Symposium Organizers
Kenji Hata Advanced Industrial Science and Technology (AIST)
Annick Loiseau Laboratoire d'Etude des Microstructures
Yoke Khin Yap Michigan Technological University
Ming Zheng National Institute of Standards and Technology
K1: <i>In-situ</i> Monitoring
Session Chairs
Hakim Amara
Annick Loiseau
Monday PM, November 30, 2009
Room 302 (Hynes)
9:00 AM - **K1.1
Growing a Carbon Nanotube Atom by Atom: ``And Yet itDoes Turn”.
Mickael Marchand 1 , Catherine Journet 1 , Dominique Guillot 1 , Jean-Michel Benoit 1 , Boris Yakobson 2 , Stephen Purcell 1
1 LPMCN, University of Lyon, Villeurbanne Cedex France, 2 ME&MS Department, Rice University, Smalley Institute, Houston, Texas, United States
Show AbstractThe key issue for realizing the potential of CNTs has always been, and still remains, a better control of CNT growth. Measurement techniques, models and control are needed at the atomic scale as this is the size of the critical growth zone. Though important progress is now being made by growing CNTs in transmission electron microscopes, this does not yet show how individual atoms integrate into a growing CNT. Ding, et al. have recently proposed that atoms may simply repetitively stick to the edges of growing single wall nanotubes (SWNTs) by a ‘screw-dislocation-like’ (SDL) mechanism. Such a mechanism is attractive because it points towards controlled growth by a sort of epitaxy, as for bulk single crystals, and connects the growth speed to helicity. However to test this theory and find the experimental conditions over which it is applicable, an experimental method that can measure growth with an atomic resolution is needed. Here we show that field emission (FE) permits such “atomic” resolution by observing the growths of individual carbon nanotubes (CNTs); from the nucleation stage, directly in a field emission microscope (FEM). As we explain below, our results lend direct support to the SDL model.Ni was first deposited on a sharp W tip in an ultrahigh vacuum FE system and formed into nano-particle catalysts by de-wetting. The CNTs were then grown by chemical vapour deposition (CVD) in 10-7 Torr acetylene at 800°C, during FEM imaging. Electrons emitted from the caps of individual, growing CNTs formed circular FEM patterns on a phosphor viewing screen. The voltage necessary for FE progressively decreased and the pattern increased in diameter which by FE principles means that a CNT grew radially from the W support tip. A more interesting type of growth was when in addition to strengthening and widening, the FE pattern rotated axially during growth. In one case the CNT rotated ~180 times during its 11 min growth cycle. This immediately suggests growth by the SDL mechanism where the integrating atoms don’t simply extrude the CNT, but force it to simultaneously rotate about the catalyst particle. More striking and in-depth information was obtained by a frame by frame analysis of the video. This showed that the rotation proceeded by discrete steps with about ~24 per rotation, half the number of atoms on the circumferences of common SWNTs. We conclude that each step is the direct observation of the SDL growth of a SWNT, one carbon dimer at a time. This work brings new insights to the three elements needed for advancing controlled CNT growth: measurement, model and control. The striking observation by FEM of the fabrication atomic brick by atomic brick of a molecular system is a new measurement technique at the atomic scale.
9:30 AM - K1.2
In Situ Synthesis of Fe Catalysts for Carbon Nanotube Growth in an Environmental Transmission Electron Microscope (ETEM).
See Wee Chee 1 , Chase Yurga-Bell 2 , Renu Sharma 1
1 LeRoy Eyring Center for Solid State Science, Arizona State University, Tempe, Arizona, United States, 2 School of Materials, Arizona State University, Tempe, Arizona, United States
Show AbstractThe transmission electron microscope (TEM) has been an important characterization tool in studying carbon nanotubes (CNT). With the development of the environmental scanning TEM (E(S)TEM), it has become possible to conduct in situ experiments to study the growth of the nanotubes at atomic resolution using the microscope column as a CVD reactor. Recently, we have successfully fabricated the Fe catalyst particles from iron organometallic precursors by electron beam induced deposition (EBID) using a Tecnai F20E(S)TEM. While these particles are catalytically active for CNT growth, the relationship between various EBID and CNT growth parameters is still not resolved.To better understand the deposition process, we used two organometallic precursors, diiron nonacarbonyl and ferrocene and studied how the morphology and composition of the deposited catalyst particles changes with the precursor pressures. Perforated Si and SiO2 membranes are used as substrates. For carbon nanotube growth, the Fe containing particles were then heated in 100 mTorr of hydrogen up to 650°C before introducing acetylene. Electron energy loss spectroscopy (EELS) data were also collected from the deposited particles before and after heating in hydrogen.We found that while flowing diiron nonacarbonyl is necessary for the catalyst deposition, it is possible to deposit particles from the adsorbed ferrocene when the precursor flow is switched off after saturating the substrate surface. Time resolved analysis of the deposited particles is then used to understand the different absorption behaviors of the two precursors. In addition, analysis of the EELS spectra shows that the particles deposited using ferrocene has higher carbon content compared to those deposited using diiron nonacarbonyl. A comparison of how the activity of the catalyst particles changes with precursor and deposition conditions will also be presented.
9:45 AM - K1.3
Origin of the Quasi-solid State of Catalyst Nanoparticles in Growing Nanostructures.
Felipe Cervantes Sodi 1 , Michael Moseler 2 3 , Stephan Hofmann 1 , Gabor Csanyi 1 , Andrea Ferrari 1
1 Engineering Department, University of Cambridge, Cambridge, Cambridgeshire, United Kingdom, 2 Department of Physics, University of Freiburg, Freiburg Germany, 3 , Fraunhofer Institute for Mechanics of Material IWM, Freiburg Germany
Show AbstractSolid nanoparticles undergo liquid-like metamorphoses, when observed in an electron microscope, or during catalytic growth of nanomaterials, such as nanotubes and nanowires. This behaviour has puzzled researchers for more than 20 years, and was termed ”quasi-solid” state [1,2]. We combine environmental electron microscopy [3,4,5] with multiscale modelling[5] to identify surface diffusion as the reason for Ni particles quasi-solidity during nanotubes growth[5]. Our simulations reveal a leap-frog motion originating from a capillarity-driven surface diffusion current. This grows a spherical head outside the tube, while shrinking an intra-tube tail. A corresponding continuum model, calibrated with atomistic diffusion, predicts a shape evolution in excellent agreement with experiments[5]. Quasi-solidity is a time, as well as size dependent property, since nanoparticles reshape in milliseconds, while micro-particles would need years.1. S. Iijima, T. Ichihashi, Phys. Rev. Lett. 56, 616 (1986).2. P. Ajayan and L. Marks, Phys. Rev. Lett. 63, 279 (1989).3. S. Hofmann et. al., Nano Lett 7, 602 (2007).4. S. Helveg et. al., Nature 427, 426 (2004).5. F. Cervantes-Sodi et al., submitted (2009).
10:00 AM - K1.4
Growth Termination of Vertically Aligned Carbon Nanotube Arrays by Dynamic Catalyst Activity.
Seung Min Kim 1 2 , Cary Pint 3 4 , Placidus Amama 5 , Dmitri Zakharov 2 , Robert Hauge 4 6 , Benji Maruyama 5 , Eric Stach 1 2
1 School of Materials Engineering, Purdue University, West Lafayette, Indiana, United States, 2 Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana, United States, 3 Department of Physics and Astronomy, Rice University, Houston, Texas, United States, 4 Richard E. Smalley Institute for Nanoscale Science and Technology, Rice University, Houston, Texas, United States, 5 Materials and Manufacturing Directorate, AFRL/RXBN, WPAFB, Ohio, United States, 6 Department of Chemistry, Rice University, Houston, Texas, United States
Show AbstractFollowing Hata’s pioneering work regarding water-assisted “supergrowth” [Hata et al., Science, 309, 2004], vertically aligned single-walled carbon nanotube (SWNT) arrays have received enormous attention, as they have a large number of potential applications. Since then, substantial research has sought the condition for “infinite” growth or “immortal” catalyst activity, but every attempt has fallen short because there is a lack of understanding of the mechanisms of growth termination. In this work, we will present a clear description of the growth termination mechanism based on dynamically evolving catalyst morphology. Since catalyst particles are located at the interface between carbon nanotube (CNT) array and substrate, we have exploited various methods to investigate the correlation between morphological evolution of catalyst particles and the growth of CNT array: thermal annealing and real CNT carpet growth combined with standard plan view and cross sectional imaging by a transmission electron microscope (TEM), in-situ CNT carpet growth monitoring by pulsed hydrocarbon source, and in-situ observation of individual CNT growth termination using an environmental-cell TEM (E-TEM). Throughout these series of investigations, we found out that the dynamic evolution of the catalyst particles, which is governed by Ostwald ripening and sub-surface diffusion, is strongly correlated with the evolution of the CNT array growth rate, and eventually the termination of growth.Based on this established correlation, we can answer two perplexing questions related to growth termination: (1) what is the role of water in “supergrowth” and (2) why does the growth temperature play so critical role in growth termination compared to other growth parameters. Approaches that may lead to “immortal catalysts” will be described.
10:15 AM - K1.5
Validation of Kinetic Model of Chemical Vapor Deposition Grown Multi-walled Carbon Nanotube via In-situ Interferrometry.
Ranadeep Bhowmick 1 2 , Brett Cruden 2 , Bruce Clemens 1
1 Materials Science and Engineering, Stanford University, Stanford, California, United States, 2 CAAMD, NASA Ames Research Center, Moffett Field, California, United States
Show AbstractDespite over a decade of chemical vapor deposition (CVD) of carbon nanotubes and inorganic nanowires, the application of validated models based on physical phenomena to explain the growth processes has been limited. Here we report the development of a general physical model for growth of 1D nanomaterials and validate the model against in-situ measurement of CVD of multi-walled nanotubes (MWNT). An interferometry setup is incorporated into a cold-wall, single-wafer CVD chamber to monitor the MWNT growth. Interference fringes and attenuation of a reflected laser beam are used to measure the heights and densities of the MWNT films, hence obtaining growth rates and catalyst yields for the CVD process. The model employed is a general kinetic model for growth of 1-D nanostructures applied to the carbon-iron system using four serial processes: thermally-induced dissociation of precursor molecules, adsorption of gas phase carbon to the catalyst particle, diffusion of carbon through the catalyst particle (both surface and bulk diffusion are considered) and partition of carbon from a carbon-iron mixture to the pure carbon form of MWNTs. The experimental results are compared against the model to identify the rate-limiting step for the growth conditions studied. Growth conditions were varied by changing temperatures, partial pressures and the absolute pressure of the precursor gases. Additionally, the increase in growth rate by introduction of an electric field to the CVD growth is examined within the context of this model.
10:30 AM - **K1.6
Exploring the Structure of Graphene and BN via Transmission Electron Microscopy.
A. Zettl 1
1 Physics, University of California-Berkeley, Berkeley, California, United States
Show AbstractA. ZettlDepartment of Physics, University of California at Berkeley, and Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley CA 94720 U.S.A.Abstract:Low dimensional sp2-bonded materials based on carbon and boron-nitride (BN) are the subject of much experimental and theoretical effort. Often, subtleties of the geometrical structure, including edge reconstructions and in-plane defects, have a profound effect on the overall electronic, thermal, optical, magnetic, and mechanical properties. I will discuss the application of ultra-high-resolution transmission electron microscopy (TEM) to graphene and planar hexagonal BN. Suspended monolayer and multi-layer foils are explored. Of particular interest is the dynamics of edge and sheet atoms, which we have recorded to produce movies of the atomic motion. In BN, it is possible to distinguish boron from nitrogen. Graphene foils can also be used as ultra-low-contrast specimen grids, whereby adsorbed chemical species can be observed; this includes the real-time observation of light-molecule dynamics.
11:00 AM - K1:in situ
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K2: Control Growth of Carbon Nanotubes
Session Chairs
Kenji Hata
Catherine Journet
Monday PM, November 30, 2009
Room 302 (Hynes)
11:30 AM - **K2.1
Structure-controlled Growth of Single-Walled Carbon Nanotubes.
Jin Zhang 1
1 College of Chemistry and Molecular Engineering, Peking University, Beijing China
Show AbstractSince the discovery of single-walled carbon nanotube (SWNTs) in 1993, many efforts have been made to investigate the structure controlled growth for meeting the existing expectations in nanoelectronics. Although various attempts have been made, it still remains a lot of challenges. This talk will cover the following topics: 1)Temperature Mediated CVD Growth of SWNTs with Controlled Diameter: This was achieved by a consistent variation of SWNT diameter and chirality with the change of growth temperature even though catalyst particles remained the same. These findings provide a potential approach to grow SWNT intramolecular junctions at desired locations, sizes and orientations, which are important for making SWNT electronic circuits. 2)‘Cloning’ of SWNTs via Open-End Growth Mechanism: By using open-end SWNTs as ‘seeds/catalysts’ (without metal catalysts), duplicate SWNTs could be grown and cloned from the parent segments via an open-end growth mechanism. These findings provide a potential approach for growing SWNTs with controlled chirality. 3)Crankling Individual Ultralong SWNT into Serpentines. Crankling ultralong SWNTs into serpentine tubes on quartz surface were realized by controlling its landing process. The yield percentage of serpentines SWNTs exceeds 96% with the amplitudes and the density over 100 μm and 2 SWNTs/μm, respectively. The serpentine SWNTs are accessible to be introduced into ultrahigh-current SWNT-based devices simultaneously with high on/off ratio. These findings flatten an approach to desirable devices built from single-chirality SWNT arrays on surface. References:1.J Zhang et. al., Temperature-mediated growth of single-walled carbon-nanotube intramolecular junctions, Nature. Mater., 6(4)(2007), 283.2.J Zhang et. al., 'Cloning' of single-walled carbon nanotubes via open-end growth mechanism, Nano Lett., 9(2009),16733.J Zhang et. al., Crankling Ultralong Carbon Nanotubes into Serpentines via Landing-Controlled Process, Adv. Mater., 2009, In press.4.J Zhang et. al., Grow single-walled carbon nanotubes cross-bar in one batch, J. Phys. Chem. C, 113(14)(2009)5341. (cover paper).
12:00 PM - K2.2
Density Enhancement of Aligned Single-walled Carbon Nanotube Thin Films on Quartz Substrates by Sulfur Assisted Synthesis.
Thomas McNicholas 1 , Lei Ding 1 , Dongning Yuan 1 , Jie Liu 1
1 Chemistry, Duke University, Durham, North Carolina, United States
Show AbstractThe density of the aligned Single-Walled Carbon Nanotubes (SWNTs) grown on quartz substrates is an important factor for the performance of fabricated electronic devices. It was discovered that the addition of a Sulfur containing compound (thiophene) to the reaction mixture improved the density of SWNTs by a factor of 2 or more, from ~ 2-3 SWNT/μm to 6-8 SWNTs/μm under similar growth conditions. It was also observed that along with the increase in nanotube density, the cleanness of the samples improved as well. These effects were demonstrated over a large range of growth conditions, indicating that the addition Sulfur makes the growth processes more favorable for the nucleation and growth of aligned SWNTs.
12:15 PM - K2.3
Direct Growth of Bent Carbon Nanotubes on Surface Engineered Sapphire.
Hiroki Ago 1 2 3 , Kenta Imamoto 2 , Tetsushi Nishi 2 , Masaharu Tsuji 1 2 , Tatsuya Ikuta 4 , Koji Takahashi 4 , Munetoshi Fukui 5
1 Inst. Mater. Chem. Eng., Kyushu University, Fukuoka Japan, 2 Grad. Schl. Eng. Sci., Kyushu University, Fukuoka Japan, 3 , PRESTO-JST, Kawasaki Japan, 4 Grad. Schl. Eng., Kyushu University, Fukuoka Japan, 5 , Hitachi High-Tech., Ibaraki Japan
Show AbstractRealizing hierarchical network of single-walled carbon nanotubes (SWNTs) is important for future electronic applications. The horizontally-aligned growth has been achieved on single-crystalline substrates, such as sapphire (Al2O3) [1,2] and quartz (SiO2) [3], but bending or changing the growth direction of SWNTs during their growth is expected for further control of structure. Although SWNT serpentine was previously reported, the bending position was difficult to control [4]. Here, we demonstrate the bending of horizontally-aligned SWNT on surface engineered single-crystal sapphire. The SWNTs grown on r-plane sapphire were aligned along the specific crystallographic [1 -1 0 -1] direction due to the lattice-oriented growth, and we created artificial step structures perpendicular to this SWNT growth direction. These steps changed the nanotube growth direction from the [1 -1 0 -1] to the step direction with the bending angle of nearly 90 degrees [5]. Effects of the bending structure on electron transport property were studied, and we found that the bending segment show higher resistivity compared with the straight segment. Our approach to combine the lattice-oriented growth with the step-templated growth will offer a new route towards a controlled growth of a two-dimensional SWNT architecture for future nanoelectronics.Lastly, our new finding of the orthogonal growth of SWNTs based on two different surface atomic arrangements on one sapphire substrate is also presented.References[1] H. Ago et al., Chem. Phys. Lett., 408, 433 (2005). [2] S. Han et al., J. Am. Chem. Soc., 127, 5294 (2005). [3] C. Kocabas et al., Small, 1, 1110 (2005). [4] N. Gelblinger et al., Nat. Nanotech,. 3, 195 (2008). [5] H. Ago et al., J. Phys. Chem. C, in press.
12:30 PM - K2.4
Compositional Tuning of NiFe Bimetallic Nanocatalysts for Selective Growth of Single-walled Carbon Nanotubes (SWCNTs) and Fabrication of SWCNT-based Field-effect Transistors.
Wei-Hung Chiang 1 , Mohammed Sakr 2 3 , Xuan P.A. Gao 2 , R. Mohan Sankaran 1
1 Chemical Engineering, Case Western Reserve University, Cleveland, Ohio, United States, 2 Physics, Case Western Reserve University, Cleveland, Ohio, United States, 3 Physics, Alexandria University, Alexandria Egypt
Show Abstract Single-walled carbon nanotubes (SWCNTs) have exceptional optical, electronic, and mechanical properties that are largely determined by their diameter and chiral angle, specified as chiral indices (n,m). Although significant research efforts have been directed towards post-growth separation and purification of individual nanotube structures, the selective growth of SWCNTs in the gas phase remains the most promising approach for non-destructive, scalable, and economical production. Here, we present a novel investigation of the effect of nanocatalyst composition on the growth and chirality distribution of as-grown SWCNTS, independent of particle size. We have recently developed a two-step process for gas-phase SWCNT growth [1-3]. In the first step, vapor-phase precursors such as nickelocene or ferrocene are introduced into an atmospheric-pressure microplasma and decomposed non-thermally by electron impact to nucleate and grow dimensionally- and compositionally-controlled nanoparticles. The particles are then continuously injected into a flow furnace with acetylene (C2H2) and hydrogen (H2) gases to catalyze SWCNT growth. Optical characterization of the SWCNT product by UV-Vis-NIR absorbance spectroscopy, photoluminescence (PL) spectroscopy, and micro Raman spectroscopy shows that the chirality distribution of as-grown SWCNTs is significantly influenced by the composition of the nanocatalysts. While monometallic Ni nanocatalysts yield a broad distribution of SWCNT structures, including a mixture of metallic and semiconducting tubes, bimetallic Ni0.27Fe0.73 nanocatalysts produce a narrow chirality distribution with mostly semiconducting tubes. The electrical properties of the SWCNTs were tested by fabricating bottom-gated thin film field-effect transistors (FETs) and confirm that samples grown with Ni0.27Fe0.73 nanocatalysts contain a higher fraction of semiconducting nanotubes. 1.W-H. Chiang and R. M. Sankaran, “Microplasma synthesis of metal nanoparticles for gas-phase studies of catalyzed carbon nanotube growth,” Appl. Phys. Lett., Vol. 91, 121503 (2007).2.W-H. Chiang and R. M. Sankaran, “Synergistic effects in bimetallic nanoparticles for low temperature carbon nanotube growth,” Adv. Mater., Vol. 20, 4857 (2008).3.W-H. Chiang and R. M. Sankaran, “In-flight dimensional tuning of metal nanoparticles by microplasma synthesis for selective production of diameter-controlled carbon nanotubes,” J. Phys. Chem. C, Vol. 112, 17920 (2008).
12:45 PM - K2.5
Mechanistic Investigations of Single-walled Carbon Nanotube Synthesis by Ferrocene Vapor Decomposition in Carbon Monoxide.
Anton Anisimov 1 , Albert Nasibulin 1 , Hua Jiang 1 , Pascale Launois 2 , Julien Cambedouzou 2 , Sergey Shandakov 1 3 , Esko Kauppinen 1 4
1 Department of Applied Physics, Helsinki University of Technology, Espoo Finland, 2 Laboratoire de Physique des Solides, Universite Paris-Sud, Orsay France, 3 Department of Physics, Kemerovo State University, Kemerovo Russian Federation, 4 , VTT Biotechnology, Espoo Finland
Show AbstractThe single-walled carbon nanotubes (SWCNTs) were synthesized by the carbon monoxide disproportionation reaction on Fe catalyst particles formed by ferrocene vapor decomposition in a laminar flow aerosol (floating catalyst) reactor. On the basis of in situ sampling of the product collected at different locations in the reactor, kinetics of the SWCNT growth and catalyst particle crystallinity were studied. Catalyst particles captured before SWCNT nucleation as well as inactive particles were determined to have cementite (Fe3C) phase, while particles with γ- and α-Fe phases were found to be embedded in the SCWNTs. The growth rate in the temperature range from 804 to 915 oC was respectively varied from 0.67 to 2.7 µm/s. The growth rate constant can be described by an Arrhenius dependence ofk=k0exp(-Ea/kT) with an activation energy ofEa=1.39 eV, which was attributed to the carbon diffusion in solid iron particles. CNT growth termination was explained by solid-liquid phase transition in the catalyst particles. A high temperature gradient during the SWCNT growth was found to not have any effect on the diameter and as a result on the chirality of the growing SWCNTs. The mechanism of SWCNT nucleation and growth was proposed.
K3: Theory of Carbon Nanostructures
Session Chairs
Monday PM, November 30, 2009
Room 302 (Hynes)
2:30 PM - **K3.1
Creating, Removing and Detecting Defects in Nanocarbons.
David Tomanek 1
1 Physics and Astronomy Department, Michigan State University, East Lansing, Michigan, United States
Show AbstractDefects in carbon nanotubes, including atomic vacancies andStone-Wales defects, are known to significantly degrade thestability, electrical and thermal conductance of these uniquenanostructures. Location of defects can be detectedspectroscopically [1] or by probing the topography or localdamping in dynamic Atomic Force Microscopy [2]. Carbon nanotubesexhibit an unusual capability for healing by reconstruction atdefect sites, induced thermally or by monochromatic light [3,4].On the other hand, presence of structural defects may be adesirable pre-requisite to induce large-scale structural changes,including fusion of nanotubes [5] and nanotube peapods [6].
Since direct observation of atomic-scale processes associated withself-healing at defect sites or defect-assisted structural changesis very hard by experimental means, computer simulations offerunique insight into the underlying Physics.
[1] Yoshiyuki Miyamoto, Angel Rubio, Savas Berber, Mina Yoon,David Tomanek, Spectroscopic characterization of Stone-WalesDefects in Nanotubes, Phys. Rev. BR 69, 121413 (2004).
[2] Makoto Ashino, Roland Wiesendanger, Andrei N. Khlobystov,Savas Berber, and David Tomanek, Revealing Sub-Surface VibrationalModes by Atom-Resolved Damping Force Spectroscopy, Phys. Rev.Lett. 102 (2009).
[3] Yoshiyuki Miyamoto, Savas Berber, Mina Yoon, Angel Rubio, andDavid Tomanek, Onset of nanotube decay under extreme thermal andelectronic excitations, Physica B 323, 78 (2002).
[4] Yoshiyuki Miyamoto, Savas Berber, Mina Yoon, Angel Rubio,David Tomanek, Can Photo Excitations Heal Defects in CarbonNanotubes? Chem. Phys. Lett. 392, 209 (2004).
[5] Mina Yoon, Seungwu Han, Gunn Kim, Sangbong Lee, Savas Berber,Eiji Osawa, Jisoon Ihm, Mauricio Terrones, Florian Banhart,Jean-Christophe Charlier, Nicole Grobert, Humberto Terrones,Pulickel M. Ajayan, David Tomanek, The zipper mechanism ofnanotube fusion: Theory and Experiment, Phys. Rev. Lett. 92,075504 (2004).
[6] Savas Berber, Young-Kyun Kwon, and David Tomanek, MicroscopicFormation Mechanism of Nanotube Peapods, Phys. Rev. Lett. 88,185502 (2002).
3:00 PM - K3.2
An Approach For The Healing Of Defective Carbon Structures:A Tight-Binding Monte Carlo Study.
Hakim Amara 1 , Sondes Karoui 1 , Bichara Christophe 2 , Ducastelle Francois 1
1 , ONERA-CNRS, Chatillon France, 2 , CINaM CNRS, Marseille France
Show AbstractCarbon nanotubes and graphene are promising materials of remarkable mechanical and electronic properties that should give rise in the near future to revolutionary technologies. As of today, the mechanisms of germination and growth of the nano-objects are still very much misunderstood. Likewise, the selective and controlled growth of carbon nanotubes is currently unachievable. Graphitic structures can be synthesized at medium temperatures (1000 K) by chemical vapor deposition from a metal catalyzing particle. The most prevailing problem with these synthesized structures is the presence of a high concentration of defects that hinders large scale manufacturing.In the context of this work, we wish to determine how to effectively control the geometries of graphitic structures grown from catalytic decomposition on transition metals. We have at our disposal a theoretical model that enables us to investigate the atomistic processes involved in the nucleation of these structures as well as the subsequent phases. Based on the (tight binding) approximation, it constitutes a semi-empirical energetics model implemented into a Monte-Carlo code.
3:15 PM - K3.3
Towards Real-Time Control of Conduction Switching of Carbon Nanotubes: A First-Principles Investigation.
Elise Li 1 , Nicolas Poilvert 2 , Nicola Marzari 2
1 Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractFunctionalization of SWNT through cycloaddition reactions represents an effective method to engineer or manipulate carbon nanotubes. For armchair CNTs, the electronic property can be transformed drastically from metallic to semiconducting by the introduction of functional groups which disrupt the conjugated π network. Unlike common monovalent substituents such as hydrogens or aryl groups, [1+2] cycloadditions of carbenes or nitrenes can preserve CNT metallicity to a high extent. The strain energy caused by the cyclopropane moiety formed between the divalent functional group and CNT often induce a sidewall bond breakage, thus recovering the sp2 environment and high electronic transport. In real systems, whether this bond cleavage happens depends heavily on the chirality and curvature of the tube, and the chemical nature of the addends. Here we explore the underlying mechanism of bond-cleavage chemistry in [1+2] cycloadditions on armchair carbon nanotubes using first-principles calculations. We find the high strain energy in cyclopropane moiety can be compensated by a through space π orbital interaction between the addend and the CNT which lowers the HOMO energy significantly in closed-bond configuration. A bond opening or closing switch marked by large conductance change can therefore be devised by modulating the proximity of the addend π system and the tube surface via optical or electrochemical control. This could allow for real-time on/off control of theconductance, which potentially has extensive applications in nanoscale devices.
3:30 PM - K3: CTheory
BREAK
K4: Spectroscopy of Carbon Nanostructures
Session Chairs
Monday PM, November 30, 2009
Room 302 (Hynes)
4:00 PM - **K4.1
Wavefunctions and Many-body Effects in Carbon Nanotubes Measured by STM.
Jerome Lagoute 1 , Hong Lin 2 1 , Vincent Repain 1 , Cyril Chacon 1 , Yann Girard 1 , Francois Ducastelle 2 , Annick Loiseau 2 , Sylvie Rousset 1
1 Laboratoire Matériaux et Phénomènes quantiques, Université Paris Diderot-CNRS, Paris France, 2 Laboratoire d'étude des microstructures, ONERA-CNRS, Châtillon France
Show AbstractCarbon nanotubes (CNTs) have emerged as promising candidates for molecular electronics in particular because their metallic or semiconducting character can be tuned through a structural control. It is therefore crucial to understand their electronic properties down to the atomic scale. Scanning tunnelling microscopy (STM) and spectroscopy (STS) is a powerful tool for the local investigation of the link between atomic structure and local electronic density of states. The spectroscopy which is dominated by a series of Van Hove singularities (VHS) has been successfully described in the scheme of the tight binding theory although many-body effects play an important role in the band structure of CNTs.We addressed the question of the origin of energy position of VHS and the role of many-body effects in STS measurements. In a typical STM experiment, the nanotubes are supported by a metallic substrate which reduces the many-body interactions by the screening effect. Measuring the local spectroscopy on bundles of single-walled carbon nanotubes we have access to strong or soft tube-metal interaction. Therefore, the analysis of STS measurements provide informations on the many-body interactions in SWNTs. To get deeper insight in the underlying physics of this system, we compared STS results with the optical absorption spectrum which, in contrast to STS measurements, is sensitive to the excitons. These data allow an estimate of the exciton binding energy deduced from local measurements.The local electronic properties of carbon nanotubes can be investigated further by imaging their electronic density of states at different energies. In this way we are able to measure electron wavefunctions of SWNTs. These measurements will be discussed in detail. The results obtained are in line with the predictions of a simple tight binding model. This accordance indicates that, despite the influence of the substrate, STS allows to measure the intrinsic wavefunctions of nanotubes.
4:30 PM - **K4.2
Optical Spectroscopy of Freely Suspended Graphene Monolayers and Individual Carbon Nanotubes.
Stephane Berciaud 1
1 Department of Chemistry and Department of Physics, Columbia University, New York, New York, United States
Show AbstractOwing to their outstanding fundamental properties, graphene layers and carbon nanotubes areamong the most promising building blocks for carbon-based electronic and opto-electronic devices. Sinceboth materials consist entirely of surface atoms, they are strongly perturbed by the environment.Therefore, non-contact studies on free-standing samples are particularly praised.The first part of this talk will be dedicated to the opto-electronic properties of graphene. We willshow that Raman scattering spectroscopy is a simple, but extremely sensitive non-contact approach thatprovides a wealth of quantitative information (number of layers, doping level, influence of disorder,temperature, mechanical stress,…) about this two-dimensional material system. This techniquecomplements electronic transport measurements, which require several processing steps and contactedsamples. We performed a spatially resolved micro-Raman study on pristine graphene layers that weresuspended in air over micrometer-sized trenches. In these conditions, we have demonstrated that freestandinggraphene monolayers are essentially undoped, with an upper bound of 2\times10^{11}cm^{-2}for the residual carrier concentration [1]. Without the deleterious perturbations induced by a solidsubstrate (charge inhomogeneity and enhanced carrier scattering), such free-standing samples allowedus to probe the intrinsic electronic and vibrational properties of graphene monolayers. We will focus onthe peculiar properties of the one phonon G- and 2-phonon 2D- Raman modes under ideal conditions,and discuss their evolution in electrostatically gated and electrically contacted suspended samples.In the second part, we will review recent experiments performed on free-standing carbonnanotubes. These quasi-one-dimensional systems can be seen as rolled up graphene sheets. In additionto several properties that derive directly from graphene, quantum confinement and enhanced Coulombinteractions give rise to strong excitonic transitions that can be probed optically at the single nanotubelevel [2]. Using a combination of Rayleigh and Raman scattering measurements, we were able todetermine the chiral indices (n,m) of a collection of isolated free-standing nanotubes and to examine thespectra of their unperturbed electronic transitions in detail. We will focus on the influence of the chiralindices on electron-phonon and exciton-phonon coupling, both in semi-conducting and metallic species.References[1] S. Berciaud, S. Ryu, L. E. Brus, T. F. Heinz., Nano Letters 9, 346 (2009)[2] M. Sfeir et al. Science 312 554 (2006)
5:00 PM - K4.3
Exciton-Exciton Annihiation Dynamics in (6,5) Single-walled Carbon Nanotubes.
Shujing Wang 1 , Marat Khafizov 1 , Ming Zheng 2 , Todd Krauss 1
1 , University of Rochester, Rochester, New York, United States, 2 , Pont Central Research, Wilmington, Delaware, United States
Show AbstractSingle-walled carbon nanotubes (SWNTs) have recently emerged as a novel 1D material with exceptional optical and electronic properties. In particular, photoexcitation of SWNTs results in a strongly bound electron-hole pair (i.e. exciton) with electronic resonances dependent on the SWNT diameter and energies in the technologically important near-infrared region of the electromagnetic spectrum. Understanding the different relaxation pathways for these excitons is of fundamental interest and especially important since these pathways play a crucial role in developing potential applications for optoelectronic devices. We will present studies of ultrafast exciton excited state dynamics in single chirality enriched (6,5) SWNTs using transient absorption spectroscopy. The decay of the differential transmission signal on the ~1 nsec timescale is nonexponential, and is best fit by a power-law, indicating long-time population relaxation is controlled by one-dimensional diffusion limited processes. However, focusing on the first 20 ps of relaxation, the dynamics can be well described by a triexponential function with three distinct decay components determined from a global fitting procedure: τ3 ~ 0.6ps, τ2 ~ 2 ps, and τ1 ~ 30ps. These decay time constants were found to be similar when the SWNTs were excited at different wavelengths including 335, 400, 670, and 800 nm. While the longer and middle decay times are independent of pump intensity, the subpicosecond decay component is strongly pump dependent, with a relative contribution that becomes significantly more pronounced with increasing fluence. The pump fluence dependence of the short-time contribution strongly suggests that these respective dynamics comes from exciton-exciton annihilation processes. On the other hand, the ~2 ps and ~30 ps decay components are related to single exciton recombination since they both persist unchanged down to extremely low pump fluence where the average number of excitons per NT is < 0.2. The underlying physical processes responsible for the dynamics at all timescales will be discussed.
5:15 PM - K4.4
Polarization-dependent Raman Spectra of Graphene Nanoribbons.
Andrea Fasoli 1 , Antonio Lombardo 1 , Tero Kulmala 1 , Alan Colli 2 , Andrea Ferrari 1
1 , Cambridge University, Cambridge United Kingdom, 2 , Nokia Research Centre c/o Nanoscience Centre, Cambridge United Kingdom
Show AbstractShaping a graphene flake into a nanoribbon is a preferred way to induce a band gap opening [1]. Graphene nanoribbons (GNRs) are thus envisaged to be used as building blocks of room temperature, fast switching, high mobility transistors [1,2]. The GNR electronic properties are strongly related to the quality of its crystallographic structure, in particular to the edges morphology [2]. Raman spectroscopy is an ideal tool to investigate the structural properties of carbon-based nanomaterials, graphene in particular [3].Here, we present polarization-dependent Raman measurements on GNRs fabricated via Nanowire Lithography (NWL). We use silicon nanowires (SiNWs) transferred on mechanically cleaved graphene flakes to fabricate GNRs sandwiched between the SiO2 substrate and the masking SiNWs. Raman measurements show a dependence on incident light polarization of the intensity of all detected peaks, this being maximum along the ribbon axis [4]. 1. Han, M. Y. ; et al. Phys. Rev. Lett. 98, 206805 (2007)2. Ouyang Y.; et al. Appl. Phys. Lett. 92, 243124 (2008)3. Ferrari A.C.; et al. Phys. Rev. Lett. 97, 187401 (2006)4. Fasoli A.; et al. submitted (2009)
5:30 PM - **K4.5
Substitutionally-Functionalized vs Metallicity-Selected Single-Walled Carbon Nanotubes: A High Energy Spectroscopy Viewpoint.
Paola Ayala 1 , Yasumitsu Miyata 2 , Christian Kramberger 1 , Hiromichi Kataura 3 , Thomas Pichler 1
1 Fakultät für Physik, University of Vienna, Vienna Austria, 2 , University of Nagoya, Nagoya Japan, 3 , AIST, Tsukuba Japan
Show AbstractThe unique one-dimensional electronic and optical properties attributed to single-walled carbon nanotubes (SWCNTs) are mainly related to the peculiar local arrangement of sp2 hybridised carbon atoms. This atomic distribution determines the feasibility to have different semiconducting and metallic tubular structures, which nowadays are still produced in mixtures of both species with the state-of-the-art manufacturing techniques. For this reason, the possibility to modify the SWCNTs properties in a controlled manner is particularly appealing. In this framework, modified structures can be envisaged based on collective and single effects. The first case embraces the inevitable interactions of nanotubes in a bundle or via different doping routes. The second case is related to single doping defects, which locally modify the energies of charge carriers and lattice vibrations.In this presentation we first review how the properties of these structures are usually determined by their interaction in a nanotube solid. High energy spectroscopy, as well as optical and Raman spectroscopy have been shown to be very effective key tools to analyse the details in modifications of the underlying basic correlation effects in the bonding environment, the charge transfer between functionalized nanotubes, and the doping in nanotubes. These studies provide a solid basis for a detailed insight into the influence of doping, chemical interactions on the electronic ground state and the transport properties of SWCNTs. The particular case of B-doped SWCNTs will be shown in detail. Our recent progress on bulk properties of metallicity-separated SWCNTs (pristine and intercalated) using photoemission and x-ray absorption spectroscopy is also presented. Here, the changes in the site selective valence and the conduction-band electronic structure in metallicity-selected nanotubes are analyzed.
K5: Poster Session: Synthesis of Nanotubes and Relatd Nanostructures
Session Chairs
Kenji Hata
Annick Loiseau
Tuesday AM, December 01, 2009
Exhibit Hall D (Hynes)
9:00 PM - K5.1
Tuning Ultra Long Multi-walled Carbon Nanotubes with Desirable Structures through Growth Kinetics Investigation.
Xinwei Cui 1 , Weifeng Wei 2 , Weixing Chen 1
1 Chemical & Materials Engineering Department, University of Alberta, Edmonton, Alberta, Canada, 2 Department of Chemical and Materials Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractThe unique properties of carbon nanotubes (CNTs) strongly depend on their structures. In this study, we have succeed in synthesizing multi-walled carbon nanotube (MWCNT) arrays with desirable MWCNT structures, such as high purity, selective height and CNT wall number, by water-assisted chemical vapor deposition (WA-CVD). It was found that the kinetics of MWCNT arrays in WA-CVD demonstrated a lengthening and thickening growth. In the lengthening stage, the array height increases linearly with growth time and CNT wall number doesn’t change; while in the thickening stage, CNT wall number increases substantially with time and catalysts become deactivated following the radioactive decay model. By choosing the partial pressure of water vapor and/or ethylene gas in the reaction environment, different linear lengthening stages corresponding to different CNT wall numbers could be obtained. Based on the kinetics in the linear lengthening stage, high purity MWCNT arrays with desirable height and/or CNT wall number have been fabricated.
9:00 PM - K5.10
Double-walled Carbon Nanotubes from Ethanol Decomposed on Bimetallic Fe-Mo Nanocatalysts Supported on γ-Al2O3.
Zhenyu Liu 1 , Kelsey Finega 1 , Judith C. Yang 1
1 Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
Show AbstractHigh quality double-walled carbon nanotubes (DWNTs) are synthesized by catalytic decomposition of ethanol at 900oC on Fe-Mo/Al2O3 catalyst. The different concentration of catalyst play an important role on the yield of DWNTs growth. The evolution of the catalyst size and phase states of mono-Fe and bi-Fe/Mo catalysts before and after carbon DWNTs growth have been studied using transmission electron microscopy (TEM) and x-ray diffraction (XRD) measurements. The addition of molybdenum to Fe lowers the growth temperature of DWNTs. Carbon induced solid-liquid and solid–liquid-solid phase transitions of the nanocatalyst during the CNT synthesis were observed. We found that the liquid phase is favored for the growth of nanotubes, while solidification due to the formation of stable iron carbides along with the poisoning of the catalyst surface by amorphous carbon nearly terminates the CNT growth. No growth of DWNTs was observed below the eutectic point where the catalyst is in its solid phase. However, the presence of Mo decreases the eutectic point of the catalyst and prevents the formation of stable carbides, thereby increasing the yield and quality of the DWNTs. Our results support a growth mechanism of DWNTs from liquefied catalyst particles. The re-growth behavior of the regenerated catalysts by oxidation was investigated also by high resolution TEM and Raman; it was found that the diameter of the resulting carbon nanotubes may be tuned by the multi-cycled reduction and oxidation (redox).
9:00 PM - K5.12
Non-Catalytic Flame Synthesis of Carbon Nanostructures.
Cassandra D'Esposito 1 , Jafar Al-Sharab 2 , Bernard Kear 2 , Stephen Tse 1
1 Mechanical and Aerospace Engineering, Rutgers University, Piscataway, New Jersey, United States, 2 Materials Science and Engineering, Rutgers University, Piscataway, New Jersey, United States
Show AbstractCarbon nanostructures are one of the most commonly mentioned building blocks of nanotechnology due to their amazing mechanical, electrical, thermal, and optical properties. Carbon nanotubes (CNTs) are generally produced by three main techniques: arc discharge, laser ablation, and CVD. Although these methods have met with some success, large-scale applications will require synthetic methods that are continuous and energy efficient and that do not require expensive starting materials. Combustion synthesis has demonstrated a history of scalability and offers the potential for high-volume commercial production, at reduced costs. We utilize flame-based synthesis, which, due to the characteristic high temperatures, allows for the formation of carbon nanotubes without the use of catalysts. Specifically, various carbon nanostructures, such as carbon nanotubes, nano-onions, and graphene layers, are produced from counterflow diffusion flames, which permit correlation of morphologies with local conditions due to the quasi-one-dimensionality of the flow field. The synthesis is carried out at one atmosphere pressure. To assess the growth mechanisms, spontaneous Raman scattering is used to determine the temperature profile and to map CO, C2H2, CH4, H2, and O2 gas-phase species. Laser induced fluorescence is used to map OH and C2 gas-phase distributions.
9:00 PM - K5.13
Control over Wall-Number of Carbon Nanotubes via Block Copolymer Lithography.
Duck Hyun Lee 1 , Won Jong Lee 1 , Sang Ouk Kim 1
1 Department of Materials Science and Engineering, KAIST, Daejeon Korea (the Republic of)
Show AbstractThe wall-number-selective growth of vertical carbon nanotube (CNT) arrays is achieved by combining plasma enhanced chemical vapor deposition (PECVD) and block copolymer lithography. Block copolymer lithography is an attractive nanopatterning method for generating a uniform catalyst particle array for carbon nanotube growth. However, the scale of the catalyst particles patterned by block copolymer lithography is usually tens of nanometers, which is too large for wall-number-selective growth of CNTs. In this work, various methods for sub-nanometer-scale tunability of catalyst size have been investigated to enable excellent controllability of the wall-number and diameter of the CNTs. In this work, highly uniform nanopatterned iron catalyst arrays were prepared by tilted evaporation through block copolymer nanotemplates, and the sub-nanometer-scale tunability of catalyst particles enabled the excellent controllability of the wall-number and density of the CNT arrays. Moreover, the use of ammonia in the growth of CNT arrays ensured that the CNTs were nitrogen doped, and the doping concentration of nitrogen can be adjusted by controlling the flow rate of ammonia gas. Substitution of a carbon in a CNT wall with a more electron-rich nitrogen atom provided additional electrons and enhanced the conductivity of the nanotubes. Since the overall process throughout nanotemplate assembly, catalyst deposition and CNT growth constitutes parallel processing, our approach is readily scalable to a mass-production.
9:00 PM - K5.14
Dynamic Deposition Mechanism for the Growth of Carbon Nanotube Films.
Sangil Hyun 2 , Seung-Hun Huh 1 , Lan-Hee Yang 3 , Byeong-Deok Yu 4
2 Nanotech Convergence Team, KICET, Seoul Korea (the Republic of), 1 Nanotech Convergence Team, KICET, Seoul Korea (the Republic of), 3 Physics Department, University of Seoul, Seoul Korea (the Republic of), 4 Physics Department, University of Seoul, Seoul Korea (the Republic of)
Show AbstractParticle collisions are common phenomena observed in chemical/physical reaction processes. Artificial atomic/molecular-level deposition is a practical form of collision utilized in thin-film fabrication method such as sputtering accompanied by surface nucleation and grain growth, as defined by Grovenor and Thornton-Zone diagrams. Cluster collisions are known to form dense films with high impact velocity. While nanoparticle collisions cannot drive grain growth, because of nanoparticle state stability and relatively low impact energy, products of such collisions have properties of both a film and an intrinsic nanoparticle, based on collision-induced direct bond formation. Our study is to address that the collisions of carbon nanotubes (CNTs) could yield granular CNT films without catalysts and binders. Chemical vapour deposition, electrical/chemical forced adsorption, and printing with polymer binders are widely used for CNT film fabrication. These methods however usually have shortcomings on the intrinsic CNT properties and compatibility of the film with semiconducting processes due to the possible contaminations and physical/chemical/thermal instability. In this talk, we suggest a new approach of realizing CNT films with biaxial structural properties—lateral bound CNT bodies and vertical protuberances of CNT terminals—using physical impact deposition (PID). It is a quite reliable method to achieve stable bonding between the CNT and Si substrates.To examine the morphology and kinematics of the film formation process, we performed numerical simulations using classical molecular dynamics and the first principle method. The origin of the bonding state being observed after the plastic deformation of the substrate is totally different from the weak van der Waals interaction. Based on the bonding strength between carbon and silicon atoms, we suggest that some chemical bonding can be formed by the dynamic deposition of CNTs on the substrate.
9:00 PM - K5.16
Influence of Hydrogen on Growth of Carbon Nanotubes.
Andrey Knizhnik 1 , Irina Lebedeva 1 , Alexey Gavrikov 1 , Alexey Baranov 1 , Maksim Belov 1 , Boris Potapkin 1 , Timothy Sommerer 2 , Christopher Eastman 2
1 , Kintech Lab Ltd, Moscow Russian Federation, 2 , GE Global Research Center, Niskayuna, New York, United States
Show AbstractDepending on the purpose which carbon nanotubes (CNTs) are grown for, the structure of the nanotubes should meet different requirements. According to the experimental data, the hydrogen partial pressure affects the structure of CNTs grown by chemical vapor deposition. We analyzed interaction of carbon species with hydrogen in the gas phase and on the catalyst surface. By density functional theory calculations, we obtained kinetic parameters for dissociation of hydrocarbons on the Ni (111) and Ni (113) surfaces and showed that under typical conditions for the growth of CNTs hydrogen can considerably influence the equilibrium in such a system. Hydrogenation of small carbon species should lead to a decrease in the rate of their adsorption and an increase in the rate of desorption and, consequently, a decrease of an effective carbon flux onto the catalyst surface. We also demonstrated that hydrogen effectively binds to edges of graphitic structures on the Ni (111) surface. Kinetic parameters for attachment of carbon adatoms to graphitic structures were calculated for different configurations with and without hydrogen in the system. These calculations revealed that hydrogen should reduce the rate of carbon incorporation into graphitic structures. To correctly reproduce the effect of hydrogen, a kinetic model of growth of CNTs was developed. The model was used to estimate the growth rate of carbon nanotubes and to determine critical gas pressures, at which CNT growth switches from the adsorption limitation to the limitation by reaction and diffusion on the catalyst. The results obtained using the kinetic model of growth of CNTs are in good agreement with experimental data.
9:00 PM - K5.17
Morphology, Dynamics, and Sudden Termination of Vertically Aligned Carbon Nanotube Forest Growth.
Phillip Vinten 2 1 , Paul Marshall 1 , Jeffery Bond 2 1 , Jacques Lefebvre 1 , Paul Finnie 1 2
2 Department of Physics, University of Ottawa, Ottawa, Ontario, Canada, 1 Institute for Microstructural Sciences, National Research Council Canada, Ottawa, Ontario, Canada
Show AbstractThe termination of, versus the continued growth of, vertically aligned carbon nanotube forests grown by chemical vapor deposition (CVD) is an increasingly important topic. In situ methods are a promising approach for these studies. Here, millimeter scale forests are synthesized by water-assisted acetylene CVD and ethanol CVD on patterned silicon:silicon dioxide samples with patterned thin film alumina:cobalt catalyst islands. We use real-time in situ optical microscopy to observe growing forests and changes in their morphology as they grow. Ex situ scanning electron microscopy and Raman spectroscopy are used to further characterize the structure of the forests and observe their finer details. From in situ observations, we extract detailed dynamics (e.g. final heights, initial growth rates, termination rates) and their associated activation energies. We compare the activation energies for ethanol and acetylene CVD, showing that energetic parameters are specific to the carbon source. In contrast, Raman spectroscopy reveals that other parameters, (e.g. D to G ratio and radial breathing mode density) scale almost identically for both ethanol and acetylene. We do see the sudden termination phenomena reported by other groups; however, our experiments further reveal that not all forests terminate the same way, but rather that they are dependent on the specific process parameters. Furthermore, while stable growth may be the more normal situation, transitions from stable, continuous growth to unstable growth can occur.
9:00 PM - K5.18
Size-induced Enhanced Diffusion in Melting Iron Nanoparticles.
Felipe Cervantes Sodi 1 , Gabor Csanyi 1 , Andre Ferrari 1 , Stefano Curtarolo 2
1 Engineering Department, University of Cambridge, Cambridge, Cambridgeshire, United Kingdom, 2 Department of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina, United States
Show AbstractDuring chemical vapor deposition growth of carbon nanotubes the kinetic and thermodynamic aspects of the catalytic particle play a fundamental role in the nucleation and growth process. Here we investigate the thermodynamic state of iron nanoparticles via molecular dynamics at temperatures close to the size corrected melting point [1]. The size-dependent solid to liquid transformation is described with a combination of bond-length order parameters, caloric curves, and self-diffusion coefficients. We find that the diffusion coefficient is enhanced in small particles and can be used to describe the viscous condition across the transformation. The implications in CNT growth are that at constant temperature, the smaller clusters are capable of a more rapid reorganization upon application of external pressure and enhanced diffusion could allow more rapid transformation of the feedstock [1]. However, if the size of the catalysts becomes too small, their “excess surface-tension free-energy” dominates over bulk and surface free-energies, causing reduced solubility [2] or coarsening [3], both detriments for catalytic activity.1.F. Cervantes-Sodi et. al., submitted (2009).2.S. Curtarolo et. al. Phys. Rev. B 78, 054105 (2008).3.P. B. Amama et. al. Nano Lett. 9, 44 (2009).
9:00 PM - K5.19
Carbon Nanotubes Grown on Cu Substrates for Storage Applications.
Gowtam Atthipalli 1 , Prashant Kumta 1 2 3 , Wei Wang 4 , Alexander Star 5 , Brett Allen 5 , Yifan Tang 5 , Jennifer Gray 1
1 Materials Science and Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States, 2 Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States, 3 Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States, 4 Department of Materials Science and Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States, 5 Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
Show AbstractCarbon nanotubes with their unique 1-D character and their large aspect ratio are ideal candidates for anodes on suitable conducting substrates for energy storage applications. We studied the growth of carbon nanotubes on copper substrates using a nickel thin film as a catalyst. The catalyst was sputtered in a chamber having a base pressure in the ultra-high-vacuum regime. By adjusting the sputtering parameters including sputtering time, power, and pressure, the effects of the morphology and the structure of Nickel catalyst on the growth of carbon nanotubes have also been investigated. Multiple hydrocarbon sources as carbon feedstock (including methane and xylene) and corresponding catalyst precursors and varying temperature conditions were used during the Chemical Vapor Deposition (CVD) process to understand and best determine the ideal conditions for carbon nanotube growth on copper. . Correlation between the thickness of the thin film nickel catalyst and the carbon nanotube diameter is also presented in the study. A hypothesis for critical catalyst thickness range below which no carbon nanotube growth is observed is also postulated. The structure and morphology of the carbon nanotubes and the thin film nickel catalyst were studied using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Results will also be presented on experiments designed to yield carbon nanotubes on copper substrates with an extended surface area for energy storage applications.
9:00 PM - K5.20
Synthesis of a Closely Packed Multi-walled Carbon Nanotube Forest by a Multi-step Plasma Chemical Vapor Deposition Growth Method.
Yuichi Yamazaki 1 , Masayuki Katagiri 1 , Naoshi Sakuma 1 , Mariko Suzuki 1 , Shintaro Sato 2 , Mizuhisa Nihei 2 , Makoto Wada 3 , Noriaki Matsunaga 3 , Tadashi Sakai 1 , Yuji Awano 2
1 , MIRAI–Selete, Kawasaki Japan, 2 , MIRAI–Selete, Atsugi Japan, 3 , Semiconductor Company, Toshiba Corporation, Yokohama Japan
Show AbstractCarbon nanotubes (CNTs) have attracted wide-ranging interest because they have many excellent electrical, optical, thermal and mechanical properties. To realize maximum performance of CNT-based devices, CNTs must be well controlled in terms of diameter, length, layer number, CNT packing density and so on. The CNT packing density is one of the important parameters. To date, the highest CNT packing density has been ~1×1012 cm-2 reported by Zhong et al. The value was, however, one order of magnitude lower than the theoretical value, and the volume occupancy was estimated to be only about 3% for single-walled CNTs with the diameter ranging 1-3 nm. The difficulty of increasing CNT packing density in the growth is attributed to the ease with which catalytic nanoparticles aggregate at an elevated temperature prior to a CNT growth. In this study, we report a synthesis of a closely packed multi-walled carbon nanotube (CP-MWCNT) forest by a multi-step growth method, including a new approach to immobilize catalytic nanoparticles, using plasma-based chemical vapor deposition. The sequence to synthesize a CP-MWCNT forest has three steps: extremely high-density catalytic nanoparticle formation, immobilization of the nanoparticles and high-quality CNT growth. For immobilization of nanoparticles, CNT nucleation was performed. This is based on the concept that it is impossible for nanoparticles covered with graphene shells to migrate and coalesce. We found appropriate plasma treatments suitable for the respective steps described above. As a result, the continuous processing of all steps realized the synthesis of a CP-MWCNT forest. The CNT packing density reached one-half of the theoretical value, where the space of 30-40% was filled with MWCNTs. Although the CNT forest with such high volume occupancy has been reported by several authors, they applied the zipping effect of liquid to draw CNTs together to a CNT forest with low volume occupancy less than 3%. Since the catalytic nanoparticles are perfectly fixed, a CP-MWCNT forest can be grown at a wide growth temperature range. We confirmed the synthesis of a CP-MWCNT forest at 450-600 C. Using the different plasma conditions in the first step, the multi-step growth method enables us to fabricate a CP-MWCNT forest at a particular region such as trench and via hole. The smallest via size we successfully grew CNTs was 70 nm in diameter. The zipping effect is not applicable because the number of CNTs is predetermined at such a restricted region. Our method can open up opportunities for new and wider use of CNT forests.AcknowledgementsThe authors thank T. Mogami of MIRAI-Selete, and H. Shibata and K. Takaoka of Toshiba Corporation for their support and valuable comments. This work was conducted as part of the MIRAI Project under contract to the New Energy and Industrial Technology Development Organization (NEDO).
9:00 PM - K5.21
Controlling the Morphology and Tailoring the Spinnability of CNT Forests.
Yingying Zhang 1 , Guifu Zou 1 , Stephen Doorn 1 , Han Htoon 1 , Liliana Stan 1 , Marilyn Hawley 1 , Quanxi Jia 1
1 , Los Alamos National lab, Los Alamos, New Mexico, United States
Show AbstractControlled growth of carbon nanotubes (CNTs) towards different functions remains a critical challenge for their applications in many fields. The extraordinary mechanical properties of CNTs promise CNT fiber to be a very promising candidate for next-generation ultra-strong and light-weight fibers. Directly spinning CNT fibers from vertically aligned CNT arrays (CNT forests) is a promising way for the application of CNTs in field of high performance materials. However, most of the reported CNT forests are not spinnable. In the work, by controlling catalyst pretreatment conditions, we demonstrate that the degree of spinnability of CNTs is closely related to the morphology of CNT forests. Shortest catalyst pretreatment time led to CNT forests with the best spinnability, while prolonged pretreatment resulted in coarsening of catalyst particles and non-spinnable CNTs. By controlling the coalescence of catalyst particles, we further demonstrate the growth of undulating CNT arrays with uniform and tunable waviness. The CNT arrays can be tuned from well-aligned, spinnable forests to uniformly wavy, foam-like films. This work presents a systematical study on the correlation between catalyst pretreatment, CNT morphology and CNT spinnability.
9:00 PM - K5.22
Bimetallic Catalysts on N-Doped Carbon Nanotubes: High Catalytic Performance of Hydrogen Generation.
Weon Ho Shin 1 , Hyung Mo Jung 1 , Jeung Ku Kang 1
1 MSE, KAIST, Daejeon Korea (the Republic of)
Show AbstractWe synthesize bimetallic material dispersed N-doped carbon nanotubes (NDCNTs), which exhibit the high performance catalysts for hydrogen generation from borane/water solution. The NiPt catalysts can be obtained on the sidewalls of NDCNTs using N-mediated synthesis method in the presence of NaBH4 as a reducing agent. Nano-sized NiPt bimetallic catalysts are dispersed on NDCNTs as high crystalline alloy materials. This materials shows the superior hydrogen generation rate, where Ni0.72Pt0.28 bimetallic catalyst on CNTs exhibits the highest hydrogen generation rate up to 27.6 kg/hour/kg-catalyst having high potential for using automobile applications. Furthermore, the present one-pot and facile route to synthesize NiPt bimetallic catalyst on CNTs can be extended to prepare other alloy nano-materials exhibiting excellent catalytic property on various fields.
9:00 PM - K5.23
Inter-Tube Links in Defective Double-Wall Carbon Nanotubes: Electronic and Mechanical Effects.
Leonidas Tsetseris 1 2 , Sokrates Pantelides 2 3
1 Department of Physics, Aristotle University of Thessaloniki, Thessaloniki Greece, 2 Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee, United States, 3 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractSeveral key physical properties of graphitic systems have a sensitive dependence on the presence of even a small number of native defects and impurities. For example, vacancies and interstitials affect the mechanical, electronic, and transport properties of carbon nanotubes (CNT),[1,2] and they enhance the reactivity of the host systems towards various molecules, including typical precursors of nanotube growth.[3] Impurities like boron or nitrogen can act as dopants in semiconducting CNTs, while other extrinsic species, like iron or nickel, may be transferred to the CNTs from the metal catalysts used in growth.Here we report the results of first-principles calculations that probe the stability of intrinsic point defects and impurities in double-wall carbon nanotubes (DWCNTs). The calculations were performed within density-functional theory, with a plane-wave basis and large supercells to simulate isolated defects. As in our recent ab initio study [4] of native defects on graphene and single-walled carbon nanotubes, we identify stable configurations of single vacancies or interstitials, mechanisms that lead to the formation of defect complexes, including intimate vacancy-interstitial pairs, and processes, like diffusion, that play a role in the evolution of the imperfections.The DWCNTs we studied include (9,0)@(18,0) zig-zag and (6,6)@(11,11) armchair pairs, as well as chiral (15,3) and (16,3) segments around (8,0) and (9,0) tubes. In all cases, the most stable configuration for a C interstitial resembles the so-called spiro configuration of a single interstitial in graphite. Similar inter-layer bridge structures are obtained for boron impurities in the (9,0)@(18,0) DWCNTs. In contrast, vacancies, divacancies, and nitrogen impurities might exist in metastable inter-tube bridge configurations, but in their equilibrium structures they reside on the inner tube of the DWCNT. We also report the energy and force variations during inter-tube sliding and rotation and we find that the effect of various imperfections on the mechanical properties of DWCNTs depends strongly on the nature of the defect (bridge versus no bridge). Overall, our results are relevant for the evolution of defects, and, concomitantly, of the properties of DWCNTs both during CNT growth, or for long-term operation of related systems, especially in harsh environments that are susceptible to irradiation by energetic particles.The work was supported in part by the McMinn Endowment at Vanderbilt University and by DOE Grant No. DEFG0203ER46096.References[1] M. Huhtala et al., Phys. Rev. B 2003, 70, 045404.[2] A. Kis et al., Phys. Rev. Lett. 2006, 97, 025501. [3] L. Tsetseris, S. T. Pantelides, J. Phys. Chem. B 2009, 113, 941.[4] L. Tsetseris, S. T. Pantelides, Carbon 2009, 47, 901.
9:00 PM - K5.24
Pressure-induced Structural Phase Transition of Carbon Nanotubes into New Nanostructured Carbon Solids.
Masahiro Sakurai 1 , Susumu Saito 1
1 Department of Physics, Tokyo Institute of Technology, Meguro, Tokyo, Japan
Show AbstractCarbon nanostructured materials such as fullerene, carbon nanotube and graphene have been extensively studied in science and engineering, and it has been revealed that these materials exhibit various novel properties that are also useful in applications. Due to a large variety of possible atomic network topologies, various carbon nanostructured phases should be stable at normal pressure and temperature. Actually three different polymer phases have been produced from solid C60 by heating under high pressure and have attracted attention as novel semiconducting material. This indicates that other carbon nanostructured materials including carbon nanotubes can be a good precursor to other novel carbon phases which have interesting electronic properties, mechanical properties and so on. In this study, we perform the constant-pressure molecular-dynamics (MD) simulations for single-walled carbon nanotubes with a small diameter using the Parrinello-Rahman method and the transferable tight-binding (TB) model [1]. This TB model is based on the energetics obtained by using the density-functional theory (DFT) with the local-density approximation (LDA) and reproduces well not only sp2 and sp3 covalent bonds but also the sp2 interlayer interaction. First, we study the (6,6) and (7,7) armchair nanotube bundle. At 10 GPa, the system turns into an interesting sp2-sp3 structure which includes the zigzag graphene nanoribbons connected via the sp3 carbon network. It can be considered to be "graphitic nanoribbon solid". We calculate the electronic structure and the density of states (DOS) of the new phase by using the LDA in the DFT. As a result, the "graphitic nanoribbon solid" is found to be metallic and have dispersive bands associated with π states on the nanoribbon area.It is also found that some of the sp3-rich phases obtained under higher external pressure possess anisotropy in the direction of the initial tube-axis and have high hardness which is comparable to that of cubic diamond. In addition, bundles composed of both armchair and chiral nanotubes are studied. In this case, we choose (6,6) and (7,4) nanotubes, which are reported to be the nanotubes relatively abundand in experimentally purified sample [2]. Structural properties of transformed materials are discussed.[1] Y. Omata, Y. Yamagami, K. Tadano, T. Miyake and S. Saito, Physica E 29 (2005) 454. [2] Y. Sato, et al., Nano. Lett., 8 (2008) 3151.
9:00 PM - K5.25
CNT Growth on Metal Film Substrates by Direct Substrate Heating.
Florian Nitze 1 , Thomas Wagberg 1
1 Dept. of Physics, Umeå Universitet, Umeå Sweden
Show AbstractA simple glassware setup has been developed to grow carbon nanotubes (CNT). The substrate is heated directly on a serpentine heater leading to very low preheating times and high process efficiencies. This gives the possibility of controlled evaporation of liquids like propanol or ammoniac directly next to the substrate. In spite of this, the system is highly flexible and can be used with a variety of different carbon precursors. CNTs have been grown on thin metal film substrates and nano catalyst particles. We investigated the grown structures with scanning (SEM) and transmission electron microscopy (TEM) as well as Raman spectroscopy. It could be shown that even by this simple method the growth of CNTs is possible. We show that the system works with a broad spectrum of different precursors, catalysts and support substances both liquid and gaseous.
9:00 PM - K5.26
Ammonia Induced CNT Growth on Metal Films.
Florian Nitze 1 , Britt Andersson 2 , Thomas Wagberg 1
1 Dept. of Physics, Umeå Universitet, Umeå Sweden, 2 Dept. of Applied Physics and Electronics, Umeå Universitet, Umeå Sweden
Show AbstractNitrogen doped carbon nanotubes are grown by chemical vapor deposition. Ammonia is used as support gas to form metal nano catalyst particles. The effect of ammonia on the grown structures is investigated in a large temperature range from 630 °C to 910 °C, both when present during the growth or only in the pretreatment process. For characterization, scanning (SEM) and transmission electron microscopy (TEM) as well as Raman spectroscopy measurements are used. In earlier studies, we showed that the growth of CNTs carpets is enabled by the support of ammonia. We now present a more detailed study by Raman spectroscopy revealing the defect inducing effect of ammonia and its temperature dependence. We could also show in both SEM and TEM pictures that an ammonia pretreatment of the metal films leads to a non-uniform growth whereas a treatment during the whole process enhances uniformity of the grown structures.
9:00 PM - K5.27
Enhancement Mechanism of SWNT Yield with Al2Ox Buffer Layer in Low Temperature Growth.
Kuninori Sato 1 , Takahiro Maruyama 1 , Shigeya Naritsuka 1
1 , Meijo University, Nagoya, Aichi, Japan
Show AbstractRecently, we have been reporting single-walled carbon nanotube (SWNT) growth by a gas source method in an ultra-high vacuum (UHV) chamber using ethanol gas [1]. This growth technique enables SWNT growth in a high vacuum, which can reduce the growth temperature to below 400°C. We have also achieved enhancement of the SWNT yield by employing Al2Ox buffer layers [2]. However, the yield enhancement mechanism at low temperature has not been clarified enough. In this study, we investigated the enhancement mechanism of SWNT growth on the Al2Ox buffer layers at 400°C.Co/Al2Ox catalysts were formed on SiO2(100 nm)/Si substrates and Mo grids for TEM observation. The nominal thickness of the Al was 30 nm, and the Co thickness was 0.1 nm. Subsequently, SWNT growth was carried out by the gas source technique using ethanol. The sample temperature was maintained at 400°C during SWNT growth. The supply of ethanol gas was controlled by monitoring the ambient pressure, and was kept at 1×10-4 Pa.Raman results showed that the SWNT yield increased several fold by employing the Al2Ox buffer layers and that the G- bands were clearly observed on both substrates. Raman spectra with various excitation wavelengths showed several peaks in the RBM regions, indicating SWNT growth at 400°C. The G/D ratio of the SWNTs was about 10, which showed that the quality of the SWNTs was relatively good even at low temperature growth. The relative peak intensities in the lower-wavenumber RBM region (<240 cm-1) of the Raman spectra became higher when the Al2Ox buffer layers were inserted, indicating that the growth of larger diameter (> ~1.0 nm) SWNTs was enhanced. TEM observation showed that there is no significant difference in the diameter distribution of Co particles on the Al2Ox buffer layers. These results indicate that the larger size (> 1.0 nm) Co particles were activated by the Al2Ox buffer layer. Simulation of chemical reactions showed that dissociation of ethanol gas is below 10 ppb at 400°C and 10-4 Pa in the gas phase, and AES results also showed that most of the ethanol molecules were not dissociated on either the SiO2 or the Al2Ox at this temperature. These results indicate that most of the ethanol molecules were dissociated on the Co particles, indicating that the SWNTs grow through the surface diffusion of carbon atoms on the Co catalysts. Our results suggest that surface diffusion of ethanol molecules on the Al2Ox buffer layer plays an important role in enhancing the SWNT yield. [1] K. Tanioku, T. Maruyama and S. Naritsuka, Diamond Relat. Mater. 17 (2008) 589.[2] T. Maruyama et al. , J. Nanotechnol. Nanosci. to be published.
9:00 PM - K5.28
Development of an Ultra-fast Thermal Heating Cell for Fused CNT Junctions.
Amit Datye 1 , Kuang-Hsi Wu 1
1 Mechanical Engineering, Florida International University, Miami, Florida, United States
Show AbstractThe entire composite community is inspired by the remarkable properties of the Carbon Nanotubes (CNTs). Though an enhancement of modulus an increase of 27-fold in the modulus of composites in compression has been reported in the CNT composites, the highest increase in strength in CNT-polymer composites is only about 100%, which is far short of the theoretical prediction of the strength of the CNT nanocomposites. The major problem that hinders the success of the CNT composites lies with the lack of shear-stress transfer capacity between the nanotube and the matrix due to poor interface bonding, in addition to the difficulty in dispersion of CNTs. To circumvent the poor interface bonding and dispersion problems inherently associated with CNTs, this research has successfully demonstrated a new approach by fusing CNTs, using a low-cost thermal method, to form a 3-D CNT network or mesh. After a 3-D CNT network has been formed, polymer or other material can then be infiltrated into the CNT mesh to make ultra-lightweight and high-strength composites. The fused CNT junctions can also be used in nano-electronics to make nano-computer circuits, nano-diodes, and nano-junctions. Biomedical applications include bio-filters, drug-delivery applications. This innovative method is ideal for transition between lab-scale to industry scale applications of fused CNTs, fused CNT yarns and fused CNT paper.
9:00 PM - K5.29
CVD Growth of Vertically-Aligned Carbon Nanotubes in a Lamp-Heated Rapid Thermal Processor.
Zhengchun Liu 1 , Dingyou Zhang 1 , Zheng Xu 1 , Zhou Fang 1 , Chong Wu 1 , Jian-Qiang Lu 1
1 Center for Integrated Electronics, Rensselaer Polytechnic Institute, Troy, New York, United States
Show AbstractHigh-density vertically-aligned carbon nanotube (CNT) forests are promising for various applications such as IC interconnect via, super-capacitor, and chemical filter. In this work, a rapid thermal CVD process was explored for the growth of high-density CNT forest using a lamp-heated rapid thermal processor. It was found that heating at a very high ramp rate, e.g., 150 °C/s, can effectively suppress the agglomeration of fine catalyst nanoparticles and subsequently reserves them up to the CNT growth temperature (e.g., 775 °C). High density CNT forests were successfully grown on SiO2/Si substrate with Fe /Al thin layers as the catalyst. The effects of catalyst film thickness, growth time and catalyst position relevant to the lamps were also investigated.
9:00 PM - K5.3
Growth and Graphitization Improvement of a Single Aligned Carbon Nanotube.
Trilochan Paudel 1 , Yucheng Lan 1 , Gregory McMahon 1 , Dezhi Wang 1 , Zhifeng Ren 1 , David Carter 2 , Eugene Gene 2
1 Physics, Boston College, Chestnut Hill, 02467, Massachusetts, United States, 2 , The Charles Stark Draper Laboraory, Inc., Cambridge, 02139, Massachusetts, United States
Show AbstractA single vertically aligned carbon nanotube is successfully grown on a single catalytic nickel dot on silicon substrates. The nickel dot is made by electron beam lithography on Piranha-cleaned bare silicon wafer, and the vertically aligned carbon nanotube is grown by direct current plasma enhanced chemical vapor deposition (dc PECVD). The graphitization of the as-grown nanotubes is highly defected and need to be improved. We have applied a few techniques including Joule heating to enhance the graphitization. An STM probe installed in the TEM sample holder is used to in-situ heat the carbon nanotube and to improve the graphitization. This enhanced graphitization of a single aligned multiwalled carbon nanotube can be very useful for different applications such as nano actuators
9:00 PM - K5.30
Growth of Orthogonal Single-Walled Carbon Nanotube Arrays on Sapphire.
Tetsushi Nishi 1 , Hiroki Ago 1 2 3 , Kenta Imamoto 1 , Naoki Ishigami 1 , Masaharu Tsuji 1 2 , Tatsuya Ikuta 4 , Koji Takahashi 4
1 , Graduate School of Engineering Sciences, Kyushu University, Fukuoka Japan, 2 , Institute for Materials Chemistry and Engineering, Kyushu University , Fukuoka Japan, 3 , PRESTO, Japan Science and Technology Agency, Kawasaki Japan, 4 , Graduate School of Engineering, Kyushu University, Fukuoka Japan
Show AbstractHorizontally-aligned single-walled carbon nanotubes (SWNTs) grown on single crystal substrates, sapphire and quartz, has attracted a great interest, because the alignment is essential for device applications. The aligned SWNTs are oriented parallel to a specific crystallographic direction, and this alignment is attributed to the anisotropic van der Waals interaction between SWNTs and the atomic surface of the crystal [1, 2]. Here, we show a new SWNT growth direction that is orthogonal to its original growth direction. From previous studies, SWNTs normally grow in [1 -1 0 -1] direction on the r-plane sapphire [1]. We have surface-modified an r-plane sapphire such that SWNTs grow in the perpendicular direction. We have confirmed that SWNTs grow in this direction regardless of the gas flow and no remarkable steps were found in our substrate. Moreover, annealing allows the substrate to recover such that SWNTs grow in the original growth direction [1 -1 0 -1]. The different alignment direction is due to the different surface atomic arrangements appearing on the r-plane. Furthermore, site-selective modification was achieved for different growth direction on a single substrate. This new method of constructing nanotube architectures would contribute to SWNT device applications as well as the further understanding of the alignment mechanism.References[1] H. Ago et al., Chem. Phys. Lett., 408, 433 (2005). [2] C. Kocabas et al., J. Phys. Chem. C, 111, 17883 (2007).
9:00 PM - K5.31
Synthesis of Doped Carbon Nanostructures for Hydrogen Storage.
Daniele Mirabile Gattia 1 , Marco Vittori Antisari 1 , Renzo Marazzi 1 , Amelia Montone 1 , Emanuela Piscopiello 2 , Claudio Mingazzini 3
1 FIM MATCOMP, ENEA, Roma, Roma, Italy, 2 FIM MATCOMP, ENEA, Brindisi, Brindisi, Italy, 3 FIM MATING, ENEA, Faenza, Ravenna, Italy
Show AbstractLightweight materials for hydrogen storage are requested to have a widespread diffusion of hydrogen-correlated technologies. In the past, carbon nanostructures have been thought to be suitable materials for the storage of relevant amounts of hydrogen. In particular carbon nanotubes, carbon nanofibers, single-wall carbon nanohorns demonstrated unexpected gas and liquid adsorption properties due to their high surface area, surface reactivity and to the possibility of governing their porosity and of doping with other elements. Some results regarding hydrogen storage on carbon nanostructures have not been confirmed, but research on this field continues. Recently it has been reported that carbon materials doped with alkaline earth metals, like Ca, could theoretically adsorb relevant amounts of hydrogen. The interaction with hydrogen is supposed to depend on a charge transfer mechanism and hydrogen molecule dipole-induced polarization due to the presence of the alkaline earth metals. For these purposes we have synthesized carbon nanostructures, in particular single walled carbon nanohorns, with a homemade apparatus. An arc discharge is ignited between two rods 6 mm in diameter with an applied voltage between 20 and 30V and current flowing in the range 45-95 A. The lower electrode rotates on its own axis in order to homogenize the arc discharge, while the upper electrode advances toward the lower at a fixed speed depending on carbon sublimation. The arc is fed by an alternating current (AC) instead of traditional direct current (DC) and performed in air at atmospheric pressure. When a DC arc is ignited in gaseous environments, a hard crust containing carbon nanotubes and other by-products deposits at the cathode while the anode is consumed by carbon sublimation. On the other side when the arc is fed by an alternating current, both the two electrodes sublimate and light soot can be collected. In previous works we optimized soot collection by suitable arc conditions and by the use of a collector near the arc zone. This technique revealed to be simple with reproducible results and it is particularly suitable to co-sublimate graphite and other elements during arc due to reducing conditions created in the arc zone. Moreover some elements, like Ca, are known to be easily ionized elements and they could enhance arc stability and arc temperature control. In this work we report preliminary results on the synthesis of Ca/carbon composites realized by arching rods, prepared by cold isostatic pressing, containing mixtures of graphite and Ca precursors in a gaseous environment at atmospheric pressure. The material synthesized has been analyzed by scanning and transmission electron microscopy and X-Ray diffraction.
9:00 PM - K5.32
Influence of Molybdenum Concentration on the Phase Composition of Fe/Mo-MgO Catalysts for CVD Synthesis of Carbon Nanotubes.
Ana Paula Teixeira 1 , Bruno Lemos 2 , Leandro Magalhaes 1 , Jose Domingos Ardisson 1 , Clascidia Furtado 1 , Flavio Plentz 3 , Anderson Mesquita 1 , Rochel Lago 2 , Adelina Santos 1
1 Serviço de Nanotecnologia, Centro de Desenvolvimento da Tecnologia Nuclear - CDTN/CNEN, Belo Horizonte, MG, Brazil, 2 Departamento de Química, Universidade Federal de Minas Gerais - UFMG, Belo Horizonte, MG, Brazil, 3 Departamento de Física, Universidade Federal de Minas Gerais - UFMG, Belo Horizonte, MG, Brazil
Show AbstractThe addition of Mo to transition metals is known to have very important effects in the characteristics (number of walls, diameter distribution, presence or not of non-tubular nanocarbons) and yield production of carbon nanotubes (CNTs)[1]. Despite its importance the mechanism by which Mo favours the formation of carbon nanostructures is not yet totally clarified due to the complexity of the catalytic growth process [1,2]. In this work, a series of magnesia-supported Fe and Fe/Mo catalysts, were examined for CNTs growth by chemical vapor deposition (CVD) in ethylene (C2H2) and methane (CH4) and the influence of Mo as an activator in this system has been studied in details. The catalyst particles and CNTs were characterized by several techniques, including synchrotron X-ray diffraction, Mössbauer spectroscopy, micro Raman spectroscopy, SEM, TEM and EDS. The catalysts behavior was also studied in a two-stage temperature-programmed (TP) experiment. In the first TP stage, the catalyst was reduced with H2 and the hydrogen consumption was monitored by a conventional temperature-programmed reduction (TPR) procedure. After reduction, the gas stream was changed to CH4/Ar and the sample heated up to 900 C where the temperature was kept for 30 min. During that time, the H2 production was monitored and associated to the carbon growth species. The analysis of the different catalysts and carbon samples showed that the Mo plays an important role in the distribution of the iron ions and iron phases in the bimetallic catalyst. The dependence of the CNT growth on the Fe/Mo ratio in the Fe-rich region will be discussed. [1] M. Pérez-Mendoza, C. Vallés, W. K. Maser, M. T. Martínez, A. M. Benito, Nanotechnology, 16, S224-S229, 2005. [2] T. Saito, W.-C. Xu, S. Ohshima, H. Ago, M. Yumura, S. Iijima, J. Phys. Chem. B, 110, 5849, 2006. Work supported by the Brazilian Agencies CNPq and FAPEMIG, and by the Brazilian Institute of Nanotechnology, the Brazilian Network on Carbon Nanotube Research and LNLS - Brazilian Synchrotron Light Laboratory/MCT.
9:00 PM - K5.33
Nanometric Coating on Carbon Nanofibers Prepared by Plasma Polymerization of Ethylene Gas.
Ernesto Hernandez 1 , Maria Neira 1 , Luis Ramos 1 , Arturo Ponce 1
1 , CIQA, Saltillo, Coahuila, Mexico
Show AbstractPlasma treatment has attracted much interest by materials scientists due to its effectiveness in modifying the surfaces of different nanoparticles. The plasma technique in nanotechnology is made possible by the attachment of functional groups on the surfaces of nanostructures or by coating the surfaces of substrates with different polymers. Two substrates, carbon nanotubes and carbon nanofibers (CNFs), have exceptional physical and chemical properties that are very promising in revolutionizing the two principle fields of materials science and engineering. The two nanoparticle substrates have yet to be modified by plasma treatment to realize their new functionalized surface properties.In our present work, we attempt to use ethylene gas, as a monomer, to modify the surface of CNFs using plasma polymerization with a processing parameter of 100W of input plasma power for 60 min. The untreated and treated CNFs are characterized by Fourier transformed infrared spectroscopy (FTIR), Raman spectroscopy, thermogravimetric analysis (TGA), dispersion test in chloroform, and high resolution transmission electron microscopy (HRTEM). Dispersion test in chloroform indicated it enhanced the dispersion of the treated CNFs in this solvent. Both FTIR and TGA confirmed the presence of organic matter on the CNF surface as a clear evidence of surface modification. HRTEM verified the thickness of the nanometric coating to be 10-20 nm. A decrease in the frequency of the tangential mode in Raman from 1587 down to 1580 cm -1 was observed as a good indicator of interaction between the CNFs and the thin polymeric coating. The modified CNFs, if used as fillers to prepare nanocomposites with polyolefins, would definitely improve dispersion and interfacial adhesion to significantly increase the mechanical properties of nanocomposites.
9:00 PM - K5.34
Facile Method for the Deposition of Metal Oxide Nanowires on Carbon Nanotubes.
Tarik Bordjiba 1 , Daniel Belanger 1
1 chemistry, Université du Québec à Montréal, Montreal, Quebec, Canada
Show AbstractThe development of advanced composite materials based on metal oxide-carbon nanotubes is a new route for achieving highly efficient materials for different applications such as: catalysis, sensors, microelectronics, fuel cells, lithium batteries, and electrochemical capacitors. For electrochemical capacitors, active electrode materials include carbon, conducting polymers and transition metal oxides. Manganese oxide is a promising electrode material for electrochemical capacitors due to its low cost, natural abundance, environmental safety and its high theoretical capacitance. If one Mn atom in MnO2 is assumed to store one electron, then the specific capacitance of MnO2 should be around 1370 F/g. But, practically, this oxide show a specific capacitance of only one-fifth or one-sixth of the above value. Such low practical specific capacitance is due to the intrinsically poor electronic conductivity and dense morphology of the oxide [1]. Currently, there are mainly two efficient ways to reach high specific capacitance with manganese oxide. The first one is by developing nanostructred manganese oxide, which allows reaching a specific capacitance in the range of 700 F/g [2]. The second one is by the incorporation of carbon nanotubes in the MnO2 matrix which allows to reach specific capacitance ranging from 325 to 580 F/g [3-4]. We report, for the first time, the synthesis of a new composite electrode based on manganese oxide nanowires and carbon nanotubes (CNTs) by electrophoretic deposition of CNTs on a stainless steel (SS) substrate followed by direct spontaneous reduction of MnO4- ions to MnO2 to form the multi scaled SS-CNT-MnO2 electrode. The resulting material was characterized by scanning electron microscopy, energy dispersive X-ray analysis, cylic voltammetry and galvanostatic charge-discharge in a 0.65 M K2SO4 aqueous solution. The binderless SS-CNT-MnO2 nanocomposite electrode shows a very high specific capacitance of 869 F/g of CNT-MnO2 and good stability during long galvanostatic charge-discharge cycling. To the best of our knowledge, this is one of the highest capacitance for manganese oxide electrode ever reported. In addition to its applicability in electrochemical capacitors, this methodology could be extended to develop other high performance nanocomposite material electrodes based on carbon nanotubes and metal oxide for the future generation of electrochemical power sources. This strategy can find application not only in electrochemical power sources devices but also for catalysis, sensors and microelectronics.Reference: 1- M. Toupin, T. Brousse, D. Bélanger, Chem. Mater. 2004, 16, 3184.2- S. C. Pang, M. A. Anderson, T. W. Chapman, J. Electrochem. Soc. 2000, 147, 444.3- T. Bordjiba, D. Bélanger, J. Electrochem. Soc. 156 (5), A378 4- S. B. Ma, K. W Nam, W. S. Yoon, X. Q. Yang, K.Y. Ahn, K.H. Oh, K.B. Kim, J. Power Sources 2008, 178, 483.
9:00 PM - K5.35
Low Temperature Growth of CNT by Triode type RF Plasma CVD Method.
Y. Tanaka 1 , K. Sato 1 , S. Ishikawa 1 , Yoshiyuki Show 1
1 Dept. of electrical and electronic engineering, Tokai University, Hiratsuka Japan
Show AbstractCarbon nanotube (CNT) is one of the candidate materials for an electric double layer capacitor (EDLC), an electrochemical sensor, and interconnection in an ultra large-scale integrated (ULSI) circuit with 32nm technology node. These applications require growing the CNT at low temperature on substrate. In this study, the CNT was deposited by triode type RF plasma CVD method which employs the grid electrode in addition to the anode and the cathode electrodes. This grid electrode allows supplying the hydrocarbon radicals to Fe catalyst. The reaction between the hydrocarbon radicals and Fe catalyst forms the carbon nanotube at low temperature. The acetylene and hydrogen were used as source gases. RF power was kept at 50W. The growth temperature decreased up to 450oCThe CNTs with diameter of 20nm were vertically aligned against the Si substrate. These CNTs were - 8 micro m in length for 4 hour growth. It is noted that no carbon deposits such as CNT and amorphous carbon were observed when the RF power was not applied.In this study, the grid electrode was used in order to separate hydrocarbon radicals from the hydrocarbon plasma, which is generated by the RF power. The hydrocarbon radicals were supplied to the Fe catalyst by diffusion process and form the CNT with catalytic reaction. When the hydrocarbon ions in the plasma were supplied to the substrate, the amorphous carbon which consists of sp2 and sp3 bonding carbon was formed on surface of the catalyst. This catalyst surface did not react with the hydrocarbon radicals and did not contribute to the growth of the CNT. Therefore, the separation of the hydrocarbon radicals and the ions, and supplying the radicals to the catalyst are important parameter to grow the CNT at low temperature below 500oC.
9:00 PM - K5.36
Synthesis of High Quality Few Layer Graphene Sheets in Large Quantities by Radio Frequency Chemical Vapor Deposition.
Enkeleda Dervishi 1 , Zhongrui Li 1 , Fumiya Watanabe 1 , Abhijit Biswas 2 , Yang Xu 1 , Alexandru Biris 3 , Viney Saini 1 , Aurelie Courte 4 , Alexandru Biris 1
1 Nanotechnology Center, University of Arkansas at Little Rock, Little Rock, Arkansas, United States, 2 Department of Physics , University of Oklahoma, Norman, Oklahoma, United States, 3 , National Institute for Research and Development of Isotopic and Molecular Technologies, Cluj-Napoca Romania, 4 , Ecole d'Ingenieurs du CESI-EIA, La Couronne France
Show AbstractThis work reports a low-cost method for large scale production of high quality graphene via radio-frequency chemical vapor deposition. High quantities of graphene were successfully synthesized on the Fe-Co/MgO (2.5:2.5:95 wt.%) catalytic system utilizing acetylene as a hydrocarbon source at 1000 oC. The as-produced graphene sheets were purified in a single step by washing with a diluted hydrochloric acid solution under sonication. Next, they were thoroughly characterized by microscopy, spectroscopy, surface area analysis and X-Ray diffraction. Advanced transmission electron microscopy (TEM) and atomic force microscopy (AFM) analyses have indicated the formation of three to five layered graphene nanosheets. Thorough analyses by Raman spectroscopy were also performed demonstrating the presence of high quality and few-layer graphene samples. This low cost and highly reproducible method may be applied in a straightforward way to produce large quantities of graphene for various advanced applications.
9:00 PM - K5.38
Simultaneous Integration of Single-walled Carbon Nanotubes in Device Structures at Multiple Sites Using an Optically Driven Process.
Yunshen Zhou 1 , Wei Xiong 1 , Masoud Mahjouri-Samani 1 , Yang Gao 1 , Matt Mitchell 1 , Yongfeng Lu 1
1 Department of Electrical Engineering, University of Nebraska, Lincoln, Nebraska, United States
Show AbstractIn this study, we developed a technique for simultaneous integration of single-walled carbon nanotubes (SWNTs) in device structures at multiple sites through a single-step optically driven process.Single-walled carbon nanotubes (SWNTs) are amongst the most attractive one-dimensional nanostructures being investigated due to their intriguing properties and rich potential applications [1-3]. Intensive efforts have been devoted to the fabrication of SWNT-based nanodevices [3]. However, several bottlenecks, such as random growth of SWNTs at different sites and orientations, diverse chirality distribution and unpredictable SWNT-electrode contact, makes controllable and reliable fabrication of such devices an impossible mission. Therefore, there is a compelling demand on knowing the starting and ending points for the growth of SWNTs. Both in-situ and post-growth approaches have been proposed and investigated to achieve controllable integration of SWNTs in device structures at designated sites. Whereas, controllable integration of SWNTs still suffers from several restrictions, such as reliability, yield, cost effectiveness, and high process temperature. In this study, a single-step optically driven process was developed to achieve simultaneous integration of SWNTs at multiple sites. Both optical near-field effects and laser beam polarization influence were applied in a laser-assisted chemical vapor deposition (LCVD) process to enable the preferential growth of SWNTs at designated sites. A relatively low process temperature, around 500 oC, was achieved due to the localized heating at nanoscales caused by the optical near-field effects. SWNT-bridging structure arrays were fabricated simultaneously. Preferential growth of SWNTs at tip-shaped electrodes parallel to the polarization direction of the laser beam was evidenced theoretically and experimentally. This laser-based single-step process provides a reliable approach for fabricating SWNT-based devices by controllable integration of SWNTs at designated sites. References:[1] Dresselhaus, M. S.; Dresselhaus, G.; Avouris, P., Carbon Nanotubes Synthesis, Structure, Properties and Applications. Springer: 2001.[2] Dai, H. J., Accounts of Chemical Research 2002, 35, (12), 1035.[3] Collins, P. G.; Bradley K.; Ishigami M.; Zettl A., Science 2000, 287, 1801.
9:00 PM - K5.39
Carbon Nanotube Growth on Diamond Substrates for Thermal Management Applications.
Chakrapani Varanasi 1 6 , J. Petry 6 , L. Brunke 1 6 , W. Lanter 2 , H. Wang 3 , J. Bulmer 6 , J. Scofield 6 , V. Shanov 4 , M. Schulz 4 , G. Li 4 , T. Fisher 5 , P. Barnes 6
1 , University of Dayton Research Institute, Dayton, Ohio, United States, 6 , Air Force Research Laboratory , WPAFB, Ohio, United States, 2 , Innovative Scientific Solutions, Inc., Dayton, Ohio, United States, 3 , Texas A&M University, College Station, Texas, United States, 4 , University of Cincinnati, Cincinnati, Ohio, United States, 5 , Purdue University, West Lafayette, Indiana, United States
Show AbstractCarbon nanotubes were grown on free standing diamond and diamond/Si substrates by chemical vapor deposition to develop efficient thermal interface materials for thermal management of high power electronic devices. High quality translucent free standing diamond substrates up to 100 micron thickness were processed in a 5 KW microwave plasma enhanced CVD system using CH4 and H2 as precursors. Pulsed laser ablation or sputtering were used to deposit catalysts of Ni, Ni-W-Fe directly on to the diamond substrates without using an intermediate oxide buffer layer that is commonly used in CNT growth on Si substrates. Randomly oriented CNTs of 20 nm diameter forming a mat of 10 micron thickness on the diamond substrates were grown in 20 min. of growth time at 750 oC using C2H2 as a precursor. High quality CNTs on diamond showing a D/G peak ratio of 0.22 in Raman spectra were obtained using Ni catalysts deposited by sputtering. High resolution TEM analyses on these CNTs confirmed the high crystalline quality of MWCNTs showing parallel graphene layers indicating that high quality CNTs are possible to grow on diamond substrates without additional intermediate layers and thus minimizing the interfaces for better thermal management applications. Thermal resistance properties of the samples were characterized by using a photo acoustic method and an initial measurement indicated a thermal resistance of ~ 28.82 mm2K/W for a CNT/Diamond/ Si sample.
9:00 PM - K5.4
Morphology, Structure and Magnetic Properties of De-wetted Transition Metal Co- and Ni- Films as Catalysts and of Carbon Nanotubes Arrays.
Sanju Gupta 1 , S. Bianco 2 , P. Tiberto 3 , P. Martino 2 , F. Celegato 3 , A. Chiolerio 2 , A. Tagliaferro 2 , P. Allia 2 3
1 MURR & Physics, UMC 'n' PoliTO, Columbia, Missouri, United States, 2 Physics & Materials Science, PoliTO, Turin Italy, 3 Electromagnetic Division, INRIM, Turin Italy
Show AbstractInterest in the growth of carbon nanotubes by thermal and plasma-enhanced chemical vapor deposition techniques using transition 3d metals (Co, Fe and Ni) as catalyst support is still a subject of intense research in view of their promising intrinsic electrical, electronic, optical, chemical and magnetic properties allowing their use for a multitude of applications include field emission displays, gas-sensors and gas-storage media, nanoprobes, electromagnetic shielding coatings and magnetic storage recording media because of their high aspect ratio structures. In this paper, we report on the morphological, structural and magnetic properties of two of the important catalysts (Co and Ni films with varying thickness) prior to and post de-wetting that enabled the formation of island-like structures. Interestingly, we find different magnetic (superparamagnetic versus high coercivity ferromagnetic) states as a function of Co and Ni thickness and subsequent grain size. X-ray diffraction spectra revealed typical polycrystalline or multicomponent (fcc, hcp and oxide forms) structure directly affecting the magnetic properties. Moreover, the island-like Co and Ni films morphology facilitated the subsequent development by thermal chemical vapor deposition of carbon nanotube arrays that may enclose or embed the metal catalyst nanoparticles useful for various technologies. While we do not observe a strong magnetic anisotropy behavior from grown carbon nanotube arrays, we do find an enhancement in magnetic coercivity by almost two orders of magnitude with respect to their bulk counterpart for both the metal catalysts, which is promising for low dimensional, high-density magnetic recording media application. Fe and Ni nanoparticles in carbon nanotubes can be described by a modified Stoner-Wohlfarth model. Carbon nanotube arrays with Ni nanoparticles exhibit a weaker magnetic moment with a non-negligible diamagnetic signal from carbon nanotubes. We would like to thank Mr. P. Pandolfi for technical assistance in preparing some of the Co films and the author (S.G.) would like to thank fellowship from Politecnico of Turin, Italy.
9:00 PM - K5.41
Catalyst Free Synthesis and Characterization of Metastable Boron Carbide Nanowires.
Aruna Velamakanni 1 , K. Ganesh 1 , Yanwu Zhu 1 , Paulo Ferreira 1 , Rodney Ruoff 1
1 Mechanical Engineering and Materials Science and Engineering, University of Texas at Austin, Austin, Texas, United States
Show AbstractCatalyst-free growth of orthorhombic boron carbide (B8C) nanowires and nanobelts with diameters ranging from 10-50 nm and 100-150 nm respectively has been achieved by pyrolysis of diborane and methane in a quartz tube furnace. Electron diffraction analysis using a novel D-STEM technique indicates that the crystalline nanowires are single crystal orthorhombic boron carbide. Elemental analysis by EELS shows only boron and carbon while EDX and XPS show the presence of oxygen besides boron and carbon. Raman spectra are also reported which strongly suggest that boron carbide nanostructures that are formed at the inlet of the quartz tube in the lower temperature zone are composed of a boron-rich phase while those formed towards the center of the furnace in the high temperature zone are composed of a carbon-rich phase. This method provides a facile procedure for growing nanowires of a metastable, orthorhombic boron carbide phase (B8C), thus achieving kinetic vs. thermodynamic control.
9:00 PM - K5.42
Highly Entangled Hollow TiO2 Nanoribbons Templating Diphenylalanine Assembly.
Jin Ok Hwang 1 , Tae Hee Han 1 , Jun Kyun Oh 1 , Ji Sun Park 1 , Sang Ouk Kim 1
1 Materials Science & Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon Korea (the Republic of)
Show AbstractBiotemplating utilizes naturally generated biomolecular structures as templates for functional materials. Unlike synthetic template materials, biotemplates enable the construction of highly complicated hierarchical architectures through a mild, biocompatible process. In addition, naturally designed, highly specific biofunctionalities can be directly transferred to the final functional structures. TiO2 is a wide bandgap semiconductor with excellent photocatalytic activities. Owing to its attractive properties, TiO2 has been extensively used in various applications, including photocatalysis, sensors, and photovoltaics. In particular, nanotubular TiO2, which has an extremely large surface area and a one-dimensional anisotropic geometry, has demonstrated remarkably enhanced photocatalytic and photovoltaic properties. Here we demonstrate a novel fabrication process for highly entangled hollow TiO2 nanoribbons via templating of a peptide assembly. The organogel, which consists of a peptide nanoribbon framework, was readily assembled from an aromatic peptide of diphenylalanine. In contrast to the biomolecular structures that are usually used, nanoribbons constructed from highly ordered aromatic peptides exhibited remarkably high thermal stability, which allowed them to undergo a further functionalization process by means of atomic layer deposition (ALD) at a high temperature. ALD was used to deposit a thin TiO2 layer over a highly entangled 3-D peptide framework. After removal of the peptide template by pyrolysis, highly entangled hollow TiO2 nanoribbons were prepared. Our approach represents a unique pathway towards combining biomolecular assembly with a vacuum deposition process – two processes that are usually considered incompatible with each other.
9:00 PM - K5.43
Nanoscale Hollow Spheres − Microemulsion-based Synthesis, Container-Functionality and Gas Adsorption.
Claus Feldmann 1
1 Institute of Inorganic Chemistry, University of Karlsruhe, Karlsruhe Germany
Show AbstractA general microemulsion-based access to nanoscale hollow spheres allowing a wide flexibility regarding composition and size is presented. To this concern, metals (e.g., Au, Ag), oxides (e.g., AlO(OH), La(OH)3, ZnO, SnO2, TiO2) and sulfides (e.g., CdS, CuS) are realized. The outer diameter of the hollow spheres can be selectively adjusted between 10 and 40 nm and thickness of the sphere wall between 2 and 10 nm. Consequently, the inner cavity ranges from 5 to 30 nm in diameter [1−4]. Altogether, the flexibility in size and the variaty of available compounds turned out to be special advantages of the microemulsion approach.In addition to the variety of materials, the properties of nanoscale hollow spheres made from microemulsions are discussed. This includes container functionalities and drugg-delivery with inorganic salts (e.g. KSCN, K2S2O8, KF, KCl), biomolecules (e.g. phenylalanine, quercetine, cis-PtCl2(NH3)2) and fluorescent dyes (e.g., coumarine, rhodamine) [1,2,4]. Quantum-size effects are observed in case of metal hollow spheres such as gold and silver. With regard to ceramic oxide hollow spheres such as AlO(OH), SnO2, ZnO, TiO2 sensor applications, gas adsorption and storage as well as the mechanical properties are studied [3−6].[1] H. Gröger, F. Gyger, P. Leidinger, C. Zurmühl, C. Feldmann, Adv. Mater. 2009, 21, 1586.[2] D. H. M. Buchold, C. Feldmann, Nano Lett. 2007, 7, 3489.[3] C. Zimmermann, C. Feldmann, M. Wanner, D. Gerthsen, Small 2007, 3, 1347.[4] P. Leidinger, C. Feldmann, submitted.[5] F. Gyger, C. Feldmann, M. Hübner, N. Barsan, U. Weimar, submitted.[6] H. Gröger, A. Puls, F. Dreisbach, R. Staudt, C. Feldmann, submitted.
9:00 PM - K5.44
Deposition of Multi-component, Metallic and Non-metallic Nanoparticles in Carbon Nanocups.
Hyunkyung Chun 1 , Myung Gwan Hahm 1 , Latika Menon 2 , Yoshikazu Homma 3 , Pulickel Ajayan 4 , Yung Joon Jung 1
1 Department of Mechanical & Industrial Engineering, Northeastern University, Boston, Massachusetts, United States, 2 Department of Physics , Northeastern University, Boston, Massachusetts, United States, 3 Department of Physics, Tokyo University of Science, Tokyo, Shinjuku, Japan, 4 Department of Mechanical Engineering & Materials Science, Rice University, Houston, Texas, United States
Show AbstractThe synthesis of interesting morphologies of tubular carbon nanostructures such as carbon nanotubes and nanohornes has created a revolution in nanotechnology. Here we present architectures engineered from graphitic carbon, having up to 100,000 times smaller length/diameter (L/D) ratios compared to conventional nanotubes, revealing unique morphologies of nanocups, nanorings, and large area connected 2 dimensional nanocup film. Such highly engineered hollow nanostructures were fabricated using precisely controlled extremely short nanopores inside anodic aluminum oxide templates. Once the template with designed short nanochannels is generated, we deposit the graphitic cup morphologies by the pyrolysis of acetylene at the temperature of 660°C, without the use of any catalyst material. To make the graphitic nanoring morphology and to produce fully separated and length controlled nanocups, Ar ion milling was used. The structural change, indicating a higher degree of sp3 type of disorder and nanocrystallization of graphitic structure with the morphology changes from connoted carbon nanocups, to separated nanocups and nanorings, will also be discussed with Raman, XPS, and contact angle analysis. This nanoscale cup morphology was effectively used to hold and contain other nanomaterials, for example, single/binary metal, silica, and polymer (PSL) nanoparticles, leading to the formation of multi-component hybrid nanostructures with unusual morphologies. The results reported here will open up possibilities to integrate new morphologies of graphitic carbon in nanotechnology applications in nano-medicine (containers for nanogram quantities of materials, in drug delivery) and nano-metrology (nanoscale unit measures).
9:00 PM - K5.45
Comparison of Morphology and Microstructure of One-dimensional Titanate Nanotubes Prepared by Pressure-bomb and Microwave-assisted Hydrothermal Methods.
Ruey-an Doong 1 , I-ling Kao 1 , Sue-min Chang 2
1 Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu Taiwan, 2 Graduate Institute of Environmental Engineering, National Chiao Tung University, Hsinchu Taiwan
Show Abstract Various morphologies of one-dimensional (1-D) nanostructured titanate materials including nanosheets, nanotubes, nanowires and nanoribbons have been synthesized by the alkaline hydrothermal method. However, the morphology and microstructure of the TiO2-derived nanostructured material are highly dependent on the preparation conditions. More recently, the microwave-assisted hydrothermal method has been used for the fabrication of 1-D titanate nanomaterials. However, the change in morphology of titanate nanomaterials between traditional pressure-bomb and microwave-assisted hydrothermal methods has received less attention. In this study, the effect of preparation conditions in terms of hydrothermal temperature, duration, nature of raw materials, and alkaline concentration on the change in morphology, dimension and surface area of the nanostructured materials synthesized by conventional hydrothermal and microwave-assisted methods was systematically investigated. Two different TiO2 raw materials, Degussa P-25 and ST-01 TiO2 particles serving as the starting materials were added in 3-10 M NaOH solution at hydrothermal temperature of 60-230 degree C for 1-3 d using pressure bomb system and at 90-180 degree C for 1-2 h using microwave-assisted method. The morphology changed from nanoparticles/nanosheets, nanotubes, nanowires and then to nanoribbon when the hydrothermal temperatures increased from 60 to 230 degree C. ST-01 has a relatively high reactivity than that of P-25 TiO2 nanoparticles to form nanostructured material under mild conditions. In addition, the 1-D nanostructured materials have phase transformation during post-heat treatment process when calcination temperature was higher than 300 degree C and the crystalline phase transferred from titanante NaxH2-xTi¬3O7¬ nanotubes to TiO2(B) and then to anatase phase. In addition, nanosheet-like and nanotubual structures were found from ST-01 in NaOH concentrations higher than 5 M when microwave temperatures of 120 degree C was used. The synthetic temperature at 150 degree C for 1 h was found to be the optimal condition for fabrication of high-surface-area titanate nanotube using microwave-assisted hydrothermal methods. The N2 BET adsorption followed type IV or type V adsorption and the surface areas were in the range 400-500 m2/g, which is higher than those prepared from pressure-bomb method. In conclusion, microwave-assisted methods can produce titanate nanomaterials with high surface area and high aspect ratio under mild conditions, which is environmental friendly for development of hydrothermal methods to prepare titanate nanomaterials.
9:00 PM - K5.46
Synthesis of B-C-N Thin Films by RF Magnetron Sputtering and Their Structure and Optical Properties.
Ruqiang Bao 1 , Zijie Yan 1 , Douglas Chrisey 1
1 Materials Science and Engineering Department, Rensselaer Polytechnic Institute, Troy, New York, United States
Show AbstractB-C-N thin films have been deposited onto MgO(100) and KBr (optical grade) substrates in the temperature range from 25C to 650C by RF magnetron sputtering deposition technique, in which a mixed nitrogen and argon was used as gas source and boron carbide target was used. The composition of B-C-N thin films was determined by X-ray photoelectron spectroscopy. Selected area diffraction shows that the structure of the thin films is amorphous. Raman spectrum and Fourier transform infrared spectroscopy (FTIR) were used to study the local structure of B-C-N thin films deposited at different temperatures. The results show that the peaks in Raman spectrum and FTIR spectrum shifts with the increasing deposition temperatures, which indicate the structural change of B-C-N thin film with the deposition temperature. Also, optical properties for B-C-N thin film on MgO(100) substrate were measured and absorption coefficients at different deposition temperatures were calculated from optical properties. Finally, the bandgap of B-C-N thin film was derived from Tauc model. The difference of bandgap and optical properties of B-C-N thin films are related to the local structure, which were shown by Raman spectrum and FTIR.
9:00 PM - K5.47
Self-organized Nitrogen and Fluorine Co-doped Titanium Oxide Nanotube Arrays with Enhanced Visible Light Photocatalytic Performance.
Qi Li 1 , Jian Shang 1
1 Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Show AbstractHighly ordered TiO2 nanotube arrays made by anodization of titanium in fluoride-based electrolyte solutions have generated a great deal of interest in recent years. This particular TiO2 architecture provides a large surface area, a more efficient absorption of incident photons, and a decreased bulk recombination, all of which are beneficial to improving its gas-sensing, photocatalytic, and photoelectrochemical properties. To further enhance its photocatalytic performance, here we adopted an electrolyte design where a high concentration of ammoniate was used as the nitrogen doping source, and a proper amount of fluoride for both the formation of nanotube structure and the fluorine doping source. In situ incorporation of both nitrogen and fluorine dopants in the anodization process was achieved, and the crystallization of the as-prepared amorphous nanotube arrays under a nitrogen protective atmosphere preserved considerable amount of both dopants in highly crystallized nanotube arrays. Thus, unique self-organized nitrogen and fluorine co-doped titanium oxide (TiONF) nanotube arrays were created, which demonstrated enhanced visible light absorption capability and photodegradation efficiency on a model organic pollutant, methylene blue, under visible light illumination than TiO2 nanotube arrays. These enhancements could be attributed to both the nanotube structural architecture and nitrogen and fluorine co-doping effect. This novel TiONF nanotube array promises a wide range of technical applications, especially for environmental applications and solar cell devices.
9:00 PM - K5.48
Strategies for N-doping of TiO2 Nanotubes.
Cristian Fabrega 1 , Teresa Andreu 1 , Joan Morante 1 2
1 , University of Barcelona, Barcelona, Barcelona, Spain, 2 , IREC, Barcelona, Barcelona, Spain
Show AbstractAnodic growth of titania nanotubes have been extensively reported in recent years due to the potential applications in many areas, such as gas sensing, catalysis, solar cell and photo cleavage of water. The large surface area and excellent charge-transfer properties of the TiO2 nanotubes remarkably enhances their properties. However, its optical performance is limited by the wide band gap of TiO2 despite the optical absorption is enhanced because of the multiples reflections that take place in the walls of the nanotubes. In order to improve the absorbance in the visible region, a usual approach is through a structure modification with cations (Fe, Ni, Cr) or anions (N, C, F). Dopants are primarily selected according to their capacity to introduce energy levels in the oxide band gap, promoting light absorbance.In this work, we show two different methods to introduce nitrogen into the titania lattice substituting oxygen atoms. First, prior to anodization, the Ti foils used in this study were ultrasonically cleaned with acetone, rinsed with deionized water and then dried in nitrogen. Anodization was performed in a electrolyte consisting of 2% HF solution in Dimethylsulfoxide (DMSO) at 60V for 72h. After the anodizaton process the samples were annealed at 400 degrees for 3h.The first nitruration process was made in a chamber with a controlled ambient and temperature. The samples were exposed to an NH3 flow (1000 ppm in N2) at different temperatures and times in order to obtain a gradation in the doping level. The second nitruration route was performed in a hydrothermal reactor with a NH3 atmosphere (25%) with different temperature and times conditions.Structural and surface characterization has been mainly performed using FESEM, TEM, XRD and XPS. The photogeneration of hydrogen on N-doped titania nanotubes obtained with both process were evaluated electrochemically using Solar light (AM 1.5) as a radiation source.
9:00 PM - K5.5
Top-Down Approach to Align Single-Walled Carbon Nanotubes on Silicon Substrate.
Carlo Orofeo 1 , Hiroki Ago 1 2 3 , Naoki Yoshihara 1 , Masaharu Tsuji 1 2
1 , Graduate School of Engineering Sciences, Kyushu University, Fukuoka Japan, 2 , Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka Japan, 3 , PRESTO, Japan Science and Technology Agency, Fukuoka Japan
Show AbstractIn order to fully exploit the superior electronic properties of single-walled carbon nanotubes (SWNTs), the growth of horizontally aligned SWNTs on suitable substrates is a critical step for large-scale nanotube-based electronics. Such alignment has been demonstrated on single-crystal substrates such as sapphire (Al2O3) [1] and quartz (SiO2) [2]. SWNT alignment directly on SiO2/Si substrate is expected since the current FET configuration is fabricated on a Si wafer with an oxide layer. This alignment was demonstrated after plasma treatment of SiO2/Si but the position and direction of SWNTs were not controllable [3]. Here, we present a new, top-down based approach to align SWNTs directly on SiO2/Si substrate after substrate modification [4]. We modify the silicon substrate by creating trenches via electron beam (EB) lithography followed by reactive ion etching (RIE). Different top-down approach like anisotropic etching of silicon was also explored. After CVD, it was observed that nanotubes align in the direction along the created trenches regardless of the gas flow. From the experimental observations, the alignment mechanism will be discussed. Furthermore, devices created on the aligned SWNTs showed acceptable on/off ratio and mobilities comparable to transferred nanotubes on SiO2/Si substrate [5]. Our work demonstrates alignment of nanotubes along artificially-made trench structure on SiO2/Si that offers the possibility for large-scale integrated nanotube electronics for mass production. [1] H. Ago et al., Chem. Phys. Lett., 408, 433 (2005). [2] C. Kocabas, et al., Small, 1, 1110 (2005). [3] N. Yoshihara et al., J. Phys. Chem. C, 113, 8034 (2009). [4] C. M. Orofeo et al., Appl. Phys. Lett., 94, 053113 (2009). [5] L. Qu et al., Nano Lett. 8, 2682 (2008).
9:00 PM - K5.50
Anodic TiO2-Nanotubes: Growth, Modification and Application.
Robert Hahn 1 , Felix Schmidt-Stein 1 , Patrik Schmuki 1
1 University Erlangen, Department of Material Science, Institute of Surface Science, Erlangen Germany
Show AbstractSelf organized nanotubular structures of transition metal oxides grown on their metallic substrates, especially titanium [1], have attracted great scientific and technological interest due to the possibility to exploit their functional properties (such in photo-catalysis, solar energy conversion and as host for Li storage) in a nanotubular morphology. The conventional way to grow anodic TiO2 nanotubes is an optimized electrochemical treatment of Ti in fluoride containing electrolyte (for an overview see [2,3]).In the first part of the work we report on an entirely novel approach [4], the growth of nanotubes by s so-called RBA (rapid breakdown anodization). This nanotube growth-process is in comparison extremely fast (seconds instead of hours) and leads to surface coatings consisting of dense packed bundles of nanotubes with very high aspect ratios (tube length up to 50 micrometer, tube diameter of ~40 nanometer).The second part of the presentation will demonstrate that the electronic properties of these TiO2 nanotubes can be significantly modified by C-doping [5] to highly conductive phases [6]. In the third part, applications of these highly conductive TiO2 nanotubes will be discussed.Literature:[1] V. Zwilling, M. Aucouturier, E. Darque-Ceretti, Electrochim. Acta, 45, 921 (1999).[2] J.M Macak et al., Curr Opin Solid State Mater Sci 11 (2007).[3] A. Ghicov, P. Schmuki, Chem. Commun. Andrei Ghicov and Patrik Schmuki, Chem. Commun., 2791, doi:10.1039/b822726h (2009)[4] R. Hahn, J. M. Macak, P. Schmuki, Electrochem. Commun.,9, 947 (2007).[5] R. Hahn, A. Ghicov, J. Salonen, V. Lehto, P. Schmuki, Nanotechnology, 18, 105604 (2007).[6] R. Hahn et al. (2009) submitted.
9:00 PM - K5.51
Tunable Growth and Optical Properties of Indium Oxide Octahedrons, Nanowires and Tubular Nanoarrow Structures.
Mukesh Kumar 1 , Vidya Singh 1 , Bodh Mehta 1 , Jitender Singh 1
1 Physics, Indian Institute of Technology Delhi, New Delhi, Delhi, India
Show AbstractIn this study a bottom-up approach for controlled synthesis of indium oxide (IO) octahedrons, nanowires and indium-metal-filled nanotubes structures are reported under oxidizing and reducing ambient using vapor phase evaporation method. The growth has been carried out in a horizontal tube furnace maintained at 1000 °C, one atmosphere and argon carrier gas flow rate of 200 mL/min for 1-12 hrs. An alumina boat with a 1:1 mixture of IO and active carbon powder was placed at the center of the furnace while silicon substrates were placed downstream at 960 °C. A small reservoir (5-10 mL) of ethanol (reducing) and water (oxidizing) was placed in low temperature region (~65 °C) in upstream direction during the growth. SEM and HRTEM results show that the oxidizing reagent, water, results in the growth of IO nanowires and preserves the In/O stoichiometry throughout the length of the nanowires. The reducing reagent, ethanol, makes the growth environment indium rich resulting in the growth of indium-filled IO tubular nanoarrow structures. The HRTEM study reveals the growth of indium oxide octahedrons, nanowires and nanotubes along <100> direction. The growth of solid IO octahedron and nanowires, respectively, are attributed to vapor-solid and vapor-liquid-solid mechanism, whereas, for indium-filled tubular nanoarrow structures, a modified bottom-vapor-solid growth mechanism is proposed. The effect of deposition time and growth ambient on optical properties of IO nanostructures is investigated. A sixfold decrease in photoluminescence signal intensity at 590 nm with increase in deposition time from 3 to 12 h is observed in single crystalline indium oxide octahedron structures. Electron paramagnetic resonance and energy dispersive x-ray analysis confirm that the concentration of oxygen vacancies increases with deposition time. These results are contrary to the previous reports where oxygen vacancies were shown to be responsible for photoluminescence in indium oxide structures. Our results indicate that indium interstitials and their associated complex defects other than oxygen vacancies are responsible for the photoluminescence in In2O3 microstructures.
9:00 PM - K5.52
Self-doping in Boron Nanostructures: A Route to Structural Design of Metal Boride Nanostructures.
Hui Tang 1 , Sohrab Ismail-Beigi 1
1 Applied Physics, Yale University, New Haven, Connecticut, United States
Show AbstractSince the discovery of superconductivity in small-radius carbon nanotubes, superconductivity in one-dimensional nanostructures has become an appealing research topic. Metal boride nanotubes have attracted special attention in direct analogy with the superconducting bulk MgB2. MgB2 nanotubes are argued to have higher superconducting temperature than bulk MgB2. However, the structures of atomically thin metal borides are largely unknown. Moreover, it is unclear whether the stoichiometry MgBx with x=2 is the correct one. Clearly, some approach is needed to find optimal MgBx nanostructures while avoiding brute force search of all of configuration space.In this work, we present a novel self-doping picture for two-dimensional boron sheets and nanostructures. Using density functional theory, we show that for boron sheets, adding or removing atoms does not change the number of bonding states but merely changes their occupation. We demonstrate two applications of this self-doping picture. First, we propose a new general design rule for boron nanostructures, which rationalizes many stable boron nanostructures discovered previously and provides a general method for construction of stable boron structures. Second, based on self-doping and charge transfer considerations, we develop an efficient scheme to search for stable metal boride nanostructures for arbitrary stoichiometry MgBx. As an application and example, we apply this method to atomically thin MgB2 sheets and find a series of stable structures better than any reported in the literature. The most stable of these new structures is thus more likely to be the precursor of atomically-thin MgB2 nanotubes.
9:00 PM - K5.56
Substrate Morphology of Titanium Dioxide Nanotubes for Dye-sensitized Solar Cells.
Mukul Dubey 1 , Hongshan He 1
1 , South Dakota State University, Brookings, South Dakota, United States
Show AbstractIntroduction of vertically aligned titanium dioxide nanotubes arrays (TiNT) as a substitute for nanoparticle based photoelectrode is considered to be very promising for high efficiency dye sensitized solar cell (DSC). Its continuous columnar structure provides unidirectional electron flow with minimal recombination and hence high charge collection efficiency. Despite advantages, TiNT only showed ~7% energy conversion efficiency in DSC, which is far below the DSC with titanium dioxide particles as electron acceptor. The titanium dioxide nanotubes were usually prepared by anodization of titanium foil substrate. Misalignments and defects incorporated in nanotubes due to different substrate morphology lead to significant differences in the electron transport and light trapping capability of NTs. Our work primarily focuses on the effect of substrate morphology and its crystallographic orientation on the growth and PV performance of TiNT in DSC. We found commercially purchased Ti foil (99.9% pure) had surface fractures distributed throughout the substrate which led to bundling and cracking of NTs during anodization. The cracking becomes even severe after sintering due to unbalanced stress at the substrate crack centers. These cracks in turn lower the shunt resistant of the device leading to its poor performance. We found that the substrate Ti was polycrystalline in nature with average grain size of ~25 µm with different compositions at grains and grain boundaries analyzed by XRF. Preliminary studies by electron back scattered diffraction (EBSD) technique showed that there were different micro structural features throughout the substrate as well as in each grain which can inevitably affect the growth rate in different direction depending on the orientation of each micro-structure of such polycrystalline material. Moreover, The misalignment of TiNT caused by such preferred growth incorporate anisotropy in the refractive index of material which further reduced the light trapping capability and hence PV performance of the device. Further investigation suggested that chemical and physical pretreatment of substrate led to a potential change in morphology of substrate as well as the PV properties of the device. Our PV results indicated that the as purchased Ti substrate, chemically and physically treated samples have shown marked difference in the photovoltaic property of the device. The details of this study will be presented on the conference.ACKNOWLEDGEMENTThis research was supported by the National Science Foundation/ EPSCoR, Grant No. 0554609
9:00 PM - K5.57
La(OH)3 Hollow Spheres – Controllable Size and Container Functionality.
Peter Leidinger 1 , Claus Feldmann 1
1 Universitaet Karlsruhe (TH), Fakultaet fuer Chemie- und Biowissenschaften, Karlsruhe, Baden-Wuerttemberg, Germany
Show Abstract Hollow micro-/nanostructures are of great interest motivated by fundamental research as well as technical application[1,2]. On the nanoscale such structures are predominantly constructed based on solid templates, which may have the drawback of sphere wall destruction due to template removal afterwards[3]. Here, synthesis and application would gain significant variability if solid templates could be replaced. The goal of this work is the synthesis of nanoscale La(OH)3 hollow spheres with controllable and variable diameters of outer sphere wall and inner cavity. Furthermore the container functionality of as-prepared hollow spheres is validated.Nanoscale La(OH)3 hollow spheres were gained via a water-in-oil (w/o) microemulsion route with outer mean diameters of about 12 nm, 20 nm and 40 nm and constant wall thickness of about 4 nm. This is validated by DLS, SEM, STEM and TEM investigation[4]. We have chosen a microemulsion system which contains an aqueous polar phase and lanthanocene in n-dodecane as the non-polar phase. Thus, diffusion controlled precipitation occurs due to hydrolysis of lanthanocen at the phase-to-phase boundary. If the aqueous phase only consists of water, diffusion of lanthanocene to the inner micelle is favoured and leads to non-hollow nanospheres. If the aqueous phase contains inorganic salts (e.g. KF), the micellar polarity will increase. This coincides with changing the diffusion direction and leads to the formation of hollow spheres. The stabilizer (e.g. KF) furthermore acts as transportable species and can easily be freed by thermal treatment or etching. This is validated by DTA/TG, EDAX, FT-IR and XRD investigation.[1]Lou, X. W.; Archer, L. A.; Yang, Z. Adv. Mater. 2008, 20, 3987 [2]Gröger, H.; Gyger, F.; Leidinger, P.; Zurmühl, C.; Feldmann, C. Adv. Mater. 2009, 21, 1586[3]Sun, Y.; Xia, Y. J. Am. Chem. Soc. 2004, 126, 3892 [4]Leidinger, P.; Popescu, R.; Gerthsen, D.; Feldmann, C. submitted
9:00 PM - K5.58
Fabrication of Photoluminescent Peptide Nanotubes by Self-Assembly.
Jungki Ryu 1 , Seong Yoon Lim 1 , Chan Beum Park 1
1 Department of Materials Science & Engineering , Korea Advanced Institute of Science and Technology, Daejeon Korea (the Republic of)
Show AbstractThe fabrication of nanomaterials by peptide self-assembly is an attractive method for synthesizing novel nanomaterials because of unique features of peptides such as functional flexibility and molecular recognition capability. Furthermore, peptide-based nanofabrication is more environmentally friendly than conventional nanofabrication methods as it proceeds under mild conditions without harsh chemical substances. Among a number of self-assembling peptide, diphenylalanine (Phe-Phe, FF) is one of the simplest and best-known peptide building blocks that can readily form nanotubes in aqueous solutions. In this presentation, we demonstrate the synthesis of novel photoluminescent peptide nanotubes that were readily prepared by an in situ incorporation of luminescent lanthanide complexes, which was composed of small aromatic photosensitizers and/or lanthanide ions such as terbium (Tb) and europium (Eu), into FF nanotubes through a self-assembly process. We found that FF nanotubes acted not only as a host matrix for lanthanide complexes, but also as an efficient photosensitizer for luminescent lanthanide complexes. In particular, the incorporation of lanthanide ions together with photosensitizers into FF nanotubes resulted in synergistic enhancement of lanthanide photoluminescence. We confirmed the incorporation of lanthanide ions and photosensitizers into the FF nanotubes by multiple analyses such as fluorescence spectroscopy, electron and optical microscopies, and qualitative analysis with energy dispersive X-ray spectroscopy. In addition to the analyses, we could also fabricate FF nanotubes having various luminescent colors such as red, green, blue, cyan, purple, and so forth, through variation in the composition of lanthanide complexes. Our Recent Publications Related to This Presentation:J. Ryu, S. Y. Lim, C. B. Park, Advanced Materials, Vol. 21, pp. 1577-1581 (2009).J. Ryu, C. B. Park, Advanced Materials, Vol. 20, pp. 3754-3758 (2008).J. Ryu, C. B. Park, Chemistry of Materials, Vol. 20, pp. 4284-4290 (2008).
9:00 PM - K5.59
First Synthesis of Silicon Nanosheet.
Yusuke Sugiyama 1 , Hiroyuki Okamoto 1 , Yoko Kumai 1 , Takuya Mitsuoka 1 , Naoko Takahashi 1 , Hideyuki Nakano 1
1 , Toyota Central R&D Labs., INC., Nagakute Japan
Show AbstractSilicon nanosheet, which has the two-dimensional silicon backbone structure, is one of the most interest nanomaterials because of their nanoscale thickness and macroscale area. Here we report the soft synthesis of two-dimension silicon nanosheet terminated with phenyl groups. The silicon nanosheet is soluble in general organic solvents and stable under air, with the surface of silicon nanosheet terminated with phenyl groups and hydrogen. From the photoluminescence measurement, the band gap of the silicon nanosheet is determined about 3.0 eV, which is agreement with the theoretical direct band gap for Si6H6 [1]. It means that the silicon nanosheet indicate the nature of a monolayer sheet, reflecting completely solubility in organic solvents. We find a successful fabrication of silicon monolayer sheet by the solving the organic solution. The Atomic Force Microscopy (AFM) afforded strongly evidence of phenyl-capped silicon monolayer sheet. The thickness of the silicon nanosheet was measured at intervals between the sheets and the substrate surface, and yielded an average value of 1.7 nm. Furthermore, the observation of an atomically resolved AFM image of an individual sheet was succeeded, indicating that the sheet maintained the two-dimensional Si(111) backbone. [1] Tse, J. S. et.al. J. Mater. Chem. 8, 705-710 (1998).
9:00 PM - K5.6
Fabrication of Carbon Nanotubes Structures in SiO2 Channels.
Paul Hummel 1 , Tabbetha Dobbins 1 2
1 Institute for Micromanufacturing, Louisiana Tech University, Ruston, Louisiana, United States, 2 Dept. of Physics, Grambling State University, Grambling, Louisiana, United States
Show AbstractOne of the major challenges in utilizing the useful properties of carbon nanotubes (CNT) is their controlled deposition or positioning. Extensive research is being carried out to process the nanotubes into mechanical and electrical applications by controlled deposition approaches like electrophoretic deposition. In this work, single walled nanotubes (SWNT) and multi-walled nanotubes (MWNT) were self assembled and confined into trenches formed by UV lithography. Trenches of various sizes we etched into the silicon dioxide layer of a Si wafer, with the length varying from 20 to 170 um and the width varying from 2 to 8 um. By controlling the position of trenches, CNT structures with exact placement and orientation can be created to allow easily addressable CNT networks to be prepared for use in electrical and mechanical devices. SWNT dispersions are created by self assembling poly(sodium styrene sulfonate) PSS onto the SWNTs with a layer-by-layer technique. The dispersion is spin coated into prefabricated channels to form precise shapes and structures. The SWNT structures are characterized with Raman, verifying the structure is comprised of mostly SWNTs. The surface morphology of the SWNT structures is characterized with SEM and EDS. A Keithley probe station is used to measure the electrical properties of the composite films formed in the trenches.
9:00 PM - K5.61
Synthesis and Characterization of Composite Gold Nanosphere and Eu Doped Gadolinium Based Oxide Nanotube.
Kai Zhang 1 , Terrence Holloway 1 , Amber Wingfield 1 , Aswini Pradhan 1
1 , Norfolk State University, Norfolk, Virginia, United States
Show AbstractGold nanosphere and Eu-doped Gd2O3 nanotubes and their composite were synthesized through wet-chemical route at low temperature and ambient pressure. The nanostructures and composite were examined by X-ray diffraction, Scanning electron microscopy, transmission electron microscopy, photoluminescence and UV-visible absorption spectra. The characterization showed the nanotubes were uniformly distributed and the gold nanostructures were completely controlled. The results demonstrated that the nanostructures and the composite display luminescent behavior when irradiate with UV light. The gold nanostructures were tightly attached to the nanotube surface of Gd2O3 in the composite. The Eu-doped Gd2O3 nanotubes and their composite may be utilized for biomedical applications.
9:00 PM - K5.62
Catalytic Growth of Boron Nitride Nanotubes from Novel Precursors.
Benji Maruyama 1 , Shahana Chatterjee 2 , Placidus Amama 3 1 , Myung Kim 2 , Dmitri Zakharov 4 , Eric Stach 4 , Larry Sneddon 2
1 RXBN, Wright-Patterson Air Force Research Laboratory, Dayton, Ohio, United States, 2 Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania, United States, 3 University of Dayton Research Institute, University of Dayton, Dayton, Ohio, United States, 4 Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana, United States
Show AbstractMulti-walled and double-walled boron nitride nanotubes (BNNTs) have been effectively synthesized via catalytic chemical vapor deposition from novel precursors. Chemically synthesized monomeric and polymeric boron compounds were found to be desirable precursors for BNNT synthesis. In particular, growth of BNNTs and fibers from various boron precursors is demonstrated. The as-grown BN materials have been characterized using FESEM, TEM, and EELS. Our work opens a catalytic route to synthesis of BN nanotubes with high efficiency and low defect density.
9:00 PM - K5.63
Novel Boron Carbide Nanostructures by Arc-Discharge Method.
Sara Reynaud 1 , Ahmet Avci 2 , Steve Miller 1 , Sung Ryong Kim 3 , Manish Chhowalla 1
1 Materials Science and Engineering, Rutgers University, Piscataway, New Jersey, United States, 2 , Selcuk University, Konya Turkey, 3 , Chungju National University, Chungju Korea (the Republic of)
Show AbstractBoron carbide nanostructures possess unusually high thermal conductivity values [1]. Novel nanostructures of boron carbide (nominally B4C) were synthesized using the submerged arc discharge method [2-5]. The discharge in liquid nitrogen was created between two graphite electrodes, one of which (the cathode) was filled with microscopic boron carbide. Scanning electron microscopy studies revealed a wealth of novel nanoarchitectures such as nanowires, nanorods, spherical nanoparticles, and ribbon-like structures in the as- fabricated material. Transmission electron microscopy, Raman and Fourier infrared spectroscopy analyses confirmed that the detected nanostructures comprise of boron carbide. A method based on specific gravity of the different nanostructures has been developed to self-separate the various types of nanostructures. Electronic properties of the nanostructures were investigated by conductivity, photoluminescence, and thermal conductance measurements, opening new routes to novel applications using boron carbide nanostructures. [1]Kim SR, Gupta V, Yim SW, Chhowalla M. Transparent and thermally conducting nanocomposites from ultra long boron carbide NWs and PMMA, under revision in Nature Nanotechnology.[2]Sano N, Wang H, Chhowalla M, Alexandrou I, Amaratunga GAJ. Nanotechnology - Synthesis of carbon 'onions' in water. Nature 2001;414:506.[3]Sano N, Charinpanitkul T, Kanki T, Tanthapanichakoon W. Controlled synthesis of carbon nanoparticles by arc in water method with forced convective jet. Journal of Applied Physics 2004;96:645.[4]Wang H, Chhowalla M, Sano N, Jia S, Amaratunga GAJ. Large-scale synthesis of single-walled carbon nanohorns by submerged arc. Nanotechnology 2004;15:546.[5]Sano N, Naito M, Chhowalla M, Kikuchi T, Matsuda S, Iimura K, Wang HL, Kanki T, Amaratunga GAJ. Pressure effects on nanotubes formation using the submerged arc in water method. Chemical Physics Letters 2003;378:29.
9:00 PM - K5.64
Laser Chemical Vapor Synthesis (LCVS) of the BN-Nano-Structured Materials using Borazine Decomposition by Radiation of Fundamental and Second Harmonic Mixture of the YAG-Laser.
Arturo Hidalgo 1 2 , Valdimir Makarov 1 2 , Dachun Huang 1 , Gerardo Morell 1 2 , Brad Weiner 1 3
1 Physics, University of Puerto Rico, San Juan, Puerto Rico, United States, 2 , Institute Nanofunctional Materials, San juan, Puerto Rico, United States, 3 Chemistry, University of Puerto Rico, San Juan, Puerto Rico, United States
Show AbstractAbstract. We report a new method of BN-nanotube synthesis using Laser Chemical Vapor Decomposition (LCVD) of borazine by simultaneous radiation of both the fundamental and second YAG laser harmonics. It was found that yield of the nano-structured BN material is about 30%. The synthesis has been explained using simplest phenomenological chemical kinetics model, which includes degenerated chain reaction mechanism. Average concentration of active chemical species per single laser short was estimated as well as the average effective rate constant of the interaction of these species with borazine molecule was also estimated.
9:00 PM - K5.65
Controlling Nanocrystal Density and Location on Carbon Nanotube Templates.
Xiaohui Peng 1 , Stanislaus Wong 1 2
1 Department of Chemistry, State University of New York at Stony Brook, Stony Brook, New York, United States, 2 Materials and Chemical Sciences Department, Brookhaven National Laboratory, Upton, New York, United States
Show AbstractTwo types of nanoscale species (i.e., Au nanoparticles and CdSe quantum dots (CdSe QDs)) were conjugated in a stepwise manner with MWNTs via a covalent route by amidation. We have quantitatively probed the effects of varying oxidation treatments, precursor concentrations, and incubation time in order to rationally affect the spatial coverage and distribution of either Au NPs or semiconducting QDs on the MWNT sidewalls and tips. The degree of nanoparticle coverage was found to primarily vary with the intensity of the oxidation treatment, though the hydrophobicity of the nanotube as well as the chemical and steric characteristics of the nanocrystals also played a role in determining the ultimate architecture. In general, the stronger the oxidation treatment, the denser the coating of nanoparticles and/or quantum dots on the nanotube surface. In addition, the use of larger concentrations of precursor nanocrystals along with longer incubation time was conducive to the observation of higher nanoparticle densities on our nanotube templates. Furthermore, our overall results suggested that the nature of oxidation treatments primarily affected the spatial distribution of nanoparticles as well. A relative mild treatment led to a relative higher percentage of nanoparticles at the tips of carbon nanotubes. Interesting charge transfer, electromagnetic enhancement, and energy-transfer behavior between CNTs and the corresponding nanoparticles/quantum dots have been observed and will likely render such conjugates as key components in a range of nanoscale devices important for photocatalytic and solar applications.
9:00 PM - K5.66
Electronically Modified SWCNH Film with Iodine Adsorption.
Fitri Khoerunnisa 1 , Tomonori Ohba 1 , Hirofumi Kanoh 1 , Masako Yudasaka 2 , Sumio Iijima 3 2 , Katsumi Kaneko 1
1 Chemistry, Chiba University, Chiba, Chiba, Japan, 2 Nanotube Research Center, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan, 3 Material Science and Engineering, Meijo University, Nagoya, Aichi, Japan
Show AbstractSingle walled carbon nanohorns (SWCNH) exhibited n-type semiconductivity different from single walled carbon nanotubes (SWCNT). Also SWCNH has large surface area and thereby production of SWCNH films is expected to develop the application potential. Insertion of electron donor species into SWCNH is an effective method to control the physical and chemical properties. The objective of this research is to investigate the electronic properties changes of SWCNH film by Iodine adsorption. SWCNH films were prepared by coating SWCNH onto the PET substrate using the SWCNH suspension in 1,2-dichloroethane through the repeated dip-coating method. Iodine adsorption into SWCNH was carried out by ultrasonically mixing Iodine solution with SWCNH. The optical absorption of SWCNH film was measured by UV-NIR spectroscopy and the electronic structures and properties of SWCNH were examined using Raman spectroscopy, X-ray photoelectron spectroscopy, DC electrical conductivity and scanning electronic microscopy. The result showed SWCNH is efficiently modified with Iodine molecules by liquid phase adsorption. The adsorption of Iodine increased the electrical conductivity of SWCNH proportionally with Iodine enrichment on its structure. In addition, Iodine adsorption isotherm on SWCNH was Langmurian with the saturated amount of 185 ± 5 mgg-1. The alignment of SWCNH on PET substrate in high ratio tends to be similar to SWCNT alignment on the same substrate. The optical absorption spectrum of SWCNH showed interband transition around 680 nm attributed to S22 transition of the semiconducting of the tube structure, although the atomic structure of SWCNH is highly defective. X-ray photoelectron spectral changes gave the evidence of charge transfer or strong electronic interaction between SWCNH and Iodine.Key words: SWCNH film, Iodine adsorption, Electronic properties
9:00 PM - K5.67
Site-Selectivity Synthesis of Pd Nanoparticles Decorated-SWCNTs Nanocomposites.
Zhenquan Tan 1 , Hiroya Abe 1 , Makio Naito 1 , Satoshi Ohara 1
1 , Joining and Welding Research Institute, Osaka University, Ibaraki, Osaka, Japan
Show AbstractDecoration of Palladium (Pd) nanoparticles (NPs) on single walled carbon nanotubes (SWCNTs) is an interesting topic because of their great potential applications, such as high performance catalyst, fuel cell, and chemical sensors. In this study, we report a simple method to fabricate Pd NPs decorated-SWCNTs nanocomposites [1]. Interestingly, Pd NPs were found to be of site selectivity on the two sides of SWCNTs. The unique structures and the optical properties have been characterized by SEM, TEM, XRD and UV-Vis absorption spectroscope.[1] Z. Tan, H. Xu, H. Abe, M. Naito, S. Ohara, J. Nanosci. Nanotechnol., in press.
9:00 PM - K5.69
Fabrication of Molecular Nanogate to Inside of Single Wall Carbon Nanohorn.
Tomonori Ohba 1 , Katsumi Kaneko 1
1 Graduate School of Science, Chiba University, Chiba Japan
Show Abstract Single wall carbon nanohorn (SWCNH) has similar structure to single wall carbon nanotube in structure. 1 The inside of SWCNH is sealed with a carbon wall. Then molecules cannot enter into the inside. However, molecules can be accessible to the inside when nano-sized gates are donated on the carbon wall. 2,3 Thus, the nano-sized gate, which is named nanogate, works as molecular path into the inside. Molecular selectivity can be obtained by the control of nanogate size distribution. Murata et al. reported the opening treatment of SWCNH by partial oxidation. 2 However, the nanogate size distribution was broad and then high selectivity could not be obtained for the SWCNH. We attempted the donation of molecular nanogate on SWCNH by careful oxidation to get highly selective nanogate in molecular size.
Heat treatments in oxygen atmosphere at 673 K for 0.5 h and then hydrogen atmosphere at 600 K for 2 h provide the fabricated SWCNH with molecular nanogate. The nanogate size distribution was evaluated by multi-molecular probe method using N2, CH4, and SF6; N2 molecules were fully accessible to the inside, CH4 was partially adsorbed, and SF6 could not be adsorbed. Then the molecular nanogate has a sharp size distribution from 0.4 to 0.45 nm. The nanogate is useful for molecular sieving of simple molecules. Molecular nanogate is also essential for the appearance of unique mechanism of adsorbed molecules.
1 Iijima, S.; Yudasaka, M.; Yamada, R.; Bandow, S.; Suenaga, K.; Kokai, F.; Takahashi, K. Chem. Phys. Lett. 1999, 309, 165.
2 Murata, K.; Hirahara, K.; Yudasaka, M.; Iijima, S.; Kasuya, D.; Kaneko, K. J. Phys. Chem. B 2002, 106, 12668.
3 Ohba, T.; Murata, K.; Steele, W. A.; Kokai, F.; Takahashi, K.; Kasuya, D.; Yudasaka, M.; Iijima, S. Nano Lett. 2001, 1, 371.
9:00 PM - K5.7
Effect of Catalyst and Underlayer Metal on Contact Resistance in Carbon Nanotube Via Interconnect.
Xuhui Sun 1 , Ke Li 1 , Raymond Wu 1 , Patrick Wilhite 1 , Cary Yang 1
1 Center for Nanostructures, Santa Clara University, Santa Clara, California, United States
Show AbstractVertically aligned carbon nanotubes (CNTs) directly grown on metal electrode underlayer are promising materials in applications such as on-chip interconnects, nanoelectrode arrays, nanoelectromechanical systems, and field-emission devices, most of which are based on existing silicon process technology. For these applications, electrical properties such as resistance and control of geometry such as alignment, diameter, and length are critical factors in materials growth and device fabrication. Thus it is essential to optimize the growth of CNTs for device fabrication compatible with existing technology. One critical factor in via interconnect fabrication using CNTs is the choice of underlayer metal. To study this, one must have an accurate and reliable technique to extract contact resistance between the CNT and the underlayer metal in a vertically aligned configuration. Minimizing contact resistance is the key in all applications, especially when the dimension is in the nanoscale. In this work, Si process-compatible metals, Ti, Cr, and Al, are used as underlayer metals to study the growth behaviors and contact resistances of vertically aligned CNTs, together with the two most effective catalysts, Ni and Fe. Relationships between contact resistances and various combinations of catalysts and underlayer metals, as well as the effects of other CNT growth conditions such as temperature, time, and gas flow rates are investigated. The contact resistances between as-grown CNTs and underlayer metals are determined using a two-terminal extraction method [1]. From extracted contact resistances for various combinations of catalysts and underlayer metals, as well as growth conditions, we arrive at a combination which yields the minimum contact resistance. Further, the interface between CNT and underlayer metal is investigated using X-ray photoemission spectroscopy (XPS) to elucidate the relationship between local electronic structure and contact resistance. The resulting improved CNT growth process is used for fabricating via interconnect test structures for further performance and reliability studies.[1] W. Wu, S. Krishnan, T. Yamada, X. Sun, P. Wilhite, R. Wu, K. Li, and C.Y. Yang, “Contact resistance in carbon nanostructure via interconnects,” Applied Physics Letters 94, 163113 (1-3) (2009).
9:00 PM - K5.70
Carbon Onion Films-Molecular Interactions of Multi-Layer Fullerenes.
Raed Alduhaileb 1 , X. Fan 1 , K. McElroy 1 , V. Ayres 1 , B. Jacobs 1 , A. Hirata 2 , M. Horikoshi 2 , M. Galinato 3 , N. Lehnert 3
1 , Michigan State University, Lansing, Michigan, United States, 2 , Tokyo Institute of Technology, Tokyo Japan, 3 , University of Michigan, Ann Arbor, Michigan, United States
Show AbstractFilms and networks of fullerene carbons are under investigation for multiple applications in alternative energy, including both energy conversion and nanoscale tribology. In each case, film stability is a product of the fundamental molecular interactions of the fullerene carbon and its environment. Carbon onions, which are 7-10 concentric graphene shell structures, have demonstrated superior tribological characteristics and film stability in both air and vacuum, when to compared to pure C60 films [1]. In the present experiments, the fundamental molecular characteristics of carbon onions that govern rolling, sliding, and interactions with wear surfaces are assessed using high-resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS), and low temperature multi-color micro-Raman spectroscopy. Tribological performance is investigated with ball-on-disk-tribometry and atomic force microscopy (AFM). The effect of bond hybridization sp2/sp3 is studied across a series of carbon onions, whose topology changes from spherical to polyhedral as a function of growth temperature. These are grown from nanocrystalline diamond at 1700oC, 2000oC, and 2300oC in an inert atmosphere in an infrared gold image furnace. The nano-structural properties of the carbon onions are examined prior to and post ball-on-disk experiments. Carbon onions have great potential as environmentally benign solid lubricants with no requirement for heavy metal additives in a variety of environments including vacuum.[1] A. Hirata, M. Igarashi, T. Kaito, 2004. Study on solid lubricant properties of carbon onions produced by heat treatment of diamond clusters or particles. Tribology International 37: 899–905.Present address B.W. Jacobs; Sandia National Laboratories, Livermore, CA
9:00 PM - K5.71
Doping of Hexagonal Boron Nitride via Intercalation: A First-Principles Study.
Fumiyasu Oba 1 , Atsushi Togo 1 , Isao Tanaka 1 2 , Kenji Watanabe 3 , Takashi Taniguchi 3
1 Department of Materials Science and Engineering, Kyoto University, Kyoto Japan, 2 Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya Japan, 3 Advanced Materials Laboratory, National Institute for Materials Science, Tsukuba Japan
Show AbstractUltrawide-gap semiconductors for optoelectronic applications in the deep-ultraviolet region have been extensively explored in recent years. Hexagonal boron nitride (h-BN) has emerged as a new candidate for such systems since its large exciton binding energy of 0.15 eV and ultraviolet lasing using electron-beam excitation was reported [1]. In addition, its related low-dimensional systems such as BN single sheets have attracted interest in view of their specific physical properties [2]. The doping of h-BN and related systems should widen their applications, but it has not yet been reported. A difficulty is expected in their doping because of the characteristic two-dimensional structures; the doping strategies established for conventional semiconductors are unlikely to work well. Therefore, theoretical modeling is necessary to attain the efficient doping of h-BN systems. In the present study, we propose a strategy for the doping of h-BN based on first-principles calculations.The calculations were performed using the plane-wave projector augmented-wave method and the PBE0 hybrid functional, as implemented in the VASP code [3]. To evaluate the performance of dopants as donors or acceptors, their formation and ionization energies were obtained using 288-atom supercells.As a result of systematic calculations, we found that substitutional dopants yield deep and localized in-gap states in h-BN, unlike their behavior in typical semiconductors including c-BN. In contrast, intercalated atoms with high and low electronegativities perturb the host valence and conduction bands weakly, resulting in the formation of shallow acceptor and donor states in h-BN with an exceedingly wide band gap of 6 eV, respectively. The intercalated dopants are found to migrate easily over low energy barriers along the BN layers. However, their migration can be suppressed by the formation of defect complexes involving substitutional dopants, with the shallow acceptor or donor characteristics preserved. The strategy proposed here is also applicable to h-BN ultrathin layers and extendable to the doping of BN single sheets via adsorption.[1] K. Watanabe, T. Taniguchi, and H. Kanda, Nat. Mater. 3, 404 (2004). [2] H. Dil et al., Science 319, 1824 (2008). [3] J. Paier, R. Hirschl, M. Marsman, and G. Kresse, J. Chem. Phys. 122, 234102 (2005).
9:00 PM - K5.73
On the Formation of Carbon Linear Atomic Chains from Graphene: A Theoretical Study.
Marcelo Flores 1 , Gustavo Brunetto 1 , Douglas Galvao 1
1 Applied Physics, State University of Campinas, Campinas, Sao Paulo, Brazil
Show AbstractRecently, different experimental groups have reported the formation of carbon linear atomic chains (CLAC) from graphene constrictions [1,2]. Interestingly, the formation of CLACs exhibits many features also observed in the metallic LAC formation [3]. In this work we investigated CLAC formation from graphene nanoribbon stretching using molecular dynamics simulations. We have considered different ribbons with zigzag, armchair, and/or mixed borders of different sizes. For comparison purposes we investigated hydrogenated and non-hydrogenated structures. The size and large number of structures to be analyzed precludes the use of full quantum methods. We have carried out the simulations using a binding energy bond-order (BEBO) method as developed by A. C. T. van Duin and collaborators and implemented in ReaxFF code [3]. In contrast with more standard molecular force fields ReaxFF can handle making/breaking chemical bonds and the atomic hybridizations are allowed to change during the simulations. The stretching is simulated by increasing the cell size. Four temperatures (100K, 300K, 600K and 900K) were used within a NVT ensemble. Our results showed that CLACs are preferably formed when zigzag edges are present. For the equivalent hydrogenated structures the structural gain stability provided by the H atoms makes the LAC formation more difficult, which increases the probability of nanoribbon breakage. For the temperature range considered here the probability of LAC formation is directly proportional to the temperature value. The simulations reproduced well the main experimental features, showing that the methodology is physically sound. From the simulations it was possible to obtain detailed information about the atomistic mechanisms of graphene breakage, in particular the ones associated with LAC formation.[1] C. Jin, H. Lan, L. Peng, K. Suenaga, and S. Iijima, Phys. Rev. Lett. 102, 205501 (2009).[2] A. Chuvilin, J. C. Meyer, G. Algara-Siller, and U. Kaiser, arXiv:0905.3090v1[3] J. Bettini, F. Sato, P. Z. Coura, S. O. Dantas, D. S. Galvao, and D. Ugarte, Nature Nanotechnology 1, 182 (2006).[4] A. C. T. van Duin, S. Dasgupta, F. Lorant, and W. A. Goddard III, J. Phys. Chem. A 105, 9396 (2001).
9:00 PM - K5.74
Highly Efficient Formation of Anodic TiO2 Nanotubes from Sputtered Ti Films.
Haidong Zheng 1 , Abu Sadek 1 , Michael Breedon 1 , Kourosh Kalantar-zadeh 1
1 School of Electrical and Computer Engineering, RMIT University, Melbourne, Victoria, Australia
Show AbstractAnodic TiO2 nanotubes (ATNs) by anodization have attracted great interests due to their fascinating applications. These nanotubular structures have extremely high surface-to-volume ratio; excellent charge transport ability and relatively easier control on tube properties. After almost 10 years of research, anodic TiO2 nanotubes have been developed into the third generation, which nanotubes could be grown up to 1mm long with various properties. However, these were achieved on Ti foil substrate that unfortunately limits their applications. Synthesizing long and transparent ATN films from Ti films deposited on foreign substrates are very important to optical applications, however, the high applied voltages with long duration will usually damage the adhesion between ATN films and foreign substrates.In this work, we present the method for producing high quality transparent ATN films on foreign substrates and provide a comprehensive study on the volume expansion issue on these ATN films. Ti films were RF (radio frequency) sputtered on FTO (fluorine-doped tin oxide) glass, normal glass and quartz substrates. Anodization was carried out in a conventional anode (sample) – cathode (Pt) setup. The electrolytes are ammonium fluoride (NH4F) in ethylene glycol with different amounts of water content.It was found that long and transparent anodic TiO2 nanotubes could be produced on all three kinds of substrates in less than 5 minutes, and up to 9.2±0.3 μm thick ATN films were obtained. The transparency of the ATN films was found to reduce as the film thickness increases. While the growth rates of the ATNs were highly dependent on the composition of electrolyte and the applied voltage, it was found that only in the range of 0.3-0.5%(wt) NH4F with 2-3%(vol) H2O at 60V producing 10-20 mA cm-2 anodic current density, uniform transformations from sputtered Ti to ATNs were obtained. Within these preferred anodization conditions, it was observed that the formed ATN films exhibited over 2.9 times increase of thickness compared with original Ti films. However, the volume expansion ratio obtained from sputtered Ti film to ATN film conversion is consistent with the one (Pilling-Bedworth ratio 1.75 – 1.9) for compact Ti to compact TiO2 conversion. Using the evaluated volume of ATN films and the total charge recorded during anodization in Farady’s Law calculation, the efficiency of the ATN formation was surprisingly found to be very close to 100%. In conclusion, this work has extended the growth of TiO2 nanotubes on foreign substrates, and it will provide an insight study on the thickness change and volume expansion for the ATNs formation.
9:00 PM - K5.75
Uniform Coating of WOx on TiO2 Nanotubes for Enhanced Electrochromic Performance.
Haidong Zheng 1 , Jianzhen Ou 1 , Michael Breedon 1 , Abu Sadek 1 , Kourosh Kalantar-zadeh 1
1 School of Electrical and Computer Engineering, RMIT University, Melbourne, Victoria, Australia
Show AbstractTungsten oxide (WOx) is one of the most promising materials for highly efficient electrochromic devices. It is believed that the modified electronic structure of WOx due to the intercalation of protons, such as H+ and Li+, causes the coloration of the oxide. The surface morphology and microstructure of the WOx films are of prime importance for improving their electrochromic effect. Highly porous structure is very favourable for fast ion movements. Increasing the thickness of WOx film will enhance the change of transmission spectra; however, for compact films, increase of thickness means higher applied voltage and slower response. Therefore, it is extremely desirable to have thick enough WOx films with high degree of porosity for electrochromic applications.In this work, we present a facile method for coating a WOx layer uniformly onto the anodic TiO2 nanotubular (ATN) films. The TiO2 nanotubes were obtained by anodizing Ti foil which was carried out by a conventional anode (sample) – cathode (Pt) setup in ethylene glycol with ammonium fluoride. The anodization of Ti resulted in TiO2 nanotubes of ~4 µm long. Coating of WOx was conducted in 0.5M Na2WO4 aqueous solution, where the ATN film was the cathode and a Pt plate was the anode. 2.5 V was then applied between the two electrodes for 15 minutes. After the WOx deposition, scanning electron microscopy (SEM) revealed that while the general structure of TiO2 nanotubes remained, the walls of the tubes were significantly thickened uniformly. Energy dispersive X-ray (EDX) analysis confirmed that a significant amount of W was present, and the amount of oxygen was also increased. X-ray diffraction (XRD) pattern of the as-prepared sample revealed that the coated WOx was mainly amorphous, and small peaks of hydrated WO3 were present.For the electrochromic effect, the as-prepared sample was placed as working electrode in 0.5M HNO3 electrolyte against a Pt counter electrode. Reflectance measurement was conducted by a broad-band visible light of 12 mW cm-2 and a Thorlab S120 optical power meter. It was found that coloration appeared when 0.7V was applied, and the sample color changed to dark blue when 2V and above was applied, with maximum 97% reduction on reflectance was obtained. The response95% and recovery95% time of this electrochromic effect were both found to be less than 500ms. Stability testing was also performed by 10,000 bleached-darkened cycles, no significant degradations in coloration and response-recovery time were observed. In contrast, coloration on the plain ATN films started at 3.2V, and only 20% reflectance reduction was obtained. For compact ~900 nm WO3 by reactive sputtering, maximum 45% of reflectance was reduced when darkened, and both the response and recovery time were over 5s. An electrochromic device was also fabricated using the transparent WOx coated ~1.2 µm ATN films on fluorine-doped tin oxide (FTO) glass. 75% (bleached) and 30% (darkened) transmission were obtained.
9:00 PM - K5.76
Novel Tubular-Shaped Nanoparticles for Application as a Ferrofluid.
Robert Zierold 1 , Zhenyu Wu 2 , Julien Bachmann 1 , Carl Krill 2 , Kornelius Nielsch 1
1 Institute of Applied Physics, University of Hamburg, Hamburg, Hamburg, Germany, 2 Institute of Micro and Nanomaterials, Ulm University, Ulm, Baden-Württemberg, Germany
Show AbstractA novel, fully tunable preparation of short ferromagnetic nanotubes (aspect ratio <15) is presented. The combination of porous alumina as a template with atomic layer deposition (ALD) makes it possible to produce magnetic nanotubes with tailored properties [1]. Due to the self-limiting nature of sequential surface reactions, ALD is suited to covering nanostructured substrates with conformal layers of thin films at nanometer thickness resolution. By reducing the anodization time of aluminum and implementing multilayer ALD, it is possible to control all system parameters (e.g. length, wall thickness, magnetic moment) of the tubular nanoparticles. Silicon dioxide is deposited as a protection layer against wet etching and aerobic reoxidation by sequential pulses of 3-aminopropyltriethoxysilane, water and ozone [2]. The starting point for the magnetic material is the deposition of iron(III)oxide by reaction of ferrocene with ozone. Subsequent reduction in an argon-hydrogen atmosphere results in Fe3O4 magnetic tubes embedded in the Al2O3 membrane. Similar processes to obtain nickel and cobalt tubular structures are under investigation, as well [3].Removing the interconnects by reactive ion etching and releasing the tubes from the porous alumina matrix by chemical etching results in the formation of a ferrofluid-like suspension. The supporting aluminum substrate can then be recycled for use in subsequent anodizations. The viscosity of the resulting ‘nanotube ferrofluid’ has been studied as a function of the applied magnetic field and shear rate with a piezo-membrane axial vibrator. Compared to the spherical nanoparticles of conventional ferrofluids, ferromagnetic nanotubes impart a non-linear and stronger viscous response. A suppressed shear-thinning effect [4] is expected at higher shear rates.The authors thank the DFG (SPP 1165) for financial support.[1] J. Bachmann et. al., J. Am. Chem. Soc., 129, 9554 (2007). [2] J. Bachmann et. al., Angew. Chem. Int. Ed., 47, 6177 (2008). [3] M. Daub et. al., J. Appl. Phys., 101, 09J111 (2007). [4] S. Odenbach et. al., J. Magnet. Magnet. Mater., 183, 188 (1998).
9:00 PM - K5.77
Perfectly Ordered Arrays of Magnetic Nanotubes with Controlled Diameter Modulations.
Julien Bachmann 1 , Kristina Pitzschel 1 , Josep Montero Moreno 1 , Juan Escrig 2 , Detlef Goerlitz 1 , Kornelius Nielsch 1
1 Institute of Applied Physics, University of Hamburg, Hamburg Germany, 2 Departamento de Física, Universidad de Santiago de Chile, Santiago Chile
Show AbstractPorous anodic alumina furnishes an ideal template system for creating ordered arrays of one-dimensional magnetic nanostructures. Combining it with the electrodeposition of a metal yields wires; alternatively, atomic layer deposition (ALD) of an oxide can deliver tubes. In both cases, the geometric parameters (length, diameter, wall thickness) can be accurately controlled and systematically tuned — an ideal testing ground for the size-dependent properties of strongly anisotropic nanomagnets (Appl. Phys. Lett. 2001, 79, 1360-1362; J. Am. Chem. Soc. 2007, 129, 9554-9555; Phys. Rev. B 2008, 77, 214421; J. Appl. Phys. 2009, 105, 07B521).We want to move on beyond simple tubes and create more complex systems, in which additional geometric parameters can be utilized to control the properties of tubular systems.We are now able to introduce controlled modulations in diameter at arbitrarily selected points along the pores of anodic alumina templates. The shape of the nickel wires and of the iron oxide tubes obtained after electrodeposition and after ALD coating, respectively, reflects the silhouette of the alumina negative. Combining thick and thin segments in various ways affects the magnetic properties of the ensemble in a clearly non-linear manner. This is due in part to the enhanced stray field generated at the diameter changes. Moreover, the modulations can be utilized to control the motion of magnetic domain boundaries along the object: a domain boundary can thus be pinned at a well-defined position for physical investigations within an isolated object.With this, we have proven the possibility of preparing a magnetic data storage platform consisting of well-defined “vertical” memory elements (tubes), in which not only the individual properties of each element are adjustable via the parameters length and diameter, but also the interactions between neighboring elements, via the wall thickness and the diameter modulations. The system should prove useful both for applications and for first-principle studies of static and dynamic magnetic phenomena.
9:00 PM - K5.78
Fabrication of CNT Interconnection in Ultralarge-scale Integrated (ULSI) Circuit Using its Self-alignment Feature.
K. Sato 1 , T. Tanaka 1 , S. Ishikawa 1 , Yoshiyuki Show 1
1 Dept. of electrical and electronic engineering, Tokai University, Hiratsuka Japan
Show AbstractCarbon nanotube (CNT) is one of the candidate materials for the interconnection in an ultralarge-scale integrated (ULSI) circuit with 32nm technology node. Chemical vapor deposition (CVD) method is promising technique to fabricate the CNT interconnection, because it allows growing the CNT at selected area (via holes).In conventional formation process of the CNT interconnection, the CNTs are grown in via holes which are formed beforehand by the photolithography method. When via hole is small size and high aspect ratio, it is difficult to form dense CNT in it. In this study, we proposed the formation process of the CNT interconnection using self-alignment feature of the CNT. This process allows forming CNT interconnection with small size and high aspect ratio.The proposed fabrication process of the CNT interconnection is the below.(1) The Fe or Co catalyst film is selectively formed on the electrode of the device by the sputtering method and the conventional photolithography method before formation of the dielectric layer. (2) Bundles of multi wall type CNT are formed by the CVD method with the catalyst. In this study, the triode type radio frequency plasma CVD or the thermal CVD equipments were used for growing CNT. The CNT bundles were grown on the patterned catalyst existing on the electrode by its self-alignment feature. This CNT bundles work as the interconnections. On the other hand, there was no deposit such as amorphous carbon on the place where no catalyst was prepared in. Therefore, each CNT interconnections were electrically isolated. (3) The dielectric layer is formed around the CNT bundles by the CVD or sputtering method.In our proposed process, formations of the dielectric layer and the CNT interconnection are in reverse order comparing with the conventional process. Therefore, our process allows forming the CNT interconnections with small diameter and high aspect ratio, because the CNT bundles are grown on flat surface of the substrate. It is not necessary to form the CNTs in via holes with small size and high aspect ratio in this processIn this study, the CNT bondless, which were vertically aligned against the substrate, were formed by the above process. The diameter and the height of the CNT bundles were 20micro m and 40micro m, respectively. Each bundles consisted of the CNTs with the diameter of 20nm and high density of 1200 /micro m2.In this presentation, electrical properties of the CNT interconnection formed by the proposed process will be discussed.
9:00 PM - K5.79
Graphene/Single-walled Carbon Nanotubes/Graphene Interface as a Molecular Bearing.
K. Sato 1 , N. Arai 1 , K. Shintani 1
1 Department of Mechanical Engineering and Intelligent Systems, University of Electro-Communications, Chofu, Tokyo, Japan
Show AbstractNanoscale mechanical elements which can rotate or slide are essential parts of nano-electro-mechanical systems (NEMS). Rotational actuators based on multi-walled carbon nanotubes (MWNTs) were proposed by Fennimore et al. (Nature, 2004). Their actuator consists of a metal plate rotor and a MWNT which acts as a support shaft. Imposition of a voltage between the rotor and a gate stator generates a torque to rotate the rotor. If large voltages between the rotor and the stator were successively applied, the initially pristine MWNT was fatigued, and the rotor became free to rotate. Bourlon et al. (Nano Lett., 2004) fabricated a rotational actuator of a new layout. Their rotor attaches to an inner MWNT shell which can rotate around outer shells. The static friction against rotational sliding was estimated to be about 0.85MPa. Sasaki et al. (JJAP, 2007) investigated ultralow friction of a graphite/C60/graphite interface using molecular-dynamics (MD) simulation. They concluded the atomic-scale friction coefficient of the graphite/C60/graphite interface is about 30% of that of a graphite/graphite/graphite interface partly due to the three-dimensional degree of freedom of intercalated C60 motion. In light of the results of these researches, we get an idea that carbon nanotubes (CNTs) can play a role of rotators put between two plates for which graphene is a good candidate. In this paper, we investigate by MD simulation whether a graphene/single-walled carbon nanotubes (SWNTs)/graphene interface can be utilized as a molecular bearing. The interactions between the atoms in each of the graphene sheets or between those in each of the SWNTs are calculated using the Tersoff-Brenner potential, whereas the interactions between the atoms in each of the graphene sheets and those in the different SWNTs are calculated using the Lennard-Jones potential. One graphene sheet is forced to move within the plane of the sheet, and the friction coefficient is calculated. A graphene/SWNTs/graphen interface is expected to have a friction coefficient lower than that of a graphite/graphite/graphite interface and higher than that of a graphite/C60/graphite interface. According to Falvo et al. (PRB, 2000), the atomic lattices at the contact of CNTs and a graphite surface act like a gear mechanism; there are discrete orientations of the threefold symmetry in which the lateral force to rotate CNTs on the surface plane dramatically increases. They concluded the atomic lattices in these orientations are in commensurate contacts. Extending their results to our graphene/SWNTs/graphene system, we guess commensuration or incommensuration between the two graphene sheets and the SWNTs affects their friction coefficient. The combination of the atomic lattices at the contact of the two graphenes and CNTs for which the friction coefficient is smallest is searched. Once such a combination is found, the system will be suitable for its use as a molecular bearing or as a unidirectional conveyer.
9:00 PM - K5.8
Diameter-Tunable Aligned Carbon Nanotube Arrays on Quartz using Self-Assembled Fe Nanoparticles in Block Copolymers.
Ali Jazairy 1 , Joseph Payne 1 , Monica Lilly 1 , R. Clarke 1 , John Adam 1 , Hong Zhang 1
1 Electronic Systems, Northrop Grumman Corp., Linthicum, Maryland, United States
Show AbstractOne of the prerequisites for fabricating carbon nanotubes with predetermined, consistent and reproducible properties is the ability to create catalyst systems with controllable properties. We employ self-assembled morphologies created by catalyst-containing block copolymers to engineer nanocatalysts with controllable size and separation. Such a method provides precisely-controlled nucleation sites as compared to a traditional thin-film approach. We demonstrate for the first time high density aligned carbon nanotube growth on a quartz substrate using lithographically-patterned block copolymer-synthesized catalysts. The nanotubes have a narrow diameter range and these diameter bands are tunable by using PS-b-P4VP and SFES block copolymers. Atomic force microscopy on these aligned nanotubes reveals an extremely narrow diameter distribution. Diameter tunability can be achieved by using different types of block copolymers. Device design and process parameters can be varied to obtain a desired single-walled carbon nanotube density. In summary, the ability to control these process parameters is critical for high performance carbon nanotube field-effect transistors (CNT FETs).
9:00 PM - K5.80
Abrasion as Catalyst Deposition Technique for Growing Large Areas and Developing Patterns of Carbon Nanotube.
Noe Alvarez 1 4 , Cary Pint 2 4 , Robert Hauge 1 4 , James Tour 1 3 4
1 Chemistry, Rice University, Houston, Texas, United States, 4 The Richard E. Smalley Institute for Nanoscale Science and Technology, Rice University, Houston, Texas, United States, 2 Physics and Astronomy, Rice University, Houston, Texas, United States, 3 Mechanical Engineering and Material Science, Rice University, Houston, Texas, United States
Show AbstractMechanical abrasion of metal catalyst source such as stainless steel (SS) surfaces is demonstrated as an effective technique for the deposition of catalyst to support growth of vertical array - carbon nanotubes (VA-CNTs) in water-assisted catalytic chemical vapor deposition (CCVD). In all cases of Fe-containing materials abraded on Al2O3 substrates, CNT growth is observed, even though the 400 series of SS appears to deposit the most efficient catalyst. We demonstrate that this simple abrasion technique enables both micro- and nano-scale accuracy in catalyst patterning as well as large area catalyst deposition for uniform, dense CNT growth. Raman spectroscopy characterization indicates high quality CNTs grown in this method, comparable to CNT growth from traditional ultra-thin evaporated catalyst layers. This technique for CNT catalyst deposition presents an inexpensive, simple, and scalable route appealing to many of the growing number of CNT-based applications.
9:00 PM - K5.81
Alumoxanes Substrates for Large Scale Carbon Nanotube Production.
Noe Alvarez 1 4 , Christopher Hamilton 1 4 , Cary Pint 2 4 , Alvin Orbaek 1 4 , Jun Yao 2 4 , Andrew Barron 1 3 4 , James Tour 1 3 4 , Robert Hauge 1 4
1 Chemistry, Rice University, Houston, Texas, United States, 4 The Richard E. Smalley Institute for Nanoscale Science and Technology, Rice University, Houston, Texas, United States, 2 Physics and Astronomy, Rice University, Houston, Texas, United States, 3 Mechanical Engineering and Material Science, Rice University, Houston, Texas, United States
Show AbstractMass production of carbon nanotubes (CNTs) is required for many current applications. Vertical array (VA) of CNTs manufactured by chemical vapor deposition (CVD) has many advantages compared to other CNT production processes, however catalyst and catalyst-support deposition have limited CNT synthesis by CVD. We have developed thin films of alumoxane nanoparticles as catalyst-support through a simple spin coating process. Electron beam evaporated Fe and liquid phase premade Fe nanoparticles deposited on the alumoxane catalyst-support grow vertical arrays (VA) of CNTs of high quality compared to CNTs grown on standard evaporated alumina substrates. VA-CNT from premade Fe nanoparticles on alumoxanes is a complete liquid deposition process which makes CVD more competitive as a large-scale CNT production technique.
9:00 PM - K5.9
Novel Microheaters for Investigation of Nanostructure Growth.
Daniel Engstrom 1 2 , Mark Mann 2 , William Milne 2 , Peter Boggild 1
1 Department of Micro- and Nanotechnology, Technical University of Denmark, Lyngby Denmark, 2 Centre for Advanced Photonics and Electronics, Cambridge University, Cambridge United Kingdom
Show AbstractFollowing the interest in carbon nanotubes generated by the Iijima paper [1], a large number of new one-dimensional nanostructures have been synthesized. Crystalline nanowires made from group III-V and IV materials are often grown by chemical vapour deposition, where a precise control of temperature, gas composition, pressure, catalyst, and pre-treatments is essential. Each of these parameters must be optimized in order to obtain reproducible sizes and a high crystal quality which, due to the large parameter space, is a time consuming task. In this work we present the design and application of a microheater which enables in-situ growth of nanostructures at temperatures from 500 K to 1200 K in a single experiment. The heater automatically provides a temperature gradient, and thereby makes scanning over the temperature range very easy. In this way the optimal growth temperature is always found for a given process. The temperature of the micro heaters is controlled by passing a high current through a suspended silicon beam. Since the conductivity of the silicon beam depends on the temperature, simply measuring current as well as the voltage drop across the silicon beam allows us to calculate the conductivity and thereby the temperature. The silicon beam with its four connecting cantilevers is fabricated using standard photolithography. The temperature is measured in an area only a few micrometers wide and 12 micrometers long giving a temperature variation in the measurement area of less than 5 K at 1100 K. Outside the heated area and towards the base chip, the temperature drops to room temperature. COMSOL simulations indicate that it is possible to determine the temperature at any point from the heater to the base chip. To demonstrate the usefulness of the device we have, using the microheater, grown multiwalled carbon nanotubes and shown how their growth rate depends on the growth temperature without having to change the growth conditions.[1] Iijima S 1991 Nature 354 147
Symposium Organizers
Kenji Hata Advanced Industrial Science and Technology (AIST)
Annick Loiseau Laboratoire d'Etude des Microstructures
Yoke Khin Yap Michigan Technological University
Ming Zheng National Institute of Standards and Technology
K6: Controlled Synthesis of Graphene
Session Chairs
Tuesday AM, December 01, 2009
Room 302 (Hynes)
9:00 AM - **K6.1
Patterning of Chemically Converted Graphene, Carbon Nanotubes and Fullerenes for Nanoelectronic Applications.
Richard Kaner 1 2 3 , Jonathan Wassei 1 3 , Vincent Tung 2 3 , Matthew Allen 1 3 , Sergey Dubin 1 , Kitty Cha 2 3 , Yang Yang 2 3
1 Chemistry and Biochemistry, UCLA, Los Angeles, California, United States, 2 Material Science and Engineering, UCLA, Los Angeles, California, United States, 3 California NanoSystems Institute, UCLA, Los Angeles, California, United States
Show AbstractWe are exploring chemical routes to single layer graphene. These include the reduction of graphene oxide, and the intercalation and subsequent exfoliation of highly ordered pyrolytic graphite. Recently, we have developed routes to pattern chemically converted graphene (CCG), single walled carbon nanotubes and fullerenes by first dispersing them in hydrazine and then either using elastomeric lift-off membranes or using a modified micro-contact printing technique. In the first method, we use conventional photolithographic processes to fabricate polydimethylsiloxane (PDMS) lift-off membranes with defined features, which enables us to stencil carbon nanomaterials into the pores via spin- and dip-coating processes. In the second method, we utilize the low molecular weight oligomers on the surface of PDMS to create regions of hydrophobicity through surface contact. Once the substrate is prepared we can spin-coat our carbon solutions into defined locations. This provides a platform for the fabrication of nanoelectronic devices.
9:30 AM - **K6.2
NH3 Doping of Chemical Graphene Nanoribbons and Graphene Sheets.
Xiaolin Li 1 , Hailiang Wang 1 , Xinran Wang 1 , Hongjie Dai 1
1 , Stanford University, Stanford, California, United States
Show Abstract Graphene, with the remarkable physicochemical properties like the high electronic mobility (~105 cm2/V.S), large surface area (~2600 m2/g), and chemical stability, is promising for next generation of high-performance nanoelectronics and clean energy applications. The edge modification and chemical doping of graphene ribbons and sheets are important strategies to optimize their properties towards better performances in these applications. We developed a chemical route to produce graphene nanoribbons (GNR) with width from 10 to 50 nanometers. The GNRs exhibit ultra-smooth edges and the sub-10 nanometer GNRs produced are p-type field effect transistors (FET) due to the doping from adsorbates. For device applications, we access the n-doped individual graphene nanoribbons by covalently functionalizing nitrogen species through high-power electrical joule heating in ammonia gas, leading to n-type electronic doping consistent with theory. We fabricated an n-type graphene field-effect transistor that operates at room temperature. We developed a simple n-doping method for bulk amount of graphene oxide (GO) sheet materials through thermal annealing in NH3. 5% N doping was easily achieved at 500°C and the oxygen assisted doping mechanism was proposed based on the systematic XPS study of the chemical doping at different annealing temperatures. Electronic transport measurement of individual graphene sheet devices showed the resistivity dropping and Dirac point (DP) shifting to negative voltage with the temperature increasing. The n-doped graphene sheets could lead to future clean energy applications like supercapacitors and oxygen reduction catalysts in fuel cells.
10:00 AM - K6.3
Transport Gap in Chemically Derived Graphene.
Goki Eda 1 , Cecilia Mattevi 1 , Hisato Yamaguchi 1 , HoKwon Kim 1 , Manish Chhowalla 1
1 , Rutgers University, Piscataway, New Jersey, United States
Show AbstractThere has recently been growing interest in graphene oxide (GO) due to its unique physical properties and its potential as the precursor to bulk synthesis of graphene [1,2]. The properties of GO are uniquely characterized by the functional groups and disorder that are inherently introduced during synthesis. A recent report indicates that GO possesses a finite band gap whose size depends on the degree of oxygen coverage on the graphene sheet [3]. The chemical structure tuning in GO could therefore allow band gap engineering and open up pathways for electronic and photonic device applications.In this investigation, we study the transport properties of progressively reduced GO and demonstrate its gradual transition from insulator to semiconductor to graphene-like semimetal [4]. We observe a small transport gap in lightly reduced GO which allow distinct switching behavior with gate bias. We find that the apparent energy gap for transport is of the order of 10 ~ 50 meV and approaches the zero-gap condition of intrinsic graphene with extensive reduction. We show that the transport of carriers occurs via variable-range hopping between localized states. Analysis of the hopping parameters suggests that reduction leads to increased number of active hopping sites near the Fermi energy. The transport properties of reduced GO will be discussed in relation to its structural properties analyzed by Raman, photoluminscence, and X-ray photoemission spectroscopies and scanning transmission electron microscopy [5].[1] S. Park and R. Ruoff, Nature Nanotech. 4, 217 (2009).[2] G. Eda et al., Nature Nanotech. 3, 270 (2008).[3] D. W. Boukhvalov and M. I. Katsnelson, J. Am. Chem. Soc. 130, 10697 (2008).[4] G. Eda et al. < arXiv:0905.2799v1>[5] Mkhoyan et al. Nano Lett. 3,1058 (2009).
10:15 AM - K6.4
Single- and Few-layer Graphene Grown and Isolated from Ni Substrates.
Alfonso Reina 1 , Jakub Kedzierski 2 , Ki Kang Kim 1 , Stefan Thiele 3 , Gerardo Martinez 4 , Arturo Ponce 4 , Juergen Schaefer 3 , Mildred Dresselhaus 1 , Jing Kong 1
1 , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Lincoln Laboratory, Massachusetts Institute of Technology, Lexington, Massachusetts, United States, 3 Institut fur Physik and Institut fur Mikro- und Nanotechnologien, Technische Universitaet Ilmenau, Ilmenau Germany, 4 , Centro de Investigacion en Quimica Aplicada, Saltillo Mexico
Show AbstractGraphene based films, grown by ambient pressure chemical vapor deposition (CVD), are isolated from their growth substrate. The graphene films grow by surface precipiation of carbon from the bulk of a catalytic Ni substrate which forms a Ni-C solution during the CVD process. Here, we show that different graphene film morphologies and preferential coverage of single- and bi-layer graphene can be obtained during our growth process. These films are obtained by controlling both the process parameters and the properties of the Ni substrate utilized. Process parameters such as cooling rate of the Ni film and the amount of carbon stored inside the Ni film control the graphene film precipitation rate. The choice of the type of Ni substrate, such as bulk or thin film, and its structural properties, such as polycrystalline vs. single-crystalline Ni, also play an important role in the morphology of the final graphene film. TEM, Raman Spectroscopy and electrical characterization show that such tuning of the film properties may lead to differences in structural, electrical and optical properties of the synthesized graphene films.
10:30 AM - K6:CGrowth3
BREAK
K7: Electronic Properties and Application I
Session Chairs
Tuesday PM, December 01, 2009
Room 302 (Hynes)
11:00 AM - **K7.1
Individual Single/Double Walled Carbon Nanotube and its Electronic Properties.
Enge Wang 1
1 , Institute of Physics, Beijing China
Show AbstractOne-dimensional (1D) nanomaterials are believed to be fundamental components for the fabrication of novel devices in nanoscience and nanotechnology. Property measurements of single 1D nanomaterial, especially for a single-walled (SW) or double-walled (DW) carbon nanotube, are still a big challenge to the well-established conventional techniques due to their small size. We have developed an alternative novel approach that allows the direct property measurements of individual 1D nanomaterials inside high-resolution transmission electron microscopy (TEM). This talk will review our progress in using in situ TEM method to measure the chirality-resolved field electron emission and chirality-resolved transport property of individual SWNTs and DWNTs. First, we will introduce an efficient method to directly determine the chirality of carbon nanotubes based on electron diffraction by considering the relationship between the tilt-effect errors and the calculated chiral indices. Second, we will report the chirality-dependent field emission properties of individual SWNTs. It is found that the FN curves of metallic SWNTs appear linear shape, while the FN curves of semiconducting SWNTs bend up under high electrical field. Third, we will present the gate-dependent electrical transport measurements on the individual, chirality-resolved DWNTs by building the nanotube field-effect transistors (FETs) into TEM. The transistor characteristics of totally 82 DWNTs with identified chiral indices of both outer and inner shells were investigated, and the effect of the two-shell registry and intershell coupling on the transport behavior of different types of DWNTs has been carefully studied. The results help to shed light on the potential application of 1D nanomaterials in novel nanodevices.* In collaboration with Kaihui Liu, Zhi Xu, Wenlong Wang, and Xuedong Bai at IOP/CAS, Zhongfan Liu at Peking Univ., and Zhonglin Wang at GIT. The research was supported by CAS, NSF and MOST of China.
11:30 AM - **K7.2
Electrostatic Properties of Carbon Nanotubes and Carbon Nanotube Devices Using Scanning Force Techniques.
David Brunel 1 , Mariusz Zdrojek 1 , Zhao Wang 2 , Michel Devel 2 , Alexandre Mayer 3 , Thierry Melin 1
1 , IEMN-CNRS, Villenveuve d'Ascq France, 2 , Institut UTINAM, Besançon France, 3 , Laboratoire de Physique du Solide, Namur Belgium
Show AbstractIn this talk we will describe electrostaticforce microscopy experiments on individual single-walled and multiwalled carbon nanotubes(SWCNTs and MWCNTs), and carbon nanotube field effect transistors (CNTFETs).We show first that the charge states of individual SWCNTs and MWCNTs can bemeasured and manipulated using combined charge injection and electrostatic forcemicroscopy (EFM) experiments [1]. The imaging of charge emission patterns fromcarbon nanotubes will be described, and their enhancement at the nanotube capswill be investigated by EFM for SWCNTs, and compared quantitativelywith atomistic simulations using an atomic charge-dipole model [2].In a second part of the presentation, we will describe the magnitude of thelinear charge densities stored in carbon nanotubes – here in the range of a few10e to 100e/µm[3]. They are foundto differ from classical capacitive predictions by one order of magnitude. Thisbehaviour corresponds to a response of the nanotubes in the external electricfield generated at the microscope tip during the charge injection experiments,in agreement with atomistic simulations. The fact that MWCNTs can retain anout-of-equilibrium charge is attributed to their inner-shell charging, as aresult of their finite transverse polarizability and of the intercalation ofsemiconducting and metallic shells.The last part of the presentation will be devoted to results obtained onoperating CNTFETs, studied using Kelvin force microscopy (KFM) on CNTFETswith backgate geometry at room temperature. We show that KFM maps recorded as afunction of the device backgate polarization enable a complete phenomenologicaldetermination of the averaging effects associated with the KFM probe sidecapacitances, and thus, to obtain KFM measurements with quantitative character.The value of the electrostatic lever arm of the CNTFET can hence be determinedfrom KFM measurements, and are found in agreement with transport measurementsbased on Coulomb blockade. We finally investigate using combined transport,scanning probe techniques, and atomistic simulations, the fundamental operationmechanisms of CNTFET-based non-volatile memory devices, in a geometry thatintentionally separates the directions for (here, local) charge storage and forcharge detection. Operating devices show threshold voltage shifts opposite toconventional gating and almost unchanged hysteresis, in contrast with previouswork. The latter effect puts forward the dipolar nature of the hysteresis inCNTFETs. The former effect is quantitatively understood as the emission of adelocalized image charge pattern in the nanotube environment, in response tolocal charge storage [5].[1] M. Zdrojek et al., Appl. Phys. Lett. 86, 213114 (2005) ; J. Appl. Phys. 100, 114326 (2006).[2] Z. Wang et al. Phys. Rev. B 78, 085425 (2008).[3] M. Zdrojek et al. Phys Rev B 77 033404 (2008).[4] D. Brunel et al. Appl. Phys. Lett. 94, 223308 (2009).[5] D. Brunel et al., submitted (2009).
12:00 PM - K7.3
Single-Molecule Imaging of Electron-to-Fuel Conversion by Single-Walled Carbon Nanotubes.
Peng Chen 1
1 Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York, United States
Show AbstractCarbon nanotubes are promising materials for mediating chemical transformations in energy conversion. Understanding their reactivity is thus important, but hampered by their variable electronic properties from their dispersions in chirality. Measurements on individual nanotubes are therefore necessary, and multiplexed measurements with real time capability is highly desired. Here we report a single-molecule fluorescence approach that enables in-situ, multiplexed observation of electron-to-chemical conversion reactions catalyzed by single-walled carbon nanotubes (SWNTs). By imaging a fluorogenic catalytic reaction optically at single-reaction resolution with nanometer spatial precision, we find that the electrocatalytic processes occur at discrete, nanometer-dimension sites on SWNTs. Single-molecule kinetic analysis leads to an electrocatalytic mechanism, allowing quantification of the reactivity and heterogeneity of individual reactive sites. Electric-potential dependent interfacial electron transfer kinetics reveals distinct behaviors between metallic and semiconducting nanotubes. Combined with conductivity measurements, this approach will be powerful to interrogate how the electronic structure of SWNTs affects the electrocatalytic interfacial charge transfer, a process fundamental to photoelectrochemical cells.References: W. Xu, H. Shen, Y. J. Kim, X. Zhou, G. Liu, J. Park, P. Chen "Single-Molecule Electrocatalysis by Single-Walled Carbon Nanotubes" Nano Letters, 2009, doi:10.1021/nl900988f.
12:15 PM - K7.4
CNTFET Gas Sensors using SWCNT Mats : Method for Low-cost Fabrication, Solution to Improve Selectivity, Influence of Humidity (and Methods to Reduce it), Experimental Results Using Interfering Agents.
Paolo Bondavalli 1 , Pierre Legagneux 1 , Louis Gorintin 1 , Didier Pribat 2
1 NANOCARB, Thales Research and Technology, Palaiseau, Essonne, France, 2 LPICM, Ecole Polytechnique, Palaiseau, Essonne, France
Show AbstractThe first paper showing the great potentiality of Carbon Nanotubes Field Effect transistors (CNTFETs) for gas sensing applications was published in 2000 [1]. It has been demonstrated that the performances of this kind of sensors are extremely interesting : a sensitivity of around 100ppt (e.g. for NO2 [2]) has been achieved in 2003 and several techniques to improve selectivity have been tested with very promising results [2]. The main issues that have not allowed, up to now, these devices to strike more largely the market of sensors, have been the lack of an industrial method to obtain low-cost devices, a demonstration of their selectivity in relevant environments and finally a deeper study on the effect of humidity and the possible solutions to reduce it. This contribution deals with CNTFETs based sensors fabricated using air-brush technique deposition on large surfaces. Compared to our last contribution [3], we have optimized the air-brush technique in order to obtain high performances transistors (on/off ratio ~ 5) with highly reproducible characteristics : this is a key point for the industrial exploitation. We have developed a machine which allows us the dynamic deposition on heated substrates of the SWCNT solutions, improving dramatically the uniformity of the SWCNT mats. We have performed tests using different solvents that could be adapted as a function of the substrates (e.g. flexible substrates). Moreover these transistors have been achieved using different metal electrodes (patented approach [4]) in order to improve selectivity. Results of tests using NO2, CO, NH3 and Benzene with concentrations between 10ppb and 10ppm will be shown during the meeting. These tests have been performed all in ambient air using interfering agents (SO2, exhaustive fumes, humidity). Measurements after exposure to mixtures of the previous gases at different concentrations have been also performed and demonstrated the high selectivity also for very low concentrations. Finally, we have studied deeply the effect of humidity and the hysteresis of CNTFETs. In order to reduce this effect we have developed a new approach (to be patented) which permits to reduce dramatically the effect of water molecules on the dielectric layer. This approach takes into account that the gas/CNTFET interaction takes place only on the metal/CNT junctions. Measurements after gas exposure for different humidity concentrations, and after humidity effect reduction, will be shown.[1] J. Kong et al., Science 287 (2000), pp. 622-625[2] P.Bondavalli, et al., CNTFET based gas sensors : State of the art and critical review, Sensors and Actuators B, V.140, n1, 18, 2009, pp 304-318[3] P. Bondavalli et al, Preliminary Measurements of Selective sensing of DMMP and NH3 using CNTFET array. (MRS) Symp. Proc. vol. 1081, P14-02, 2008[4]P.Bondavalli et al Conductive nanotube or nanowire FET transistor network and corresponding electronic device, for detecting analytes., 2008 WO/2006/128828
12:30 PM - K7.5
High Field-Effect Carrier Mobility in Graphene Transistors with Buffered Dielectrics.
Damon Farmer 1 , Hsin-ying Chiu 1 , Yu-Ming Lin 1 , Fengnian Xia 1 , Phaedon Avouris 1
1 , IBM TJ Watson Research Center, Yorktown Heights, New York, United States
Show AbstractMuch of the interest surrounding graphene is due to the high carrier mobility that is exhibited by this material. High intrinsic mobilities in graphene lead to high field-effect mobilities (μFE) in graphene-based field-effect transistors (FETs). This makes graphene a material of great promise as the active element in electronic devices, particularly those based on high-frequency operation. One problem currently hindering the progress of graphene technology is the carrier scattering that has been shown to greatly limit mobility. A significant source of scattering is the detrimental interaction between graphene and the gate dielectric material, a necessary component in FET device architecture. The ability to minimize this degradation is paramount to realizing the full potential of graphene devices, and adequate gate dielectrics are needed to accomplish this. Here, we present a reliable dielectric stack that does not adversely affect μFE. This stack consists of a high-κ dielectric (HfO2, Al2O3, etc.) deposited by atomic layer deposition (ALD), and a buffer material that acts as a seed layer for ALD growth on the graphene surface. This buffer material satisfies the requirements necessary for high-performance graphene device fabrication: it completely coats the graphene surface, it does not damage the graphene surface, its processing can be implemented at low temperatures, it chemically reacts with ALD precursors, and it does not significantly degrade μFE. This last point deserves particular emphasis. Previous reports of high mobilities in coated graphene give intrinsic mobility values that are extracted from fitted data. In contrast, the high values of μFE that we report are directly measured from the output characteristics of graphene devices. The composition and properties of the buffer material are outlined, and possible mechanisms for the mobility preservation afforded by this material are discussed. Finally, device characteristics of high-frequency graphene transistors that utilize this buffered dielectric are presented.
12:45 PM - K7.6
Electrical Resistance of Single-Wall Carbon Nanotubes with Determined Chiral Indices.
Letian Lin 1 , Sean Washburn 2 1 , Lu-chang Qin 2 1 , Scott Paulson 3
1 Curriculum in Applied Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States, 2 Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States, 3 Department of Physics and Astronomy, James Madison University, Harrisonburg, Virginia, United States
Show AbstractThe properties of a carbon nanotube, in particular a single-wall carbon nanotube (SWNT), are highly sensitive to the atomic structure of the nanotube described by its chirality (chiral indices). We have grown isolated SWNTs on a silicon substrate using chemical vapor deposition (CVD) and patterned sub-micron probes using electron beam lithography. The SWNT was exposed by etching the underlying substrate for transmission electron imaging and diffraction studies. For each individual SWNT, its electrical resistance was measured by four-probe methods at room temperature and the chiral indices of the same SWNT were determined by nanobeam electron diffraction techniques. The contact resistances were reduced by annealing to typically 5~10% of the SWNT resistances. We have measured the I-V curve and determined the chiral indices of each nanotube individually from four SWNTs selected randomly – one is metallic and three are semiconducting. We will present the electrical resistances in correlation with the nanotube diameter as well as the band gap calculated from the determined chiral indices for semiconducting carbon nanotube. These experimental results will also be discussed in connection with the theoretical predictions.This work is supported by NSF-ECCS 0725759.
K8: Non-Carbon Nanostructures I
Session Chairs
Annick Loiseau
Yoke Khin Yap
Tuesday PM, December 01, 2009
Room 302 (Hynes)
2:30 PM - **K8.1
Band Gaps in Single Wall Carbon and Boron Nitride Nanotubes.
Francois Ducastelle 1 , Hong Lin 2 , Jerome Lagoute 2 , Perine Jaffrennou 1 2 , Sylvain Maine 3 , Brigitte Attal-Tretout 3 , Annick Loiseau 1
1 Laboratoire d’Etude des Microstructures, ONERA-CNRS, BP72, 92322 Chatillon Cedex France, 2 Laboratoire Matériaux et Phénomènes Quantiques, CNRS-Université Paris 7, 10 rue Alice Domon et Léonie Duquet, 75205 Paris Cedex 13 France, 3 Département de Mesures Physiques, ONERA, Chemin de la Hunièrere, 91761 Palaiseau Cedex France
Show AbstractThe band gaps of semiconducting single wall carbon nanotubes are known to depend on their diameter and helicity, and have been characterized in detail, using photoluminescence and Raman spectroscopy in particular. Excitonic effects are important however and complicate the analyses. Single particle properties are then very conveniently studied using scanning tunnel spectrocopy (STS) as shown elsewhere [1]. STS allows us also to image directly the wave functions at the Van Hove singularities of the semiconducting and metallic single wall nanotubes. We show, by extending earlier arguments [2], that the observed conductance images, including spectacular complementary effects when going from one singularity to the other, can be accounted for very accurately, using the simplest tight-binding model.Boron nitride nanotubes are the analogue of carbon nanotubes, being composed of rolled up hexagonal boron nitride (h-BN) sheets. Due to the ionic character of the BN bond, they are expected to have very different optical properties, with gaps in the far UV range, about 6 eV. Strong excitonic effects have also been predicted theoretically, and have been recently observed in h-BN as well as in multiwall nanotubes [3,4]. Combinations of cathodoluminescence, photoluminescence and excitation spectroscopies have provided us with a good semiquantitative description of the optical properties of these systems, which will be reviewed. Preliminary results of micro-photoluminescence on single wall BN nanotubes will also be presented.[1] L. Hong, J. Lagoute et al., this conference.[2] C. L. Kane and E. J. Mele, Phys. Rev. B59, 12759(1999).[3] P. Jaffrennou, F. Donatini, J. Barjon, J. S. Lauret, A. Maguer, B. Attal-Trétout, F. Ducastelle, and A. Loiseau, Chem. Phys. Lett. 442, 372 (2007).[4] P. Jaffrennou, J. Barjon, T. Schmid, L. Museur, A. Kanaev, J.-S. Lauret, C. Y. Zhi, C. Tang,Y. Bando, D. Golberg, B. Attal-Tretout, F. Ducastelle,1 and A. Loiseau, Phys. Rev. B77, 235422 (2008).
3:00 PM - K8.2
Narrowed Energy Bandgaps of Boron Nitride Nanotubes.
Ying Chen 1 , Dehong Yu 2 , Jun Yu 5 , Bing-ming Cheng 3 , Wenhui Duan 4
1 Institute for Technology Research and Innovation, Deakin University, Geelong, Victoria, Australia, 2 Bragg Institute, Australian Nuclear Science and Technology Organization, Sydney, New South Wales, Australia, 5 aResearch School of Physical Sciences and Engineering, Australian National University, Canberra, Australian Capital Territory, Australia, 3 , National Synchrotron Radiation Research Center, Hsinchu Taiwan, 4 Department of Physics, Tsinghua University, Beijing China
Show AbstractThe bandgap of boron nitride (BN) nanotubes is generally considered to be independent on radius and chirality of the tubes. However, we have observed that the bandgaps of BN nanotubes do depend on the tube diameters with photoluminescence excitation spectroscopy (PLE) using variable photon energies in the vacuum ultraviolet (VUV) range. With respect to the hBN bandgap, the energy bandgap of thin BN nanotubes (about 2.5 nm diameter) decreased by about 0.27 eV, and 0.13 eV reduction is measured for thick BN nanotubes (about 100 nm diameter). Red-shifted luminescent emissions were also observed in consistent with the narrowed bandgaps. The electron-hole interaction is claimed to be responsible for the observed bandgap narrowing in BN nanotubes.
3:15 PM - K8.3
Patterned Growth of Long and Clean Boron Nitride Nanotubes on Substrates.
Chee Huei Lee 1 , Ming Xie 1 , Vijaya Kayastha 1 , Jiesheng Wang 1 , Russell Cook 2 , Yoke Khin Yap 1
1 , Michigan Technological University, Houghton, Michigan, United States, 2 Electron Microscopy Center, Argonne National Laboratory, Argonne, Illinois, United States
Show AbstractThe chemistry involved and high temperature requirement make the synthesis of boron nitride nanotubes (BNNTs) challenging, compared to that of carbon nanotubes (CNTs). Both types of nanotubes form seamless tubular structure with strong sp2 bonded hexagonal network with extraordinary mechanical properties. Theoretically, BNNTs are having uniform electronic band gap of ~5.5 eV, which is insensitive to their diameter and chirality. In addition, BNNTs are good in thermal conductivity, chemically stable and resistive to oxidation up to 1000 °C. These properties make BNNTs attractive material for advanced applications.Here we report on the synthesis of BNNTs directly on substrates by chemical vapor deposition (CVD). In brief, B, MgO and other metal oxide are heated up to 1200 °C to produce B2O2 vapors. In NH3 environment, BNNTs will be grown on Si-based substrates that were patterned with catalyst films. Although we have reported on the patterned growth of BNNTs by plasma-assisted pulsed laser deposition [1], the growth rate of CVD BNNTs reported here is much higher. The typical diameter and length of the tubes are around 20-50 nm and >6 μm, respectively, as grown within an hour. In fact, this success has lead to the discovery of superhydrophopicity of BNNT films [2]. High resolution transmission electron microscopy (HRTEM) shows that these BNNTs are highly crystallized, without significant amorphous coatings on the side wall. Electron Energy Loss Spectroscopy (EELS) indicates that these are pure BNNTs. The lattice vibration of BNNTs is characterized by Fourier Transformed Infra-red (FTIR) and Raman spectroscopy. In FTIR spectra, we attribute the absorption at ~1545 cm-1 to the in-plane BN stretching along the tangential (T) axis of a nanotube. It is noted that this absorption was also predicted by theory, suggesting that this vibration could be the fingerprint for highly crystallized BNNTs. The band gap of these BNNTs is determined to be ~5.9 eV by UV-vis absorption spectroscopy [3]. Besides, the growth mechanism of BNNTs is proposed. This synthesis method is achieved by a growth vapor trapping approach inspired by the whisker nucleation theory. More importantly, using our simple setup, we have achieved for the first success of well-defined patterned growth of BNNTs at desired locations. We think that this technique is technologically important for future application of BNNTs. [1]. J. Wang et al, Nano Letters 5, 2528 (2005)[2]. C. H. Lee et al, Langmuir (Letter) 25, 4853 (2009) [3]. C. H. Lee et al, Nanotechnology 19, 455605 (2008)Yoke Khin Yap acknowledges support from the National Science Foundation (CAREER Award No. 0447555). This project is in part supported by the Department of Energy, the Office of Basic Energy Sciences (Grant No. DE-FG02-06ER46294), and the Electron Microscopy Center at Argonne National Laboratory (Project #080512-01A).
3:30 PM - K8: NoneC1
BREAK
K9: Novel Characterization
Session Chairs
Francois Ducastelle
Kenji Hata
Tuesday PM, December 01, 2009
Room 302 (Hynes)
4:00 PM - **K9.1
HR-TEM of Carbon Network, - Defects and Edge Structures of Low Dimensional Carbon.
Kazu Suenaga 1
1 , National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Japan
Show AbstractThe diversified properties of carbon nano-structures (nanotubes, fullerenesand their derivatives) are related to their polymorphic arrangement ofcarbon atoms. Therefore the direct observation of carbon network, such astopological defects or vacancies, is of great consequence in both scientificand technological viewpoints in order to predict the physical and chemicalproperties. Here we will show our recent progress in electron microscopy andits in situ investigations to visualize the various atomic defects in thelow-dimensional carbon nanostructures. The lip-lip interactions of the openedges of carbon nanotubes (1), the closed edges of heated graphenes (2), themono-vacancies in h-BN single sheet (3), the row-by-row removal of graphenenanoribbons (4) and the spectroscopy of single dopants (5) will bedemonstrated.(1) C. Jin, H. Lan, K. Suenaga, L.-M. Peng and S. Iijima, Phys. Rev. Lett.,(2008) 101 (2008) 176102(2) Z. Liu, K. Suenaga, P. Harris and S. Iijima, Phys. Rev. Lett., 102(2009) 015501(3) C. Jin, F. Lin, K. Suenaga and S. Iijima, Phys. Rev. Lett., 102 (2009)195505(4) C. Jin, H. Lan, L. Peng, K. Suenaga and S. Iijima, Phys. Rev. Lett., 102(2009) 205501(5) K. Suenaga, Y. Sato, Z. Liu, H. Kataura, T. Okazaki, K. Kimoto, H.Sawada, T. Sasaki, K. Omoto, T. Tomita, T. Kaneyama and Y. Kondo NatureChemistry (in print)
4:30 PM - K9.2
In-Situ Observation of Graphene Sublimation and Multi-Layer Edge Reconstructions.
Jianyu Huang 1 , Feng Ding 2 4 , Boris Yakobson 2 , Ping Lu 1 , Liang Qi 3 , Ju Li 3
1 1132, CINT, Sandia National Laboratories, Albuquerque, New Mexico, United States, 2 , Rice University, Houston, Texas, United States, 4 , Hong Kong Polytechnic University, Hong Kong China, 3 , University of Pennsylvania, Philadelphia, Pennsylvania, United States
Show AbstractWe induced sublimation of suspended few-layer graphene by in-situ Joule-heating inside a transmission electron microscope. The graphene sublimation fronts consisted of mostly {1100} zigzag edges. Under appropriate conditions, a fractal-like “coastline” morphology was observed. Extensive multiple-layer reconstructions at the graphene edges led to the formation of unique carbon nanostructures, such as sp2-bonded bilayer edges (BLEs) and nanotubes connected to BLEs. Flat fullerenes/nanopods and nanotubes tunneling multiple layers of graphene sheets were also observed. Remarkably, more than 99% of the graphene edges observed during sublimation are BLEs rather than monolayer edges (MLEs), indicating that BLEs are the stable edges in graphene at high temperatures. We reproduced the “coastline” sublimation morphologies by kinetic Monte Carlo (kMC) simulations. The simulation revealed geometrical and topological features unique to quasi 2-dimensional (2D) graphene sublimation and reconstructions. These reconstructions were enabled by bending, which cannot occur in first-order phase transformations of 3D bulk materials. These results indicate that substrate of multiple-layer graphene can offer unique opportunities for tailoring carbon-based nanostructures and engineering novel nano-devices with complex topologies. (J.Y. Huang et al., PNAS, doi_10.1073_pnas.0905193106)
4:45 PM - K9.3
Electron Counting Spectroscopy based on Carbon Nanotube Field Effect Transistor.
Mariusz Zdrojek 1 , Maria Esplandiu 1 , Amelia Barreiro 1 , Adrian Bachtold 1
1 , CIN2(CSIC-ICN), Bellaterra, Spain
Show AbstractA new technique, electron counting spectroscopy has been used to probe the electronic properties of semiconducting CdSe quantum dots [1]. This technique allows us to fill or empty a semiconducting quantum dot with many electrons. The ability to shift the Fermi energy by a large amount holds promise for nanoscale or molecular electronics, since the large energy separation between the levels often has limited access to only few levels.The detection scheme is based on an original approach where the investigated particle is attached to only one electrode, a carbon nanotube. The conductance of the nanotube is measured as a function of a gate voltage (Vg), which allows the detection of individual electrons transferred onto the quantum dot. The electron transfer occurs only when the electrochemical potential of the nanotube matches the energy levels in the particle, while sweeping the gate voltage. We noticed no electron transfer for certain range of Vg which is attributed to the energy gap of the CdSe quantum dot. Our study shows that single-electron detection with CNT transistor represents a new strategy to study the separation in energy between the electronic discrete levels (Eadd) of the semiconducting quantum dot. In particular, it allows the study of the chaotic behavior of the electronic levels in the CdSe particle [1]. Additionally, we show that electron counting spectroscopy can be employed to investigate other type of quantum dots, e.g. gold nanoparticles and ferritin molecules (iron core protein).References:[1] M. Zdrojek, M. J. Esplandiu, A. Barreiro and A. Bachtold, Phys. Rev. Lett., 102, 228604 (2009)
5:00 PM - K9.4
Environmental Sensitivity of the Luminescence Emitted by Individual Single-Walled Carbon Nanotubes.
Laurent Cognet 1 , Juan Duque 1 2 , Stephane Berciaud 1 , Dmitri Tsyboulski 3 , R. Bruce Weisman 3 , Matteo Pasquali 2 , Brahim Lounis 1
1 CPMOH, Universite de Bordeaux & CNRS, Bordeaux France, 2 Department of Chemical and Biomolecular Engineering , Rice University, Houston, Texas, United States, 3 Department of Chemistry, Rice University, Houston, Texas, United States
Show AbstractCurrent methods for producing single-walled carbon nanotubes (SWNTs) lead to heterogeneous samples containing mixtures of metallic and semiconducting species with a variety of lengths and defects. Optical detection at the single nanotube level offers the possibility to examine these heterogeneities. The luminescence properties of semiconducting SWNTs are highly sensitive to the nanotubes environment. For instance, single-molecule chemical reactions with individual SDBS wrapped nanotubes could be observed through the stepwise changes of the luminescence intensity within submicrometer segments of nanotubes [1]. Analysis of the step amplitudes revealed an exciton diffusion range of ~90 nm. Each exciton thus visits approximately 10^4 atomic sites during its lifetime, providing highly efficient sensing of local chemical and physical perturbations. Mapping of the single-molecule chemical reaction sites further enables sub-wavelength (< lambda/10) localization of excitonic luminescence regions along the nanotube axis through a far-field optical measurement. This super-resolution method can reveal sub-diffraction lengths, curvatures, and defects of luminescent SWNTs in unprecedented details [2]. In addition to luminescence intensities and spectral widths, we observed that luminescence decays of single nanotubes are also sensitive to synthesis or environmental effects (surfactants, surfaces etc…)[3]. Such results suggest that by affecting the exciton lifetimes environmental effects should also affect the exciton excursion range. For many applications however, such as bioimaging, luminescent SWNTs which are weakly sensitive to their environment would also be beneficial. Toward this aim, we show that by combining surfactant and polymer wrapping around the nanotubes, luminescence is insensitive to pH or salinity, allowing single nanotube detection on live cells [4].[1] Cognet, et al Science (2007)[2] Cognet, et al Nanolett (2008)[3] Berciaud et al, Phys. Rev. Lett. (2008), Duque et al, submitted (2009)[4] Duque et al, JACS (2008)
5:15 PM - K9.5
A Light Touch on Nanotubes: Femtonewton Force Sensing and Nanometric Spatial Resolution.
Onofrio Marago 1 , Francesco Bonaccorso 2 , Pietro Gucciardi 1 , Maria Antonia Iati 1 , Giuseppe Calogero 1 , Philip Jones 3 , Rosalba Saija 4 , Ferdinando Borghese 4 , Paolo Denti 4 , Andrea Ferrari 2
1 , CNR-Istituto Processi Chimico-Fisici (Messina), Faro Superiore - Messina Italy, 2 Electrical Engineering Division, University of Cambridge, Cambridge United Kingdom, 3 Department of Physics and Astronomy, University College London, London United Kingdom, 4 Dipartimento di Fisica della Materia e Ingegneria Elettronica, Università di Messina, Messina Italy
Show AbstractLight can exert a mechanical action on matter. Although this simple concept has been known for centuries, the advent of the laser age has led to tremendous experimental advances and understanding of this phenomenon. Optical tweezers, instruments based on a tightly focussed laser beam, have been used to trap, manipulate, control and assemble dielectric particles, single atoms, cells, metal and semiconduncting nanostructures, leading to a real optical revolution in Physics, Biology and Nanotechnology [1]. Recently optical trapping of one-dimensional nanostructures has received much attention due to its potential for top-down organization of complex nano-assemblies and increased space and force resolution in photonic force microscopy [2-5]. Their small transverse size is the key to achieve nanometric resolution, while an axial dimension in the micron range ensures stable trapping and allows force sensing in the femtonewton regime. Here we extract the distribution of both centre-of-mass and angular fluctuations from three-dimensional tracking of optically trapped nanotubes [2]. We measure the optical force and torque constants from auto and cross-correlation of the tracking signals. This allows us to isolate the angular Brownian motion [2]. We demonstrate that nanotubes enable nanometre spatial, and femto-Newton force resolution in photonic force microscopy [2,5]. The integration of optical trapping and Raman spectroscopy (Raman Tweezers) and Photoluminescence spectroscopy of nanotubes will be also discussed. Finally, we will show the first demonstration of optical trapping of graphene in solution [6].[1] A. Ashkin, Optical Trapping and Manipulation of Neutral Particles using Lasers, (World Scientific, Singapore, 2007).[2] O.M. Maragò et al. Nano Lett. 8, 3211 (2008).[3] F. Borghese et al. Phys. Rev. Lett. 100, 163903 (2008).[4] Y. Nakayama et al., Nature 447, 1098 (2007).[5] E.L. Florin et al. J. Struct. Biol. 119, 202 (1997).[6] O.M. Maragò et al. Submitted (2009).
5:30 PM - K9.6
The Fastest High Definition Raman Imaging of Carbon Nanotubes Bridged Between Electrodes.
Tomoya Uchiyama 1 , Taisuke Ota 1 , Minoru Kobayashi 1 , Masamichi Yoshimura 2
1 , Nanophoton corporation, Suita, Osaka Japan, 2 , Toyota Technological institute, Nagoya, Aichi Japan
Show AbstractThe Raman spectrum of carbon nanotube (CNT) contains a wealth of information such as the radial breathing modes (RBMs) which reflect the chirality of each CNTs, G- and G+-band which is used to distinguish between metallic or semiconducting CNTs and D-band which reflects the defects of CNTs. The conventional Raman instruments detect an extremely weak Raman signal from one point on the sample, and as a result, it takes huge time to construct high-definition Raman spectral images. For example, to obtain a Raman image of 256 by 256 pixels, it takes more than 1000 minutes or 18 hours if it takes 1 second for 1 Raman spectrum. The innovative technology which enables the high speed Raman imaging has been needed to meet the needs of CNTs distribution imaging.We developed a new laser Raman microscope by combining the line illumination and multi-spectrum simultaneous measurement. By using this method, the incident laser can excite the Raman scattering from the sample surface along the line illuminated area and measure it as 400 Raman scattered lights while each light is dispersed spectrally by 1340-400 pixels electrically cooled CCD detector. Additionally, our Raman microscope scans the line-shaped laser by laser beam scanning method and realizes high-speed and vibration-free imaging compared to the stage scanning method. We developed original optics (patented) to avoid a non-uniform intensity illumination along the line caused by the cylindrical lens (conventional line illumination method). Also, we adopted slit confocal optics to keep the three-dimensional spatial resolution when we use line illumination. By these means, we succeeded in speeding up the Raman imaging speed about several hundred times faster than that of conventional method while keeping the high definition imaging performance.CNTs distribution between electrodes is previously imaged by using scanning electron microscope, however it cannot tell us about the property of CNTs. We observed the distribution of CNTs bridged between electrodes by our Raman microscope and obtained the high definition Raman image at diffraction-limited resolution of 532nm excitation laser in only 8 minutes. The Raman image reveals not only the distribution of CNTs bridged between electrodes but also the distribution of CNTs which have a different RBM peak with high SN ratio.
5:45 PM - K9.7
Changes in Raman Resonance Profiles within (2n+m) Families of Semiconducting and Metallic Single-wall Carbon Nanotubes.
Mario Hofmann 1 , Ya-ping Hsieh 1 2 , Jing Kong 1 , Mildred Dresselhaus 3
1 Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Department of Physic, National Taiwan University, Taipei Taiwan, 3 Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractRaman spectra on isolated single wall carbon nanotubes (SWNTs) were obtained for a wide range of laser excitation energies to study the resonance window of the Raman RBM feature for members of (2n+m) families. A chiral angle dependence of the resonance window width was observed that is much stronger than the influence of the nanotube diameter on the width. A strong correlation of this behavior with the chiral angle dependent Raman D-band intensity was observed. Our analysis shows that defect scattering is an important source of electron relaxation and has to be taken into account in future theoretical modeling. These findings will enable a more accurate characterization of the nanotube chirality distribution of a sample from Raman spectra obtained at a limited number of laser excitation energies.
K10: Poster Session: Theory and Characterization of Nanotubes and Related Nanostructures
Session Chairs
Kenji Hata
Annick Loiseau
Wednesday AM, December 02, 2009
Exhibit Hall D (Hynes)
9:00 PM - K10.1
Development of Steady-State Electro-Raman-Thermal Technique for Micro/Nanoscale Thermal Characterization.
Yanan Yue 1 , Xinwei Wang 1 , Liying Guo 1 , Gyula Eres 2
1 Mechanical Engineering, Iowa State University, Ames, Iowa, United States, 2 , Oak Ridge National Lab, Oak Ridge, Tennessee, United States
Show AbstractIn this work, a new technology: steady-state electro-Raman-thermal (SERT) technique is developed to directly measure the thermal conductivity of micro/nanoscale wires. In this technique, the relationship between temperature and normalized Raman shift intensity in Raman spectrum is established in calibration experiment. To determine the thermal conductivity, several spectrums are recorded to measure the temperatures at the middle of the sample under different steady-state electrical heating rates in a vacuum chamber. The thermal conductivity is directly obtained from the slope of linear fitting of temperature against the heating power. Combined with our transient electro-thermal technique, we also pioneer the work to measure the density of the micro/nanoscale wires. Multiwall carbon nanotube bundles are measured in detail using the SERT technique to varify its accuracy.
9:00 PM - K10.10
Double-walled Carbon Nanotubes Under High Hydrostatic Pressure: Raman Study.
Alexander Soldatov 1 4 , Ilya Dobryden 1 , David Olevik 1 , Yoshihiro Iwasa 2 , Hiromichi Kataura 3
1 , Lulea University of Technology, Lulea Sweden, 4 Department of Physics, Harvard University, Cambridge, Massachusetts, United States, 2 Institute for Materials Research, Tohoku University, Aoba-ku Japan, 3 , National Institute of Advanced Industrial Science and Technology, Tsukuba Japan
Show AbstractSince the development of high-yield synthesis of double-walled carbon nanotubes (DWCNTs), interest in this system has been increasing due to the superior properties of double- compared to single- and multi-walled nanotubes. In this study we use hydrostatic high pressure to probe structural stability and tune vibrational and electronic properties of bundled and individual DWCNTs. Raman data demonstrate DWCNT stability up to 10 GPa, the highest hydrostatic pressure in our experiment. The RBM pressure derivatives, dw/dP, of the outer tubes are several times larger than those of the inner tubes - the former act as a protective shield for the latter upon pressure application while the inner tubes provide the structural stability to the outer ones [1,2]. We probed the response of the metallic outer tubes to high pressure and observed a gradual decrease of the FWHM of G-(BWF) component on pressure increase, indicating weakening of the electron phonon coupling. In addition, we observed anomalous behavior of G- and RBM mode frequencies above 4-5 GPa. Possible origins of this anomaly are discussed. Finally, we compare the response of individual and bundled DWCNTs to the external hydrostatic high pressure.
9:00 PM - K10.13
AFM Characterization of Carbon Nanotube FETs Fabricated by Dielectrophoresis Method Using Density Gradient Ultracentrifugation Process.
Yuji Miyato 1 , Kei Kobayashi 2 , Kazumi Matsushige 1 , Hirofumi Yamada 1
1 Department of Electronic Science and Engineering, Kyoto University, Kyoto Japan, 2 Innovative Collaboration Center, Kyoto University, Kyoto Japan
Show AbstractCarbon nanotube field effect transistors (CN-FETs) using single wall carbon nanotubes (SWNTs) have been intensively studied for building blocks in nanoelectronics. It is essentially important to fabricate the CN-FETs with small variations in their electrical characteristics for practical applications. However, it is difficult to synthesize a specific type/chirality of SWNTs so far. Recently Arnold et al. successfully separated metallic and semiconducting SWNTs by density gradient ultracentrifugation (DGU) technique [1]. This technique may enable us to fabricate electrically uniform CN-FETs. On the other hand, The CN-FET characteristics, which strongly depend on the electronic state of the SWNT itself, are also affected by the potential barriers at contact interfaces or by some defects in the channel. Since thorough understanding of their electronic states is required, the development of a method for measuring the local electronic states on a nanometer scale is indispensable. In this study, we separated the isolated SWNTs with a specific chirality by DGU and fabricated CN-FETs using these SWNTs by dielectrophoresis method. Local electrical characteristics of the CN-FETs were investigated by AFM-based electrical measurement methods.We first dispersed SWNTs (CoMoCAT) with surfactant DOC and took the supernatant after centrifugation to remove the bundles. The mixture of the supernatant and iodixanol solution with additional surfactants (SDS, SC and DOC) was inserted into the density gradient formed by layered iodixanol solutions with different concentration. Then, we centrifuged it at 60,000 G (DGU process) and collected fractions. We successfully obtained the solution enriched with the (6, 5) nanotube. The diluted solution was deposited onto pairs of palladium electrodes with a gap distance of 300 nm, fabricated on a highly doped Si substrate with a 100 nm silicon oxide film. The positions of SWNTs were controlled using the dielectrophoresis method. Finally, we obtained the CN-FETs. The surface potentials of the channel of the CN-FET were mapped by a newly developed AFM potentiometry using the point-by-point contact method (point-by-point AFMP), in which tapping mode and contact mode are alternately used at each pixel position for nondestructive topographic measurement and accurate potential measurements, respectively [2]. We also investigated the CN-FETs by scanning gate microscopy (SGM), which is capable of visualizing local potential barriers at defects or at Schottky contacts. For the improvement of the spatial resolution in SGM, the point-by-point contact technique, used in AFMP, was applied to the SGM measurement (P-SGM).[1] M. Arnold et al., Nat. Nanotechnol. 1, 60 (2006). [2] Y. Miyato,et al., Nanotechnol. 18, 084008 (2007).
9:00 PM - K10.14
Gradient Morphology Relationship of Functionalized Nanotube Nanocomposites by EELS.
Sabyasachi Ganguli 1
1 RXBT, AFRL/UDRI, Dayton, Ohio, United States
Show AbstractIn this study we establish a relationship between the plasmon energy and the physical properties specifically bulk modulus, electrical conductivity and thermal conductivity of various carbon fibers and thermoplastics having a wide range of stiffness. The objective of this research is to develop a enabling tool to readily predict the physical properties of materials based on the measured plasmon energies. Based on the developed correlation between the plasmon energy and the mechanical property, a gradient morphology relationship of amine and carboxylic functionalized carbon nanotube nanocomposite was examined and is reported. Based on this technique properties of nanocomposites could be quickly determined at the nanoscale.
9:00 PM - K10.15
Polyoctenamer - Single Walled Carbon Nanotube Composites: Spectroscopic Investigations.
Alin Cristian Chipara 2 , Rafael Villegas 2 , Karen Lozano 2 , Magdalena Dorina Chipara 1 , Steven Tidrow 1 , Mircea Chipara 1
2 Mechanical Engineering, The University of Texas Pan American, Edinburg, Texas, United States, 1 Physics and Geology, University of Texas Pan American, Edinburg, Texas, United States
Show AbstractPolymeric materials such as polyoctenamer are characterized by an excellent shock resistance and reduced weight. The addition of nanometer-sized fillers increases the strength of polymeric materials and in most cases result in a decrease of the elongation at break. However, in certain circumstances an increase of both mechanical toughness and elongation at break has been reported.Among the most frequently used nanofillers, carbon nanotubes are characterized by a huge aspect ratio, excellent mechanical strength (large high modulus), large thermal conductivity, and electrical features ranging from semiconductor to metal (pending on the chirality of the nanotubes). The research aims at a better understanding of the interactions between carbon nanotubes and macromolecular chains, by using Raman spectroscopy. In order to fully exploit the capabilities of Raman spectroscopy the research has been concentrated on single walled carbon nanotubes (SWNT) dispersed within polyoctenamer (vestanamer; PO), obtained by extrusion at 150 oC, for about one hour. Recent studies indicated that the dispersion of nanometer-sized fillers such as carbon nanotubes and carbon nanofibers enhances the mechanical properties, the thermal and thermo-oxidative stability , improves the thermal conductivity, and eventually adds electrical conducting features to polymeric matrices.A detailed investigation on the effect of SWNT on the Raman spectra of PO is reported. The experimental spectra have been obtained by using a Bruker Senterra micro Raman spectrometer operating at 785 nm. The laser power was kept at 1 mW, in order to avoid the thermal destruction of samples. Composites containing various amounts of SWNT ranging from 0 % wt. up to 15 % wt have been investigated. The attention has been focused on the breathing modes, D line and G line. However, an exhaustive analysis of the Raman spectra that included the successful computer simulation of the whole Raman spectrum for each sample has been done. The Raman components were fitted by a Breit-Wigner lineshape.The dependence of the Raman line position, amplitude, width, and asymmetry on the concentration of SWNT has been investigated in detail, with emphasis on information pertinent to the stress transfer from the macromolecular matrix to the filler (SWNTs).Additional data have been obtained by Wide Angle X-Ray Spectroscopy using a Bruker Discovery 8 equipment. These spectroscopic data will be complemented by Differential Scanning Calorimetry investigations on the same samples. The research aims for a better understanding of the interactions between polymeric matrices and nanofillers and of crystallization processes in nanocomposites.
9:00 PM - K10.16
The Influence of the Resonant Electronic Transition on the Intensity of the Raman Radial Breathing Mode of Single Walled Carbon Nanotubes During Electrochemical Charging.
Martin Kalbac 1 , Ladislav Kavan 1
1 , J. Heyrovsky Institute of Physical Chemistry, Prague Czechia
Show AbstractIn situ Raman spectroelectrochemistry has been used to probe the E11S and E22S electronic transitions of the semiconducting single walled carbon nanotube tube (6,5). These two transitions were investigated through the intensities of the radial breathing mode using 1.16 and 2.18 eV laser excitation energies, respectively. The bleaching behavior of the (6,5) tube is similar for both laser excitation energies if the magnitude of the applied electrode potential is smaller than about ±0.5 V. At potentials outside the ±0.5 V window, the intensity/potential profile is steeper for the 1.16 eV laser excitation. But a significant bleaching of the Raman signal is observed also for the 2.18 eV laser excitation energy even at mild potentials. This behavior shows that the filling of the E11S electronic state has a strong impact also on the E22S electronic transition. Hence, we suggest that a broadening of the resonance profile of E22S is a major reason for the change of the resonance enhancement of the Raman spectra before the Fermi level reaches the energy of E22S transition.
9:00 PM - K10.17
Environmental and Synthesis Dependent Luminescence Properties of Individual Single-Walled Carbon Nanotubes.
Juan Duque 1 2 3 , Howard Schmidt 1 , Matteo Pasquali 1 , Stephen Doorn 2 , Laurent Cognet 3 , Brahim Lounis 3
1 Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas, United States, 2 Physical Chemistry and Applied Spectroscopy , Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 3 Centre de Physique Moléculaire Optique et Hertzienne, Université de Bordeaux and CNRS, Bordeaux, Bordeaux, France
Show AbstractMultiple studies have shown that the optical properties of single-walled carbon nanotubes (SWNTs) are excitonic in nature.[1-3] However, a complete understanding of how these excitonic states shape the optical properties of SWNTs is lacking. Comparing the results of different published studies is difficu< the luminescence properties of SWNTs are affected by various extrinsic factors originating from synthesis and processing methods which affect the structure, sidewall quality, and environment of SWNTs. Fundamental and applied reports are hindered by poor control over the synthesis and post-processing methods. This is highlighted by the range of reported fluorescence quantum yields and luminescence lifetimes measured from ensembles or single SWNTs – they range between 10-4 to 7 %[4-8] and from 5 to 200 ps,5,[8-10] respectively, depending on the report. Here we identify different extrinsic factors which deeply influence the intrinsic SWNT luminescence properties including synthesis methods (HiPco, CoMoCat), suspension agents, and local environment.[11,12] Single molecule imaging and time resolved spectroscopy of individual (6,5) SWNTs showed that SWNT luminescence depends strongly on intrinsic and extrinsic factors such as sample preparation, sample inhomogeneities, sidewall defects, and tube synthesis conditions (HiPco or CoMoCat).[11] Ensemble measurements showed compelling spectroscopic evidence of substantial differences in chirality distribution and luminescence properties within different HiPco batches.12 These findings underline the necessity for more standard production and post-processing procedures such that correlations between different reports in the literature can be drawn, and we begin to understand the complex excitonic structure of SWNTs.References 1.Wang, F.; et. al Science 2005, 308, (5723), 838.2.Perebeinos, et. al. PRL 2004, 92, (25 I), 257402.3.Shaver, J.; et.al. Nano Lett. 2007, 7, (7), 1851.4.O'Connell, M. J.; et.al. Science 2002, 297, (5581), 593.5.Wang, F.; et.al. Nano Lett. 2007, 7, (12), 3698-3703.7.Tsyboulski, D. A.; et.al. Nano Lett. 2007, 7, (10), 3080.8.Berciaud, S.; et.al. PRL 2008, 101, (7), 077402.9.Jones, M.; et.al. Phys. Rev. B 2005, 71, 115426.10.Hirori, H.; et.al. PRL 2006, 97, (25), 257401.11.Duque, J. G.; et.al. Nano Lett.; Submitted12.Duque, J. G.; et.al. In Preparatio
9:00 PM - K10.18
Torsion in Chiral Carbon Nanotubes.
Eduardo Barros 1 , Daniel Vercosa 1 , Antonio Souza Filho 1 , Josue Mendes Filho 1 , Georgy Samsonidze 2 , Riichiro Saito 3 , Mildred Dresselhaus 4
1 Department of Physics, Universidade Federal do Ceará, Fortaleza, Ceará, Brazil, 2 Department of Physics, University of California at Berkeley, Berkeley, California, United States, 3 Department of Physics, Tohoku University, Sendai, Miyagi, Japan, 4 Department of Electrical Engineering and Computer Science and Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractSeveral theoretical and experimental studies indicate that the electronic and optical properties of carbon nanotubes are extremely sensitive to structural deformations such as axial, radial or torsional strains.[1-4] This work investigates the structural and electronic properties of torsioned single-wall carbon nanotubes. The electronic struture of torsioned nanotubes are calculated using an extended tight-binding model [5,6] and the structural properties are found by relaxing the carbon nanotube struture to find the lowest energy. Small diameter chiral carbon nanotubes are shown to have a natural torsion originating from the symmetry breaking due to chirality effects. The dependence of the natural torsion on the chiral angle is found to be different for metallic and semiconducting nanotubes, especially for near-armchair nanotubes, for which the behavior of semiconducting nanotubes deviates from the simple sin(6θ) behavior observed for metallic nanotubes. Since this natural torsion changes the electronic transition energies, a new kataura plot is calculated which should be able to describe more precisely the Raman and Photoluminescence experiments on small diameter nanotubes. The effects of decreasing or further increasing the nanotube torsion on their electronic and optical properties are also studied. The calculated predictions are discussed in comparison to experimental results. [1]L. Yang and J. Han, Phys. Rev. Lett. 85, 154 (2000).[2]R. B. Capaz et al., Phys. Status Solidi B 241, 3352 (2004).[3]S. B. Cronin et al., Phys. Rev. Lett. 93, 167401 (2004).[4]M. Lucas and R. J. Young, Phys. Rev. B 69, 085405 (2004).[5]G. G. Samsonidze, et al. Appl. Phys. Lett. 85, 5703 (2004).[6]D. Porezag, et al. Phys. Rev. B 51, 12947 (1995).
9:00 PM - K10.19
Modulation of Single-Walled Carbon Nanotube Photoluminescence by Hydrogel Swelling.
Paul Barone 1 , Hyeonseok Yoon 1 , Rene Ortiz-Garcia 1 , Jingqing Zhang 1 , Jin-Ho Ahn 1 , Jong-Ho Kim 1 , Michael Strano 1
1 Chemical Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractHydrogels are an important class of materials for interfacing biomedical devices to living tissues due to their resistance to protein fouling and favorable mechanical properties. We demonstrate, for the first time, the use of hydrogel swelling as a mechanism to reversibly induce solvatochromic shifting in single-walled carbon nanotube (SWNT) near-infrared emission within a biocompatible hydrogel. Photoluminescence emission maxima from dispersed nanotubes in a poly(vinyl alcohol) hydrogel shift as cross-linking is increased, with a maximum of -50 meV for the (6,5) nanotube. The Raman tangential mode also red-shifts up to 17 cm-1, indicative of nanotube lattice strain equivalent to an effective hydrostatic pressure of 3 GPa. While the electronic band gaps of SWNT are known to either increase or decrease with uniaxial strain or lattice deformation depending on chiral vector, we show that the mechanism of detection is counter-intuitively non-strain dependant. Instead, the data are well described by a model that accounts for changes in dielectric screening of the 1-D exciton, as the osmotic pressure forces conformational distortions in the PVA by rotating more polar groups to the nanotube surface. The model describes observed changes with hydration state and cross linking density variation from 0 to 14%.
9:00 PM - K10.2
Probing Defects in Multi-walled Carbon Nanotubes and Composites with Nanodiamond Induced by Irradiation using Resonance Raman Spectroscopy.
Sanju Gupta 1 , A. Schuttler 2 , J. Farmer 3
1 MURR & Physics, UMC 'n' PoliTO, Columbia, Missouri, United States, 2 EE, UMC, Columbia, Missouri, United States, 3 MURR and Physics, UMC, Columbia, Missouri, United States
Show AbstractIn the family of advanced multifunctional nanocarbons, carbon nanotubes are of great interest attributed to several unique physical (mechanical, electrical, thermal, chemical and biological) properties. Likewise, nanoscale diamond shows great promise due to similar range of unique physical properties. In this study, we investigated multi-walled carbon nanotubes (MWCNT) and their hybrids with ultradispersed nanodiamond (UDD) forming truly tetragonal-trigonal nanocomposite ensembles. Briefly, these materials were spin coated on SiO2/Si wafers forming thin films and subjected to gamma ray doses of 50, 100 and 103 kGy from 60Co nuclide. To assess structural modifications, they were analyzed prior to and post-irradiation in terms of morphology, microscopic structure and physical properties using electron microscopy, X-ray diffraction, resonance Raman spectroscopy and electrical I-V measurements. Experiments show that with irradiation MWCNT display various local structural instabilities due to nanoscopic defects in the lattice, albeit marginal as compared to single-walled carbon nanotubes. Since the irradiation conditions may resemble increased pressure regime enabling a degree of structural fluidity at nanoscale, a microscopic stress/strain may also result in the films. These effects exert a significant influence on their physical (optical and electrical) properties. Resonance Raman spectroscopy revealed that irradiation generated marginal defects elucidated through the variation in the intensity ratio of D to G band (ID/IG), D and G band position and widths and the position of the first overtone of the D band (G’ or 2D). The increase in the defect-induced D band intensity and a slight change in the position and intensity of G band are some of the implications for both the MWCNT and nanocomposites. We discuss our findings in terms of: 1) a minimal change in G band intensity is not explained by the defect-mediated double-resonance mechanism 2) a concomitant electronic charge transfer arising due to the difference in the electronegativity of C-sp3 and C-sp2 and misorientation of C-sp2 resulting in structural disorder and 3) softening of the q=0 selection rule. To further gain an insight into the nature of the defects (charged versus residual), the in-plane correlation length (La) was determined following TK or otherwise relation. The MWCNT combined with nanodiamond in most part retain their electrical/electronic behavior unlike those found with electron-beam irradiated materials that will also be discussed. Moreover, these irradiation processed material systems with induced defects may serve as electrochemical sensors with fast response time. The author (S.G.) acknowledges V. Padalko (Alit Co. Ukraine) for UDD material.
9:00 PM - K10.20
Investigation of Gadolinium Endofullerenes by Raman and Inelastic Electron Tunneling Spectroscopy with Theoretical Analysis.
Brian Burke 1 , Tsz-Wah (Jack) Chan 1 , Keith Williams 1 , Chunying Shu 2 , Harry Dorn 2 , James Kushmerick 3 , Alexander Puretzky 4 , David Geohegan 4
1 , University of Virginia, Charlottesville, Virginia, United States, 2 , Virginia Polytechnic Institute and State University, Blacksburg, Virginia, United States, 3 , NIST, Gaithersburg, Maryland, United States, 4 , CNMS, Oak Ridge, Tennessee, United States
Show AbstractThe structure and vibrational spectrum of Gd3N@C80 is studied through Raman and inelastic electron tunneling spectroscopy (IETS) as well as density functional theory (DFT) calculations. Hindered rotations, shown by both theory and experiment, indicate the formation of a Gd3N–C80 bond which reduces the ideal icosahedral symmetry of the C80 cage. We have conducted Raman measurements on Gd3N@C2n (n = 40, 41, 42, 43, 44), Gd2@C90 and Gd2C2@C92. Conductance measurements have been performed on Gd3N@C80 and reveal a Kondo effect similar to that observed in C60.
9:00 PM - K10.21
Manipulation of SWNT Microenvironment and its Effect on SWNT Photoluminescence.
Carlos Silvera-Batista 1 , Randy Wang 1 , Philip Weinberg 1 , Jason Butler 1 , Kirk Ziegler 1
1 Chemical Engineering, University of Florida, Gainesville, Florida, United States
Show AbstractSurfactants or polymers are often used to stabilize aqueous single-walled carbon nanotube (SWNT) suspensions. The resulting surfactant shell creates a repulsive barrier that overcomes the strong van der Waals attractive forces needed to disperse SWNTs. The fluorescence emission energies of SWNTs are sensitive to the surrounding environment with suspended SWNTs being red-shifted in comparison to SWNTs in air. The optically excited electronic states of SWNTs are highly mobile, making them sensitive to extrinsic effects that can reduce the quantum yield, including sidewall defects, protonation, aggregation, nanotube ends (i.e., lengths), surface reactions and surfactant inhomogeneities. Here we show how the surfactant shell around suspended SWNTs can be manipulated through mechanical or chemical annealing. Shearing of a SDS-SWNT suspension by flowing through a microfluidic channel is able to rearrange the surfactant structure around SWNTs. As a consequence, higher quantum yields and better protection against quenching protons are obtained. On the other hand, immiscible organic solvents are used to swell the hydrophobic core of the surfactant-SWNT complex. The new surfactant structure depends on the interactions among the organic solvent, the surfactant molecules and SWNTs. As a result, the wall of SWNTs can be exposed or better isolated from the suspending medium as evidenced by the lower or higher quantum yields in comparison to the as-prepared suspension. In addition, the formation of a microemulsion environment around SWNTs has allowed a systematic study of environmental factors such as the medium polarity on SWNT emission energy. PL and absorbance spectra of SWNTs show solvatochromic shifts in 14 nonpolar solvents, which are proportional to the solvent induction factor.
9:00 PM - K10.22
Stone-Wales Defects and Edge Reconstructions in Graphene Nanoribbons – A First-Principles Study.
Somnath Bhowmick 1 , Umesh Waghmare 2 , Vijay Shenoy 3
1 Materials Research Centre, Indian Institute of Science, Bangalore India, 2 , JNCASR, Bangalore India, 3 Department of Physics, Indian Institute of Science, Bangalore India
Show AbstractUsing density functional theory (DFT), we investigate the structure and properties of defective single layer graphene nano-ribbons, terminated by both armchair and zigzag edges. We observe that within the nano-ribbon, Stone-Wales defects introduce significant amount of stress, nature of which depends on the orientation of the defect with respect to the ribbon edge. We propose a simple model to explain this phenomena. Further, introducing the defects at the edge create "reconstructed edges", which differ significantly from regular armchair or zigzag ribbons in terms of shape, as well as properties. We examine several such cases in this work. We also discuss about the defect induced warping instability of the graphene nano-ribbons.
9:00 PM - K10.23
Influences of Covalent Defects on Electrical Characteristics and Phonon Softening in Metallic Carbon Nanotubes.
Khoi Nguyen 1 , Moonsub Shim 1
1 Materials Science and Engineering , University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Show AbstractIn metallic single-walled carbon nanotubes (NTs), G-band longitudinal optical (LO) phonon softens and broadens when the Fermi level is near the Dirac point due to the coupling of phonons to conduction electron excitations. Chiral metallic NTs may exhibit both LO and TO (transverse optical) mode softening since TO mode is not exactly along the circumferential direction. While charging dependence of Raman spectra has been studied in detail, how disorder complicates those spectral changes remains an open question. This talk focuses on how electrical characteristics and charging dependent Raman G-band phonon softening in individual metallic NTs are influenced by covalent defects. In addition to decreasing electrical conductance with increasing gate dependence eventually leading to semiconducting behavior, adding covalent defects reduces the degree of softening and broadening of LO phonon mode of the G-band near the Dirac point. On the other hand, TO mode softening is enhanced by defects. Implications on the interpretation of Raman G-band phonon softening and on utilizing Raman spectroscopy to examine covalent functionalization are discussed.
9:00 PM - K10.24
In situ Spectral Evolution of Raman Bands During the Chemical Vapor Deposition of Carbon Nanotubes.
Andrew Li-Pook-Than 2 1 , Jacques Lefebvre 1 , Paul Finnie 1 2
2 Department of Physics, University of Ottawa, Ottawa, Ontario, Canada, 1 , National Research Council of Canada, Ottawa, Ontario, Canada
Show AbstractIn situ Raman spectroscopy is an effective technique for monitoring the growth dynamics of carbon nanotubes (CNTs) and single-walled carbon nanotubes (SWNTs) in particular [1-5]. In this study, we track the spectral evolution and compare the growth profiles of different Raman bands relating to SWNT structure; namely, the G-band, the D-band, and multiple Radial Breathing Mode (RBM) bands. Distinct stages of CNT growth by chemical vapor deposition (CVD) can be identified and associated characteristic energies are measured. All CNTs are grown on silicon dioxide via hot-wall CVD under the presence of cobalt thin film catalyst and an ethanol carbon source. The effect of alumina catalyst support is investigated. [1] S. Chiashi et al., Chem. Phys. Lett. 386, 89 (2004). [2] K. Kaminska et al., Nanotech. 18, 165707 (2007). [3] S. Dittmer et al., Chem. Phys. Lett. 457, 206 (2008). [4] M. Picher et al., Nano Lett. 9, 542 (2009), [5] Finnie et al. Nano Research (2009) submitted.
9:00 PM - K10.25
The Structure and Properties of Carbon Cones.
Geir Helgesen 1 2 , Kenneth Knudsen 1 3 , Arne Skjeltorp 1 2 , Matti Knaapila 1 , Jean Patrick Pinheiro 1 , Marie Bourgeaux 1 , Henning Heiberg-Andersen 1 , Anette Gunnaes 2 , Oystein Prytz 2
1 Physics Department, Institute for Energy Technology, Kjeller Norway, 2 Department of Physics, University of Oslo, Oslo Norway, 3 Department of Physics, Norwegian University of Science and Technology, Trondheim Norway
Show AbstractIt is possible to make perfect conical carbon nanostructures that are fundamentally different from other nanocarbon materials such as buckyballs and nanotubes. These carbon cones (CC) are realized in five distinctly different forms. They consist of curved graphite sheets formed as open cones with one to five carbon pentagons at the tip with successively smaller cone apex angles, ranging from 112.9o to 19.2o. Disk-shaped particles are also produced in the same pyrolysis process. The structure and physical properties of these carbon cones have been relatively little explored so far. Ad-hoc model calculations show that the functional properties of carbon cones appear to be different from those of the other forms of carbon, due to fundamentally different topology and symmetry. We present recent results from our study of the structure of these carbon cones and disks using scanning- and transmission electron microscopy, X-ray- and electron diffraction. The particles consist of thin crystalline cores that are usually coated with amorphous carbon layers. Heat-treatment of the as-produced CC raw material improves the crystalline quality. This work was supported in part by the Research Council of Norway project no. 191621/V30 and the EU project no. NMP3-CT-2006-032970.
9:00 PM - K10.26
In-situ TEM-STM Observations of SWCNT Ropes-tubular Transformations.
Francisco Sola 2 , Luis Fonseca 1 , Marisabel Lebron-Colon 2 , Carlos Marin 1 , Azlin Biaggi-Labiosa 2 , Michael Meador 2
2 Materials and Structures Division, Polymeric Materials Branch, National Aeronautics and Space Administration, Glenn Research Center, Cleveland, Ohio, United States, 1 Institute for Functional Nanomaterials and Department of Physics, University of Puerto Rico, San Juan, Puerto Rico, United States
Show AbstractSingle walled carbon nanotubes prepared by the HiPCO process were purified using a modified method of gas phase purification technique. A TEM-STM holder was used to study the morphological changes of SWCNT ropes as a function of applied voltage. A local transformation from rope to tubular structure was observed to start in a contact-rope region. The tubular transformation progressed (in time) along the rope length during the voltage application periods. Kinks formation, buckling behavior and eventual breakdown of the system were observed. Moreover, some buckling events were observed to be reversible at 5V. Both, tubular transformation and creation of defects, are explained in terms of temperature gradients due to electrical resistance of the system, and are believed not to be caused by electron irradiation. Furthermore, the tubular transformation is attributed to the coalescence of SWCNTs.
9:00 PM - K10.27
Photoluminescence Enhancement of Single Walled Carbon Nanotubes in Aqueous Solutions.
Darlington Abanulo 1 2 , Andrey Dobrynin 2 , Fotios Papadimitrakopoulos* 1 2 3
1 Nanomaterials Optoelectronics Laboratory, Institute of Materials Science, University of Connecticut, Storrs, Connecticut, United States, 2 Polymer Program, Institute of Materials Science, University of Connecticut, Storrs, Connecticut, United States, 3 Department of Chemistry, University of Connecticut, Storrs, Connecticut, United States
Show AbstractSingle Walled Carbon Nanotubes (SWNTs) are nanomaterials whose optical properties are strongly influenced by their (n,m) chiral index. The strong potential of well-defined (n,m) SWNTs in bio-imagery, bio-sensory and nano-optoelectronics applications was significantly advanced by the recent 20% photoluminescence (PL) quantum yield (QY) report from our group (Science, 323, 1319-1323 (2009)). In order to attain high efficiencies, nanotube bundling needed to be actively minimized while seamlessly wrapped with a flavin-based surfactant to provide a highly uniform environment. While the latter can be easily realized in organic media by controlling the solubility of FC12 through solvent-solute interactions, the ability to firm-up the flavin-flavin interaction in aqueous environment is challenging. In this contribution, we report an innovative self-assembly methodology that imparts effective individualization of flavin-wrapped SWNTs in aqueous media. This scheme is based on a secondary self-organization around the primary FMN organization, which strengthens the helix and results in SWNT PL quantum yields as high as 5.0% in aqueous media. Aside from the profound importance of this discovery to bio-imagery and bio-sensory application, the secondary self-organization around the primary FMN helix provide a unique methodology to yield even stronger nanotube individualization, while retaining their pristine structure undamaged.Financial support from AFOSR is kindly acknowledged.
9:00 PM - K10.28
Flexible and Transparent SWCNT Electrodes for Alternating Current Electroluminescence (ACEL) Devices.
Christian Schrage 1 , Stefan Kaskel 1
1 , Dresden University of Technology, Dresden Germany
Show AbstractCoating of single walled carbon nanotube dispersions on flexible polymer substrates allows the generation of transparent electrodes. The two-dimensional random SWCNT network formed on the surface is conductive, mechanically robust and enables the application of SWCNT electrodes in several devices like OLEDs, polymer-solar cells or transparent transistors. This presentation focusses on the use of SWCNT electrodes in alternating current electroluminescence (ACEL) devices.ACEL devices consist of an efficient electroluminescence phosphor sandwiched between two electrodes excited in a strong electric field. The resulting EL emission color depends on the used phosphor and excitation conditions as well. ACEL devices can be used as backlights in cellular phones or PDAs and also in large scale architectural and decorative lighting. SWCNT thin film electrodes (50-160 nm) were made using a spray-coating process suitable for adjusting transparency and sheet resistance. After optimizing the dispersion procedure SWCNT electrodes were employed in three types of devices. The device characteristics were examined with respect to the sheet resistance of the SWCNT electrodes. It was found that SWCNT electrodes are a suitable alternative for ITO electrodes resulting in a comparable emission intensity with equal transparency.
9:00 PM - K10.29
Probing Interaction Strength Using Carbon Nanotubes as Ubiquitous Fluorescence Quenchers.
Chris Collison 1 , Amanda Preske 1 , Susan Spencer 1 , Sidney Coombs 1 , Steven Pellizzeri 1
1 Chemistry, RIT, Rochester, New York, United States
Show AbstractSingle-walled carbon nanotubes (SWCNT) have the potential to be used in a variety of applications. Yet, successful usage often relies on debundling the tubes and keeping them isolated from each other so as to realize their attractive electrical properties. Successful debundling and isolation techniques result from better understanding of the interactions between SWCNT and solvents and/or second materials in a composite.SWCNT can be synthesized in different ways, each resulting in a unique mixture of diameter and chirality. In addition to semiconducting chiralities, any synthesized mixture includes chiralities of metallic character. As a result, nanotube mixtures act as ubiquitous fluorescence quenchers when added to a luminescent sample in solution. Of course the extent of quenching will depend upon the relative amount of metallic tubes, the proportion of semiconducting tubes having electronic states aligned appropriately with the fluorophore's excited state, and the extent of nanotube debundling. Among other contributing factors, quenching is particularly sensitive to the degree of complexation of the nanotubes with the fluorophore.We will present results from the quenching of a variety of molecular and polymeric fluorophores with SWCNT samples. The results allow us to better understand what functional groups lead to stronger nanotube complexes, and hence how nanotube dispersion and manipulation can be improved. Furthermore we look at the differences between quenching of conjugated polymers and their small-molecule analogs so as to appreciate the future role of nanotubes in improving the manufacture and operation of polymer photovoltaic devices.
9:00 PM - K10.3
Environmental Effect on the Performance of Carbon Nanotubes Based Devices.
Gugang Chen 1 , Tereza Paronyan 2 , Elena Pigos 1 , Gamini Sumanasekera 2 , Avetik Harutyunyan 1
1 , Honda Research Institute USA, Inc., Columbus, Ohio, United States, 2 Physics, University of Louisville, Louisville, Kentucky, United States
Show AbstractThe viability of carbon nanotubes exploitation in hybrid electronics under adequate conditions still needs to be proven due to their extreme interfacial sensitivity, which is the main hurdle for their application. We performed in situ electrical and Raman scattering measurements on an individual single-walled carbon nanotube in the field-effect transistor geometry under different ambient and temperature. The Raman G+ mode frequency responds in synchronization with changes in the charge density induced by the external gate voltage displaying predictable temperature dependence. Yet, the variation of the ambient caused a blue shift of the Raman G+ mode frequency, accompanied with a reversible transformation of the device performance from p-type in air to n-type in vacuum (1.1 x 10-6 mbar) through intermediate steps. We attribute these alterations to the charge transfer induced phonon renormalization by environmental oxygen. Our results imply that the performance of nanotube based devices is very sensitive to the energetic levels of impurities that are introduced by the environmental species.
9:00 PM - K10.31
Optical Quality Nanotube-polymer Composites through Non-aqueous Dispersions.
Tawfique Hasan 1 , Zhipei Sun 1 , Daniel Popa 1 , Felice Torrisi 1 , Fengqiu Wang 1 , Francesco Bonaccorso 1 , Andrea Ferrari 1
1 Engineering Department, Cambridge University, Cambridge United Kingdom
Show AbstractSWNTs homogeneously embedded in polymer matrices are excellent saturable absorbers for passively mode-locked lasers [1-3] as they provide better physical stability and repeatable performance compared to as-grown/deposited SWNT films. These require low non-saturable losses, resistance to humidity and environmental stability for practical, long term implementation. The non-saturable losses mostly arise from large nanotube aggregates, overtones of fundamental molecular vibrations from the host polymer, defects in the composite, surfactants and impurities which can be largely overcome by uniformly dispersing nanotubes in polymer matrices. The environmental stability of the composites depends on the polymers used. As water soluble polymer matrices do not display long term stability, particularly in humid environment, polymer composites with homogeneous nanotube distribution prepared through non-aqueous route are the key to optimize the saturable absorbers. Here, we report the processing and characterization of SWNT-composites for photonic applications based on polycarbonate (PC), styrenemethylmethacrylate (SMMA) and Polydimethylsiloxane (PDMS) which are highly stable to harsh environmental and chemical conditions [4]. The nanotube dispersion strategy used here enables us to fabricate composites with submicron nanotube aggregations, therefore avoiding scattering losses for transmissive device structures [4]. SWNTs are first dispersed in 1,2-dichlorobenzene (DCB) or chloroform by ultrasonication aided by a polythiophene (PT) derivative acting as a dispersant. After the removal of residual impurities, the host polymer is added to the solution. In case of PDMS, the curing agent is added after the nanotube dispersion is ultrasonicated with the base. A further ultrasonication procedure precedes the mixtures are drop cast under vacuum and/or at elevated temperature (80°C), resulting in freestanding composites with uniform, sub-micrometer distribution of SWNTs, as confirmed by optical microscopy. The composites are then characterized for their linear and nonlinear properties by UV-Vis-NIR spectroscopy and power dependent measurements, the latter with a femtosecond laser source. These saturable-absorber composites are finally used as passive mode-lockers in fiber laser cavities to generate sub-picosend optical pulses.1. V. Scardaci et al. Adv. Mater. 20, 4040 (2008)2. Z. Sun et al. Appl. Phys. Lett. 93, 061114 (2008)3. F. Wang et al. Nature Nano 3, 738 (2008) 4. T. Hasan et al. Adv. Mater. (Accepted)
9:00 PM - K10.32
Modeling the Kinetics Behind the Self-Assembly of Nanotube-Based Photoelectrochemical Complexes.
Ardemis Boghossian 1 , Moon-Ho Ham 1 , Jong Hyun Choi 2 , Michael Strano 1
1 Chemical Engineering, MIT, Cambridge, Massachusetts, United States, 2 Mechanical Engineering, Purdue University, West Lafayette, Indiana, United States
Show AbstractIn our work, we have developed the first photoelectrochemical complex capable of mimicking the self-assembly process used in plant repair to minimize photodamage. By mimicking the dynamics behind this self-repair, one can create more robust solar conversion systems capable of indefinite lifetimes. To form such a complex, a solution of phospholipids, recombinant proteins, single-walled carbon nanotubes (SWNTs), photosynthetic reaction center (RCs), and sodium cholate surfactant is dialyzed to remove sodium cholate. Upon surfactant removal, the remaining components spontaneously self-assemble into a reaction center-lipid bilayer nanodisc-nanotube (RC-ND-SWNT)complex capable of solar energy conversion when in the assembled state. This self-assembly process is completely irreversible; the complex disassembles into its free components upon surfactant re-addition.To study the dynamics behind this complex formation, a kinetic model of the solution dialysis has been developed. According to this model, the complex can reversibly transition from the disassembled to the assembled state only if the rate of surfactant removal exceeds a kinetic threshold. This kinetic threshold reflects the competition between the relatively fast formation of ND-SWNT complexes and the kinetically slower, but thermodynamically favored assembly of homogeneous, bundled SWNT phases. Kinetic rate parameters for ND-SWNT formation were evaluated by fitting the model to experimental data, which was used to confirm the reversibility of the system as the solution was continuously cycled between the assembled and disassembled states.
9:00 PM - K10.33
Carbon Nanotubes as a Near-perfect Optical Absorption Material.
Cheng-Ying Chen 1 , Sheng-Yi Lu 2 , Hsin-Fu Kuo 2 , Wen-Kuang Hsu 2 , Jr-Hau He 1
1 , Graduate Institute of Photonics and Optoelectronics & Department of Electrical Engineering, National Taiwan University, Taipei Taiwan, 2 , Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu Taiwan
Show AbstractCarbon nanotubes (CNTs) have led to the broad applications for pyroelectric detectors [1, 2], solar cells [3, 4], bolometers [5]. In this work, we demonstrated that the vertically aligned CNT arrays can act as a near-perfect optical absorber. The 30μm well-aligned CNT arrays, with the diameter of 100±20 nm, on Si wafer were prepared by chemical vapor deposition (CVD) process similar to what has been reported elsewhere [6]. Spectral reflectance measurements show extremely low reflection and ultra high absorption over a broad range of wavelengths and a wide range of angle of incidence (AOI). For example, the reflectance of R = 0.01-0.03% and absorption of A = 99.97-99.99% at AOI=80. These results are due to the nanoscale surface roughness of the arrays and the low effective refraction index of the arrays. The optical performances approach an ideal black material. References[1] Lehman J H, Deshpande R, Rice P, To B and Dillon A C 2006 Infrared Phys. Technol. 47 246–50;[2] Lehman J H, Engtrakul C, Gennett T and Dillon A C 2005 Appl. Opt. 44 483–8[3] Camacho R E et al 2007 JOM 59 39–42[4] Turano S P, Flicker J D and ReadyW J 2008 Carbon 46 723–8[5] Tarasov M, Svensson J, Kuzmin L and Campbell E E B 2007 Appl. Phys. Lett. 90 163503[6] Fang W, Chu H Y, Hsu W K, Cheng T W, and Tai N H 2005 Adv. Mater 17 2987
9:00 PM - K10.34
Effects of Wall Thickness and Dielectric Environment on the Optical Properties of Gold Nanotubes.
Micha Fireman 1 , Deirdre O'Carroll 1 , Harry Atwater 1
1 Thomas J. Watson Sr. Laboratory of Applied Physics, California Institute of Technology, Pasadena, California, United States
Show AbstractAn important attribute of metallic nanotubes over metallic nanowires for sensing applications, in addition to increased surface area-to-volume ratio, is that evanescent surface plasmon modes can propagate at the metal-dielectric interface on both inner and outer nanotube surfaces. This factor could allow metal nanotube-based devices to more fully take advantage of surface plasmon interactions with the local dielectric environment, which, in turn, could increase the sensitivity factor of the nanostructure to the refractive index of its surroundings. It has been shown, for instance, that for hollow gold nanoshells a greater wavelength shift per unit change in surrounding refractive index can be achieved when compared to solid gold nanospheres.1 In this work, we experimentally and theoretically investigate how the optical properties and refractive index sensitivity factor of gold nanotubes are modified by systematically varying nanotube wall thickness. Nanotube fabrication is carried out by, firstly, electrochemically depositing sacrificial nickel nanowires into the pores of nanoporous alumina templates. Secondly, a pore-widening step facilitates the electrodeposition of a gold shell around the nickel wire cores. Selective chemical etching of the nickel nanowires yields vertically oriented arrays of gold nanotubes with typical outer diameters of 270 nm over an area of ~30 mm2. The wall thickness of the gold nanotubes is tuned from 15 nm to > 100 nm by varying the pore widening time prior to electrodeposition of gold. Dark-field spectroscopy of nanotube arrays indicates that resonant scattering at visible wavelengths red shifts with decreasing wall thickness. By monitoring the change in resonant scattering wavelength with refractive index of the environment sensitivity factors of ~75 nm per refractive index unit (RIU) were experimentally determined for gold nanotube arrays.Full-field electromagnetic simulations show that nanotube sensitivity factor increases with decreasing wall thickness - with values of more than 170 nm/RIU possible for individual gold nanotubes with wall thickness less than 50 nm. Both localized surface plasmon resonances and propagating surface plasmon polaritons are shown to contribute to nanotube near-field spectra, with the latter excitation exhibiting greater refractive index sensitivities. This work demonstrates that the sensing wavelength and sensitivity factor of gold nanotubes can be tuned by varying nanotube wall thickness. With choice of a suitable metal, shell thickness and inner/outer diameter, several applications of metallic nanotubes are foreseeable in addition to refractive index sensing. For example, the light-emitting properties of semiconductors be modified or enhanced by placement in the nanotube core and arrays of vertically aligned plasmonic waveguides or nanoscale optical cavities could be realized.1. Y. Sun, B. Mayers, Y. Xia, Metal Nanostructures with Hollow Interiors. Adv. Mater. 15 (2003) 641.
9:00 PM - K10.36
Carbon Nanotube-silicon Heterojunction Solar Cells with Controlled Electronic Properties.
Sungwoo Yang 1
1 Chemistry, Duke University, Durham, North Carolina, United States
Show AbstractIn recent year, carbon nanotubes (CNTs) have attracted a great interest in PVC application due to their unique mechanical, chemical and electrical properties. Depending on its intrinsic chiral vector, CNT can be metallic or semiconducting. The local density of state (DOS) of CNT falls into van Hove singularities with symmetric direct band gaps as one dimensional material. This direct band gap is essential to realize PVC devices because there is no photon-excited energy loss due to phonon phenomenon. In addition, the band gap of CNT is inversely proportional to its diameter and as-grown product in CVD system usually includes CNTs with various diameters resulting in a variety of energy band gaps to absorb a broad range of photon energy. In last year, PVC utilized CNTs reaching 7% efficiency and as-grown CNTs were used for this project. However, inherently as-grown CNTs are a mixture of metallic and semiconducting CNT. However, the presence of metallic CNTs is expected to contribute to the recombination between photon-excited electron and hole pairs resulting in decreasing performance of PVC. Meanwhile, semiconducting CNTs might increase the performance by providing lower resistivity pathway due to the increased carrier mobility in p-n heterojunction. Therefore, by removing metallic CNT, we improved the efficiency of PVC. In this work, PVC based on CNTs has shown increased efficiency by controlling CNT’s electrical properties. In order to separate CNTs by their metallicity, 1-Docosyloxymethyl-pyrene (DOMP) was used to separate CNTs because a stronger chemiadsorption of DOMP occurs with semiconducting CNTs than with metallic ones. Radial breath mode (RBM) of metallic CNT is located between 170cm-1 to 210 cm-1 with 633nm excited wavelength. Raman data confirms higher semiconducting CNTs in the supernatant of centrifuged solution. On the other hand, noticeable amount of metallic CNTs were observed in the residue. In addition, by simulating energy level analysis of the heterojunction between CNT and n-type silicon, we found that energy band gap of CNT might be a significant factor to increase this PVC’s efficiency. In order to control CNT’s energy band gap, density gradient ultracentrifugation (DGU) method was used resulting in improved efficiency of PVC. Synthesized double walled carbon nanotubes (DWNTs) were separated by DGU method and UV-vis NIR data demonstrated that mixture types of synthesized CNTs were successfully sorted by their number of side walls and diameter. Larger diameter of SWNT was located at the higher buoyant density point. DWNTs shows relatively higher buoyant density compared to SWNTs. These sorted CNTs will be directly sprayed on n-type silicon wafer to fabricate solar cells with different energy level of p-n heterojunction. We have not finished this work to optimize CNT’s energy band gap to increase PCV efficiency. However, the work is expected to be completed within three months.
9:00 PM - K10.37
Photo-Electrochemical Properties of Carbon Nanotube/TiO2 and Carbon Nanotube/SnO2 Nanostructures Prepared by Three Different Methods.
Baleeswaraiah Muchharla 1 , Lifeng Dong 1
1 Department of Physics, Astronomy, and Materials Science, Missouri State University, Springfield, Missouri, United States
Show AbstractIn this work, we used three different methods to fabricate solar cell structures on indium tin oxide (ITO) substrate. For the first method, multi layered structure was prepared by using single walled carbon nanotubes (SWCNTs) and photoactive nanoparticles, such as TiO2 and SnO2. SWCNTs layer was firstly deposited on the ITO substrate, and photoactive material was coated on the top of the SWCNT layer. For the second method, photoactive particles were added to the solution of SWCNTs. The solution was mechanically stirred and then deposited on the ITO substrate. For the third method, we synthesized photoactive particles on SWCNTs through a chemical-solution routine using TiCl4 or SnCl4 as precursors. The morphology and structure of the SWCNTs coated with TiO2 or SnO2 nanoparticles prepared with different method were characterized by field emission scanning electron microscope (FESEM) equipped with X-ray energy dispersive spectrometer (EDS) and a scanning transmission electron microscopy (STEM) detector. The photo-electrochemical properties of all electrodes were characterized by using an electrochemical station; mainly, we examined the photocurrent generated under periodic illumination. We observed the influences of SWCNTs for the different photoactive materials. Our results indicate that there are significant differences in the photocurrent in the presence of SWCNTs. We propose the following hypothetical mechanism: without carbon nanotubes, generated electrons (when light is absorbed by TiO2 and SnO2 particles) must cross the particle network to reach an electrode. Many electrons never escape to generate an electrical current. The carbon nanotubes "collect" the electrons and provide, therefore, a more direct route to the electrode, thus improving the efficiency of the solar cells. Acknowledgement: This work was partially supported by a Faculty Research Grant from Missouri State University, the American Chemical Society Petroleum Research Fund (47532-GB10), and the National Science Foundation (DMR-0821159).
9:00 PM - K10.38
UV-photocatalytic Reduction of Graphene Oxide and its Application as an Interfacial Layer toEnhance the Performance of Dye-sensitized Solar Cells.
Sung-Ryong Kim 1 , Md. Khaled Parvez 1 , Manish Chhowalla 2
1 , Chungju National University , Chungju Korea (the Republic of), 2 , Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States
Show AbstractA mixture of graphene oxide (GO) and TiO2 nanocomposites was reduced photocatalytically by UV-irradiation and applied as an interfacial layer between a fluorine doped tin oxide (FTO) layer and a nanocrystalline TiO2 film. The interfacial layer effectively reduced the contact between I- ions in the electrolyte and the FTO layer, which inhibited the back transport reaction of the electrons. The introduction of a graphene-TiO2 interfacial layer increased the Voc and fill factor by 34 mV and 14 %, respectively, and the photoconversion efficiency was improved from 4.43 % to 4.72 %.
9:00 PM - K10.39
Inorganic EL Devices with CNT-ZnS:Cu,Cl Phosphor.
Jin-Young Kim 1 , SangHyeun Park 2 , SeGi Yu 3
1 Dept. Physics, Sungkyungkwan University, Suwon Korea (the Republic of), 2 Advanced Material Lab, Samsung Advanced Institute of Technology, Yongin Korea (the Republic of), 3 Dept. Physics, Hankuk University of Foreign Studies, Yongin Korea (the Republic of)
Show AbstractElectroluminescence (EL) characteristics of green-emission ZnS:Cu,Cl-based ac-type inorganic powder electroluminescent structures were examined by inserting carbon nanotubes (CNTs) into or next to the dielectric layer. For the top-emission type EL structure, where the luminescent light was emitted from the top of the structure, was fabricated by assembling in order, a top electrode, an emitting layer, a dielectric layer, and a bottom electrode from the top. BaTiO3 powder mixed with CNTs was used as a dielectric layer or CNTs were deposited between the bottom electrode and BaTiO3 dielectric layer in order to improve the role of the dielectric layer in the structure. Luminance of an EL structure with CNTs inclusion was greatly enhanced possibly due to the high dielectric constant in the dielectric layer of BaTiO3/CNTs, which is one of hot research topics utilizing nano-objects for intensifying dielectric constant and reducing dielectric loss at the same time. A variation on the CNTs themselves and their inclusion methods in the dielectric layer has been exhorted, and the underlying mechanism for the role of CNTs in the EL structure will be explained in the poster. In order to extend the flexibility of EL devices, EL devices were fabricated on the paper substrate and their performance was compared other EL devices on the plastic-based substrate. The work done by S.Y. was supported by the Korea Research Foundation Grant funded by the Korean Government (MOEHRD) (KRF-2007-313-C00299). E-mail address:
[email protected]9:00 PM - K10.4
Understanding Structural and Physical Properties of Individual Nanomaterials: Thermal/thermoelectric and Electrical Transport Properties.
Taekyung Kim 1 , Charles Harris 2 , Gang Chen 2 , Jianyu Huang 1 , Michael Siegal 1
1 , Sandia National Labs, Albuquerque, New Mexico, United States, 2 , Massachusetts Institute of Technology, Boston, Massachusetts, United States
Show AbstractCurrently, there is a lack of correlation between microstructure and physical property studies of nanomaterials such as carbon nanotubes (CNTs), nanowires, and graphene. It is important to correlate structure with physical properties such as electrical and thermal transport due to the sensitivity of these properties to the atomic structure of quasi 1- and 2-dimensional nanomaterials. Here, we present a microfabricated device, compatible with a transmission electron microscope (TEM), for such studies. The device uses a field-effect transistor geometry with a through-etched window for both TEM observation and a suspended Pt heater-sensor. The microfabricated heater-sensor enables simultaneous study of structure, thermal/thermoelectric properties, and electric transport properties of individual nanomaterials due to the back-gated field-effect transistor geometry. Every experimentally-measured property will be correlated to the atomic structure of a given individual nanomaterial, such as the number of walls and diameters of CNTs. Preliminary electrical/thermal transport measurements from individual nanomaterials will be presented.Supported by Laboratory Directed Research and Development, Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under contract DE-AC04-94AL85000.
9:00 PM - K10.40
Structure and Properties of Macromolecules made of Single Walled Carbon Nanotubes - `Super'-Fullerenes.
Vitor Coluci 1 , Ricardo dos Santos 2 , Douglas Galvao 3
1 Faculty of Technology, State University of Campinas, Limeira, SP, Brazil, 2 Departamento de Engenharia Agricola, Universidade Estadual de Maringa, Maringa, SP, Brazil, 3 Applied Physics Department, Institute of Physics, State University of Campinas, Campinas, SP, Brazil
Show AbstractRecent advances in synthesis, sorting, and self-assembly protocols have made possible to controllably assemble single walled carbon nanotubes (SWNTs) in terms of position and orientation. The achievement of such procedures would allow the fabrication of ordered SWNT networks, representing a breakthrough in the ``bottom-up'' manufacturing approach. Based on these possibilities, different types of ordered SWNT networks have been proposed and investigated. By heuristically replacing the carbon-carbon bonds of the graphene structure by SWNTs and the carbon atoms by appropriate SWNT junctions, one-, two-, and three-dimensional ordered SWNT networks were proposed [1,2], named as `super'-nanotubes, `super'-graphene, and `super'-diamond, respectively [1,2]. On the other hand, `zero'-dimensional structures have not been investigated yet. In this work, we propose and theoretically investigate closed ordered SWNT networks that represent `zero'-dimensional structures. These networks were designed based on the topology of the highest symmetrical fullerene molecules , being thus topologically closed macromolecules (composed of 1000 atoms or more). Classical atomistic calculations were used to predict stability, thermal, vibrational, and mechanical properties of these molecules. Due to the analogy of the SWNT networks proposed here with the fullerene molecules we named them as `super'-fullerenes. The molecules were constructed connecting Y-like junctions through (8,0) SWNTs following the topology of C20 and C60 fullerene molecules. While the locations of the junctions on the networks are related to the positions of the atoms on the fullerene molecule, the SWNTs mimic the chemical bonds among carbon atoms. The investigated macromolecules present diameters of ~10 nm and present high porosity, low density (~1 g/cm3), and high surface area (~2500 m2/g). Our results predict gas phase specific heat of about 0.4 Jg-1K-1 at room temperature and high flexibility under compressive strains. These properties make these hypothetical macromolecules good candidates for gas storage material and biomolecular sieves. Combining the remarkable molecular recognition properties of DNA with respect to carbon nanotubes and the recent advances of DNA nanotechnology [3], we suggest here that the use of DNA as scaffolds might allow the synthesis of the SWNT macromolecules proposed here.[1] V.R. Coluci, D.S. Galvao, A. Jorio, Nanotech. 17 617 2006; [2] J.M. Romo-Herrera et al., Nano Lett. 7 570 2007; [3] Y. Zhang, N.C. Seeman J. Am. Chem. Soc. 116 1661 1994; [4] Y. He et al., Nature 452 198 2008
9:00 PM - K10.41
Wide-range Optical Spectra of Transparent Conducting Carbon Nanotube Films.
Katalin Kamaras 1 , Aron Pekker 1 , Norbert Nemes 2 , Mar Garcia-Hernandez 3
1 , Research Institute for Solid State Physics and Optics, Budapest Hungary, 2 GFMC. Dpto. Fisica Aplicada III, Universidad Complutense de Madrid, Madrid Spain, 3 Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, Cantoblanco Spain
Show AbstractConducting carbon nanotube networks are used in many applications, e.g. in flexible transparent electrodes or as substrates for neuron growth. The most important parameters in these applications are the dc conductivity and the electromagnetic spectrum in the widest possible range; these values then can be tuned by choosing the appropriate starting material and subject it to physical or chemical modification. We have chosen wide-range (far-infrared through ultraviolet, 10 meV - 4 eV) optical spectroscopy on transparent carbon nanotube films to characterize such networks. This substrate-free method yields information about intrinsic conductivity, metallic/semiconducting ratio, as well as on the transparency window. We also performed resistivity measurements as a function of temperature. When comparing optical conductivity of different types of networks, calculated from transmission, we find that while arc discharge and laser-ablated materials combine metallic dc conductivity with high transparency in the mid- and near infrared range, HiPCO and CoMoCat tubes exhibit a much lower metallic content and therefore lower conductivity. However, small-gap (~10 meV) tubes are present in the latter type of nanotubes as well. Both the window of transparency and the dc conductivity can be tuned by several methods: doping, de-doping or sidewall functionalization. For networks with nanotube density above the percolation threshold, the low-frequency optical conductivity approaches the dc value. Most transparent conducting applications, however, are targeted at the visible region, and a figure of merit is desirable which combines easily measurable dc sheet resistance and transmission at visible wavelengths. We propose the ratio of optical density (-log T) and sheet conductance as such a figure. This value can be determined without measuring the thickness for a given type of network, and has several advantages over previously used estimates: it is independent of the model describing the optical conductivity, and the two quantities (representing optical and electrical quality, respectively) can be combined into simple plots where the proximity to the technologically desired parameter sets is easily visualized. Supported by the European Commission NEURONANO FP6 grant (NMP4-CT-2006-031847).
9:00 PM - K10.42
Fast Diffusion of Graphene Flake on Graphite Surface.
Irina Lebedeva 1 2 , Olga Ershova 2 , Andrey Knizhnik 1 , Andrey Popov 3 , Yurii Lozovik 3 , Boris Potapkin 1
1 , Kintech Lab Ltd, Moscow Russian Federation, 2 , Moscow Institute of Physics and Technology, Moscow Russian Federation, 3 , Institute of Spectroscopy, Troitsk Russian Federation
Show AbstractDiscovery of graphene aroused considerable interest of the scientific community due to the unique electric and mechanical properties of graphene. We propose a new phenomenon of fast diffusion and drift of a graphene flake on the graphite surface related to the rotation of the flake to a configuration incommensurate with the underlying graphite surface. Both DFT and semi-empirical calculations show that the energy required for rotation of a graphene flake to the incommensurate configuration is close to the barrier for sliding of the flake along the surface. Therefore, the probability for the flake to rotate to the incommensurate configuration is comparable to that for the movement to the adjacent energy minimum. However, the distance made by the flake in an incommensurate configuration can significantly exceed the distance between the energy minimums. Because of the large diffusion length, diffusion via the rotation to the incommensurate configuration should provide the diffusion rate which is much higher than that for a flake in the commensurate configuration. Molecular dynamics simulations of diffusion of a graphene flake on the graphite surface are performed at room temperature. These simulations demonstrate that fast diffusion of the flake can actually be realized. The diffusion length of the flake exceeds the lattice constant for graphene by one-two orders of magnitude. We also derive analytic expressions for the diffusion and drift coefficients. The results of the analytic calculations are in good agreement with those of the molecular dynamics simulations. Since graphene is considered as a promising material for the use in nanoelectromechanical systems, it is important to control graphene diffusion and drift. Thus we also discuss the ways in which it is possible to suppress or enhance diffusion and drift of the flake. One way is fixation of the flake orientation, which can be realized if the flake has an electric or magnetic dipole moment and it is placed in an electric or magnetic fields, respectively. The drift and diffusion can be also enhanced if the flake contains defects and remains incommensurate with the graphite surface. This assumption is confirmed by the molecular dynamics simulations.
9:00 PM - K10.43
Development of a Sample Preparation Method for Microscopic Characterization of Multi-Walled Carbon Nanotubes.
Li Han 1 , Reshan Fernando 1 , Teri Walker 1 , David Ensor 1 , N. Walker 2 , Brad Collins 2
1 , RTI International, Research Triangle Park, North Carolina, United States, 2 National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, United States
Show AbstractMulti-walled carbon nanotubes (CNTs) have unique mechanical, electrical and thermal properties. Among other characteristics, the smaller diameter and the higher aspect ratio are considered as two of the most important factors that contribute to their exceptional properties. Microscopic techniques are often used in physical characterization of carbon nanotubes. However, it is quite a challenge to obtain accurate measurements of individual CNTs because these materials normally exist in a highly agglomerated form. Obviously, it is necessary to disperse the nanotubes and to maintain them in their dispersed state until statistically valid number of measurements is taken for each CNT sample. Furthermore, it is imperative that the dispersion reagent and the method do not alter the physical characteristics of the CNT. In this paper, we report the development of a method to prepare highly dispersed CNTs for microscopic characterization without functionalizing the CNT surface. The developed dispersion method was successfully used to determine the diameter and the length of six different commercially available CNTs using transmission electron microcopy (TEM) and scanning electron microscopy (SEM). The results will be presented and compared to the manufacturer reported values.
9:00 PM - K10.44
Evaluating Properties of Graphene Sheets using Conductive Probe Atomic Force Microscopy.
Fanny Hauquier 1 , David Alamarguy 1 , Sophie Noel 1 , Pascal Viel 2
1 LGEP, Supelec, Gif sur Yvette France, 2 LCSI-DSM-IRAMIS, CEA, Gif sur Yvette France
Show AbstractGraphene has attracted recently an increasing interest in the scientific community. The attention is due to its outstanding transport properties making this material the ideal candidate for future nanoelectronics applications, and to its intriguing physical behaviour as a link between solid state and quantum electrodynamics. In our work, the covalent grafting of graphene sheet was made onto self-adhesive surfaces based on aryldiazonium salt layers. Indeed, previous work in our group has shown that the chemistry of aryldiazonium salts has been thoroughly used to obtain self-adhesive surfaces using the grafting of ultrathin polyphenylene-like film in a very simple and robust way. This organic layer was characterized by ATR FT-IR and XPS. The Raman spectroscopy was used to estimate the number of graphene layers in this graphene/organic interface. A nanoscale investigation on the electrical conductivity and friction properties of graphene and organic layer was carried out with a conductive probe AFM. Simultaneous analysis of the electrical and mechanical properties of the grafted graphene was performed during tip/sample approach and withdrawal curves and current-voltage curves.
9:00 PM - K10.45
Nanowire Lithography on Silicon and Graphene.
Tero Kulmala 1 , Andrea Fasoli 1 , Antonio Lombardo 1 , Alan Colli 2 , Andrea Ferrari 1
1 Department of Engineering, University of Cambridge, Cambridge United Kingdom, 2 , Nokia Research Centre, Cambridge United Kingdom
Show AbstractNanowire-lithography (NWL) consists of using NWs as etch masks to transfer their one-dimensional morphology to an underlying substrate [1,2]. Here we show that the lateral features of fully-oxidised silicon NWs (SiNWs) can be mirrored in a silicon-on-insulator (SOI) wafer by means of a highly selective, anisotropic Deep Reactive Ion Etching (DRIE)[2]. Planar field-effect transistors made of a single SOI-NW channel exhibit a contact resistance below 20 kOhm and a consistent scaling behaviour with channel width. Further, we assess the electrical response of a SOI-NW network obtained using a mask of superimposing SiNWs ink-jetted from solution [2,3]. Even by using a poorly conducting percolation network as mask, the resulting conformal network etched into the underlying wafer is monolithic, with single-crystalline bulk junctions. We then show that this concept can be applied to other materials, such as graphene. When shaped down to ribbons, electron confinement opens a gap [4], making it suitable for the realization of devices. Here we show that SiNWs are ideal to implement NWL on graphene[5]. SiNWs are mechanically transferred or dispersed from solution onto graphene flakes produced on SiO2 by exfoliation. The NW morphology is transferred onto the graphene flake by a low power O2 plasma. The process leads to conformal nanoribbons with diameter comparable to the overlaying NW [5]. The diameter can be further reduced by multiple O2 etching steps. Raman spectroscopy is used to characterise the structure of the resulting ribbons. Field-effect measurements show their transition from semi-metal to semiconductor[5].1. D. Whang, et al. Nano Lett. 3, 951 (2003)2. A. Colli et al. Nano Lett. 8, 1358 (2008)3. P. Beecher et al., J.Appl. Phys. 102, 043710 (2007)4. N. Y. Han et al. Phys. Rev. Lett. 98, 206805 (2007)5. A. Fasoli et al submitted (2009).
9:00 PM - K10.5
Optical Spectroscopy of Individual Single-Walled Carbon Nanotubes.
Brahim Lounis 1 , Silvia Santos 1 , Jonah Shaver 1 , Stephane Berciaud 1 , Laurent Cognet 1
1 , CNRS & Université Bordeaux, Bordeaux France
Show AbstractCurrent methods for producing single-walled carbon nanotubes (SWNTs) lead to heterogeneous samples containing mixtures of metallic and semiconducting species with a variety of lengths and defects. Optical detection at the single nanotube level offer the possibility to examine these heterogeneities provided that all SWNT types are equally well detected. Photothermal Heterodyne technique allows to perform highly sensitive imaging and absorption spectroscopy of individual small diameter SWNTs. Because it probes light absorption, the method enables identification of both semiconducting and metallic SWNTs. Using time–resolved and cw luminescence spectroscopy, the absorption cross section of highly luminescent individual single-walled carbon nanotubes is determined. A mean value of 10-17 cm2 per carbon atom is obtained for (6,5) tubes excited at their second optical transition, and corroborated by single tube photothermal absorption measurements. Biexponential luminescence decays are systematically observed, with short and long lifetimes around 45ps and 250ps. This intrinsic behavior is attributed to the band edge exciton fine structure with a dark level lying a few meV below a bright one. References1.Berciaud et al, Nano Letters, 7 (2007) 1203.2.Berciaud et al, Phys. Rev. Lett., 101, (2008) 077402 ; Duque et al, submitted
9:00 PM - K10.6
Resonant Raman Scattering of Individual C60 Double Wall Carbon Nanotubes with Inner Semiconducting Layers and Outer Metallic Layers.
Federico Villalpando-Paez 1 , Hiroyuki Muramatsu 2 , Yoong-Ahm Kim 2 , Daniel Nezich 1 , Morinobu Endo 2 , Mauricio Terrones 3 , Mildred Dresselhaus 1
1 , MIT, Cambridge, Massachusetts, United States, 2 , Shinshu University, Nagano Japan, 3 , IPICYT, San Luis Potosi Mexico
Show AbstractWe measured resonant Raman scattering from individual C60 double wall carbon nanotubes (C60-DWNTs) with inner semiconducting (6,5) layers and outer metallic layers belonging to family 2n+m=33. The inner and outer walls of the individual C60-DWNTs were simultaneously in resonance with the same laser energy. In comparison to previous experiments on DWNT bundles the obtained Raman spectra on individual C60-DWNTs show simplified radial breathing mode (RBM), G and G’ line shapes that allow us to study the inter layer interactions. We observe that DWNTs with smaller diameter inner layers might have smaller wall to wall distances.
9:00 PM - K10.7
Electronic Raman Scattering in Metallic Carbon Nanotubes.
Hootan Farhat 1 , Martin Kalbac 1 2 , Mildred Dresselhaus 1 , Jing Kong 1
1 , MIT, Cambridge, Massachusetts, United States, 2 , Academy of Sciences of the Czech Republic, Prague Czechia
Show AbstractThe asymmetric lineshape of the G-band in the Raman spectrum of metallic nanotubes is often attributed to a Fano interference between phonon and electron Raman scattering. The electronic contribution is presumed to be weak and featureless and has, to date, received little attention. Here we present measurements of the electronic contribution to the Raman spectrum and show that it is resonantly enhanced thus giving rise to a broad peak. Depending on the excitation energy, the position of the peak will overlap with different parts of the phonon Raman spectrum and, if not accounted for, can result in a misinterpretation of the lineshape of the G-band. We show that energy of the Raman scattered photons are centered around the optical transition energies of the metallic nanotube. Therefore the optical resonances of metallic nanotubes can be identified based on the electronic Raman spectrum.
9:00 PM - K10.8
Raman Spectroscopy of Chirality-Enriched Single Walled Carbon Nanotubes.
Stephen Doorn 1 , Juan Duque 1 , Erik Haroz 2 , Jun Kono 2 , Hang Chen 3 , Anna Swan 3 , Xiaomin Tu 4 , Ming Zheng 4
1 Chemistry Division, Los Alamos National Lab, Los Alamos, New Mexico, United States, 2 Department of Electrical and Computer Engineering, Rice University, Houston, Texas, United States, 3 Department of Electrical and Computer Engineering, Boston University, Boston, Massachusetts, United States, 4 Central Research and Development, DuPont, Wilmington, Delaware, United States
Show AbstractRecent advances in carbon nanotube separations science are providing access to samples highly enriched by metallicity and in single chiralities. We present examples of Raman spectroscopic investigations enabled by such enriched samples. Density gradient ultracentrifugation of nanotubes suspended in cosurfactant systems provide fractions enriched in armchair metallic chiralities. We present Raman characterization of the enrichment process. G-band data for spectroscopically isolated armchair chiralities show that the low frequency LO mode is absent for these structures. We also present resonance window behavior on G-band spectra for single chirality semiconducting species generated from ion chromatography of DNA-functionalized nanotubes. RBM, IFM, G, and G’ behavior in E22 and higher order excitations will also be discussed.
9:00 PM - K10.9
Resonant Raman Spectroscopy Study of Heat Treated Graphitic Nanoribbons.
Jessica Campos-Delgado 1 , Hootan Farhat 2 , Yoong Ahm Kim 3 , Alfonso Reina 2 , Morinobu Endo 3 , Jing Kong 2 , Humberto Terrones 1 , Mauricio Terrones 1 , Mildred Dresselhaus 2
1 Advanced Materials Department, IPICYT, San Luis Potosi, San Luis Potosí, Mexico, 2 EECS, DMSE, Department of Physics, MIT, Cambridge, Massachusetts, United States, 3 Faculty of Engineering, Shinshu University, Wakasato, Nagano, Japan
Show AbstractWe have carried out micro-Raman measurements of pristine and heat treated CVD-grown graphitic nanoribbons[1] at the bulk and individual scales.At the bulk level we have used seven different excitation laser energies to probe the changes induced by the thermal annealing, and quantify the dispersive behavior of the D-, and the G‘- bands. Our study at this level shows a progressive increase in order as a function of heat treatment temperature, confirmed by the ID/IG ratios and the FWHM of the G band.At the individual level, thanks to a computerized stage we have been able to perform line scans across isolated nanoribbons consisting of 4-6 measurements. Considering the spot size of the laser beam (~0.5 µm), this procedure allowed us to hit the sample mainly on the edges when the laser was far from the center of the nanoribbon. We demonstrate that the presence of symmetry-breaking elements concentrates mainly at the edges[2]. These results provide new information about the origin the D- and D’- bands on graphitic nanocarbons that contain highly curved domains after thermal annealing. [1] J. Campos-Delgado, et al. Chem. Phys. Lett. 469, 177, 2009[2] J. Campos-Delgado, et al. (submitted to Small)
Symposium Organizers
Kenji Hata Advanced Industrial Science and Technology (AIST)
Annick Loiseau Laboratoire d'Etude des Microstructures
Yoke Khin Yap Michigan Technological University
Ming Zheng National Institute of Standards and Technology
K11: Chemical and Biological Applications I
Session Chairs
Zhuang Liu
Michael Strano
Ming Zheng
Wednesday AM, December 02, 2009
Room 302 (Hynes)
9:30 AM - **K11.1
Structure and Binding Strength of CNT-recognizing DNA Sequences.
Anand Jagota 1 , Suresh Manohar 1 , Ming Zheng 2 , Dmitri Vezenov 3 , Constantine Khripin 1 , Xiaomin Tu 2
1 , Lehigh University, Bethlehem, Pennsylvania, United States, 2 MS&E/CR&D, The DuPont Company, Wilmington, Delaware, United States, 3 Chemistry, Lehigh University, Bethlehem, Pennsylvania, United States
Show AbstractMost DNA sequences bind strongly to carbon nanotubes (CNTs), dispersing them effectively in water. It has recently been discovered that certain DNA sequence motifs, comprising mostly of pyrimidines with an occasional purine base, are very effective at recognizing a particular type of CNT, allowing their clean separation from a mixture. We have proposed that the basis of recognition is the formation of an ordered DNA structure, stabilized by interactions between it and the underlying CNT. We show that antiparallel DNA strands can form an extended, hydrogen-bonded, sheet on graphite that is analogous to the well-known beta-sheet structure of polypeptides. Like the beta-barrel structure of polypeptides, this can be rolled into a barrel with discrete radii. For the poly(GT) sequence, we show that the proposed structure is consistent with mobility measurements using capillary electrophoresis. Measurements of the force required to peel a single DNA molecule off graphite have been used to quantify the sequence-dependent binding strength between the two. These measurements also suggest the formation of secondary structure in recognition sequences.
10:00 AM - K11.2
Amphiphilic Polyvinylpyrollidone-based Copolymers for Single-Walled Carbon Nanotube Wrapping.
Brian Popp 1 , Dillon Miles 1 , Zachary Ball 1
1 Dept. of Chemistry and the Richard E. Smalley Institute for Nanoscale Science and Technology, Rice University, Houston, Texas, United States
Show AbstractElectronically pristine single-walled carbon nanotubes (SWNTs) offer potential as sensors in biological and ecological environments. In order to exploit SWNTs for this purpose, a suitable “wrapping” agent (e.g., surfactant or polymer) is needed to provide a stable, robust encapsulation of the SWNT. One such polymer, polyvinylpyrrolidone (PVP), has been investigated previously; however, the PVP-SWNT supramolecular assembly is poorly stable in many environments and thus leads to irreversible flocculation of the SWNT. Utilizing vinylpyrrolidone monomers bearing environmentally responsive and chemically targetable functionality on the pyrrolidone ring, we have prepared a series of PVP-based copolymers utilizing radical addition-fragmentation chain-transfer (RAFT) polymerization methods. The effects of copolymer structure on SWNTs electronic properties and near-infrared fluorescence emission will be discussed.
10:15 AM - K11.3
Photoluminescence Brightening of Individual Single-Walled Carbon Nanotubes by Reducing Agents.
Xiaoyong Wang 1 , Andrea Lee 1 , Lisa Carlson 1 , Julie Smyder 1 , Ming Zheng 2 , Todd Krauss 1 3
1 Department of Chemistry, University of Rochester, Rochester, New York, United States, 2 , DuPont Central Research and Development, Wilmington, Delaware, United States, 3 Institute of Optics, University of Rochester, Rochester, New York, United States
Show AbstractSingle-walled carbon nanotubes (SWNTs) are tubular graphitic molecules with high aspect ratios and exceptional electronic and optical properties, such as the ability to be either metallic or semiconducting depending on their molecular structure. Single semiconducting SWNTs display remarkably stable and size-tunable photoluminescence at near-infrared (NIR) wavelengths, making them fundamentally interesting and technologically relevant materials. However, in water even the brightest SWNTs have a relatively poor photoluminescence quantum yield (QY) of ~1%, much less than other NIR emitting nanomaterials such as semiconductor quantum dots, which have QYs over 10 times larger than SWNTs. It is currently not understood whether the poor QY of SWNTs in water is an intrinsic property or the result of extrinsic quenching mechanisms indicative of non-optimal sample quality. Here we report the addition of reducing agents to an aqueous solution of SWNTs results in an enormous enhancement of the QY for individual SWNTs to unprecedented values of ~30%. The enhancement was reversible upon removal of the reducing molecules. When the SWNTs were deliberately oxidized using a hole donor, reducing agents were able to recover photoluminescence, suggesting photoluminescence intensity enhancement occurs through a reduction of defect sites on the NT sidewall. These unexpectedly high QY values indicate that SWNTs are intrinsically bright emitters, and that current understanding of the optical properties of SWNTs has largely been obtained from defective SWNTs having their photoluminescence partially quenched. The availability of a bright and steady source of NIR photons will greatly facilitate the development of new technology in several fields including biological imaging, quantum optics, and optoelectronics.
10:30 AM - K11.4
Stoichiometric Control of Carbon Nanotube Functionalization.
Alain Penicaud 1 , Damien Voiry 1 , Olivier Roubeau 2 1
1 CNRS-CRPP, University of Bordeaux, Pessac France, 2 Instituto de Ciencias de Materiales de Aragon-CSIC, Universidade de Zaragoza, Zaragoza Spain
Show AbstractCovalent grafting on carbon nanotubes has been a key step to yield metananotubes, i.e. nanotubes with functionnality such as hydrophilicity, light harvesting, sensor, catalysis and so on. Although many reported functionalization routes are known,[1] most involving highly reactive intermediates, stoichiometric control has rarely been obtained, while this latter point is fundamental for most applications using the extended π-system of CNTs. We report here that electrophilic addition on carbon nanotube salts [2] allow full control of the addend/C ratio.[3,4] Potassium salts of nanotubes have been synthetized, isolated and characterized with C/K ratio varying from ca 500 to 20. Addition of an electrophile to solutions of these salts of varying potassium/carbon ratio yield functionalized nanotubes where the C/addend ratio varies from ca 1000 to 60. Two series of functionalized tubes have been characterized by ATG and XPS, IR and Raman spectrometries, all showing stoichiometric control. The functionalized tubes are soluble in different organic solvents and absorption spectroscopy show that electronic transitions are still present. Applications of these series of functionalized tubes are currently under investigation.[1] C. A. Dyke, J. A. Tour, J. Phys. Chem. A 2004, 108, 11151 ; D. Tasis, N. Tagmatarchis, A. Bianco, M. Prato, Chem. Rev 2006, 106, 1105[2] A. Pénicaud, P. Poulin, A. Derré, E. Anglaret and P. Petit, J. Am. Chem. Soc. 2005, 127, 8.[3] O. Roubeau, A. Lucas, A. Pénicaud, A. Derré, J. Nanoscience and Nanotechnology 2007, 7, 1-5.[4] D. Voiry, O. Roubeau and A. Pénicaud, Submitted
10:45 AM - K11.5
Non-Covalent Functionalization as an Alternative to Oxidative Acid Treatment of Single Wall Carbon Nanotubes.
Trevor Simmons 1 2 3 , Justin Bult 2 , Daniel Hashim 2 4 5 , Robert Linhardt 1 6 7 , Pulickel Ajayan 2 3 4
1 Chemistry & Chemical Biology, Rensselaer Polytechnic Institute, Troy, New York, United States, 2 Material Science & Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States, 3 Rensselaer Nanotechnology Center, Rensselaer Polytechnic Institute, Troy, New York, United States, 4 Mechanical Engineering & Material Science, Rice University, Houston, Texas, United States, 5 Materiales Avanzados, Instituto Potosino de Investigacion Cientifica y Tecnologica, San Luis Potosi, San Luis Potosi, Mexico, 6 Chemical & Biological Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States, 7 Biology, Rensselaer Polytechnic Institute, Troy, New York, United States
Show AbstractWe have created stable dispersions of single wall carbon nanotubes (SWNTs) in water by employing a non-covalent functionalization scheme that allows carboxylic acid moieties to be attached to the SWNT surface by a π-π stacking interaction. Pyrenecarboxylic acid (PCA) is non-covalently attached to the surface of SWNTs and affords highly uniform and stable aqueous dispersions. This method was developed to provide a non-covalent alternative to the commonly used oxidative acid treatment functionalization of carbon nanotubes. This alternative strategy avoids the damage to the carbon nanotube structure inherent to oxidative acid treatments. Carbon nanotubes are commonly functionalized with oxidative acid treatment schemes to create polymer-nanotube composites and improve the adhesion between the polymer and carbon nanotubes. Composites of SWNTs and polycarbonate were prepared and tested to determine the effect of PCA on the adhesion of the SWNTs to the polymer matrix. These tests confirmed that PCA improved the SWNT-polycarbonate adhesion and improved the dispersion of the SWNTs throughout the matrix. This study demonstrates that stable dispersions of SWNTs can be achieved without substantial cutting, introduction of defects, or covalent modification, by employing a simple and effective non-covalent functionalization with PCA, with possible application to other advanced carbon materials such as graphene.
11:00 AM - K11:CBA1
BREAK
11:30 AM - **K11.6
DNA Sequence Motifs for Structure-Specific Recognition and Separation of Carbon Nanotubes.
Xiaomin Tu 1 , Ming Zheng 1
1 , DuPont Central Research and Development, Wilmington, Delaware, United States
Show AbstractSingle-walled carbon nanotubes (SWNTs) are fascinating one-dimensional carbon materials that are attractive for many fundamental studies and technological applications. In the past, DNA-based chromatographic SWNT separation has demonstrated its capability in obtaining nanotubes of uniform dimension and identical chirality that current synthesis can not provide. The exquisite resolution power of DNA approach is able to differentiate the minute difference in structure among nanotubes. Here, we identified a set of DNA sequences capable of purifying single-chirality nanotube species from a synthetic mixture through an effective search of a DNA library of 1060 in size. Each of the sequences recognizes a particular nanotube structure, enabling chromatographic purification of 12 major semiconducting species from HiPco tubes. The identified sequences are short and share a purine-pyrimidine pattern that can undergo hydrogen-bonding to form well-ordered three-dimensional barrels around selected nanotubes, allowing them to elute early. Fine tuning of the sequences, replacing one of the bases with another structurally similar purine or pyrimidine, improves the resolution of the purified tubes and offers the potential for more single-chirality species enrichment.
12:00 PM - K11.7
Brightly Fluorescent Single-Walled Carbon Nanotubes via an Oxygen-Excluding Flavin-Based Helical Organization.
Fotios Papadimitrakopoulos 1 2 3 , Sang-Yong Ju 1 2 , William Kopcha 1 3 , Darlington Abanulo 1 2 , Christopher Baddaluco 1
1 Nanomaterials Optoelectronics Laboratory, University of Connecticut, Storrs, Connecticut, United States, 2 Polymer Program, Institute of Materials Science, University of Connecticut, Storrs, Connecticut, United States, 3 Department of Chemistry, University of Connecticut, Storrs, Connecticut, United States
Show AbstractAttaining high photoluminescence quantum yields for single-walled carbon nanotubes (SWNTs) has been a challenging task that needs to be conquered in order to broaden their optoelectronics and sensing applications. Among various nonradiative pathways, sidewall chemisorption of oxygen provides a known defect for exciton quenching through nanotube hole doping. Recently, we have reported that flavin mononucleotide (FMN), the phosphorylated form of vitamin B2 seamlessly wraps around SWNTs (Nature Nanotech., 3, 356-362 (2008)), affording a simple methodology to impart an 85% chirality enrichment of (8,6)-single-walled carbon nanotubes. In this paper, we present that an aliphatic (dodecyl) analog of flavin mononucleotide, FC12, leads to high degree of nanotube individualization, which otherwise tend to aggregate into small bundles. Unlike other surfactants, the surface organization of FC12 is sufficiently tight to exclude oxygen from the SWNT surface, which led to quantum yields as high as 20% (Science, 323, 1319-1323 (2009)). Toluene-dispersed, FC12-wrapped nanotubes exhibited an absorption spectrum with ultrasharp peaks (widths of 12 to 25 milli–electron volts) devoid of the characteristic background absorption of most nanotube dispersions. The uniform and defect-free environment offered by the flavin organization, which is needed as a result of the large exciton diffusion length (~90 nm) (7) in SWNTs, opens an array of new frontiers in SWNT photophysics. Financial Support from AFOSR is kindly acknowledged.
12:15 PM - K11.8
Emission Saturation of Single-Wall Carbon Nanotubes via Modulation of Surfactant Interaction at the Nanotube Surface.
Juan Duque 1 , Crystal Densmore 1 , Stephen Doorn 1
1 Physical Chemistry and Applied Spectroscopy , Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show AbstractThe optical properties of single-walled carbon nanotubes (SWNTs) offer great promises. However, the realization of their potential is limited by polydispersity and the degree to which the SWNTs are individually suspended and isolated from their immediate surroundings. This has been accomplished in the literature by altering the surfactant system.1,2 The SWNT/surfactant hybrid undergoes a complex dynamic process that involves constant adsorption and desorption of surfactant molecules onto the SWNT surface; this dynamic process can be affected by the SWNT chirality, presence of electrolytes, and many other extrinsic factors which create changes in the adsorbate density around the tubes. This will, in turn, lead to changes in the emission properties of the SWNTs and alter the ability to separate SWNTs via density gradient separation (DGS).3-5 In this work we study how addition of electrolytes and changes in surfactant concentration affects SWNT/surfactant interactions. Electrolyte modulation via salt addition enhances the nanotube optical properties and the ability to achieve separation via DGS. More precisely, we show that at low surfactant load addition of salts increases the surfactant density at the nanotube surface, effectively blushifting, narrowing, and enhancing the absorbance and emission of SWNTs. These optical changes are shown to be highly dependent on SWNT chirality with eventual aggregation at high salt addition. The manipulation of the SWNT/surfactant unit by controlled salt addition also improves the diameter-dependent separation of highly enriched metallic and semiconducting fractions. However, it should be noted that these phenomena are not universal for all SWNT surfactant concentrations; at high surfactant concentration minimal optical changes are observed after salt addition and no significant separation is obtained; suggesting that at high surfactant load the SWNT surface have an optimal surfactant density. Importantly, we observed that surfactant saturation via salt addition is different for different anionic surfactants and/or surfactant mixtures with negligible optical changes and minimal separation indicating different packing densities. In addition, we show photophysical measurements of highly enriched fractions of SWNTs to illustrate the strong interactions which occur with their surroundings.References1.Bachilo, S. M., et al. Science 2002, 298, (5602), 2361-6.2.O'Connell, M. J., et al. Science 2002, 297, (5581), 593-6.3.Duque, J. G., et al. J. Am. Chem. Soc. 2008, 130, (8), 2626-2633.4.Niyogi, S., et al. J. Am. Chem. Soc. 2007, 129, (7), 1898-1899.5.Niyogi, S., et al. J. Am. Chem. Soc. 2009, 131, (3), 1144-1153.
12:30 PM - K11.9
Electrochemistry of Carbon Nanotubes Containing Single Point Defects and Single Palladium Nanoparticles.
Vaikunth Khalap 1 , Tatyana Sheps 1 , Alexander Kane 1 , Philip Collins 1
1 Physics and Astronomy, Univ. of California, Irvine, Irvine, California, United States
Show AbstractSingle-walled carbon nanotubes (SWNTs) provide a pristine and edge-free surface for studying fundamental chemical processes of importance to all carbon electrodes. Here, we describe ongoing electrochemical experiments testing electron transfer rates on both pristine SWNTs and at individual point defects located on SWNT sidewalls. We have recently demonstrated electrochemical techniques for successfully creating such defects [1], tailoring them to have different functionalities [2], and labeling them for quantitative analysis [3].This combination of tools provides acute, atomistic control over complex systems relevant to electrochemistry and catalysis. For example, we have completed a series of cyclic voltammetry experiments using common redox couple on isolated SWNTs with and without oxygen-containing defect functionalities. Furthermore, similar experiments were performed using single Pd nanoclusters attached to both pristine SWNTs and those with defect sites. We can clearly demonstrate the importance of the defect support on the metal particle’s activity. Conversely, the Pd decorated defect has an enormous impact on the SWNT conductivity, with an inherent hydrogen gas sensitivity that makes the devices competitive commercial hydrogen sensors. These systems represent the irreducible element important for understanding bulk, carbon electrodes decorated by this catalytically relevant material.[1] B. Goldsmith et al, Science 315 77 (2007)[2] J. Coroneus et al, ChemPhysChem 9 1053 (2008)[3] Y. Fan et al, Nature Materials 4 906 (2005)
12:45 PM - K11.10
Interactions of DNA Wrapped Single Wall Carbon Nanotube (SWCNT) with Collagen as Model Biological Substrate: An SPR Study.
Jung Park 2 1 , Jeffrey Fagan 2 , Ji Huh 2 , Alamgir Karim 3 2 , Kalman Migler 2 , Dharmaraj Raghavan 1 2
2 Polymers Division, National Institute of Standards & Technology, Gaithersburg, Maryland, United States, 1 Chemistry, Howard University , Washington, DC 20059, District of Columbia, United States, 3 Polymer Engineering, University of Akron, Akron, Ohio, United States
Show AbstractThe adsorption behavior of SWCNT on the extracellular matrix protein collagen has been investigated as a model biological template for understanding biological surface - nanomaterial interactions. Both purified and length sorted SWCNTs, individually dispersed with 30-mer 5’-GT(GT)13GT-3’ single-stranded DNA, were studied to measure the characteristics of the interactions. Formation of the collagen layer and the SWCNT adsorption process were sequentially performed in a microfluidic environment that allowed for controlled variations of parameters on a common substrate, and the time-dependent adsorption was characterized by surface plasmon resonance imaging (SPR). Adsorption kinetics for the dispersed SWCNTs were measured over a range of SWCNT concentrations, pH values, and model biological environments; analysis of the resulting curves allowed for determination of the diffusion or reaction limited adsorption process as a function of SWCNT concentration. In pH 7.4 HEPES buffer the interaction between the DNA wrapped SWCNT and the collagen layer was found to be irreversible, but modifiable to an extent by exposure of the surface to unbound single stranded DNA prior to SWCNT exposure. The effect of varying solution pH (5.5 – 10) on the adsorption was also investigated in order to gain insight into the role of electrostatic interactions between the SWCNTs and the collagen layer, in which the abundant amine component of collagen has an apparently large effect. The combination of the multiple microfluidic channels and the SPR imaging enables controlled and parallel measurements of the SWCNT adsorption to the collagen layer.
K12: Vertically Aligned Growth
Session Chairs
Wednesday PM, December 02, 2009
Room 302 (Hynes)
2:30 PM - K12.1
General Rules Governing the Highly Efficient Growth of Carbon Nanotubes.
Don Futaba 1 , Jundai Goto 1 , Satoshi Yasuda 1 , Takeo Yamada 1 , Motoo Yumura 1 , Kenji Hata 1
1 Nanotube Research Center , AIST, Japan, Tsukuba, Ibaraki, Japan
Show AbstractIn water-assisted chemical vapor deposition (CVD), the addition of a growth enhancer, e.g. water, to the ambient of normal hydrocarbon CVD dramatically improved growth efficiency resulting in vertically aligned forests [1]. Here, we present a generalized picture of water-assisted chemical vapor deposition (Super-growth) by demonstrating that highly efficient growth of carbon nanotubes (CNTs) is possible using, essentially, a countless number of growth enhancers, e.g. alcohols, ethers, esters, ketones, aldehydes, and even carbon dioxide. Importantly, we uncovered the general rules governing the highly efficient growth of carbon nanotubes and the fundamental reasons from which they arose. Specifically, we found that the key for highly efficient growth is to include two essential ingredients in the growth ambient: a carbon source not containing oxygen and a minute quantity of a secondary gas, i.e. growth enhancer, containing oxygen. Exclusively for all combinations of carbon sources and growth enhancers following these rules, we could achieve highly efficient growth. [1] K. Hata et al, Science, 306, 1241 (2004).
2:45 PM - K12.2
Growth Kinetics of Carbon Nanotube Forests.
Tobias Wirth 1 , Can Zhang 1 , Guofang Zhong 1 , Stephan Hofmann 1 , John Robertson 1
1 Engineering, University of Cambridge, Cambridge United Kingdom
Show AbstractIn this study [1] we suggest a fundamental step in the catalytic growth process of carbon nanotubes (CNTs) arrays. The basic question whether the growth is gas-diffusion controlled or kinetically controlled is generally difficult to solve. We have studied a widely used model catalyst system: Al2O3-supported Fe and its reaction with acetylene (C2H2). It is of general interest to understand its catalytic activity, especially to obtain eventually growth selectivity. Two very important parameters for the nucleation of CNTs are (i) the partial pressure of the carbon precursor and (ii) the temperature at which growth is performed. We extracted activation energies for a pressure range of 5 orders of magnitude and a pressure dependence of the growth rate for 7 orders of magnitude respectively. We conclude that a reaction-rate limited mechanism for the growth of CNT arrays is based on C-C bond breaking of absorbed C2 species rather than the previously suggested diffusion limit. In addition, we also present high resolution real-time optical imaging. The high quality videos enable insights into the in-situ growth of CNT arrays.[1] CT Wirth, C. Zhang, G. Zhong, S. Hofmann, J. Robertson, ACS Nano, submitted (2009)
3:00 PM - K12.3
Synthesis of Centimeter Long Vertically Aligned Single-Walled Carbon Nanotubes by Remote Plasma in Low Pressure Beyond the Atmospheric Pressure Synthesis.
Ryogo Kato 1 , Hiroshi Kawarada 1
1 , Waseda University, Shinjuku-ku Japan
Show Abstract "We have succeeded in enhancing the growth rate of SWNTs without sacrificing catalyst conversion ability in a remote plasma deposition. Normally SWNT length was been limited to 2-3 mm because of catalyst life time. In this work the SWNTs growth rate at 60 Torr in a remote plasma increases to 3mm/h, which is 10 times higher in the SWNTs growth rate (270μm/h )[1] at lower pressure (20Torr) in the same remote plasma and is comparable with the growth rate of SWNTs by the water-assisted synthesis method at the atmospheric pressure [2] We have achieved the enhanced growth rate of SWNTs by raising microwave power and total gas pressure up to 60 Torr. The maximum length of SWNTs is 7.5mm after 2.5 h deposition and can be extended to centimeters because the catalyst particles preserving high conversion ability[3,4] because water vpaour has not been introduced." "Si substrates are coated with a sandwich-like structure Al2O3 /Fe /Al2O3 (/Si). Al2O3 between Si and Fe is a buffer layer to suppress the interdiffusion On the other hand, Al2O3 above the Fe film works as a barrier of the surface diffusion of catalytic atoms so that the aggregation of Fe atoms can be controlled during the pre-heating time. As a result, high dense catalytic particles can be formed and extremely dense and vertically aligned SWNTs can be synthesized. The substrate was heated up to 690°C within a few minutues by an induction heater to form catalytic nanoparticles, and then plasma was turned on in a gas mixture of H2 and CH4 for the growth of SWNTs. The microwave power and total gas pressure were 120W and 60Torr, respectively. Synthesized samples were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and micro-Raman spectroscopy." "We can control the diameter and layer number of CNTs by adjusting thickness of Fe films and Al2O3 films. Specifically, SWNTs are grown at below 0.5 nm in Fe film thickness. From the result of Raman spectroscopy of as-grown vertically aligned SWNTs(Fe film thickness 0.2-0.5nm), our SWNTs have diameters of 0.8-1.2nm and High G- to D-peak ratio which indicates the high quality of our SWNTs despite high growth rate synthesis." "[1] G. Zhong, H.Kawarada et al., Jpn. J. Appl. Phys., 44, 1558 (2005).[2] K. Hata et al., Science 306, 1362 (2004).[3] G. Zhong, H.Kawarada et al., J. Phys. Chem. B, 111, 1907 (2007).[4] T. Iwasaki, H.Kawarada et al., Nano Lett. 8, 886 (2008)."
3:15 PM - K12.4
Control of Source Gases and Underlayer for Low-Temperature Synthesis of Dense Carpets of Vertically-Aligned Carbon Nanotubes on Metallic Substrates for Interconnect Applications.
Gilbert Nessim 1 , Matteo Seita 2 , Donatello Acquaviva 3 , Desiree Plata 6 , Kevin O'Brien 5 , A. John Hart 4 , Robert Mitchell 1 , Carl Thompson 1
1 Materials Science and Engineering, MIT, Cambridge, Massachusetts, United States, 2 Lab. for Nanometallurgy, Dept. of Materials, ETH Zurich, Zurich Switzerland, 3 Laboratory of Micro and Nanoelectronics Devices (LEG2), Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne Switzerland, 6 Civil and Environmental Engineering, MIT, Cambridge, Massachusetts, United States, 5 Components Research Department, Intel Corporation, Hillsboro, Oregon, United States, 4 Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, United States
Show AbstractCarbon NanoTubes (CNTs) have been extensively investigated as ideal replacements for copper interconnects for integrated circuit nodes below 22nm. Although CNT material properties are recognized as superior to copper for this application, the ability to grow high density carpets of vertically aligned, crystalline CNTs on metallic substrates at the low temperatures compatible with CMOS fabrication remains the major hurdle for their implementation in mass-manufacturing.New Processes were developed for growth of micron-tall, vertically-aligned, dense carpets of CNTs on various metallic underlayers using thermal Chemical Vapor Deposition at temperatures below 500°C. This was accomplished through hydrocarbon gas pre-heating that allowed CNT growth in a second lower temperature substrate zone, and by the appropriate choice of the underlayer material and its thickness. By varying the gas pre-heating temperature, we observed significant differences in CNT growth, both in terms of the carpet height and density, as well as in crystallinity of the CNTs. We systematically analyzed the gases produced by the decomposition of ethylene and cross-referenced their concentration with the CNT carpets obtained for various pre-heat temperatures. The gas analysis points to a few gas candidates that are critical for CNT growth. This is a first step in the direction of identifying the specific hydrocarbon gases that allow growth on metallic substrates at low temperatures.The choice of the underlayer material and thickness was also found to be critical as catalyst-underlayer alloying and catalyst diffusion to and through underlayer grain boundaries hinder CNT growth. We consistently obtained vertically-aligned CNT carpets using underlayers with high melting temperature (e.g., Ta) where their grain sizes remained below 100nm during the thermal process. We also obtained vertically-aligned growth on thin Pd underlayers as their small grains led to a high density of catalyst particles. However, use of thick Pd layers led only to entangled CNT growth because the catalysts density was too low for vertical CNT growth as they decorated the micron-size Pd grain boundaries. The examples presented will show how appropriate source gas preheating and choice of underlayer material and thickness are promising techniques for future use of carbon nanotubes in CMOS fabrication.
3:30 PM - K12:CGrowth4
BREAK
K13: Chemical and Biological Applications II
Session Chairs
Wednesday PM, December 02, 2009
Room 302 (Hynes)
4:00 PM - **K13.1
Single Molecule Biodetection Using Single Walled Carbon Nanotube Optical Sensors.
Michael Strano 1
1 , MIT, Cambridge, Massachusetts, United States
Show AbstractCarbon nanotubes, like inorganic nanowires, are materials were electrons are confined to a single physical dimension, resulting in new and unusual properties. Our laboratory has been focused on understanding their chemistry and on engineering 1D materials for applications specifically in biodetection. Nanoscale sensing elements offer promise for single-molecule analyte detection in physically or biologically constrained environments. Single-walled carbon nanotubes (SWNT), as optical sensors, offer unique advantages such as photostable near-infrared (n-IR) emission for prolonged detection through biological media and single-molecule sensitivity. We demonstrate detection of single molecule H2O2 signaling from Epidermal Growth Factor Receptor using fluorescent single-walled carbon nanotubes. An emerging concept in cell signaling is the natural role of reactive oxygen species, such as hydrogen peroxide (H2O2), as beneficial messengers in redox signaling pathways. Despite growing evidence, the nature of H2O2 signaling is confounded by the difficulty in tracking it in living systems both spatially and temporally at sub-nanomolar concentrations. In this work, we demonstrate a platform for selectively measuring the H2O2 efflux from living cells at the single molecule level. An array of near infrared fluorescent single walled carbon nanotubes is capable of recording the discrete, stochastic quenching events that occur as H2O2 molecules are emitted from individual A431 human epidermal carcinoma cells in response to epidermal growth factor (EGF). We show mathematically that such detection arrays have the unique property of distinguishing between molecules originating near the membrane from those with no memory of origination, or background. We find that EGF induces on average 0.04 nmol H2O2/min/active receptor over a period of 50 min after exposure to EGF. This platform promises a new approach to understanding reactive oxygen signaling at the cellular level.
4:30 PM - K13.2
High-performance Nanotube Sensor Arrays.
Fei Wang 1 , Timothy Swager 2
1 Materials Science and Engineering, MIT, Cambridge, Massachusetts, United States, 2 Chemistry, MIT, Cambridge, Massachusetts, United States
Show AbstractHerein we report a chemiresistor array using chemically modified carbon nanotubes that can orthogonally detect a series of organic vapors. Our group recently developed a highly efficient zwitterion-mediated modular transformation method of nanotubes. Recognition groups can be further installed to these nanotubes via 1,3-dipolar cycloaddition, metathesis, or thiol addition reactions. We will describe in detail the versatile nanotube chemistry and the rational design of recognition groups. Examples of recognition groups include calixarene for the detection of aromatic molecules via host-guest chemistry and hexafluoroisopropanol for the detection of tetrahydrofuran via H-bonding. We will also discuss the sensing process, investigation of sensing mechanisms, and the comparison with nanotube/polymer based sensors. We believe this approach can lead to the realization of nanotube based “smart-noses”.
4:45 PM - K13.3
Nanoscale Carbon Probes for Single Cell Interrogation.
Riju Singhal 1 , Zulfiya Orynbayeva 2 , Sayan Bhattacharyya 1 , Gary Friedman 3 , Yury Gogotsi 1
1 Materials Science and Engineernig, Drexel University, Philadelphia, Pennsylvania, United States, 2 Biochemistry and Molecular Biology, Drexel University, Philadelphia, Pennsylvania, United States, 3 Electrical and Computer Engineering, Drexel University, Philadelphia, Pennsylvania, United States
Show AbstractCellular and sub-cellular interrogation requires tools that have sub-micrometer diameters and can penetrate a cell membrane easily, cause minimal harm to the intracellular environment, and effectively carry out a specific operation. In the past, such studies have been attempted by means of glass pipettes of sufficiently small dimensions. However, these pipettes suffer from low mechanical strength and brittleness of glass. Therefore, they had limited success in cellular probing. Meanwhile, carbon nanotubes have found numerous applications where superior electrical and mechanical properties were desired. Moreover, the chemically inert nature of carbon under a large range of experimental conditions makes it a suitable candidate for biomedical applications. Here we demonstrate pipettes with tips of carbon having the diameters ranging from tens to hundreds of nanometers. In the first method, non-catalytic chemical vapor deposition (CVD) of methane was employed to deposit carbon on quartz pipettes. Different reaction conditions were applied to obtain the desired carbon thicknesses inside and (or) outside the quartz pipettes. A large variety of carbon probes were fabricated having different carbon configurations. These were then post processed to yield carbon-tipped nanopipettes. Another fabrication method involved assembly of individual carbon nanotubes at the tips of individual glass pipettes by employing fluid flow and sealing the junctions with epoxy to yield carbon nanotube-tipped pipettes. Nanotubes of different diameters (50, 100 and 200 nm), with ordered and disordered wall structure and various surface functionalities can be utilized for this purpose to yield multi-functional cellular endoscopes of desired diameters and with the required mechanical and electrical properties. These probes were shown to be highly efficient and minimally invasive while carrying out studies involving cell piercing. The synthesis parameters in each fabrication method have been varied to yield a large variety of nanopipettes useful for cell injection, intracellular sensing and interrogation.
5:00 PM - K13.4
Biomimetic Color Detection Using Chromophore-Nanotube Hybrid Devices.
Xinjian Zhou 1 , Thomas Ziefer 1 , Bryan Wong 1 , Karen Krafcik 1 , Andrew Vance 1 , Francois Leonard 1
1 , Sandia Nationa Laboratories, Livermore, California, United States
Show AbstractWe present a nanoscale color detector based on a single-walled carbon nanotube functionalized with azobenzene chromophores, where the chromophores serve as photoabsorbers and the nanotube as the electronic read-out. By synthesizing chromophores with specific absorption windows in the visible spectrum and anchoring them to the nanotube surface, we demonstrate the controlled detection of visible light of low intensity in narrow ranges of wavelengths. Our measurements suggest that upon photoabsorption, the chromophores isomerize from the ground state trans configuration to the excited state cis configuration, accompanied by a large change in dipole moment, changing the electrostatic environment of the nanotube. We will also present our all-electron ab initio calculations that are used to study the chromophore-nanotube hybrids and show that the chromophores bind strongly to the nanotubes without disturbing the electronic structure of either species. Calculated values of the dipole moments support the notion of dipole changes as the optical detection mechanism.
5:15 PM - K13.5
Durable Glucose Biosensors Based on Vertically-Aligned Multi-Walled Carbon Nanotubes.
Archana Pandey 1 , Jason Moscatello 1 , Abhishek Prasad 1 , Yoke Khin Yap 1
1 , Michigan Technological University, Houghton, Michigan, United States
Show AbstractIn 2007, the CDC estimates 7.8% of the US population had diabetes, and the percent is rising [National Diabetes Fact Sheet, Centers for Disease Control and Prevention, U.S. Department of Health (2007)]. Such high numbers lead to a large demand for highly selective, sensitive glucose sensors; the answer to this demand may be in nanomaterials. It has been reported that arrays of polymer embedded Multi-Walled Carbon Nanotubes (MWCNTs) can be modified to fabricate glucose sensors [1]. However, the full performance of these devices is still not known. Here we present wide characterization of these devices, with results on the detection limits, measurement stability and sensor lifetime. Vertically aligned (VA) MWCNTs were grown using a plasma enhanced chemical vapor deposition technique [2]. These VA-MWCNTs were then dip-coated by Poly Methyl Methacrylate (PMMA) followed by annealing at ~100 °C. Samples were then mechanically polished to expose and open the MWCNT tips. The exposed tips of these nanoelectrode ensembles were then immobilized with the biological molecule Glucose Oxidase (GOx) using the reported procedure [1]. These glucose biosensors present a high sensitivity of 0.15 µA mM−1cm −2 to glucose in the range of 1 mM to 1.5 mM with a response time of less than 10 s and a detection limit of 3.8 µM at a signal/noise ratio of 3. The sensors can continuously detect glucose molecules for at least 24 hours and can be reused for longer than eight months when kept in proper storage conditions. The details of these results will be presented in the meeting.[1] Lin et. al., Nanoletters 4 (2004) 191.[2] Menda et al., Applied Physics Letters 87 (2005) 173106. Yoke Khin Yap acknowledges supports from the Defense Advanced Research Projects Agency (Contract number DAAD17-03-C-0115 through the U.S. Army Research Laboratory), USDA (2007-35603-17740), and the Multi-Scale Technologies Institute (MuSTI) at Michigan Tech.
5:30 PM - K13.6
Programmable Transdermal Drug Delivery Utilizing Electroosmotic Flow within Carbon Nanotubes Membranes.
Ji Wu 1 , Caroline Strasinger 2 , Audra Stinchcomb 2 , Bruce Hinds 1
1 Chemical and Materials Engineering, University of Kentucky, Lexington, Kentucky, United States, 2 Pharmaceutical Science, University of Kentucky, Lexington, Kentucky, United States
Show AbstractProper treatment of drug addiction and abuse is critically important since it is estimated that the total overall costs of substance abuse in the United States exceed half a trillion dollars annually as reported by National Institute on Drug Abuse (NIDA). Conventional transdermal patches can provide a constant flux of drug in an easy and non invasive way. However many treatments, such as nicotine, fentanyl and clonidine, require variable rates of transdermal delivery. Membranes made of carbon nanotubes possess many advantageous attributes that include: 1) atomically flat graphite surface allows for ideal fluid slip boundary conditions 100,00 times faster than conventional pores 2) the cutting process to open CNTs inherently places functional chemistry at CNT core entrance to act as chemical gatekeepers and 3) CNT are electrically conductive allowing for electrochemical reactions and application of electric fields gradients at CNT tips. Thus CNT membranes are and ideal candidate to have a voltage controlled membrane as the active element in a transdermal drug delivery device. CNT membranes were functionalized with highly-charged anionic dye molecules to induce a highly efficient electroosmotic flow. The anionic charge density on CNTs was first enhanced through diazonium electrochemical modification followed by a quad-anionic dye amine functionalization. It was found that fluxes of both cationic and neutral molecules through the CNT membrane have been greatly increased under negative biases. High electro-osmotic flows of 0.05 cm/s at -300mV bias have been observed with 15% ion efficiency. Electro-osmosis within CNT membranes is strongly related to electric field strength, ionic strength and surface charge density. Employing this phenomenon, the delivery rate of clonidine was enhanced by more than 4 times under -300 mV bias compared to the rate at +300 mV bias. The rate was be increased from 2.8 to 13.8 nano-mole/hr-cm2, which matches the traditional five day opioid withdrawal symptom treatment that requires variable delivery rates ranging from 1.7 to 5.4 nano-mole/hr.cm2. Voltage controlled dosing across human skin samples is also demonstrated.
5:45 PM - K13.7
Transport of Individual Ions Through the Interior of Perfectly Aligned Single Walled Carbon Nanotubes.
Chang Young Lee 1 , Jae-Hee Han 1 , Michael Strano 1
1 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractTheories predict that single walled carbon nanotube (SWNT) can be a fast molecular transporter due to its atomically smooth surface where molecular corrugation is minimized by high density of carbon atoms. Molecular dynamics simulation estimates the velocity of water and small molecules through the interior of carbon nanotubes to be several orders of magnitude higher than the value predicted by continuum hydrodynamics. Experimentally the velocity of water through the nanotubes was measured using 1) multi-walled carbon nanotubes where the pore size is significantly larger than the individual water molecules, or 2) thin membranes of double/single-walled carbon nanotubes from which only ensemble measurements can be made. However, none to date have studied how a single molecule is transported through individual single walled carbon nanotubes.In this work we have grown an array of perfectly aligned SWNT using chemical vapor deposition for the study of molecular transport of water and ions through the interior of nanotubes. An electric field is applied across two reservoirs of ionic solution connected by the aligned nanotubes with open ends. We find that the ionic solutions can be transported from one reservoir to the other along the nanotubes. Formation of salt crystals along the nanotube surface proves that the transport is through the exterior. By blocking the exterior, however, we were able to demonstrate the first experimental evidence of single ion transport through the interior of individual single walled carbon nanotubes. The trace of ion current through the nanotubes exhibits stochastic pore-blocking events with characteristic dwell time of individual ions. The transport of each ion is highly coordinated with the transport of the next ion resulting in an oscillation of the ion current. We have performed rigorous statistical analysis of the dwell time and the frequency of the pore-blocking events for various ions in order to understand the mechanism. Our results give direct answers to several critical questions that many researchers have speculated about for decades, and will be the basis of future application of carbon nanotubes as molecular conduits.
K14: Poster Session: Chemical and Biological Processing and Application
Session Chairs
Thursday AM, December 03, 2009
Exhibit Hall D (Hynes)
9:00 PM - K14.1
Field-effect Biosensors Using Carbon Nanotubes Multilayers as Gate Material.
Jose Siqueira 1 2 3 , Valtencir Zucolotto 1 , Arshak Poghossian 2 3 , Osvaldo Oliveira 1 , Michael Schoening 2 3
1 Physics Institute of São Carlos, University of São Paulo, São Carlos Brazil, 2 Institute of Nano- and Biotechnologies, Aachen University of Applied Sciences, Juelich Germany, 3 Institute of Bio- and Nanosystems (IBN2), Research Centre Juelich, Juelich Germany
Show AbstractThe integration of carbon nanotubes and biological compounds into electrical devices has been exploited in developing new biosensing concepts. In this study, we introduce the fabrication of two types of field-effect-based sensors, namely a capacitive electrolyte-insulator-semiconductor (EIS) structure and a light-addressable potentiometric sensor (LAPS) modified with layer-by-layer films of single-walled carbon nanotubes alternated with polyamidoamine dendrimers. The capacitive EIS sensor was characterized with the capacitance-voltage and constant-capacitance-mode methods, while for the LAPS device use was made of current–voltage and constant-current mode measurements. The formation of PAMAM/SWNT LbL films was analyzed through scanning electron microscopy (SEM) and atomic force microscopy (AFM), whose images displayed a highly porous nanofilm owing to the interpenetration of the SWNTs-network into the dendrimers layers. The biosensing ability of the devices was tested for penicillin G via adsorptive immobilization of the enzyme penicillinase atop the PAMAM/SWNT LbL film. For both architectures a limit of detection of ca. 5.0 x 10-6 mol L-1 was achieved. We noted that the incorporation of PAMAM/SWNT LbL films onto the surface of the EIS and LAPS structures led to sensors with enhanced performance, as the devices exhibited higher sensitivity and stability, small drift and fast response time, in comparison to the corresponding unmodified structures. The improved performance was associated with the nanofilm architecture, as the porous structure with larger active surface area in the PAMAM/SWNT films allowed a better distribution and adsorption of penicillinase, and a faster H+-ion penetration through the film. These results amount to a proof-of-concept for the potential application of CNT-LbL structures in field-effect-based biosensors, which are amenable to the integration of a biological recognition element into the well-established silicon device technology.
9:00 PM - K14.10
Potential of Mean Force between Aqueous Single Walled Carbon Nanotubes in Surfactant Solutions.
Naga Rajesh Tummala 1 , Brian Morrow 1 , Peter Luo 1 , Alberto Striolo 1
1 School of Chemical Biological and Materials Engineering, University of Oklahoma, Norman, Oklahoma, United States
Show AbstractMolecular dynamic simulations were conducted to calculate the effective potential of mean force (PMF) between two (6,6) SWNTs in the presence of aqueous surfactants at room conditions. In an effort to relate the surfactant structure to effective CNT-CNT interactions in aqueous solutions, the surfactants considered include sodium dodecyl sulfate (SDS) and flavin mononucleotide (FMN) surfactants.In the absence of surfactants our results show, as expected, a strongly attractive SWNT-SWNT PMF at short nanotube-nanotube separations. The presence of surfactants modulates the PMF profile, as detailed by the results presented herein. In the case of SDS we employed two surface densities adsorbed on the (6,6) SWNTs to calculate the PMF as a function of nanotube-nanotube distance. Restricted to the conditions considered, we found that the potential of mean force does not depend significantly on the SDS surface density. In both cases, the PMF shows a long-ranged weak repulsion between the SWNTs in the presence of the surfactants, coupled to strong attractive and repulsive regions when the SWNTs are close to each other. Unfortunately, the repulsive peak is not strong enough to prevent the aggregation of carbon nanotubes, probably because of the large mobility of SDS surfactants adsorbed on (6,6) SWNTs. Because FMN surfactants, the phosphorilated form of vitamin B2, contain an aromatic isoalloxazine moiety and a chiral phosphate group, they couple more tightly with the SWNTs and yield a much more pronounced repulsive force between approaching SWNTs than that observed in the presence of SDS. Our results will help us identify the surfactant properties that allow us to manipulate nanotube-nanotube effective interactions. This is the key for designing nanotube-specific dispersing agents.
9:00 PM - K14.11
Thermoresponsive Control of Carbon Nanotube Stabilization and Exfoliation.
Krishna Etika 2 , Jaime Grunlan 1 2
2 Materials Science and Engineering, Texas A&M University, College Station, Texas, United States, 1 Mechanical Engineering, Texas A&M University, College Station, Texas, United States
Show AbstractDespite their immense potential, the ability to control the dispersion and microstructure of carbon nanotubes remains a hurdle for their widespread use. Stimuli-responsive polymers show conformation changes with applied external stimulus (pH, temperature, light etc.). Previously we demonstrated the ability to tailor nanotube exfoliation and stabilization using poly(acrylic acid) and pH as the stimulus. In the present work, temperature responsive polymers based on poly(N-cyclopropylacrylamide) [PNCPA] with varying amounts of pyrene functionality (p-PNCPA), were used to disperse single-walled carbon nanotubes (SWNT) in water. Pyrene associates strongly with SWNT due to π-π stacking along the sidewalls. Using p-PNCPA, containing 5 mol% pyrene, aqueous SWNT suspensions transitioned from Newtonian behavior at 10oC to highly shear thinning at 50oC. The lower critical solution temperature (LCST) of this polymer is approximately 30oC, above which the polymer normally settles out of solution in the absence of the nanotubes. The SWNT are much more bundled and networked at the higher temperature, as evidenced by cryo-TEM images. This is likely due to the polymer chain adopting a more globular structure as it becomes less hydrophilic and thereby interacts more weakly with the nanotubes. Composites generated by drying these suspensions at low and high temperature revealed an order of magnitude difference in electrical conductivity. Higher conductivity is associated with higher temperature because the nanotubes are less influenced by the polymer and better able to intimately contact one another. This type of temperature-controlled dispersion and behavior of carbon nanotubes could have a variety of applications in nanoelectronics, sensing, and drug delivery.
9:00 PM - K14.12
Detection of Protein via Gold Nanoparticle-Antigen Conjugates in Carbon Nanotube Field Effect Transistors.
Shun Mao 1 , Ganhua Lu 1 , Kehan Yu 1 , Junhong Chen 1
1 Department of Mechanical Engineering, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin, United States
Show AbstractBiological sensing generally relies on optical, electrochemical, and piezoelectric technologies. Although these technologies are relatively easy and reliable for molecular detection and in vitro diagnostics, they have limited sensitivity for low concentration analytes (typically in µM range) and are difficult to miniaturize. Nanomaterials, especially carbon nanotubes (CNTs) with all atoms on their surface have been demonstrated for biomolecular sensing. Field effect transistors (FETs) based on semiconducting carbon nanotube have also been used as biosensors. CNT-based FET devices are extremely sensitive to variations in the surrounding environment because all the electrical current flows through the most out layer of the CNTs which are typically located on the surface of the supporting substrate for direct contact with the analyte. Here, we successfully demonstrate electrical detection of protein binding via the introduction of Au nanoparticle-antigen conjugates to the surface of CNTs in CNT field effect transistors (CNTFETs). Antibody (horseradish peroxidase) and antigen (anti-horseradish peroxidase) binding events leading to the amplitude change in the drain current of the CNTFET can be sensitively detected by FET measurements. Immunoglobulin G (IgG) is used as a mismatched protein to verify the specificity of the biosensor; and nonspecific binding of protein with the sensing element is blocked by bovine serum albumin (BSA). The CNTFET-based biosensor could be adapted to detection of a variety of proteins for in vitro diagnostics.
9:00 PM - K14.14
Thermodynamically Stable, Size Selective Solubilization of Carbon Nanotubes in Aqueous Media by Self-assembly with Amphiphilic Block Copolymers.
Ramanathan Nagarajan 1
1 , Natick Soldier R D & E Center, Natick, Massachusetts, United States
Show AbstractTwo molecular modes of amphiphilic block copolymer-carbon nanotube interactions have been identified in the literature, one in which the adsorption of individual block copolymer molecules on the carbon nanotube occurs and the other involving the adsorption of multimolecular, spherical block copolymer micelles on the nanotubes. In both cases, the nature of stability imparted to the dispersion of carbon nanotubes in the aqueous medium is kinetic, controlled by the steric barrier imposed by the adsorbed individual block copolymer molecules or micelles. In this study we propose yet another mode of molecular interaction, wherein the block copolymer molecules self-assemble around the nanotube to generate a thermodynamically stable aqueous dispersion. Such a phenomenon of micellar solubilization of nanotubes is examined by constructing a phenomenological theory for the free energy change on solubilization. Illustrative calculations performed for symmetric PEO-PPO-PEO triblock copolymers show that block copolymer molecules are capable of solubilizing the carbon nanotubes in aqueous solutions. While the block copolymer molecules that spontaneously form cylindrical micelles are most likely to solubilize the nanotubes, other copolymers whose natural curvature is spherical or lamellar also are capable of forming cylindrical micelles around the nanotubes. Most interestingly, the solubilization is found to be size specific suggesting that this can be developed into a practical method to fractionate carbon nanotubes by size or chirality.
9:00 PM - K14.16
Carbon Nanotube Scaffolds via Self-assembled Aqueous Droplets.
Wonjun Lee 1 , Sun Hwa Lee 1 , Sang Ouk Kim 1
1 Materials Science and Engineering, KAIST, Daejeon Korea (the Republic of)
Show AbstractSelf-assembly is an effective strategy for the creation of novel structures at the nanoscale. Since self-assembly relies on the spontaneous and parallel organization of pre-existing building blocks, it is cost-effective as well as beneficial for large-scale organization processes. The organization of carbon nanotubes (CNTs) into films, fibers, gels or micropatterned materials may provide versatile opportunities for applications in nanoelectronics, energy storage devices, sensors, bioscaffolds, etc. because organized carbon nanotubes retain not only the intrinsic properties of individual nanotubes, such as high surface area, flexibility and electrical conductivity but also well defined architectures with various useful morphologies. Here we introduce a facile and versatile directed assembly method to produce cellular CNT scaffolds with tunable morphologies. Our approach uses the liquid-liquid interface between immiscible fluids, for example, on the surface of droplets, which has been shown to be ideal for the assembly of materials namely ‘breath figure’ method. The self-organization of aqueous droplets upon a volatile solution has been applied to an organic solution containing both polymer and CNTs as solutes and has yielded macroporous polymer/CNT nanocomposite films. After pyrolysis of the nanocomposites, highly stable CNT scaffolds retained the macroporous morphology. Owing to the simple process and morphological diversity, the CNT scaffolds are expected to be useful for various applications. In this work, their electrical conductivity and field-emission properties have been explored to elucidate potential applications for nanoelectronics and energy storage materials.
9:00 PM - K14.17
Carbon Nanotube/polymer Composites by Vacuum Plasma.
Sami Abou Rich 1 , Alexandre Felten 1 , Xavier Gillon 1 , Jean-Jacques Pireaux 1
1 , University of Namur FUNDP, Namur Belgium
Show AbstractThe non-reactive nature of the carbon nanotube (CNT) surface appears as a constraint in several technological applications such as formation of composites in which the CNT must be homogeneously dispersed in a matrix. To overcome this problem, modification of the CNT surface by changing its chemical composition has proved to be efficient. At variance with the methods generally used for surface modification (chemical, electrochemical, fluorination…), we have developed Inductively Coupled Plasma (ICP) at 13.56 MHz to polymerize a monomer (methyl methacrylate, allylamine, styrene …) onto a large quantity of CNTs (many grams), at once.The design and optimization of the plasma reactor will be described. Different (surface) characterization techniques have been used to ascertain the quality of the polymer deposits. FTIR allows to identify the chemical bonds in the plasma-polymerized polymers; XPS gives a global view of the overall elemental and chemical composition of the polymer-wrapped CNTs; SEM evidences the morphology of the deposit; Scanning Transmission X-ray Microscopy (STXM), with a spatial resolution better than 30 nm, allows to study the electronic, structural and chemical properties of pristine and plasma treated isolated nanotubes. Chemical mapping at the nanoscale is performed, highlighting polymer rich regions on individual nanotubes. This work is financially supported by the Nano2Hybrids project (EC-STREP-033311) and the Marshall – Nanocompo plan.
9:00 PM - K14.18
Ionic Doping Enhancement of Bulk Single Wall Carbon Nanotube Electrical Conductivity.
Christopher Schauerman 1 , Paul Jarosz 1 , Jack Alvarenga 1 , Brian Moses 1 , Thomas Mastrangelo 1 , Peggy Walsh 1 , Elizabeth Gorse 1 , Brian Landi 1 , Ryne Raffaelle 1
1 , RIT - NanoPower Research Labs, Rochester, New York, United States
Show AbstractSingle wall carbon nanotubes (SWCNTs) can be fabricated into many different form factors including papers, ribbons, yarns, ropes, and wires with unique physical, electrical and mechanical properties. These materials hold many benefits for a number of different applications including conductive wiring, structural reinforcement materials, and electrical storage media among others. Advancements are still needed, however, in purification, processing, doping and modification of SWCNT bulk materials to realize the measured properties from theory and at the individual nanotube level. Several strategies in the present work have been employed for enhancing the bulk properties of high purity SWCNT papers, ribbons, and wires; including the combined effects of mechanical densification, polymer additives, and chemical doping. As-produced SWCNT material was synthesized from pulsed laser vaporization of nickel and cobalt doped (3%/3% w/w) graphite targets. The as-produced material was purified by acid reflux and thermal oxidation in air and fabricated into free-standing SWCNT papers without the aid of polymer or binders. Baseline characterization of the free-standing SWCNTs papers is compared with post-modified materials. A number of different ionic salts with varying ionic radii and composition were incorporated into the bulk papers to dope the nanotube bundles and reduce the bulk contact resistance. The electrical conductivity of the ionic-doped SWCNT material increased more than an order of magnitude over the baseline material to 8x105 S/m with ionic doping. The effects of polymer additives and densification on the mechanical strength and electrical conductivity of SWCNT wires through the use of drawing dies has also been investigated. The maximum tensile strength (MPa) of the polymer-treated and densified material increased over 750% following treatement and densification. Further modification of SWCNT bulk materials could lead to even greater improvements, approaching the theoretical conductivity and tensile strength of an individual SWCNT. Lastly, the improved results for SWCNT bulk materials will be compared and discussed in the context of a sustainable replacement to conventional metal wiring like copper which is anticipated to become a future global concern over scarcity and environmental impact from refining.
9:00 PM - K14.19
Microscaled Carbon Nanotube-based Probes for Insect Neuronal Stimulation.
Wei-Mong Tsang 1 , S. Sinaei 1 , S. Murray 1 , A. Stone 2 , Z. Aldworth 3 , R. Levine 2 , J. Hildebrand 2 , T. Daniel 3 , A. Akinwande 1 , J. Voldman 1
1 Electrical Engineering and Computer Science, MIT, Cambridge, Massachusetts, United States, 2 Arizona Research Laboratories, Division of Neurobiology, University of Arizona, Tucson, Arizona, United States, 3 Department of Biology, University of Washington, Seattle, Washington, United States
Show AbstractInsects are promising candidate model organisms for aiding the development of neural prostheses and studying fundamental neuroscience as they have a relatively simple nervous system as compared to vertebrates. Moreover, functional interfacing of electrodes with insect nervous systems can result in novel applications such as insect-based Micro-Air-Vehicles. However, most existing neuroprosthetic probes are developed for mammals, which have significantly larger nervous systems than insects. Although microfabrication technology enables the creation of insect-sized neural probes, the resulting decrease in the surface area of the stimulation sites significantly reduces the charge transfer capability and increases the interface impedance between the probe and neural tissue. Carbon nanotubes (CNTs) present an attractive option as an electrode material as they have intrinsically large surface area and intriguing electrochemical properties, resulting in low impedance and high charge transfer characteristics. In this work, we developed a cyanide-free electroplating method to deposit CNT-Au nanocomposites onto flexible neuroprosthetic probes, which we then can use for insect flight control using multisite neural stimulation. The probe is made of two layers of polyimide with gold sandwiched in-between in a split-ring geometry. The CNT-Au nanocomposites are deposited from an aqueous solution of multi-wall CNTs and cyanide-free Au electrolyte with monophasic voltage pulse at 1 V for 1-10 minutes. Following CNT-Au nanocomposite deposition, we have observed a decrease in impedance at the biologically relevant stimulation frequency of 1 kHz of ~100× and ~10× increase in the charge transfer into saline media. The pupae of moths (Manduca sexta) implanted with CNT-Au nanocomposite-coated probes are able to emerge into adult moths, and in vivo characterization shows that the CNT-Au nanocomposite-coated probes are able to elicit multi-directional graded abdominal motions in both pupae and adult moths with a stimulation voltages as low as 2.0 V, as compared to 5.0 V for uncoated probes. In loosely tethered flight, we showed that the abdominal ruddering is able to cause the normally hovering moth to change its flight direction. These new CNT-Au nanocomposite-coated multisite probes represent a significant advance in microprobe technology for neural applications from invertebrates to mammals.
9:00 PM - K14.2
Synthesis and Characterization of Nanocomposites of Chitosan/SWNTs Used as Sensors for Trihalomethanes.
Julio Ximenes 1 , Rafael Salomao 2 , Antonio Souza Filho 3 , Mariselma Ferreira 1
1 Center for Natural Sciences and Humanities (CCNH), University Federal of ABC (UFABC), Santo Andre, Sao Paulo, Brazil, 2 Center for Engineering, Modeling and Applied Social Sciences (CECS), University Federal of ABC (UFABC), Santo Andre, Sao Paulo, Brazil, 3 Department of Physics, University Federal of Ceara (UFC), Fortaleza, Ceara, Brazil
Show AbstractChitosan is a heteropolysaccharide composed predominantly of residues by β-1,4-D-glucosamine. This biopolymer is one of the most promising polymers for using in nanocomposites because of an interesting combination of properties such as biocompatibility, biodegradability and abundance in nature. Simple structural changes in the polymer chain can lead a wide range of applications and the ability to generate biomaterials with different forms such as microspheres and membranes (1). Carbon nanotubes (CNTs) are formed by a simple tubular structure with sp2 hibridization. These single walled carbon nanotubes (SWNTs) exhibit physical and chemical properties with a great potential for applications in the fabrication of novel devices based on nanotechnology (2). The possibility of trihalomethanes (THMs) adsorption on carbon nanotubes bundles was recently pointed out in the literature (3). THMs like CHCl3, CHBrCl2, CHBr2Cl and CHBr3 are sub-products in water treatment processes and its managing is very important for environmental related applications. The aim of this work was to perform the characterization of a nanocomposites based in chitosan 2% (w/v) dissolved in acetic acid 1% (v/v) and SWNT (0.1 mg/mL) for the development of a material that can be a sensor for THMs. Firstly the sample of SWNTs was characterized by Raman spectroscopy to evaluate the adsorption of chloroform to the nanotubes. These analyses have shown the existence of non-covalent interaction between the SWNTs and chloroform. Subsequently, to investigate the process of nanotubes dispersion in the matrix of chitosan it was used photoluminescence and absorption UV-Vis, suggesting the ability of the SWNTs to be wrapped within the matrix of chitosan forming thin films with good dispersion and distribution. After the nanocomposites production, properties of the films were evaluated by stress-strain mechanical tests and it showed rupture values of 33 MPa for nanocomposites and 40 MPa for chitosan films. The infrared spectroscopy (FTIR) showed peaks in 3440cm-1 to axial deformation of OH (δOH), 2872 and 2910cm-1 ~ δCH, 1653cm-1 ~ δCO, 1417 and 1377cm-1 ~ δCN, while the peak at 1580cm-1 is due the angular deformation of NH. All these peaks are characteristic of the chitosan. Ongoing tests of thermogravimetric analysis (TG), dynamic scanning calorimetric (DSC), x-ray and scanning electron microscopy (SEM) are being made to evaluate the thermal properties and morphology of nanocomposites. In conclusion, the nanocomposites has good mechanical strength and chemical stability which indicate the possibility of using carbon nanotubes wrapped in polymeric matrix for various applications.Acknowledgments: CNPq and CAPES. 1)Gentili, 2006 Intern Biodet. Biodeg. 57 222–228. 2)Souza Filho, 2007 Quim. Nov. 30 1695-1703.3)Nowack, 2007 Envir. Pol. 150 5-22.
9:00 PM - K14.20
Molecular Dissolution of Carbon Nanotubes (CNTs) in Superacids.
Nicholas Parra-Vasquez 1 3 , Natnael Behabtu 1 3 , Micah Green 1 3 , Cary Pint 2 3 , Virginia Davis 5 , Judith Schmidt 4 , Ellina Kesselman 4 , Yachin Cohen 4 , Robert Hauge 2 3 , Yeshayahu Talmon 4 , Matteo Pasquali 1 2 3
1 Chemical Engineering, Rice University, Houston, Texas, United States, 3 Smalley Institute for nanoscale science and technology, Rice University, Houston, Texas, United States, 2 Chemistry, Rice University, Houston, Texas, United States, 5 Chemical Engineering, Auburn University, Auburn, Alabama, United States, 4 Chemical Engineering, Technion-Israel Institute of Technology, Haifa Israel
Show AbstractFluid phase processing is critical for the production of CNT based macroscopic articles such as films and fibers. However, their dissolution has been a major hurdle for researchers in the past decade. Here we characterize CNT/superacid phase behavior as a function of acid strength and CNT concentration. We draw particular attention to the ability of chlorosulfonic acid to dissolve CNTs in an isotropic phase at high concentrations. At still higher CNT concentrations, birefringent liquid crystalline phases form. Cryo-TEM imaging shows that in the isotropic phase, CNTs spontaneously dissolve in chlorosulfonic acid as individuals; this is true even for CNTs that are hundreds of microns long. The dissolution mechanism is sidewall protonation by the acid, which results in inter-CNT repulsion; this mechanism is effective for CNTs with low defect density. Finally, we show that the isotropic phase can be used to produce transparent and conducting films, while the liquid crystalline phase can be used for the production of neat CNT fibers.
9:00 PM - K14.21
Mesoscopically Ordered Self-assembled Arrays of Single Wall Carbon Nanotubes from Solution.
Mariela Bravo Sanchez 1 , Trevor Simmons 2 1 , Miguel Angel Vidal Borbolla 1 , Daniel Hashim 3 4
1 Materiales y Dispositivos Semiconductores, Instituto de Investigacion en Comunicacion Optica, San Luis Potosi, San Luis Potosi, Mexico, 2 Chemistry & Chemical Biology/Materials Science & Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States, 3 Mechanical Engineering & Material Science, Rice University, Houston, Texas, United States, 4 Material Science & Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States
Show AbstractIt has been shown in previous works that the surfactant sodium dodecyl benzene sulfonate (SDBS) and the water soluble polymer polyvinylpyrrolidone (PVP) can create aqueous solutions of single wall carbon nanotubes. The work presented will demonstrate that these solutions are stable over a period of at least eighteen months, and can be used to obtain large arrays of self-ordered single wall carbon nanotubes from horizontal drop drying. These arrays form on the surface of a droplet during drying, and appear to contract during the final stages of drying to leave a network of surface bound arrays. Extremely large bundles, which can measure upwards of 10 microns in width, are observed along with the appearance of unique rings and loops. Alignment of single wall carbon nanotubes in these extremely large bundles frequently occurs on the scale of hundreds of microns. Various deposition parameters were studied including temperature, substrate inclination, gas flow over the substrate, and varied concentrations of SDBS, PVP, and single wall carbon nanotubes. FE-SEM images were used to assess the level of order in the arrays, and numerous studies have been completed. From the empirical evidence obtained, theories to describe the mechanism for the formation of self-ordered arrays have been developed and will be presented.
9:00 PM - K14.23
Conjugated Surfactants for the Dispersion of Carbon Nanotubes in Non-polar Organic Solvents.
Yan Ji 1 , Yan Yan Huang 1 , Ali Tajbakhsh 1 , Eugene Terentjev 1
1 Physics, University of Cambridge, Cambridge United Kingdom
Show AbstractWe develop two new amphiphilic molecules that are shown to act as efficient surfactants for carbon nanotubes in organic solvents. The active groups, which are highly attracted to graphene nanotube surface, are based on pyrene and porphyrin. We show that relatively short (C18) carbon tails are insufficient to provide stabilization. As our ultimate aim is to disperse and stabilize nanotubes in siloxane matrix (polymer and crosslinked elastomer), both surfactant molecules are made with long siloxane tails to facilitate solubility and steric stabilization. We show that pyrene-siloxane surfactant is very effective in dispersing multi-wall nanotubes, while the porphyrin-siloxane is making single-wall nanotubes soluble, both in petroleum ether and in siloxane matrix.
9:00 PM - K14.24
Heat Treatment of Single-walled Carbon Nanotubes Structures.
Paul Hummel 1 , Tabbetha Dobbins 1 2
1 Institute for Micromanufacturing, Louisiana Tech University, Ruston, Louisiana, United States, 2 Dept. of Physics, Grambling State University, Grambling, Louisiana, United States
Show AbstractPrevious research was able to fabricate precise and controlled single-walled nanotubes (SWNT) structures using standard UV lithography. The structures were made from SWNT dispersions containing poly(sodium styrene sulfonate) (PSS). The electrical characteristics of the resulting structure were degraded significantly due to the PSS in the final structure. This work studies how a heat treatment on the fabricated SWNT structure can burn off the PSS and improve the electrical characteristics of the final device. The SWNT structures are heat treated up to 700° C in steps of 100°. After each step, the SWNT structure is characterized. The surface morphology of the SWNT structures is analyzed with SEM and EDS. A Keithley probe station is used to measure the electrical properties of the composite films formed in the trenches.
9:00 PM - K14.25
Non-invasive Fabrication of Functional Conjuaged Polymer/Carbon Nanotube Composites.
Lei Zhai 1
1 Nanoscience Technology Center and Chemistry Department, University of Central Florida, Orlando, Florida, United States
Show AbstractConjugated block copolymers have been used to disperse and functionalize pristine carbon nanotubes (CNTs). Upon a simple sonication, the conjugated polymer block such as polythiophenes can form strong π-π interactions with CNT walls, while the non-conjugated polymer block provides the de-bundled CNTs with a good solubility and stability in a wide range of organic solvents and host polymer matrices. Various block copolymers have been utilized to fabricate CNT nanocomposites with unique mechanical and electrical properties. The conductive block copolymers not only provide a universal system to disperse CNTs but also introduce other interesting properties into the system. Additionally, poly(3-hexylthiophene) supramolecular structures were fabricated on CNT surface. The conjugated polymer/carbon nanotube composite materials have great applications in energy storage and conversion devices.
9:00 PM - K14.26
Carbon Nanotube-Based Divided-Function Nanocomposites.
Vladimir Mordkovich 1 , Aida Karaeva 1 , Edward Mitberg 1
1 New chemical technologies and nanomaterials, Technological Institute for Superhard and Novel Carbon Materials, Troitsk, Moscow region Russian Federation
Show AbstractThe carbon nanotube (CNT) synthesis research has been mostly devoted to one of the three major challenges, i.e. (a) selective growth of certain fractions; (b) growth of longer CNT for technological fibers or (c) growth of short CNT with maximum yield. The latter task is most closely related to the emerging industry of multi-ton CNT production for polymer-CNT composites. Those composites with more or less homogeneous distribution of CNT in a matrix are usually referred to as improved polymers, i.e. are characterized by better mechanical or electrophysical properties.However, the unique CNT physical and chemical properties allow using in a more sophisticated kind of composites, i.e. divided-function composites. The divided-function composites possess properties, which are defined by separate functions performed by different components of the composites. For example, a composite sorbent, where matrix provides mechanical durability, while the first filler provides sorption capacity and the second filler provides selective mass transport to and fro the sorption centers. Divided function composite systems based on carbon structures with nanoclusters of transition metals (Ni, Co, Fe etc.) represent scientific and practical interest for such applications as chemical or petrochemical catalysis, selective sorption, etc. This work is devoted to the composites based on a mineral or carbon template, where the carbon nanostructures are grown on the template or deposited on it. Combination of nanostructure properties with the properties of the template affords ample opportunities for the development of novel technologies in catalysis and sorption such as active catalytic systems with enhanced heat conductivity and mechanical durability.A review and classification of the carbon nanostructure-containing composite materials and their possible applications in catalysis is given in this work along with experimental data on some systems under investigation. In particular, a divided-function composite catalyst for gas chemistry processes was prepared by three-step consecutive deposition of Co metal, then CNT and then Co metal again into a porous zeolite template. It is shown that the nanotubes grow along the transport pores of the zeolite template and serve as heat- and mass-transport arteries for the Co catalytically active centers. The tests of this catalyst in a Fischer-Tropsch process for synthetic fuel production showed almost two-fold increase in productivity in comparison with the conventional zeolite-based catalyst. The productivity increased from 150 to 320 kg/(m3×hr).
9:00 PM - K14.27
Effects of Carbon Ion on Glassy Carbon Electrode as Chemical Sensor.
Bopha Chhay 1 , Daryush Ila 1
1 , Alabama A&M University, Normal, Alabama, United States
Show AbstractGlassy carbon is a material commonly used for making electrodes for cyclic voltammetric (CV) and amperometric measurements. Previous work done at Alabama A&M University (AAMU) as shown that high energy ion beam can be used to activate carbons in the electrode. In this work, we fabricated a glassy carbon electrode and we used carbon ions to activate the electrode. Surface analyses including Raman spectroscopy, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) were performed to compare the changes in surface morphology and structure before and after ion bombardment.
9:00 PM - K14.28
Nanotube Crossbar Array via Microcontact Printing for Biomolecule Detection.
Shalini Prasad 1
1 EE, Arizona State University, Tempe, Arizona, United States
Show AbstractWe, present an approach to design, fabricate and develop a simple, low cost, and rapid prototyping crossbar junction comprising of amine functionalized c multi walled carbon nanotubes via flexible non-lithographic microcontact printing. This is achieved using poly-dimethylsiloxane (PDMS) molds. The parallel relief structure in order of a few micrometers is used to transfer continuous horizontal arrays of the MWCNTs in aqueous suspension. Using an alignment and the stamping process, PDMS molds is inked with the functionalized MWCNT suspensions and transferred in a grid-like manner onto the base micro-electrode platform. Parallel alignment of these MWCNTs is achieved due to the geometry of the mold relief structures. The hierarchical assembly resulted in the formation of the crossbar array structures. The functionality of this circuit as a sensor for detecting protein biomolecules was demonstrated through the current-voltage (I-V) characteristics. We have demonstrated detection of standard study proteins , Protein A and interleukin- 4 (IL-4) at picogram/ml sensitivity.The long term goal is to form the high density cross-array circuit pattern to develop an array of “devices” for multiplexed biomolecule detection.
9:00 PM - K14.29
Graphene Enhanced Self-healing Shape Memory Polymer Nanocomposition.
Xingcheng Xiao 1 , Tao Xie 1
1 , General Motors Research & Development Center, Warren, Michigan, United States
Show AbstractGraphene, a single planar layer of sp2-bonded carbon atoms, has attracted considerable attention owing to its extraordinary mechanical properties, high thermal and electronic conductivity. Particular efforts have been focused on harnessing the graphene properties in polymer nanocomposites, with the challenges lying in large scale fabrication of graphene and the process of dispersing it onto polymers. Significant progresses have been made, notably by dispersing graphene in its oxidized form and convert it back to the reduced form in the presence of a stabilizer such as a polymer. Here, we demonstrate a simple and scalable method to fabricate graphene polymer nanocomposites, without the need for filler chemical treatment. The graphene material used is nanolayered graphene (NLG) obtained by a scalable chemical vapor deposition (CVD) method. The NLG, in its pristine state, is dispersed directly into the precursor for an epoxy shape memory polymer (SMP). The shape memory properties of the cured epoxy polymer matrix impart a heat triggered non-autonomic self-healing property into the nanocomposites, which is significantly enhanced by the NLG fillers at ultralow contents (0.0026 vol% and 0.0124 vol.%, respectively).
9:00 PM - K14.3
Influence of Electron Density on the Separation Ability of Amine Functional Groups with Single Walled Carbon Nanotubes.
Justin Opatkiewicz 1 , Melburne LeMieux 1 , Mark Roberts 1 , Claire Anderson 1 , Zhenan Bao 1
1 Chemical Engineering, Stanford University, Stanford, California, United States
Show AbstractSingle walled carbon nanotubes (SWNTs) are synthesized in a mixture of semiconducting and metallic tubes. By exploiting noncovalent interactions with amines on surfaces, these nanotubes can be separated and purified semiconducting networks are obtained. Recent studies have shown that the electron pair on the nitrogen atom is primarily responsible for this selective binding with semiconducting nanotubes (SC-CNTs). In this study, we utilized amines with differing electronic structures to tune and optimize the SWNT chirality sorting. Cyanide groups served as electron-withdrawing groups whereas azide groups and methyl substitution promoted electron donation towards the terminal amine. Atomic Force Microscopy (AFM) was used to verify SWNT deposition and to analyze density and alignment. Micro-Raman spectroscopy and device testing were used to determine the efficiency of sorting on the different surfaces. Tuning the amine electron density can yield a better understanding of the origin behind the preferential interaction between amines and SC-CNTs. Using this information, the device properties of these semiconducting single walled nanotube networks (SWNTnts) can be finely tuned and yield higher quality thin film transistors (TFTs) and related devices.
9:00 PM - K14.30
Self-assembly of Fullerene (C60) into 0, 1, and 2D Structures via Drop-drying Process: The Critical Effect of Solvent Geometry.
Chibeom Park 1 , Hyun Jae Song 1 , Hee Cheul Choi 1
1 Department of Chemistry and Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), Pohang Korea (the Republic of)
Show AbstractThree types of geometrically defined C60 self-assembled crystals (disks, wires and dots) are systematically obtained via solution drop-drying method at room temperature. We have found that the final geometry of self-assembled C60 structure is critically affected by the geometry of solvents. When the C60 solution prepared using pseudo three dimensional (p3D) solvents, for example, CCl4 is drop-dried, p2D C60 hexagonal disk structures are formed. Similarly, the C60 solutions of p2D (m-xylene) and p1D (n-hexane) result in p1D and p0D self-assembled C60 wire and dot structures, respectively. Especially, we have found that C60 molecules are specifically guided to self-assemble into p1D structures as long as the benzene-series p2D solvents have functional groups at 120o apart, regardless of the polarity, type or number of the functional groups.
9:00 PM - K14.31
Counting Ions Through the Interior of Single Walled Carbon Nanotubes.
Chang Young Lee 1 , Jae-Hee Han 1 , Michael Strano 1
1 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractTheories predict that single walled carbon nanotube (SWNT) can be a fast molecular transporter due to its atomically smooth surface where molecular corrugation is minimized by high density of carbon atoms. Molecular dynamics simulation estimates the velocity of water and small molecules through the interior of carbon nanotubes to be several orders of magnitude higher than the value predicted by continuum hydrodynamics. Experimentally the velocity of water through the nanotubes was measured using 1) multi-walled carbon nanotubes where the pore size is significantly larger than the individual water molecules, or 2) thin membranes of double/single-walled carbon nanotubes from which only ensemble measurements can be made. However, none to date have studied how a single molecule is transported through individual single walled carbon nanotubes.In this work we demonstrate the first experimental evidence of single ion transport through the interior of individual single walled carbon nanotubes. Two reservoirs of ionic solutions are connected by an array of open-ended SWNT. Upon application of electrical field across the reservoirs, the trace of ion current through the nanotubes exhibits stochastic pore-blocking events with characteristic dwell time of individual ions. The transport of each ion is highly coordinated with the transport of the next ion resulting in an oscillation of the ion current. We have performed rigorous statistical analysis of the dwell time and the frequency of the pore-blocking events for various ions in order to understand the mechanism. Our results give direct answers to several critical questions that many researchers have speculated about for decades, and will be the basis of future application of carbon nanotubes as molecular conduits.
9:00 PM - K14.32
Polyoctenamer - Single Walled Carbon Nanotube Composites: Thermal Properties.
Rafael Villegas 2 , Alin Cristian Chipara 2 , Karen Lozano 2 , Mircea Chipara 1
2 Mechanical Engineering, The University of Texas Pan American, Edinburg, Texas, United States, 1 Physics and Geology, University of Texas Pan American, Edinburg, Texas, United States
Show AbstractPolymeric materials degrade under the effect of temperature. The destruction of the macromolecular chain is simpler if the degradation process occurs in inert atmosphere (such as nitrogen). The presence of oxygen results in additional oxidation processes that complicate the degradation pathway of polymers and nanocomposites.Recent studies indicated that the dispersion of nanometer-sized fillers such as carbon nanotubes and carbon nanofibers enhances the thermal and thermo-oxidative stability of polymeric matrices.A detailed investigation on the thermal and thermo-oxidative stability of nanocomposites obtained by dispersing single walled carbon nanotubes (SWNT) in polyoctenamer (Vestenamer; PO) is reported. Composites containing various amounts of SWNT have been obtained by extrusion; the concentration of SWNTs was ranging from 0 % wt. up to 15 % wt. Thermo gravimetric analysis (TGA) has been performed by using a TA instrument (TGA Q500) at various heating rates (5, 10, 20, 30, 40, and 50 oC/min) starting from 50 oC up to 700 oC. Measurements have been performed both in air (oxygen containing atmosphere) and in nitrogen (inert atmosphere). Approximately 10 mg samples were used in all experiments.The as obtained thermograms were analyzed in detail. The derivative of the mass evolution versus temperature was used to determine the temperature at which the mass loss is maxim (Tmax) and to estimate the mass loss speed. The amount of polymer lost at Tmax has been determined. The derivative of the mass evolution versus temperature has been fitted by an extended Lorentzian shape, and the width of this distribution has been measured. The fraction of polymer trapped within the polymer - SWNTs interphase was estimated; the thickness of the interface was approximately calculated within a simple approximation.The dependence of all these parameters on the concentration of SWNTs and on the heating rate was investigated in detail. The activation energy for the thermal degradation process has been determined, assuming an Arrhenius-like process. The effect of the filling with carbon nanotubes on the activation energy is discussed. The analysis has been extended to thermal degradation of these nanocomposites in air.The TGA data revealed an increase of the thermal stability of PO-SWNT composites by about 20 oC, confirming the formation of an interface between the polymeric matrix and the nanometer-sized fillers. Similar results were obtained in the case of the thermal degradation of PO-SWNT composites in air. Further experiments such as Differential Scanning Calorimetry (DSC) are scheduled in order to obtain a better picture of the modifications induced in PO by SWNTs.
9:00 PM - K14.33
Carbon Nanofibers for Reducing Immune Responses.
Young Wook Chun 1 , Thomas Webster 1
1 , Brown University, Providence, Rhode Island, United States
Show AbstractCarbon nanotubes and nanofibers are intrigued due to their promising applications in biomaterials. Although much effort has been focused on the utilization of those materials in tissue regeneration, immunological aspect is still unveiled and key issue. Since implanted biomaterials in human body are instantly interact with monocyte and lymphocyte cells in human body, cyto-toxicity and immune response will determine the following tissue formation and regeneration process. In this study, we investigated the macrophage response on altered surface energies of carbon nanofiber layers due to aromatic layers and results have shown strong dependence of cytokine release amounts from macrophages on different surface tensions of carbon nanofibers. In conclusion, surface treatment and purification process of nanofibers resulted in the change of hydrophobicity and it may reduce the pro-inflammatory responses of macrophages. Importantly, this finding can be utilized in developing enhanced drug delivery system and generating better soft/hard biomaterials with purified carbon nanotubes and nanofibers
9:00 PM - K14.34
Reduction-Controlled Viologen in Bisolvent as an Environmentally Stable n-Type Dopant for Carbon Nanotubes.
Soo Min Kim 1 , Jin Ho Jang 1 , Ki Kang Kim 1 , Jung Jun Bae 1 , Hyeon Ki Park 1 , Woo Jong Yu 1 , Il Ha Lee 1 , Gunn Kim 1 , Duong Dinh Loc 1 , Un Jeong Kim 2 , Eun-Hong Lee 2 , Hyeon-Jin Shin 2 , Jae-Young Choi 2 , Young Hee Lee 1
1 , Sungkyunkwan University, Suwon Korea (the Republic of), 2 , Samsung Advanced Institute of Technology, Suwon Korea (the Republic of)
Show AbstractVarious viologens have been used to control the doping of single-walled carbon nanotubes(SWCNTs) via direct redox reactions. A new method of extracting neutral viologen (V0) was introducedusing a biphase of toluene and viologen-dissolved water. A reductant of sodium borohydride transferredpositively charged viologen (V2+) into V0, where the reduced V0 was separated into toluene with highseparation yield. This separated V0 solution was dropped on carbon nanotube transistors to investigatethe doping effect of CNTs. With a viologen concentration of 3 mM, all the p-type CNT transistors wereconverted to n-type with improved on/off ratios. This was achieved by donating electrons spontaneously toCNTs from neutral V0, leaving energetically stable V2+ on the nanotube surface again. The doped CNTswere stable in water due to the presence of hydrophobic V0 at the outermost CNT transistors, which mayact as a protecting layer to prevent further oxidation from water.
9:00 PM - K14.35
First-principles Study of Graphene Nanoribbons as Nanoscale Molecular Sensors.
T. Urakawa 1 , K. Shintani 1
1 Department of Mechanical Engineering and Intelligent Systems, University of Electro-Communications, Chofu, Tokyo, Japan
Show AbstractGraphene has attracted much attention of researchers since its sinthesis by Novoselov et al. (Science, 2004). It is expected graphene will overcome the limitations of the conventional materials such as silicon, carbon nanotubes, etc. For example, it was shown experimentally that graphene can be excellent chemical sensors (Scedin et al., Nat. Mater., 2007). Graphene nanoribbons (GNRs) were also patterned via lithography (Berger et al., Science, 2006). GNRs are quasi-one-dimensional materials, and their long edges are so reactive that GNRs can easily be modified chemically. Accordingly, GNRs are more suited for sensing gas molecules than pristine graphene itself. Adsorption of gas molecules such as CO, NO, NO2, O2, N2, CO2, and NH3 on GNRs was investigated by Huang et al. (JPC, 2008). Using density functional theory (DFT) calculation, they showed the electronic and transport properties of GNRs with armchair edges are sensitive to the adsorption of NH3 molecules whereas the other gas molecules have negligible influences on their properties. Hence, it was suggested that NH3 molecules can be detected out of the other molecules via GNR-based sensors. Stimulated by the study of Huang et al., we in this paper investigate whether other gas molecules can be detected via GNRs with armchair edges or zigzag ones. Furthermore, the effects of Stone-Wales defects and strains on their performance as sensors of gas molecules are examined. DFT calculations using the PHASE code yield the optimized structures of GNRs before and after the adsorption of gas molecules on their edges, and the adsorption energies, charge transfer, and electronic band structures are calculated. Such calculations are tried for both graphene models with or without Stone-Wales defects and graphene models under strains or under no strains.
9:00 PM - K14.36
Stable Anchoring of Gold Nanoparticle onto Thiol-functionalized Multi-walled Carbon Nanotube and its Electrochemical Properties.
Hyun-Jung Choi 1 , In-Yup Jeon 1 , Jong-Beom Baek 1
1 , Ulsan National Institute of Science and Technology, Ulsan Metropolitan City Korea (the Republic of)
Show AbstractStable multi-walled carbon nanotube (MWNT)/gold nanoparticle (GNP) hybrid materials were prepared by three-step chemical route: (1) the functionalization of MWNT with 4-chlorobenzoic acid to afford 4-chlorobenzoyl-functionalized MWNT (CB-MWNT); (2) the grafting of CB-MWNT with thiol-terminated hyperbranched polyphenylene sulfide (HPPS) to yield thiol-functionalized MWNT (TF-MWNT); (3) the reduction of HAuCl4.3H2O by using sodium borohydride (NaBH4) in the presence of TF-MWNT dispersion. The bonding between surface thiol groups and GNPs was expected to offer a strong adhesion of GNPs onto the surface of TF-MWNT. Thus, we report the functionalization of MWNT to afford TF-MWNT and attachment of GNP to afford stable TF-MWNT/GNP composites, which could be simply prepared by adding TF-MWNT dispersed in gold colloid. GNPs were prepared by reduction of HAuCl4.3H2O in water with sodium borohydride as reducing agent and citric acid as capping agent. The formation of GNP was easily confirmed through change the color. Initially, HAuCl4.3H2O solution was yellow and the solution turned purple immediately after the addition of the sodium borohydride, indicating that gold nanoparticles were formed, which was mixed with TF-MWNT dispersed solution. As a result, GNPs were well bonded to TF-MWNT via strong S-Au bonds. The color of final solution became dark-black due to MWNT/GNP dispersion. The morphology of resultant composites was studied with scanning electron microscopy (SEM) and transmission electron microscope (TEM), showing that GNPs are uniformly distributed on the surface of TF-MWNT. On the basis of X-Ray diffraction (XRD) analysis, GNPs were strongly adhered onto the surface of TF-MWNT. To ensure the formation of composite, further characterization was conducted with Elemental analysis (EA), Fourier-transform Infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA) and ultraviolet-visible spectroscopy (UV-vis). The cyclic voltammetry (CV) of MWNT/GNP composite showed excellent electrocatalytic activity.
9:00 PM - K14.37
Supramolecular Recognition on Single-Walled Carbon Nanotubes Surface.
Ha-Jin Lee 1 , Bora Nam 1 , Jeong-Ok Lee 2 , Sang-Kyu Park 3
1 , Korea Basic Science Institute, Jeonju Korea (the Republic of), 2 , Center for University-Wide Research Facilities, Chonbuk National University, Jeonju Korea (the Republic of), 3 , Department of Chemistry, Chonbuk National University, Jeonju Korea (the Republic of)
Show AbstractIntense multidisciplinary study using singlewall carbon nanotubes (SWCNTs) has been focused due to their excellent electrical and mechanical properties. In spite of that, the advances of their technological applications including electronic devices and chemical/bio-sensors have been interrupted because of their low solubility in solvents. Chemical modification of SWCNTs and physical adsorption of organic molecules or polymers on SWCNT surfaces are useful strategies to improve the solubility of SWCNT in solvents. Herein we report the solubilization of SWCNTs in aqueous media based on the π-π interaction between pyrene moiety and SWCNTs and investigate macrocycle molecule, cucurbit[n]uril (CB[n], n = 6 and 7) recognition on SWCNT surface.CB[n] consists of n glycouril units linked by two methylene groups and has a rigid cavity capable of binding suitable-sized guest molecules. Therefore, the macrocycle molecule, CB[n] has been widely studied as a synthetic receptor and as a building block for supramolecular chemistry. CB[7] and CB[6] homologues have high affinity with viologen moiety and easily make their host-guest complexes. We designed and synthesized viologen derivative linked with pyrene moiety (py-vg) to investigate supramolecular interaction between CB[n] and viologen moiety on SWCNT surface. SWCNTs have been easily dispersed in aqueous solution of the py-vg via noncovalent π-π interaction between pyrene groups of py-vg and SWCNTs sidewall. The viologen moieties functionalized on SWCNT surface recognize CB[n] and form their complexes in aqueous media by supramolecular host-guest reaction. 1H-NMR results show the formation of the CB[n]…py-vg (n = 6 and 7) complexes on SWCNT surface (CB[n]…py-vg/SWCNT). Redox properties of viologen moieties before and after complexation with CB[n] were measured by using cyclic voltammetry. The π-π interaction between pyrene and SWCNTs was confirmed by fluorescence and UV-vis spectra. When excess CB[7] were added to CB[7]…py-vg/SWCNT solution, pyrene moieties were segregated from SWCNTs to form complexes with the excess CB[7] and the pure SWCNTs were isolated. On the contrary, excess CB[6] could not isolate the pure SWCNTs because the size of cavity was not wide enough to make its complex with pyrene moiety. We expect the supramolecular interaction on SWCNT surface via host-guest reaction is technologically critical to control the dispersion property of SWCNTs in aqueous systems.
9:00 PM - K14.38
High Rate Assembly and Transfer of Nanoelements.
Arun Kumar 1 2 , Chian Yilmaz 3 , Jia Shen 1 2 , Ming Wei 1 2 , Sivasubramanian Somu 3 , Ahmed Busnaina 3 , Carol Barry 1 2 , Joey Mead 1 2
1 Plastics Engineering, University of Massachusetts Lowell, Lowell, Massachusetts, United States, 2 Centre for High Rate Nanomanufacturing, University of Massachusetts Lowell, Lowell, Massachusetts, United States, 3 Centre for High Rate Nanomanufacturing, Northeastern University, Boston, Massachusetts, United States
Show AbstractCarbon nanotubes (CNT’s) are of interest because of their high thermal, mechanical, and electrical properties. They are often combined with polymers to enhance the properties; however, it would be useful for a number of applications to incorporate the CNT’s in a patterned structure. In this work we investigate approaches to pattern the carbon nanotubes and transfer this pattern to a polymer substrate using thermoforming, a commercially relevant process. We have used electrophoretic deposition of multi-wall carbon nanotubes (MWCNT), single wall carbon nanotubes (SWCNT) and conducting Polyaniline (PANI) onto the circuits followed by transfer to a polyurethane film by thermoforming. The electronic circuit had a gold (Au) wire with a width of 2 µm. Nanoelements were deposited onto the Au wires using the electrophoresis method with direct current (DC) voltage. A novel mold design for the thermoforming process was developed, which has a removable insert to keep the electrophoretically patterned circuit inside the mold. The thermoforming process parameters (temperature (heating time), forming time and vacuum) were optimized to obtain transfer of the patterned nanoelements to the polyurethane surface
9:00 PM - K14.39
Dielectric Polymer Nanocoating on Carbon Nanotube and its Application for Biosensing.
Huaizhou Zhao 1 , Lu Ren 2 3 , Yang Zheng 4 , Dong Cai 2 , Zhifeng Ren 1 , Thomas Chiles 2
1 Physics, Boston College, Boston, Massachusetts, United States, 2 Biology, Boston College, Boston, Massachusetts, United States, 3 , Central China Normal University, Wuhan China, 4 , Huazhong University of Science and Technology, Wuhan China
Show AbstractIn this work, we demonstrate a novel protein sensor by using electropolymerization method to establish a polyphenol(PPn) nanocoating on carbon nanotube (CNT) array. Polyphenol is a non-conductive polymer. Its electropolymerization on carbon nanotubes entitles a self-limiting process that can completely coat CNT at nanoscale (~15 nm) thickness. Unlike the conductive polymer film coatings, the significant impedance changes of the vertical CNT arrays with and without PPn coatings would allow the development of molecular imprints and protein detections using the electrochemical impedance spectroscopy (EIS) and other electrochemistry techniques. Ferritin is an iron storage protein especially in mammalian bloods. Its abnormal level, either high or low, will lead to hemochromatosis or amenia. The ferritin imprinted cavities can be developed after buffer rinsing of PPn film with ferritin entrapment. The imprints hold an intrinsic affinity to the template proteins that enables the specific bio-recognition.
9:00 PM - K14.4
Methanol Concentration Sensor Using Nafion/SWCNT Composite.
Kyongsoo Lee 1 , Byeong-Kwon Ju 1
1 , Korea University, Seoul Korea (the Republic of)
Show AbstractAn aqueous methanol sensor for direct methanol fuel cells (DMFCs) application is demonstrated. The methanol sensor is built using dispersed single-walled carbon nanotubes (SWCNTs) with Nafion117 solution to detect methanol concentration in water. This study is done for the potential use of the array as methanol sensor for direct methanol fuel cells (DMFCs). The concentration of methanol in the fuel circulation loop of a DMFC system is an important operating parameter, because it determines the electrical performance and efficiency of the system. The design is based on resistance output limited by permeation rates of water and methanol through a Nafion117 perfluorosulfonic acid membrane. Nafion117 is used not only for permeation membrane of methanol and water but also as the solution to achieve well-dispersed carbon nanotubes(CNTs). The sensor is also operative even at ambient temperature and responds quickly to concentration of methanol changes. Such a sensor can be easily incorporated into the methanol fuel solution flow loop in a DMFC system.
9:00 PM - K14.40
Purification of Carbon Nanotube Films Formed on SiC Substrates by Surface Decomposition.
Takahiro Maruyama 1 , Fumiya Nakahama 1 , Shigeya Naritsuka 1
1 Department of Materials Science and Engineering, Meijo University, Nagoya, Aichi, Japan
Show AbstractCarbon nanotube (CNT) growth by surface decomposition of SiC is a unique growth technique. By this method, high-density and well-aligned multi-walled CNTs (MWNTs) films can be formed on 6H-SiC(000-1) wafers, and the chilarity is restricted to a zigzag-type structure [1]. In addition, the grown CNTs are atomically connected to SiC crystals at the interface, which will be useful for fabricating CNT devices. Recently, we have also found that reduction of native oxides before the CNT growth improves the homogenity of CNT diameters [2]. In spite of these merits, D band intensity was comparable to the G band intensity in the Raman spectra and carbon-related impurites were observed among the CNTs in TEM observations, suggesting that the quality of CNT films is not sufficient for fabricating the devices. In this study, we attempted purfication of the CNT films grown by SiC surface decomposition. Our results showed heating in a H2O2 solution is most effective in improving the G/D ratio, which also reduced threshold voltage of field emission.MWNT films used for purification were synthesized by the SiC surface decomposition method. The thickness of MWNT films were 400 nm and 1 μm. The purification was carried out by oxidation with heating in a H2O2 solution or steam. We also heated the MWNT films in KOH solution. All purification treatments were carried out for “as-grown“ MWNTs, which were not separated from the SiC substrates. The samples after these purification treatments were characterized by SEM, Raman, FT-IR and TEM. After the MWNT films were heated in steam between 400 and 650°C for 4 h, Raman results showed that the G/D ratios were about 2, which were almost the same as that before the heating. Heating at 70°C in KOH solution did not show distinct effects on the Raman spectra of MWNT films either. In contrast, after heating in H2O2 solutions, the G/D ratio increased to about 3 and the FWHM of G band peak became narrow, accompanied with the appearance of a D' shoulder peak, which indicates improvement of the MWNT film quality. FT-IR measurements showed that the damage on MWNT films after the H2O2 treatment was negligible In addition, regarding the MWNTs with the H2O2 treatment, dispersion was attained in the DMF solutions, although they were bundled too firmly to disperse before the treatment. After the treatments, the threshold voltage for field emssion was improved from 9.0 to 7.4 V/μm. These results indicate that the H2O2 treatment is effective in reducing the impurites and improving the MWNT film quality.[1] M. Kusunoki et al. Appl. Phys. Lett. 77 (2000) 531.[2] T. Maruyama et al., J. Nanotechnol. Nanosci. to be published.
9:00 PM - K14.41
Enhancement of Single-walled Carbon Nanotube Dispersion by Debundling Using Supercritical Fluids.
Woo-Ram Jung 1 , Young-Soo Seo 1
1 nano science&department, sejong university, Seoul Korea (the Republic of)
Show AbstractSingle walled carbon nanotube (SWCNT) having excellent physical and chemical properties has wide-ranged applications including transparent conducting films. Dispersion of SWCNT, especially debundling, is crucial for fabricating commercial products which need to get better transparency by reducing a percolation threshold. In this study, we use supercritical fluids (SCFs) for enhancing debundling, where SCF is expected to attenuate van der Waals interaction between individual tubes. Additives such as organic solvents, water, and surfactants are also used for isolating tubes during SCF treatment. Consequently concentration of SWCNT in water solution turns out to become twice by SCF treatment after ultra-centrifugation in comparison to without SCF treatment case, confirmed by UV-vis spectroscopy. Near-IR and Raman spectra will be presented for proving debundling. Additionally it will be presented that impurities originated from residual catalysts SWCNT are partly removed during SCF treatment.
9:00 PM - K14.42
Vertically Aligned Multi-walled Carbon Nanotube Decorated Anodes for Microbial Fuel Cells.
Rebecca Schaller 1 , Yanzhen Fan 2 , Shoutao Xu 2 , Alan Fern 3 , Frank Chaplen 2 , Hong Liu 2 , Jun Jiao 1
1 Physics, Portland State University, Portland, Oregon, United States, 2 Biological and Ecological Engineering, Oregon State University, Corvallis, Oregon, United States, 3 Electrical Engineering and Computer Science, Oregon State Univarsity, Corvallis, Oregon, United States
Show AbstractMicrobial Fuel Cells (MFCs) are not readily available for commercial use due to their low power density output. Efficiently transporting electrons from the microbe to the anode interface is key to increasing this power output. Nanomodification of the anode could offer one possible solution to this problem by providing a suitable anode surface for microbes, which enhances the connection between the microbes and the anode surface, thus increasing the electron flow—and therefore current—through the entire fuel cell. In this study, vertically aligned multi-walled carbon nanotubes (MWCNTs) were synthesized using plasma-enhanced chemical vapor deposition on pressed graphite pillars (anodes). Various lengths and densities of MWCNTs were studied. Average current densities were compared for each type of electrode over a period of 125 hours. Overall, the current density of the anode decorated with the aligned MWCNTs increased roughly 208%, a significantly greater output than the simultaneously tested un-nanomodified control samples.
9:00 PM - K14.43
Suspended Single-Walled Carbon Nanotube Based pH Sensors on Flexible Parylene-C Substrate.
Chih-Feng Yang 1 , Niksa Valim 1 , Chia-Ling Chen 1 , Mehmet. R. Dokmeci 1
1 Electrical and Computer Engineering, Northeastern University, Boston, Massachusetts, United States
Show AbstractMiniature, low cost, highly efficient and fast response pH sensors are of particular interest in the field of medical diagnostics and implantable devices. Carbon Nanotubes (CNT) with their high aspect ratio, large surface area to volume ratios and exceptional mechanical stability are potential candidates for highly sensitive sensor applications. Previously reported CNT based pH sensors were attached to a substrate which severely limited their performance. By realizing suspended CNT sensors, one can not only reduce the influence of the substrate, but also can enhance the active surface area of the sensor both for functionalization and also for sensing. In this paper, we present our latest results on suspended CNT pH sensors on a flexible parylene-C substrate. To realize these sensors, first a thin layer of 10 µm thick parylene-C is deposited on a silicon substrate. Next, the assembly electrodes (Au, 1500Å) were deposited and patterned using a combination of sputtering, optical photolithography and lift off process. Dielectrophoretic assembly is utilized for the attachment of SWNTs on to these suspended microelectrodes which had a gap of 4 µm. The process technology is compatible with most microfabrication methods, and the approach several advantages including being light-weight, low-cost and flexible. The operation of the sensor relies on the fact that the Hydroxide (OH–) ions from the solution attach to the walls of the CNTs which change their conductance. The I-V measurements from the SWNT sensors showed that the resistance values of the SWNTs decreased as they were exposed to solutions with higher pH values. Measurements were conducted with pH values from 4 to 10 which were from commercial vendors (Fisher Scientific, HACH). The resistance values decreased from 100KΩ (pH =4) to 75KΩ (pH=10) and the measurements were reproducible. This versatile technique allows the realization of nanosensors on low cost disposable substrates with potential applications in medical diagnostics and implantable devices.
9:00 PM - K14.44
Specially-Designed Atmospheres for Sintering Carbon Nanotube-Reinforced Hydroxyapatite.
Ashley White 1 , Alan Windle 1 , Ian Kinloch 2 , Serena Best 1
1 Dept. Materials Science and Metallurgy, University of Cambridge, Cambridge United Kingdom, 2 School of Materials, University of Manchester, Manchester United Kingdom
Show AbstractWhile hydroxyapatite (HA) is known for its bioactive properties derived from its chemical similarity to the mineral component of bone, its poor tensile strength and fracture toughness have prevented its use in major load-bearing devices [1]. Carbon nanotubes (CNTs), as one of the strongest and stiffest materials available [2], have the potential to strengthen and toughen HA, thus expanding the range of clinical uses for the material. However, certain challenges arise in combining these materials to form a dense composite [3].The work presented will focus on one of those challenges – selecting an appropriate sintering atmosphere and profile that can accommodate the requirements of both the HA and CNTs. Studies have shown that the presence of water in the atmosphere is required to retain HA’s hydroxyl groups [4], which impact its bioactivity. However, water leads to the oxidation of CNTs at the high temperatures needed to obtain a dense ceramic, and thus the reinforcing phase is lost. Previous studies of these composites have used techniques such as hot isostatic pressing [5] or spark plasma sintering [6] to circumvent this problem and keep both phases intact. However, these routes are expensive and geometrically limited compared with ambient-pressure sintering. We have examined fourteen sintering atmospheres under ambient-pressure conditions, with special consideration towards the thermodynamics of each. Characterisation of the sintered composites included XRD to ensure phase purity of the HA, FTIR to examine hydroxylation, density measurements, measurement of CNT retention, and SEM and TEM to examine the microstructure and condition of the CNTs before and after sintering. Additionally, the sintering profile has been adjusted to optimally balance CNT retention and microstructural characteristics which impact mechanical properties, such as porosity and grain size. With our optimised sintering conditions, we have been able to retain both HA’s hydroxyl groups and the CNTs and have achieved a high density, thus offering a more commercially-viable route for producing these composites.1. J. Hench (1991) J Amer Ceram Soc 74:1487-510.2. M.F. Yu, O. Lourie, M.J. Dyer, et al. (2000) Science 287:637-40.3. A.A. White, I.A. Kinloch, S.M. Best (2007) Int J Appl Ceram Technol 4:1-13.4. P.E. Wang and T.K. Chaki (1993) J Mater Sci 4: 150-158.5. L. Zhao and L. Gao (2004) Carbon 42: 423-460.6. M. Omori, A. Okubo, M. Otsubo, et al. (2004) Key Eng. Mater 254-256: 395-398.
9:00 PM - K14.45
Carbon Nanotube Modified Superhydrophobic Steel Surfaces.
Sunny Sethi 1 , Ali Dhinojwala 1
1 Department of Polymer Science, The University of Akron, Akron, Ohio, United States
Show AbstractInterfacial and surface properties play an important role in designing many modern day engineering and biological applications. One such surface property of great interest is superhydrophobicity. Superhydrophobic surfaces may not only be used for self cleaning but also for applications like in microfluidics, filtration, naval applications and robotics. Many low energy organic substances like silicones and fluorinated polymers have been used to make surfaces hydrophobic. However being organic, these substances leave the surfaces electrically and thermally insulating. Here we report fabricating environmentally stable, thermally robust and conductive super hydrophobic coatings for stainless steel using carbon nanotube mesh structures. Stainless steel is an important material used in industrial and architectural applications, and carbon nanotube based superhydrophobic coatings on steel offer many unique advantages compared to organic coatings used currently. These coatings showed a water contact angle of greater than 155° and can withstand exposure to boiling water, high thermal shocks and extreme temperature conditions. These coatings can further be reinforced and functionalized using suitable polymeric material without compromising on superhydrophobicity and conductivity. The large surface area of the carbon nanotube mesh allows intimate polymer nanotube interaction. Thus these coatings can have both the toughness of plastics and the excellent conductivity and thermal properties of carbon nanotubes. We demonstrated that this process can be used to coat objects of various shapes and sizes and even on the inner surfaces of pipes. This material will form basis for many new and unique applications such as heat exchangers, electrodes for fuel cells, solar panels, fluid transport and non-fouling surfaces.
9:00 PM - K14.46
On Chip Chemical Reactivity of Graphene and Graphene Multilayers Towards Electron Transfer Chemistries.
Richa Sharma 1 , Michael Strano 1
1 Chemical Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractReactivity of graphene and various multilayers towards electron transfer chemistries is probed by Raman spectroscopy after reaction on-chip. Single sheets are found to be almost ten times more reactive than bi or multi layers of graphene according to relative disorder (D) peak increases after functionalization. We define a new spectroscopic test to examine relative reactivity of graphene edges versus the bulk. We show for the first time that reactivity is at least two times higher than reactivity of the bulk single graphene sheet, as supported by theory. These differences in rates may be important for selecting and manipulating graphitic materials on-chip.
9:00 PM - K14.47
Carbon Nanotube Membrane Filters for Oil-water Separation.
Cheesung Lee 1 , Seunghyun Baik 1 2 3
1 SAINT, Sungkyunkwan Univ, Suwon, Gyeonggi-do, Korea (the Republic of), 2 School of Mechanical Engineering , Sungkyunkwan Univ, Suwon, Gyeonggi-do, Korea (the Republic of), 3 Department of Energy Science, Sungkyunkwan Univ, Suwon, Gyeonggi-do, Korea (the Republic of)
Show AbstractThe oil-water separation technology has created a great deal of interests for over decades due to the potential application in waste water treatment, oil and water refining and oil spill cleanup processes. Traditional technologies such as API, hydrocyclones and plate separators exhibit insufficient separation efficiency, high energy consumption and large occupational space.Here we developed carbon nanotube membrane filters for the oil-water separation. Such a filter was achieved by synthesizing vertically-aligned multi-walled carbon nanotubes (VAMWNTs) on stainless steel meshes with different pore sizes. The VAMWNT filter shows excellent hydrophobic-oleophilic properties which were improved by the dual scale roughness; i.e., nano-scale needle-like tubes on the mesh with micro-scale pores. The nanotube filter successfully separated diesel and water layers with outstanding efficiency, and even surfactant-stabilized emulsions. The fundamental physics for the separation can be applied to a variety of different hydrophobic and oleophilic liquids.
9:00 PM - K14.48
Short and Long Term Stability of Flexible SWNT based Flexible Thin Film Transistors in Air and in Biological Mediums with Parylene-C Passivation.
Selvapraba Selvarasah 1 2 , Ahmed Busnaina 2 , Mehmet Dokmeci 1 2
1 Dept. of Electrical and Computer Engineering, Northeastern University, Boston, Massachusetts, United States, 2 NSF-NSEC for High-rate Nanomanufacturing, Northeastern University, Boston, Massachusetts, United States
Show AbstractCarbon nanotubes (CNTs) with their unique chemical, physical and mechanical properties are promising active materials for novel and high performance electronic devices. However, CNTs are extremely sensitive to the gases in the environments which demand a proper encapsulation technique to isolate them from the environmental conditions. In this paper, we present SWNTs based flexible TFTs, and encapsulate them with a thin layer of parylene-C passivation layer and then evaluate their stability in air and in biological mediums. In order to realize the bottom gated TFT, we first deposit and 10um thick parylene- C layer on an oxidized silicon substrate. Next, we pattern the bottom gate electrodes. After depositing a thin dielectric layer, we next pattern the source and drain electrodes using a combination of sputtering and optical lithography. Next, SWNTs are assembled in between the source and drain electrodes using DEP assembly. As assembled the SWNTs contain a mixture of metallic and semiconducting nanotubes. We then conduct electrical breakdown to reduce the amount of metallic nanotubes in the channel region of the TFT. These transistors exhibited p-type behavior with a mobility of around 55 cm2/Vs and a maximum ON/OFF ratio of 103. Finally, devices were encapsulated with a pin hole free and chemically inert thin parylene film which has a low permeability to moisture and gases. The experimental results showed that parylene-C encapsulation layer does not introduce degradation in the device performance of TFTs. The long term stability of these TFTs were investigated using different parylene-C thicknesses (eg. 1um, 3um, 5um and 10 um) both in air and in 7% saline medium. The electrical instability of these flexible CNTFETs will be discussed in the paper.
9:00 PM - K14.5
SWNT Gas Sensor Fabricated on a Parylene-C Substrate.
Chih Feng Yang 1 , Chia-Ling Chen 2 , Niksa Valim 3 , Chen-Fu Guo 4 , Ahmed A. Busnaina 5 , Mehmet R. Dokmeci 6
1 Electrical Engineering, Northeastern University, Boston, Massachusetts, United States, 2 Electrical Engineering, Northeastern University , Boston, Massachusetts, United States, 3 Electrical Engineering, Northeastern University , Boston, Massachusetts, United States, 4 Electrical Engineering, Northeastern University , Boston, Massachusetts, United States, 5 Mechanical and Industrial Engineering, Northeastern University , Boston, Massachusetts, United States, 6 Electrical Engineering, Northeastern University , Boston, Massachusetts, United States
Show AbstractIn this paper, we demonstrate a novel Single-walled carbon nanotube (SWNT) gas sensor on a flexible parylene-C substrate. Gas sensors are widely used in many applications including environmental safety, gas alarms and controlling manufacturing processes. Traditional gas sensors have limitations being large and bulky. SWNT have numerous advantages including miniature size, large surface area-to-volume ratio and fast response, and hence are very promising candidates as active materials for the next generation gas sensor applications. The electronic properties of SWNTs are strongly related to the atomic structure and mechanical deformations which make them useful when developing extremely small sensors that are sensitive to the environment. Parylene-C, a light weight, flexible and a biocompatible polymer, is compatible with many microfabrication processes. Another attractive feature of parylene-C is that it is not sensitive to moisture and also can be readily peeled off from carrier substrates upon completion of the fabrication process. The fabrication of the flexible SWNT gas sensor starts by depositing a 10µm thick layer parylene-C layer on a 3" silicon wafer. Then, optical photolithography followed by a lift-off process is utilized to pattern the Au electrodes on the parylene-C layer. Au metal electrodes serve as a 2D microplatform for the assembling nanotubes. Utilizing Dielectrophoresis (DEP) assembly process, we next assembled the SWNT bundles onto the microplatform as sensing devices. Peeling off the parylene-C substrate containing the SWNT sensors from the silicon substrate concluded the process. The gas sensing measurements indicate that when the SWNTs were exposed to methanol vapor, their resistance increased by about 12%. The same sensors, under exposure to isopropanol, had their resistance increase by 3%. This versatile technique allows the realization of low cost SWNT based gas sensors with potential applications in disposable, flexible devices for environmental monitoring.
9:00 PM - K14.50
Using in situ Protection for Oxidative Unzipping of Carbon Nanotubes and Oxidation of Other Graphitic Materials to Graphite Oxide.
Dmitry Kosynkin 1
1 , Rice University, Houston, Texas, United States
Show AbstractUse of simple and inexpensive additives capable of stabilizing vicinal diol intermediates formed during oxidation of graphitic materials to graphite oxide (GO) drastically reduces overoxidation accompanied by formation of perforations in the basal plane of the graphene sheets. The resulting GOs show markedly improved structural integrity and increased mechanical strength. Subsequent reduction of these novel forms of GO to chemically converted graphene (CCG) gives materials with conductivity comparable to that of micromechanically cleaved highly ordered pyrolytic graphite (HOPG).
9:00 PM - K14.6
Kinetic Modeling of Nanotube-Based Photoelectrochemical Complexes Capable of Reversible Self-Assembly.
Ardemis Boghossian 1 , Moon-Ho Ham 1 , Jong Hyun Choi 2 , Michael Strano 1
1 Chemical Engineering, MIT, Cambridge, Massachusetts, United States, 2 Mechanical Engineering, Purdue University, West Lafayette, Indiana, United States
Show AbstractUnlike the synthetic photoelectrochemical systems available today, plants are capable of a reversible self-repair process that limits the impact of photodamage and degradation. In our work, we have demonstrated the development of the first photoelectrochemical complex capable of mimicking the dynamic equilibrium that forms the basis of natural self-repair. To form this complex, a mixture of phospholipids, recombinant proteins, single-walled carbon nanotubes (SWNTs), photosynthetic reaction center (RCs), and sodium cholate surfactant is dialyzed to remove sodium cholate. Upon surfactant removal, the remaining components reversibly and spontaneously self-assemble into a reaction center-lipid bilayer nanodisc-nanotube (RC-ND-SWNT)complex capable of solar energy conversion when in the assembled state. A kinetic model of the formation of this complex reveals that the assembly can transition reversibly between free components and the assembled state only if the rate of surfactant removal exceeds a kinetic threshold. Below this threshold rate, the system irreversibly forms pure lipid, protein, and SWNT particulate phases. The magnitude of this limiting rate is fixed by the differences in kinetic timescales between the rapid ND-SWNT assembly process and the thermodynamically-favored, but kinetically slower, homogeneous phases. Kinetic rate parameters for ND and ND-SWNT formation were determined by fitting this model to experimental data, which confirm that the system can continuously cycle between the assembled and disassembled state to create photoelectrochemical complexes capable of indefinite lifetimes.
9:00 PM - K14.7
CNT-DNA Topological Study According to Kind of Salts.
Chang Kee Lee 1 , Jin Kie Shim 1 , Kyemin Cho 1 , Sang Bong Lee 1
1 Korea Packaging Center, Korea Institute of Industrial Technology, Cheonan Korea (the Republic of)
Show AbstractIt is important the homogeneous integration of CNTs into a polymer matrix without destroying CNT integrity (i.e. chemical functionalization for hydrophilic property) and reducing CNT aspect ratio (i.e. cutting process to short) because applications of CNT composite depend on ability in dispersion of the CNTs. In the aqueous single walled carbon nanotubes (CNTs) solutions, it is known that CNT is a free suspension where it usually exists as CNT bundles which are consisted of tens of CNTs as the CNT “rope” due to its hydrophobic nature and small lateral dimensions. This behavior of CNTs has been considered by concentration ratio of either CNT or polymer in the solution. However there is a possibility of control of solution phase assembly of CNTs by a external ionic force. Flory predicted that biphasic dispersions of rods could be separated into isotropic and ordered phases by the application of an external force, such as ionic or centrifugal forces. Previously it was confirmed the DNA condenses when it is exposed to cationic salts. The packing state of DNA is more compact but the conformational structure is different due to the sensitivity of DNA for cationic salts. We can predict that the shape of DNA-coated CNTs ropes would be quite sensitive to ionic salts because the packing state and conformational structure of DNA can be affected sensitively by cations, and the DNA would also allow water and other small molecules to associate on the surface of DNA-coated CNTs. In this work, we selected a Ca2+ ion for the controlling external ionic force of the CNT-DNA solution to achieve a DNA interfacial coated CNT bundles (i.e. the nanofiber) and characterized a shape of CNT-DNA assembly in the solution. As a result, figure 1 show the TEM image for the CNT-DNA solution with 1-ethyl-3-methyl imidazolium bromide ([emim]Br) where specific weight ratio of CNT is 60% versus weight ratio of DNA (40%). A clear circular shape was found however, a square shape was occurred when Ca2+ was added to CNT-DNA solution that doesn't have [emim]Br. This phenomenon was exhibited by analysis of DNA helicity using circular dichroism (CD) spectroscopy. The difference of solution phase assembly between in RTIL and in Ca2+ was clarified.
9:00 PM - K14.8
Characterization of Exfoliated and Functionalized Graphene with Inverse Gas Chromatography.
Michael Papantonakis 1 , Bernadette Higgins 1 , Duane Simonson 1 , R. Andrew McGill 1
1 , US Naval Research Laboratory, Washington, District of Columbia, United States
Show AbstractGraphene sheets have been targeted as a new material for electronic devices, composite materials, and sensors due to their purity, mechanical strength, and high surface area. Many strategies have emerged for producing bulk quantities of single- or few-layered graphene flakes, ranging from chemical or thermal treatment of graphite to CVD growth of large sheets. These processes often introduce defects or functional groups to the graphene surface which can be difficult to detect using conventional analytical techniques. This especially important when incorporating graphene into polymeric composites, where improvement in the composite often depends critically on the homogeneous dispersion - and thus chemical compatibility with and binding to - the polymeric host. Inverse gas chromatography (IGC) is a sensitive technique for studying the surface properties of materials such as surface energies, adsorption capacities, adsorption enthalpies, and KA and KD numbers (ability of the adsorbent to accept or donate electrons).We evaluated several prevailing thermal and chemical techniques for exfoliating graphite into single- or few-layered graphene sheets and analyzed the products with IGC, as well as Raman spectroscopy, FTIR, and various microscopies. We found that the KA and KD numbers as determined by IGC serve as good predictors of the compatibility of graphitic materials with the desired polymeric matrix.
9:00 PM - K14.9
Simple and High-throughput Colloidal Dispersion of Carbon Nanotubes Using Electrostatically Tethered Nanoplatelets.
Dazhi (Peter) Sun 2 1 , W. Neil Everett 2 , Chien-Chia Chu 2 , Hung-Jue Sue 2
2 Mechnanical Engineering, Texas A&M University, College Station, Texas, United States, 1 , Brookhaven national lab, Upton, New York, United States
Show AbstractWe report a simple colloidal approach to fully disperse carbon nanotubes (CNTs) into individual tubes with preserved physical properties in water and polymers using electrostatically tethered inorganic nanoplatelets. Following dispersion in water, the dispersant, inorganic nanoplatelets, can be removed through electrostatic screening by tuning the ionic strength of the solution. The purified CNTs are subsequently redispersed through conventional surfactants and polymers. Various characterization techniques such as high-resolution transmission electron microscopy, UV-vis-NIR, and Raman are utilized to confirm the dispersion. Such high-quality individually dispersed CNTs can be well aligned in microfluidic channels for various applications that require high conductivity and high current density on a surface. Moreover, polymer nanocomposites containing well dispersed CNTs show exceptional mechanical properties: significant improvements in both modulus and strength without reduction in ductility. The dispersion mechanisms and implications of this approach on CNT-based polymer nanocomposites are also discussed.
Symposium Organizers
Kenji Hata Advanced Industrial Science and Technology (AIST)
Annick Loiseau Laboratoire d'Etude des Microstructures
Yoke Khin Yap Michigan Technological University
Ming Zheng National Institute of Standards and Technology
K15: NEMS: Properties and Application
Session Chairs
Kinji Asaka
Craig Friedrich
Kenji Hata
Thursday AM, December 03, 2009
Room 302 (Hynes)
9:30 AM - **K15.1
Three Dimensional Microstructures from CNT Forests by Nano Infiltration Fabrication (NIF).
Robert Davis 1
1 Physics and Astronomy, Brigham Young University, Provo, Utah, United States
Show AbstractA class of carbon nanotube composite structures have been developed to take advantage of the precise high aspect ratio shape of patterned, vertically-grown nanotube forests. These patterned forests were rendered mechanically robust by chemical vapor infiltration and were used to fabricate a diverse variety of functional MEMS devices, including comb drives, cantilevers, bistable mechanisms, and thermomechanical actuators. A wide range of chemical vapor depositable materials can be used for the infiltration including materials that have previously been difficult to pattern in 3-D including oxides, nitrides and carbides. Porous 3-D microstructures were also fabricated by this technique for applications where high surface area is desirable.
10:00 AM - **K15.2
Carbon-nanotube-based Elastic Conductors for Stretchable Electronics and Displays.
Takao Someya 1 2 , Tsuyoshi Sekitani 1 , Hiroyoshi Nakajima 3 , Hiroki Maeda 3 , Kenji Hata 4 , Takanori Fukushima 5 , Takuzo Aida 6 7
1 Department of Electric and Electronic Engineering, The University of Tokyo, Tokyo Japan, 2 Collaborative Institute for Nano Quantum Information Electronics (INQIE), The University of Tokyo, Tokyo Japan, 3 R&D Center, Dai Nippon Printing Co., Ltd., Chiba Japan, 4 Research Center for Advanced Carbon Materials, National Institute of Advanced Industrial Science and Technology, Tsukuba Japan, 5 Functional Soft Matter Engineering Laboratory, Advanced Science Institute, RIKEN, Wako Japan, 6 Department of Chemistry and Biotechnology, The University of Tokyo, Tokyo Japan, 7 Nanospace Project, Exploratory Research for Advanced Technology–Solution Oriented Research for Science and Technology, Japan Science and Technology Agency, Tokyo Japan
Show AbstractWe report recent progress and future prospects of elastic conductors using mm-long single-walled carbon nanotubes (SWNTs) [1] as a conducting dopant. SWNTs were uniformly dispersed as chemically stable dopants in a fluorinated rubber matrix by using an ionic liquid, and manufactured SWNT composite films [2,3]. Conductivity of more than 100 S/cm and stretchability of more than 100% are obtained. We have also successfully fabricated rubber-like stretchable integrated circuits (ICs). The abovementioned elastic conductors are integrated with organic transistors, which are fabricated by state-of-the-art printing processes, and are then used as wirings in large-area stretchable ICs. These ICs, which have a high electronic performance, can be stretched by up to 70% without any degradation in their mechanical or electronic properties. This is an important step in the development of ICs that can be used on freely curved surfaces and in smart surfaces [4,5]. Subsequently, it will be possible to develop an intelligent surface that will be able to interact with people, objects, and the environment in new ways.Furthermore, making full use of this extraordinary conductivity, we constructed a rubber-like stretchable active matrix display comprising integrated printed elastic conductors, organic transistors, and organic light-emitting diodes. The display could be stretched by 30–50% and spread over a hemisphere without any mechanical or electrical damage [6].Acknowledgment: This study was partially supported by the Grant-in-Aid for Scientific Research (KAKENHI; WAKATE S), the Special Coordination Funds for Promoting and Technology.References 1. K. Hata et al., Science 306, 1362 (2004); 2. T. Fukushima, et al., Science 300, 2072 (2003); 3. T. Sekitani, Y. Noguchi, K. Hata, T. Fukushima, T. Aida, and T. Someya, Science, 321, 1468 (2008); 4. T. Someya et al., Proc. Natl. Acad. Sci. U.S.A. 101, 9966 (2004); 5. T. Someya, et al., Proc. Natl. Acad. Sci. U.S.A. 102, 12321 (2005); 6. T. Sekitani, H. Nakajima, H. Maeda, T. Fukushima, T. Aida, K. Hata, T. Someya, Nature Materials 8, 494 (2009).
10:30 AM - **K15.3
Aligned Carbon Nanotube Wafer-based Device Applications.
Takeo Yamada 1
1 Nanotube Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan
Show AbstractWith the motivation to realize reproducible, uniform, and reliable carbon nanotube (CNT) based devices, we developed an approach centered on the use of aligned and closely-packed CNT films that we denote as “CNT wafers” [1]. Through this approach an assembly of a predetermined massive quantity of aligned CNTs, grown by the super-grown method [2], could be placed at prescribed locations, orientations, which then could be shaped into well-defined and controlled configurations. Together with the ability of the CNT wafer to exist as a single cohesive units with useful mechanical and electrical properties, individual CNT components with higher-level structural diversity and complexity, which serve as building blocks for device systems, could be fabricated.In this presentation, I will provide an overview of our recent progress on the development of carbon nanotube wafer-based applications. After providing an introduction to the CNT wafer concept and our motivations, I will present the fundamental obstacles we face. Then, I will present examples of applications on both the small and large length scales which highlight the unique properties of the CNT wafer. Finally, I will discuss our future outlook. [1] Y. Hayamizu, T. Yamada, K. Mizuno, R.B. Davis, D.N. Futaba, M. Yumura, and K. Hata, Nature Nanotech. 3, 289 (2008).[2] K. Hata, D.N. Futaba, K. Mizuno, T. Namai, M. Yumura, and S. Iijima, Science 306, 1362 (2004).
11:00 AM - K15: NEMS1
BREAK
11:30 AM - **K15.4
Fast Fully Plastic Actuator Based on Ionic-liquid-based Bucky Gel.
Kinji Asaka 1 , Ken Mukai 1 , Takushi Sugino 1 , Kenji Kiyohara 1 , Ichiroh Takeuchi 1 , Don Futaba 4 , Kenji Hata 4 , Takanori Fukushima 2 3 , Takuzo Aida 3 2
1 Reseach Institute for Cell Engineering, AIST, Ikeda Japan, 4 Nanotube Research Center, AIST, Tsukuba Japan, 2 , RIKEN, WAKO Japan, 3 , ERATO-SORST Nanospace Project, Tokyo Japan
Show AbstractRecently, much attention has been focused on soft materials that can directly transform electrical energy into mechanical work, because they allow a wide range of applications including robotics, tactile and optical display, prosthetic devices, medical devices, micro-electromechanical systems and so forth. Especially, electromechanical polymer actuators, which can work quickly and softly driven by low voltage are very useful, since they can be used as artificial muscle-like actuators for various bio-medical and human affinity applications. In previous papers, we reported the first dry actuator that can be fabricated simply by layer-by-layer casting, using 'bucky gel', a gelatinous room-temperature ionic liquid containing single-walled carbon nanotubes (SWNTs). The actuator has a bimorph configuration with a polymer-supported internal ionic liquid electrolyte layer sandwiched by polymer-supported bucky-gel electrode layers, which allow quick and long-lived operation in air at low applied voltages. Recently, using millimeter-long 'super-growth' carbon nanotubes (SG-SWNTs), produced by a water-assisted modified CVD method that was developed by Hata et al., we developed a high-performance 'dry' actuator, which shows in air a very large bending motion in quick response to an applied alternating square-wave voltage of only 5 Vp.-p.. This achievement was made by our interesting finding that SG-SWNTs associate together tightly with ionic liquids, affording a free-standing sheet with a superb conductivity. In this paper, some of the recent developments of the actuator performance are reported.
12:00 PM - K15.5
Aligned Carbon Nanotube/Ionomer Composite Electrodes in Ionic Polymer Actuators with Large and Fast Strain Response.
Sheng Liu 1 , Yang Liu 1 , Hulya Cebeci 3 4 , Roberto de Villoria 3 4 , Jun-Hong Lin 2 , Brian Wardle 3 4 , Qiming Zhang 1 2
1 Electrical Engineering, Penn State University, University Park, Pennsylvania, United States, 3 Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 4 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania, United States
Show AbstractIon/electron conductor composite electrodes made of high-volume-fraction vertically aligned carbon nanotube (CNT) and ionomers show great improvement in ionic conduction which is highly desirable in many ionic transducers (actuators and sensors) and electrical energy storage systems (Li-ion batteries and ultracapacitors). With unique morphology, this new kind electrodes provide aligned paths for ions and continuous connection for electrons, which also increase the electrical efficiency. The ionic and electronic conductivity are in the order 0.1 mS/cm and 1000 mS/cm, respectively. High strain (>10%) is also observed due to good electromechanical coupling in aligned CNT with volume fraction up to 22% and 15-20 nm spacing between the nanotubes of 8-10 nm diameters[1]. Even with thick electrodes (>20µm) the actuators could have fast actuation response because of high speed ion transport, resulting in high power/energy output. Anisotropic mechanical property of these composite electrodes increases mechanical efficiency by clamping strain in the nanotube growth direction (thickness direction) and enhance strain in lateral direction, from which the total efficiency could be increased 33%. [1] Wardle BL, Saito DS, Garcia EJ, Hart JA, de Villoria RG and Verploegen EA, Adv. Mater. 20, 2707-2714 (2008).
12:15 PM - K15.6
Thermoplastic Polyurethane Nanocomposites Produced with Long Carbon Nanotubes: Orientation Effect on Electrical Conductivity.
Glaura Silva 1 , Marco-Tulio Rodrigues 1 , Cristiano Fantini 2 , Raquel Borges 1 , Brent Carey 3 , Li-Jie Ci 3 , Marcos Pimenta 2 , Pulickel Ajayan 3
1 Departamento de Química, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil, 2 Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil, 3 Department of Mechanical Engineering and Materials Science, Rice University, Houston, Texas, United States
Show AbstractThermoplastic elastomeric polyurethanes (TPUs) show hard and soft domains segregation exhibiting very interesting thermal and mechanical properties associated with special morphological arrangements. Apparent inconsistencies in polymer/carbon nanotube properties reported in the literature can be due to several factors such as: nanotube synthetic process, purification (if any) and aspect ratio; characteristics of the polymer matrix and nanocomposite fabrication procedure – solution blending, melting blending or in situ polymerization. Long array of carbon nanotubes (~3 mm) are not easily dispersed in polymers to produce anisotropic composites without significant cutting of the tubes. Otherwise, to take advantage of the length is possible to impregnate the carpet of carbon nanotube with the polymer. This strategy was applied to produce oriented polyurethane/carbon nanotube composites. Moreover, a random nanocomposite was prepared with the same carbon nanotubes by using a coagulation method. An increase of 10oC on glass transition was observed with the addition of 6 mass% of nanotubes. SEM images indicated that the coagulation method lead a better coverage of the nanotubes by the polymer. Raman spectroscopy showed important differences in the nanocomposite spectra for the oriented and random material. Furthermore, the oriented nanocomposite presented conductivities 100 times higher (~1 S/cm) than the random material (~0.01 S/cm) for the same content (6 mass%) of nanotube. This is an interesting result regarding the effect of the polymer layer separating the nanotubes on the conductivity levels.
12:30 PM - K15.7
Thermoelectric Applications of Carbon Nanotube Sheets.
David Lashmore 1 , Jennifer Mann 1 , Thomas VanVechten 1 , David Deresh 1 , Diana Lewis 1 , Ian Wilson 1
1 R&D, Nanocomp, Concord, New Hampshire, United States
Show AbstractThis paper summarizes Nanocomp’s progress towards the fabrication of p-type and n-type semiconducting regions on large carbon nanotube sheets suggesting a potential for large-scale thermoelectric device applications. High electrical conductivity and independently controlled thermal conductivity potentially enables high figure of merit (ZT) values. The use of single-wall or multi-wall carbon nanotube (SWCNT or MWCNT) sheets is investigated through identification and improvement of the Seebeck coefficient, thermal conductivity, and electrical resistivity. We show that coating with specific chemicals in post-processing tunes the Seebeck coefficient from -50 to +75 micro volt per deg Kelvin. Both extremes have been achieved on the same sheet. In-situ doping and post processing can change the thermal conductivity without affecting electrical resistivity or Seebeck coefficient. Advantages over bismuth telluride (a common thermoelectric material) include low density, low cost, high-temp stability, and an abundant precursor material. Applications of thin film CNT thermoelectric devices for direct solar conversion are described.
12:45 PM - K15.8
Thermal Conductivity of Graphene: A First-principles Study.
Nicola Bonini 1 , Jivtesh Garg 1 , Nicola Marzari 1
1 DMSE, MIT, Cambridge, Massachusetts, United States
Show AbstractCarbon nanostructures, such as graphene and carbon nanotubes, are particularly promising materials for thermal management applications because of their very high thermal conductivity.A clear understanding of the transport properties of thesematerials is a key step in view of their possible integration into future devices.Here, we present our first-principles results for the thermal conductivity of graphene.The vibrational properties and the cubic anharmonic termsare calculated using density-functional theory and density-functional perturbation theory.The thermal conductivity is determined by directly solving the linearized Boltzmann transport equation using an iterative procedure.This method doesn't rely on any a priori assumptions on the role of the different phonon modes and on the nature of the phonon-phonon (normal or umklapp) scattering processes. This is an important step to accurately estimate the thermal conductivity of graphene and to assess the main mechanisms for energy relaxation in this system.
K16: Chemical and Biological Applications III
Session Chairs
Thursday PM, December 03, 2009
Room 302 (Hynes)
2:30 PM - **K16.1
Biomedical Application of Carbon Nanotubes for Cancer Molecular Imaging and Therapy.
Zhuang Liu 1 2 , Hongjie Dai 2 , Xiaoyuan Chen 3
1 Functional Nano & Soft Material Laboratory, Soochow University, Suzhou, Jiangsu, China, 2 Chemistry, Stanford University, Stanford, California, United States, 3 Radiology, Stanford University, Stanford, California, United States
Show AbstractBiological applications of carbon nanotubes have been attracting tremendous attentions recently [1]. In the past few years, we have studied the in vivo biodistribution, tumor targeting, long term fate and toxicity of functionalized single walled carbon nanotubes (SWNTs) in animals [2,3]. We have uncovered that SWNTs with proper surface chemistry are biocompatible and non-toxic in vitro to cells. After being intravenously administrated into mice, SWNTs are accumulated in reticuloendothelial systems (RES) including liver and spleen, and slowly excreted via biliary pathway in feces without exhibiting obvious side effect [3]. After those fundamental studies, for the first time we have shown that carbon nanotubes can be used as drug delivery vehicles for in vivo cancer treatment in mouse xenograft tumor models to enhance treatment efficacy and / or reduce side effects of chemotherapy drugs [4]. Two commonly used anti-cancer drugs, paclitaxel and doxorubicin have been involved in our studies. On the other hand, the intrinsic optical properties such as resonance Raman scattering and near-infrared (NIR) photoluminance of SWNTs allow us to track and image nanotubes in vitro and in vivo. Multiplexed multi-color NIR Raman imaging can be realized by using isotopically modified SWNTs [5]. As many as five different SWNT Raman ‘colors’ have been produced and used to label and image cancer cells in vitro and tumor slices ex vivo, revealing both geometrical and molecular information of biological samples. Taken together, carbon nanotubes are promising nanomaterials for future multimodality cancer therapy and imaging.[1] Liu, Z., Tabakman, S., Welsher, K., and Dai, H. Nano Res. 2, 85-175 (2009)[2] Liu, Z. et al. Nat. Nanotechnol. 2, 47-52 (2007)[3] Liu, Z. et al. Proc. Natl. Acad. Sci. USA 105, 1410-1415 (2008)[4] Liu, Z. et al. Cancer Res. 68, 6652-6660 (2008)[5] Liu, Z. et al. J. Am. Chem. Soc. 130, 13540–13541 (2008)
3:00 PM - K16.2
Diagnosing Lung Cancer by Random Network of Single-Walled Carbon Nanotubes Coated with Non-Polymeric Organic Materials.
Hossam Haick 1
1 Dept. Chemical Engineering, Technion - Israel Institute of Technology, Haifa Israel
Show AbstractRecent statistics have estimated that there were nearly 2.9 million new cases diagnosed in 2004 and over 1.7 million deaths from cancer in US, with lung cancer as the commonest form of cancer diagnosed and of cancer death. In this study, we have developed an array of sensors to detect lung cancer and to differentiate between the Volatile Organic Compounds (VOCs) found in the breath of patients with lung cancer, relative to healthy controls. A technology, in which a (semi-) conductive random network of single-walled carbon nanotubes (SWCNTs) and insulating non-polymeric organic materials provide arrays of vapor detectors form the basis for our approach. The study was designed in two main phases. In the first phase, alveolar breath was collected from individuals with lung cancer and from healthy subjects and analyzed with GC-MS, to reveal the characteristics of VOCs in the collected breath samples. In the second phase, the major VOCs found in the healthy and diseased states were simulated and exposed to the developed array of sensors that were conjugated with machine learning algorithms. Our results indicate that the array of the developed sensors has a high potential for diagnosis of lung cancer via breath samples. The sensors array showed excellent discrimination between the VOCs found in the breath of patients with lung cancer, relative to healthy controls, especially if the sensors array is preceded with either water extractor and/or pre-concentrator of VOCs. The obtained results with simulated biomarkers were compared with responses from the same array of sensors that were exposed to real alveolar breath. A reliable correlation was found between the two classes of responses. The developed devices are expected to be relatively inexpensive, portable, and amenable to widespread screening. Given the impact of rising incidence of cancer on health budgets worldwide, the proposed technology will be a significant saving for both private and public health expenditures. The potential for using the proposed technology towards other diseases and conditions make it of further great interest.
3:15 PM - K16.3
Potential Transport, Transformation, and Impact of Carbon Nanotubes in Natural Aqueous Ecosystem.
Shirley Tang 1
1 chemistry, university of waterloo, Waterloo, Ontario, Canada
Show AbstractNoval nanomaterials, such as carbon nanotubes (CNTs), have sparked tremendous interest in a wide range of industrial applications. At the same time, nanomaterials posed new challenges in environmental monitoring and risk assessment. Many questions await answers. What are the routes of transportation and transformation of emerging nanomaterials? What are their distribution in various environmental compartments and how to detect? What are their ecotoxicity and the risk to public health? Here, we report our study which revealed 1) potential transport and transformation of CNTs by ciliated protozoa, 2) potential impact of CNTs on aquatic microbial population composition, 3) potential utilization of unicellular organisms as environmental monitoring tools for waste CNT detection.We investigated the interactions of water soluble CNTs with unicellular organisms, in particular ciliated protozoa and bacteria, which are abundant in natural fresh water. Using T. thermophila as an example organism, our result shows that microorganisms could effectively incorporate CNTs into natural organic matter (NOM), and therefore into normal ecological processes[1]. Further, CNTs induced egestion of viable bacteria in membrane enclosed vesicles by ciliated protozoa. This form of egested bacteria aggregates was able to escape digestion by protozoa, proliferate, and resist antibiotics / disinfectant treatment, which may have important implications to public health. This study highlights the importance of ecotoxicology studies of nanoparticles as effects on a single-organism can extrapolate to organisms at different trophic levels in an ecosystem. Finally, T. thermophila, an important organism in waste water treatment, was explored as a tool for removal and detection of CNT contaminants in natural aqueous environment.Reference:1. P. Ghafari, C. H. St-Denis, M. E. Power, X. Jin, V. Tsou, H. S. Mandal, N. C. Bols, X. S. Tang, Nat. Nanotechnol. 3, p. 347.
K17: Non-Carbon Nanostructures II
Session Chairs
Annick Loiseau
Yoke Khin Yap
Thursday PM, December 03, 2009
Room 302 (Hynes)
4:00 PM - **K17.1
Polymeric Composites of BN Nanotubes and Nanosheets.
Yoshio Bando 1 , Chunyi Zhi 1 , Chengchun Tang 1 , Dmitri Golberg 1
1 World Premier International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), Japan, Tsukuba, Ibaraki, Japan
Show Abstract One of the amazing properties of boron nitride (BN) materials is that they are electrically insulating and possess very high thermal conductivity (for example, theoretically, for single-walled BNNTs (BNNTs), more than 3000 W/mK). Combining with other advantages of BN materials, such as great structural stability, chemical inertness, and super mechanical strength, BN materials can be unique nanofillers to make highly thermo-conductive insulating composite materials or composites with high mechanical strength. In addition, for improvement of thermal conductivity and/or mechanical reinforcement, nanomaterials, such as one-dimensional nanotubes, two-dimensional nanosheets etc have attractive advantages based on their high aspect ratio. We work on development of novel low dimensional BN nanofillers for composite materials, followed by polymeric composite fabrication. We have been able to produce grams level highly pure BNNTs by a novel CVD method.1 Further characterization reveals their high elastic modulus, super oxidation resistance etc.2 Moreover, through a liquid exfoliation method, ultra-thin two dimensional BN nanosheets were fabricated; the nanosheets possess nanosize thickness (down to 1.2 nm) and microsize lateral area.3 Utilizing the novel BN nanofillers fabricated, Polymer/BNNTs composites were fabricated. With 1wt. % BNNTs’ fraction, elastic modulus of matrix was improved up to 21 %.4 In addition, due to specific surface properties, BN nanosheets were found to be more effective for mechanical reinforcement: with only 0.3 wt.% BN nanosheets fraction, 22% increase of matrix’s elastic modulus was observed. In addition, we also develop various highly thermo-conductive insulating polymeric composites. A filtering-absorbing method was adopted to embed high fraction of BNNTs in matrix.5 By this method, with 24wt.% BNNTs’ fraction, the thermal conductivity of matrix can be 20-folded. The coefficient of thermal expansion was also remarkably reduced and electrical insulation was kept. The overall performance of the obtained composite materials was thoroughly investigated. Our studies indicates the low dimensional BN nanomaterials, such as BNNTs, BN nanosheets, are very promising fillers for composite materials to obtain high thermal conductivity, high electrical resistance, low coefficient of thermal expansion and high mechanical strength etc. References,1. C. C. Tang, Y. Bando, etc, Chem. Commun. 2002, 1290.2. D. Golberg, Y. Bando, etc, Adv. Mater. 2007, 19, 2413.3. C. Y. Zhi, Y. Bando, etc, Adv. Mater. 2009, 21, 1.4. C. Y. Zhi, Y. Bando, etc, J. Mater. Res. 2006, 21, 2794.5. C. Y. Zhi, Y. Bando, etc, Adv. Funct. Mater. 2009, 19, 1.
4:30 PM - K17.2
Superhydrophobicity of Boron Nitride Nanotubes.
Chee Huei Lee 1 , Jaroslaw Drelich 2 , Yoke Khin Yap 1
1 Department of Physics, Michigan Technological University, Houghton, Michigan, United States, 2 Department of Materials Science and Engineering, Michigan Technological University, Houghton, Michigan, United States
Show AbstractSuperhydrophobic materials have gained significant research interest due to its potential applications as self-cleaning and antifouling coatings on a surface, based on their water repelling properties. Artificial superhydrophobic surfaces can usually be achieved by creating micro/nanostructures on intrinsically hydrophobic surfaces. Hydrophobic organic materials such as fluorinated polymers, olefins, fluorinated hydrocarbons, and silicon-based hydrocarbons are frequently used. The disadvantage of these organic materials is that they are deteriorated at high temperatures or under UV irradiations.Here we report on superior hydrophobic coatings using boron nitride nanotubes (BNNTs) grown directly on Si substrates [1, 2]. We found that BNNTs can achieve superhydrophobic state with the advancing water contact angle (CA) exceeding 150°, especially when aligned almost vertically to the substrate surface. In contrast to BN thin films, the CA is measured to be ~50°. Furthermore, superhydrophopicity of BNNTs is achievable in the full pH range (pH 1 to pH 14). In addition, our results shown that superhydrophobicity of BNNT films strongly depends on its surface morphology. We found that the number of tubes in contact with water drop affects the CA measurements, subsequently affecting the area of the water droplets in contact with the air pockets formed in between the BNNTs. This correlation follows the prediction by the Cassie-Baxter equation [3]. Since BN is chemically inert, having resistance to oxidation at temperatures up to 1000 °C, and transparent to visible-UV light, turning BN into a superhydrophobic structure opens the prospect of using it as self-cleaning, transparent (up to 5.9 eV), insulating, and anticorrosive coatings under rigorous chemical and thermal conditions. Details of these results will be discussed in the meeting.[1]. J. Wang et al, Nano Letters 5, 2528 (2005)[2]. C. H. Lee et al, Nanotechnology 19, 455605 (2008)[3]. C. H. Lee et al, Langmuir (Letter) 25, 4853 (2009) Yoke Khin Yap acknowledges support from the National Science Foundation (CAREER Award No. 0447555). This project is in part supported by the Department of Energy, the Office of Basic Energy Sciences (Grant No. DE-FG02-06ER46294).
4:45 PM - K17.3
On the Relation of Mechanical Deformation and Electrical Properties of BN Nanotubes.
Hessam Ghassemi 1 , Reza Shahbazian Yassar 1 , Yoke Khin Yap 1 , Chee Huei Lee 1
1 , Michigan Technological University, Houghon, Michigan, United States
Show AbstractTheoretical calculations show that bending of boron nitride nanotube (BNNT) reduces the energy difference between highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), called band gap. Using a novel in-situ TEM holder, we have shown that BNNT structure can convert from insulator to semi-conductor upon bending. To measure the electrical properties, the BNNT was bent between two gold contacts constructing a metal-semiconductor-metal circuit. The resistivity (R~dV/dI) of the BNNT measured ~260 MΩ under bending condition. Interestingly, the value of resistivity was directly related to the amount of bending. Therefore under a specific angel of bending the resistivity, i.e. band gap energy was fixed.
5:00 PM - K17.4
Real-Time Compressive Measurements of Individual Titanium Dioxide Nanotubes.
Tolou Shokuhfar 1 , Ganesh Arumugam 2 , Patricia Heiden 2 , Reza Shahbazian-Yassar 1 , Craig Friedrich 1
1 Mechanical Engineering, Michigan Technology University, Houghton, Michigan, United States, 2 Chemistry, Michigan Technological University , Houghton, Michigan, United States
Show AbstractThe mechanical compressive properties of individual thin-wall and thick-wall TiO2 nanotubes were directly measured for the first time. Nanotubes with outside diameters of 75 and 110nm and wall thicknesses of 5nm and 15nm, respectively, were axially compressed inside a 400 keV high-resolution transmission electron microscope (TEM) using a new fully integrated TEM-atomic force microscope (AFM) piezo-driven fixture for continuous recording of the force-displacement curves. Individual nanotubes were directly subjected to compressive loading. We found that the Young’s modulus of titanium dioxide nanotubes depended on the diameter and wall thickness of the nanotube and is in the range of 23-44GPa. The thin-wall nanotubes collapsed at ~1.0-1.2μN during axial compression.
5:15 PM - K17.5
A New Class of Boron Nitride Nanotubes via the Pressurized Vapor/Condenser Method.
Michael Smith 1 , Kevin Jordan 3 , Cheol Park 2 , Jae-Woo Kim 2 , Peter Lillehei 1 , Roy Crooks 1 , Joycelyn Harrison 1
1 , NASA LaRC, Hampton, Virginia, United States, 3 , Jefferson Lab, Newport News, Virginia, United States, 2 , National Institute of Aerospace, Hampton, Virginia, United States
Show AbstractTo date, boron nitride nanotubes (BNNTs) have been grown by two general methods: `high temperature’, mainly represented by electric arc and laser vaporization, and `low temperature,’ mainly represented by ball-mill/annealing and chemical vapor deposition. High temperature methods produce genuinely fullerenic nanotubes; i. e., tubes with just one or a few walls that are defined by smooth planes of hexagonal boron nitride (h-BN) parallel to the tube axis. High temperature tubes have been of high quality, but so far difficult to produce beyond the milligram level. Low temperature methods are easier to scale, but the morphologies are frequently not fullerenic. NASA, Jefferson Lab, and the National Institute of Aerospace have developed a new high temperature technique for producing fullerenic BNNTs, which we call the `pressurized vapor/condenser’ (PVC) method. The PVC method is catalyst-free, using only boron and nitrogen as reactants. The bulk raw material produced by the PVC method has extraordinary length scales making it cotton-like in form and capable of being processed with textile methods (e. g. spinning). The raw material forms in natural fibrils about 10 cm in length, and in aggregate, palm-sized `cotton balls’ over 15 cm in length. A centimeters-long section of yarn spun directly from such a PVC-grown BNNT `cotton ball’ will be shown. Also, video data will be presented to demonstrate the extraordinary speed at which BNNTs grow by the PVC method. In the video, ten centimeter-long fibrils form in a high-speed assembly line. Each fibril takes just 100 milliseconds to grow to its full length, showing the scale-up capability of the technique. Also, the raw material has an unusually high surface area. Two hundred milligrams completely fills a 10 cm by 10 cm jar. A battery of microscopy and chemical analyses will show that the high-quality, fullerenic nature of the raw material is preserved, even at this high rate of production. Specifically, the small-diameter, highly-crystalline, low-defect, h-BN walls of the tubes will be shown through scanning electron microscopy, atomic force microscopy, high resolution transmission electron microscopy (TEM), electron energy loss spectroscopy, and energy-filtered TEM. The extraordinary length of the tubes and their bundles will also be shown. Tube bundles over 100 microns in length were commonly seen in the raw material and in BNNT composites.
5:30 PM - K17.6
First Success in the Synthesis of Boron Nitride Nanoribbons and Hetero-junctions of Boron Nitride Nanotubes and Carbon Nanotubes.
Jiesheng Wang 1 , Chee Huei Lee 1 , Vijaya Kayastha 1 , Yoke Khin Yap 1
1 , Michigan Technological University, Houghton, Michigan, United States
Show Abstract We report here the first success in growing two novel types of boron nitride based nanostructures: 1) single crystalline boron nitride nanoribbons (BNNRs), and 2) hetero-junctions of boron nitride nanotubes and carbon nanotubes (BNNTs/CNTs hetero-junctions). BNNRs are structurally identical to hexagonal boron nitride (h-BN) but in the form of nanoribbons. The structures of BNNRs are also different from boron nitride nanowires (BNNWs), which have recently been reported. All the reported works on BNNWs are having polycrystalline and fiber-like structures. In addition, high growth temperatures (> 1100 °C) were required for the synthesis and thus have prevented their growth on Si substrates. These BNNWs are dominated by impurities and sometimes mixed with fiber-like boron nitride nanotubes (BNNTs). The growth of our single crystalline BNNRs was conducted by thermal chemical vapor deposition (CVD) at 800 °C. Our approach is similar to the growth of our BNNTs, which was performed in a simple horizontal tube furnace with a quarts chamber [1]. However, the growth temperature for BNNRs is much lower. Moreover, the growth locations of the BNNRs are highly controllable, just like the patterned growth of BNNTs that we have achieved by plasma-assisted pulsed-laser deposition [2]. BNNTs/CNTs hetero-junctions are expected to have appealing properties that are not available from pure BNNTs and CNTs. The growth of BNNTs/CNTs junctions was hindered by the absent of a common growth technique for both types of nanotubes. At Michigan Technological University, we have succeeded to grow pure BNNTs and pure CNTs by a series of techniques including thermal chemical vapor deposition (thermal CVD). Based on this unique capability, we have succeeded in growing two types of BNNTs/CNTs junctions: 1) branching junctions and 2) co-axial junctions by thermal CVD. Both BNNRs and BNNTs/CNTs hetero-junctions were characterized by various optical spectroscopy and electron microscopy. Details of these results and the possible growth mechanism will be discussed in the meeting. [1]. C. H. Lee et al, Nanotechnology 19, 455605 (2008) [2]. J. Wang et al, Nano Letters 5, 2528 (2005) Yoke Khin Yap acknowledges support from the National Science Foundation (CAREER Award No. 0447555). This project is in part supported by the Department of Energy, the Office of Basic Energy Sciences (Grant No. DE-FG02-06ER46294).
5:45 PM - K17.7
Preparation and Catalytic Properties of Hollow BN Spheres-supported Ni.
Toshimasa Oohashi 1 , Yuting Wang 1 , Yasunori Yamamoto 1 , Shiro Shimada 1
1 , Hokkaido University, Sapporo Japan
Show AbstractHollow boron nitride spheres (HBNS) have a potential to be used as catalyst supports, because of their outstanding properties as high thermal stability, oxidation, and corrosion resistance. Nickel metal is known as a catalyst for hydrogen production. In this study, hollow BN spheres-supported Ni (Ni/HBNS) were synthesized and characterized, and their catalytic activity for hydrogen production from methanol was investigated. Amorphous boron nitride (a-BN) spheres were produced by heating BH3NH3 in two independently temperature-controlled double deck furnaces at 200 °C and 700 °C in N2. When a-BN spheres were heated in NH3 at high temperatures (>1300 °C), their surface layers were crystallized with inside core parts remaining amorphous. Treatment of these core-shell structured BN spheres in a nickel formate (Ni(HCOO)2) solution at 95 °C, dissolved amorphous cores by H2O with crystallized shell part left, resulting in the formation of HBNS covered with Ni(OH)2 films. It is assumed that Ni(OH)2 is formed as a result of reaction of nickel formate with NH3 released by dissolution of a-BN by H2O. By reduction with hydrogen, nickel hydroxide changed to metal-nickel, that is, Ni-deposited HBNS were formed. The HBNS and Ni/HBNS were characterized by XRD, FT-IR, SEM and TEM. It was found that the diameter and thickness of crystallized shell of h-HBNS were 200-800 nm and 20-60 nm, respectively, with the diameter of deposited Ni particles ranging from 5 to 30 nm. A catalytic property of hollow BN spheres-supported Ni for decomposition of methanol to H2 was investigated. γ-Al2O3-supported Ni (Ni/Al2O3) was used for comparison, it was revealed that Ni/HBNS catalyst exhibited a better selectivity for decomposition of methanol to H2 than that of Ni/Al2O3.
K18: Poster Session: Physical Properties and Applications
Session Chairs
Friday AM, December 04, 2009
Exhibit Hall D (Hynes)
9:00 PM - K18.1
Transport Property Shift due to Hybrid Formation of Single-Walled Carbon Nanotubes with Single Strand DNA.
Seungwon Jung 1 , Misun Cha 2 , Moon-Hyun Cha 3 , Gunn Kim 3 , Jisoon Ihm 3 , Junghoon Lee 1 4
1 Mechanical & Aerospace Engineering, Seoul National University, Seoul Korea (the Republic of), 2 Institute of Advanced Machinery and Design, Seoul National University, Seoul Korea (the Republic of), 3 FPRD and Department of Physics and Astronomy, Seoul National University, Seoul Korea (the Republic of), 4 Interdisciplinary Program for Bioengineering, Seoul National University, Seoul Korea (the Republic of)
Show AbstractSingle strand DNA (ssDNA) forms an interesting hybrid with single-walled carbon nanotube (SWNT). It has been initially observed that the ssDNA wraps around the SWNT through π-stacking, forming the hybrid which can be well dispersed in water. Recent research is focused on the mechanism and changes in physical properties resulting from the hybrid formation. Here we present a direct observation of the transition from a metallic SWNT to a semiconducting one by forming the hybrid with ssDNA. Following an alignment and deposition of the hybrid on electrode gaps by using a dielectrophoretic force, electrical property was measured with the back gate sweeping. It was discovered that water is essential in activating the transition due to the charge interaction between the DNA and its surrounding water molecules. SWNTs with metallic dominant sample were dispersed in an aqueous solution with the ssDNA by sonication, forming the hybrids. Au was patterned to fabricate a nanoscale gap device by nanoimprint lithography (NIL). The conductivity change of the SWNT was measured on the gap device after depositing the hybrids by dielectrophoresis (DEP) across the electrodes. The electrical response of the ssDNA-SWNTs was measured by field effect transistor (FET) configuration. The source-drain current was measured with the gate voltage swept from -15 V to +15 V. According to our observation the current of the ssDNA-SWNT hybrids in the dry state was independence of the gate voltage, showing a metallic behavior. On the other hand those in the wet state manifest the behavior of a p-type semiconductor. This result demonstrates that the transport characteristic of the SWNT is significantly altered by the existence of the DNA and the water.Raman spectroscopy was used to further investigate the effect of water on the metal-semiconductor transition. The G-band shows a clear change in the electronic structure of the ssDNA-SWNT hybrid in water. The G-band of the ssDNA-SWNT hybrid in dry state shows strong broad and asymmetric BWF line which represents the metallic property. After an injection of water into the identical sample, however, the electronic properties were changed considerably. The BWF line was greatly diminished and shifted to a higher frequency. First-principles electronic structure calculations were also performed to additionally understand the experimental observations. Through the calculations, it was found that the SWNT donates a fraction of an electron to negatively charged AMP surrounded by water molecules and becomes a p-type semiconductor due to the opening of the band gap. This metal-semiconductor transition of ssDNA-SWNT hybrids will provide critical information for applications such as nano-bio sensing and gene/drug delivery.
9:00 PM - K18.10
Tuning Transport in Nanotube FETs by Low-Energy Electron Irradiation.
Tsz Chan 1 , Brian Burke 1 , Michael Cabral 2 , Hu Chong 2 , Joe Campbell 2 , Lloyd Harriott 2 , Keith Williams 1
1 Physics, University of Virginia, Charlottesville, Virginia, United States, 2 Electrical and Computer Engineering, University of Virginia, Charlottesville, Virginia, United States
Show AbstractWe studied the effect of low energy electron beam on carbon nanotube field effect transistors. We show that the transport behavior of these devices can be reversibly tuned by electron beam exposure and with in situ gating. A partial n-type behavior can be obtained by exposing a device held under positive gate bias, while ambipolar behavior can be obtained when the device is held under a negative gate bias. The tuned transport behavior is relatively stable in time. Possible mechanisms for the observed phenomenon will be discussed.
9:00 PM - K18.11
Temperature Dependence of Carbon Nanofiber Resistance.
Hisashi Yabutani 1 , Toshishige Yamada 1 , Tsutomu Saito 2 , Cary Yang 1
1 Center for Nanostructures, Santa Clara University, Santa Clara, California, United States, 2 , Hitachi High-Technologies, Hitachinaka Japan
Show Abstract Carbon nanofiber (CNF) is a promising candidate for next-generation on-chip interconnects because of its excellent electric and thermal conductivities and high current capacity. From our recent study on test structures of CNFs attached to tungsten-gold (W-Au) electrodes [1], we observed a reversible reduction in CNF resistance (during each constant-current stress cycle) with increasing stress current. Here we present a method to determine the temperature dependence of CNF resistance, based on a heat transport model developed recently by our group [2]. This study can lead to potential application of CNF in a temperature-sensing device. Current stressing measurement is performed on a single CNF bridging two W-Au electrodes, formed by depositing W with focused ion beam on Au-CNF contacts [1]. The stress current in each cycle corresponds to a specific temperature distribution along the length of the nanofiber [2]. The measured average resistance during each stress cycle is then related to an average CNF temperature obtained from this temperature profile. Since the increase in temperature originates from Joule heating of the CNF, and since we established that current stressing has little effect on contact resistance [1], this result suggests that the reversible resistance change due to Joule heating is a result of change in bulk CNF properties at elevated temperatures. We explain this observation in the context of trapping/detrapping of electrons in CNF. The traps are present as result of inherent defects formed during CNF growth [3]. The effect of thermally activated detrapping of electrons can account for the decrease in resistance as the CNF temperature is increased. As the temperature returns to ambient, the electrons are again trapped, giving rise to the reversible resistance change observed. Such thermal activation can be characterized by an Arrhenius behavior for the electrical conductivity, from which the activation energy is extracted using our data. We confirm that the values of extracted activation energy (~30 meV) are completely consistent with results of our previous study for vertically aligned CNF via structures. Our present results strongly suggest the use of CNF as a nanoscale temperature-sensing material.[1] T. Saito, T. Yamada, D. Fabris, H. Kitsuki, P. Wilhite, M. Suzuki, and C. Y. Yang, “Improved contact for thermal and electrical transport in carbon nanofiber interconnects,” Applied Physics letters 93, 102108(1-3) (2008).[2] T. Yamada, T. Saito, D. Fabris, and C. Y. Yang, “Electrothermal Analysis of Breakdown in Carbon Nanofiber Interconnects,” IEEE Electron Device Letters 30, 469–471 (2009).[3] Q. Ngo, T. Yamada, M. Suzuki, Y. Ominami, A. M. Cassell, J. Li, M. Meyyappan, and C.Y. Yang, “Structural and Electrical Characterization of Carbon Nanofibers for Interconnect Via Applications,” IEEE Trans. Nanotechnology 6, 688-695 (2007).
9:00 PM - K18.12
A First-principles Assessment of Schottky Barrier Heights in CNT-metal Junctions.
Nicholas Singh-Miller 1 , Nicola Marzari 1
1 Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractWe study Schottky barrier heights (SBHs) in carbon nanotube (CNT) - metal junctions using pseudopotential plane-wave density functional calculations. We focus on the effects that surface roughness, functionalization, or chemisorption have on SBHs with respect to the pristine system. Al(111) and Pd(111) surfaces are taken as examples of low and high work-function metals, contacted with a semiconducting (8,0) CNT. In all cases we find that a surface dipole forms, that locally shifts the band structure of the CNT; control of this electrostatic dipole would directly control the SBH. However, this seems to be locally influenced by the geometry of the CNT-metal contact, chemisorption, and chemical functionalizations. These affect the dipoles at the interface and drive the band energies of the CNT up or down, ultimately altering the SBH. We find that the CNT/Al junctions are more susceptible to SBH changes due to external interactions than the CNT/Pd junctions.
9:00 PM - K18.13
Direct Electrical Probing of Individual Carbon Nanotubes.
Patrick Wilhite 1 , Xuhui Sun 1 , Ke Li 1 , Raymond Wu 1 , Cary Yang 1
1 , Santa Clara University, Santa Clara, California, United States
Show AbstractContinuous downward scaling of feature size and performance demands in the nanoelectronics industry have driven researchers to search for suitable new materials for next-generation chip manufacturing. Vertically aligned carbon nanostructures have potential in via applications due to their low resistivity and high current capacity [1]. For on-chip via interconnect applications, it is necessary to measure the electrical characteristics as the nanostructures are incorporated into devices consisting of other materials. The resulting device structure introduces new interfaces (such as electrode contacts) and contact resistances that critically impact the performance and reliability of the entire system.In this study, we utilize two commercially available techniques to characterize vertically aligned carbon nanotubes and nanofibers in a via interconnect configuration. The accompanying instruments, atomic force microscope operating in the conductive mode (C-AFM) and piezo-actuated nanoprober, are used to measure the resistance of individual nanotubes grown on a suitable metal underlayer. The results enabled us to develop a contact resistance extraction technique using C-AFM [2]. In addition, using the nanoprober in a four-point configuration, we determine the carbon nanotube resistivity directly, which, together with other measured electrical and materials properties, allows us to continuously improve the materials growth and device fabrication processes accordingly. Thus, this direct probing of nanostructures can be used as a process characterization tool for research and development of nanowires and nanotubes for applications in integrated circuit technology. The methodology is completely applicable to any one-dimensional nanoscale system.[1] International Technology Roadmap for Semiconductors-Interconnect: http://www.itrs.net/Links/2007ITRS/2007_Chapters/ 2007_Interconnect.pdf[2] W. Wu, S. Krishnan, T. Yamada, X. Sun, P. Wilhite, R. Wu, K. Li, and C.Y. Yang, “Contact resistance in carbon nanostructure via interconnects,” Applied Physics Letters 94, 163113 (1-3) (2009).
9:00 PM - K18.16
High-performance Solution-deposited Flexible, Transparent Electrodes from Carbon Nanotube-conjugated Polymer Composites.
Sondra Hellstrom 1 , Hang Woo Lee 2 , Zhenan Bao 2
1 Applied Physics, Stanford University, Stanford, California, United States, 2 Chemical Engineering, Stanford University, Stanford, California, United States
Show AbstractFlexible transparent electrodes are crucial for touch screen, flat panel display, and solar cell technologies. While carbon nanotube (CNT) network electrodes show promise, their fabrication typically either suffers from poor morphology or involves incorporation of highly insulating surfactants which substantially worsen network conductivity. Instead, we show that small amounts of conjugated semiconducting polymer added to nanotube dispersions enables straightforward, direct fabrication of network electrodes by spin-coating or drop casting, and that these electrodes are uniform and highly functional without polymer removal. After treatment in thionyl chloride, electrodes as good as 175 ohm/sq with 81% transmittance, or 80 ohm/sq with 72% transmittance, at 550 nm are obtained. Further, the electrodes may be patterned concurrently with deposition, and the morphology of the networks is systematically tunable by changing the chemistry and processing of the composite.
9:00 PM - K18.17
Spontaneous Electron Transfer from C60 to Au Ions: Oxidation of C60 and Fabrication of p-type C60 Field Effect Transistor.
Hyeon Suk Shin 1 , Hyunseob Lim 2 , Hyun Jae Song 2 , Hyun-Joon Shin 2 , Su-Moon Park 2 , Hee Cheul Choi 2
1 , Ulsan National Institute of Science & Technology, Ulsan Korea (the Republic of), 2 , Pohang University of Science and Technology, Pohang Korea (the Republic of)
Show AbstractFullerene (C60)-based p-type semiconductor was realized via spontaneous oxidation of C60 by Au ions. When C60 was guided to make contacts with Au3+ ions in aqueous HAuCl4 solution, electrons were spontaneously transferred from C60 to Au3+ ions, resulting in hole (h+) doped C60 cations and Au nanoparticles on C60 layer. This spontaneous electron transfer occurs due to the galvanic displacement from C60 to Au3+ ion owing to the energy difference between Fermi energy level of C60 (-4.7 eV) and standard reduction potential of Au3+ ion (+1.002 V). The successful hole doping in C60 as well as consequent formation of reduced Au nanoparticles were confirmed by atomic force microscopy, X-ray photoelectron spectroscopy, electrochemistry and contact angle measurement. The switch of majority charge carrier type from electron to hole and its stability in air were also confirmed by monitoring I-Vg characteristic curves of C60 film and C60 wire-based field effect transistor (FET) devices before and after the reaction with Au3+ ions.
9:00 PM - K18.18
Enhancing the Electrical Properties of Carbon Nanotube Wires and Ribbon Connectors.
Brian White 1 , Craig Lombard 1 , Meghann White 1 , David Lashmore 1
1 , Nanocomp Technologies, Concord, New Hampshire, United States
Show AbstractCopper wire conductors, with an 8.9 g/cm^3 density, are universally used throughout various industries because of good electrical conductivity and availability. However, for some applications, where considerations of weight, oxidation resistance, strength and fatigue are concerned, copper wire has serious performance deficiencies. We have the ability to produce wires and ribbon connectors composed of pure carbon nanotubes (CNTs) on the bulk scale with a density of 0.2 g/cm^3. Our as-produced CNT material has a conductivity of 1.25 x 10^5 to 5 x 10^5 S/m. A strategy for reducing the resistivity of the nanotube ribbon connectors and wires is to introduce trace amounts of foreign atoms or molecules (doping) during growth or during a subsequent processing step. Several different methods of doping will be presented with varying degrees of success. These highly conductive wires and ribbons have been used to construct both power and data transmission cables with comparable performance and significant weight savings.
9:00 PM - K18.2
Systematic Study of Work Functions of Single-walled Carbon Nantotubes.
Koichiro Kato 1 , Susumu Saito 1
1 Physics, Tokyo Institute of Technology, Oh-okayama, Meguro-ku, Japan
Show AbstractEver since the discovery of carbon nanotubes (CNTs), many experimental and theoretical works have been devoted to them. The electronic structure of CNTs sensitively depends on the diameter and chirality. Therefore, it is very important to know the accurate electronic properties of CNTs for any possible electronic application. In the present work, we perform the systematic study of work functions (WFs) of 44 kinds of isolated single-walled carbon nanotubes in the framework of the density functional theory. The WF is one of the crucial quantities in understanding their field emission properties and applying CNTs to electronic devices. It has been revealed that the first principles calculations play quite important roles for predicting various properties of carbon nanotubes. Moreover, we have to perform the structural relaxation in order to know the accurate electronic properties of CNTs [1]. Therefore we carry out the complete geometrical relaxations for 44 kinds of CNTs and evaluate their WFs. The diameters (D) of calculated nanotubes are about 0.3 < D < 2.0 nm. Especially, we focus on the WFs of small diameter CNTs. We determine WF values from the difference between the Fermi level and the vacuum level. In the semiconducting CNTs, the Fermi level is chosen at the midgap. As a result, it is found that the CNTs should be classified into three classes according to the D dependence of WFs. The WFs of class I CNTs (D > 0.7 nm) have no significant dependence of their diameters and chiral-angles. Their values are very close to that of graphene. For class II CNTs (0.45 < D < 0.7 nm), the sizable chiral-angle dependences of the WFs are observed. Class II nanotubes have moderate distributions of their WFs in the range from 4.5 to 5 eV and they show continuous variations. Finally, The WFs of class III CNTs (D < 0.45 nm) have very large values above 5 eV except for armchair nanotubes. Zigzag CNTs have larger WFs than chiral nanotubes both in the class II and in the class III regions. Interestingly, armchair CNTs have almost the same values about 4.5 eV in the whole regions. Although, the classification of The CNTs into I and II has been pointed out previously [2]. The presented remark has clarified that CNTs should be classified into three types according to the diameter dependence of work functions.K.K. acknowledges the financial support from the Global Center of Excellence Program by MEXT, Japan through the "Nanoscience and Quantum Physics" Project of the Tokyo Institute of Technology. [1] K. Kanamitsu and S. Saito, J. Phys. Soc. Jpn. 71, 483 (2002) [2] B. Shan and K. Cho, Phys. Rev. Lett. 94, 236602 (2005)
9:00 PM - K18.21
Field Emission Response from Multiwall Carbon Nanotubes Grown on Different Metallic Substrates.
Indranil Lahiri 1 , Raghunandan Seelaboyina 1 , WonBong Choi 1
1 Mechanical & Materials Engineering, Florida International University, Miami, Florida, United States
Show AbstractIn recent years, carbon nanotubes (CNT) have seen a wide variety of applications, spread well beyond the semiconductor industries - especially in field emission related devices. In order to reduce the interfacial resistance, it has become very much important to grow CNTs on a variety of metallic substrates and understand their field emission response. In the present study, multiwall CNTs (MWCNT), grown on pure metallic substrates like Cu, Al and W, were subjected to field emission tests under DC and AC bias. Choice of diffusion barrier layer and catalyst was also varied, to verify their effects on the emission response. Field emission behaviors from all such structures were compared with MWCNTs grown on Si. It was found that the MWCNTs grown on pure Cu substrate showed excellent field electron emission response, in terms of low turn-on field, high emission current, long time stability and very high field enhancement factor.
9:00 PM - K18.22
Comparing Field Emission Stability of Lithography-free, Modified Multi-walled Carbon Nanotubes.
Archana Pandey 1 , Abhishek Prasad 1 , Jason Moscatello 1 , Yoke Khin Yap 1
1 , Michigan Technological University, Houghton, Michigan, United States
Show AbstractField emission from carbon nanotubes (CNTs) was known for more than a decade, but reliable commercial products are yet to be realized. Obviously, the basic science for stable field emission with high emission density is still not clear. Most reported work focus on demonstrating low emission threshold fields (Eth) of various types of CNTs and their device configuration. Although these techniques are able to reduce threshold electric field for emission but long-term emission stability is scarcely discussed. Emission stability and lifetime are essential characteristics required for any material to be suitable for use in practical field emission devices. Recently, we started to investigate factors that determine the emission stability of CNTs and found that the graphitic order of CNTs is one of the key factors for stable emission [1]. Here we describe our efforts to increase the long-term emission stability as well as keeping the emission threshold electric field low. We have found two simple and effective techniques (without lithography processes) for improving field emission stability of vertically-aligned multiwalled carbon nanotubes (VA-MWCNTs): 1) self-assembled conical bundles of opened-tip VA-MWCNTs, 2) Opened-tip VA-MWCNTs embedded in poly-methyl methacrylate (PMMA). The opened-tip conical nanotube bundles were prepared by acid etching of the residual Ni catalysts at the tips of as grown VA-MWCNTs. The etched samples will self-assembled in to regular arrays of conical bundles. The PMMA embedded samples were prepared by over-coat as-grown VA-MWCNTs with PMMA and follow by mechanical polishing to expose their tips. All these samples were then compared for their current density versus applied electric field (J-E) properties, long-term emission stability for continuous emission, as well as their emission site densities, in a high-vacuum chamber (x10-7 mbar) [2]. Theoretical simulation was also performed to scrutinize the actual reasons behind the improved performances of these modified nanotubes.The threshold electric field (Eth), defined as E required for emitting electrons to a level of 1 µA/cm2, was 3.58 V/µm for as-grown sample. The opened-tip, conical nanotube bundles prepared from a simultaneously grown sample was reduced to Eth = 3.09 V/µm. In another set of as grown samples, Eth was detected as 4.403 V/µm and was reduced to Eth = 1.90 V/µm after embedded into PMMA. In addition, the PMMA-embedded, opened-tip sample showed a significant improvement in emission stability as compared to the as-grown CNT sample. Details of all these results will be discussed in the meeting.[1] B. Ulmen et al., Diamond & Related Materials 15, 212 (2006).[2] V. K. Kayastha et al., Nanotechnology 18, 035206 (2007).Yoke Khin Yap acknowledges support from the U.S. Army Research Laboratory and the Defense Advanced Research Projects Agency (Contract number DAAD17-03-C-0115).
9:00 PM - K18.23
The Impact of Densification on the Physical and Electrical Properties of Carbon Nanotube Materials.
Jack Alvarenga 1 , Christopher Schauerman 1 , Paul Jarosz 1 , Brian Moses 1 , Tom Mastrangelo 1 , Peggy Walsh 1 , Elizabeth Gorse 1 , Brian Landi 1 , Ryne Raffaelle 1
1 NanoPower Research Labs, Rochester Institute of Technology, Rochester, New York, United States
Show AbstractElectrically conductive and mechanically robust bulk carbon nanotube (CNT) ribbons and wires have been investigated as replacements for conventional copper wiring in the aerospace industry, including electrical harnesses and photovoltaic arrays. The primary appeal of implementing CNTs is the possibility of reducing the payload mass and enhancing current carrying capacity of the interconnects. The present work evaluates the electrical and mechanical properties of commercially produced CVD CNT materials. A manual drawing die process was used to alter the form factor of wet CNT ribbon segments, cut from larger CNT sheet material, to highly densified wires with diameters ranging from 0.30 to 0.75 mm. This technique requires a wetting agent for the ribbon before the drawing process can begin. Prior to characterization, all the wire samples are dried in a muffle furnace at 200°C to remove any excess moisture. Initially, deionized water was applied to the CNT ribbon segments to permit densification. Four point probe electrical conductivity measurements of the densified wires vary with changes in polarity of the wetting agent. For similar wire bulk densities (approximately 1000 kg/m3), CNT wires densified with deionized water yielded an average electrical conductivity of 1.4x105 S/m whereas an average electrical conductivity of 2.1x105 S/m was observed when the wetting agent was N,N-dimethylacetamide. To achieve even larger bulk electrical conductivities (1.3x106 S/m), a gold ion doping solution was applied to the CNT ribbons prior to drawing. It has been observed that both mechanical strength and electrical conductivity significantly increase (across samples composed of the same material) as the bulk density of the wire increases. Increasing the bulk density of a CNT wire fabricated with a deionized water wetting agent from 600 to 1100 kg/m3 results in an increase of the ultimate breaking force of the wires from 14 to 24 Newtons and the Young's modulus from 13 to 50 MPa. Experimentation with additional solvents, wire twisting during fabrication, polymer additives, and CNT purity also offer the prospect of further enhancement of the electrical and mechanical properties of these wires.
9:00 PM - K18.24
Electrically Conductive CNT/PTFE Composite Film for Corrosion Resistant Coating on Bipolar Plate of Fuel Cell.
K. Takahashi 1 , R. Nishimura 1 , K. Kohara 1 , Y. Fukami 1 , H. Murata 1 , Yoshiyuki Show 1
1 Dept. of electrical and electronic engineering, Tokai University, Hiratsuka Japan
Show AbstractCarbon nanotube (CNT) is chemically stable and electrically conductive material. One of the applications of the CNT is filler into insulating materials for decreasing its electrical resistivity. In this study, composite film was formed from the carbon nanotube (CNT) and the polytetrafluoroethylene (PTFE). This composite film is electrically conductive and highly corrosion resistance. Therefore, it is suitable material for corrosion resistant coating on bipolar plate of the fuel cell.The CNT/PTFE composite film was formed from dispersion fluids of the CNT and the PTFE. CNT dispersion was made from multi-wall type CNT. Cellulose derivatives were added into water to disperse the CNT. Water based commercial PTFE dispersion was used in this study. The dispersion fluids of the CNT and the PTFE were mixed and stirred by applying the ultrasonic wave.The CNT/PTFE dispersion was applied to stainless steel bipolar plate at the thickness 50micro m. The bipolar plates were dried under the atmosphere of 40oC for 30 min, and then were heated at 350oC for 10min. Pure PTFE showed the low electrical conductivity below measuring limit. The composite material of 5% CNT showed high conductivity of 0.1 S/cm. The conductivity increased up to 20 S/cm with an increase in the CNT concentration in the film. This result indicates that the CNTs form the electrical network in the material and modify the PTFE into electrically conductive material.Polymer exchange membrane fuel cells were assembled with either bare stainless steel bipolar plates and the bipolar plates coated with the CNT/PTFE composite film. The fuel cell using the bare stainless steel bipolar plates showed the output power of 2.0W. The composite film coating to the bipolar plates increased the output power up to 2.7W. Impedance analyzer measurement for these fuel cells indicated that the composite film coating decreased the contact resistance between the bipolar plate and the MEA, because the composite film prevents the bipolar plate surface from corroding. These results indicate that the CNT/PTFE composite film is useful as anticorrosion coating to bipolar plate of fuel cell.In this presentation, polarization curve measurement for the bipolar plate coated with CNT/PTFE composite material will be also discussed.
9:00 PM - K18.25
Nano-silver Coated Carbon Nanotubes for Conductive Pastes.
Youngseok Oh 1 , Kyoungyong Chun 2 , Youngjin Kim 1 2 , Seunghyun Baik 1 2 3
1 SKKU Advanced Institue of Nanotechnology (SAINT), Sungkyunkwan Univ., Suwon, Gyeonggi-do, Korea (the Republic of), 2 School of Mechanical Engineering, Sungkyunkwan Univ., Suwon, Gyeonggi-do, Korea (the Republic of), 3 Department of Energy Science, Sungkyunkwan Univ., Suwon, Gyeonggi-do, Korea (the Republic of)
Show AbstractThe conductivity of silver paste was significantly improved by the incorporation of nano-silver coated carbon nanotubes. The surface of carbon nanotubes was coated with the self-assembled nano-silver clusters leading to a substantial reduction in interfacial contact resistance. The conjugation mechanism is based on the π-π interactions between side-walls of carbon nanotubes and nano-silver clusters functionalized with benzyl mercaptan. The conductivity of the nanotube-incorporated paste was increased up to 1300 % compared with the control sample without nanotubes. The mechanism was investigated using X-ray photo electron spectroscopy and transmission electron microscopy. The nanotube-incorporated conductive paste might find immediate industrial applications as interconnect materials for multi-layer circuit boards.
9:00 PM - K18.26
Effects of Structural Disorder on the Electrical Characteristics of Graphene.
Kanghyun Kim 1 , Haeyong Kang 1 , Nam Hee Lee 1 , Byung-Chill Woo 1 , Wan Soo Yun 1
1 , Korea Research Institute of Standards and Science, Daejeon Korea (the Republic of)
Show AbstractAlthough the honeycomb lattice carbon crystal is considered to be inert, graphene has an interesting sensitivity to circumstances, such as gas, electron beam, and chemical reagent. It has been reported that such characteristics may be induced or enhanced by disorders and ripples inside graphene or by interaction with the substrate underneath. Here, we have studied the effect of a structural disorder on the electrical properties of a graphene device such as conductance, transconductance, low frequency noise, and magnetoresistance. Those transport properties of the defective graphene was successfully described with the models of continuum percolation and the variable range hopping. The anomalous magnetoresistance under a tilted magnetic field was observed and discussed with modified interference between electron motions in multi-layer graphene.
9:00 PM - K18.27
Carbon Nanotube-GNR Structures: Modeling of Formation, Elastic and Electronic Properties.
Leonid Chernozatonskii 1 , Anastasiia Artyukh 1 , Kseniya Bets 3 1 , Pavel Sorokin 2 1
1 Material Research, Institute of Biochemical Physics, Russian Academy of Sciences , Moscow, Moscow, Russian Federation, 3 physics, D. Mendeleyev University of Chemical Technology of Russia , Moscow Russian Federation, 2 Physics, Siberian Federal University, Krasnoyarsk, Krasnoyarsk, Russian Federation
Show AbstractA new class of carbon nanostructures is considered: covalently (or molecularly) bound carbon nanotube (CNT) and graphene nanoribbon (GNR) fragments. As found using methods of molecular dynamics and density functional theory, we have constructed the energetically stable structures formed by covalent bonding GNR edge atoms to nanotube atoms arranged at the CNT cylinder and some similar GNRs-CNTs systems. The elastic and electronic properties of separate one (or two) CNT - one (or up 6) GNR covalent-bonded structures and their one- (and two) dimensional superlattices have investigated. It has been shown that such structures have more higher elastic modules because rigid GNR edges forming on the CNT. Electronic spectra of such structures qualitatively can be described as sum of separate spectra of GNR and CNT with H-atoms situated on the sp3 -added line. That is why it is possible to organize the GNR-CNT structures with different semiconductor behaviors.If a GNR fragment is arranged at a distance of ~0.35 nm from a nanotube the Van der Waals interaction can attach it to the surface of the tube or penetrate to CNT. We have shown that the GNR-CNT VdW systems are more flexible than separate CNTs. We have also considered the thermal process how the structures are formed by moving GNRs between CNTs or penetrating into CNTs.It is evident that the proposed new materials exhibit an extremely wide range of electronic and mechanical properties and they can be in great demand for various physico-chemical applications.
9:00 PM - K18.30
Thermal Conductivity of Confined CNTs.
Ali Aliev 1
1 NanoTech Institute, University of Texas at Dallas, Richardson, Texas, United States
Show AbstractThermal conductivity and thermal diffusivity of individual and bundled SWNTs and MWNTs embedded into different polymer matrices was measured by laser flash and 3-omega methods. Substantial decrease of thermal diffusivity observed for individual and bundled nanotubes surrounded by polymer matrix is resulted by increase of thermal inertia (ρC). However the decrease of the thermal conductivity mostly induced by suppression of low energy phonon modes involving out-of-plane atom vibrations.
9:00 PM - K18.31
Thermal and Structural Characterizations of Individual Carbon Nanotubes.
Michael Pettes 1 , Li Shi 1 2
1 Mechanical Engineering, The University of Texas at Austin, Austin, Texas, United States, 2 Texas Materials Institute, The University of Texas at Austin, Austin, Texas, United States
Show AbstractIndividual single- (S), double- (D), and multi- (M) walled (W) carbon nanotubes (CNTs) suspended between two micro-thermometers are characterized by thermal transport measurements and transmission electron microscopy (TEM). For the first time, the thermal conductance, diameter, and chirality are measured on the same single-walled SWCNT and the thermal conductance of a DWCNT is measured. The thermal contact resistance to a MWCNT sample is determined from thermal measurements before and after deposition of platinum-carbon composites at the contacts. The obtained intrinsic thermal conductivity of about 200 W m-1 K-1 at room-temperature for this CVD-grown MWCNT sample correlates well with TEM observed effective grain size of approximately 30 nm; whereas the effective thermal conductivity is found to be limited by the thermal contact resistance to be approximately 600 W m-1 K-1 at room temperature for the DWCNT and SWCNT samples with the diameter and chirality determined by TEM but without contact depositions. Analysis based on the measured thermal conductance of individual CNTs shows that even contact-dominated CNTs promise one to two orders of magnitude performance enhancement when they are employed as thermal interface materials.
9:00 PM - K18.32
Properties and Applications of Carbon Nanotube Fibers by Dry Spinning of Super-aligned Carbon Nanotubes.
SeongWoo Ryu 1 , JaeWon Hwang 1 , SoonHyung Hong 1
1 , Korea Advanced Institute of Science and Technology, Taejon Korea (the Republic of)
Show AbstractCarbon nanotubes(CNTs) have extraordinary mechanical, thermal and electrical properties due to their unique carbon based structure. However, the application of CNTs as nano-sized tubular form makes it difficult to utilize those outstanding properties. In this research, continuous carbon nanotube fibers are spun from the super-aligned carbon nanotubes forest grown by plasma enhanced chemical vapor deposition(PECVD) process. By using dry spinning process, well-aligned CNT fibers of having high bonding strength between the CNTs have been successfully manufactured. Highly oriented CNT fibers by dry spinning process can have characteristics of high strength and modulus, which can be potentially applied as ultra-light and high strength structural materials such as space elevator cable, artificial muscle, and armour material. Also, they can be widely applied as multi-functional materials such as E-texile, touch pannel, biosensor, supercapacitor, and FED.
9:00 PM - K18.33
Low-field Actuation of High-performance Polyimide Nanocomposites via Resistive Heating.
Aaron Sellinger 1 , Huabin Wang 1 , Loon-Seng Tan 1 , Richard Vaia 1
1 , Air Force Research Laboratory, Wpafb, Ohio, United States
Show AbstractThe novel property combinations offered by polymer nanocomposites (PNC) afford unique opportunities for sensor and actuator-based devices. Carbon nanotube (CNT) additives, both below and above percolation, have been shown to reduce the electric-fields required to induce actuation by up to two orders of magnitude in various electrostrictive and piezoelectric polymers. This behavior is commonly attributed to local electric-field modification and charge accumulation within the PNC. Alternatively, the low percolation thresholds and tunable conductivity afforded by CNTs can also promote actuation via resistive (Joule) heating at relatively low applied fields. Infrared imaging of polyimide (CP2) nanocomposites containing single wall nanotubes (SWNTs) and carbon nanofibers (CNFs) reveals temperature increases in excess of 225 °C at fields no greater than 0.006 MV/m applied in-plane. Thus, depending on the mechanical boundary conditions employed, thermal expansion driven buckling or mechanical softening of the polymer at Tg (209 °C) can result in macroscopic strains of up to 2%. Upon removal of the field, convective cooling is estimated to occur at rates in excess of 104 °C/s, suggesting reversible strain cycling may operate at frequencies above 0.5 kHz. Consequently, under the application of an AC voltage, both the temperature and shape of the PNC oscillate in accordance with the applied frequency, with maximum strains exceeding those previously reported by over two orders of magnitude for a given applied field.
9:00 PM - K18.34
Individual and Coupled Single-walled Carbon Nanotube Resonators through Direct Stamping.
Chung Chiang Wu 1 , Zhaohui Zhong 1
1 Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan, United States
Show AbstractSingle-walled carbon nanotubes are 1D ballistic conductors with Young’s modulus of ~ 1TPa. Their unique electrical and mechanical properties make them ideal building blocks for novel nanoelectromechanical systems (NEMS). Here we demonstrate a powerful yet simple technique for fabricating individual and couple nanotube NEMS resonators. Through a one-step stamping technique, CVD grown nanotubes are directly transferred and suspended across pre-fabricated electrodes, eliminating the organic residue contaminations from conventional lithography. More importantly, multiple devices on the same nanotube are readily formed by using this technique, enabling the first studies of coupled nanotube NEMS resonators. In addition, the suspended nanotube devices are inherently clean and free of defects. Low temperature electron transport studies taking advantages of such a clean system will also be discussed.
9:00 PM - K18.35
Enhancement of Composite-metal Interfacial Adhesion Strength by Grafting Carbon Nanotube onto Alumina Surface.
Yanping Peng 1 , Qiwen Guo 2 , Yibin Li 3 , Xiaodong He 3
1 , Ministry of Industry and Information Technology of the People’s republic of China, Beijing, Beijing, China, 2 , Beijing Institute of Technology, Beijing, Beijing, China, 3 , Harbin Institute of Technology, Harbin, Heilongjiang, China
Show AbstractThe interface between carbon fiber reinforced polymer composites and metal plays a critical role in determining the strength of laminated composites. The carbon nanotubes were grafted onto alumina surface aiming to enhance the interfacial adhesion strength between polymer and metal, thus more effectively transfer the load. In this paper, we focus on the preparation of carbon nanobute onto the alumina surface by introducing a nanolayer of dendrimer. It shows that one highly stable and nano-patterned dendrimer layer was dip-coated onto different treated alumina substrates by adsorbing poly (amido amine) (PAMAM) dendrimers. The characterization results indicate that the dendrimer is adsorbed to the alumina via acid-base chemical interactions. The adsorption study reveals that the adsorption is controlled by the concentration, reaction time, and especially the hydroxylation degree of alumina surface. The carbon nanotubes were confirmed to be grafted onto the dendrimer-coated alumina surface.
9:00 PM - K18.36
Mechanism, Optimization and Thermal Boundary Resistance of Metal Deposition onto Vertically Aligned Single-Walled Carbon Nanotube Arrays.
Hai Duong 1 3 , Matt Panzer 2 , Kei Ishikawa 3 , Jun Okawa 3 , Kazuaki Ogura 3 , Erik Einarsson 3 , Junichiro Shiomi 3 , Shigeo Maruyama 3 , Kenneth Goodson 2 , Brian Wardle 1
1 Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 Mechanical Engineering, University of Tokyo, Tokyo Japan, 2 Mechanical Engineering, Stanford University, Stanford, California, United States
Show AbstractVertically aligned single-walled carbon nanotubes (VA-SWNTs) have attracted much attention as promising materials for next-generation thermal and electrical devices because of their extraordinary thermal and electrical properties. Although possibilities for single-channel devices with an individual SWNT have been extensively explored, bulk SWNT materials in the form of mats and films are expected to play an important role in near-future applications due to their handling and cost efficiencies. Regarding applications of VA-SWNT films as thermal and electrical devices, metal film coating is an important element technology for integration and probing intrinsic properties. The metal-SWNT interaction is a primary issue as the contact resistance significantly influences the performance and the electrical/thermal conductance due to the large carrier mean-free-paths. Reports on the strong dependence of SWNT transport characteristics on metal type have motivated vacuum-evaporation experiments for various metals and deposition conditions, which revealed strongly metal-dependent morphologies. VA-SWNT arrays grown by the alcohol catalytic CVD method were coated with thin films of Ti, Pd, Au, and Al by evaporative deposition. Scanning electron microcopy showed the Ti and Pd coatings were continuous or quasi-continuous, whereas Au and Al agglomerated into discrete deposits on SWNT bundles. The mechanism of metal film formation on VA-SWNT arrays was studied by observing the film at various stages of the depositing process. Uniformity of the deposition was also found to be strongly dependent on the deposition conditions, such as substrate temperature, deposition rate, and deposition thickness. The optimization of the deposition conditions was demonstrated for Pd. The results suggest that the deposition efficiency for a smooth coating layer is determined by the balance of two processes with significantly different speeds: the coating along a VA-SWNT bundle and coating of an interbundle, which depend on the metal type and the deposition conditions. In order to improve upon the thermal performance of VA-SWNT arrays and develop models for the thermal transport in nanostructured contacts, the interface resistance between metallic films and the tips of VA-SWNT arrays grown on Si is measured by ultra fast transient optical thermometry (picosecond and nanosecond). These findings will be useful regarding both fundamental and practical aspects of VA-SWNT applications in thermal and electronic devices.
9:00 PM - K18.37
Dynamical Behavior of Thermally Controlled Double Walled Carbon Nanotube Oscillators.
Vitor Coluci 1 , Varese Timoteo 1 , Douglas Galvao 2
1 Faculty of Technology, State University of Campinas, Limeira, SP, Brazil, 2 Applied Physics Department, Institute of Physics , State University of Campinas, Campinas, SP, Brazil
Show AbstractThe proposition of a device composed of double walled carbon nanotubes that can lead to oscillations of the inner tube at frequencies of ~ 1 GHz by Zheng and Jiang [1] has stimulated further works on similar nanomechanical devices [2-4]. For these devices, the inner nanotube can move inside the outer one with very low friction. The oscillatory motion is induced and maintained by van der Waals interactions between the inner and the outer tubes. One key issue regarding these devices is how to initialize them in a controllable way. Different strategies have been proposed to start the oscillatory movements, such as application of magnetic and electrical fields, encapsulation of charged elements in the inner tube, etc. In this work we propose the use of heat to initialize and control the oscillators. This approach is based on recent findings that demonstrated the possibility of producing nanoscale thermal motors [5]. We have used numerical and atomistic classical molecular dynamics simulations to investigate the motions of the inner nanotube. Our results indicate that a thermal gradient can be effective to initiate the oscillators. Furthermore, suitable heat pulses (e.g., generated by electrical currents) may provide an appropriate way to tune some of the oscillators features, such as, their frequencies. We observed that the overall behavior is dictated by the heat pulse frequency and form, as well as by the thermal gradient format. We observed self-sustained (i.e., regular oscillatory motions) as well as chaotic motions on the devices proposed here.[1] Q. Zheng and Q. Jiang, Phys. Rev. Lett. 88, 045503 (2002); [2] S.B. Legoas, V. R. Coluci, S. F. Braga, P. Z. Coura, S. O. Dantas, D. S. Galvao, Phys. Rev. Lett. 90 55504 (2003); [3] P. Tangney, S. G. Louie, M. L. Cohen, Phys. Rev. Lett. 93 065503 (2004); [4] J. Servantie, P. Gaspard, Phys. Rev. B 73 125428 (2006); [5] A. Barreiro, R. Rurali, E.R. Hernandez, J. Moser, T. Pichler, L. Forro, A. Bachtold, Science 320 775 (2008).
9:00 PM - K18.38
Carbon Nanotube Assisted Electrical Treeing for Vascular Network Synthesis.
Kristopher Behler 1 , Eric Wetzel 1
1 Multifunctional Materials Branch, U.S. Army Reseach Lab, Aberdeen Proving Ground, Maryland, United States
Show AbstractElectrical Treeing (ET) was performed in an epoxy system to produce a continuous branched network of hollow tubules. By growing the trees from the electrode to the ground, an intricate pathway is produced that allows for filling of the structure with applications in self-healing materials, thermal management and fluid transport. Multi-walled Carbon Nanotubes (MWCNTs) were used to increase the local electric field around the needle electrode and promote tree initiation. Various configurations of the electrode and ground were used to optimize tree growth and subsequent filling. A needle-needle configuration allowed for possible switching of the electrode to grow two trees toward each other while maintaining the same geometry throughout the experiment. A needle-plane setup was employed to grow trees in a specific direction while trying to maximize the number of branches that penetrate to the air, thus providing more exit sites for infused liquid. A needle-cylinder geometry was used to produce two large outlets for the branches to be able to empty into. Needles and the various grounds were coated with thin layers of metal to allow for self-clearing to promote many branches to grow to a designated distance and provide many more channels for filling without short circuiting the system. Both AC and DC current were used to grow trees in different manners. AC-treeing, performed at 20 kV peak to peak harnessing a sine wave at 100 Hz, promotes more “bush-like” trees in which more high-order branches are produced. DC-treeing, performed at up to (-) 60 kV, generates more low order branches that tend to grow directly to the ground from the lead electrode and resemble more of a riverbed or canyon system. The electrical trees were then filled with dyed liquid to show the ability to fill various structures with another external material.
9:00 PM - K18.39
Carbon Nanotube-confined MnO2 Nanocomposites for Electrochemical Capacitors.
Chunlei Wang 1 , Wei Chen 1 , Kevin Bechtold 1 , Majid Beidaghi 1 , Varun Penmatsa 1
1 Mechanical and Materials Engineering, Florida International University, Miami, Florida, United States
Show AbstractElectrochemical Capacitors (ECs) with substantially higher power densities, faster recharge rate and longer cycle lifetimes are the ideal electrical energy storage technologies for meeting future energy demands. However, energy densities of ECs are generally lower than those of batteries and are insufficient for many applications in which significant energy storage is needed. Here, we are using carbon nanotube (CNT) confined MnO2 composite as electrode materials of ECs, i.e., combining double layer (e.g., CNTs) and pseudocapacitive (e.g., MnO2) types into one capacitor. Cyclic voltammetry shows that the CNT-confined MnO2 exhibit typical rectangle shape and have a higher specific capacitance compared to the composites of MnO2 coated on CNT’s outer surface. We attribute this improvement to the synergetic enhancement in the pseudocapacitance of MnO2 inside CNTs. In addition, Electrochemical impedance spectroscopy will be measured to analysize the pseudocapacitive behaviors of CNT-confined MnO2 and the related diffusion process of electrolyte, which will help us to understand how the active materials store/transport charge and further optimize the electrochemical energy storage systems.
9:00 PM - K18.40
Opto-mechanical Coupling in Multiwalled Carbon Nanotubes.
Fragneaud Benjamin 1 , Jeffrey Kysar 1
1 Mechanical Engineering, Columbi University, New York, New York, United States
Show AbstractAmong different coupling properties, it has been recently proposed that carbon nanotubes can undergo some dimensions transformation when exposed to visible light [1]. The authors concluded that they observed distinct movements of the single walled nanotubes without precising the dimension of the mechanical actuation. Finally they addressed the nature of the opto-mechanical coupling to the highly coupled thermal, electrical, optical and mechanical properties of this peculiar material. Few evidence of nanotube opto-mechanical actuation has been reported in the literature since then [2]. More recent papers have shown that when the carbon nanotubes are dispersed in a polymer matrix the composite material is able to expand or contract depending on the pre-stress applied to the material [3]. In order to explain the composite material deflection the nanotube actuation has been assumed to be equivalent to an isotropic compression along the nanotube longitudinal axis on an uncompressible material. However there is no experimental evidence of such a phenomenon. In this work we expose a direct observation of the opto-mechanical coupling in carbon nanotube by using a nano-indenter as a displacement sensor. Then we explored the impact of different parameters such as the nanotube length, light intensity or tube dispersion. Finally we also propose a mechanism to explain this phenomenon and perform calculus by using density functional theory (DFT). It appears that the variations of the electron population densities between the valence band and the conductive band induced due to photon absorption results in carbon nanotube actuation mechanical contraction. [1] Zhang, Y. and S. Iijima (1999). Physical Review Letters, 82(17): 3472-3475.[2] Lu, S. X. and B. Panchapakesan (2005). Nanotechnology, 16(11): 2548-2554.[3] Lu, S. X. and B. Panchapakesan (2007). Nanotechnology, 18(30): 8.
9:00 PM - K18.43
Fabrication and Fracture Toughness of Nanotube Reinforced Nanocrystalline Diamond Coatings.
Sugeetha Vasudevan 1 , Brian Sheldon 1
1 Division of Engineering, Brown University, Providence, Rhode Island, United States
Show AbstractAll carbon composite coatings consisting of nanocrystalline diamond (NCD) matrices reinforced with carbon nanotubes (CNTs) are of interest because of their potential for high fracture toughness. Combined with the extremely high hardness and low friction of the NCD matrix, these composites are promising as wear resistant coatings for cutting tools and orthopedic implants, and in other possible applications such as MEMS structures and biosensors. The fabrication of these composite coatings poses problems because of the delicate balance between the simultaneous etching of the nanotubes during the NCD growth process. Also the CNTs can act as a potential source for diamond growth, which creates difficulties in controlling the uniform fabrication of the NCD matrix around the nanotube reinforcements. An analysis of these processing issues and an approach for engineering these NCD composites are reported here. Also, the fracture toughness of the composite coatings was measured with a novel indentation method that is designed to avoid delamination problems that can lead to erroneous fracture toughness values during direct indentation testing of thin films.
9:00 PM - K18.44
Carbon Nanotube Assembly for Flexible Transparent Electrodes.
Mei Zhang 1 2 , Farag Abdelsalam 1 2 , Chuck Zhang 1 2 , Ben Wang 1 2
1 High Performance Materials Institute, Florida State University, Tallahassee, Florida, United States, 2 Department of Industrial and Manufacturing Engineering, FAMU-FSU College of Engineering, Tallahassee, Florida, United States
Show AbstractFlexible electronics such as a flexible display panel has long been a dream and is under rigorous development nowadays. Indium tin oxide (ITO) films are commonly used as transparent conductive films because of their superior transparency to visible light and high electrical conductivity. However, ITO coatings on flexible substrates are brittle or fail by cracking when the substrates undergo dimensional changes, which results in lowering of electrode electrical conductivity and efficiency of the display device. Due to carbon nanotube’s (CNT) unique mechanical, electronic, and physical properties, CNT films are capable as flexible, lightweight, low-cost alternatives for ITO coatings. We developed a solid-state process to fabricate transparent CNT sheets. In this work, the process of making flexible transparent electrodes using CNT sheets will be presented. The structures and properties of the electrodes will be observed, measured, and discussed.
9:00 PM - K18.45
Effect of Multi-walled Carbon Nanotubes on the Structure and Thermal Properties of Poly(Vinylidene Fluoride).
Wenwen Huang 1 , Kyle Edenzon 2 , Luis Fernandez 3 , Shabnam Razmpour 2 , Jenna Woodburn 4 , Peggy Cebe 1
1 Physics, Tufts University, Medford, Massachusetts, United States, 2 Department of Biological Sciences, Rochester Institute of Technology, Rochester, New York, United States, 3 Department of Science and Mathematics, Rochester Institute of Technology, Rochester, New York, United States, 4 Department of Chemistry and Physics, Gallaudet University, Washington, District of Columbia, United States
Show AbstractWe report the preparation and characterization of nanocomposites of Poly(vinylidene fluoride) (PVDF) with mutiwalled carbon nanotubes (MWCNT) with a wide composition range, from 0.1 % to 5.0 % MWCNT by weight. The purpose of this study is to determine separate effects of MWCNT addition and uniaxial drawing of PVDF on the phase transition from non-polar alpha phase to polar beta phase in PVDF, and their impact on the thermal and mechanical properties of the PVDF/MWCNT films. Effect of uniaxial orientation by zone drawing on these nanocomposites is discussed and compared with unoriented compression molded films. Room temperature two-dimensional wide angle X-ray scattering and Fourier transform infrared spectroscopy were used for PVDF crystal phase identification. Differential scanning calorimetry, dynamic mechanical and thermogravimetic analyses were used to study the thermal properties. Results indicate that: 1) incorporation of MWCNT in PVDF induces a small portion of beta phase crystal in the PVDF/MWCNT bulk films, while zone drawing causes a significant alpha to beta transition; 2) MWCNTs act as nucleation agents during crystallization but do not change the glass transition temperature. A higher glass transition can be obtain by zone drawing; 3) Storage modulus increases when MWCNT concentration increases. Zone drawing causes a higher storage modulus along the draw direction for PVDF/MWCNT films in general; 4) thermal stability is improved when MWCNT concentration increases.ACKNOWLEDGEMENTSFor support of this work the authors thank the National Science Foundation, Polymers Program of the Division of Materials Research, through DMR-0704056 and the MRI Program under DMR-0520655 for thermal analysis instrumentation. Summer interns KE, LF, SR and JW thank their American Sign Language interpreters: Mark Riley, Diane McKeon, and Francine Graff-James. The internship and the work reported herein were performed at Tufts University.
9:00 PM - K18.46
Chemically Driven, Carbon Nanotube-Guided Thermopower Waves.
Wonjoon Choi 1 2 , Joel Abrahamson 2 , Jaehee Han 2 , Changsik Song 2 , Michael Strano 2
1 Mechanical Engineering, MIT, Cambridge, Massachusetts, United States, 2 Chemical Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractCoupling an exothermic chemical reaction with a nanotube or nanowire possessing high axial thermal conductivity creates a self propagating reactive wave along its length. Phonon mean free path becomes commensurate with the length contacting with nanotube, and this system makes an enormous acceleration of reactive wave. Such waves are realized using a 7 nm cyclotrimethylene-trinitramine (TNA) annular shell around a multi-walled carbon nanotube and are amplified by more than 10000 times the bulk TNA value (0.2mm/s), propagating more than 2 m/s. This directional thermal wave produces a concomitant electrical pulse of disproportionately high specific power, as large as 20 kW/kg, that we identify as a thermopower wave. The wave traverses the system faster than the region behind which the wave can cool by atmospheric condition, and electrons are entrained in this thermal wave, producing a high power pulse. As the thermal gradient is preserved in the propagation of the wave front, thermopower waves do not necessarily require low phonon and high electron transport rates like conventional thermoelectric material. High phonon electron transport-material like nanotube can be used to generate high specific thermopower. The specific power of such thermopower waves demonstrates an unusual inverse scaling with system size, highlighting their utility as sub-micron and nano-sized pulse power sources. Moreover, the reaction in arrays of nanotubes with TNA annular shell produces an anisotropic pressure wave of exceedingly high total impulse per mass of 300 N-s/kg and specific impulse per total mass (5.5 s/µg) having applications to micro-propulsion and actuators.
9:00 PM - K18.47
Thermal Conductance of Hot Electrons in Individual Single-Walled Carbon Nanotubes.
Daniel Santavicca 1 , Joel Chudow 1 , Anthony Annunziata 1 , Luigi Frunzio 1 , Meninder Purewal 2 , Philip Kim 2 , Daniel Prober 1
1 Dept. of Applied Physics, Yale University, New Haven, Connecticut, United States, 2 Depts. of Physics and Applied Physics, Columbia University, New York, New York, United States
Show AbstractCarbon nanotubes are attractive for device applications in part because of their ability to support extremely large current densities. This can lead to significant Joule heating, and hence self-heating effects are important in determining the performance of nanotube-based devices. These self-heating effects also provide a tool for studying the electrothermal properties of this unique one-dimensional conductor. We report low temperature characterizations of individual metallic single-walled carbon nanotubes on insulating substrates. With ohmic (low resistance) contacts, the increase in dc resistance with increasing bias current is attributed to Joule heating of the electron system. We confirm this self-heating description using Johnson noise thermometry. Thus, the dc resistance is a direct probe of the average electron temperature. This enables a straightforward determination of the thermal conductance for cooling of the out-of-equilibrium electron system. We study both the length- and temperature-dependence of the thermal conductance. The results are described by a model based on acoustic phonon scattering, hot electron outdiffusion, and the high-bias onset of scattering with surface polar phonons in the substrate. This work is supported in part by NSF-CHE and Yale University.
9:00 PM - K18.48
Dynamic Mechanical Analysis of Bulk Carbon Nanotube Materials.
Brian Moses 1 , Paul Jarosz 1 , Jack Alvarenga 1 , Christopher Schauerman 1 , Brian Landi 1 , Ryne Raffaelle 1
1 NanoPower Research Labs, Rochester Institute of Technology, Rochester, New York, United States
Show AbstractHigh purity single wall carbon nanotube (SWCNT) papers, produced via laser vaporization synthesis, have been successfully fabricated into form factors similar to copper cables, such as flat ribbons and wires. There are several factors which determine the physical properties and Van der Waal forces between individual SWCNTs including alignment, densification, impurities, and additives. Characterizing the response in the physical properties, such as tensile strength, by altering the local environment can lead to improvements in the breaking stress (MPa) of the bulk papers. Alternatively, the forces between nanotubes can be augmented by filling void spaces with compounds that bond well to nanotubes, and morphological changes to the material through the degree of purification and inclusion of impurities, dopants, and other compounds have a distinct effect on the mechanical properties. Characterization is performed using a Q800 dynamic mechanical analyzer (DMA) from TA Instruments, which allows measurement of tensile strength, elastic modulus, planar coefficients of thermal expansion, and bending fatigue life.In this work, various purification and processing techniques for laser produced SWCNT material are investigated while characterizing changes to the mechanical properties. The mechanical properties of SWCNT papers are measured as a function of carbonaceous purity, controlled via thermal oxidation and acid reflux, up to >95% SWCNT w/w. It has been observed that maximum stress (MPa) for a SWCNT ribbon is dependent on the weight percentage of amorphous carbon present in the material. Measurements of the tensile strength for the bulk SWCNT materials have exceeded 200 MPa. In addition, a negative planar thermal expansion of a nanotube paper is experimentally observed, and adsorbed gases in the carbon nanotube paper can change the thermal coefficient of expansion. The results suggest that composites containing SWCNT materials can be produced into lightweight, conductive products with a neutral coefficient of expansion.
9:00 PM - K18.49
Thermal and Electrical Properties of Composites Consisting of Carbon Nanotubes Dispersed in a Compacted Granular Media.
Michael Depriester 2 , Abdelhak Hadj Sahraoui 2 , Philippe Hus 2 , Frederick Roussel 1
2 , Universite du Littoral-Cote d'Opale, Dunkerque France, 1 , Universite Lille 1, Villeneuve d'Ascq France
Show AbstractTransport properties of composite materials made of conductive fillers dispersed in organic or inorganic matrices are of main scientific interest. Due to their exceptional physical and mechanical properties, carbon nanotubes (CNTs)[single-walled (SWNT) and multiple-walled (MWNT)] are now considered as promising filler substitutes. Indeed, CNTs have been shown to possess higher thermal and electrical bulk conductivities compared to their graphite-containing composite counterparts. However, experimental measurements of thermal parameters usually provide significant lower values than those obtained from numerical calculations based on geometrical models. Numerous factors have been invoked to explain these observations such as nanotube characteristics (diameter,length, chirality, etc.), the architecture of the nanotube network, the physical characteristics of interfaces (interfacial resistance). In this work, we report on the thermal and electrical properties of composite materials made of SWNTs or MWNTs dispersed in a compacted granular medium (potassium bromide, KBr). These consolidated/nanostructured granular composites can be considered as model system for experimental (e.g., wave propagation) and technical (e.g., thermal management) investigations. The thermal conductivity (k) of CNT/KBr composites is investigated as a function of CNT mass fraction using photothermal radiometry. The electrical conductivity measurements are carried out using the conventional collinear four point probe method. A significant enhancement of both thermal and electrical conductivities for CNT contents up to 2 wt% was observed. Above 3 wt% CNT, a morphological transition from a compacted to an unconsolidated granular media occurs leading to a sharp decrease of k caused by the presence of air interfaces. A geometrical model based on interpenetrating continua is applied to describe the unusual evolution of the thermal conductivity. In contrast, the electric transport along the percolating network is kept.M. Depriester, A. Hadj Sahraoui, P. Hus, F. Roussel, Appl. Phys. Lett. 94, 231910 (2009)
9:00 PM - K18.50
Assessment of Electrical Conductivity Enhancement Treatments and Mechanisms for Carbon Nanotube Conductors for Aerospace Applications.
Ed Silverman 1 , John Starkovich 1 , Hsiao-hu Peng 1 , Scott Gilje 1 , David Lashmore 2 , Brian White 2 , Ryne Raffaelle 3
1 , Northrop Grumman, Redondo Beach, California, United States, 2 , Nanocomp Technologies, Inc., Concord, Maine, United States, 3 , Rochester Institute of Technology, Rochester, New York, United States
Show AbstractVarious doping and treatment studies for enhancing electrical conductivity of commercially-produced carbon nanotube (CNT) engineering product forms (yarn, braid and sheet materials) were undertaken to reduce conductor weight and improve properties for different space applications. Target applications included power and data cables along with EMI shielding. Comparative assessments were made of conductivity enhancements obtained with dopants such as alkali, halogen, chalcogenide, acid, super-acid, along with organic functionalization. Surface treatments such as extraction, pulsed-galvanostatic and direct current electrodepostion, high temperature annealing, e-beam and X-ray exposure were also explored. Conductivity enhancements of more than 80 percent were measured for several of the dopant treatments. Thermo-vacuum stability and temperature coefficient of resistivity for selected product treatments were evaluated and frequency-dependent impedances assessed. Conductivity improvement were found to correlate with dopant ion size. Hall measurements and Raman spectroscopy were also employed to understand enhancement mechanisms. Based on findings from these studies further improvements in their effectiveness were indentified. Possible enhancement mechanisms considered included: (1) Defect decoration, (2) CNT carrier density improvement, (3) Intercalation of ionic charge transfer complexes, and finally (4) Inter-tube contact resistance reduction.
9:00 PM - K18.51
Electromechanical Characterization of Carbon Nanotubes in Torsion.
Traian Dumitrica 1 , Dong-Bo Zhang 1
1 , Univ. of Minnesota, Minneapolis, Minnesota, United States
Show AbstractThe nonlinear elastic response of carbon nanotubes (CNTs) in torsion is derived with objective molecular dynamics and a density-functional-based tight-binding model. The critical strain beyond which CNTs behave nonlinearly, the most favorable rippling morphology, and the twist- and morphology-related changes in fundamental band gap are identified. There is a sharply contrasting behavior in the electronic response: While in single-walled CNTs the band gap variations are dominated by rippling, MWCNTs exhibit an unexpected insensitivity. Results are assistive for experiments performed on CNT-pedal devices.
9:00 PM - K18.52
NEMS Based on Relative Vibrations of Carbon Nanotube Walls and Graphene Layers.
Olga Ershova 2 , Irina Lebedeva 1 2 , Elena Bichoutskaia 3 , Andrey Knizhnik 1 , Andrei Popov 4 , Yurii Lozovik 4 , Boris Potapkin 1
2 , Moscow Institute of Physics and , Moscow Russian Federation, 1 , Kintech Lab Ltd, Moscow Russian Federation, 3 , University of Nottingham, Nottingham United Kingdom, 4 , Institute of Spectroscopy, Troitsk Russian Federation
Show AbstractAt the present time a variety of nanoelectromechanical systems (NEMS) that employ carbon nanotube walls or graphene layers as movable elements are being developed. There are two types of motion of carbon layers in such systems: a telescopic motion with large separation of the walls and small vibrations around commensurate position. In both cases vibrational properties of NEMS are determined by van der Walls interaction and matching between carbon layers. However, in the first case van der Walls forces saturate at large wall separation, resulting in non-harmonic behavior of the oscillator, while in the second case relative vibrations are approximately harmonic. Moreover, the telescopic motion of carbon layers can provide small frequencies of relative vibrations for large systems, while in the second case the frequency of relative vibration does not depend on system size.We performed a multiscale investigation of NEMS based on relative vibrations of carbon layers, starting from study of interwall potential up to the operation characteristics at macroscopic times. We applied first-principles methods to compute the interaction energy of the walls of carbon nanotubes and layers of graphene as a function of their relative position. Then we investigated tribological properties of NEMS depending on the parameters and microscopic structure of the system (temperature, length, interwall distance, structure of the walls/layers, defectness, etc.) through molecular dynamics simulations. We found that large interwall distance and defects in carbon layers significantly increase dissipation rate of the oscillator by excitation of perpendicular interwall vibrations.For the use of NEMS, it is essential to control the motion of carbon layers at long operation times. To describe the dynamic behavior of the NEMS at long simulation times we applied a phenomenological model, which was parameterized on the results of molecular dynamics modeling. It was shown that systems based on telescopic motion of carbon layers have limited ranges of phase stability of induced vibrations due to non-harmonic character of these systems. Moreover, we found that thermodynamic fluctuations in these NEMS have a critical effect on the possibility of controlling the NEMS operation. Based on on the Fokker-Plank equation for the energy distribution function of the gigahertz oscillator and calculations with the phenomenological model we found dependences of the lifetime of the stationary operation mode on the parameters of the system. It was shown that the stability of the NEMS operation can be achieved through increasing the amplitude of the control force and the NEMS size.
9:00 PM - K18.53
3D SWNT Thermal Sensors: Design, Fabrication and Characterization.
Selvapraba Selvarasah 1 2 , Ahmed Busnaina 2 , Mehmet Dokmeci 1 2
1 Dept. of Electrical and Computer Engineering, Northeastern University, Boston, Massachusetts, United States, 2 NSF-NSEC for High-rate Nanomanufacturing, Northeastern University, Boston, Massachusetts, United States
Show AbstractNanotechnology enables the realization of small, light weight, inexpensive and miniaturized sensors for diverse applications. Nanoscale materials not only provide greater sensitivity but also can be tailored for specific sensing applications. Carbon nanotubes (CNTs), a one-dimensional nanomaterial, have gained tremendous interest for sensing applications, especially in nanobiotechnology, due to their exceptional physical, mechanical and chemical properties. Most of the current CNT sensors are realized on planar two-dimensional (2D) surfaces. In this paper, we report the design, fabrication and characterization of vertical assembly of 3D SWNTs and investigate their thermal sensing properties. The DEP assembly process parameters have been optimized to create predictable assembly by adjusting the electrode spacing and overall/separation distance between the top and bottom electrodes. Scaling the geometry of 3D microelectrode platform enabled the control over density, bundle thickness, and angle of incline of assembled SWNTs. Then, the thermal sensitivity of single 3D electrode sensors was characterized. We have observed a higher temperature coefficient of resistance (TCR) compared to the previously reported carbon nanotube thermal sensors. The TCR value of the single electrode thermal sensor ranged from-0.08 to -0.24%/°C, whereas the TCR of the multielectrode sensor varied from -0.53 to -0.76%/°C. These thermal sensors exhibited electrical hysteresis during heating and cooling cycles. Even though the resistance has slightly increased during cooling, the obtained TCR value (-0.17 to -0.21%/°C) is quite consistent with that of obtained from heating cycle. The higher sensitivity values obtained from the thermal sensors are due to the 3D geometry of the electrodes which created vertically suspended highly dense SWNT bundles.
9:00 PM - K18.54
Thermoelectric Transport in Individual Sb2Se3 Nanotubes and Nanorods.
Wei Jiang 1 , R. Mehta 1 , C. Karthik 1 , E. Castillo 2 , T. Borca-Tasciuc 2 , G. Ramanath 1
1 Materials Science and Engineering, Rensselaer Polytechnic Institute , Troy, New York, United States, 2 Mechanical Engineering, Rensselaer Polytechnic Institute , Troy, New York, United States
Show AbstractOne-dimensional nanostructures, i.e., nanorods and nanotubes, of chalcogenides have attracted a great deal of attention for solid-state refrigeration and conversion fo heat to electrical power from heat. This is mainly because they offer possibilities for enhancing the thermoelectric power factor from quantum confinement, and decreasing the thermal conductivity by increasing phonon scattering due to size confinement. Here, we report the first-time direct measurements of the Seebeck coefficient α, thermal conductivity κ and electrical conductivity δ in 2-3 μm long Sb2Se3 nanorods and nanotubes of 40-100 nm diameter, synthesized by a rapid microwave method. Test devices are fabricated by e-beam lithography, metallization and lift-off. For α measurements, the device consists of a heater to provide a temperature gradient and two thermometers to sense the gradient and measure the thermoelectric voltage. We used a four-point probe device that employed self-heating of the nanostructures to determine κ, which was validated using a one-dimensional heat transfer model. Our results show a remarkably high δ~700 Ω-1m-1, α~700μV/K and κ~0.8 W/mK. We will present temperature-dependent measurements and correlate the measured properties in terms of the doping levels in the chalcogenide. These results are important for understanding thermoelectric transport properties in materials comprised of nanostructures and their assemblies.
9:00 PM - K18.55
CNT Films for Transparent and Flexible Electronics.
Antti Kaskela 1 , Albert Nasibulin 1 , Brad Aitchison 2 , Anton Anisimov 1 , David Brown 2 , Esko Kauppinen 1 3
1 Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo Finland, 2 , Canatu Ltd., Espoo Finland, 3 , VTT Nanobiotechnology, Espoo Finland
Show AbstractCarbon nanotubes (CNTs) and especially single-walled CNTs (SWCNTs) are of great interest due to their unique and useful physical and chemical properties. For many purposes thin films of CNTs with adjustable physical properties are urgently required. Indeed, CNT film based devices have been already successfully used as gas detectors, transparent conductive coatings and field emitters. Also, they are considered to be strong candidates for ITO replacement in transparent electrodes [1]. An obstacle in the use of CNT films in industrial applications is in their handling. This is due to, among other factors, their high flexibility and specific surface area, the presence of magnetic catalyst particles and their low density. This leads to stickiness of the films to surrounding surfaces, e.g., to manipulating instruments and substrates, and to the folding of films during their treatment which destroys their two dimensional morphology. Therefore, a simple method to stabilize single-walled CNT films and to allow them to be incorporated in a variety of applications is desirable. For this purpose, a method to integrate free CNT films into polymer matrices is useful.We have developed a simple and direct method for the preparation of CNT films with different thicknesses to be easily integrated in polymers. The nanotubes were synthesized by an aerosol method based on the ferrocene vapor decomposition in CO atmosphere and collected directly from the gas phase by the filtering through silver and nitrocellulose filters [2,3]. In addition to simple direct transferring technique, we elaborated a simple thermo-compression method to polyethylene polymer films. As a result, we were able to manufacture transparent, conductive, and flexible CNT containing polymer films. The optical and electrical measurements demonstrated their excellent properties suitable for many electronic applications including field electron emitters and transparent and flexible electronics. [1] Nasibulin, A. G., A. Ollikainen, A. S. Anisimov, D. P. Brown, P. V. Pikhitsa, S. Holopainen, J. S. Penttilä, P. Helistö, J. Ruokolainen, M. Choi, E. I. Kauppinen (2008) Integration of single-walled carbon nanotubes into polymer films by thermo-compression. Chemical Engineering Journal, 136(2-3), 409-413.[2] Nasibulin, A. G., Moisala, A., Brown, D. P, Jiang, H., Kauppinen, E. I. (2005) A novel aerosol method for single walled carbon nanotube synthesis. Chemical Physics Letters, 402(1-3) 227-232.[3] Moisala, A., Nasibulin, A. G., Brown, D. P., Jiang, H., Khriachtchev, L. and Kauppinen, E. I., (2006) Single-walled carbon nanotube synthesis using ferrocene and iron pentacarbonyl in a laminar flow reactor. Chemical Engineering Science, 61, 4393-4402.
9:00 PM - K18.56
Microtubule as a Universal Fourth Circuit Element.
Satyajit Sahu 1 , Anirban Bandyopadhyay 1 , Daisuke Fujita 1
1 Advanced nano characterization center, Natioanl Institute for Materials Science, Tsukuba Japan
Show AbstractInvention of the fourth circuit element H after 150 years of the invention of first three elements resistor (R), capacitor (C) and inductor (L), would open up a new kind of electronics . H correlates magnetic flux with the charge content in a device. Since the rate of change of magnetic flux generates voltage; thus far, H has been designed/realized correlating electrical flux and charge. These devices cannot generate magnetic flux which is essential for the fourth element. They can not generate any new property that cannot be created using R, C and L. Here, we propose a helically symmetric structure for H that is capable of generating/tuning magnetic flux by storing/releasing charge in a quantized manner. An unprecedented coherence of electric and magnetic flux in the helical path of H generates three basic features of the fourth element. First, even though inherent L and C grow/decay together, an ideal H is remarkably linear in its dc output. Second, co-existence of L and C turn an input ac signal 180 degree out of phase, enabling it to cut off noise1 in an assembly/integrated circuit. Third, at a suitable condition, H can store/transport signal losing almost no energy. Microtubules that are responsible for information processing and transport in a living cell exhibit all the properties of H explicitly. H unify discretely reported unique features of microtubules, DNA,helical nanotubes, molecular solenoids, nano-springs for resonators as exemplification of the conceptual fourth element. One application of H would be powering the nano-machines replacing biomotors.
9:00 PM - K18.6
Evaluating Electrostatic Interactions and Field-Effect Transistor Operation of Solution Assembled Carbon Nanotube Networks on Amine Functionalized Surfaces.
Justin Opatkiewicz 1 , Melburne LeMieux 1 , Zhenan Bao 1
1 Chemical Engineering, Stanford University, Stanford, California, United States
Show AbstractSolution deposition of single walled carbon nanotubes (SWNTs) onto self-assembled monolayers (SAMs) containing amine functional groups to produce high quality semiconducting network devices (SWNTnts). When these aminated surfaces were exposed to varying pH solutions, the resulting NT networks were altered. In this work, the chirality, density, and alignment dependence of these networks on pH exposure was examined. Atomic Force Microscopy (AFM) was used to observe variation in the density of CNTs adsorbed on the surface while micro-Raman spectroscopy was used to determine the efficiency of sorting and SWNT chirality. Electrode deposition and device testing was used to determine the influence of the pH treatment on thin film transistor (TFT) performance. Secondary and tertiary amines with methyl substitutions were utilized to confirm that adsorption and sorting capability is related to the nitrogen pair, not the neighboring hydrogen atoms. When the interaction between the amine and SWNTs can be better understood and characterized, this surface sorting technique can be optimized for better TFTs.
9:00 PM - K18.8
Radiation and Temperature Effects in Single-Walled Carbon Nanotube Paper Conductivity.
Cory Cress 1 , Christopher Schaureman 2 , Brian Landi 2 , Scott Messenger 1 , Ryne Raffaelle 2 , Robert Walters 1
1 Solid State Devices, U.S. Naval Research Laboratory, Washington , District of Columbia, United States, 2 NanoPower Research Laboratories, Rochester Institute of Technology, Rochester, New York, United States
Show AbstractThe high conductivity and structural robustness of single-walled carbon nanotubes (SWCNT) has motivated research into their use in applications such as field effect transistors, transparent conductive coatings, electrostatic discharge materials, conductive wires, and many others. The potential for increased performance with concurrent reductions in volume and mass make SWCNT utilization in these applications very attractive for space deployment. In such an environment, however, many new material reliability challenges are encountered including large temperature fluctuations and high fluxes of ionizing radiation. There currently exists a need to assess the effects of ionizing radiation with concomitant thermal cycling to identify potential failure modes associated with utilizing such materials in space. Furthermore, assessing the response of SWCNTs to radiation exposure can increase the fundamental understanding of the transport properties in SWCNT films or papers, and may elucidate new methods for tailoring the structural and electronic properties of SWCNTs to achieve the desired device performance.
This presentation will overview on going research aimed at understanding the effects of ionizing radiation on the electrical conductivity of SWCNT papers. The SWCNT papers studied are comprised of high-purity laser-synthesized SWCNTs, are approximately 35 μm thick, have conductivities of 140 S/cm, and have mechanical properties (yield strength) similar to that of standard printer paper. The SWCNT were irradiated with 4.8 MeV alpha particles and the temperature dependent conductivity was measured in situ at incremental alpha-particle fluences in a high vacuum environment. Analysis of the temperature-dependent conductivity of the SWCNT paper indicates that radiation damage causes increases in the effective energy barrier for tunneling-like conductivity and a concomitant increase in wavefunction localization of charge carriers within individual SWCNTs. Radiation damage modeling incorporates both Monte Carlo simulations and numerical calculations and is used to accurately determine the spatial defect generation density within the SWCNT paper. The modeling results indicate that uniform displacement damage (which simulates the space environment) is achievable with the alpha-particle source utilized, and was subsequently imparted to the SWCNT paper under study. A comparison of the damage coefficient (i.e., differential change in conductivity with fluence) for alpha particles, carbon ions, and protons yields a non-linear relationship with the non-ionizing energy loss (NIEL) imparted to the SWCNT papers by the three incident particles. This indicates that localized damage within SWCNT papers has a greater impact than distributed damage, thus signifying that the radiation response is dominated by the preferred one-dimensional conduction within these two dimensionally confined nanostructures.
9:00 PM - K18.9
Electron Transport in Nanotubes with Defects: A Renormalization Plus Convolution Approach.
Vicenta Sanchez 1 , Chumin Wang 2
1 Departamento de Fisica, Facultad de Ciencias, Universidad Nacional Autonoma de Mexico, Mexico D.F. Mexico, 2 Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Mexico D.F. Mexico
Show AbstractThe transport of electrons in carbon nanotubes is studied by means of a real-space renormalization plus convolution method [1], in a similar way to the cubically structured nanowire case [2]. A honeycomb lattice of atoms can be mapped into a square one by considering that each new lattice point represents four atoms. The method of renormalization plus convolution has the advantage of being computationally efficient, without introducing additional approximations and capable to analyze nanotubes of multi-scale length even with defects. The results show a quantized electrical dc conductance for single-wall pure nanotubes. Effects of single and extended planar defects, such as a quasiperiodic modulation, on the electric conductance of nanotubes with a macroscopic length are also investigated. [1] V. Sanchez and C. Wang, Phys. Rev. B 70, 144207 (2004). [2] C. Wang, F. Salazar, and V. Sanchez, Nano Lett. 8, 4205 (2008).
9:00 PM - K18: PosPhysApp
K18.4 Transferred to K7.6
Show Abstract