Symposium Organizers
Kenji Hata AIST
Annick Loiseau Laboratoire d'Etude des Microstructures (LEM)
Yoke Khin Yap Michigan Technological University
Ming Zheng DuPont Central Research and Development
II1: Carbon Nanostructures I
Session Chairs
Kenji Hata
Annick Loiseau
Yoke Khin Yap
Ming Zheng
Monday PM, November 26, 2007
Room 312 (Hynes)
9:00 AM - **II1.1
``Super Growth": Applications and the Scaling up for Mass Production of Catalyst-Free SWNTs.
Don Futaba 1
1 Research Center for Advanced Carbon Materials, AIST, Japan, Tsukuba, Ibaraki, Japan
Show AbstractSingle-walled carbon nanotubes (SWNT), possessing unique intrinsic properties, have inspired numerous potential applications from high-performance computer chips to drug delivery devices, yet their ultimate place in history as a industrially viable material hinges on their availability. Previously we demonstrated the highly pure and highly efficient synthesis of single-walled carbon nanotubes (water-assisted or “Super-growth” chemical vapor deposition (CVD) [1]) which simultaneously addressed problems, such as scalability, purity and cost. This presentation will provide an overview of our recent progress in the synthesis and application of millimeter-scale, vertically-aligned single-walled carbon nanotubes using Super-growth CVD. After providing a brief introduction to the Super-Growth concept, I will discuss some recent results on the application of SWNT forests for epoxy reinforcement. Next, I will present the development of SWNTs with high surface area by utilizing their inner surfaces, and our technique to transform the sparse as-grown carbon nanotube forests into highly-densely packed material that we call SWNT solids [2]. We demonstrate that such SWNT solid and are useful for super-capacitor electrodes for compact energy storage. Finally, I will present our progress toward the realization of industrial-scale mass production of high-purity, long, and aligned SWNTs. [1] K. Hata, D.N. Futaba, K. Mizuno, T. Namai, M. Yumura, and S. Iijima, Science, 306, 1362 (2004). [2] D. N. Futaba et al., Nature Mater., 5, 987 (2006).
9:30 AM - II1.2
Growth of Single-Walled Carbon Nanotubes with Controlled Diameter from Individual Catalyst Nanoparticle.
Jin Zhang 1 , Yagang Yao 1 , Ran Liu 1 , Zhongfan Liu 1
1 College of Chemistry and Molecular Engineering, Peking University, Beijing China
Show AbstractThe first critical step in making full single-walled carbon nanotubes (SWNTs) electronic circuit is to make SWNT intramolecular junctions in a controlled manner. Unfortunately, although SWNT intramolecular junctions have been reported grown via several methods, they only grew inadvertently in most cases. We reported herein a temperature oscillated chemical vapor deposition (CVD) to grow ultralong (SWNTs) with different (n,m) value (or different diameter) displaying in single nanotubes. The diameter of the SWNTs will change from larger to smaller or inverse depending on the temperature oscillated direction. We found a given catalyst nanoparticle prefers to grow larger diameter nanotube under lower temperature and smaller diameter nanotube while in the higher temperature. The different (n,m) value or diameter of nanotubes displaying in a single nanotube can be detected by micro-resonance Raman spectroscopy and electric properties measurement. It is indicated that M-M, M-S, and S-S SWNTs intramolecular junctions can be obtained by the temperature oscillated CVD. Additionally, using the intramolecular junctions as Raman identifiable marks to confirm the starting and finishing position of the segments, the growth rate of SWNTs can be calculated by ν=L/t, where ν is the growth rate, L is the length of the segment which can be measured by Raman mapping and t is its growth time. This temperature oscillated CVD will benefit the development of nanotube-based devices for future applications, such as FETs, sensors, NEMS, etc. References:1, YG Yao, QW Li, J Zhang, R Liu, LY Jiao, YT Zhu, ZF Liu, Nature Materials, 2007, 6, 283-286.2, YG Yao, R Liu, J Zhang, LY Jiao, ZF Liu, J. Phys. Chem. C, 2007, In press.
9:45 AM - II1.3
Controlled Growth of Vertically Aligned Single- and Double-Walled Carbon Nanotubes without Etching Agents.
Vijaya Kayastha 1 , Shun Wu 1 , Jason Moscatello 1 , Yoke Khin Yap 1
1 , Michigan Technological University, Houghton, Michigan, United States
Show AbstractThe number of graphene shells on carbon nanotubes (CNTs) was controlled to yield high-density, vertically-aligned single-walled CNTs (SWCNTs) and double-walled CNTs (DWCNTs). This was obtained by a conventional thermal chemical vapor deposition technique at 700oC without using any etching agents such as water, oxygen or plasma which may potentially oxidize and damage the nanotubes. Acetylene was used as the carbon precursor. The growth rate was ≥16 µm/min for both SWCNTs and DWCNTs growths, which is higher than in most reported works. Our SWCNTs are ~100% pure while DWCNTs are ~ 80% pure. We found that the decomposition rate of acetylene must be controlled for achieving equilibrium with the rates of subsequent carbon diffusion into the catalysts and carbon segregation from the catalysts, as suggested by our growth model proposed earlier for multi-walled CNTs [1, 2]. The key factors for this success are controlled dissociative adsorption of acetylene (C2H2) molecules, and sub-nanometer thickness control of the Al/Fe/Mo tri-layer films. We propose that an Al concave meniscus confines the actual growth surface areas of Fe/Mo catalytic nanoparticles [3], while controlled supply of acetylene defines the number of shells in the nanotubes and, ultimately, enables the growth of CNTs with desired number of graphene shells.This work is supported by the U.S. Department of Army (Grant No. W911NF-04-1-0029, through the City College of New York), Defense Advanced Research Agency (Contract No: DAAD17-03-C-0115, through Army Research Laboratory), and the Center for Nanophase Materials Sciences sponsored by the Division of Materials Sciences and Engineering, U.S. Department of Energy (Contract No DE-AC05-00OR22725).[1]. V. Kayastha et. al, Appl. Phys. Lett. 85, 3265 (2004).[2]. V. Kayastha et. al, Appl. Phys. Lett. 86, 253105 (2005).[3]. V. Kayastha et. al, J. Phy. Chem. C (letter), (2007, in press).
10:00 AM - II1.4
Tuning of Vertically-Aligned Carbon Nanotube Length, Number of Walls, and Areal Density through Catalysts Pre-Treatments.
Gilbert Nessim 1 , A. John Hart 2 , Jin Kim 1 , Donatello Acquaviva 3 , Jihun Oh 1 , Cate Morgan 1 , M. Seita 1 , Carl Thompson 1
1 Department of Materials Science and Engineering, MIT, Cambridge, Massachusetts, United States, 2 Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 3 Laboratory of Micro and Nanoelectronics Devices (LEG2), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne Switzerland
Show Abstract10:15 AM - II1.5
Synthesis of Highly Quality Double-Walled Carbon Nanotubes.
Ye Hou 1 , Cheng Qian 1 , Jie Liu 1
1 Chemistry, Duke University, Durham, North Carolina, United States
Show AbstractHighly pure double-wall carbon nanotubes (DWNTs) (>95%) have been synthesized by carbon monoxide CVD method using binary catalysts Co/Mo supported on MgO. High-Resolution TEM and Raman spectroscopy have revealed that the present DWNTs have an inner diameter of 0.7-1.1nm, which correspond to the narrowest diameter distribution of mass produced DWNTs ever reported. Moreover, the diameters of DWNTs can be controlled by simply adjust growth temperature and tuning the catalyst compositions.
10:30 AM - **II1.6
Understanding and Controlling the Synthesis of Carbon Nanotubes and Nanohorns with Time-Resolved in situ Diagnostics.
David Geohegan 1 , Alexander Puretzky 1 , Gyula Eres 1 , Bin Zhao 1 , Hui Hu 1 , Christopher Rouleau 1 , David Styers-Barnett 1 , Zuqin Liu 1 , Ilia Ivanov 1 , Jeremy Jackson 1 , Richard Wood 1 , Sreekanth Pannala 1 , Jack Wells 1 , Mina Yoon 1 , Kai Xiao 1 , Matthew Garrett 1
1 Materials Science and Technology Division and Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show Abstract11:00 AM - II1: Carbon-1
BREAK
II2: Optical Spectroscopy I
Session Chairs
Kenji Hata
Jing Kong
Annick Loiseau
Yoke Khin Yap
Ming Zheng
Monday PM, November 26, 2007
Room 312 (Hynes)
11:30 AM - **II2.1
Raman Spectroscopy of Well-identified Single-walled Carbon Nanotubes.
Matthieu Paillet 1 , Thierry Michel 2 , Jean-Louis Sauvajol 3
1 Physics, Universite de Montreal, Montreal, Quebec, Canada, 2 Physics, Universite de Montpellier, Montpellier France, 3 Physics, University Montpellier II/CNRS, Montpellier France
Show AbstractFor long time, the resonance Raman spectra of isolated SWNTs were only measured on SWNTs grown (deposited) on a substrate and on SWNTs wrapped with surfactant and dispersed in aqueous solution. These spectra have been mainly understood in the framework of different models of the electronic and mechanical properties. The goal of our “complete experimental” approach is to relate the Raman response of an individual freestanding SWNT to its (n,m) structure determined from an independent way. In this aim, a procedure including transmission electronic microscopy (TEM), Raman spectroscopy, and electron diffraction experiments on the same freestanding nanotube was developed. The precise and independent determination of both structure and Raman features of semiconducting and metallic SWNTs allows to answer at several questions:1- From the radial breathing mode (RBM) frequencies measured on precisely identified nanotube structures, we obtain a RBM vs. diameter relationship that does not depend on any modelization of nanotube electronic or mechanical properties [1]. A comparison with recent data obtained on freestanding metallic SWNTs [2] is done.2- The dependence of the frequency of the tangential modes (LO and TO) with the diameter of semiconducting tubes is found and compared with the predictions of different models [3]. On the other hand the profiles of the LO and TO G-modes for metallic tubes are shown and discussed.3- The comparison between the incident excitation energies, for which an intense RBM signal is measured, and the calculated transition energies [4] allows us to determine precisely the values of the optical transition energies EM11, ES33 and ES44 for SWNTs for SWNTs in the 1.3-2.4 nm diameter range: the so-called "Kataura" plot [3]. A good agreement with the transition energies measured by Rayleigh scattering [5] is shown. Several exemples of the use of this "Kataura" plot in the understanding of Raman data and identification of the structure of tubes are reported.4-These latter results question the so-called Kane and Mele correction [Kane and Mele. Phys. Rev. Lett. 93, (2004), 197402] to explain the differences between the experimental and calculated transition energie for the ES33 and ES44 [6]. Different other explanations are discussed.[1] J.C. Meyer et al., Phys. Rev. Lett. . 95 (2005) 217401.[2] J. Maultzsch et al, arXiv/cond mat:0705.3986.[3] M. Paillet, et al.,, Phys. Rev. Lett. 96 (2006) 257401.[4] V. Popov and L. Henrard, Phys. Rev. B 70, (2004) 115407.[5] M. Y. Sfeir et al., Science 312 (2006) 554.[6] T. Michel, Phys. Rev. B 75 (2007)155432.
12:00 PM - II2.2
Raman Spectroscopy of Isolated Double Wall Carbon Nanotubes (DWNTs).
Federico Villalpando 2 , Daisuke Shimamoto 5 , Alfonso Reina Cecco 2 , Antonio G. Souza Filho 4 , Hyungbin Son 1 , Eduardo Barros 7 , Yoong A. Kim 5 , Morinobu Endo 5 , Mauricio Terrones 6 , Mildred Dresselhaus 1 3
2 Materials Science and Engineering, Massachusetts Institute of Technology, cambridge, Massachusetts, United States, 5 Faculty of Engineering, Shinshu University, Shinshu Japan, 4 Departamento de Fisica, Universiadade Federal do Ceara, Ceara, Fortaleza, Brazil, 1 Electrical Engineering and Computer Science, Massachusetts Institute of Technology, cambridge, Massachusetts, United States, 7 Physics, Tohoku University, Tohoku Japan, 6 Advanced Materials Department, IPICyT, San Luis Potosi, San Luis Potosi, Mexico, 3 Physics, Massachusetts Institute of Technology, cambridge, Massachusetts, United States
Show AbstractWe performed Raman spectroscopy experiments on isolated double walled carbon nanotubes (DWNTs). The inner and outer walls of a DWNT can be metallic (M) or semiconducting (S) and each of the four possible configurations (M/M, M/S, S/S, S/M) has different electronic properties. In this context, various laser excitation energies were used to identify the configuration of individual DWNTs and to study their electronic properties. We identify the contributions from the inner and outer layers of an isolated DWNT to the Raman G and G’ bands and compare the results to similar measurements made on DWNT bundles and single and double layer graphene.ACKNOWLEDGEMENTS.CONACYT-Mexico grant 45772 (MT). CONACYT-Mexico graduate student fellowship.NSF Grants DMR-04-05538 and DMR-07-04197.
12:15 PM - II2.3
Length Dependence in the Raman Spectra of Carbon Nanotubes.
Aurea Zare 1 , Shin Grace Chou 2 7 , Hyungbin Son 1 , Ming Zheng 5 , Jeff Simpson 6 , Angela Hight Walker 6 , Gene Dresselhaus 4 , Mildred Dresselhaus 3 1
1 EECS, MIT, Cambridge, Massachusetts, United States, 2 Chemistry, MIT, Cambridge, Massachusetts, United States, 7 Parenteral Center of Emphasis, Pfizer Global Research and Development, Groton, Connecticut, United States, 5 , DuPont Central Research and Development, Wilmington, Delaware, United States, 6 , National Institute of Standards and Technology, Gaithersburg, Maryland, United States, 4 Francis Bitter Magnet Laboratory, MIT, Cambridge, Massachusetts, United States, 3 Physics, MIT, Cambridge, Massachusetts, United States
Show AbstractLength sorting of DNA-wrapped carbon nanotubes using size-exclusion chromatography was recently achieved. This advancement allows a greater understanding of the basic properties of carbon nanotubes, since few length-dependent studies exist. Furthermore, the availability of short carbon nanotubes, having lengths less than the wavelength of visible light, allows us to study finite size effects. We present the results of Raman spectroscopy experiments on length-sorted carbon nanotube samples. Raman data was collected using a wide range of laser excitation energies that probe both semiconducting and metallic nanotubes. The length dependence of the individual G-band components was analyzed. For metallic nanotubes, the lower frequency G- peak has a broad, asymmetric Breit-Wigner-Fano lineshape, the origin of which remains unclear. We have found that this peak becomes narrower and the lineshape becomes less asymmetric as the nanotube length decreases. In addition, an unusually high intensity ratio of the G- peak to the higher frequency G+ peak was found to occur for the shortest metallic nanotubes. The length dependence of the Intermediate Frequency Mode (IFM) peaks, which were predicted to appear for finite length nanotubes, will also be discussed. This work was supported by the Dupont-MIT Alliance, NSF Grants DMR-04-05538, INT 00-00408, and DMR-07-04197, NIST, and the National Research Council – NIST Postdoctoral Fellowship.
12:30 PM - II2.4
Dependence of Raman-active Modes on the External Voltagein Single-wall Carbon Nanotube Networks.
Giovanni Fanchini 1 , Husnu Unalan 1 , Goki Eda 1 , Manish Chhowalla 1
1 Materials Science and Engineering, Rutgers University, Piscataway, New Jersey, United States
Show AbstractWe report on Raman measurements under the application of an external voltage in gap-cell devices made by transparent and conducting single-wall carbon nanotube (SWNT) thin films [1] Two different Raman excitation wavelengths (785 and 633 nm) were used. Application of voltage results in downshifts of the D and G modes and in reduction of their intensity. The intensities of the radial breathing modes increase with voltage in metallic SWNTs, while decreasing in semiconducting SWNTs. A model explaining the phenomenon in terms of both direct and indirect (Joule heating) effects of the field is proposed. Our work rules out the elimination of large amounts of metallic SWNTs in thin film transistors using high field pulses. Our results support the existence of Kohn anomalies in the Raman-active optical branches of metallic graphitic materials. Additional Raman measurements in SWNT thin film transistors at varying source-drain voltage and gate voltage will be presented as well.[1] G Fanchini, et al, Nano Lett. 7 (2007) 1129
12:45 PM - II2.5
Crystal Face Dependence of Chiralities of Horizontally-aligned SWNTs on Sapphire.
Naoki Ishigami 1 , Hiroki Ago 1 2 , Kenta Imamoto 1 , Masaharu Tsuji 1 2 , Konstantin Iakoubovskii 3 , Nobutsugu Minami 3
1 Graduate School of Engineering Sciences, Kyushu University, Fukuoka Japan, 2 Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka Japan, 3 Nanotechnology Research Institute, AIST, Tsukuba Japan
Show AbstractThe directional control of single-walled carbon nanotubes (SWNTs) on a substrate is one of the most important issues for fabrication of SWNT-based devices. In our previous work, we succeeded to grow horizontally-aligned SWNTs on A- and R-faces of sapphire substrates [1-3]. Influences of a crystal face on the structure of aligned SWNTs are interesting from the view point of epitaxial growth. Here, we report on the characterization of the aligned SWNTs by Raman and photoluminescence (PL) spectroscopies.SWNTs were grown on A-, R-, C-face sapphire and SiO2 substrates by chemical vapor deposition (CVD) in the presence of Co-based catalyst. The diameter distribution was estimated by a Raman spectroscopy with three different excitation wavelengths (488, 514.5, and 632.8 nm) and found to depend on the crystal face of sapphire. The surfaces which aligned SWNTs gave relatively narrow diameter distribution. We could observe the PL from the aligned SWNTs on sapphire, even though the SWNTs were not covered with any surfactants. The polarized PL measurement confirmed the alignment of nanotubes. This is the first demonstration of the PL emission from uncovered SWNTs deposited on a substrate, as far as we know, because tube-substrate interactions are supposed to quench the luminescence. The reaction temperature dependence of the chirality distribution was also studied by the PL measurement.[1] H. Ago et al., Chem. Phys. Lett., 408, 433 (2005).[2] H. Ago et al., Chem. Phys. Lett., 421, 399 (2006).[3] H. Ago et al., Appl. Phys. Lett., 90, 123112 (2007).
II3: Carbon Nanostructures II
Session Chairs
Shashi Karna
Ralph Scheicher
Yoke Khin Yap
Monday PM, November 26, 2007
Room 312 (Hynes)
2:30 PM - **II3.1
Excitons and Many-electron Effects in Nanotubes and Graphene Nanoribbons.
Steven Louie 1 2
1 Physics, University of California at Berkeley, Berkeley, California, United States, 2 Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractIn this talk, I discuss some recent work on using first-principles theory and computation to understand and predict the electronic structure and optical response of one-dimensional nanostructures, with focus on metallic single-walled carbon nanotubes (SWCNTs) and graphene nanoribbons. The calculations confirm earlier prediction that bound excitons exist in metallic SWCNTs [1] and that excitonic effects are very important in describing their optical properties. In particular, excitons exist in the experimentally realizable metallic tubes, with binding energies of ~50 meV. [2] Although these binding energies are smaller than those in the semiconducting tubes, the optical spectrum is qualitatively altered in character by the excitons leading to distinct characteristics that may be tested by experiment. Theory further shows that the second and third van Hove singularities in the joint density of states also give rise to a single “bright” bound or resonant exciton state. Similarly, we have carried out calculations on the quasiparticle excitations and optical spectra of the graphene nanoribbons as a function of their widths. Our results show that both armchair-edged graphene nanoribbons (AGNRs) and zigzag-edged graphene nanoribbons (ZGNRs) are semiconductors [3], arising from different physical mechanisms, and that many-electron effects are equally important in the spectroscopic properties of these systems as in the SWCNTs. Moreover, the ZGNRs are predicted to be half-metals under a sufficiently strong transverse electric field.[4]Acknowledgments: This work is supported by NSF and DOE.[1] C. D. Spataru, S. Ismail-Beigi, L. X. Benedict, and S. G. Louie, Phys. Rev. Lett. 92, 077402 (2004).[2] J. Deslippe, C. D. Spataru, D. Prendergast, and S. G. Louie, Nano Lett. (2007), in press.[3] Y.-W. Son, M. L. Cohen, and S. G. Louie, Phys. Rev. Lett. 97, 216803 (2006).[4] Y.-W. Son, M. L. Cohen, and S. G. Louie, Nature 444, 347 (2006).
3:00 PM - II3.2
Spin Channels in Functionalized Graphene Nanoribbons.
Giovanni Cantele 1 , Young-Su Lee 2 , Domenico Ninno 1 , Nicola Marzari 2
1 Scienze Fisiche, Coherentia CNR-INFM and Universita' di Napoli "Federico II", Napoli Italy, 2 Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractWe characterize with first-principles techniques the electronic structure and ballistic conductance of graphene nanoribbons after they have been functionalized with a variety of organic or inorganic moieties. Conducting edge states appear under a variety of applied chemical potentials and partial pressures. More importantly, the same functionalizations that create edge states can effectively passivate the bulk of the ribbon, giving rise to spin-resolved conduction channels that could act as near perfect spin-valves.
3:15 PM - II3.3
Electrostatic Response of the Graphene and Boron-nitride Sheets from First-principles Calculations.
Boris Kozinsky 1 , Nicola Marzari 1
1 , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractWe present a complete characterization of the electrostatic response of two-dimensional graphene and boron-nitride sheets using first-principles calculations. In particular, we focus on the $q$-dependence of the in-plane static charge density response function, which we calculate using density functional perturbation theory, fully accounting for all crystal-field effects. Graphene is an exceptional material with extremely high mobility of charge carriers, whose dispersion mimics that of massless relativistic particles. The unusual electronic structure of pristine graphene is responsible for the scale-invariant in-plane dielectric response, which we find to be qualitatively different from either a metal or an insulator. In order to highlight the unique dielectric properties of pristine graphene, we compare its response to that of boron-nitride, a two-dimensional material with a related crystal structure. We find that the response function of boron-nitride exhibits scaling expected of a 2D insulator, while doped graphene behaves like a metal. These results are relevant in studying charged impurities and engineering the electron-phonon coupling in these low-dimensional materials. We also map the computed in-plane response functions of these two-dimensional materials onto cylindrical geometry. This allows us to make predictions regarding the screening of uniform electric fields and the transverse dielectric response of carbon and boron-nitride nanotubes, that are in excellent quantitative agreement with direct ab-initio calculations of nanotubes. We find that the scale-invariant dielectric response of graphene is directly responsible for the semi-metallic character and radius-invariant screening in single-wall carbon nanotubes.
3:30 PM - II3: Carbon-2
BREAK
II4: Carbon Nanostructures III
Session Chairs
Kenji Hata
Annick Loiseau
Yoke Khin Yap
Ming Zheng
Monday PM, November 26, 2007
Room 312 (Hynes)
4:00 PM - **II4.1
Modelling the Nickel Carbon Interface to Study the Nucleation and Growth of Carbon Nanotubes.
Amara Hakim 2 , Christophe Bichara 1 , Francois Ducastelle 3
2 Laboratoire Francis Perrin, CNRS/CEA, Gif sur Yvette France, 1 Centre de Recherches en Matiere Condensee et Nanosciences, CNRS, Marseille France, 3 Laboratoire d Etude des Microstructures, CNRS/ONERA, Chatillon France
Show AbstractWe have developed a tight binding model for Ni-C alloys (1). A special effort has been made to reproduce some key features of the Ni-C interaction that are important for the study of the carbon nanotube nucleation and growth. The interaction energies of carbon with Ni in different configurations match the ab-initio and the available experimental data. Typical features of the behavior of C on a Ni surface such as the “clock” reconstruction are also obtained in our model, as well as a reasonable solubility of C in bulk Ni (about 8% at 1500K to be compared with the experimental value around 4%). Using grand canonical Monte Carlo calculations (2), we simulate the nucleation and early stages of the growth of carbon nanotubes, under conditions relevant to chemical vapor deposition synthesis. We first show that the nucleation of a nanotube cap is only possible in a well defined carbon chemical potential window, in agreement with experimental observations. We then study the combined effect of the temperature, carbon chemical potential, size and initial state of the catalyst particle (crystalline or amorphous, resulting from a quench from the liquid) on the carbon solubility in the outer catalyst layers. Depending on these conditions, carbon solubility can be either marginal or large enough to induce a significant, liquid-like, disorder of the outer layers, possibly explaining the “reshaping” of the catalyst particle observed experimentally.We conclude by an analysis of the catalytic growth mechanisms, in relation with the characteristics of the Ni-C bonding. Its consequences on the growth models and on a possible control of the chirality of the tubes are discussed.[1] H. Amara, C. Bichara and F. Ducastelle Phys. Rev B, 73, 113404, (2006).[2]submitted to the Journal of Nanoscience and Nanotechnology. Preprint available at http://fr.arxiv.org/abs/0704.2024.
4:30 PM - **II4.2
Interface Dynamics of Crystalline Catalysts during Carbon Nanotube Growth.
Stephan Hofmann 1
1 Engineering, Unversity of Cambridge, Cambridge United Kingdom
Show AbstractAn accurate model of catalytic carbon nanotube nucleation relies heavily on the quality of direct experimental observation. We present atomic-scale environmental transmission electron microscopy (ETEM) and in-situ X-ray photoelectron spectroscopy (XPS) of catalyst assisted growth of SWNTs and CNFs [1], combined with a large-throughput ex-situ catalyst screening by plasma assisted and thermal CVD [2,3]. We sample Ni, Fe, Au and Cu catalyst films on SiOx and Al2O3 support upon acetylene, ethylene or methane exposure. We focus on catalyst island formation upon temperature elevation and their subsequent interaction with carbon precursors and the resulting graphitic network. We compare this to graphene nucleation on stepped transition metal films.We observe Ni catalyst nano-particles to be highly deformable, despite their core exhibiting a crystalline structure throughout the CVD process. Time-resolved XPS results suggest a rapid transition from initial chemisorbed carbon on a metallic Fe catalyst surface to a sp2 graphitic carbon network. For a CNF, the graphene layer stacking is determined by the successive elongation and contraction of the catalyst nano-particle at its tip. A SWNT nucleates by lift-off of a carbon cap. Cap stabilization and nanotube growth involve the dynamic reshaping of the catalyst nano-crystal itself. XPS shows a strong interaction between Fe and Al2O3 layers, which prevents excessive Fe island sintering and homogenises their size distribution. We observe with an optical camera how this triggers the growth of vertically aligned, mm-long SWNT/CNF forests. Combining ETEM and substrate micro-structuring, we show that, apart from their catalyst anchorage, SWNTs are often not in direct contact with the substrate. This allows us to grow gas-flow aligned, mm-long lateral nanotube arrays.References:[1] Hofmann S., Sharma R., Ducati C., Du G., Mattevi C., Cepek C., Cantoro M., Pisana S., Parvez A., Ferrari A. C., Dunin-Borkowski R., Lizzit S., Petaccia L., Goldoni A., Robertson J., Nano Lett. 7, 602 (2007)[2] Cantoro et al., Nano Lett. 6, 1107 (2006)[3] Hofmann et al., Phys. Rev. Lett. 95, 036101 (2005)
5:00 PM - II4.3
In-situ Study of Fe Catalyst Nanoparticles used for Growth of Carbon Nanotubes.
Tyson Back 1 2 , Benji Maruyama 1 , Terry Murray 2 1 , Eunsung Shin 2 , John Jones 1 , Eric Stach 3 , Seung Min Kim 3
1 MLBC, AFRL, Wright-Patterson, Ohio, United States, 2 Materials Engineering, University of Dayton, Dayton, Ohio, United States, 3 Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana, United States
Show AbstractThe catalyst nanoparticle is critical to the yield, purity, type, diameter and perfection in the growth and nucleation of carbon nanotubes. A complete physical description of how carbon nanotubes nucleate and began to grow is as of yet undetermined. In order to elucidate this process CVD experiments in which catalyst nanoparticles were deposited on substrates by through thin film ablation (TTFA) as well as sputtering were conducted in-situ with X-ray photoelectron, Auger electron, and ultraviolet photoelectron spectroscopies. The goal of the experiments is to understand the chemical and electronic changes to the state of the catalyst as a function of exposure to growth gases and growth temperatures. Spectra taken during Langmuir exposures of methane, ethylene, and acetylene, all mixed with hydrogen are expected to reveal the chemical state of Fe nanoparticles as a function of time. The impact of the results on current models for carbon nanotube growth will be discussed.
5:15 PM - II4.4
Measuring the Catalyst Lifetime Favorable for SWCNTs Growth: Parametrical Studies.
Elena Pigos 1 , Oleg Kuznetsov 1 , Toshio Tokune 1 , Avetik Harutyunyan 1
1 , Honda Research Institute USA Inc., Columbus, Ohio, United States
Show AbstractThe period of catalyst activity favorable for the growth of single-walled carbon nanotubes (SWCNTs) is a key catalyst property, especially when growing long and high quality tubes for particular applications. Currently, the approaches described in the literature for estimation of the catalyst lifetime are based on measurements of nanotubes length evolution with time. Here, a simple method is presented which allows us to precisely determine the catalyst lifetime favorable for the growth of SWCNTs. A special chemical vapor deposition set-up, enhanced by an attached mass spectrometer for in-situ parametrical studies, allows us to follow the catalyst activity evolution during the growth of SWCNTs. Validation of the period of catalytic activity and its relationship with nanotube growth is achieved by analysis of the Raman spectra of samples obtained with sequential introduction of hydrocarbon gases with 12C and 13C isotopes at different stages of the catalyst activity during nanotube growth. When contribution from both C isotopes is observed in the Raman spectrum, catalyst is still active for nanotube growth after switching gases [1]. When contribution from the carbon isotope introduced last is not observed, catalyst is already deactivated. The effect of synthesis parameters and catalyst precursor and composition on the catalyst lifetime for SWCNTs growth is also discussed. We find that proper modification of the catalyst composition (e.g. Fe/Mo instead of Fe) increases the lifetime around three times, thereby increasing the yield of tubes grown. An increase of 140 °C in the synthesis temperature shortened the lifetime from ~90 to ~10 min, increasing, however, the growth rate and resulting in a similar nanotube yield. A nine times increase in the CH4 feedstock only slightly decreased the catalyst lifetime, although affects on the sample quality as observed by Raman scattering and TGA analyses. Different poisoning mechanisms of catalysts are discussed.[1] A.R. Harutyunyan et. al. Appl. Phys. Lett. 90, 163120 (2007).
5:30 PM - II4.5
Determining the Effect of Catalyst Composition on Carbon Nanotube Growth Utilizing Composition Gradients.
Jonathan Petrie 1 , Benjamin Hertzberg 1 , Robert van Dover 1
1 MS&E, Cornell University, Ithaca, New York, United States
Show AbstractThe unique electrical, mechanical, and chemical properties of carbon nanotubes (CNTs) have not resulted in the technological impact originally anticipated due to difficulty in obtaining controlled growth. One aspect of this problem is the need to reliably synthesize nanotubes of certain chirality and length using thermal CVD. Choice of an optimum catalyst composition could prove advantageous, but the role of composition on nanotube growth has not been fully explored. We varied both the substrate and composition/structure of catalytic nanoparticles to determine what effects these variables may have on nanotube development under an ethylene precursor gas and a temperature range centered around 700°C. We employed a high-throughput (combinatorial) approach, which involved sputtering continuous composition gradients of different materials to prepare hundreds of intermetallic nanoparticle compositions on Si and SiO2 substrates. To date, we have focused on mixtures of Fe, Ni, and Co with other transition metals, such as Pd, Pt, and Ru. CNT growth was characterized using SEM and Raman/optical spectroscopy. We find systematic trends relating CNT structure to various nanoparticle composition/substrate combinations. By understanding these trends along with optimizing the processing conditions, we hope to identify materials that offer improved control over the crystallinity, chirality, and length of CNTs.
5:45 PM - II4: Carbon-3
II4.6 transferred to II22.4
Show AbstractII5: Poster Session: Synthesis of Nanostructures
Session Chairs
Kenji Hata
Annick Loiseau
Yoke Khin Yap
Ming Zheng
Tuesday AM, November 27, 2007
Exhibition Hall D (Hynes)
9:00 PM - II5.1
Linear Carbon Chains Obtanied by Laser Ablation of Carbon Targets in Different Liquids.
Giuseppe Compagnini 1 , Luisa D'Urso 1 , Valentina Mita 1 , Orazio Puglisi 1 , Sergio Cataliotti 1
1 Chemistry Dpt, university of catania, catania Italy
Show Abstract9:00 PM - II5.10
Investigation of Catalyst Reduction and Etching of Carbon Nanotubes Caused by Hydrogen During Carbon Nanotube Growth in CH4/H2 Plasmas.
Atsushi Okita 1 , Yoshiyuki Suda 1 , Akinori Oda 2 , Junji Nakamura 3 , Youhei Hizume 1 , Hirotake Sugawara 1 , Yosuke Sakai 1
1 Laboratory of Integrated Material Processings, Graduate School of Information Science and Technology, Hokkaido University, Sapporo, Hokkaido, Japan, 2 , Nagoya Institute of Technology, Nagoya Japan, 3 , University of Tukuba, Tukuba Japan
Show AbstractPlasma-enhanced chemical vapor deposition (PECVD) is one of the advantageous techniques for carbon nanotubes (CNTs) growth because it can synthesize CNTs at lower temperature (<400οC), which is desired to realize LSI applications of CNTs. We believe that it is crucial to investigate and reveal the mechanism of CNTs by PECVD and the effects of active species on CNTs growth for realizing CNT applications. In this study, we synthesized CNTs by CH4/H2 plasmas and these plasmas were simulated using a one-dimensional fluid model. We expect that quantitative evaluation of the precursor for CNTs will enable us to control CNTs growth with high accuracy. The detail of experimental setup and procedure are written in our previous works [1-3]. We used triple-layered catalysts (Al2O3/Fe/Al2O3 = 1/1/1 nm) for CNT growth under the CH4/H2 pressure of 10 Torr at 650οC and varied CH4/H2 gas mixture ratio. We evaluated CNTs grown by scanning electron microscope (SEM; Hitach S-4800) and transmission electron microscope (TEM; JEOL JEM-2000FX). We also analyzed the binding energy of carbon in CNTs using an X-ray photoelectron spectroscope (XPS; Shimadzu, ESCA-3400, MgKa 1253.6 eV). The amount of fluxes and number densities of plasma species were calculated by a plasma simulation [1,3]. From these results, we discussed the effects of hydrogen as a reductant and a etchant for CNT growth. First, we investigated the dependence of CNT growth on CH4/H2 gas flow ratio [1]. At CH4/H2 = 30/0 sccm, CNT growth rate was fast (0.8 μm/min) but CNT growth was saturated for 30 min. At CH4/H2 = 27/3 sccm, CNT growth rate was decreased (0.3 μm/min), while CNTs continued to grow for 90 min without losing catalyst activity. These results show that an addition of H2 in CH4 dramatically affects CNTs growth. Possible explanation is that a supply of hydrogen of an optimal amount realizes a longer duration time of CNTs by keeping the catalyst size small and active. However, excess supply of hydrogen makes the duration time short.Next, we studied the effect of hydrogen etching on CNTs by observing CNTs treated by H2 plasma after CNT growth. As the results, it was confirmed that multi-walled CNTs were not etched by the H2 plasma and the C 1s XPS spectra of the CNTs showed no chemical shift before and after the H2 treatment. In these XPS spectra, we found that C-H bonds were produced in CNTs. We think that the C-H bonds observed in CNTs were produced during CNTs growth owing to ion bombardments in plasma process. [1] A. Okita, et al, Carbon 45 (2007) 1518-1526. [2] A. Okita, et al, Jpn. J. Appl. Phys. 45 (2006) 8323-8329 [3] A. Okita, et al, J. Appl. Phys. 99 (2006) 014302.
9:00 PM - II5.11
Growth and Applications for Aligned Carbon Nanotubes on Metal Substrates.
Prahalad Parthangal 2 , Richard Cavicchi 1 , Douglass Meier 1 , Rebecca Zangmeister 1 , Michael Zachariah 2 1
2 Center for NanoEnergetics Research (CNER), University of Maryland, College Park, Maryland, United States, 1 Chemical Science and Technology Laboratory, National Institute of Standards & Technology, Gaithersburg, Maryland, United States
Show AbstractThe growth of aligned carbon nanotubes on both metal films and bulk metal substrates is desirable for a variety of applications. Chemical vapor deposition (CVD) of CNT’s makes use of a dispersion of metal catalytic nanoparticles such as Fe, Ni, or Co. At the high growth temperatures needed for CNT growth, reaction between the nanoparticles and the metal substrate is likely, which has impeded progress towards a general approach. Recent reports of the utility of two-component catalyst particles for the growth of CNT’s suggest a way around this problem. We have found that iron/alumina composite catalysts can be used to successfully grow aligned CNT’s on metals. The alumina both minimizes the surface diffusion of iron and prevents catalyst substrate reactions. Using a CVD process with acetylene, hydrogen and argon at moderate temperatures, (as low as 550 °C) we have grown aligned multiwall CNTs on Au, Ag, Cu, Al, Pt, W, TiN, NiCr, and steel substrates. Despite the presence of non-conducting alumina from the catalyst, the contact resistance between the CNTs and the metal underlayer was observed to be low, which is important for many practical applications.We report the use of this process for two applications. In the first, we fabricated area electrochemical electrodes consisting of aligned nanotubes grown directly on thin film gold electrodes. Cyclic voltammetry (CV) was employed to study the electroactivity of these CNT forests to both cationic [Ru(NH3)63+/2+] and anionic [Fe(CN)63-/4-] redox couples and compared against bare Au films. The nanotube electrode produced reproducible signals that did not degrade after repeated cycles. In the second, we examined the use of CNTs as a template for the CVD growth of tin oxide for gas sensing applications. The substrate used was a microhotplate, a micromachined membrane with a buried heater and top electrical contacts. A microhotplate, coated with catalyst, was placed in a cold-wall CVD reactor. While the CVD gases flowed over the sample, a voltage was applied to the microheater to heat the surface of the microhotplate to 600 °C. This allowed for the selective deposition of CNTs only on the heated microhotplate surface. After characterization of this layer, the sample was placed in a second cold wall CVD chamber, where the microhotplate was heated to 375 °C in the presence of tin nitrate. This resulted in tin oxide-coated CNTs. Subsequent heating to 450 °C in air removed the CNTs leaving tin oxide nanotubes. The device showed substantial improvement in sensitivity to methanol compared to a tin oxide film grown directly on the microhotplate.
9:00 PM - II5.12
Multi-walled Carbon Nanotubes from a Coal Precursor by Chemical Vapor Deposition Method: Synthesis and Purification.
Hong Zhu 1 , Lu Zhang 1 , Haiyan Lin 1 , Xudong Cao 1
1 , Beijing Jiaotong University, China, Beijing China
Show Abstract9:00 PM - II5.13
Aligned Multi-Wall Carbon Nanotube Growth on Conductive Substrates.
Justin Bult 1 , Pamela Dickrell 2 , Linda Schadler 1 , Pulickel Ajayan 1 , Gregory Sawyer 2
1 Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States, 2 Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida, United States
Show AbstractThe use of carbon nanotubes in electronic applications requires low resistance electrical contact with the nanotubes while still allowing for controlled growth and placement. To this end it will be shown that the use of metal substrates such as Inconel or stainless steel, with stable passivation oxide barriers, in Thermal Chemical Vapor Deposition allows for growth of aligned multi-wall carbon nanotubes with high conductivity. Furthermore, by altering the passivation oxide, the electrical conductivity and nanotube placement is controllable based on the oxide’s impurities, thickness and oxidation procedure. Designed patterns of aligned nanotubes can also be produced by using selective oxidization (or etching) when producing the passivation barrier. This technique allows for conductive assemblies of directionally controlled nanotubes to be grown. Finally, the nanotube arrays will be demonstrated in device applications such as electrical contacts and field emitters. The decreased interfacial resistance coupled with the conductive substrate allows for enhanced device performance and ease of production.
9:00 PM - II5.14
Carbon Nanotubes Directly Grown on Atomic Force Microscopy Tips.
Hiroki Okuyama 1 , Nobuyuki Iwata 1 , Hiroshi Yamamoto 1
1 College of Science and Technology, Nihon University, Funabashi, Chiba, Japan
Show AbstractCarbon nanotubes (CNTs) have many unique characteristics, for example, high mechanical strength, high electric conductivity, and small radius of curvature. These characteristics are promising for application to a nano probe tip such as an atomic force microscopy (AFM) probe. We have developed a novel process to prepare CNT probes using growth position and direction controlling method of CNTs. In this report, we attempted to grow only one CNT directly on the top of the AFM cantilever tip. An Au cover layer and a Ni catalyst were deposited on a Si3N4 AFM cantilever. The Au/Ni films were prepared using RF magnetron sputtering. The growth conditions (substrate temperature, sputtering power and growth time) were 70°C, 20 W and 10 min for Ni, 120°C, 50 W and 10 min for Au, respectively. The cantilever tip was scratched on a sapphire substrate using AFM to remove the Au cover layer. The CNTs were grown using DC plasma-enhanced chemical vapor deposition (PECVD) method. The CVD reactor tube was heated to 500°C. The background pressure was 0.1 Pa. The H2 : Ar (50 : 50 sccm) flow was introduced into the reactor tube during heating. The total pressure was maintained at 2 kPa. The DC glow discharge was induced by applying a bias voltage of -250 V between a sample holder and a grounded anodes separated from the substrates by approximately 5 mm. The CNT growth was performed by adding 5 sccm of ethylene (C2H4) gas. From the results of SEM observations, the cantilever tip was gradually ablated after AFM scratching. The Ni catalyst appeared at the top of the cantilever tip. As a result, only one CNT with ca. 20 nm diameter and ca. 700 nm length grew on the top of the cantilever tip. The CNT grew vertically due to the DC bias effect. Conclusively the CNT probes were fabricated using novel position selective growth and vertical alignment techniques of CNTs. The results of AFM/current imaging, which was observed using the fabricated CNT cantilever, will be reported.
9:00 PM - II5.15
Growth Promotion and Etching of Carbon Nanotubes by Carbon Dioxide in Chemical Vapor Deposition using Methane Gas.
Yoshiyuki Suda 1 , Takeshi Saito 1 , Atsushi Okita 1 , Junichi Takayama 1 , Junji Nakamura 2 , Yosuke Sakai 1 , Hirotake Sugawara 1
1 , Hokkaido University, Sapporo Japan, 2 , University of Tsukuba, Tsukuba Japan
Show Abstract9:00 PM - II5.16
Investigation of In-situ Growth of Carbon Nanotubes via Chemical Vapor Deposition for Field-Effect Transistor (CNTFET) Applications.
Eko Pandowo 1 , Dennis Callahan, Jr. 1 , Jonathan Leong 1 , Katherine Ziemer 2 , Albert Sacco, Jr. 1
1 Department of Chemical Engineering, Center for Advanced Microgravity Materials Processing, Northeastern University, Boston, Massachusetts, United States, 2 Department of Chemical Engineering, Semiconductor Interface Engineering Laboratory, Northeastern University, Boston, Massachusetts, United States
Show AbstractGlobal sales of semiconductors reached $247.7 billion in 2006, an increase of 8.9 percent from the $227.5 billion reported in 2005 [1]. Due to the increasing consumer demand for smaller computers that process data at a much faster rate, processors that have a large number of transistors per chip are required. For example, Intel Itanium® 2 uses as many as 1.7 billion transistors operating at 1.6 GHz [2]. However, further miniaturization is restricted by poor thermal conductivity of silicon. Carbon nanotubes have nanoscale dimensions (1-2 nm for single-walled; 10-20 nm for multiwalled) and are a promising candidate for creating smaller transistors. Carbon nanotube field-effect transistors (CNTFETs), introduced by IBM in 1998, were made by dispersing carbon nanotubes by sonication in a dichloroethane solution, and then spreading them on a substrate with predefined electrodes [3]. While this technique demonstrated the feasibility of CNTFETs, the processing method limited the number of transistors per chip. Therefore, a novel processing technique is needed to efficiently and effectively produce commercial CNTFETs.Controlled parallel growth of CNTFETs in-situ is a way to solve the processing difficulties to make many CNTFETs A process is being developed that combines nanoscale patterning by e-beam lithography with the controlled growth of CNTs demonstrated by Bazzana [4]. This process will control the placement of Ni nanoparticles using e-beam lithography to modify surface free energy, and control the growth sites and directionality of CNTs. First, troughs (1 μm × 50 nm × 25 nm each, 110 μm spacing between 2 troughs) were made by e-beam lithography on the Si substrate with 100 nm thick SiO2 on top. A gold electrode (100 μm × 100 μm × 50 nm) was patterned at both ends of each trough. Ni nanoparticles were deposited to make sites for CNTs in troughs between electrodes. Initial results show the ability to fabricate many CNTFETs at once, with controlled directionality of carbon nanotubes.
9:00 PM - II5.17
Growth of Well-aligned Thin Carbon Nanotubes at Low Temperatures by Inductively Coupled Plasma Chemical Vapor Deposition and their Field Emission Characteristics.
Kim Young Rae 1 , Jang Ingoo 2 , Jeon Hong Jun 1 , Kong Byung Yun 3 , Hwang Hosoo 3 , Cho Jungkeun 3 , Lee Naesung 1
1 Faculty of Nanotechnology and Advanced Materials Engineering, Sejong University, Seoul, 143-747, Korea (the Republic of), 2 Electronics Engineering, Sejong University, Seoul, 143-747, Korea (the Republic of), 3 Research Center, System Engineering Mega Solution, Yong-In, 446-901, Korea (the Republic of)
Show AbstractCarbon nanotubes (CNTs) have attracted much attention as one of the representative nanomaterials due to their versatile potentials to a wide range of applications. In particular, CNTs have been considered very promising for field emitter materials as they exhibit peculiar morphologies of extremely large aspect ratios (nm-scale diameter and μm long) and extraordinary properties in terms of electrical conductivity, mechanical strength, chemical inertness, etc. The application of CNTs to large-area field emitters puts several stringent prerequisites such as, most importantly, the growth of CNTs at temperatures low enough to adopt glass substrates. In the early-stage studies, CNTs had seldom been grown at low temperatures and finally Meyyappan et al. claimed that the growth of CNTs did not take place below 550°C. This study report here the successful synthesis of well-aligned multiwalled CNTs by using inductively coupled plasma chemical deposition (ICP-CVD) below 450°C. ICP-CVD, which belongs to high-density plasma , seems to efficiently decompose feedstock gases, thereby enabling the growth of CNTs at low temperatures. Our catalyst system is composed of three layers all deposited consecutively by thermal evaporation: 1-nm-thick ternary Fe-Ni-Co alloy catalyst, 15-nm-thick Al underlayer, and 50-nm-thick Ti diffusion barrier on a Si wafer. The catalyst substrate was annealed for 2 min in H2 (150 sccm) at 441°C and was then fed with a feedstock of C2H2 and a carrier gas of H2 for 5~10 min. We have systematically carried out the parametric study such as flow rate of C2H2, pressure, plasma power, etc. to optimize the synthesis of CNTs at low temperatures. Currently, we obtain several μm long, thin in diameter, vertically well aligned CNTs at the optimum deposition conditions. Our thin CNTs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and field emission measurements.
9:00 PM - II5.18
Controlling the Direction of Carbon Nanofiber Growth in a PECVD Process.
Anatoli Melechko 1 2 , Igor Merkulov 1 , Dale Hensley 2 , Ryan Pearce 2 , Michael Simpson 1 2 3
1 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 2 Center for Nanophase Materials Sciences, Oak Ridge National Lab, Oak Ridge, Tennessee, United States, 3 Materials Science and Engineering, University of Tennessee, Knoxville, Knoxville, Tennessee, United States
Show AbstractOne of the most significant benefits of using catalytic plasma enhanced chemical vapor deposition (C-PECVD) for growth of carbon nanofibers is that this process imposes alignment even on freestanding nanofibers. It has been demonstrated that the nanofibers with catalytic particles at the tip are aligned with the direction of electric field applied to the substrate during PECVD process. Usually, the electric field is perpendicular to the metallic substrate. It can be varied to some extent by controlling the geometry of the substrate. One of the models of the alignment mechanisms suggested that the mechanical forces that act on nanofiber-catalyst particle system are responsible for the controlling the growth direction. In this work we show that nanofiber growth direction can be significantly deviated from the direction of the electric field by appropriate modification of the gas distribution system. This result leads to the conclusion that growth direction depends on the spatial distribution of chemical potential across the nanoparticle surface. In this view the electric field is only one of many other factors, e.g. gas flux and pressure, which controls this distribution through a directed ion bombardment.This work was sponsored by the Division of Materials Sciences and Engineering of the DOE Office of Science (MLS, AVM, and IAM). This work was performed at Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the US DOE under Contract No. DE-AC05-00OR22725. A portion of this research was conducted at the Center for Nanophase Materials Sciences, which is sponsored at Oak Ridge National Laboratory by the Division of Scientific User Facilities, US Department of Energy.
9:00 PM - II5.19
Carbon Nanotube Growth on Different Types of Tool Steel Substrates.
Ipek Nasuf 1 , Max Yen 1
1 Mechanical Engr. Dept. SIUC, Materials Technology Center, Carbondale, Illinois, United States
Show AbstractMethods for achieving carbon nanotube growth directly on stainless steel substrates have been proposed. Proposed methods include either pretreatment of the surface using hydrogen plasma or using different form of steel substrates. In this study, carbon nanotube growth by thermal chemical vapor deposition on four different type of tool steel substrates will be investigated after pretreating the substrates by mechanical polishing, chemical etching and hydrogen gas. Relationship between the surface roughness and carbon nanotube growth will be studied as well as the effect of steel type on the growth of nanotubes. Surface treatment methods and thermal chemical vapor deposition process parameters that provide the most dense carbon nanotube growth on tool steel substrates will be obtained.
9:00 PM - II5.2
Two-Stage Growth of Single-Walled Carbon Nanotubes.
Hang Qi 1 , Dongning Yuan 1 , Jie Liu 1
1 Chemistry, Duke University, Durham, North Carolina, United States
Show AbstractThe growth of single walled carbon nanotubes (SWNTs) in a chemical vapor deposition (CVD) system is a complex process. In a typical growth mechanism, the process includes the nucleation, the growth and the termination stages. However, most of the growth experiments were performed under the same growth conditions for different stages. Here, a two-stage growth process is studied with different growth environment at the nucleation and growth stages. In the nucleation stage, the catalyst particles absorb carbonaceous species and get ready to catalyze the growth of SWNTs. And then in the growth stage, SWNTs grow from these catalyst particles. The requirements for optimized conditions for these two stages are different. To obtain SWNTs with desired high yield, different growth conditions are required to match the requirements of each stage. The experimental results confirmed that the yield of the carbon nanotubes can be significantly improved using higher carbon feeding rate in the nucleation stage followed by lower carbon feeding rate for continued growth.
9:00 PM - II5.20
Growth of Carbon Nanotubes by Remote Plasma-Enhanced Chemical Vapor Deposition for Interconnect Applications.
Masayuki Katagiri 1 , Naoshi Sakuma 1 , Mariko Suzuki 1 , Tadashi Sakai 1 , Shintaro Sato 2 , Takashi Hyakushima 2 , Mizuhisa Nihei 2 , Yuji Awano 2
1 , MIRAI-Selete (Semiconductor Leading Edge Technologies, Inc.), Kawasaki, Kanagawa, Japan, 2 , MIRAI-Selete (Semiconductor Leading Edge Technologies, Inc.), Atsugi, Kanagawa, Japan
Show AbstractCarbon nanotubes (CNTs) are an attractive material for future LSI interconnects because of their excellent properties such as high current capability, high thermal conductivity, ballistic transport along the tube, and high aspect ratio. It is necessary to lower the growth temperature of CNTs below 400 °C for the integration with low-dielectric-constant films in LSI. Plasma-enhanced chemical vapor deposition (CVD) is a suitable method to lower growth temperature of CNTs because source gases can be decomposed even at low temperatures owing to plasma. In this paper, we report on the low-temperature growth of CNTs by plasma-enhanced CVD and the formation of a planarized CNT via structure using conventional semiconductor processes.The growth of CNTs is performed by remote-type plasma-enhanced CVD. A quartz ion trap and a metal mesh grid were installed between the plasma and the substrate stage for suppression of ion bombardment damage. We have confirmed the effects on the reduction of ion density near the substrate by a Langmuir probe. A mixture of methane and hydrogen was used as the source gas. Size-classified Co nanoparticles were used as a catalyst.Scanning electron microscope and transmission electron microscope observations revealed that CNTs grown at a low temperature of 400 °C have a multi-walled structure. The diameter of the CNT was approximately 10 nm. In the via formation, CNT bundles were selectively grown in via holes at 430 °C. Planarization of the CNT vias was achieved by chemical mechanical polishing. The resistance of a 2-μm-diameter CNT via was 72 Ω. The higher resistance obtained in the present study may be attributed to ion bombardment damage from plasma to CNTs. In order to lower the electrical resistance of a CNT via, it is important to grow high-quality dense CNTs. The via resistance is in inverse proportion to the via area. In addition, the one-via resistance estimated from the measurements for 1000 via chains is approximately equivalent to that of a single CNT via. These results indicate that the CNTs are grown with uniform quality and density in via holes with various diameters and good electrical contacts between CNTs and the electrodes are obtained.This work was performed as part of the MIRAI Project supported by the NEDO of Japan.
9:00 PM - II5.21
Carbon Nanotube Growth on PLD and NSL Catalyst Films.
Niall Mc Evoy 1 , Tony Donnelly 1 , Rory Leahy 1 , Satheesh Krishnamurthy 1 , James Lunney 1 , Werner Blau 1
1 School of Physics, Trinity College Dublin, Dublin Ireland
Show AbstractThermal CVD using a mixture of C2H2 and Ar gases is used to grow carbon nanotubes on metal catalyst films prepared by pulsed laser deposition (PLD) and nanosphere lithography (NSL). These techniques allow for unordered and ordered placement of metal catalyst nanoparticles respectively. The films are characterized pre and post growth using AFM, SEM and Raman spectroscopy. This allows a comparison to be drawn between the nanotubes produced on each catalyst film. The effect of varying CVD process parameters such as active gas flow rates, active gas flow time and growth temperature is investigated. The effect of varying nanoparticle size and distribution is also investigated. For PLD this is achieved by changing the equivalent thickness of the deposited material. For NSL this is achieved by using either different metal deposition conditions or by using different sized nanospheres for templating against.CVD recipes for producing aligned arrays of nanotubes, interconnecting nanotubes and random networks of nanotubes have been developed. The use of these networks for the production of transistors and other macroscale electronic devices is investigated. Individual interconnecting nanotubes are interesting for use as quantum wires; aligned arrays are potentially applicable for the production of field emission devices and random networks are interesting for their use as an electronic material and for their use in sensor applications.
9:00 PM - II5.23
Microwave Synthesis of Carbon Nanotubes – The Concept of Selective Heating of Metallic Nanoparticles by Microwave Irradiation.
Stephanie Hoeppener 1 , Tamara Druzhinina 1 , Ulrich Schubert 1 2
1 Laboratory of Macromolecular Chemistry and Nanoscience, Eindhoven University of Technology, Eindhoven Netherlands, 2 Laboratory of Organic and Macromolecular Chemistry, Friedrich-Schiller-University Jena, Jena Germany
Show AbstractThe synthesis of carbon nanotubes generally requires the application of rather harsh experimental conditions, i.e. high temperatures, explosive feeding gas mixtures etc. This requirement significantly limits the growth of carbon nanotubes on substrates i.e. polymers etc. Recently, microwave heating became an important method in synthetic chemistry due to its direct heating properties. Naturally not all materials are equally suited for absorbing microwaves. This property of microwave heating is used for the synthesis of carbon nanotubes[1] on different substrates, including silicon, glass, teflon and polymeric substrates. The growth of carbon nanotubes requires the presence of catalyst particles, which are very efficient microwave absorbers. Therefore it can be demonstrated that the temperature in the vicinity of the catalyst particles is sufficiently high. Besides theoretical considerations we introduce a method that allows investigating individual particles, selectively attached to a substrate that is coated with a n-octadecyltrichlorosilane (OTS) monolayers. The analysis of individual catalyst particles is realized by the use of electro-oxidative nanolithography that allows binding of individual catalyst particles onto predefined positions on a substrate. The OTS monolayer acts as a sensitive indicator for elevated temperatures as it starts to degrade at temperatures above 150o C. It can be demonstrated that the degradation process starts only in close vicinity of the metal catalyst particles and indicates their selective heating due to microwave irradiation, whereas the remaining substrates remains significantly cooler. We explore the resulting possibilities to grow carbon nanotubes in a safe and fast approach (less than 5 minutes), utilizing microwave irradiation. This approach opens new possibilities to grow carbon nanotubes on a variety of substrates that are normally do not withstand high temperatures and opens new ways to integrate carbon nanotubes into device features. Finally, we explore possibilities for the formation of patterned nanotube arrays.[1] E.H. Hong, K.-H. Lee, S.H. Oh, C.G. Par, Adv. Funct. Mater. 2003, 13, 961.
9:00 PM - II5.24
Continuous-flow Microplasma Synthesis of Metal Nanoparticles for Catalytic Growth of Carbon Nanotubes.
Wei-Hung Chiang 1 , R. Mohan Sankaran 1
1 Chemical Engineering, Case Western Reserve University, Cleveland, Ohio, United States
Show AbstractCarbon nanotubes (CNTs) have been synthesized in a continuous-flow, gas-phase catalytic process. The synthesis technique consists of two steps: 1) production of well-defined metal nanoparticles in an atmospheric-pressure microplasma and 2) catalytic growth of carbon nanotubes in a tube furnace reactor. In the first step, nanoparticles are generated using a direct-current (dc) hollow cathode microplasma made-up of a stainless steel cathode with a pin-hole (d~180 μm) and an arbitrarily-shaped tube anode. Gaseous precursors are introduced into the microplasma at atmospheric-pressure and decomposed non-thermally by electron impact to generate reactive radical species. Under appropriate precursor saturation conditions, the radicals polymerize to nucleate particles homogenously in the gas phase. Particle growth is limited to the small reactor volume (less than 1 nL) created by the microplasma geometry. As a result of the large concentration gradients and short residence time, the technique is capable of producing very small (1-3 nm diameter) nanoparticles with narrow size distributions. The particle-laden flow is then continuously fed to a second reactor to grow carbon nanotubes in free flight with addition of acetylene and hydrogen and heating at fixed temperatures between 500 and 1000 oC. Nanotube size and distribution are determined on line using a gas-phase electrophoretic mobility macromolecular analyzer (GEMMA). In situ aerosol classification allows experimental conditions to be directly related to growth parameters. We have recently investigated the catalytic properties of iron and nickel nanoparticles toward growth of carbon nanotubes and determined their activation energies. Process parameters were optimized to prevent amorphous carbon formation and obtain high-quality CNTs. Ex-situ techniques such as Raman spectroscopy and high resolution transmission electron microscope (HRTEM) were used to characterize the structure of the carbon nanotubes. The combination of continuous-flow synthesis using microplasmas and the GEMMA system opens new possibilities for nanocatalyst synthesis and provides a methodology for enhancing our fundamental understanding of catalytic behavior.
9:00 PM - II5.26
Surface Oxidation and Carbon Nanotube Formation in Surface Decomposition of 6H-SiC.
Takahiro Maruyama 1 2 , Naomi Fujita 1 , Shigeya Naritsuka 1 2 , Michiko Kusunoki 3
1 Department of Materials Science and Engineering, Meijo University, Nagoya, Aichi, Japan, 2 21th CENTURY COE Nano Factory, Meijo University, Nagoya, Aichi, Japan, 3 EcoTopia Science Institute, Nagoya University, Nagoya, Aichi, Japan
Show AbstractIt has been reported that carbon nanotubes (CNTs) were formed through the decomposition of SiC(000-1) surfaces by heating in a vacuum. By this growth technique, well aligned zigzag-type CNTs can be selectively formed without any catalysts and the diameters of the CNTs are fairly uniform. Moreover, this growth technique has an advantage in fabrication of CNT devices, since CNTs grow into the inside of SiC, facilitating the application of semiconductor process. So far, we have reported that ambient oxygen enhances the CNT growth rate [1]. However, the optimum oxygen pressure has never been investigated enough. It has also been reported that SiO2 layer is formed on SiC surface after annealing under high oxygen pressure [2]. In this study, we investigated the relation between surface oxide formation and CNT growth under various annealing conditions.After HF etching, 6H-SiC(000-1) (Carbon-face) samples were introduced into an ultra-high vacuum (UHV) chamber and annealed at various temperatures between 800 and 1250oC. During the annealing, oxygen partial pressure was controlled by supply of oxygen gas. The oxygen pressure was set between 10-4 and 1 Pa. For comparison, we also annealed several samples under UHV (10-6 Pa). Scanning tunneling microscopy (STM) observation and X-ray photoelectron spectroscopy (XPS) measurements were carried out to analyze their surface structures and chemical species.It was observed that the surface decomposition of SiC had occurred after annealing at 800oC under UHV, and carbon nanocaps were formed on the SiC surface at 1200oC, which subsequently transformed into CNTs at higher temperature. When oxygen pressure was below 10-2 Pa, the nanocap formation was observed between 1150 and 1200oC irrespective of oxygen pressure. However, at 1 Pa of oxygen pressure, SiO2 layer was observed on the SiC surface after annealing at 1200oC and no carbon nanocaps were observed. These results indicate that it is necessary to anneal SiC below 1 Pa to form CNT, although the presence of oxygen enhances CNT formation below 10-3 Pa. The boundary between the active oxidation and the passive oxidation in SiC oxidation estimated from our results was well consistent with previous studies for SiC oxidation under higher oxygen pressure (>1 Pa)[2]. From our results, in order to grow CNT effectively, it is important to minutely control oxygen pressure.[1] T. Maruyama et al. Diamond and Related Materials,16(2007)1078.[2] Y. Song and F.W. Smith, Appl. Phys. Lett. 81(2002)3061.
9:00 PM - II5.28
Synthesis of Y-junction Carbon Nanotubes by Alcohol Chemical Vapor Deposition.
Masayuki Maekawa 1 , Yoshiyuki Suda 1 , Atsushi Okita 1 , Hirotake Sugawara 1 , Yosuke Sakai 1
1 Laboratory of Integrated Material Processings, Graduate School of Information Science and Technology, Hokkaido University, Sapporo Japan
Show AbstractSince carbon nanotubes (CNTs) have been discovered, they have attracted much attention as a promising material owing to their excellent properties. Y-junction carbon nanotubes (Y-CNTs) are interesting for their potential use in three-terminal nanoscale devices such as a transistor [1] because of their unique structures. So far, thiophene (C4H4S) has been used as an effective promoter for Y-junction structures. Recently, the growth of single-walled Y-CNTs without thiophene was also reported by Choi, et al [2]. In this report, they said that forming molybdenum carbide (Mo2C) is a key factor to synthesize a single-walled branching structure. However the reports on the growth mechanism of single-walled Y-CNTs are only a few. It is desirable to understand the growth mechanism and develop new growth techniques of single-walled Y-junction CNTs.We have studied variation of CNTs growth from binary catalysts, Co and Mo to synthesize branched CNT by alcohol chemical vapor deposition. We use catalysts films with different Co/Mo molar ratio on SiO2 substrates using a dip coating method [3]. The substrates were placed inside the quartz tubular reactor. The reactor was vacuumed by a rotary pump and heated up to operating temperature in a vacuum. Subsequently, H2 gas fed into the reactor as reduction for 20 minutes. After H2 supply was stopped, ethanol vapor was introduced for 60 minutes. The CNTs grown were analyzed with scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy.We found the changes in CNTs number density and G/D ratio of Raman spectra by Co/Mo molar ratio. We showed a tendency; the number density of CNTs decreased when Mo composition ratio increased. Moreover, the higher Mo composition ratio, the more catalyst particles attached on CNT surface. We focused on this attachment of growing nanotubes to catalyst particles on substrate, from which we expect to induce Y-junction structures. To increase the attachment of catalyst particles on growing CNTs, we prepared zeolite-supported Mo catalyst. It was placed upstream of the rector to supply Mo particles during CNTs growth. As the results, we found only a little amount of Y-CNTs grown on substrates when additional Mo particles were supplied. Details of this result will be discussed in the meeting.References [1] A.N. Andoiotis, et al, Phys. Rev. Lett., 87 (2001) 66802-1-4 [2] Y.C. Choi, et al, Carbon, 43 (2005) 2737-2741 [3] Y. Murakami, et al., Chem. Phys. Lett., 377 (2003) 49-54
9:00 PM - II5.29
Facile Synthesis and Characterization of Metal Nanoparticle-Decorated Carbon Nanotubes.
Yi Lin 1 , Kent Watson 2 , Sayata Ghose 2 , Joseph Smith 1 , John Connell 1
1 , NASA Langley Research Center, Hampton, Virginia, United States, 2 , National Institute of Aerospace, Hampton, Virginia, United States
Show AbstractMulti-walled carbon nanotubes (MWCNTs) were decorated with metal nanoparticles (e.g. Ag, Au, Pt, Ru, etc.) in a facile and electroless method using corresponding metal salts as starting materials but without the presence of any reducing reagents. Various microscopy and spectroscopy techniques were used to characterize the metal nanoparticle-decorated MWCNT samples. The decoration densities as well as the sizes and size distributions of attached metal nanoparticles were found to be closely related with several parameters, such as the chemical history of MWCNTs and the loading level of metal salts. Other characterization results and potential applications of such conveniently synthesized carbon-metal hybrid materials will also be presented and discussed.
9:00 PM - II5.3
Carbon Nanotubes Grown by a Two-Step CVD Method for Supercapacitors.
Aijun Yin 1 , Jimmy Xu 1 2
1 Engineering, Brown University, Providence, Rhode Island, United States, 2 Physics, Brown University, Providence, Rhode Island, United States
Show AbstractDensely-packed carbon nanotube (CNT) films or networks were fabricated directly on metal foils (Ni, Mo, Cu), carbon cloths, and carbon blacks via chemical vapor deposition (CVD). The catalysts used for CNT growth were spin-coated on the substrates with a solution consisting of iron nitrate and/or cobalt chloride, an organic solvent (ethanol, methanol, isopropanol, or a mixture of them), and a surfactant. The catalyst-coated substrate was first heated at 100 C in an oven for 30 min. The sample was then loaded into a tube furnace and annealed at 400 C for 2 h followed by H2 reduction at 650 C for 4 h. Finally, CNTs were grown at the same temperature using 10% C2H2 for a period of 10 to 60 min. In order to enhance the surface area, a two-step CNT growth method was applied. After the first CNT growth, a second layer of catalyst was deposited onto the CNT samples by dip-coating. The secondary CNT growth was then carried out under the same conditions. The substrates with films and networks of CNTs on CNTs were fabricated and used as the electrode materials for supercapacitors. Electric double layer capacitors (EDLCs) have been assembled with the CNTs as the electrodes and sulfuric acid (0.3 M – 1.0 M) as the electrolyte. The electrochemical performance of the EDLC was evaluated with cyclic voltammetry (CV). The EDLC with these components showed excellent electrochemical properties in terms of charging and discharging rates, specific capacitance, and cycling performances.
9:00 PM - II5.30
Anomalous Branch-structured Carbon Nanotubes on Silicon Substrates.
Yaser Abdi 1 , Shams Mohajerzadeh 1 , Javad Koohsorkhi 1 , Sarah Paydavosi 1
1 ECE, University of Tehran, Tehran Iran (the Islamic Republic of)
Show AbstractThe evolution of CNTs with an anomalous multi-level and tree-like structure on Si is reported. <100> P-type Si wafers, cleaned in an RCA#1 solution, are used as the substrate. The silicon samples are are coated with 5nm Ni layer using e-beam evaporation system at a temperature of 350oC and a base pressure of 1X10-6 torr. Coated wafers are then placed in a DC-PECVD chamber and a pressure of 3×10-2 torr is attained. At a hydrogen pressure of 1.6 torr and temperature of 650oC samples are annealed for 15 mins. To create nano-islands of Ni this step was followed by a hydrogen plasma treatment for 5 mins at the same temperature and pressure. Then acetylene was introduced to the chamber to start the CNTs growth. The flow of C2H2 and H2 in this step was 10 and 35 Sccm respectively and plasma power was 5-6 W/cm2. After 10-15 mins, vertically align CNTs are obtained. To observe the effects of the hydrogen bombardment on CNTs, the prepared samples are reloaded into the PECVD reactor and exposed to a 7W/cm2 power of H2 plasma at the temperature of 650oC for 5 mins. Our previous investigations of CNTs show that a tip growth mechanism is predominant for such nanotubes which are grown directly on Si substrates. A mere high energy hydrogenation step would lead to an explosion of the Ni tip side and hollow tubes are obtained. To protect the Ni nano-particles on the tip side of CNTs, they are coated by a thin layer of TiO2 prior to the hydrogenation step. The deposition of TiO2 on CNTs was carried out at a temperature of 220oC in an atmospheric pressure CVD reactor and in the presence of O2 and vapors of TiCl4 solution. Once the hydrogenation cycle on the CNT-coated Si substrates is finished, a second growth of CNTs is immediately initiated by flowing C2H2 (5sccm) into the reactor. The rate of H2/C2H2 in the second growth step was 35/5 as opposed to the initial growth (35/10). The lesser C2H2 flow leads to a thinner CNT diameter. This sequence is repeated for the third time to achieve almost single or double-wall nanotubes on the tips of the previously grown CNTs. SEM and scanning tunneling microscopy tools are used to study the structure of the nickel seed layer, the grown CNTs and the tree-like nanostructures. Such tree-like nanostructures can be grown on previously patterned nickel dots to form an ordered nerve-like structures suitable for gas detection. Also the possibility of mechanical sensing with micro-meter spatial resolution is investigated.In addition to the growth of CNTs in a multi-level manner, we have achieved single standing isolated CNTs grown on circular patterns. Such circular patterns are obtained by means of optical diffraction onto a resist-coated substrate (Argon spots). The evolved rings can be used as the mask to pattern the nickel seed layer at nano-scale with no need to a nanolithography tool. The growth on such ordered sub-micro-scale patterns is suitable for higher ordered photonic crystal applications.
9:00 PM - II5.31
Synthesis and Characterization of Phosphorus-Nitrogen doped Multiwalled Carbon Nanotubes.
Eduardo Cruz-Silva 1 , David Cullen 2 , Lin Gu 2 , Jose Manuel Romo-Herrera 1 , Emilio Munoz-Sandoval 1 , Florentino Lopez-Urias 1 , Bobby Sumpter 3 , Vincent Meunier 3 , David Smith 2 , Humberto Terrones 1 , Mauricio Terrones 1
1 Advanced Materials, IPICyT, San Luis Potosi, San Luis Potosi, Mexico, 2 School of Physics and Department of Physics, Arizona State University, Tempe, Arizona, United States, 3 Computer Science and Mathematic Division and Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractCarbon Nanotubes have attracted great attention of the scientific community due to their unique electronic and mechanical properties. Inclusion of non-carbon atoms into the graphite network, also known as doping, leads to different electronic and chemical properties due to variations in their electronic structure. In this work, multi-wall carbon nanotubes arrays were synthesized using a solution of ferrocene and triphenyl-phosphine on benzylamine as carbon source in a spray pyrolysis experiment. Iron phosphide (Fe3P) nanoparticles acted as catalyst for nanotube growth, leading to the formation of PN-doped multiwalled carbon nanotubes. Comprehensive characterization by SEM, HRTEM and STEM will be shown, as well as analytical information on the composition and stochiometry of the catalytic particles by EELS and EDX spectroscopy. Also, chemical stability is explored by means of thermogravimetric analysis in the presence of oxygen. These materials are promising for new applications as chemical sensors based on the reactivity of the doping atoms.
9:00 PM - II5.32
Multiwall BCN/C Nanotube Nanojunction and its Rectification Behavior.
Shuang Liu 1 , Lei Liao 1 , Kaihui Liu 1 , Xuedong Bai 1 , Enge Wang 1
1 , Institute of Physics, Chinese Academy of Sciences, Beijing China
Show AbstractTheoretical calculations have predicted that the band gap of BCN nanotubes can be tailored over a wide range by chemical composition rather than by geometrical structure. The following attempts toward the fabrication of BCN nanotube devices should be of great importance both to further understand their electronic properties and to develop their prospective applications for nanoscale electronic and photonic devices. Here, the direct synthesis of massive BCN/C nanotube intramolecular junctions has been realized via a bias-assisted hot-filament chemical vapor deposition (CVD) method. The electrical transport measurements of individual nanotube junctions were performed on a conductive atomic force microscopy (AFM). It is found that the BCN/C nanotube intramolecular junctions show a typical rectifying diode behavior.
9:00 PM - II5.33
Single-Walled Boron Nitride Nanotubes: Towards Large-Scale CVD Synthesis and Related Studies.
Wenlong Wang 1 2 , Yoshio Bondo 1 , Enge Wang 2 , Dmitri Golberg 1
1 International Center for Young Scientists (ICYS), National Institute for Materials Science, Tsukuba Japan, 2 Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing China
Show AbstractThe discovery of carbon nanotubes (CNTs) in the early 1990’s has stimulated much interest in nanotubular materials as a major area of research that is still flourishing. As the binary III-VI homolog of CNTs, the boron nitride nanotubes (BNNTs) share the most structural similarity with CNTs and can be regarded as an important complement to CNTs from both fundamental and application viewpoints. The existence of BNNTs was predicted early in 1994 and experimentally realized in the form of multi-walled nanotubes one year later. During the past decade, however, as compared to the tremendous progress witnessed in the field of CNTs, the advancement of BNNTs research has been rather slow as hindered by the unsolved difficulties in BNNTs synthesis, especially the single-walled BN nanotubes (BN-SWNTs).Among the various techniques established for the nanotublar material synthesis, the chemical vapor deposition (CVD) method is known to hold advantages in terms of experimental simplicity and potential for the large-scale and controlled synthesis. Here, we report on our recent advances in the catalytic CVD synthesis of BN-SWNTs, which was achieved via a systematical selection and optimization of catalysts, precursor, and CVD growth conditions. The present results, though still being preliminary, have demonstrated the first example of CVD growth of BN-SWNTs which have a reasonable prospect for achieving the final goal of large scale and controlled synthesis. Beyond SWNT synthesis, a comprehensive study on the chemical accessibility and processibility of BNNTs, especially concerning aspects different from those of CNTs, will also be presented.
9:00 PM - II5.34
Catalytic Growth of BN Nanotubes from Novel Precursors.
Myung Jong Kim 1 2 3 , Shahana Chatterjee 1 , Mark Bradley 1 , Mark Pender 2 , Larry Sneddon 1 , Benji Maruyama 2
1 Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania, United States, 2 Materials & Manufacturing Directorate, Air Force Research Laboratory, Dayton, Ohio, United States, 3 , Universal Technology Corporation, Dayton, Ohio, United States
Show AbstractMulti-walled and single-walled BN nanotubes have been effectively synthesized via catalytic pyrolysis or catalytic chemical vapor deposition from novel precursors. Chemically synthesized monomeric and polymeric compounds were found to be desirable precursors for BN nanotube synthesis. The catalytic effect of supported catalysts such as pre-made nanoparticles and thin film-derived catalysts made of various metals was clearly demonstrated, and the characteristics of BN nanotubes from different catalysts were studied. This method opens a catalytic route to synthesis of BN nanotubes with high efficiency and low defect density.
9:00 PM - II5.35
Nanostructured Cuprites-Copper Photovoltaic Cells from Epitaxial Hydrothermal Growth.
Xuejun Zhang 1 2 3 , Zhongyong Yuan 3 , Ming Su 1 2
1 Department of Mechanical, Materials, Aerospace Engineering, University of Central Florida, Orlando, Florida, United States, 2 College of Chemistry, Nankai University, Tianjin China, 3 , Nanoscience Tech Center, Orlando, Florida, United States
Show AbstractCopper (I) oxide (Cu2O) is one of the few p-type direct bandgap semiconductors with the bandgap of 2.17 eV. Its unique optical and magnetic properties have attracted increasing interest because of its potentials in solar energy conversion, nanoelectronics, magnetic storage, catalysis, and biosensing. The shape tunability of the copper oxide nanocrystals is of great importance to modulate their electronic structures, bonding energy, surface energies, and chemical reactivity. Despite many methods discovered for the synthesis of various nanostructured Cu2O, it remains a challenge to assemble the nanostructured materials into spatially regular patterns under template-free and mild conditions. We have synthesized the thin films of single-crystalline nanostructured cuprites of various morphologies (cubes, hexagonal, triangular plates, and octahedrons) on copper foil substrate using an epitaxial hydrothermal condition. The structural evolution from nanotube to nanooctahedron was identified through electron microscopy imaging, and their properties were characterized by UV-visible absorption, electron microscopy, X-ray diffraction and energy-dispersive X-ray analysis. The photovoltaic properties of the cuprites-copper thin films were measured using a sourcemeter. The nonlinear current-voltage curves under different illumination conditions confirm the hetero-junctions formed between the cuprites and copper.
9:00 PM - II5.36
Combinatorial Approach to Materials Fabrication from Higher Hierarchies of Rosette Nanotubes.
Grigory Tikhomirov 1 2 , Hicham Fenniri 1 2
1 Chemistry, University of Alberta, Edmonton, Alberta, Canada, 2 Supramolecular Nanoscale Assembly Group, National Institute for Nanotechnology , Edmonton, Alberta, Canada
Show AbstractTop down approach of materials fabrication has a good control of the resulting morphology, but it has a lower size limit below which design and construction of fine (nanometer and subnanometer) functional features is impractical. Bottom up approach, realized mostly through self-assembly of small building blocks, allows for preparation of large nanostructures, albeit with limited control over higher order aggregation. Here we report on a systematic approach to control not only lower, but also higher degrees of assembly from several angstrom to several microns in size.Combinatorial chemistry has been used extensively and successfully used in drug discovery. It allows for faster and more efficient search of a bioactive molecule with desired properties. The combinatorial parameters varied here are usually substituents on the target molecule that can be introduced using organic synthesis. The number of positions varied determines the dimension of the combinatorial matrix. In this work we built a multi-dimensional matrix covering (a) nature of the self-assembling modules (b) nature of the solvent in which self-assembly takes place, (c) concentration, and (d) sample aging.All the self-assembling modules investigated are derivatives of our previously reported G^C motif. The first level of self-assembly is well controlled through the self-complementary array of six hydrogen bonds on the G^C motif that leads to the formation of a six-membered supermacrocycle (rosette) maintained by 18 H-bonds. The second level, powered mostly by p–p stacking, is rosettes self-organization into a nanotube with the growth direction perpendicular to the rosette plane. The rosette nanotubes (RNTs) can further aggregate into bundles of several tubes that can subsequently undergo further aggregation into complex nano and microstructures. While the first two levels of RNTs multihierarchical self-assembly were well established1 for a number of G^C derivatives, subsequent aggregation beyond the RNT level still presents an important challenge. In the present work the first dimension of the matrix – the nature of self-assembling modules – was explored by synthesizing a set of six of G^C derivatives bearing variations at two substitution sites. Ten solvents covering a wide range of polarities constitute the second dimension of the matrix defining the modules interactions with each other and with the solvent and therefore controlling degree and fashion of RNT aggregation. The modes of self-assembly were further diversified in several cases by adding more dimensions to the combinatorial space, e.g. temperature at which the self-assembly is done, aging time and co-solvent. A wide range of nanoarchitectures including “bow-ties”, “hay stacks”, ”rice grains”, and “doughnuts” featuring dimensions from several nanometers to several microns were obtained and studied by scanning and transmission electron microscopy, (SEM, TEM), and atomic force microscopy (AFM)
9:00 PM - II5.37
Rosette Nanotubes: Factors Affecting the Self-assembly of the Monobases Versus the Twin Base System.
Usha Hemraz 1 2 , Hicham Fenniri 1 2
1 Chemistry, University of Alberta, Edmonton, Alberta, Canada, 2 , National Institute for Nanotechnology, Edmonton, Alberta, Canada
Show AbstractRosette Nanotubes1 (RNTs) are formed by the self-assembly of a guanine-cytosine motif (G^C), a hybrid of the DNA bases guanine and cytosine, to give a six membered macrocycle maintained by 18 H-bonds. RNTs are potential materials for use in the biomedical field.2 As such, it is important to understand the different factors affecting their self-assembly. In theory, any moiety covalently attached to the G^C base can be expressed on the nanotubes surface. However we anticipate that the self-assembly and stability of these functionalised RNs will also be governed by steric effects.3 Here we describe the synthesis and the self assembly of the Twin Base Lysine (TBL-K) and its monobase (MBL-K). While TBL-K self-assembles readily in water and methanol to give tubular structures of nanometer range, MBL-K does not form nanotubes. Various techniques were used to characterize the RNTs, namely, nuclear magnetic resonance (NMR), mass spectrometry, dynamic light scattering, circular dichroism, scanning electron microscopy, tapping mode atomic force microscopy and transmission electron microscopy. The factors, preventing self-assembly in the case of MBL-K, were investigated using 2D NMR experiments. REFERENCES:1.Fenniri H. et al, PNAS, 2002, 2, 6451-6418.2.Chun A. L et al, Nanotechnology, 2004, 15, S234-S239.3.Morales J.G et al, J. Am. Chem. Soc., 2005, 127, 8307-8309.
9:00 PM - II5.38
Novel Self-Complimentary Tricyclic Heterocycles: Expanding the Chemistry of Self-Assembled Rosette Nanotubes.
Gabor Borzsonyi 1 2 , Andrew Myles 1 , Ross Johnson 1 2 , Jae-Young Cho 1 , Takeshi Yamazaki 1 , Andriy Kovalenko 1 , Hicham Fenniri 1 2
1 Supramolecular Nanoscale Assembly Group, National Institute for Nanotechnology, Edmonton, Alberta, Canada, 2 Chemistry, University of Alberta, Edmonton, Alberta, Canada
Show Abstract9:00 PM - II5.39
Synthesis of Micro- and/or Mesoporous Silica Nanotubes using Rosette nanotubes as Templates.
Christophe Danumah 1 , Hicham Fenniri 1 , Usha Hemraz 1 , Jesus Moralez 1 2
1 Chemistry, University of Alberta, Edmonton, Alberta, Canada, 2 , Dupont Central Research and Development, Wilmington, Delaware, United States
Show Abstract9:00 PM - II5.4
Chemistry of Water-assisted CVD Growth of Single- and Double- Walled Carbon Nanotubes.
Naoki Yoshihara 1 , Hiroki Ago 1 2 , 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
Show AbstractHigh-yield synthesis of single- and double-walled carbon nanotubes (SWNTs, DWNTs) is important for the applications in composites and energy devices. We analyzed the change in the gas composition during the methane chemical vapor deposition (CVD) growth of SWNTs and DWNTs and found that the addition of Mo to Fe/MgO catalyst increases the initial catalytic activity and catalyst lifetime [1]. We also observed that a small amount of water vapor increased the nanotube yield over Fe-Mo/MgO catalyst due to extension of the catalyst lifetime [1], in consistent with the previous work [2]. The chemistry of the water-assisted nanotube growth is interesting and also important for the high-yield growth. However, the mechanism of water-assisted nanotube growth, such as water-induced oxidation and reaction kinetics, is still unclear. Here, we study chemistry involved in the water-assisted nanotube growth over a Fe-Mo/MgO catalyst, focusing on the water-induced oxidation and its effects on catalytic activity, based on the analysis of the effluent gas throughout the CVD. Together with CH4 and H2, CO gas was detected in the effluent gas during the water-assisted CVD growth. This CO emission was originated in the water-oxidation of carbon precipitates. In addition, a large amount of CO emission was observed in an initial few minutes of the CVD, which is accounted for by the reduction of the iron oxide catalyst with CH4 feedstock. From the equilibrium CO concentration, we revealed that all the introduced water vapor was fully converted to CO and H2 gasses and that about 1/1000 of the as-formed carbon precipitate was oxidized by water [3].[1] H. Ago, N. Uehara, N. Yoshihara, M. Tsuji, M. Yumura, N. Tomonaga, T. Setoguchi, Carbon, 44, 2912 (2006). [2] K. Hata, D. N. Futaba, K. Mizuno, T. Namai, M. Yumura, S. Iijima, Science, 306, 1362 (2004). [3] N. Yoshihara, H. Ago, M. Tsuji J. Phys. Chem. C, in press (2007).
9:00 PM - II5.40
InGaAs-GaAs Semiconductor Nanotubes: Exploring the Formation, Properties and Applications.
Ik Su Chun 2 , Varun Verma 1 , Jame Coleman 1 , Xiuling Li 1
2 Department of Materials Science and Engineering, University of Illinois, Urbana, Illinois, United States, 1 Electrical and Computer Engineering, University of Illinois, Urbana-Champaign, Urbana, Illinois, United States
Show AbstractIII-V semiconductor rolled-up nanotubes are formed when strained planar bilayers are released from the substrate by selectively removing the sacrificial layer. The relative strain in the bilayer creates a momentum for the planar sheet to roll up or down. The diameter of the tube is determined by the strain and thickness of the planar sheet, and the number of rolls can be controlled by etching time and mesa design. First discovered by Prinz et al.[Russia], these nanotubes could potentially be a new paradigm after quantum wells, quantum wires and quantum dots, and carbon nanotubes. When appropriate device structures are incorporated in the planar strained “wrapper”, they could lead to potential applications in nanoelectronics and nanophotonics. In this paper, we will report on the formation of InGaAs/GaAs based nanotubes of various dimensions and configuration, using lithographically defined stripe patterns on metalorganic chemical vapor deposition (MOCVD) broad area and selective area grown films. We will demonstrate the clear crystallographical orientation dependence, and the geometry effect of strain induced rolling behavior in the formation of the nanotubes. We will discuss the structural, mechanical and optical properties of these nanostructures. Applications using III-V nanotubes as active structures will also be explored.
9:00 PM - II5.41
Needle-like Co3O4 Nanotubes and Porous Nanorods as Superior Electrodes for Next Generation Lithium-ion Batteries.
David Lou 1 , Lynden Archer 1
1 Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York, United States
Show AbstractLithium ion batteries (LIBs) are currently the dominant power source for portable electronic devices. There is ever-growing need for next-generation LIBs with high energy and/or high power densities. New electrode materials have been discovered which can in principle deliver as high as 3 times the capacity of currently used graphite (< 372 mAh/g). However their practical use is largely hindered by poor capacity retention upon charge-discharge cycling. A common strategy for improvement in the community is to tailor the nanostructure (shape, size et al.) of electrode materials. Nanotubes are thought to be an advantageous nanostructure because of their multi-scale structural features: structural integrity in the micrometer scale (tube length), effective particle size (Li diffusion length) in nanometer scale (the wall thickness) and most importantly its hollow nature. In the present work, electrochemically active Co3O4 has been prepared with a needle-like nanotube morphology through a novel self-supported topotactic transformation approach. Initially β-Co(OH)2 nano-needles are formed followed by oxidative transformation in solution to needle-like Co3O4 nanotubes under constant mediation of air. β-Co(OH)2 nano-needles are also converted to porous Co3O4 nano-needles by calcination in air at 200 – 400 oC. When evaluated as electrode materials for LIBs, the as-prepared Co3O4 nanomateials show excellent rate capability and ultrahigh capacity with nearly 100% capacity retention for over 30 cycles. Considering the superior performance and cost-effective synthesis, we believe the as-prepared Co3O4 nanomaterials are promising candidates as negative electrodes for next-generation lithium ion batteries.
9:00 PM - II5.42
Synthesis of Bismuth Nanotubes by Microwave Irradiation.
Oxana Kharissova 1 , Mario Osorio 1 , Mauricio Garza 1
1 FCFM, UANL, Monterrey Mexico
Show AbstractThe electronic properties in bismuth bulk promise unusual properties in bismuth nanotubes. So we have used software about the first-principles molecular dynamics to study the stabilities and electronic properties of bismuth nanotubes. In this paper we report synthesis of Bi nanotubes by microwave irradiation; being this method easier and cheaper than the common synthesis methods. The samples were warmed up in vacuum during 5, 10 and 15 minutes in a conventional microwave oven of 2,45 GHz and 1300 W. The resulting Bi nanotubes were characterized using transmission electron microscopy (TEM) for its structure and atomic force microscopy (AFM) for its size.
9:00 PM - II5.43
Titania Nanotubes Synthesized by Anodization in Chlorine Containing Media.
Eugen Panaitescu 1 , Christiaan Richter 2 , Latika Menon 1
1 Physics, Northeastern University, Boston, Massachusetts, United States, 2 Chemical Engineering, Northeastern University, Boston, Massachusetts, United States
Show AbstractTitanium oxide nanotubes are drawing increased scientific interest for applications in various fields such as solar energy conversion, gas sensing, or nanobiology and nanomedicine. Our lab recently reported about a new synthesis route of such nanotubes via anodization in chlorine containing media. We performed an extensive study on a wide range of anodization parameters such as the anodization voltage, the chlorine ions concentration, acidity and nature of the electrolyte, or anodization time. Voltage and chlorine concentration have been identified as critical factors in the nanotubes formation process, as slight changes of these parameters determine dramatically different results, thus making the process very sensible to their local variation. We proposed a basic growing mechanism, and furthermore predicted and employed optimal conditions for better uniformity and coverage all over the sample and/or high yield of nanotubes containing precipitates. Also, different methods for the characterization of the nanotubes and of their subsequent crystallization by annealing have been employed such as transmission electron microscopy and selected area electron diffraction, RAMAN spectroscopy, reflectivity, and calorimetric measurements.
9:00 PM - II5.44
Anodised Titania Nanotubes: Nucleation, Early Growth of the Film and Deduction of the Growth Mechanism from Electron Microscopy Characterisation.
Domenico Regonini 1 , Angkhana Jaroenworaluck 2 , Ron Stevens 1 , Chris Bowen 1 , Duncan Allsopp 3
1 Materials Research Centre (Dept. of Mechanical Engineering), University of Bath, Bath United Kingdom, 2 , MTEC: National Metal and Materials Technology Center, Pathumthani Thailand, 3 Department of Electronic & Electrical Engineering, University of Bath, Bath United Kingdom
Show AbstractThis paper will discuss a possible growth model mechanism for the generation of titanium dioxide nanotubes (NTs) via anodisation of titanium metal in fluorine-containing electrolytes. Our assumptions are based on information gained from Scanning and Transmission Electron Microscopy (SEM and TEM). Experiments performed using both water and organic media suggest the tubular titania nanostructure is the result of the link up of spherical nanoparticles of titanium oxide/hydroxide which, under the action of the electric field, align with each other to form channels and optimise the current flow within the film. Those particles, especially in based-water electrolytes, develop a certain degree of hydration [Ti(OH)4], but they dehydrate to TiO2 during the evolution of the anodic film in a similar fashion to a gel hardening process. Whether the nanoparticles also contain gas species, which may contribute to the expansion of the cavities (bubbles) and the generation of channels, has still to be clarified; but there is evidence of oxygen evolution during the early stages of the process.A comprehensive TEM analysis of the early stages of the growth of anodised titania NTs synthesized in water is also presented. When using an initial voltage ramp before holding the anodisation voltage at a constant value, cavities begin to form with simultaneous growth of the oxide. As a result, a high degree of pore interconnection is achieved from the very beginning of the process, creating the condition for the growth of thicker NTs layers. The structure of the film remains amorphous (to 200kV electrons) in nature. There is some evidence of small, isolated, regions of ordered structure in the as formed film, the crystallites being in the size range 3-10nm. The crystallites tend to be present in the more dense arms of the interconnected porous structure that forms in the early stages of the process, as the pores start to link up to form the tubular array. While the initial titania nanotubes are amorphous in nature, details about the heat treatment of the nanotubes to form anatase and rutile will also be discussed.
9:00 PM - II5.45
From Single Molecules to Nanoscopically Structured Functional Materials by Controlling the Surface Chemistry Layered Metal Chalcogenides.
Wolfgang Tremel 1 , Aswani Yella 1 , Muhammad Tahir 1 , Helen Annal Therese 1 , Martin Panthoefer 1 , Ute Kolb 2 , Werner Mueller 2 , Heinz-Christian Schroeder 2
1 Chemistry, University of Mainz, Mainz Germany, 2 Medicine, Universität Mainz, Mainz Germany
Show Abstract9:00 PM - II5.46
Opening and Controlling the Nano-windows on the Carbon Nanohorns by the Treatment in Hydrogen Peroxide.
Takashi Yamaguchi 1 , Shunji Bandow 1 , Masako Yudasaka 2 , Sumio Iijima 1 2
1 , Meijo university, Nagoya Japan, 2 , NEC Corporation, JST, Tsukuba Japan
Show AbstractBoth methods, based on the combustion in the oxygen gas and the oxidation in the acid solution, are well known as the opening technique for the carbonaceous materials. Although those methods work well, the interior spaces of the carbonaceous materials are often stuffed by the nanometer-sized byproducts during opening the nano-windows. Therefore we cannot use the nano-space effectively.Here, we applied the liquid phase treatment by using the aqueous solution of hydrogen peroxide in order to open the nano-window on the sidewall of the carbon nanohorn that can be produced without using the metal catalyst. In the present study, we analyze the opening process of the nano-windows by using TEM and ESR. According to the TEM observation, tiny amorphous carbon materials covering over the nanohorns could be removed by refluxing in the solution of hydrogen peroxide at 90°C for 5 min. Further treatment for 5 to 30 min gave slight destruction of nano-horn structure, and then the treatment in excess of 30 min gave serious damage on the horn-structure. By conducting the treatment for more than 60 min., it was found that the horn structure was completely disintegrated. It is known that the spectral line width of ESR from the nanohorns is strongly dependent on the partial pressure of the oxygen gas. We used such ESR feature and characterized the general feature for the nano-windows located on the nanohorn wall. Then it was found that the mild treatment using the hydrogen peroxide effectively opens the small sized nano-windows that sizes are just in the order for entering the oxygen molecules, and their sizes can be controlled by the treatment times. Experimental details and the conditions for opening the nano-windows are presented in the poster.
9:00 PM - II5.47
Fabrication of Free-standing Fullerene Nanowire using Direct Electron Beam Writing and Sacrificial Dry Etching.
Toshiyuki Tsuchiya 1 , Tomoya Jomori 1 , Koji Sugano 1 , Osamu Tabata 1
1 Dept of Microengineering, Kyoto University, Kyoto Japan
Show AbstractThis paper reports the fabrication of free-standing fullerene(C60) nanowires on a silicon substrate as a doubly-supported beam in order to fabricate nano electro mechanical system (NEMS) devices. By irradiating vacuum-deposited fullerene thin film with electron beam (EB), polymerized fullerene nanowires were patterned. Then, free-standing structures of the fullerene nanowires were obtained by sacrificial etching using XeF2 gas.Carbon nano materials such as fullerene and carbon nanotube are expected to be used in a wide range of applications in nanotechnology domain because of their high electrical and thermal conductivity and mechanical stiffness. New applications were expected not only electron devices but also electromechanical devices. In order to use these materials in MEMS or NEMS, their mechanical properties should be evaluated. In this research, a new on-chip tensile testing device using electrostatic MEMS is being developed to evaluate the mechanical properties of nano-scale materials. As discussed frequently in applications of nanoscaled materials, one important issue of the research is the specimen fabrication and alignment of nano materials. In this paper, a new technique for fabricating a free-standing fullerene specimen on a MEMS structure was proposed and demonstrated.The process flow of the proposed fabrication technique is as follows;(a) Deposition of fullerene thin film: An approximately 15-20 nm thick film on silicon substrate was deposited using vacuum evaporation.(b) Fullerene polymerization by EB irradiation: Thin polymerized fullerene wires of 50 to 2000 nm wide were patterned using a conventional EB lithography tool.(c) Wet etching of fullerene: The fullerene nanowires were formed by etching the un-polymerized area of the fullerene films using toluene and hexane (1:6) solvent. The polymerized fullerene became insoluble against the solvent.(d) Mask formation for silicon sacrificial etching: Using the standard photolithography process, photoresist was patterned, which defines the length of the free-standing wire. The designed length of fullerene nanowire that was equivalent to the width of the photoresist openings was 2 μm.(e) Silicon sacrificial dry etching: Using photoresist pattern as a mask, silicon substrate was etched by XeF2 gas to release the nanowire. Gas phase etching is indispensable for preventing the stiction and fracture of the nanowire during the release process. Minimum line width of the pattern of polymerized fullerene nanowires on silicon substrate is approximately 300 nm. The position and dimensions of the nanowire were successfully controlled by optimizing the condition of the EB irradiation. From micro Raman spectroscopic analysis the pattern was identified as a polymerized fullerene. After the sacrificial etching, the free-standing doubly-clamped structures of fullerene nanowires were fabricated. The dimensions of the fabricated doubly-clamped wires were 2 μm long, 400 nm wide and 15 nm thick.
9:00 PM - II5.48
Polymerization of Fullerene in Solution with Free Electron Laser Irradiation.
Nobuyuki Iwata 1 , Yasunori Iio 1 , Shingo Ando 1 , Ryo Nokariya 1 , Hiroshi Yamamoto 1
1 Electronics & Computer Science, College of Science & Technology, Nihon University, Chiba Japan
Show AbstractWe have been studying the polymerization of C60 with free electron laser (FEL) irradiation. The FEL has the features of wavelength variability and extremely sharp pulse width, several hundreds femto-second. The purpose of this work is to synthesize an amorphous and polymerized fullerene bulk. In our previous works the optimization is carried out concerning about the irradiation wavelength, that is 450 ~ 500 nm.[1] Inserting some molecules with double bonds between C60 molecules is expected to reduce the directionality for polymerization. Amorphous C60 polymer with macro scale is anticipated. In this presentation FEL was irradiated to C60 precipitates on the bottom in the saturated toluene. The effect of FEL irradiation to the specimens grown by liquid-liquid interfacial precipitation (LLIP) method will be also discussed. Those results are compared to that of specimens in vacuum with pressed powder. The C60 powder (99.5%) was pressed to be bulk specimen and 3rd harmonics 500 nm FEL was irradiated in a vacuum after annealing at 120 degree C. Another process for polymerization in solution is as follows. The C60 powder 0.2 g was dissolved in toluene 30 ml, immediately sonicated for 5 min. The solution was maintained for 3 days in a refrigerator. FEL was irradiated for one hour to the precipitated C60 powder at the bottom of a glass bottle in saturated toluene. Irradiated powder was pressed and the surface was evaluated by optical microscope and Raman analysis. The pressed bulk specimen with FEL irradiation showed typical photo-polymerized peak at 1460 cm-1 in Raman spectrum detected from the shinny grain with ~5μm size. At the other regions pristine Ag(2) 1469 cm-1 was observed, hence the shinny grains were polymerized. The optical image of the FEL irradiated precipitates in the saturated toluene showed that the shinny grains became larger to approximately 30μm. The Raman spectrum was similar to that of pressed bulk. FEL irradiation in solution was effective to promote C60 polymerization. [1] S.Ando, R.Nokariya, R.Koyaizu, N.Iwata, and H. Yamamoto,”Synthesis of C60 Polymer by Free Electron Laser Irradiation with Hole-Doping Effect”, will be published in Trans. MRS-J (2007)
9:00 PM - II5.49
Phase Transformations in C60 and C70 Peapods after High Pressure - High Temperature Treatments.
Matthieu Chorro 1 , Pascale Launois 1 , Agnieszka Iwasiewicz - Wabnig 2 , Laure Noe 3 , Stephane Rols 4 , Marc Monthioux 3 , Bertil Sundqvist 2 , Julien Cambedouzou 1
1 , Laboratoire de Physique des Solides UMR CNRS 8502 Université Paris-Sud, F-91405 Orsay France, 2 Department of Physics, Umeå University, S-90187 Umeå Sweden, 3 , Centre d'Elaboration des Matériaux et d'Etudes Structurales UPR CNRS 8011, F-31062 Toulouse France, 4 , Institut Laue Langevin, F-38042 Grenoble France
Show Abstract9:00 PM - II5.5
Vertically Aligned Single-walled Carbon Nanotube Regrowth After Peeling from an Fe-coated Alumina Substrate.
Cary Pint 1 , Sean Pheasant 2 , Nolan Nicholas 1 , Matteo Pasquali 3 , Robert Hauge 2
1 Physics, Rice University, Houston, Texas, United States, 2 Chemistry, Rice University, Houston, Texas, United States, 3 Chemical Engineering, Rice University, Houston, Texas, United States
Show AbstractVertically aligned single-walled carbon nanotubes (VA-SWNT) with lengths exceeding 0.5 millimeters are grown in a hot filament chemical vapor deposition (HFCVD) apparatus. After growth of the VA-SWNT on an Fe coated alumina substrate, we demonstrate the process of regrowth after peeling the VA-SWNT from the substrate with an adhesive material and preparing the substrate for a second growth with an oxidation process. As we report, the oxidation process is found to be essential for activating catalytic particles for regrowth. A detailed analysis of regrowth under different oxidizing conditions is presented, and we demonstrate average regrowth of up to 50% in some cases, with local regions of regrowth of up to 75%. VA-SWNT densities, heights, and chirality distributions in the first and second stages of growth are characterized, and we emphasize the importance of a second phase of growth from the same substrate toward future interest in scale-up production of VA-SWNT material.
9:00 PM - II5.50
Inorganic Closed-Caged Fullerene-Like Nanoparticles.
Rita Rosentsveig 1 , Ifat Kaplan-Ashiri 1 , Alexander Margolin 1 , Maya Bar-Sadan 1 , Alon Katz 1 , Reshef Tenne 1
1 Materials and Interfaces, Weizmann Institute of Science, Rehovot Israel
Show AbstractIn early nineteen’s of XX it has been found that nanosized sheets of 2D materials are unstable against folding thus forming closed-caged nanostructures, later called inorganic fullerene-like nanoparticles (IF) in analogy to the carbon predecessors. The first obtained IFs of tungsten disulfide were later accompanied by nanotubes and nanospheres of other layered compounds (typically MxZy, where M is metal, e.g. W, Mo, Ni, Nb, V, Ti, etc; while Z is S, Se, Cl, O, etc). The synthetic strategies leading to IFs include physical transformation of initial material or chemical way. The chemical method is determinant in this work due to easier scaling-up and higher purity of desired product.The successful synthesis of WS2 closed-caged nanostructures paved the way to understanding the nature of their formation. The comprehension of this and subsequent processes opened the possibility to produce sufficient amounts of 100% pure IF phase. The availability of new materials has enabled systematic study of their properties.It was found that the size and unique form of those novel particles combines resulting in changing their properties with respect to the 2D chemical analogs. The reducing of friction is typical application for many layered materials. The tribological testing of IF nanoparticles showed their superb behavior, especially under harsh conditions.The small size of individual nanoparticles makes their manipulation and measuring of their properties a challenging task, however some success has been achieved in the present. For instance, a combination of atomic force microscopy and scanning electron microscopy was used to determine the Young’s modulus of an individual multiwall WS2 nanotube. The fine agreement of the experimental value (170 GPa) with the theoretical predictions corroborates the perfect crystallinity of the obtained nanotubes.The outstanding properties of new materials together with their availability made it possible to test their practical applications in various spheres.
9:00 PM - II5.7
New Insights in the Structure and the Growth Mechanisms of Iron-filled Multi-walled Carbon Nanotubes Carpets from Aerosol-assisted CCVD.
Vasile Heresanu 1 , Celia Castro 2 , Mathieu Pinault 2 , Julien Cambedouzou 1 , Pascale Launois 1 , Mathieu Kociak 1 , Odile Stephan 1 , Martine Mayne-L'Hermite 2 , Cecile Reynaud 2
1 , Laboratoire de Physique des Solides, UMR CNRS 8502, Université Paris Sud, Orsay France, 2 , Laboratoire Francis Perrin, URA CEA-CNRS 2453, DSM-DRECAM-SPAM, CEA Saclay, Gif Sur Yvette Cedex France
Show AbstractSamples of well aligned iron filled multiwall carbon nanotubes (MWNTs) with high yield and high purity can be formed by aerosol-assisted Catalytic Chemical Vapor Deposition (CCVD) [1]. In this process, the reactor is continuously fed by a mixed aerosol containing both carbon source (liquid hydrocarbon) and catalyst precursor (ferrocene). Based on the use of sequential injections of aerosols, we have recently identified a base growth mechanism all along aligned nanotubes formation from catalytic particles localised at the surface of the substrate [2, 3]. However, the nature and morphology of the catalytic particles during the nanotubes growth is still under debate. Different hypotheses have been reported in the literature, arguing that the catalytic particles could be pure iron, iron carbide, iron oxide, or liquid particles. Ex situ analyses of the samples (Mossbauer and X-Ray Diffraction) demonstrated the occurrence of several iron-base phases in the nanotubes carpets [4]. We have developed a new synthesis procedure involving a quenching step at the end of the carpet growth in order to analyse the role of the cooling dynamics on the structure and the chemical composition of the catalytic particles. Based on a comprehensive investigation involving local (transmission electron microscopy, electron diffraction) and global probes (x-ray diffraction), as well as complementary chemical composition analysis using electron energy loss spectroscopy, we give in this communication a new lightening on the nature of the catalytic particles [5]. We demonstrate that the catalytic particles during the nanotubes growth are not oxidized. We furthermore evidenced the influence of the cooling dynamics on the crystallinity of catalyst particles, in particular from the faceting point of view. Finally, a possible formation mechanism of the encapsulated nanowires found inside MWNT is discussed in the light of these new results. These objects are thought to be promising for a variety of applications, including the field of magnetic storage [6], and their use could be all the more interesting as their synthesis route by chemical vapor deposition is well controlled.[1] M. Mayne et al., Chem. Phys. Lett. 338, 101 (2001)[2] M. Pinault, M. Mayne-L’Hermite, C. Reynaud, V. Pichot, P. Launois, D. Ballutaud, Carbon, 43 14 (2005) 2968-2976[3] M. Pinault, V. Pichot, H. Khodja, P. Launois, C. Reynaud, M. Mayne-L’Hermite, Nanoletters, 5, 12 (2005) 2394-2398[4] V. Pichot et al., Appl. Phys. Lett. 85, 473 (2004)[5] V. Heresanu et al., in preparation[6] N. Grobert et al., Appl. Phys. Lett. 75, 3363 (1999)
9:00 PM - II5.8
Oriented Growth of Ultra-Long Single-Walled Carbon Nanotubes.
Limin Huang 1 , Zhang Jia 1 , Stephen O'Brien 1
1 Applied Physics, Columbia University, New York, New York, United States
Show AbstractSingle-wall carbon nanotubes (SWNTs) have unique structural, mechanical, thermal and electrical properties, which make them attractive and important building blocks for nanotechnology. Oriented assembly of SWNTs presents a crucial prerequisite for both fundamental research at the individual SWNT level and nanotube-based device fabrication and applications. I review our own research efforts in orientation control by chemical vapor deposition, and how this enables the fundamental characterization of individual SWNTs, and contributes to nanotube-based device fabrication and applications. In our CVD process, CoMo doped mesoporous SiO2 (SBA series, a type of thermally stable mesoporous silica materials with ordered pore structures and uniform nanoporous channel) or Cobalt (Co) ultrathin films were used as catalysts, respectively. Ethanol was used as a carbon feedstock because it does not tend to form amorphous carbon upon dissociation. The mesoporous silica has a uniform and ordered nanoporous channel of 2-6 nm in diameter and a high surface area (> 400 m2/g), which can control (limit) the size of the active component CoMo and help reduce the tendency of particle aggregation, while maintaining accessibility of the active species. In the case of the Co ultrathin film catalyst, the as-deposited Co 0.5-1 nm film balls up on heating to form individual Co nanoparticles after a high temperature annealing (850oC and Ar/H2 flow), ethanol CVD is then performed.
9:00 PM - II5.9
Growth and Applications of Vertically Aligned Large-diameter Double-walled Carbon Nanotube Arrays.
Lijie Ci 1 , Robert Vajtai 1 , Pulickel M. Ajayan 1
1 , Rensselaer Polytechnic Institute, Troy, New York, United States
Show Abstract
Symposium Organizers
Kenji Hata AIST
Annick Loiseau Laboratoire d'Etude des Microstructures (LEM)
Yoke Khin Yap Michigan Technological University
Ming Zheng DuPont Central Research and Development
II6: Non-carbon Nanostructures I
Session Chairs
Kenji Hata
Annick Loiseau
Yoke Khin Yap
Ming Zheng
Tuesday AM, November 27, 2007
Room 312 (Hynes)
9:00 AM - **II6.1
Single-walled Boron Nitride Nanotubes: A Particular Class of Nanotubes.
Raul Arenal 1
1 , LEM, CNRS-ONERA, Chatillon France
Show AbstractBoron nitride nanotubes (BNNTs) are a very attractive alternative to those of carbon (CNTs) in regards to possible applications. In fact, in contrast to CNTs which are metallic or semi-conductors depending on their atomic structure, BNNTs are insulators with a gap around 6 eV [1]. These tubes can be used for high-power-high-frequency electronic devices; they also have outstanding mechanical properties, are chemically inert, and can be used as protective cages in the nanoworld. Nevertheless, contrary to CNTs, where, a high number of studies have been realised on their structure and physical properties, a few is known on BNNTs, due to the low amount of NTs produced and available. ONERA has developed in 2001 the first synthesis route of single-walled BNNTs in high quantity which helped the development of this research area. This synthesis method consists in vaporizing a BN target by a continuous CO2 laser under a N2 atmosphere [2,3]. This communication will review the studies concerning the synthesis process, the atomic structure, the chemical composition as well as the determination of the chemical bonding (down to sub-nanometer scale by spatially resolved electron energy loss spectroscopy (EELS) [3]) and different measurements (vibrational and optoelectronic properties) done on these BNNTs. A detailed knowledge of the atomic structure of these nanotubes (chiral angle and diameter) is fundamental to understanding their growth mechanism. Electron diffraction, which is the most reliable technique for obtaining this structural information, is employed as well as high resolution transmission electron microscopy (TEM) [5]. The data obtained from all these TEM studies allow us to identify the fundamental factors controlling the nanotube growth and support a phenomenological growth model which will be presented [3]. Concerning the vibrational properties of BNNTs the Raman spectroscopy measurements in the UV range will be discussed as well as the ab initio calculations that allow their interpretation [6,7]. Different approaches have been employed in order to study the opto-electronic properties of the BNNTs: optical absorption, luminescence (cathodo- and photo-lum.) as well as the investigation of the dielectric response by EELS in the low-loss energy region (< 50 eV) on individual tubes [8-11]. All these different results will be presented. [1] X. Blase, et al, Europhys. Lett. (1994)[2] R.S. Lee, et al., Phys. Rev. B (2001)[3] R. Arenal, et al., Chem. Mat., submitted (2007)[4] R. Arenal, et al., Ultramicroscopy, submitted (2007)[5] R. Arenal, et al., Appl. Phys. Lett. (2006)[6] L. Wirtz, et al., Phys. Rev. B (2003)[7] R. Arenal, et al., Nano Lett. (2006)[8] J.S. Lauret., et al., Phys. Rev. Lett. (2005)[9] M. Silly, et al., Phys. Rev. B (2007)[10] P. Jaffrennou, et al., Chem. Phys. Lett. (2007)[11] R. Arenal, et al., Phys. Rev. Lett. (2005)
9:30 AM - **II6.2
Optical Properties of BN Nanotubes and Hexagonal BN: Role of Defects.
Angel Rubio 2 , Ludger Wirtz 1
2 European Theoretical Spectroscopy Facility and MAterials Physics Department, Universidad del Pais Vasco and Centro Mixto CSIC-UPV/EHU, San Sebastián Spain, 1 Europeant Theoretical Spectroscopy Facility, Edificio de I+D+I Korta, Universidad del Pais Vasco, San Sebastian Spain
Show AbstractTuesday, Nov 27New Presenter *II6.2Optical Properties of BN Nanotubes and Hexagonal BN: Role of Defects. Ludger Wirtz
10:00 AM - II6.3
Luminescence Properties of Individual Boron Nitride Nanotubes.
Perine Jaffrennou 1 2 3 , Julien Barjon 4 , Jean Sebastien Lauret 3 , Brigitte Attal-Tretout 2 , Francois Ducastelle 1 , Annick Loiseau 1
1 LEM, ONERA, Chatillon France, 2 DMPH, ONERA, Palaiseau France, 3 LPQM, ENS Cachan, Cachan France, 4 GEMac, CNRS Bellevue, Meudon France
Show AbstractBoron nitride nanotubes (BNNT) are composed of rolled up hexagonal boron nitride (hBN) sheets and were discovered in 1995, a few years after carbon nanotubes. According to calculations, they are, as their related bulk material, h-BN, wide band gap semiconductors and are expected to emit strongly in the UV range. It is also predicted that their electronic properties and their optical properties should not depend too much on their diameter and helicity, in contrast to carbon nanotubes. Recent theoretical calculations show that, as has been experimentally demonstrated for h-BN, strong excitonic effects should occur in BNNT, with localized excitons of very large binding energy (quasi-Frenkel excitons). Such effects have not been experimentally demonstrated yet especially because of a lack of pure BNNT samples. In our study, cathodoluminescence spectroscopy and imaging on individual BNNT have been undertaken and are compared to photoluminescence and absorption spectroscopies on BNNT macroscopic samples. These experiments confirm that their are strongly UV luminescent materials and show that luminescence occurs all along the nanotube. The spectra are compared to those obtained for h-BN in order to understand the origin of this strong luminescence. The first results show that the optical signal of BNNT is composed of two emission bands located in the range 3–6 eV. The far UV luminescence band observed at about 5.3 eV is attributed to quasi Frenkel excitons and the 3.8 eV luminescence band is related to impurity centers (C or O impurities).
10:15 AM - **II6.4
First-Principles Studies of Boron Nanostructures: Clusters, Sheets and Nanotubes.
Ravi Pandey 1 , Kah Lau 1
1 Physics, Michigan Tech, Houghton, Michigan, United States
Show AbstractThe elemental boron exhibits rather fascinating chemical versatility which has been well studied in the crystalline solid form, but has scarcely been investigated in the nanostructure form. In order to understand and properly describe the unusual bonding features for boron nanostructures, including clusters, sheets and nanotubes, we have initiated a detailed and systematic first principles study based on density functional theory. Specifically, the size-dependent evolution of topological structures and bonding characteristics of boron clusters will be discussed. Based on the trend observed in the boron clusters, the unique properties of boron sheets and boron nanotubes will be described. Moreover, the ballistic electron transport in single-walled boron nanotube relative to that of single-walled carbon nanotubes will be considered. It is expected that the theoretical results obtained in the present thesis will initiate further studies on boron nanostructures, which will be helpful in understanding, designing and realizing boron-based nanoscale devices.
10:45 AM - II6.5
Synthesis Of Boron Single-Wall Nanotube Using Optimized Mg-Mcm-41.
Fang Fang 1 , Mathieu Pinault 1 2 , Dragos Ciuparu 1 , Claire Anderson 1 , Chuan Wang 1 , Lisa Pfefferle 1
1 , Chemical Engineering Department, Yale University, New Haven, Connecticut, United States, 2 , Laboratoire Francis Perrin, URA CEA-CNRS 2453, DSM-DRECAM-SPAM, CEA Saclay, Gif Sur Yvette Cedex France
Show AbstractSynthesis of pure Boron single-wall nanotube by reaction of BCl3 with H2 over 1%Mg-MCM-41 was previously reported by our group [1]. Preliminary results suggest Mg-doped Boron nanotube show high temperature superconductivity, so efforts to produce large samples for characterization are important. Parameters including catalyst nature, reaction time and temperature, reactant ratio, BCl3 flow rate, are observed to significantly affect both the yield and quality of the Boron nanostructures. The structure of the catalyst and loading condition of Mg are crucial in optimizing the selectivity to boron nanotube over other nanostructures produced. Optimization of the synthesis conditions for 1%Mg-MCM-41 shows a silicate solution pH=12.0 giving the best result, leading to the highest yield of Boron nanotube and retaining the template structure during synthesis. Based on the tube diameter and template structure sensitivity, a mechanism involving the physical templating of Boron nanotube is proposed. Tubular nanostructures growing out of the silica template are captured in TEM, and confirmed by EELS for Boron. Raman is employed to confirm the tubular geometry and to show the absence of Carbon nanotube contamination. After two rounds of NaOH washes removing the silica template, bundles of nanotubes are found. EXAFS of Boron K-edge further evaluate the structure and exclude the existence of Boron Nitride. Since Mg ions are relatively large, high loading incorporation can collapse the pores in the mesoporous silica template. Ni is introduced by co-incorporation with Mg to increase activity while maintaining in template stability. This catalyst both shifts the optimal reaction temperature down, and improves the Boron nanotube yield. [1] D. Ciuparu et al., Journal of Physical Chemistry B 108 13 (2004) 3967-3969
11:00 AM - II6: NCarbon-1
BREAK
II7: Carbon Nanostructures IV
Session Chairs
Ravi Pandey
Ralph Scheicher
Yoke Khin Yap
Tuesday PM, November 27, 2007
Room 312 (Hynes)
11:30 AM - **II7.1
Real-time ab initio Simulations of Excited-state Dynamics in Nanostructures.
David Tomanek 1
1 Physics and Astronomy Department, Michigan State University, East Lansing, Michigan, United States
Show AbstractCombining time-dependent ab initio density functional calculations for electrons with molecular dynamics simulations for ions, we investigate the effect of excited-state dynamics in nanostructures. In carbon nanotubes, we find electronic excitations to last for a large fraction of a picosecond [1]. The de-excitation process is dominated by coupling to other electronic degrees of freedom during the first few hundred femtoseconds.Later, the de-excitation process becomes dominated by coupling to ionic motion. The onset point and damping rate in that regime change with initial ion velocities, a manifestation of temperature dependent electron-phonon coupling. Considering the fact that the force field in the electronically excited state differs significantly from the ground state, as reflected in the Franck-Condon effect, atomic bonds can easily be broken or restored during the relatively long lifetime of electronic excitations. This effect can be utilized in a "photo-surgery" of nanotubes, causing structural self-healing at vacancy sites [2] or selective de-oxidation processes induced by photo-absorption [3].Also, electronic excitations are a key ingredient for the understanding of sputtering processes in nanostructures, induced by energetic collisions with ions [4].In collaboration with Yoshiyuki Miyamoto, Angel Rubio, and Arkady Krasheninnikov. Supported by NSF NSEC grant EEC-425826 and NSF NIRT grant ECS-0506309[1] Yoshiyuki Miyamoto, Angel Rubio, and David Tomanek,Phys. Rev. Lett. 97, 126104 (2006).[2] Yoshiyuki Miyamoto, Savas Berber, Mina Yoon, AngelRubio, and David Tomanek, Chem. Phys. Lett. 392, 209(2004).[3] Yoshiyuki Miyamoto, Noboru Jinbo,Hisashi Nakamura, Angel Rubio, and David Tomanek, Phys. Rev. B70, 233408 (2004).}[4] Yoshiyuki Miyamoto, Arkady Krasheninnikov, andDavid Tomanek, Phys. Rev. Lett. (2007).
12:00 PM - **II7.2
NanoBuds – A Novel Carbon Nanomaterial: Synthesis, Structure and Field Emission Properties.
Esko Kauppinen 1 2
1 Center for New Materials & Laboratory of Physics, Helsinki University of Technology, Espoo Finland, 2 VTT Biotechnology, VTT - Technical Research Centre of Finland, Espoo Finland
Show AbstractWe present synthesis, structure and field emission properties of a novel hybrid carbon nanomaterial, NanoBudsTM, combining fullerenes and single-walled carbon nanotubes (CNTs) . NanoBuds consist of fullerenes attached to the outside surface of CNTs, i.e. nanotubes are functionalized with fullerenes (1). Two floating catalyst methods for their selective synthesis have been developed, using pre-made iron catalyst particles by a hot wire based PVD method or grown in situ via ferrocene vapour decomposition in the presence of CO and trace amounts of H2O and CO2. TEM images show spherical structures i.e. fullerenes at the surface of the tube. Their spherical nature was confirmed by tilting samples within a HR-TEM. Statistical size measurements on the basis of HR-TEM images revealed that the majority of fullerenes consists of C42 and C60. Interestingly, evidence of C20 fullerenes, the smallest possible dodecahedra is found. Raman spectra show a pronounced G-band at 1600 cm-1 associated with CNTs, and only a weak D-band at 1320-1350 cm-1. The main peaks in MALDI-TOF spectrum are attributed to C60 (C60H2, C60H2O) and C42 (C42COO) fullerenes. Accordingly, fullerenes are attached to CNTs via either oxygen (preferable for fullerenes larger than C54) or carboxylic (for smaller fullerenes) bridges, which was confirmed by FT-IR measurements. EELS observations with TEM also showed the existence of oxygen. Scanning tunneling microscopy (STM) and spectroscopy (STS) measurements of samples deposited on Au(111) substrate confirmed the covalent nature of fullerene bonding to the tube. Atomistic density-functional-theory based calculations showed that systems composed of fullerenes and nanotubes with single vacancies covalently functionalized through ester groups can indeed exist. In-situ deposited i.e. non-purified planar NanoBud mats showed stable cold electron field emission with a current density of 189 µA/cm2 at 1.26 V/µm. The threshold voltage was about 0.6 V/µm, compared to over 2 V/µm for similarly produced planar nanotube mats. 1.A. G. Nasibulin, P. V. Pikhitsa, H. Jiang, D. P. Brown, A. V. Krasheninnikov, A. S. Anisimov, P. Queipo, A. Moisala, D. Gonzalez, G. Lientschnig, A. Hassanien, S. D. Shandakov, G. Lolli, D. E. Resasco, M. Choi, D. Tománek, and E. I. Kauppinen, (2007) A Novel Hybrid Nanomaterial, Nature Nanotechnology 2(3), 156-161.
12:30 PM - II7.3
Electronic Structure of Boron-Doped Carbon Nanotube.
Takashi Koretsune 1 , Susumu Saito 1
1 Department of Physics, Tokyo Institute of Technology, Tokyo Japan
Show AbstractBoron doping into carbon materials attracts much attention ever since the discovery of superconductivity in heavily boron-doped diamond. In the case of carbon nanotubes, on the other hand, it is well known that their electronic transport properties depend strongly on the radius and chirality. Therefore, effects of boron doping should be much more complicated and have not been well understood yet. We systematically study the energetics, electronic structure, and geometries of boron-doped zig-zag carbon nanotubes in the framework of the density-functional theory.Interesingly, from the total energies obtained after the geometry optimization, it is found that the energy cost of doping the B atom substitutionally into the isolated carbon nanotube is smaller for thin nanotubes. In the case of the (10,0) nanotube which is a moderate-gap semiconductor, the electronic structure of the 0.8 at% B-doped case is found to possess the hole-doped valence band. However, the Fermi level is already off the peak of the density of states. Therefore, less doped material should have higher Fermi-level density of states and be more interesting from the viewpoint of superconductivity etc. This is in sharp contrast to B-doped diamond. We also discuss the effect of the intertube interaction on the electronic structure of B-doped multi-wall carbon nanotubes as well as those in the crystalline bundles of B-doped nanotubes.
12:45 PM - II7.4
Transport Properties of Doped Carbon Nanotubes: Effect of Organic Molecules Encapsulation.
Rodion Belosludov 1 , Sang Lee 1 , Hiroshi Mizuseki 1 , Taishi Takenobu 1 , Yoshihiro Iwasa 1 , Yoshiyuki Kawazoe 1
1 Institute for Materials Research, Tohoku University, Sendai, Miyagi, Japan
Show AbstractRecently, the properties of carbon nanotubes (CNTs) have been the subject of much scientific attention from the viewpoint of their various applications in future nanoscale devices. However, there are some limitations to using these materials. For example, the realization of the CNT interconnections between electronic devices is a complicated problem because the separation of metallic and semiconducting CNTs is still a significant challenge for experimentalists. The important problem for carbon nanotube field-effect transistors (CNT-FETs) is stable control of polarity in FETs. This control is applicable in electronic devices such as complementary metal-oxide semiconductor CMOS based logic circuits. These problems can, most likely, be solved by doping CNTs. Recently, the single-wall carbon nanotube (SWNT) doping with different organic molecules has been reported experimentally [1], exemplifying the importance of estimating the electronic and conductance properties of doped SWNTs.Density functional theory and nonequilibrium Green’s function approaches have been used for the investigation of the electronic and transport properties of organic doped carbon nanotubes. The encapsulation effect of several organic molecules such as tetracyano-p-quinodimethane (TCNQ), anthracene, and tetrakis(dimethylamino)ethylene (TDEA) on electronic and transport properties of carbon nanotubes have been investigated. In order to obtain experimentally realizable results, the intercalation density of organic molecules was chosen as such: molecule/C140 in the case of the metallic (10,10) and molecule/C136 in the case of the semiconducting (17,0) SWNT. The favorable intercalation of TCNQ and TDAE is associated with charge transfer between the carbon nanotube and organic molecules.The conductivity of semiconductor SWNTs varies with n- and p-type doping, and a shift of the conductance peaks to the right and left of the Fermi level, respectively, has been observed. In the case of p-doping, the transport characteristics of both (10,10) and (17,0) SWNT remain similar to those of the undoped SWNT. However, in the case of n-doping, the calculated I/V curves show that organic molecules, especially TDAE, do not affect the conductance through metallic (10,10) SWNTs, but do significantly increase the conductivity through the semiconductor (17,0) SWNTs. The results indicate, in particular, the following three possibilities: enhancing the metallic features of carbon nanotube mixtures while avoiding complicated separation processes, realizing complex electronic devices such as p-n junctions based on SWNTs doped by different types of molecules, and controlling these devices’ characteristics by varying the concentration of the dopant. REFERENCES[1] T. Takenobu et al. Nature Materials 2 (2003) 683.
II8: Non-carbon Nanostructures II
Session Chairs
Kenji Hata
Annick Loiseau
Yoke Khin Yap
Ming Zheng
Tuesday PM, November 27, 2007
Room 312 (Hynes)
2:30 PM - **II8.1
BN Nanotubes, Synthesis, Properties and their Polymer Composites.
Chunyi Zhi 1 , Yoshio Bando 1 , Dmitri Golberg 1 , Chengchun Tang 1
1 , National Institute for materials sciences, Japan, Tsukuba, Ibaraki, Japan
Show AbstractA boron nitride nanotube (BNNT) is a structural analog of a carbon nanotube (CNT) in which alternating B and N atoms entirely substitute for C atoms in a honeycomb lattice. BNNTs are an intriguing nanoscale material. For instance, in spite of the fact that BNNT is an electrical insulator with a 5.5 eV band gap its electrical response can be tuned by doping or deformation. BNNTs have also shown piezoelectric behavior. In addition, BNNTs may find interesting uses in polymeric composites, with potential to rival or even surpass CNTs due to their superior thermal and chemical stabilities, straight shapes, superb rigidity and elasticity. Large scale BNNTs were synthesized using a chemical vapor deposition method using boron and metal oxide as reactants. Systematical property investigations were performed based on BNNTs with high quality. Recently, Individual multiwalled BNNTs were bent inside a transmission electron microscope (TEM) using a new fully integrated TEM - atomic force microscope (AFM) piezo-driven holder under continuous recording of force – piezo-displacements curves. The tubes were gently compressed in-situ between a piezo-movable aluminum wire and a silicon cantilever. Typically, bending stress values ranging from ~100 to ~260 MPa, and corresponding to elastic moduli of 0.5-0.6 TPa, were estimated. Tube gross failures were absent up to very large bending angles. The kinks were found to be entirely reversible on reloading with no (or marginal) traces of residual plastic deformation. Various methods were developed to functionalize BNNTs for better solubility and processability. For the first time, BNNTs were perfectly dispersed in various organic solvents by wrapping them with a polymer or due to covalent functionalization. Moreover, the biology applications of BNNTs were also explored by immobilizing various proteins on BNNTs; and peeled BNNTs and BNNT Y-junctions were obtained through chemical reaction in DMSO. Recently, for the first time, a gel suspension was fabricated with BNNTs and ILs. A new phase and ordering were found to be induced by BNNT introduction into the gels. A “green”, rapid chemical functionalization method was developed utilizing the BNNTs/ILs gels. By this method, a long alkyl chain can be connected to a BNNT surface at room temperature via a SN2 nucleophilic substitution reaction catalyzed by a strong Lewis acid. Polymer/BNNT composites were fabricated by solution method. With 1 wt.% BNNTs fraction, the elastic modulus of polystyrene can be increased 21 %. PmPV were found can improve not only the dispersion of BNNTs, but also increase the interaction between polymer and BNNTs. For other polymers, such as polyamide, around 100% increase in elastic modulus can be obtained with 5 wt.% BNNTs fraction. The investigations to thermal properties of composites, such as improvement of thermal conductivity, are still underway.
3:00 PM - II8.2
Effective Catalysts for Low Temperature Growth of Boron Nitride Nanotubes.
Jiesheng Wang 1 , Ming Xie 1 , Yoke Khin Yap 1
1 , Michigan Technological University, Houghton, Michigan, United States
Show AbstractBoron nitride nanotubes (BNNTs) are promising nanostuctures that will complement the applications of carbon nanotubes (CNTs) in various emerging areas. BNNTs have uniform electronic properties that are insensitive to their diameters and chiralities. Their wide bandgaps (~5eV) can also be tunable by doping or transverse electric fields. In addition, BNNTs have excellent piezoelectricity and high resistance to oxidation making them unique for applications that can not be met by CNTs. However, the synthesis of BNNTs is still challenging and required high growth temperatures (1100°C to 3000°C). The as grown products are usually predominated with impurities. We have reported on the growth of pure BNNTs at 600°C by a plasma-enhanced pulsed-laser deposition (PE-PLD) technique [1, 2]. For the first time, these BNNTs were grown vertically-aligned on substrates without residual catalyst particles on the BNNTs. Although a VLS mechanism was proposed for the growth, a lot of details are remained to be understood. For examples, what are the most effective catalysts for this low temperature growth process? What are the roles of the growth temperatures, and plasma configurations? All these details have been recently defined in a series of systematic investigation. The possible effects of plasma heating, sputter yields of the catalyst, resputtering rates of the BN deposits, etc. have been identified and leading to a better understanding on the growth mechanism. At optimum growth conditions, pure BNNTs with high structural order were successfully grown. UV Raman Spectroscopy demonstrates a strong signal at 1372 cm-1, which corresponds to the E2g mode of the hexagonal BN networks of the BNNTs. The effect of catalyst, growth temperatures, ambient gas pressures, substrate bias voltages and the growth mechanism will be discussed in the meeting.This work is supported by National Science Foundation CAREER award (Award No. 0447555, Division of Materials Research) and the Center for Nanophase Materials Sciences sponsored by the Division of Materials Sciences and Engineering, U.S. Department of Energy (Contract No DE-AC05-00OR22725).[1]. J. Wang et. al, Nano Letts. 5, 2528 (2005).[2]. Materials Today Vol. 9 (no 1-2), page 9, Jan-Feb 2006.
3:30 PM - II8: NCarbon-2
BREAK
II9: Optical Spectroscopy II
Session Chairs
Kenji Hata
Annick Loiseau
Yoke Khin Yap
Ming Zheng
Tuesday PM, November 27, 2007
Room 312 (Hynes)
4:00 PM - **II9.1
Optical Spectroscopy of Individual Carbon Nanotubes.
Tony Heinz 1
1 Depts. of Physics and Electrical Engineering, Columbia University, New York, NY, New York, United States
Show AbstractIn this paper we describe recent investigations of individual single-walled carbon nanotubes (SWNTs) using Rayleigh and Raman scattering techniques. The experiments were performed using isolated SWNTs grown over a slit by chemical vapor deposition. Individual nanotubes were probed with a broadband supercontinuum source for Rayleigh (elastic) light scattering and with a monochromatic laser excitation for Raman spectroscopy.
We present results of a study in which the nanotube electronic transitions were measured by Rayleigh scattering on individual nanotubes with chiral indices that independently identified by electron diffraction [1]. In this fashion, we could directly verify the essential trends of transition energies that were used in making earlier optical assignments of different structures. Single nanotube optical spectroscopy also provides an excellent means of examining the effects of perturbations on the electronic structure of specific SWNTs. We illustrate these possibilities with two studies. We examine the influence of local changes in the environment by comparing electronic spectra of isolated individual nanotube with their spectra when bundled with a second nanotube [2].
The controlled environment of suspended individual nanotubes has also been exploited to examine broadening of SWNT phonon spectra as observed in Raman scattering. For metallic nanotubes, identified independently by Rayleigh measurements, strong line broadening of the G-mode feature is seen, as in earlier reports. This effect arises from electron-phonon coupling and is shown to be modified by changing the nanotube Fermi energy through electrostatic gating [3].
These studies were carried out in collaboration with the research groups of Profs. Louis Brus, Jim Hone, and Stephen O’Brien at Columbia. Structural analysis of individual nanotubes by electron diffraction was performed by Dr. Yimei Zhu’s group at Brookhaven National Lab.
[1] M. Y. Sfeir et al., Science 312, 554 (2006).
[2] F. Wang et al., Phys. Rev. Lett. 96, 167401 (2006).
[3] Y. Wu et al., Phys. Rev. Lett. 99, 027402 (2007).
4:30 PM - **II9.2
Resonance Raman Scattering in Carbon Nanostructures.
Marcos Pimenta 1
1 Departamento de Fisica, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
Show Abstract5:00 PM - II9.3
Polarized Raman and Photoluminescence Characterization of Vertically Aligned Single-Walled Carbon Nanotubes.
Shigeo Maruyama 1 , Zhengyi Zhang 1 , Yuhei Miyauchi 1 , Rong Xiang 1 , Erik Einarsson 1
1 Department of Mechanical Engineering, The University of Tokyo, Tokyo Japan
Show AbstractPolarized Raman and photoluminescence studies were employed to characterize vertically aligned single-walled carbon nanotubes (VA-SWNTs) synthesized by the alcohol catalytic CVD (ACCVD) method [1,2]. The high-purity VA-SWNT film with average nanotube diameter of 2 nm can be grown up to 30 μm with in-situ observation of film thickness [3]. When the film is excited from the top surface, we found several strong RBM peaks, i.e. a peak at 180 cm-1 for 488 nm excitation, are distinguishing feature of VA-SWNTs. In our previous polarized Raman studies, we found these peaks are strong for incident light polarized perpendicular to the tube growth direction but diminishes when incident light is polarized parallel to the tube growth direction [4]. We concluded that we are observing cross-polarized excitation. However, recent higher-resolution Raman measurements reveal that some of these peaks are composed of several separate fine peaks. Also, this strong peak disappears when the VA-SWNT film is dispersed. With our recent findings that our film is composed of small bundles [5], typically 5-8 nanotubes, the distinguishing Raman feature is further examined by updated polarized Raman measurements. Given the Z-direction to be defined as parallel to the SWNT axis (growth direction), both incident and scattered light propagate along the Y-direction. After testing Y(ZZ)Y, Y(ZX)Y, Y(XX)Y, and Y(XZ)Y configurations, it was found that the RBM peaks are much stronger in the Y(XX)Y configuration (when the incident light and scattered light are perpendicular to the tube axis) than in the Y(ZZ)Y configuration. Also, the peak intensities are suppressed dramatically for the cross-polarized case, Y(XZ)Y, which is quite different from the previously well accepted result that optical spectra are dominated by absorption/emission of light polarized parallel to the tube axis, known as the antenna effect. On the other hand, G-band is much stronger for Y(ZZ)Y configuration compared with Y(XX)Y configuration. Hence, the intensity ratio between the RBM mode and G band is also larger in the Y(XX)Y case than any other configuration. We can also identify a decomposed component of G-band which is only observed for Y(ZZ)Y configuration. Higher order Raman signal such as 2D, 2G, G+2D, 3G, 4D, 2G+2D... are observed from this VA-SWNT film with the typical photoluminescence measurement setup using Xe lamp excitation. These higher order Raman scatterings are resonant with exciton E11 energy and overlapped to the photoluminescence signal. A VA-SWNT film made of 13C isotopes synthesized by our improved ACCVD condition is used to clarify these overlapped features.References: [1] Y. Murakami et al, Chem. Phys. Lett., (2004), 385, 298.[2] Y. Murakami et al., Phys. Rev. Lett., (2005), 94, 087402.[3] S. Maruyama et al., Chem. Phys. Lett., (2005), 403, 320.[4] Y. Murakami et al., Phys. Rev. B, (2005), 71, 085403.[5] E. Einarsson et al., J. Phys. Chem. B, (2007), submitted.
5:15 PM - II9.4
Curvature Effects on the Energy Dispersion of the G’ Band in Double-walled Nanotubes and Bilayer Graphene.
Alfonso Reina 1 , Eduardo Barros 2 , Federico Villalpando 1 , Riichiro Saito 2 , Jing Kong 3 , M. Dresselhaus 3 4
1 Materials Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Physics, Tohoko University, Sendai Japan, 3 Electrical Engineering and Computer Science, Massachusets Institute of Technology, Cambridge, Massachusetts, United States, 4 Physics, Massachusets Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractThe energy dispersion of the G’ band that appears in the Raman spectrum of double-walled carbon nanotubes (DWNTs) and bilayer graphene (BG) was obtained experimentally. The G’ band composes of four peaks in both cases. A higher frequency separation was observed between the highest and the lowest frequency peaks in the DWNT system. (up to ~10 cm-1 difference). On the other hand, a higher splitting between the two conduction bands was observed in BG comparing to DWNTs (greater by up to 300 meV). The effects observed can be explained by the role of curvature in DWNTs affecting the electronic and phonon dispersion relations in these carbon systems.
5:30 PM - II9.5
Length-Dependent Optical Properties of Single-Walled Carbon Nanotubes.
Jeff Simpson 3 , Jeffrey Fagan 3 , Barry Bauer 3 , Matthew Becker 3 , Erik Hobbie 3 , Angela Hight Walker 3
3 , National Institute of Standards and Technology, Gaithersburg, Maryland, United States
Show Abstract5:45 PM - II9.6
Elusive Fluorescence from Double-walled Carbon Nanotubes: New Experimental Approaches and Results.
Dmitri Tsyboulski 1 2 , Ye Hou 3 , Nikta Fakhri 4 2 , Matteo Pasquali 4 2 , Jie Liu 3 , R. Bruce Weisman 1 2
1 Department of Chemistry, Rice Universtiy, Houston, Texas, United States, 2 The Richard E. Smalley Institute for Nanoscale Science and Nanotechnology, Rice University, Houston, Texas, United States, 3 Department of Chemistry, Duke University, Durham, North Carolina, United States, 4 Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas, United States
Show AbstractFluorescence from double-walled carbon nanotubes (DWNTs) has become a controversial topic in current research. Some researchers believe that the outer nanotube with its substantially smaller band gap will serve as an energy acceptor and provide efficient quenching of inner nanotube fluorescence. Several experimental reports, however, indicate the opposite. In this study, a series of tests at the single-molecule level were performed to define similarities and differences between the emission centers present in aqueous suspensions of SWNTs and DWNTs. DWNTs were synthesized by carbon monoxide chemical vapor deposition (CO-CVD) method using binary catalysts Co/Mo supported on MgO. The nanotube product was first oxidized at 525 C in 20% air in Ar for 1 hour and then refluxed in 3 N HCl solution to obtain high purity DWNTs. HRTEM measurements showed inner and outer diameter distributions between 0.7-1.2 and 1.4-1.9 nm, respectively. We performed single-molecule near-IR fluorescence studies of the emitting centers from dispersed DWNT and SWNT samples and compared their photophysical properties. We found that the same semiconducting (n,m) species in both samples displayed nearly the same photoluminescence intensities, spectral line widths and peak positions. The sensitivity of SWNT and DWNT fluorescence to covalent functionalization with diazonium salt compounds in solution was examined. Similarly efficient quenching of fluorescence was found for SWNT and DWNT suspensions. Finally, we analyzed the thermally-induced bending motions of nanotubes with lengths greater than 4 µm to determine their persistence length parameters Lp. Since it is known from theory and experiment that Lp varies as the cube of nanotube diameter, a SWNT of given diameter will have a persistence length shorter by a factor of 5 to 9 than a DWNT containing the same inner tube. Examining the DWNT samples, we found that the persistence lengths of all fluorescent nanotubes analyzed to date are clearly characteristic of single-walled structures. The DWNT suspensions, however, do contain highly rigid extended structures that can be visualized with added conventional fluorophores. These structures displayed no near-IR emission. Our results indicate that the fluorescence signals from suspended DWNT samples arise from SWNT impurities rather than from the DWNT inner tubes. We note that this finding applies only to the one type of DWNT sample described above. However, we believe that the methods used in this study can be applied in the future to other DWNT samples to fully resolve the issue of DWNT inner-tube fluorescence.
II10: Poster Session: Theory and Characterization of Nanotubes and Related Nanostructures
Session Chairs
Kenji Hata
Annick Loiseau
Yoke Khin Yap
Ming Zheng
Wednesday AM, November 28, 2007
Exhibition Hall D (Hynes)
9:00 PM - II10.11
Effects of Covalent Functionalization on Photoelectrochemical Properties of Single-Walled Carbon Nanotube Clusters Electrophoretically Deposited on Semiconducting Electrodes.
Tomokazu Umeyama 1 , Mitsuru Fujita 1 , Noriyasu Tezuka 1 , Naoki Kadota 1 , Yoshihiro Matano 1 , Hiroshi Imahori 1
1 Graduate School of Engineering, Kyoto Univeristy, Kyoto Japan
Show AbstractOne-dimensional, nanowire-like structures of single-walled carbon nanotubes (SWNTs) are potential candidates as ideal nanohighways for efficient electron transport in photoelectrochemical devices consisting of donor-SWNT nanocomposites. In addition, individual SWNTs would afford large surface area at the donor-SWNT interface, which is favorable for efficient dissociation of exciton and prevention of self-quenching of excited SWNTs. However, incorporation of debundled SWNTs into photovoltaic systems has been hindered by their poor dispersibility in organic and aqueous solvents as a result of their strong intermolecular interaction between the individual SWNTs. In this study, bulky photoactive molecules (i.e., porphyrin) have been tethered to SWNTs to increase the dispersibility in organic solvents and then the composites have been deposited electrophoretically onto SnO2 electrodes to construct photoelectrochemical devices. This is the first example of photoelectrochemical systems in which porphyrins are covalently linked to SWNTs.The electrophoretically deposited film of SWNTs modified covalently with porphyrins at terminals and defect sites by amide linkage (NT-H2P) was photoactive and absorbs light in the visible and near-infrared regions efficiently. The incident photon-to-photocurrent efficiency (IPCE) of the device was as high as 4.0 % under an applied potential of 0.08 V vs SCE, which is larger than reference systems comprised of SWNTs modified with long alkyl (NT-Ref, IPCE = 2.3 %) or carboxyl (NT-CO2H, IPCE = 2.6 %) groups. Further enhancement of photocurrent generation was achieved when the sidewall of NT-H2P was also functionalized with in situ generated porphyrin diazonium compounds (H2P-NT-H2P, IPCE = 4.9 %). The more efficient photocurrent generation in the porphyrin-SWNT composite devices can be rationalized by the exfoliation abilities of the bulky porphyrins that yield more exfoliated SWNTs in the deposited films, which was confirmed by AFM and TEM measurements. In spite of efficient quenching of the porphyrin excited singlet state by the SWNTs in the porphyrin-linked SWNTs, the photocurrent action spectra revealed that the excitation of the porphyrin moieties makes no contribution to the photocurrent generation. Direct electron injection from the excited states of the SWNTs to the conduction band of the SnO2 electrode is responsible for the photocurrent generation. The evolution of exciplex between the porphyrin excited singlet state and the SWNTs and the subsequent rapid decay to the ground state without generating the charge-separated state is proposed to explain the unusual photoelectrochemical behavior.[1] Umeyama, T.; Fujita, M.; Tezuka, N.; Kadota, N.; Matano, Y.; Yoshida, K.; Isoda, S.; Imahori, H. J. Phys. Chem. C, in press; [2] Umeyama, T.; Tezuka, N.; Fujita, M.; Matano, Y.; Takeda, N.; Murakoshi, K.; Yoshida, K.; Isoda, S.; Imahori, H. J. Phys. Chem. C, in press.
9:00 PM - II10.13
Highly Stable and Luminescent Single-Wall Carbon Nanotubes SWNT)in Acidic Environment.
Juan Duque 1 3 , Cognet Laurent 2 3 4 , Nicholas Parra-Vasquez 1 3 , Nolan Nicholas 2 3 , Howard Schmidt 3 , Matteo Pasquali 1 2 3
1 Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas, United States, 3 Carbon Nanotechnology Laboratory, The Smalley Institute for Nanoscale Science & Technology, Rice University, Houston, Texas, United States, 2 Department of Chemistry, Rice University, Houston, Texas, United States, 4 Centre de Physique Moléculaire Optique et Hertzienne, Université Bordeaux, Talence France
Show AbstractAqueous suspensions of single-walled carbon nanotubes (SWNT) in the anionic surfactants sodium dodecyl benzenesulfonate (SDBS) and sodium dodecyl sulfate (SDS) readily undergo luminescence bleaching in acidic conditions, with faster bleaching rates for small band gap tubes. Here we show that when SWNT suspensions are prepared below neutral conditions in a mixture of anionic surfactant and polymer (SDBS and poly(vinylpyrrolidone), PVP), the luminescence of all SWNT species is enhanced. These suspensions remain highly luminescent at pH 1 and are stable for weeks, as evidenced by fluorescence and UV absorbance. Cryo-TEM and AFM images obtained both in neutral and acidic conditions corroborate spectroscopic observations made by Raman and single nanotube luminescence microscopy, which indicates that SWNT are suspended as individuals. The mechanism of luminescence enhancement is studied using time lapse measurements at pH 2. After acidification, the system undergoes a fast process in which the PVP becomes protonated while behaving as a buffer between the acid and the tubes. Protonation of PVP induces swelling which increases the interstitial spacing and allows the tubes to behave more independently. Stable and highly luminescent SWNT suspensions in acidic media will allow scientists to study the behavior and properties of tubes in such environments where the spectroscopic signatures would otherwise not be present.
9:00 PM - II10.14
Structure-Dependent Electric Field Effects on Single-Walled Carbon Nanotube Photoluminescence.
Anton Naumov 1 , Dmitri Tsyboulski 2 , Sergei Bachilo 2 , R. Bruce Weisman 2
1 Applied Physics, Rice University, Houston, Texas, United States, 2 Chemistry, Rice University, Houston, Texas, United States
Show AbstractAn experimental investigation of the fluorescence emission of single-walled carbon nanotubes (SWNTs) in electric fields will be described. In a series of experiments, HiPco SWNTs were embedded in poly(methylmetacrylate) (PMMA) and deposited as a polymeric film onto the surface of microscope slides equipped with gold or ITO electrodes. The fluorescence of individual semiconducting SWNTs was observed using an inverted Nikon microscope coupled to a near-IR spectrograph with InGaAs detector, and an InGaAs 2-D camera. Bulk samples of SWNTs in polymer were studied with a scanning spectrofluorometer. Our previous studies showed that when SWNTs in PMMA are subjected to electric fields of up to 10 V/μm, a drastic decrease in their fluorescence intensity is observed. This fluorescence quenching is well described as an inverse hyperbolic cosine function of applied field, with a single quenching efficiency parameter typically found to be 0.1 to 1.0 μm/V. The quenching phenomenon may be related to exciton dissociation and free carrier quenching in the presence of an electric field. Fluorescence quenching is induced by the electric field component parallel to the SWNT axis, while the perpendicular component does not produce detectable quenching. Accordingly, the quenching coefficient is found to vary as the cosine of the angle between the SWNT axis and the direction of the electric field. Such behavior, which is observed for both multiple and individual nanotubes, agrees with the theoretical models mentioned above. Nanotube length was also found to have a strong impact on field-induced fluorescence quenching. The quenching is enhanced for long nanotubes. In studies of bulk samples, a strong dependence of SWNT photoluminescence quenching on optical band gap was uncovered. It was found that the quenching efficiency increases with SWNT diameter and decreases as the band gap increases. This dependence may provide a useful experimental route to deduce exciton binding energies. Finally, the temperature dependence of field-induced quenching effect will be described and interpreted in terms of the underlying mechanism.
9:00 PM - II10.15
Direct Imaging of Percolative Paths in Carbon Nanotube Thin Film Transistors in Photoelectron Emission Microscope.
Vinod Sangwan 1 2 , Vincent Ballarotto 2 , Michael Fuhrer 1 , Ellen Williams 1 2
1 Department of Physics, University of Maryland, College Park, Maryland, United States, 2 , Laboratory for Physical Sciences, College Park, Maryland, United States
Show Abstract9:00 PM - II10.16
Structural and Electrochemical Characterization of Catalysts Using Carbon Nanofilaments as Support.
Petra Bele 1 , Alexander Racz 1 , Ulrich Stimming 1
1 Department of Physics E19, Technische Universität München, Garching Germany
Show Abstract9:00 PM - II10.17
Damping Characteristics of Double-walled Carbon Nanotube Oscillators.
Y. Ooi 1 , K. Shintani 1
1 Department of Mechanical Engineering and Intelligent Systems, University of Electro-Communications, Chofu, Tokyo, Japan
Show AbstractCarbon nanotubes (CNTs) will be applicable to functional mechanical devices such as bearings, actuators, sliders, oscillators, etc., in nano-electro-mechanical systems. Double-walled nanotubes (DWNTs) especially attract one's attention because it was reported that the inner and outer shells of DWNTs can move relatively and oscillate translationally in the axial direction and that the frequencies of such oscillations are of the order of several 10 GHz. It was also found that the attenuation constant depends on the tube length and temperature. In this study, we investigate by molecular-dynamics simulation how the oscillatory behavior of DWNTs is affected by their geometrical parameters, viz., diameter and length. For simplicity, both the inner and outer shells of our model DWNTs have such chiral indices of armchair nanotubes as (4,4)/(9,9), (5,5)/(10,10), (6,6)/(11,11), and (7,7)/(12,12). The length of all these DWNTs is 5nm. In addtion, another (5,5)/(10,10) DWNT is 8nm in length. The space between the inner and outer tubes is 0.344nm. The intertube interaction is calculated by using the Tersoff-Brenner potential. On the other hand, the intratube interation is calculated by the Lennard-Jones potential. The inner shell is initially extracted by 45% of the total tube length from inside the outer shell. If the inner shell is released with no velocity, the translational oscillation begins. This oscillation is damped owing to energy dissipation; the kinetic energy of the translational movement is transformed into the kinetic energy corresponding to the intratube temperature. We calculate the frequencies and logarithmic decrements of the damped oscillations of the model DWNTs. It is shown that the logarithmic decrement exponentially increases with increasing the tube diameter and decreases with increasing the tube length.
9:00 PM - II10.18
van der Waals - London Dispersion Interactions For Metallic and Semiconducting Carbon Nanotubes From ab initio, Unixial Optical Properties.
Rick Rajter 1 , Roger French 2
1 DMSE, MIT, Boston, Massachusetts, United States, 2 Central Research, Dupont, Wilmington, Delaware, United States
Show AbstractAs the drive towards nanoscale assembly continues, the need to understand all the fundamental forces becomes increasingly important for the purpose of success from properly designed experiments. The van der Waals - London dispersion (vdW-Ld) interaction are the universal long range interaction and their calculations often appear impractical because of the current lack of full spectral optical properties along with the proper geometrical formulation that are necessary for meaningful results. These obstacles are removed through 1. the use of ab initio full spectral, uniaxial, optical properties calculated from electronic structure calculations, and 2. with extensions of the Lifshitz formulation to more complex geometrically and optically anisotropic configurations. These new abilities are of broad utility, especially in the biological community because of the difficulty in experimental determination of full spectral optical properties of nanoscale, liquid phase biomolecules. Here we demonstrate 3 levels of complexity of vdW-Ld interactions (optically isotropic planar, optically anisotropic planar, and optically anisotropic solid cylinder(1)) as well as calculate and compare a variety of Hamaker coefficients relevant for these systems. For the two more complex cases, anisotropic substrates and anisotropic cylinders, we use the ab initio optical properties of semiconducting and metallic single wall carbon nanotubes. Our results show the effects of strong anisotropy upon the overall vdW-Ld interaction strength as well as the presence of strong dispersion-driven torques in both anisotropic cases, which can play a role in mutual CNT alignment with other CNTs and also preferred alignment directions upon anisotropic substrates.1. R. Rajter, R. Podgornik, V. A. Parsegian, R. H. French, W. Y. Ching, accepted and awaiting publication in Phys. Rev. B.
9:00 PM - II10.19
Current-driven Nanofluidic Propellers with Chemically Tunable Blades.
Lela Vukovic 1 , Petr Kral 1 , Boyang Wang 1
1 Chemistry, University of Illinois at Chicago, Chicago, Illinois, United States
Show Abstract9:00 PM - II10.2
Qualitative Raman Characterization of Single-Walled Carbon Nanotube Soot.
Jeungchoon Goak 1 , Jong Hun Han 2 , Naesung Lee 1
1 Faculty of Nanotechnology and Advanced Materials Engineering, Sejong University, Seoul Korea (the Republic of), 2 NT based Information & Energy Storage Research Center, Korea Electronics Technology, Gyeonggi Korea (the Republic of)
Show AbstractArc discharge technique is a potential candidate for the large-scale production of single-walled carbon nanotubes (SWCNTs) with excellent quality among many synthesis techniques. However, SWCNTs soot produced contains a significant amount of carbonaceous nanoparticles and metal catalysts mainly encapsulated with graphitic nanoparticles. Depending on the production method, the purity of as-produced SWCNTs ranges from 10 to 70%, which is simply assessed by different specific metrics. There are several qualitative and quantitative techniques used to characterize the properties of SWCNT-including samples, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis-NIR spectroscopy, thermogravimetric analysis (TGA), Raman spectroscopy, etc. Various information has been extracted from the portion of interest in a sample by using these tools. For example, TEM and SEM are not suitable due to an extremely limited amount, around 10-12 g, of sample evaluated, but provide a visual confirmation of SWCNTs. The content of metal has been verified with TGA, but the amount of carbonaceous constituents is difficult to be determined. In contrast, optical absorption spectroscopy can enable a quantitative analysis by comparing and measuring the electronic transition of non-SWCNTs and SWCNTs in a low concentration of a homogeneous CNT solution. Therefore, such analytical metrics can be employed to delineate the properties of all constituents in combination rather than in individual. Raman spectroscopy is a simple, fast, and non-destructive technique to determine the diameters and electronic types of individual SWCNTs. Additionally, the peak intensity ratio of the D- and G-band can be used as a means to quantify the relative SWCNT fraction and to resultantly evaluate the efficiency of purification. In this study, SWCNT soot produced by arc discharge was analyzed in a powder form by using Raman spectroscopy. To make a reliable ratio of peak intensity of SWCNT-containing sample, inhomogeneous SWCNT soot was subject to ultrasonic homogenizing in ethanol. The homogeneously mixed soot was checked in five independent regions to obtain a mean value and a standard deviation. Temperature controlled thermal oxidation (TTO) to monitor the efficiency of the purification was conducted at incremental temperature interval, where, supported by Raman spectroscopy, the intensity ratio of D- and G-band was exponentially reduced at higher oxidation temperatures. We also investigated the peak position, line width, and relative intensity of D, G-, and G+ for a series of oxidized samples. Conclusively, a ratio of peak intensity of G- and G+ seems to offer much information during thermal oxidation, compared to the intensity ratio of D- and G-band. Other technical tools such as TGA are necessarily engaged as well, to validate the techniques and to ensure material assessment based on Raman spectroscopy.
9:00 PM - II10.20
General Elasticity Theory for Graphene Membranes Based on Molecular Dynamics.
Kaveh Samadikhah 1 , Juan Atalaya 1 , Caroline Huldt 1 , Andreas Isacsson 1 , Jari Kinaret 1
1 Department of Applied Physics, Chalmers University of Technology, Gothenburg Sweden
Show AbstractWe have studied the mechanical properties of a suspended graphene membrane using molecular dynamics (MD) and generalized continuum elasticity theory (GE). The MD simulations are based on a valence force field model which is used to determine the deformation and the elastic energy of the membrane (EMD) as a function of external forces. For the continuum description we use the expression Εcont = Estretching[ε] + Ebending[κ,Η], for the elastic energy functional. Here, ε is the strain tensor while κ and Η are the Gaussian and mean curvatures. The elastic parameters (tensile rigidity, Poisson ratio and bending rigidity) entering Εcont are determined by requiring that Εcont = EMD for a set of deformations.We solve the nonlinear equations derived from the GE theory (von Karman equations for large deflections of thin plates) to obtain the equilibrium shape of the membrane. Comparisons with the MD results show excellent agreement. We find that the elastic energy of clamped graphene sheets is typically dominated by the nonlinear stretching terms whereas a linear description is valid when the bending energy dominates or when the stresses are uniform. This implies that in some applications, e.g. NEMS, the linear description may be of limited applicability.
9:00 PM - II10.21
Emulsion Stabilization with Single-Walled Carbon Nanotubes.
Kirk Ziegler 1 , Randy Wang 1 , Ryan Reeves 1
1 Department of Chemical Engineering, University of Florida, Gainesville, Florida, United States
Show AbstractSingle-walled carbon nanotubes (SWNTs) have excited researchers for several years because of their unique physical and chemical properties, which can be used in microelectronic and biomedical applications. However, most SWNT synthesis techniques result in polydisperse lengths. Chromatographic or electrophoretic separations have been successful but are typically limited to analytical scale separations. Recently, a bulk-scale liquid-liquid extraction process was developed for the separation of SWNTs by length. The separation was attributed to the length-dependent van der Waals attractions of SWNTs. These separations, however, often had difficulties with the formation of stabilized emulsions. To further understand the stabilization of emulsions with nanotubes, we have studied the interfacial interactions of a simpler system – surfactant suspended SWNT solutions. A simple model has been developed to characterize the free energy changes upon movement of nanotubes from the aqueous phase to the interface. This model predicts that longer nanotubes preferentially adsorb to the interface and that oil-in-water emulsion systems are stabilized by hydrophilic particles.
9:00 PM - II10.22
Structures of `all surface' KI and CsI Nanocrystals Grown within Single-walled Carbon Nanotubes.
Elena Bichoutskaia 2 , Nicholas Pyper 3 , John Harding 1
2 Chemistry, University of Nottingham, Nottingham United Kingdom, 3 University Chemical Laboratory, University of Cambridge, Cambridge United Kingdom, 1 Engineering Materials, University of Sheffield, Sheffield United Kingdom
Show Abstract9:00 PM - II10.23
Density Functional Theory Study of DNA/RNA Nucleobases Interacting with Carbon Nanotubes in the Low- and High-Curvature Limit.
Ralph Scheicher 1 , S. Gowtham 1 , Ravi Pandey 1 , Shashi Karna 2
1 Physics, Michigan Technological University, Houghton, Michigan, United States, 2 , US Army Research Laboratory, Aberdeen Proving Ground, Maryland, United States
Show AbstractWe report the results of our first-principles investigation on the interaction of the nucleobases adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U) with both graphene and with a (5,0) zigzag carbon nanotube (CNT). Graphene is used in our study as a model system for the low-curvature limit of CNTs with very large diameter, while the (5,0) tube with a diameter of merely 0.392 nm is representing the high-curvature limit. In the present study, we employed density functional theory (DFT) within the local density approximation (LDA) and for comparison also Hartree-Fock plus second-order Moller-Plesset perturbation theory (HF+MP2). We find that LDA is suitable to determine the equilibrium geometry in this van der Waals bound system. However, compared to HF+MP2, the binding energy may be underestimated by 40-60%. Our results show that the nucleobases can exhibit significantly different interaction strengths when physisorbed either on graphene or on the surface of a (5,0) CNT. The calculated binding energies of the nucleobases follow the hierarchy: G > A > T > C > U. The stabilizing factor in the interaction is clearly dominated by the molecular polarizability of the nucleobases which gives rise to a weakly attractive dispersion force. Regarding the equilibrium geometry, we find that the high curvature of the (5,0) CNT allows the base molecules to bind at a smaller vertical distance from the surface than it is the case for graphene. The present study is part of a larger project which aims towards a first-principles understanding of how the base sequence of DNA affects its interaction with CNTs, as observed experimentally. This work is partially supported by DARPA.
9:00 PM - II10.24
Density Functional Study of Hydrogen Adsorption in Nitrogen Doped Defective Single-Walled Carbon Nanotubes.
SambasivaRao Rupenaguntla 1 , Prasad Matukumilli 2
1 Dept. of Chemistry, Andhra University, Visakhapatnam, Andhra Pradesh, India, 2 Dept. of Mechanical Engg., Andhra University, visakhapatnam, Andhra Pradesh, India
Show Abstract9:00 PM - II10.26
ESR Studies on High-energy Ion Irradiated Carbon Nanotubes.
Ananta Adhikari 1 , Mengbing Huang 1 , Hassaram Bakhru 1 , Pulickel Ajayan 2 , Mircea Chipara 3
1 College of Nanoscale Science and Engineering, State University of New York, Albany, New York, United States, 2 Department of Material Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States, 3 University of Texas Pan America, Department of Physics and Geology, Edinburg, Texas, United States
Show AbstractThe effects of high-energy ion (Hydrogen, Helium or Neon) irradiation on single wall carbon nanotubes (SWNTs) are studied using electron spin resonance (ESR). Irradiation ions and doses were varied purposefully to introduce wide range of defects. The temperature dependence of ESR spectra in the range 25 K to 250 K was used to identify the components of the ESR spectra. The results revealed the generation of paramagnetic defects due to the ion bombardment. These data correlate with previous Raman and thermal investigations [1] on the same SWNTs and reveals their sensitivity to ionizing radiation. [1] A. R. Adhikari, M. B. Huang, H. Bakhru, R. Vajtai, C. Y. Ryu and P. M. Ajayan, Journal of Applied Physics 100 (2006) 064315.
9:00 PM - II10.27
Ar Beam Modification of Nanotube Based Composites Using Molecular Dynamics Simulations
Sharon Pregler 1 , Byeong Woo Jeong 1 , Susan Sinnott 1
1 , University of Florida, Gainesville, Florida, United States
Show AbstractIon-beam irradiation of polymers is a common approach to modify their mechanical properties. Here, Ar deposition on polystyrene-carbon nanotube composites is examined. The goals are to determine how subjecting these composites to Ar irradiation influences their surface structure and mechanical properties. The approach is classical molecular dynamics simulations using the reactive empirical bond-order potential to determine the interactions for short-ranged interactions, and the Lennard-Jones potential to determine the forces for long-ranged interactions. Three different composites were considered that consisted of a polystyrene matrix with a single-walled nanotube, double-walled nanotube, or single-walled nanotube bundle as the reinforcing fiber(s). The composites were irradiated with a beam of 100 Ar atoms, that had an incident energy of 80 eV/ion. The simulations predict that the Ar beam induced crosslinking between the nanotube and polymer and/or between neighboring nanotubes. Following irradiation, the nanotubes were pulled axially with respect to the polystyrene to determine the effects of crosslinking and polymer etching on the pullout forces. Stand-alone bundles of single-walled and double-walled nanotubes were also irradiated with Ar to examine the variation of irradiation-induced changes in bonding with the curvature and structure of the nanotubes. The results indicate that the pullout forces significantly increased as a result of irradiation-induced crosslinking. This work was supported by the National Science Foundation (CHE-0200838).
9:00 PM - II10.28
Molecular Dynamics Study of Electron Irradiation Damages in Carbon Nano-Materials.
Masaaki Yasuda 1 , Takashi Majima 1 , Yoshihisa Kimoto 1 , Kazuhiro Tada 1 , Hiroaki Kawata 1 , Yoshihiko Hirai 1
1 Physics & Electronics Eng., Osaka Prefecture University, Sakai Japan
Show AbstractIn the transmission electron microscope observation, irradiation damages in nano-materials become a serious problem. We have developed the molecular dynamics simulation including the interaction between an electron and a carbon atom to study the deformation process of carbon nano-materials under electron beam irradiation. The transferred energy from the electron to the carbon atom and the scattering angle of the carbon atom are determined based on the elastic scattering theory. The collision atom in the target materials is randomly selected. Tersoff-Brenner and Lennard-Jones potentials are used in the simulation to describe the short-range and long-range interactions among carbon atoms, respectively.We demonstrate the electron irradiation damages in carbon nano-materials such as single-walled carbon nanotube (SWNT), double-walled carbon nanotube and fullerene-encapsulated SWNT. Our simulation results show good agreement with those reported experimentally in the various conditions.This work was supported by the Grants-in-Aid for Scientific Research from the Japan Society for the Promotion of Science.
9:00 PM - II10.3
Resonance Raman Behaviour of Chemical and Electrochemical Doped Double-Wall-Carbon-Nanotubes.
Gustavo doNascimento 1 , Yoong Kim 3 , Morinobu Endo 3 , Noboru Akuzawa 4 , Mildred Dresselhaus 1 2
1 Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 , Faculty of Engineering, Shinshu University, Wakasato, Nagano-shi Japan, 4 Department of Chemical Science and Engineering , Tokyo National College of Technology, Tokyo Japan, 2 Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractDouble-wall carbon nanotubes (DWNTs) are an interesting material because they represent an intermediate structure between single-wall (SWNT) and multi-wall carbon nanotubes (MWNT). DWNTs are a prototype material for investigating interactions between two graphite layers. Resonance Raman scattering is the most commonly used technique used to probe the electronic levels of this class of materials, due to the possibility of selecting different electronic transitions by only changing the excitation laser line. Until now, there has been only a few investigations into the behavior of DWNTs using different excitation energies while simultaneously varying the applied electrical potential. Such an investigation is valuable in order to study the behaviour of the inner and outer tubes as a function of the potential at different excitation wavelengths, allowing us to better understand the interactions between the two walls. In this work we present the resonance Raman behaviour of DWNTs as a function of the applied potencial. Special attention was given to distinguish the behavior between S/M and M/S outer/inner semiconducting (S) and metallic (M) tubes. The results will be compared with those obtained for DWNTs chemically doped with bromine.G.M. do Nascimento acknowledges CNPq 202479/2006-4 (Brazilian Agencie) for the fellowship. This work was supported by NSF Grants DMR-04-05538 and DMR-07-04197.
9:00 PM - II10.30
Defects in Carbon Nanotubes.
Antonio daSilva 1 , Rodrigo Amorim 1 , Alexandre Rocha 1 , Alex Antonelli 2 , Adalberto Fazzio 1
1 Instituto de Física, Universidade de São Paulo, São Paulo, SP, Brazil, 2 Instituto de Física ‘‘Gleb Wataghin’’, UNICAMP, Campinas, SP, Brazil
Show AbstractPristine Carbon Nanotubes (CNTs) have exceptional mechanical and transport properties. It has been experimentally established, however, that defects in CNTs can alter in a dramatic way these properties. For example, upon irradiation the tubes in bundles have better mechanical properties [1] whereas isolated tubes have large changes in their conductivity [2]. In the former case, defects are believed to cause links between the tubes in the bundle [3], whereas in the latter di-vacancies seem to be the most prevalent defects created upon irradiation that can alter the charge transport properties. We investigate, using ab initio Density Functional Theory calculations: 1) the detailed nature and properties of defects that can connect tubes in bundles. In particular, we will present results for i) an interstitial carbon atom right besides a vacancy that can connect tubes in bundles [3]; ii) vacancies that can connect tubes in bundles. In particular, we investigate two different configurations, V12 and V22, which correspond to distinct arrangements of the vacancies in two nearest neighbor tubes; 2) similar defects are investigated for double-walled nanotubes. We will present results for formation energies, and barriers of formation and recombination of these defects. We compare these results with the graphite, and study how these defects can alter the mechanical properties; 3) the divacancy in single walled carbon nanotubes (SWNT). We study two distinct configurations, which have been labeled as 585 (two pentagons and one octagon) and 555-777 (three pentagons and three heptagons). The 585 has been recently used in theoretical studies of charge transport in SWNT [4]. However, as another recent investigation [5] has shown that the 555-777 has the lowest formation energy in graphenes, it is fundamental to study the behavior of these two defects in the SWNTs. We investigate how their formation energies change with the diameter and chirality, including the limit of infinite diameter (graphene). We also investigate how these defects affect the charge transport properties of armchair nanotubes using a Non-Equilibrium Greens Function formalism, both for isolated defects as well as for a randomly distributed arrangements in large nanotubes. This work was supported by the Brazilian agencies FAPESP and CNPq. We also would like to thank CENAPAD-SP for computer time.[1] A. Kis et al., Nature Mat. 3, 153 (2004).[2] C. Gomez-Navarro et al., Nature Mat. 4, 534 (2005).[3] See A. J. R. da Silva, A. Fazzio, and A. Antonelli, Nano Lett. 5, 1045 (2005) and references therein.[4] B. Biel et al., Phys. Rev. Lett. 95, 266801 (2005).[5] G.-D. Lee et al., Phys. Rev. Lett. 95, 205501 (2005).
9:00 PM - II10.31
Defect Healing of Carbon Nanotubes by Rapid Vacuum Arc Annealing.
Jeff Tsai 1 , Andy Tseng 1
1 Graduate Institute of Electro-Optical Engineering, Tatung University, Taipei Taiwan
Show Abstract9:00 PM - II10.32
How Do Coiled Carbon Nanotubes Break?
Vitor Coluci 1 , Alexandre Fonseca 2 , Chiara Daraio 3 , Istvan Laszlo 4 , Douglas Galvao 1
1 Applied Physics, State University of Campinas, Campinas Brazil, 2 , The University of Texas at Dallas, Dallas, Texas, United States, 3 Aeronautics & Applied Physics, California Institute of Technology , Pasadena, California, United States, 4 Department of Theoretical Physics, Budapest University of Technology and Economics, Budapest Hungary
Show AbstractCarbon nanotubes of helical shape, the so-called coiled carbon nanotubes (CCNT) were predicted to exist from molecular-dynamics simulations. The first experimental observation of coiled single walled carbon nanotubes (CSWNTs) was made by Biró et al. [1]using scanning tunneling microscopy. Recently, Daraio et al. [2] have shown that forests formed of coiled carbon nanotubes exhibits a strongly nonlinear, non-Hertzian-type contact interaction law, which could allow the design of strongly nonlinear phononic devices with tunable properties [2]. In order to better understand these experimental findings a more detailed investigation on the elastic properties of CCNT is necessary. In this work we present results from classical molecular dynamics simulations of the mechanical behavior of CSWNTs under tensile load.A tightly wound CSWCNT with length of 6.57 nm and diameter about 2 nm was used [3]. The interactions between carbon atoms were described by an adaptive intermolecular reactive empirical bond-order potential. This empirical potential is similar to Brenner-Tersoff kind, but it incorporates by suitable modifications the non-bonded interactions. This kind of reactive potentials has been proved to be accurate to describe carbon nanotube deformations under mechanical strain. For the molecular dynamics simulations the Newton's equations of motion were integrated with a third-order Nordisieck predictor corrector algorithm using a time step of 0.5 fs. We have carried out simulations of tensile tests in situations of impact load, i.e., the atoms on the CSWCNT extremities were moved along the axial directions with a speed of 10 m/s. In order to investigate thermal effects on the tensile behavior of CSWCNTs, the Berendsen's thermostat was applied to all remaining atoms. Tensile behaviors for two different temperatures (10 K and 300 K) were analyzed. We observed a linear regime form 0 to about 23 % of tensile strain. A spring constant of about 3.9 N/m was obtained for this regime for both temperatures. This regime is associated with the elastic deformation of the CSWNT. From 23% up to about 40% of tensile strain a plateau is present, suggestive of a plastic regime. We associated this regime with a structural transition of the CSWNT. In this case the nanotube undergoes a flattening process of its cross sectional area. After this limit a linear behavior was again observed. These structures exhibit a remarkable capability of deformation without breaking, total rupture of the CSWNT occurred at about 190% (T=10K) and 195% (T=300K). The mechanism of rupture and healing processes seem to be very distinct from the ones observed for standard carbon nanotubes.[1] L. P. Biro et al Europhys. Lett. 50, 494 (2000).[2] C. Daraio, F. F. Nesterenko, S. Jin, W. Wang, A. M. Rao, J. Appl. Phys. 100 064309 (2006).[3] I. Laszlo, A. Rassat, J. Chem. Inf. Comput. Sci. 43 519 (2003).
9:00 PM - II10.33
Mesoscopic Model for Simulations of Carbon Nanotube Nanocomposites.
Kiril Simov 1 , Elodie Leveugle 1 , Alexey Volkov 1 , Leonid Zhigilei 1 , Maxim Makeev 2 , Deepak Srivastava 2
1 Materials Science and Engineering, University of Virginia, Charlottesville, Virginia, United States, 2 Computational Nanotechnology, NASA Ames Research Center, Moffett Field, California, United States
Show Abstract9:00 PM - II10.34
Chaining Effect and Emerging Yield in Nanotube Suspensions under Electric Field.
Amir Farajian 1 , Olga Pupysheva 1 , Howard Schmidt 2 , Boris Yakobson 1
1 Mechanical Engineering and Materials Science, Rice University, Houston, Texas, United States, 2 Carbon Nanotechnology Laboratory, Rice University, Houston, Texas, United States
Show AbstractNanotube suspensions are shown to possess unique properties with novel applications in, e.g., liquid crystals and cancer therapy. The viscoelastic features of nanotube suspensions are known to change upon application of electric field. Here we model the electrostatic response of nanotube suspensions, and investigate the conditions which cause alignment and chaining of the nanotubes despite thermal agitations. The polarizations of the nanotubes are calculated using an exact numerical approach, within classical electrostatics, in which the nanotubes are modeled as solid rods with hemispherical ends. Calculating the surface charge densities, we derive the inter-nanotube forces and estimate the emerging yields. Our results are in good agreement with the experimental data, and can be used to control phase transitions in nanotube suspensions.
9:00 PM - II10.35
Schottky Barrier Heights in CNT-Metal Junctions from First-principles.
Nicholas Singh-Miller 1 , Nicola Marzari 1
1 Materials Science and Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractFundamental understanding of the electronic properties at the junction between a carbon nanotube (CNT) and a substrate or lead is important for the practical application of CNT-based devices. Here, we use density functional theory (DFT) to probe the properties of the CNT-metal interface, paying particular attention to the Schottky barrier heights (SBH). We focus on the junction between a semiconducting (8,0)CNT and aluminum or palladium, chosen as paradigmatic examples of a simple metal and a transition metal, respectively. We obtain SBHs from the potential lineup, examining the effects of geometry at the interface and the functionalization of the CNT on the SBH.
9:00 PM - II10.36
Formation of Carbon Nanotube Semiconductor-Metal Intramolecular Junctions by the Reconstruction of Vacancy Defects.
Gun-Do Lee 1 , Cai-Zhuang Wang 2 , Euijoon Yoon 1 , Nong-Moon Hwang 1 , Jaejun Yu 3 , Kai-Ming Ho 2
1 Materials Science and Engineering, Seoul National University, Seoul Korea (the Republic of), 2 Physics, Iowa State University, Ames, Iowa, United States, 3 Physics, Seoul National University, Seoul Korea (the Republic of)
Show AbstractCarbon nanotube semiconductor-metal intramolecular junction formation by the reconstruction of vacancy defects are investigated by tight-binding molecular dynamics simulations and first principles total energy calculations. In this study, we observe that vacancy defects in a single wall carbon nanotube is completely healed by reconstruction through a series of generalized Stone-Wales transformations and a semiconductor-metal junction with two pentagon-heptagon pair defects is formed. Our simulations suggest a mechanism for synthesis of carbon nanotube semiconductor-metal intramolecular junctions with specific locations and controlled sizes and show the possibility of application to nanoelectronic devices.
9:00 PM - II10.37
The Deformation and its Effects on the Electronic Structure of the SWCNT Bundle.
Dong Chen 1 2 , Taizo Sasaki 1 , Jie Tang 1 , Lu-Chang Qin 3
1 , National Institute for Materials Science, Tsukuba, Ibaraki, Japan, 2 , Institute of Metal Research, Chinese Academy of Sciences, Shenyang China, 3 , University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
Show AbstractThe bundle of the carbon nanotube is a class of the materials with potential functionalities. We have studied the structural and electronic properties of the single-wall carbon nanotube (SWCNT) in the bundle form under the uniaxial pressure theoretically. The density-functional theory was applied to the bundle of three types of semiconducting SWCNTs, (8,0), (10,0), and (11,0). The tubes were arranged in the triangular lattice as the bundle and the uniaxial pressure was given along the direction perpendicular to the tube axis so that the elliptic deformation would occur. The electronic structures and the total energies were calculated with a full optimization of the atomic position and the lattice constants at each pressure. The results of the calculations exhibited that an abrupt change of the structure occurs at certain pressure for all three types of the bundles although the symmetry of the system is intact. At this change, an elongation was observed in the lattice constant perpendicular to both the pressure and the tube axis, and in the lattice angle. As a result, the triangular-lattice configuration of the tubes is largely deformed. Moreover, the deformation of the tube cross-section becomes remarkable for the (11,0)-tube bundle, showing a flat shape.All types of the bundle show a energy gap at the ambient condition. While the gap rapidly decreases by applying the pressure, it stops at a certain pressure. When the pressure is increased, the energy gap keeps almost same value for the (8,0)- and (11,0)-tube bundle or increases for the (10,0)-tube one, and it suddenly drops to zero. Such a complicated behavior of the energy gap was found to be related to the structural change. However, this semiconductor-metal transition for (8,0) and (11,0) occurs at the pressure much lower than that mentioned above.
9:00 PM - II10.38
Oxygen in Graphite Oxide Structures.
JoAnn Scales 1 , Senthil Sambandam 1 , Tocarra Cecil 1 , Weijie Lu 1
1 Department of Chemistry, Fisk University, Nashville, Tennessee, United States
Show Abstract9:00 PM - II10.39
Tuning the Thermal Conductivity of Single Wall Carbon Nanotubes through Carbon Ad-dimer Defects and Methylene Functionalization.
Shashishekar Adiga 1 , Michael Sternberg 3 , Peter Zapol 1 2 , Larry Curtiss 1 2 , Donald Brenner 4
1 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States, 3 Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois, United States, 2 Chemistry Division, Argonne National Laboratory, Argonne, Illinois, United States, 4 Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina, United States
Show AbstractFunctionalization of single wall carbon nanotubes (SWNTs) has attracted considerable interest as a way to modify their physical, chemical and electronic properties. A recent density functional study of energetics of addition of carbon dimer (C2) defects has suggested that C2 functionalization presents a promising way to tune electronic and chemical properties of SWNTs [1]. Here, the effect of functionalization by C2 and methylene (CH2) groups on the thermal conductivity of (5,5) SWNTs is explored using classical molecular dynamics (MD) simulations. In particular, SWNTs with attachments of C2 in horizontal and vertical configurations, CH2 groups, and C2-CH2 groups in random positions at different densities were considered. In addition, SWNTs with C2 defects added symmetrically around the circumference of the tube that results in a bump were considered. The results show that functionalization of SWNTs with C2 groups in a bumpy configuration reduces their thermal conductivity drastically. Also, among randomly placed horizontal C2, vertical C2, and C2-CH2 groups, C2-CH2 modification is most effective in reducing the thermal conductivity. References[1] M. Sternberg, L. A. Curtiss, D. M. Gruen, G. Kedziora, D. A. Horner, P. C. Redfern, and P. Zapol, Phys. Rev. Lett. 96, 075506 (2006)
9:00 PM - II10.4
SERS Investigations on Single-Walled Carbon Nanotubes Networks Decorated with Silver Nanoparticles.
Yi-chieh Chen 1 , Robert Young 1 , Julie Macpherson 2 , Neil Wilson 3
1 Materials Science Centre, University of Manchester, Manchester United Kingdom, 2 Department of Chemistry, University of Warwick, Coventry United Kingdom, 3 Department of Physics, University of Warwick, Coventry United Kingdom
Show Abstract2D single-walled carbon nanotubes (SWNTs) networks were used in this work for electrochemical deposition of Ag onto the SWNT networks. This approach results in the formation of Ag nanoparticles over the SWNTs networks with their diameter and density varying from the electrode, enabling the fabrication of controllable SERS environment for the investigation of SWNTs.The surface enhancement of SWNTs on this “graded” substrate was analysed from the SWNTs Raman intensity enhancement with different regions of the substrate under different excitation wavelengths. The Raman intensity was increased due to the localized surface plasmon resonance of Ag particles, showing dependence as a function of distance away from the contact electrode as well as on the laser energy used. The optical property of the deposited Ag particles, AFM and electron microscopy investigations on the morphology of particles were analyzed, providing strong correlations to the degree of enhancement on the SWNTs Raman bands. This knowledge is used to increase the enhancement by adjusting the nanoparticle size and density. The resultant SWNTs/Ag nanostructure demonstrates a great promise of studying SERS of nanotubes, enabling sensitive probing of the effect of the physical environment on the SWNTs. The optimised substrates were applied as a generic, controllable SERS substrate for high sensitivity SERS study of a variety of target molecules.
9:00 PM - II10.40
Ab initio Transport Simulations of Large Scale Carbon-nanotube-based Sensors.
Alexandre Rocha 1 , Mariana Carvalho 1 , Adalberto Fazzio 1 , Antonio da Silva 1
1 Departamento de Física dos Materiais e Mecânica, Universidade de São Paulo, São Paulo, São Paulo, Brazil
Show Abstract9:00 PM - II10.41
From Graphene to Graphite: A Tight-binding Hamiltonian for Band Structure and Carrier Transport in Layered Nanoribbons.
Daniel Finkenstadt 1 , Gary Pennington 2 , Michael Mehl 1
1 , Naval Research Laboratory, Washington, District of Columbia, United States, 2 Electrical Engineering, University of Maryland, College Park, Maryland, United States
Show AbstractTo understand nanoribbons of graphene, and multilayers of such ribbons, we developed an ab initio parametrized fit to Carbon and Hydrogen chemical data, out to arbitrary neighbor interactions, including relaxations. Our computed band structure shows an increase in the number of zigzag edge states and a decrease in the armchair edge band gap when ribbons are multilayered. Further, the well-known three-family behavior of armchair bangaps is confirmed and shown to also apply to the Fermi velocity of charge carriers, which can have + or - 20% deviations in two of the families, compared to an ideal Fermi velocity, close to that of the infinite sheet, for the third, nearly-metallic family of ribbons. Boltzmann carrier transport simulations from calculated phonon spectra also show a familial dependence of conductance, peak field-effect mobility and "on" conductance that increase linearly with ribbon width. We will also discuss phonon-limited scattering and impurity scattering of charge carriers in graphene.
9:00 PM - II10.42
Quantifying Structural Characteristics of Carbon Nanotube Ensembles using X-ray Scattering.
Anastasios Hart 1 2 , Eric Verploegen 3 , Benjamin Wang 4 , Ryan Bennett 4 , Robert Cohen 4
1 Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 2 Mechanical Engineering, MIT, Cambridge, Massachusetts, United States, 3 Materials Science and Engineering, MIT, Cambridge, Massachusetts, United States, 4 Chemical Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractThe thickness of dense aligned films of carbon nanotubes (CNTs) grown from thermal CVD can reach several millimeters, suggesting manufacturing feasibility for prospective applications including thermal and electrical interface layers and reinforced composite materials. The CNT diameter and orientation within these films is traditionally characterized using scanning and transmission electron microscopy (SEM and TEM). However, the requirement of removing CNTs from the substrate and the restricted field of view in TEM make it challenging to elucidate spatial variations in film morphology. Furthermore it is difficult to quantitatively compare orientation and CNT areal density using SEM. We have recently demonstrated how small-angle X-ray scattering (SAXS) can provide locally averaged, non-destructive, quantitative measurements of these parameters. Here, we establish the limits of X-ray scattering for measuring the inner and outer diameter, alignment, and areal density (average tube-tube spacing) of ensembles of CNTs within as-grown aligned and tangled films, and in films which are deformed and/or densified by direct mechanical or capillary-induced action. Data is combined from ultra small-angle (USAXS), small-angle (SAXS), and wide-angle (WAXS) X-ray scattering, and measurements made by curve-fitting of the scattering patterns are verified by SEM and TEM on selected samples. Generally, by fitting to a hard-cylinder model, SAXS can measure CNT diameters from 50 nm to below 5 nm (including SWNTs). WAXS of the graphene layers in a MWCNT, and fitting to the Scherrer equation, allow for the number of sheets and thus the inner tube diameter to be determined. USAXS reveals low-q scattering, probing features up to 1 micron in size, allowing for changes in the tube-tube spacing to be analyzed (typically ~100 nm in a VA-CNT forest). Additionally, the direction and degree of alignment can be quantified through these scattering methods. By changing the beam path through the sample (100 micron spot size) in SAXS, we use VA-CNTs forest as a model system for spatially mapping these characteristics. Further, by characterizing a wide variety of samples prepared from different depositions of the same catalyst material (deposited by e-beam evaporation), we quantitatively establish the repeatability of CNT diameter and alignment under identical growth conditions in a tube furnace.
9:00 PM - II10.43
Study Of Carbon Nanotubes Obtained By Microwave Heating For Sports Materials.
Oxana Kharissova 1 , Olha Velychko 1 , Artur Torres 1 , Ubaldo Ortiz 1
1 FCFM, UANL, Monterrey Mexico
Show AbstractNanotechnology has been established the last few decades as a promising tool to drive technological development in this century. Nanotechnology — engineering on a scale of individual atoms — is a way to make new materials, or to improve properties of existing materials. Its uses range from medical devices to car paint. And in the past, any shift in materials science has eventually altered sports.In this work, we report a short summary of the development of a technique was carried out to obtain Nanomaterials with aligned carbon nanotubes. Study the impact resistant the composite stick for aplication of gym products. The aligned carbon nanotubes (CNTs) were synthesized by microwave (MW) irradiation heating with efficiency up to 90%. In this research, Scanning Electron Micriscopy (SEM), Atomic Force Micriscopy (AFM) and Transmission Electron Microscopy (TEM) are used for study of nano epoxy with aligned carbon nanotubes by microwave heating.
9:00 PM - II10.44
NMR Investigations of the Structure and Transport of Water within Hydrophobic, Nanoscale Channels.
Julie Herberg 1 , Jason Giuliani 1 , Robert Maxwell 1 , Jason Holt 1
1 Chemistry and Material Science, Lawrence Livermore National Laboratory, Livermore, California, United States
Show AbstractA single wall carbon nanotube (SWCNT) represents a confined hydrophobic system. Recently, an of orders of magnitude (greater than 1000 times relative to hydrodynamic theory) enhancement in water flow through sub-2nm diameter carbon nanotube channels has been shown. Early molecular dynamics studies predicted novel structures for water confined within carbon nanotubes and enhanced transport rates that are not seen in the bulk. However, different simulation methods (ab-initio MD) have suggested the absence of water ordering, while enhanced transport rates are still predicted. Recent experimental studies suggest water ordering does exist within SWCNTs under low temperature conditions (from below the bulk freezing point of water to cryogenic conditions), although the methods were incapable of providing dynamic information relating to the diffusion rate of water through the channels. Thus, there is no general agreement as to whether water ordering is a general phenomenon within SWCNTs, particularly under the room temperature conditions relevant to many proposed nanofluidics applications of SWCNTs. It is also unclear the extent to which water ordering, if present, affects water dynamics, and on what length scale ordering becomes important. We are currently using 1H NMR techniques to probe the structure and dynamics of the water inside the carbon nanotubes that have shown an enhancement in flow and directly measure the diffusion of water inside the carbon nanotubes.This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory, under contract # W-7405-ENG-48.
9:00 PM - II10.45
Stabilization Mechanisms in Multiwalled Peapods.
Roberto Scipioni 1 , Atsushi Oshiyama 2 3 , Takahisa Ohno 4
1 ICYS, NIMS, Tsukuba Japan, 2 Department of Applied Physics, University of Tokyo, Tokyo Japan, 3 , JST-Crest, Kawaguchi Japan, 4 Computational Materials Science Center, NIMS, Tsukuba Japan
Show Abstract9:00 PM - II10.46
Carbon Cones - a Structure with Unique Properties.
Henning Heiberg-Andersen 1 , Geir Helgesen 1 , Kenneth Knudsen 1 , Patrick Pinheiro 1 , Arne Skjeltorp 1 2 , Eldrid Svasand 1 2 , Arnljot Elgsaeter 3 , Torgunn Garberg 3 , Stine Naess 3 , Steinar Raaen 3 , Merete Tverdal 3 , Xiaofeng Yu 3
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 Abstract9:00 PM - II10.47
Novel Nanocarbons: Quantification of Global Topology and Curvature Perspectives from Vibrational Spectroscopy.
Sanju Gupta 1 , A. Saxena 2
1 Electrical and Computer Engineering, University of Missouri, Columbia, Missouri, United States, 2 Theoretical Division, Los Alamos National Laboratory, New Mexico, New Mexico, United States
Show AbstractCarbon nanotubes (both the single- and multi-walled) in the family of nanostructured carbons are of great interest because of several unsurpassable physical properties. In addition to space applications, when exposed to high energy electron beam from transmission electron microscopy, the results seem quite promising in terms of nano-manufacturing for producing novel nanocarbons [1, 2]. Experimental studies of effects of electron beam irradiation on carbon nanotubes show that multi-walled nanotubes tend to be relatively more robust than their single-walled counterparts. The increased exposure on an individual bundle of single-wall nanotubes promoted graphitization, pinching, and cross-linking analogous to polymers forming an intra-molecular junction (IMJ) within the area of electron beam focus, possibly through aggregates of amorphous carbon [2, 3]. Formation of novel nanostructures (nano-ring and helix-like) due to irradiation are observed. These studies shed light on the dynamics of nanomanufacturing and a regime of possible relevance of these materials for: (i) short-term space missions; (ii) radiation hard programmable logic circuits; and (iii) radiation pressure sensors. It is suggestive that a local reorganization may be occurring possibly due to local melting. Through resonance Raman spectroscopy (vibrational spectroscopy) technique we also elucidate an important notion of global topology and curvature at nanoscale which points to an emergent paradigm of Curvature/Topology --> Property --> Functionality in these technologically important geometries of carbons: nanotubes, fullerenes, nanorings, nanocones, nanohorns and nanodisks. To this end, we have determined the variation in first order high frequency Raman band (i.e. G band) which indicates a strong electron-phonon coupling (EPC) [2] and in our present report we made an attempt to correlate the G band to curvature index (chi) in order to quantify the global topology from local topology. It is worth mentioning that these concepts also apply to nanostructures of other ``topological materials" such as BN nanotubes and nanotori, helical gold nanotubes as well as Möbius conjugated polymers [2]. *This work is supported in parts by internal MU Research Council and MURR Grants (SG) and DoE (AS). [1] S. Gupta et. al. Mater. Res. Soc. Symp. Proc. 863, Q6.3-Q6.9 (2005). [2] S. Gupta and A. Saxena, Mater. Res. Soc. Symp. Proc. 960E, N9.6-N9.15 (2007).
9:00 PM - II10.5
Molecular Orientation in Individual Electrospun Nanofibers Observed via Polarized Raman Spectroscopy.
Leon Bellan 1 , Harold Craighead 1
1 School of Applied and Engineering Physics, Cornell University, Ithaca, New York, United States
Show AbstractUsing polarized Raman spectroscopy, we have recorded Raman spectra from individual electrospun Nylon-6 nanofibers. Qualitative analysis of these single fiber spectra, compared to those of unoriented and oriented Nylon-6 film, indicates significant molecular orientation. Because electrospinning produces fibers in a jet with a large strain rate, this molecular orientation is expected. Utilizing measured polarized Raman spectra from four scattering geometries for each fiber, we can calculate the P2 and P4 Legendre polynomial orientation functions for a single fiber. We discuss the prospects for quantitative measurement of molecular orientation in a single nanofiber (given the signal-to-noise ratio and error of the measurement) and comparison of orientation between fibers. Such measurements could yield information about the uniformity of the electrospinning process and resulting fibers, and may also allow comparison between spectrally measured orientation functions and single fiber mechanical properties.
9:00 PM - II10.6
Raman and Computational Studies of the Electronic Origins of Intermediate Frequency Mode Enhancements in Carbon Nanotubes.
Stephen Doorn 1 , Svetlana Kilina 2 , Sergei Tretiak 2 , Zhengtang Luo 3 , Fotios Papadimitrakopoulos 3
1 Chemistry Division, Los Alamos National Lab, Los Alamos, New Mexico, United States, 2 Theoretical Division and Center for Nonlinear Studies, Los Alamos National Lab, Los Alamos, New Mexico, United States, 3 Department of Chemistry, University of Connecticut, Storrs, Connecticut, United States
Show AbstractWe discuss a new class of intermediate frequency modes (IFMs) associated with the E22 and E11 transitions in semiconducting single-walled carbon nanotubes. We have studied these IFMs with resonance Raman excitation spectroscopy in the near-IR region (1.26 eV to 1.77 eV) [1]. These modes display a similar “stepwise” dispersive behavior and electronic resonance behavior as is displayed by previously investigated IFMs connected to the E33 and E44 transitions [2,3]. Analysis of the current results fits well within the theoretical framework of refs. 2 and 3. However, symmetry considerations when excitons are taken into account suggest that the IFM electronic resonances may instead be with true intermediate states lying between the E11 and E22 levels. We have undertaken quantum chemical calculations of these intermediate transitions to shed light on the possible origins of these resonances. Computations have included an analysis of potential 2-photon, cross-polarized, and other intermediate states. We will discuss the computational results in the context of likely assignments of the IFM resonant transitions.1)Luo, Z.; Papadimitrakopoulos, F.; Doorn, S.K.; Phys. Rev. B 75, 205438 (2007).2)Fantini, C.; et. al. Phys. Rev. Lett. 93, 087401 (2004).3)Fantini, C.; et. al. Phys. Rev. B 72, 085446 (2005).
9:00 PM - II10.8
Raman Studies and Redox Titration of Solutions of Nanotube Salts.
Fabienne Dragin 1 2 , Alain Penicaud 3 , Eric Anglaret 2 , Richard Martel 1
1 Regroupement quebecois sur les materiaux de pointe, Universite de montreal, Montreal, Quebec, Canada, 2 Laboratoire des colloides, verres et nanomateriaux, UMR CNRS 5587, Universite Montpellier II, Montpellier France, 3 Centre de recherche Paul Pascal- CNRS, Universite Bordeaux I, Bordeaux France
Show Abstract9:00 PM - II10.9
Universal Kataura Plot for Optical Transition Energies of Single-Walled Carbon Nanotubes.
Jong Hyun Choi 1 , Michael Strano 1
1 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show Abstract9:00 PM - II10: Theo-Char
II10.48 Transferred to II15.62
Show Abstract
Symposium Organizers
Kenji Hata AIST
Annick Loiseau Laboratoire d'Etude des Microstructures (LEM)
Yoke Khin Yap Michigan Technological University
Ming Zheng DuPont Central Research and Development
II11: NEMS and Related Properties
Session Chairs
Craig Friedrich
Annick Loiseau
Yoke Khin Yap
Wednesday AM, November 28, 2007
Room 312 (Hynes)
9:00 AM - **II11.1
Carbon Nanotube NEMS: Pros and Cons.
Eleanor Campbell 1 2 , Anders Eriksson 2 , SangWook Lee 2 , Jari Kinaret 3 , Andreas Isaacson 3
1 Chemistry, Edinburgh University, Edinburgh United Kingdom, 2 Dept. of Physics, Gothenburg University, Gothenburg Sweden, 3 Dept. of Applied Physics, Chalmers University of Technology, Gothenburg Sweden
Show AbstractCarbon nanotubes are ideal materials to explore the possibilitiles of nanoelectromechanical systems (NEMS). The extreme mechanical properties of nanotubes combined with their lightweight hollow structure and their favorable electronic properties make them potentially very interesting as molecular sensors, fast switches and high frequency filters, to name just a few possibilities. In this talk I will discuss the predictions of nanotube high frequency NEMS properties and describe the experimental approaches and measurements that have been made. The advantages and disadvantages of nanotube NEMS will be discussed.
9:30 AM - II11.2
In-Situ Plastic Deformation of Carbon Nanotubes.
Jianyu Huang 1
1 Center for Integrated Nanotechnologies (CINT), Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractCurrently there exists a gap between the microstructure and the corresponding electrical and mechanical property studies of nanostructured materials, i.e. studying the microstructure without knowledge of the related physical properties, or vice versa. By using a Nanofactory transmission electron microscopy-scanning tunneling microscopy (TEM-STM) platform, we were able to characterize simultaneously the atomic-scale microstructure with its electrical and mechanical properties of individual carbon nanotubes [1-3], which are perceived as being rather brittle because of the strong C-C sp2 bonds in the honeycomb lattice. It is postulated that nanotubes accommodate no plastic deformation even beyond the elastic limit or before breakage at room temperature. I report here our recent discoveries of plastic deformation, as characterized by the superplastic elongation, kink motion, and dislocation climb, in carbon nanotubes at about 2000 °C. The plastic deformation induces dramatic electronic property changes of the nanotubes. These discoveries indicate that there are rich nanomechanics and nanoelectronics in carbon nanotubes at high temperatures. Our discoveries may provide important implications for the high temperature applications of carbon nanotubes. [1] J. Y. Huang et al. Nature 439, 281 (2006).[2] J. Y. Huang et al., Phys. Rev. Lett. 94, 236802 (2005); 97, 075501 (2006); 98, 185501 (2007). [3] J.Y. Huang et al., Nano. Lett. 6, 1699 (2006).
9:45 AM - II11.3
Mechanical Behavior of Carbon Nanotubes Under Contact Loading.
Siddhartha Pathak 1 , Surya Kalidindi 1 , Z. Cambaz 1 , Vadym Mochalin 1 , Gleb Yushin 1 , Yury Gogotsi 1
1 , Drexel University, Philadelphia, Pennsylvania, United States
Show AbstractMost of the past experiments have focused on the tensile loading and bending of CNTs to extract their mechanical properties. There are only a handful of experimental measurements in literature detailing the use of nanoindentation as a tool to measure the local properties of CNT arrays. Our analysis of the nanoindentation data centers on translating spherical nanoindentation generated load-displacement curves into indentation stress-strain (ISS) curves for a better representation of material deformation under contact loading. A major advantage of spherical indentation is that, unlike sharp indenters, it allows us to follow the entire evolution of damage modes from initial elasticity, the initiation of plasticity at a critical load (yield behavior) to full plasticity. The ISS curves are especially helpful in this respect since they permit us to estimate the modulus of the sample from the initial loading segment itself. Majority of the methods in literature however utilize the unloading curve for measurement of nanoindentation properties. This corresponds to evaluating the properties of a surface that is already altered by prior indentation. Together with the approximations inherent to Hertz solutions for this altered situation (the unloading is no longer from a flat surface), it results in a substantial deviation from the actual values. The ISS curves are also capable of providing valuable information about the yield and post-yield behavior of the sample in indentation-type deformation modes. Nanoindentation experiments with a spherical diamond tip of 1 micron radius were carried out on the CNT films of 100-10000 nm in thickness grown on the Si-face and C-face of 6H SiC wafers. Upon conversion of the load-displacement curves to ISS curves, 3 distinct stages were clearly visible. Initially the CNTs are elastically compressed by the indenter (E=20±4GPa). In the second stage, there is a sudden deviation from the initial elastic slope corresponding to the CNT buckling or bending. At this stage the resistance to penetration of the indenter decreases as the CNTs are pushed aside. Finally after the indenter has penetrated the entire CNT thickness we can see a strong increase in slope with the modulus and hardness approaching that of SiC. Our preliminary results also show an increase in the initial elastic modulus of the CNTs as indenter tips of larger radii were used (E≈25 GPa for a 5 micron spherical indenter tip and E≈30 GPa for a 13.5 micron tip). This is indicative of a greater resistance to the indentation pressure as more CNTs come in contact with indenter tips of higher radii. As such, this study constitutes a crucial first step in the formulation of a rigorous mechanical framework for analyzing the local mechanical properties for CNT forests.
10:00 AM - II11.4
Measuring the Chirality of Multiwalled Carbon Nanotubes – Each and Every Shell.
Lu-Chang Qin 1 , Hakan Deniz 1
1 Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
Show AbstractMany of the properties of a carbon nanotube, single-walled or multiwalled, are very sensitive to the chirality, specified by its chiral indices (n,m), of the nanotube. For a multiwalled carbon nanotube, it is necessary to determine the chirality (chiral indices (n,m) or equivalently diameter and helicity) of each and every shell, from which, for example, the metallicity of each shell can be told directly from the chiral indices (n,m). Electron diffraction can now be used to determine the chiral indices (n,m) of individual carbon nanotubes for both single-walled and multi-walled. We have established an electron diffraction method with high accuracy that allows us to obtain the chiral indices (n,m) of each and every shell of multiwalled carbon nanotubes. To improve the accuracy of the results, we apply a combination of two methods: one uses the intensity profiles of the principal reflection layer lines due to the primary Bragg reflections of graphene and the other makes uses of the ratios of the principal layer line spacings. We will present examples of application of the helical diffraction method with the chiral indices (n,m) of each and every shell determined for double-walled, triple-walled, quadruple-walled, etc. A general strategy and systematic procedure will also be presented and discussed.
10:15 AM - II11.5
Real-time sub-100nm thermal Imaging of Carbon Nanotubes.
Kamal Baloch 1 , Todd Brintlinger 2 , Yi Qi 2 , John Cumings 2 3
1 Institute for Physical Science and Technology , university of Maryland, College Park, Maryland, United States, 2 Department of Materials Science and Engineering, University of Maryland, College Park, Maryland, United States, 3 Center for Nanophysics and Advanced Materials, University of Maryland, College Park, Maryland, United States
Show AbstractFor practical applications of carbon nanotubes it is essential to have a clear understanding of their thermal and electrical properties. Development of in-situ, high-resolution electron thermal microscopy, presented here, enables real time thermal imaging of multi-walled carbon nanotubes (MWCNT) both under electrical transport and as passive thermal elements. This technique allows the study of heat transfer and the extraction of important parameters like thermal conductivity. Experiments are performed below 200 C and allow thermal cycling of a given device. Samples are prepared on free standing silicon nitride membranes of known thermal conductivity in multiple e-beam lithography steps. Joule heating of metallic wires thermally connected to MWCNT provides a heat source. For thermometry, the melting transitions of individual 100nm Indium islands on the back side of the membranes act as local temperature probes, yielding high-resolution thermal maps. The thermal conductivity of an individual MWCNT can be determined from comparisons of experimentally generated thermal maps and those obtained by finite element analysis. The inherent flexibility of the lithography together with the robust local temperature probes allows a variety of geometries to be examined. Experimental procedure, video demonstration, and simulation will all be presented in the course of this presentation.
10:30 AM - **II11.6
Nanomaterials and Nanoscale Physics: A Basis for NEMS
Alex Zettl 1
1 Physics, University of California at Berkeley, Berkeley, California, United States
Show AbstractI will review some unique properties of nanoscale materials and phenomena with particular relevance to NEMS (Nanoelectromechanical Systems). The materials include nanotubes, nanocrystals, and nanodroplets, and the phenomena include field emission, electromigration, surface tension, thermal transport, mechanical vibrations, and chemical bonding. NEMS systems of interest are actuators and motors, tuned high frequency, high Q resonators, memory devices, and general transducers. The underlying materials science and physics is rich, with significant applications potential.
11:00 AM - II11: NEMS
BREAK
II12: Electronics and Related Properties I
Session Chairs
Kenji Hata
Annick Loiseau
Yoke Khin Yap
Ming Zheng
Wednesday PM, November 28, 2007
Room 312 (Hynes)
11:30 AM - **II12.1
Epitaxial Graphene.
Walt deHeer 1
1 , Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractGraphene multilayers are grown epitaxially on single crystal silicon carbide. This system is composed of several graphene layers of which the first layer is electron doped due to the built-in electric field and the other layers are essentially undoped. Unlike graphite the charge carriers show Dirac particle properties (i.e. an anomalous Berry's phase, weak anti-localization and square root field dependence of the Landau level energies). Epitaxial graphene shows quasi-ballistic transport and long coherence lengths; properties which may persists above cryogenic temperatures. Paradoxically, in contrast to exfoliated graphene, the quantum Hall effect is not observed in high mobility epitaxial graphene. It appears that the effect is suppressed due to absence of localized states in the bulk of the material. Epitaxial graphene can be patterned using standard lithography methods and characterized using a wide array of techniques. These favorable features indicate that interconnected room temperature ballistic devices may be feasible for low dissipation high-speed nanoelectronics. In this talk the latest developments in this rapidly growing field will be presented.
12:00 PM - II12.2
Interference of Electron Waves in a Ballistic Graphene Transistor.
Sungjae Cho 1 , Michael Fuhrer 1
1 Department of Physics and Center for Superconductivity Research, University of Maryland, College Park, Maryland, United States
Show AbstractWe have prepared single- and few-layer graphene samples by mechanical exfoliation of Kish graphite on SiO2/Si substrates. We have fabricated graphene field-effect transistors by electron beam lithography followed by thermal evaporation of Cr/Au or Permalloy source and drain electrodes; the conducting silicon underneath 300 nm silicon dioxide serves as a back gate electrode. We find that at low temperatures that the two-dimensional plot of conductance as a function of gate voltage and drain voltage shows an interference pattern of maxima and minima which occur along diagonal lines. We analyze the pattern in terms of interference of electron waves reflected between source and drain electrodes. The slope of the lines measures the compressibility of the two-dimensional electron system, and has strikingly different dependence on carrier density (gate voltage) for single- and few-layer graphene samples, as expected theoretically.
12:15 PM - II12.3
Electrical Properties of Transparent Single-Wall Carbon Nanotube Networks.
Teresa Barnes 1 , Jeffrey Blackburn 1 , Jao van de Lagemaat 1 , Michael Heben 1 , Timothy Coutts 1
1 , National Renewable Energy Lab, Golden, Colorado, United States
Show Abstract12:30 PM - II12.4
Thin Carbon Nanotube Films for Transparent Electrodes and FETs - Simulations and Electric Force Microscopy Studies.
Mark Topinka 1 , Mike Rowell 1 , Michael McGehee 1 , David Hecht 2 , George Gruner 2
1 , Stanford University, Stanford, California, United States, 2 Physics, UCLA, Los Angeles, California, United States
Show AbstractIn this talk we present our work on understanding thin, transparent carbon nanotube (CNT) films. CNT films are a good candidate for a replacement for ITO and other transparent conductors in applications such as LCDs and solar cells due to their good performance (~100 Ohms/square, ~85% transparency), liquid processibility, flexibility, and falling cost. It has been shown that the overall conductivity of CNT films behaves as expected by basic percolation theory, g=g0(n-nc)^a for very sparse films around the percolation threshold, (where “g” is conductivity, “n” is tube density, and “nc” is the percolation onset, and where “a” is a critical exponent which lies between the values of 1.33 for a 2-d network and 1.94 for a 3-d network), while for large, thicker films the film behaves like a bulk conductor, and g=g1*n. While the broad agreement with theory is good, the critical real-world values of the prefactors, g0 and g1, in both these equations have largely simply been adjustable curve-fitting parameters. Here we perform electrical measurements, scanning probe microscopy experiments and detailed nanotube network simulations to determine the underlying physical parameters, such as intra-tube resistance, tube-junction resistance, and junction density which give rise to these values and to highlight what efforts for improvement are likely to be the most fruitful in pushing the performance of CNT films closer to their theoretical limits. Our scanning probe microscopy studies are performed using electric force microscopy (EFM) on both sparse, CVD grown films where all tubes in the network are visible, as well as thicker real-world electrodes (~100nm thick) where only the top layer of tubes is visible. We find that our sparse network results are in good agreement with values of tube resistance and tube-tube junction resistance taken both from our measurements and literature. The results of our thicker film studies show that the tube-tube resistances in these films appears to be higher than in the sparse films, and we present EFM and simulation results to demonstrate this conclusion. We also have performed nanotube network simulations to determine the effects of different semiconducting / metallic ratios of nanotubes, as well as the effects of other real world factors such as tube bending, different distributions of junction resistances and tube lengths, and impurities or defects within the tubes themselves.
12:45 PM - II12.5
High Frequency Flexible Nanotube Transistors.
Vincent Derycke 1 , Nicolas Chimot 1 , Arnaud Le Louarn 2 , Marcelo Goffman 1 , Henri Happy 2 , Gilles Dambrine 2 , Jean-Philippe Bourgoin 1
1 SPEC, CEA Saclay, Gif-sur-Yvette France, 2 IEMN, CNRS, Lille France
Show AbstractFlexible electronics is a fast growing field driven by important perspectives in terms of applications (e-papers, smart tags…). As for conventional electronics, applications would be much improved and would diversify if devices and circuits could work at high frequency (HF). Polymers and small molecules are for now the materials of choice for flexible applications but the very low carrier mobility in these materials (<10 cm2/V.s) prevents their use at frequencies above some tens of MHz. In this context, carbon nanotubes appear particularly promising. Indeed, their exceptional mechanical properties make them suitable for the fabrication of highly flexible devices as was demonstrated by several groups. Moreover, their electrical properties, and in particular the very high carrier mobility (>10^4 cm2/V.s), make them one of the most suitable material for very high frequency applications. Combining these two properties could yield to the best performing flexible HF devices and circuits. Still, the fabrication and characterization of HF devices based on nano-objects is challenging because (i) the high impedance of individual nano-scale objects does not match the 50 Ohms impedance of conventional HF equipment and (ii) the parasitic capacitances tend to dominates because of the relative small size of the channel compared with the electrodes and contact pads. Nevertheless, using configurations with multiple nanotubes in parallel, we recently showed that HF nanotube transistors with intrinsic cut-off frequencies as high as 30 GHz (after de-embedding of the parasitics, 4 GHz without de-embedding) could be obtained on rigid substrates [1,2]. Dense arrays of mostly aligned nanotubes were deposited using di-electrophoresis to serve as the channel leading to high current and high transconductance devices. We recently adapted the structure of these HF devices to plastic substrates and obtained highly flexible HF transistors. Nanotube transistors on PET (poly-ethyleneterephtalate) show constant transconductances up to at least 6 GHz and as-measured cut-off frequencies as high as 1 GHz (5-8 GHz after de-embedding). Electrical measurements upon bending reveal a constant transconductance up to radius of curvature below 3 mm. All together, our devices are among the best HF flexible devices to date, competing favourably with nanowire based devices. Finally, analysis of the HF results on rigid substrate show clearly the geometrical and nanotube layout parameters to improve to realise the true potential of this flexible transistor technology that we estimate much beyond 30 GHz[1] Bethoux et al, A 8-GHz ft Carbon Nanotube Field-Effect Transistor for Gigahertz Range Applications, IEEE Electron.Dev. Lett. 27, 681 (2006).[2] Le Louarn A. et al. Intrinsic current gain cut-ff frequency of 30 GHz with carbon nanotube transistors, Appl. Phys. Lett. 90, 233108 (2007).
II13: Non-carbon Nanostructures III
Session Chairs
Kenji Hata
Annick Loiseau
Yoke Khin Yap
Ming Zheng
Wednesday PM, November 28, 2007
Room 312 (Hynes)
2:30 PM - **II13.1
Direct Synthesis of Single-Walled Semiconducting BCN Nanotubes and Development of Field Effect Transistors.
Enge Wang 1
1 , Institute of Physics, Chinese Academy of Sciences, Beijing China
Show AbstractAs a member of light-element nanotubular materials, the ternary BCN nanotubes are attractive in that their properties are much less dependent on nanotube geometry. In this talk, I will report the direct synthesis of single-walled BCN nanotubes (BxCyNz-SWNTs) by bias-assisted hot filament chemical vapor deposition [1]. The field emission conventional and energy-filtered high-resolution transmission electron microscopes have shown that the obtained BxCyNz-SWNTs exhibit straight cylindrical structure in a similar way to pure carbon SWNTs, and the constituting B, C, and N elements are homogenously distributed within the tube walls. X-ray photoelectron spectroscopy also reveals the ternary bonding nature. Field effect transistors made of the as-grown BxCyNz-SWNTs have been used to study the electrical transport properties [2]. More than 94% of the BxCyNz-SWNTs from over 200 samples are semiconducting. In addition, the on-and-off current ratio (Ion/Ioff) of the BCN-SWNT field effect transistors reaches up to 10^6. By compared with the electronic property of pure carbon SWNTs obtained by the same set-up, our present experimental results indicate that in situ introducing B and N in CVD growth of carbon nanotubes is a viable route for selectively altering the electronic properties, which shed light on the key issue of potential technological importance. [1] W.L. Wang, X.D. Bai, K.H. Liu, Z. Xu, D. Golberg, Y. Bando, and E.G. Wang, J. Am. Chem. Soc. 128, 6530(2006); [2] Z. Xu, K.H. Liu, W.L. Wang, X.D. Bai, E.G. Wang, and Hongjie Dai, (submitted).Funding provided by NSFC, MOST, and CAS of China.In collaboration with Xuedong Bai, Wenlong Wang, Zhi Xu, and K.H. Liu, D. Golberg and Y. Bando at NIMS, and Hongjie Dai at Stanford University.
3:00 PM - II13.2
Growth of Single Crystalline ZnO Nanotubes and Nanosquids.
Abhishek Prasad 1 , Samuel Mensah 1 , Jiesheng Wang 1 , Vijaya Kayastha 1 , Archana Pandey 1 , Yoke Khin Yap 1
1 , Michigan Technological University, Houghton, Michigan, United States
Show AbstractZnO has proven to be a versatile functional material with promising properties. ZnO nanostructures are especially promising for applications at the nanoscale. Here we report the growth of ZnO nanotubes [1, 2] and nanosquids [3], which can be directly grown on planar oxidized Si substrates without using catalysts and templates. A conventional thermal CVD technique was used for the synthesis of these interesting ZnO nanostructures. Our experiments were conducted in a double-tube configuration. The substrates were inserted into a small quartz tube closed at one end with a mixture of ZnO and graphite powders in a ratio of 2:1, respectively. This tube is then inserted into the cylindrical quartz tube chamber of the thermal CVD furnace such that the mixed powder is at the center of the horizontal furnace. In this arrangement, the mixed powder will be combusted at 1100 oC and the substrates are at a temperature of ~650 oC. Oxygen gas was introduced into the quartz tube at a flow rate of 40 sccm. Tubular ZnO nanostructures are formed on the substrates when appropriate cooling rate was then applied.Characterization of these ZnO nanostructures was conducted by X-ray powder diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), Field-emission scanning electron microscopy (FESEM), Raman spectroscopy, and photoluminescence (PL). Results indicate that these ZnO nanostructures were single crystals of pure hexagonal wurtzite structure. Our results show that rapid cooling rate and deficiency of oxygen contributed to the formation of tubular ZnO nanostructures. Details of our growth model guided by the theory of nucleation and the vapor-solid crystal growth mechanism will be discussed at the meeting. This work is supported by the U.S. Department of Army (Grant No. W911NF-04-1-0029, through the City College of New York), National Science Foundation CAREER award (Award No. 0447555, Division of Materials Research), and the Center for Nanophase Materials Sciences sponsored by the Division of Materials Sciences and Engineering, U.S. Department of Energy (Contract No DE-AC05-00OR22725).[1]. S. Mensah, et al., Appl. Phys. Letts. 90, 113108 (2007).[2]. Cover of the 12 March 2007 issue of Applied Physics Letters.[3]. A. Prasad, et al., J. Nanosci. Nanotech. (special issue) (2007, in press).
3:15 PM - II13.3
Self-assembly of Silicon Nanotubes.
Ming Xie 1 , Jiesheng Wang 1 , Yoke Khin Yap 1
1 , Michigan Technological University, Houghton, Michigan, United States
Show AbstractSilicon nanotubes (SiNTs) have recently attracted attention because of the peculiar properties and compatibility to the present microelectronic technology. Theoretically, many research groups have investigated the possible existence of SiNTs. Experimentally, amorphous SiNTs have been synthesized by using template methods. Nevertheless, these SiNTs cannot form good crystal structure due to disordered aggregation of silicon atoms in the inner wall of the templates. Here we report the self-assembly of SiNTs by dual RF-plasma treatments. This technique is compatible to the present integrated circuit technology without involving excessive synthesis pressures, temperatures, and wet chemical processes. The as grown SiNTs are vertically-aligned on the p-type Si substrates. Transmission electron microscopy (TEM) indicates that these SiNTs are having diameters 50-100 nm, with a wall thickness of ~10-20 nm. The lengths of these SiNTs can be as long as 15 microns, depending on the plasma configurations. The transport properties of these SiNTs were examined by conducting atomic force microscopy (AFM). Results indicate that these SiNTs are p-type semiconductors like the p-type Si substrates. Their conductivity is lower than that of the substrates. Based on a series of experimental evidences, the growth model of these SiNTs is proposed. Details on the synthesis, structural and transport properties of these SiNTs will be discussed in the meeting.This work is supported by National Science Foundation CAREER award (Award No. 0447555, Division of Materials Research).
3:30 PM - II13: NCarbon-3
BREAK
II14: Carbon Nanostructures V
Session Chairs
Kenji Hata
Annick Loiseau
Yoke Khin Yap
Ming Zheng
Wednesday PM, November 28, 2007
Room 312 (Hynes)
4:00 PM - **II14.1
Single-walled Carbon Nanotubes: Synthesis, Modification and Characterizations.
Sumio Iijima 1
1 Faculty of Science and Engineering, Meijo University, Nagoya, Aichi, Japan
Show AbstractUnique properties of CNTs depend on their structures and morphologies, and well-controlled specimens (diameter, length, quantity, chirality, structural perfection, impurity, homogeneity) will be needed for precise experiments and also for their industrial applications. Regarding these requirements, two important breakthroughs in single-wall carbon nanotube (SWCNT) growth were made recently in our laboratories at AIST (1). One is a floating catalyst-assisted CVD method of growing SWCNTs, which can provide controlled tube diameters and extremely high purity tubes with high production yield. Some of industrial use of the product is for transparent and flexible conductive films and threads. Another is the "Super-Growth" of SWCNTs, which grow vertically on various substrates including metal foils as high as one centimeter. The method has being developed into a level for the industrial production, which will be used for high power density capacitors. For characterization of the SWCNTs Raman spectroscopy of radial breathing mode (RBM) is a standard method. Another spectroscopic characterization of SWCNTs is two-D mapping of photoluminessence particularly for semiconducting tubes which are specified in terms of band gaps and excitation wavelength. The method has been applied to study the band-gap modulation of SWCNTs mostly due to stress, which is induced by doping various molecules inside the central hollows of the tubes. The importance of characterization of nano-structured materials will be demonstrated by showing the latest results of atomic structures of CNTs and their modifications, which have been revealed by an ultra-high resolution TEM with a spherical aberration corrector. Individual carbon atoms, local atomic defects of SWCNTs and individual fullerene molecules were directly recorded. Dynamic behaviors of those atoms and defects as well as doped metal atoms and organic molecules inside the tubes are of interest in terms of sophisticated device application of CNTs (2).(1) T. Saito, et al., J. Phys. Chem. B, 109, 10647-10652 (2005). D. Futaba et al., Science 306, 1362-1364 (2004). D. Futaba et al., Phys. Rev. Lett. 95, 056104 (1)-(4) (2005 D. Futaba et al., Science 306, 1362-1364 (2004). D. Futaba et al., Nature Materials 5, 987-994 (2006). (2) A. Hashimoto, et al., Nature, 430, 870-873 (2004). K. Urita, et al., Phys. Rev. Lett, 94, 155502(2005). Z. Liu, et al., Phys. Rev. Lett., 95, 187406(1)-(4) (2005). Y. Sato, et al., Phys. Rev. B, 73, 233409(2006). Suenaga, et al. Nature Nanotech. (2007). Liu, et al. Nature Materials. (2007).
4:30 PM - II14.2
Isolated Bundles of Highly Straight, Highly Uniform Single Wall Carbon Nanotubes Grown at Very Low Temperature.
Sakthi Kumar 1 , Yasuhiko Yoshida 1
1 Bio Nano Electronics Research Center, Toyo University, Kawagoe-shi, Saitama, Japan
Show AbstractAfter the invention of carbon nanotubes (CNTs) by S. Ijima, many growth methods (arc discharge, laser ablation, chemical vapor deposition etc.) have been introduced in the field to develop CNTs (both multi walled and single walled carbon nanotubes (MWCNTs and SWCNTs)) for the past one decade. However almost all of them produced endless web natured curled (tangled – spaghetti type) arch like structures of nanotubes which are difficult to purify, manipulate and assemble for building addressable nanotube structures. This problem is considered as one of the major problems currently facing by the nanotechnology field along with non uniformity of the SWCNTs. And again intense research work is going on to lower the processing temperature to use nanotubes on glass, plastic and other flexible but heat susceptible substrates by keeping the quality of nanotubes. It is generally accepted that producing CNTs at low temperatures by keeping its quality, is a highly formidable task. This is due to the fact that the relatively low growth temperature does not provide sufficient thermal energy to anneal nanotubes into perfectly crystalline structures. High temperature is necessary to form nearly defect free crystalline SWCNT structures, which having small diameters and thus having high strain energies. It is suggested that high temperature processes (such as arc discharge and laser evaporation) are the best methods to produce high quality nanotubes. In fact we may need to develop high quality nanotubes at substrate temperature much below 450 oC even to imagine the possibility of online processing for the integration of nanotubes in micro and nano electronics circuits with currently existing industrial infrastructure facilities based on complementary metal-oxide semiconductor (CMOS) technology. Here we report a new, simple but elegant processing method with which we can develop SWCNTs of short isolated bundles of high quality and highly uniform at low substrate temperatures (~280oC). This method provides solution for almost all the above mentioned problems in a single step itself. We have characterized our SWCNTs with the help of TEM, SEM, ESCA, EDS, Mapping, Line scans analysis, Raman and XRD. The characteristic features of the XRD spectrum of SWCNTs obtained by the XRD experiment clearly and undoubtedly suggest that we have succeeded to produce high quality SWCNTs at very low substrate temperature.
4:45 PM - II14.3
Low Temperature Synthesis of Carbon Nanotube on Si substrate Using Alcohol Gas Source in High Vacuum.
Takahiro Maruyama 1 2 , Kenji Tanioku 1 , Shigeya Naritsuka 1 2
1 Department of Materials Science and Engineering, Meijo University, Nagoya, Aichi, Japan, 2 21th CENTURY COE Nano Factory, Meijo University, Nagoya, Aichi, Japan
Show AbstractConventional alcohol catalytic chemical vapor deposition (ACCVD) growth of carbon nanotubes (CNTs) have been carried out under ambient gases from 103 to105 Pa. These ambient gas pressures have made it diffuclt to carry out in situ observations using an electron beam during CNT growth, such as scanning electron microscopy (SEM), scanning tunneling microscopy (STM). Therefore, in order to realize the in situ observations and to clarify the growth mechanism of nanotube, CNT growth in a high vacuum is essential. In addition, the effects of residual gases also may be avoided in the growth under high vacuum. In this study, we carried out CNT growth under high vacuum using an alcohol gas source in an ultrahigh vacuum (UHV) chamber and we achieved CNT growth below 400°C without any excitation processes of carbon source.After deposition of Co catalyst of 1 nm in thickness on SiO2/Si substrate, ethanol gas was supplied to the substrate surface through a stainless steel nozzle in the UHV chamber. The growth temperature was monitored by a pyrometer during the growth, and set between 350 and 900°C. The supply of ethanol gas was controlled by monitoring an ambient pressure, which was varied from 1×10-1 to 1×10-4 Pa. The grown CNTs were characterized by SEM and Raman spectroscopy.The G/Si intensity ratio reached its maximum at 700°C, when the pressure was 1×10-1 Pa. The maximum point of the G/Si peak intensity shifted to a lower temperature as the growth pressure decreased. When the pressure was 1×10-4 Pa, the G/Si intensity ratio reached its maximum at 400oC, at which clear RBM peaks were observed in the Raman spectrum. From the RBM peaks, the CNT diameters were estimated to be between 0.9 to 1.7 nm, and CNTs of 1.2-1.4 nm in diameter were dominant at 1×10-1 Pa, whereas thinner CNTs (diameter is below 1.0 nm) were increased with the reduction of the pressure. Our largest G/D ratio was about 40 for the sample grown at 1×10-1 Pa, which is considerably larger than the reported value for the CNTs grown under low pressure. From these results, we conclude that the reduction of the growth pressure lowers the growth temperature. This technique can be applied to in situ observation, and may also be useful for low temperature growth of CNTs, which opens new possibilities for the fabrication of CNT based nanodevices.
5:00 PM - II14.4
Investigating the Growth Process of Vertically Aligned Single-Walled Carbon Nanotubes Synthesized from Alcohol.
Erik Einarsson 1 , Rong Xiang 1 , Kazuaki Ogura 1 , Jun Okawa 1 , Zhengyi Zhang 1 , Shigeo Maruyama 1
1 Mechanical Engineering, The University of Tokyo, Tokyo Japan
Show AbstractWe have carried out a systematic investigation of the influence of various growth parameters on the synthesis of vertically aligned single-walled carbon nanotubes (VA-SWNTs) by the alcohol catalytic chemical vapor deposition (ACCVD) method [1-3]. The growth process of the VA-SWNTs was monitored using an in situ optical absorbance technique [3], which provides a profile of the thickness of the VA-SWNT array vs. CVD time.This growth process was analyzed based on a growth model [4] that has been shown to accurately describe the growth in terms of the initial growth rate, γ0, and the catalyst lifetime, τ. The effects on γ0 and τ of different growth conditions, particularly the synthesis pressure and temperature, were investigated. We found that the ideal pressure for VA-SWNT synthesis is dependent on the growth temperature, shifting toward higher pressure as the growth temperature increases. Our results also show the initial growth rate increases linearly with pressure up to approximately 2 kPa, but decreases at higher pressures. The trend in this higher pressure range is still unclear, but γ0 seems to decrease down to a constant value as the ethanol pressure continues to rise. These findings indicate that, for pressures below 2 kPa, the growth reaction is first-order with regard to pressure, thus the supply of ethanol to the catalyst is the rate-limiting step in the growth process at lower pressures. At higher pressures, however, the rate at which ethanol is supplied to the catalyst is sufficiently fast that the growth becomes limited by a different mechanism.In addition to pressure and temperature, the influence of the ethanol flow rate on synthesis of VA-SWNTs was also investigated. Little difference was found in most cases, but in the extreme case of very low flow (~10 sccm), or no-flow conditions, the VA-SWNT growth was found to occur by a significantly different process, which cannot be described by the standard growth model. This alternative growth process is also investigated. These findings help to clarify some of the many aspects to VA-SWNT synthesis. Additional research is still necessary to determine the details of the catalytic reaction, as well as the mechanism responsible for the diminishing catalyst activity which ultimately inhibits the growth process.[1] S. Maruyama, R. Kojima, Y. Miyauchi, S. Chiashi, M. Kohno, Chem. Phys. Lett. 360 (2002) 229.[2] Y. Murakami, S. Chiashi, Y. Miyauchi, M. Hu, M. Ogura, T. Okubo, S. Maruyama, Chem. Phys. Lett. 385 (2004) 298.[3] S. Maruyama, E. Einarsson, Y. Murakami, T. Edamura, Chem. Phys. Lett. 403 (2005) 320.[4] E. Einarsson, Y. Murakami, M. Kadowaki, S. Maruyama, Carbon (2007) submitted.
5:15 PM - II14.5
Controlling Growth of Carbon Nanotubes for Devices.
John Robertson 1 , Stephan Hofmann 1 , Simone Pisana 1 , C. Wirth 1 , Atlus Parvez 1 , Can Zhang 1 , Alfred Chuang 1 , Guofang Zhong 1
1 Engineering, Cambridge University, Cambridge United Kingdom
Show AbstractCarbon nanotubes have unique properties which may lead to their use in high performance electronic devices such as vias, interconnects and FETs. However, these applications require a much better control of the growth process than presently exists. For Vias formed by a bunch of multi-walled nanotubes, the effective resistance must be reduced to 10 ohms. MWNTs grown by PECVD or CVD are typically grown from a Ni or Fe which has been restructured into a nano-particle from which the nanotube nucleates. But this tends to restrict the site density. On the other hand, FETs require use of only semiconducting single wall nanotubes, which in effect requires some chiral selection, or post-growth separation, which is uneconomic. Both applications place temperature limits on the growth process. We have shown by recent work an improved understanding of the growth process which helps in each of these aspects, such as the ability to grow SNWTs at only 400C by purely thermal CVD [2]. Very high nucleation density and catalyst efficiency of vertically aligned SWNT mats are also required [3]. This work is greatly supported by our in-situ observations of growth as described by Hofmann [4] in this symposium.1 S Hofmann, et al, App Phys Lett 83 135 (2003); J App Phys 98 034308 (2005)2 M Cantoro et al, Nanolett 6 1107 (2006)3 G Zhong et al, Carbon 44 2009 (2006)4 S Hofmann et al, Nanolets 7 602 (2007)
5:30 PM - II14.6
Cutting of Layered Single-walled Carbon Nanotubes: Investigation of Interface Structure and Fabrication of Short Single-walled Carbon Nanotube Arrays.
Takayuki Iwasaki 1 , Hiroshi Kawarada 1
1 , Waseda university, Tokyo Japan
Show AbstractLayered CNTs have been fabricated by several methods. The layered CNTs consist of multiple CNT forests and interfaces between the forests can be observed as white lines by SEM. We showed layered SWNT forests by an intermittent growth method and revealed the root growth mode of SWNTs using the interface between two SWNT layers as a marker [1]. However, the structure of the interface has not been clarified yet. In this study, by cutting the layered SWNTs, we investigated the interface structure and fabricated short SWNT arrays, which are very useful for electronic applications. Radical CVD was used for the growth of vertically aligned SWNTs on Si wafers with a sandwich-like structure of Al (0.5 nm)/Fe (0.3–0.5nm)/Al (5 nm) [2]. Layered SWNTs were fabricated as follows. The substrate was heated at 600 degrees for 5 min for pre-heating, and a microwave power of 60W was applied in a mixture of H2 and CH4 gases for growth of the 1st layer. Then, the plasma and heater were switched off, and the sample was cooled for 5 min, after which the substrate was heated at 600 degrees and the plasma was turned on again to allow the growth of the 2nd layer. The 2nd layer is below the 1st layer because of the root growth mode. We need more than 500 um thick for the 1st layer to cut using a cutter because of hand cutting. By radical CVD, the catalyst lifetime can be active for 30 h and 5 mm long vertically aligned SWNTs can be grown [3], so we synthesized 500 um – 1 mm SWNTs as the 1st layer. After an interval, the 2nd layer with 280 nm – 20 um in length was synthesized. When we press the side of the 1st layer using a cutter very slowly, the layer was peeled off from the 2nd layer. As a result, only the 2nd layer was left on the substrate. Although the top surface of as-grown SWNTs are curved and not vertically aligned because of flexibility of SWNTs, the tip part of the 2nd layer after cutting is straight and vertically aligned. To clarify the tip structure of the 2nd layer, TEM observations were performed. We observed caps at the tips of SWNTs in the 2nd layer. Therefore, SWNTs nucleated again on the particles and grew at 2nd layer growth. SWNTs of the two layers do not connect although the 2nd layer grows from the same catalyst particles as the 1st layer. A SWNT of the 1st layer is on a SWNT cap of the 2nd layer with van der Waals attraction. By decreasing the growth rate of SWNTs, a layer with 200-300 nm in length can be obtained for the 2nd layer. And cutting the 1st layer resulted in fabrication of short SWNT arrays, which cannot be obtained from as-grown SWNTs. This structure has sharp and straight tips. Therefore, we expect that field emission properties and contacts with electrodes for LSI interconnects and three-dimensional transistors would be improved using the straight arrays. [1] T. Iwasaki et al., J. Phys. Chem. B 109, 19556 (2005) [2] G. Zhong et al., Jpn. J. Appl. Phys. 44, 1558 (2005) [3] G. Zhong et al., J. Phys. Chem. B 111, 1907 (2007)
5:45 PM - II14.7
High-Yield Synthesis of Vertically-Aligned Single-Walled Carbon Nanotubes in Ion-Damage and Radical-Damage Free Atmospheric Pressure PECVD.
Tomohiro Nozaki 1 , Kuma Ohnishi 1 , Ken Okazaki 1
1 Mechanical and Control Engineering, Tokyo Institute of Technology, Tokyo Japan
Show Abstract Plasma-enhanced chemical vapor deposition (PECVD) is recognized as one of the viable fabrication techniques of carbon nanotubes (CNTs). However, "CNTs" synthesized in low-pressure PECVD is overwhelmingly carbon nanofibers or multi-walled carbon nanotubes because catalysts and CNTs receive severe damage from ion bombardment: single-walled carbon nanotubes (SWCNTs) has been exclusively synthesized in the thermal CVD regime except a few examples [1,2]. We present atmospheric pressure plasma enhanced chemical vapor deposition (AP-PECVD) for high-purity vertically-aligned SWCNT synthesis, because both ion-damage and radical-damage are preferentially avoided in atmospheric pressure [3]. The SWCNTs were synthesized in the atmospheric pressure radio-frequency discharge (APRFD) reactor that provides spatially uniform non-thermal discharge at 101 kPa [3]. We prepared densely mono-dispersed Fe-Co nanoparticles on 2-inch silicon substrate by dip-coating method [4]. Metallic catalyst particles and bare silicon substrate were isolated by thin alumina layer (20 nm). Typical conditions are as follows: Temperature: 973 K, Pressure: 110 kPa, Power: 60 W, Gas: He/H2/CH4 = 1000/30/16 cm3min-1. Previous study revealed that reactive species created by APRFD promote gas phase chemistry which in turn accelerates carbon precipitation at given conditions. In fact, SWCNTs were not deposited in the thermal CVD regime without APRFD. However, unlike low-pressure plasma condition, reactive species such as CH3 and H produced in the bulk plasma should be consumed at 110 kPa before arriving at catalysts in which SWCNTs grow in the root-growth regime. For this reason, we performed on-line gas analysis using quadrupole mass spectrometer. Thin metallic capillary tube (O.D. 450 μm) was inserted into the cathodic plasma sheath (thickness: 900 μm) and reacting gas was directly extracted for on-line gas analysis. The result showed the main product via CH4 decomposition was C2H6: it is noteworthy that CNTs were missing in the C2H6 thermal CVD at 973 K. We speculate that ionic species such as CH4+, which is one of the abundant reactive species in the plasma, once absorbed on CNT surface and then migrated towards catalyst particles which are anchored on alumina surface. We also studied the effect of total pressure on SWCNT growth. The D/G Raman band peak ratios dramatically increased as total pressure decreased from 110 kPa to 20 kPa, and SWCNTs were no longer synthesized. Because ion-damage was considered negligible at 20 kPa, the CNTs with small D/G ratios were believed to grow in this pressure range. However, excessive supply of reactive species at reduced pressure simultaneously formed amorphous carbon network onto the CNT film that ultimately deteriorates SWCNT yield.[1] T Kato et al, Nanotechnology,17 (2006) 2223.[2] G Zhong et al, J Phys. Chem. B Lett., 111 (2007) 1907.[3] T Nozaki et al, Carbon, 45 (2007) 364.[4] Y Murakami et al, Chem. Phys. Lett., 377 (2003) 49.
II15: Poster Session: Physical Properties and Devices
Session Chairs
Kenji Hata
Annick Loiseau
Yoke Khin Yap
Ming Zheng
Thursday AM, November 29, 2007
Exhibition Hall D (Hynes)
9:00 PM - II15.1
Field-Emission Enhancement Resulting from Self-Assembly of Surface Structures On Ar+ Ion-Irradiated Reticulated Vitreous Carbon (RVC).
Judith Chacon 1 , Charles Hunt 2
1 Chemical Engineering and Materials Science, University of California, Davis, Davis, California, United States, 2 Electrical and Computer Engineering, University of California, Davis, Davis, California, United States
Show AbstractIrradiation of various forms of carbon by Ar+ ions has been shown to result, under certain conditions, in self-assembly of cones, nanowires and nanowhiskers. In this study, Reticulated Vitreous Carbon (RVC), which has been demonstrated inherently as a useful field-emission material, is bombarded with Ar+ ions, producing self-assembling surface morphology changes that further improve the field-emissive properties. Emission is shown to become more uniform, the electric field required for the onset of emission lowers, and the maximum current density increases, compared to other carbon materials. The resultant self-assembled surface features have been observed by SEM, Raman, NMR techniques, and diode-mode field-emission measurements. Field emission improves both by the surface having increased geometric field-enhancement factor as well as because of favorable changes in the sp2- and sp3- bonds at the emission surface. If 10-6 A/cm2 is considered as the onset of emission, non-irradiated RVC requires approximately 4.19 V/μm for emission, whereas even briefly-irradiated (7 min) RVC requires only 1.45 V/μm for emission. Using surface analysis, we show changes in the surface morphology of the RVC evolve with various irradiation times, plasma densities, and acceleration voltages. We show the correlation between these changes and the emission characteristics.
9:00 PM - II15.10
Controlled Placement of Carbon Nanotubes by Spin Coating into SiO2 Trenches.
Paul Hummel 1 , Ramasudhakar Dhullipudi 1 , Tabbetha Dobbins 1 2
1 Institute for Micromanufacturing, Louisiana Tech University, Ruston, Louisiana, United States, 2 Physics, Grambling State University, Grambling, Louisiana, United States
Show AbstractAlthough carbon nanotubes (CNT) have shown to have unique and advantageous electrical and mechanical properties, they have failed to be implemented into new products due to the difficulty in controlling their placement and orientation. This work describes a technique to create controlled structures of CNTs in long trenches. Trenches of various sizes we etched into the silicon dioxide layer of an Si wafer using standard lithography techniques. The trenches vary in length from 20 to 170 um and vary in width from 2 to 8 um. A dispersion of CNTs was created with polyelectrolytes poly(sodium styrene sulfonate) (PSS) and poly(allylamine hydrochloride) (PAH). The dispersion of CNTs was then spin coated onto the wafer with the trenches. Most CNTs collected into the trenches while any CNTs on the surface were removed by centrifugal force. Any CNTs remaining on the surface were removed during the photoresist layer liftoff. The CNTs collected within the microfabricated trenches conformed to bundles which were the exact shape and size of the trench. By controlling where the trenches are created, 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.
9:00 PM - II15.11
A Novel Method for High Rate Manufacturing of Field Effect Transistors (FET) Using Aligned Nanotubes on Flexible and Rigid Substrates.
Prashanth Makaram 1 , Cihan Yilmaz 1 , Sivasubramanian Somu 1 , Anup Singh 1 , Xugang Xiong 1 , Ahmed Busnaina 1 , Yung-Joon Jung 1 , Nick McGruer 1
1 The NSF Nanoscale Science and Engineering Center for , Northeastern University, Boston, Massachusetts, United States
Show AbstractWe present a novel manufacturing approach using aligned Single Walled Carbon Nanotubes (SWNT) to produce high yield field effect transistors (FET) on both flexible and rigid substrates. Electrophoresis is used to direct the assembly of SWNTs and fluidic forces are then utilized to control the orientation of the nanotubes. A simple one mask process is used to fabricate the transistors. The transistors show N-type semiconducting behavior and they can be operated at low gate voltages. This approach has great potential for high-density, large-scale integrated systems based on aligned SWNTs for both micro- and flexible electronics.
9:00 PM - II15.13
Explicit Determination of Various Metal-dependent Contact Properties to Single-wall Carbon Nanotubes.
Minhee Yun 1 , Perello David 1 , Moon Kim 2 , DongKyu Cha 2 , Young Hee Lee 3 , Dong Jae Bae 3 , Seung Yol Jeong 3 , Kang Hee Han 3
1 Department of Electrical and Computer Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States, 2 Department of Electrical Engineering, University of Texas at Dallas, Dallas, Texas, United States, 3 Department of Physics, Sungkyunkwan University, Suwon Korea (the Republic of)
Show AbstractSingle- wall carbon nanotubes (SWCNT), although the subject of hundreds of studies, still have many unknown growth and fabrication difficulties that need addressed if they are to remain an option for replacing CMOS in the next few decades. It is promising, however, that certain growth methods can produce nanotubes with small variation in diameter and primarily semiconducting or metallic tubes. Post growth steps also require better understanding before implementation in chips with large transistor densities. Consistent contacts with small process variation will be needed along with a comprehensive theory on nano-scale junctions.Thus far, it has been realized that contacts differ greatly by metal and deposition methods. Work function appears a primary source of contact differences to SWCNT, but at this point it cannot be assumed the only factor. If a large work function metal were the only requirement, then metals such as Pt, Au, and Ni would consistently produce ohmic contacts to SWCNT; but they do not. Other considerations likely of importance include: fabrication variability, tube diameter and chirality, sample surface dielectric qualities and relation to electric field strength at the contact, or CNT defects at electrode interface.The major flaw of most previous studies is the lack of explicit barrier heights and transport model details. Our method is an attempt to hold as many of the factors noted above constant, while characterizing electrical properties of devices to various transport models including explicit values of the barrier heights, Raman data, and low temperature considerations. Fabrication consists of catalyst and contact pad deposition on a doped silicon wafer with 50 nm of thermal SiO2. Next, semiconducting SWCNT are grown with a PECVD process, and contact electrodes are fabricated with a an e-beam lithography and liftoff process producing drain and source electrodes with channel lengths from 200 nm to around 400 nm. Single tubes can have up to 24 electrodes and six different metals. This is done to hold diameter, fabrication, chirality, and dielectric quality considerations constant in describing transport differences for each metal contact.Our results indicate Cr, Ni, Mo typically fit the standard Schottky model of transport. Other devices fabricated are being characterized and under investigating. The metals under consideration include Mn, Hf, Pt, Pd, Au, Ti, Ni, Cr, Gd and Sn. Based on our experimental results with various metals and device structures, further understanding of contact properties at the metal-CNT interface will be extracted or that a better approach will be formulated to solve any issues in the future CNT device applications.
9:00 PM - II15.14
Junction Effects in Single-walled Carbon Nanotube Thin Film Transistors.
Goki Eda 1 , Giovanni Fanchini 1 , Manish Chhowalla 1
1 Materials Science and Engineering, Rutgers University, Piscataway, New Jersey, United States
Show Abstract9:00 PM - II15.15
The Effect of Film Structure on the Conductivity of Nanotube Films.
Philip Lyons 1 2 , Sukanta De 1 2 , Fiona Blighe 1 , Werner Blau 1 , Jonathan Coleman 1 2
1 School of Physics, University of Dublin, Trinity College, Dublin Ireland, 2 Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), University of Dublin, Trinity College, Dublin Ireland
Show AbstractWe have studied the conductivity of a wide range of different types of single-walled carbon nanotubes (SWNT), functionalized single-walled carbon nanotubes and double wall carbon nanotubes in the form of thin porous films (Buckypaper). Buckypapers were synthesized by filtering nanotube dispersions prepared in different solvents. Resistance of all films was measured by two probe methods and the conductivity of films ranged from 1.5×104 Sm-1 down to 2×102 Sm-1. The film of Hipco SWNT prepared using NMP based dispersions shows the highest conductivity whereas the carboxylic acid functionalized P3 SWNTs (Carbon Solutions Inc) dispersed in DMF shows the highest conductivity (1.3×104Sm-1) among the functionalized nanotubes. The presence of defects in the nanotubes were roughly quantified using the ratio of D band intensity to the G band intensity, (D/G) of Raman spectra. The nanotube bundle size, d, in the films were measured from the SEM images while the film porosity was calculated from the density. Increasing trend of conductivity with (G/D) value was observed, whereas it decreases with increasing bundle size (d) and the porosity (P%) of the films. We have proposed a scaling relation of conductivity with these three parameters as (G/D)/dP , which is in good agreement with our results.
9:00 PM - II15.16
Improved Conductivity of Transparent Single-wall Carbon Nanotube Thin Films via Stable Post-deposition Functionalization.
Bhavin Parekh 1 , Giovanni Fanchini 1 , Goki Eda 1 , Manish Chhowalla 1
1 Materials Science and Engineeing, Rutgers Univeristy, Piscataway, New Jersey, United States
Show AbstractA simple post deposition method for improving the conductivity of transparent and conducting single-wall carbon nanotube (SWNT) thin films via exposure to nitric acid and thionyl chloride is reported. A systematic study on a range of films of variable density and from different commercial sources of SWNTs is performed. The functionalized films possess sheet resistances as low as that of indium tin oxide (ITO) (~30 Ω /square) albeit at lower transmittance (~50%). At 80±5% transmittance, the functionalized films have resistance values ranging from 150 to 300 Ω /square. The SWNT films, however, are more flexible than ITO. Due to this doping effect, a decrease in sheet resistance of SWNT thin films by a factor of five was obtained. Thermo- gravimetric (TGA) and Fourier Transform Spectroscopy (FT-IR) were used to verify that the doping effect on SWNTS. The stability of the functionalized films upon annealing and processing in solvents (water, methanol, and chloroform) is also reported [1].1] Parekh, B. B.; Fanchini, G.; Eda, G.; Chhowalla, M. Appl. Phys. Lett. 2007, 90, 121913.
9:00 PM - II15.17
Factors Controlling the Transmission-Resistance Relationship in Thin Nanotube Films.
Sukanta De 1 2 , Philip Lyons 1 2 , Jonathan Coleman 1 2
1 School of Physics, Trinity College Dublin, University of Dublin, Dublin Ireland, 2 Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, University of Dublin, Dublin Ireland
Show Abstract9:00 PM - II15.19
High Current Stress on Carbon Nanotubes Buckypaper: Scanning Electron Microscopy and Raman Spectra Analysis.
Jin-Gyu Park 1 2 , Shu Li 1 2 , Richard Liang 1 2 , Chuck Zhang 1 2 , Ben Wang 1 2
1 Industrial and Manufacturing Engineering, Florida State University, Tallahassee, Florida, United States, 2 High-Performance Materials Institute, Florida State University, Tallahassee, Florida, United States
Show Abstract9:00 PM - II15.20
Fabrication of Carbon Nanotube Field-Effect Transistors with Metal and Semiconductor Electrodes.
Zhigang Xiao 1
1 Electrical Engineering, Alabama A&M University, Normal, Alabama, United States
Show AbstractCarbon nanotube field-effect transistors (CNTFETs) were fabricated with metal and semiconductor materials as the source and drain materials. Highly-purified HiPCO-grown single-walled carbon nanotubes (CNTs) from Carbon Nanotechnologies, Inc. (CNI) were used for the fabrication of CNTFETs. The single-walled carbon nanotubes were ultrasonically dispersed in toluene, sodium dodecyl sulfate (SDS), and DI water. Dielectrophoresis (DEP) method was then used to deposit, align, and assemble carbon nanotubes (CNTs) to bridge cross the source and drain of CNTFETs to form the channel. The structure of CNTFET has a similar structure of a conventional field-effect transistor with a top gate. Both metals such as gold/titanium and semiconductors such as heavy-doped n-type silicon were used as the source and drain materials. Silicon dioxide was used as the gate oxide. Electron-beam evaporation was used to deposit the thin film layers. Microfabrication techniques such as photolithography, e-beam lithography, and lift-off process were used to define and fabricate the source, drain, and gate of CNTFETs. The gap between the source and drain varied from 2 to 3 um. The developed carbon nanotube field-effect transistors (CNTFETs) can be a good candidate for the application of nanoelectronics and integrated circuits with a high mobility and fast switching. The effects of the junction formed by carbon nanotubes with metal materials on CNTFETs will be compared with those of the junctions formed by carbon nanotubes with semiconductor materials. The fabricated CNTFETs and the electrical characteristics of CNTFETs will be presented in the conference.Acknowledgements: The author thanks NSA for financial support for the research (Grant No.: H98230-07-1-0113).
9:00 PM - II15.21
Electrical Transport Studies of Multi-walled Carbon Nanotube Percolation Networks in Polyimide Nanocomposites.
A. Trionfi 1 , D. Scrymgeour 1 , J. Hsu 1 , M. Arlen 2 , D. Wang 2 , L. Tan 2 , R. Vaia 2
1 , Sandia National Laboratories, Albuquerque, New Mexico, United States, 2 , WPAFB Air Force Research Laboratory, Dayton, Ohio, United States
Show AbstractTransport studies of multi-walled carbon nanotube (c-MWNT)/polymer nanocomposites have shown percolation transport with conductivity σ = σ0(φ-φc)t above the percolation threshold. The conductivity depends on at least three aspects of the conducting network: the conductivity of the constituent c-MWNT and the contact resistance between them, the number of c-MWNT making up the conducting network, and the detailed interconnectivity of the c-MWNT in the conducting network. Using conducting-tip atomic force microscopy, we have studied the density and the conductivity of the c-MWNT conducting network as a function of c-MWNT loading between 0.5 % and 5.0 wt % in polyimide. Preliminary results show that both the areal density of conducting paths and the conductance of these paths increase as the c-MWNT loading increases. Using the Principle of Delesse, the volume fraction of the c-MWNT conducting network can be calculated from the conducting areal density measured by the C-AFM scans. From an estimate of both the constituent c-MWNT conductivity and the volume fraction of the c-MWNT conducting network, we discuss if the arrangement of the c-MWNT conducting network can be inferred. Additionally, a comparison between the C-AFM scans and I-V measurements performed with evaporated metal electrodes will be discussed. Finally, temperature dependent I-V measurements (using the evaporated metal electrodes) between 4 and 300 K show no observable temperature dependence at any loading. However, a polyimide nanocomposite containing 5 wt % functionalized c-MWNT shows both nonlinear I-V characteristics and an increase in conductivity with decreasing temperature. Implications on possible transport mechanisms will be discussed. This work was performed in part at the US Department of Energy, Center for Integrated Nanotechnologies, at Los Alamos and Sandia National Laboratories. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a Lockheed-Martin Company, for the U. S. Department of Energy under Contract No. DE-AC04-94AL85000.
9:00 PM - II15.23
Current Induced Graphitization of Amorphous Carbon Pillar Contained Gallium Nanoparticles.
Toshinari Ichihashi 1 5 , Oleg Lourie 2 , Jun-ichi Fujita 3 5 , Kenichiro Nakamatsu 4 5 , Reo Kometani 4 5 , Shinji Matsui 4 5
1 Nano-Electronics Research Laboratories, NEC Corporation, Tsukuba Japan, 5 , CREST-JST, Kawaguchi Japan, 2 , Nanofactory Instruments AB, Goteborg Sweden, 3 , University of Tsukuba, Tsukuba Japan, 4 , University of Hyogo, Kamigori Japan
Show AbstractIn situ observations of mass transportation of metals using probing system for TEM have been reported by K. Svensson et al. and B. C. Regan et al.. J. Fujita et al. found that a flash motion of gallium droplets with Joule heating transformed an amorphous carbon pillar into multi-walled carbon nanotube. Recently, D. Takagi et al. reported that gold, silver and copper act as catalysts for single-walled carbon nanotube synthesis. The binding energy of carbon for those metals is much smaller than that for iron-family metals. The binding energy of carbon for gallium is also much smaller than that for iron-family metals. So we try to clarify the tubulization mechanism by gallium droplets. Here, we present how amorphous carbon pillars were graphitized and tubulized by Joule heating them in the presence of gallium nanoparticles with in situ STM-STEM. We used a STEM (Hitachi HD-2300) equipped with an in situ probing system (Nanofactory ST1000) for injecting a current to amorphous carbon pillars. The STEM has an electron energy-loss spectrometer (Gatan Enfina). We grew the pillars, which were 100-200nm in diameter and 1000-2000nm long, on a copper by using gallium ion beam induced chemical vapor deposition (FIB-CVD) in a phenanthrene (C14H10) gas atmosphere. A small current injection heated up the pillar slowly, and the gallium clusters grew by coalescing. These gallium droplets escaped at a specific position on the pillar and formed voids at core region of the pillar. The pillar contained a lot of graphitic bubbles. In contrast, a large current triggered the transformation of amorphous carbon pillar into the graphitic tube-like structure. Electron energy-loss spectrum of carbon K-edge revealed that the tublized carbon pillar has a graphitic structure.
9:00 PM - II15.24
The Synthesis and Low Temperature Transport Properties of Graphene Devices.
Adam Friedman 1 , Latika Menon 1 , Sergey Kravchenko 1
1 Physics, Northeastern University, Boston, MA, Massachusetts, United States
Show AbstractThe recent discovery of graphene, composed of an unrolled single-walled carbon nanotube, or single layer carbon atom sheet, and its remarkable properties has lead researchers to contemplate it as a replacement for silicon in the next generation of computer chips. A large amount of theoretical work has been done. But very little experimental work has been done to verify the theory. In this work, we study how to create graphene samples and turn them into devices that will enable us to study the properties of the graphene. We will study the low temperature (down to 50mK) transport properties, magnetotransport properties, and thermodynamic properties. Preliminary results will be presented.
9:00 PM - II15.25
Effect of High-bias and Temperature on the Electrical Properties of C60 Submicron Rods.
Anubha Goyal 1 , Caterina Soldano 2 , Ashavani Kumar 1 , Swastik Kar 1 , Pulickel M Ajayan 1
1 Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States, 2 Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, Troy, New York, United States
Show AbstractThe electrical properties of single crystal C60 are known to reflect a number of phase-transitions below room temperature. However, past studies were performed under low-bias conditions and the possibility of non-linear transport under high electrical fields has not been investigated on crystals of high purity. We present the fabrication, characterization, and high-bias temperature-dependent electrical properties of individual submicron-sized hexagonal rods of C60. These rods were synthesized by liquid-liquid interfacial precipitation methods and characterized by various techniques such as scanning electron and transmission electron microscopy and Raman spectroscopy. The microscopic analysis reveals highly developed crystalline order. Two-probe platinum-contacted devices were fabricated using long (~50-100 µm) individual C60 rods using focused ion beam (FIB) assisted deposition on an insulating (Si/SiO2) substrates. High-bias current-voltage(IV) measurements were performed on these devices in the temperature range of 18K to 300K under an applied voltage of -20V to 20V. Our measurements reveal an overall decrease in conductivity with decreasing temperature, with structures appearing commensurately with the known positions of the phase–transitions. Cyclic high-bias measurements show substantial hysteretic behavior below T~260K, expected from a sudden and large increase in the dielectric constant of the system. The high-bias IV-“loops” show significant non-linearity and asymmetry and the shapes of the “loops” evolve with change in temperature, with sharp changes across the phase transition regions. The observed results are discussed in the framework of various possible scenarios.
9:00 PM - II15.26
Schottky Diodes Using SWNT Networks.
Bryan Hicks 1 , Stephanie Getty 2 , David Allred 1
1 Physics and Astronomy, Brigham Young University, Provo, Utah, United States, 2 Materials Engineering Branch, NASA Goddard Space Flight Center , Greenbelt, Maryland, United States
Show AbstractSchottky diode-like behavior was observed across a network of single-walled carbon nanotubes (SWCNTs) with asymmetric metal electrodes. The network of SWCNTs was grown on a SiO2/Si substrate using catalyst-assisted chemical vapor deposition (CVD). Using shadow masks, two sets of metal electrodes were deposited onto the SWCNT network. Each device was contacted using one gold electrode and one aluminum electrode. This technique, recently reported in the literature, has formerly only been implemented across well aligned, non-networked SWCNTs. Although no effort was made to align the SWCNTs in our devices or to eliminate metallic nanotubes, current rectification was observed in the source-drain bias range of -3V to +3V. The leakage current ranges between 5% and 22% of the current carrying capacities. Maximum forward-biased current capacities between 8 μA and 22 μA have been observed with 136 kΩ to 375 kΩ series resistances, respectively. Efforts to further characterize the electronic nature and optimize the diode response of the network devices will be discussed.
9:00 PM - II15.27
Microwave Rectification by Carbon Nantoube Schottky Diodes.
Enrique Cobas 1 , Michael Fuhrer 1
1 Department of Physics and Center for Superconductivity Research, University of Maryland, College Park, Maryland, United States
Show AbstractWe report the fabrication and electrical characterization of carbon nanotube Schottky diodes (CNT-SDs) via photolithography on high-frequency-compatible substrates using dissimilar contacts of chromium and platinum. The diodes are well-described by the ideal diode equation (n ~ 1.0). DC and low-frequency behavior is compared to a model of a diode in series with a resistor. The diodes rectify microwave signals at 7GHz and 18GHz to produce dc currents of hundreds of nanoamperes. The microwave response is consistent with little or no frequency dependence, indicating the cut-off frequency for the CNT-SD is significantly higher than 18 GHz.
9:00 PM - II15.28
New Electrical Testing Technique for Characterization of Electronic-Grade Carbon Nanotube Aqueous Solutions.
Xuliang Han 1 , Daniel Janzen 1 , Kathleen Greer 2
1 R&D, Brewer Science, Inc., Rolla, Missouri, United States, 2 Center for Applied Science & Engineering, Missouri State University, Springfield, Missouri, United States
Show AbstractCarbon nanotubes (CNTs) are of great interests for a wide range of applications because of their unique structural, mechanical, electrical, optical, thermal, and chemical properties. However, one crucial obstacle to implementing CNT-based applications has been the lack of pure CNTs suitable for direct industrial use. The as-produced CNTs are very fluffy soot, and thus extremely difficult to be handled in the device fabrication process. Although CNTs can be grown directly on a substrate from the catalyst deposited on the substrate surface, the growing temperature is very high, typically greater than 900oC, which represents a big challenge to device fabrication and integration. Another issue is that the catalyst on the substrate surface must be removed without affecting the grown CNTs. In the raw CNT soot, there is always a considerable amount of impurities, including metallic particles from the catalyst and carbonaceous impurities from the chemical reaction by-products. The concentration of metallic impurities is typically 30-50%, whereas the tolerance of metallic particles in a device is extremely tight, because even a small amount can cause many serious problems, such as electrical short and charge accumulation. Amorphous carbon (α-C) is a very common carbonaceous impurity. When the sidewalls of individual CNTs are covered by α-C, significant tube-to-tube barriers are formed, which can tremendously restrict the tube-to-tube carrier transport in CNT thin films. The production of electronic-grade CNT aqueous solutions, which contain only individually suspended pure CNTs without any kind of surfactant, is a critical milestone for implementing CNT-based applications. By using such solutions, pure CNT thin films can be formed through various solution-casting processes, such as spin coating, spray coating, micro-dispensing, and ink-jet printing. At this stage, the trace metals in the solutions can be reduced to < 25 ppb, as measured by Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). The challenge is to quantitatively characterize the carbonaceous impurities in the solutions. For this purpose a new electrical testing technique will be presented in this paper. The procedure starts with forming a CNT thin film on an alumina membrane, which has a nominal pore size of 0.02 μm, by performing vacuum filtration with a certain amount of electronic-grade CNT aqueous solution. Then, the mass (m) and the sheet resistance (Rs) of the obtained CNT thin film are measured with a microbalance and a 4-point probe, respectively. The quantity of m x Rs is proposed as the figure-of-merit to indicate the carbonaceous impurity level. The theoretical background of this technique, its validity regime, and the testing protocol based on this technique will be discussed in this paper.
9:00 PM - II15.29
Bistable Nanoswitch : Fabrication and Characterization.
Sivasubramanian Somu 1 , Tae Kim 1 , Peter Ryan 1 , Xugang Xiong 1 , George Adams 1 , Nick McGruer 1 , Ahmed Busnaina 1
1 Center for High-rate Nanomanufacturing, Northeastern University, Boston, Massachusetts, United States
Show AbstractA non-volatile electromechanical nanoswitch with single wall carbon nanotubes as the switching element has been designed and fabricated using directed assembly. Dielectrophoresis is employed to assemble the carbon nanotubes from an aqueous solution. This nanoswitch uses a two trench approach that allows us to achieve switching between the states at low voltages. The fundamental limits on the dimensions of a nanoswitch for non-volatility are theoretically examined by considering the carbon nanotube as a string with slip between the nanotube and the metal electrodes. Electrical characterization of these carbon nanotubes and their interaction with the metallic electrodes are carried out. The bi-stable characteristics of the nanoswitch and switching between the two states are being studied experimentally.
9:00 PM - II15.3
Improvement of Field Emission Lifetime and Uniformity of Photosensitive Carbon Nanotube Paste by Oxidative Electrical Conditioning.
Hansung Lee 1 , Jihyeon Jeon 1 , Jinhee Kim 1 , Jeungchoon Goak 1 , Naesung Lee 1
1 Faculty of Nanotechnology and Advanced Materials Engineering, Sejong University, Seoul Korea (the Republic of)
Show Abstract9:00 PM - II15.30
Temperature-Dependent Carbon Nanofiber Conductance Model.
Kristofer Gleason 1 , Quoc Ngo 1 , Toshishige Yamada 1 2 , Alan Cassell 2 , Jun Li 2 , Cary Yang 1
1 Center for Nanostructures, Santa Clara University, Santa Clara, California, United States, 2 Center for Advanced Aerospace Materials and Devices, NASA Ames Research Center, Moffett Field, California, United States
Show Abstract9:00 PM - II15.31
Artificial Introduction of Defects in Carbon Nanotubes through Argon and Hydrogen Ion Implantation, and Application to Chemical Sensors.
Jeff Nichols 1 , Prabhakar Bandaru 1
1 Materials Science Program, Department of Mechanical Engineering, UC, San Diego, La Jolla, California, United States
Show Abstract While carbon nanotubes (CNTs) are known to contain various defects that can significantly influence their physical and chemical properties, a systematic investigation of the correlation has not yet been undertaken. The goal of this study is to quantify the effect of defect density on the electrochemical properties of multi-walled CNTs. Consequently, reactive ion etching, with argon and hydrogen (individually), under various conditions of power, pressure, and flow rate has been performed to systematically incorporate defects into vertically aligned MWCNTs. Raman spectroscopy was then used to characterize the amount of disorder within the nanotube samples. The electrochemical behavior of MWCNT samples with different defect densities was then subsequently observed through cyclic voltammetry (CV) measurements. Raman spectroscopy revealed an increase in the disorder in MWCNTs with the introduction of argon and hydrogen, as evidenced by an increase in the ID/IG peak intensity ratio. However, argon is intercalated into the CNTs, and charges the nanotubes (in the form of dangling bonds), while hydrogen treatment terminates residual dangling bonds in the CNTs. We have also seen a corresponding modification of the in-plane nanotube correlation length, from 2- 4 nm, by measuring the area ratios of the Raman peaks. In CV measurements, we have seen that only the Ar treated samples exhibit perfect reversible Nernstian behavior characteristic of ideal electrodes. However, hydrogen treated CNT electrode ensembles seem to exhibit quicker response, as glucose sensors, with exquisite (~ 1 microM) sensitivity. Our research marks an important step towards understanding and controlling defects and improving the performance of nanotubes in chemical and biological sensor applications.
9:00 PM - II15.32
An Ionization-Type Gas Sensor.
Alex Moser 1 , Dan Niebauer 1 , Leonid Grigorian 1
1 , YTC America, Inc., Camarillo, California, United States
Show AbstractAn ionization-type sensor utilizing a shift in breakdown voltage of the sample volume gas was found to be useful for sensing ppm levels of certain analyte gases. Parallel plates comprised of either silicon wafers or carbon nanotube films served as the device electrodes. This simple and robust structure is suitable for helium leak detection, harsh environment, and other gas sensing applications. The breakdown voltage shift sensing mechanism was found to be insensitive at concentrations above 100 ppm of certain analyte gases. However, at analyte concentrations below 100 ppm the sensitivity increased by over an order of magnitude. The study revealed device performance as a function of electrode material and nature and concentration of the analyte gas. Detection of gas breakdown across an electrode gap requires ionization within the sample volume that can lead to a destructive arcing phenomenon. Enhancements to the device electronics enabled the electrodes to withstand thousands of sensor tests with no apparent macroscopic or microscopic damage. Performance of silicon wafer and carbon nanotube electrodes are compared.
9:00 PM - II15.33
Elastic Properties and Morphology of Individual Vapor Grown Carbon Nanofibers.
Joseph Lawrence 1 , Lesley Berhan 2 , Arunan Nadarajah 1
1 Chemical and Environmental Engineering, University of Toledo, Toledo, Ohio, United States, 2 Mechanical, Industrial and Manufacturing Engineering, University of Toledo, Toledo, Ohio, United States
Show AbstractVapor grown carbon nanofibers (VGCNF) are believed to have excellent mechanical properties making them good candidates for fillers in polymer nanocomposites with improved elastic modulus. In order to understand the mechanical properties of the nanocomposite, it is important to measure the elastic properties of individual nanofibers. Although, there are theoretical calculations of elastic modulus reported based on molecular dynamics simulation and continuum mechanics, there have been no experimental measurements of the elastic properties of individual nanofibers. Also, the variety of morphologies that can be present in nanofiber samples, with various orientations of graphite sheets in them, the elastic properties may be quite different for each individual nanofiber.We present a method which not only measures the elastic properties of individual nanofibers accurately and reproducibly, but also determines the corresponding morphology. This method combined Atomic Force Microscopy (AFM), Transmission Electron Microscopy (TEM) and Focused Ion Beam techniques to suspend the nanofibers and measure their deflection, coupled with accurate determinations of inner and outer diameters and morphology using high resolution TEM. To demonstrate its effectiveness, the method was used to determine the elastic modulus of individual VGCNF and their corresponding morphology. Also, the nanofiber can be imaged at high resolution after the loading test to ensure that it was not damaged by the AFM tip during the experiment. The error in measurement of inner and outer diameter of the nanofiber was reduced in this method compared to the earlier AFM only methods. The stress strain behavior of the nanofibers and the variation of elastic modulus with diameter will be analyzed. The paper will also discuss the relationship between elastic modulus and cone angle of VGCNF.
9:00 PM - II15.34
Torsional Electromechanical Quantum Oscillations in Carbon Nanotubes.
Tzahi Cohen-Karni 1 2 , Nagapriya Sethumadhava 1 , Lior Segev 1 , Onit Lavi 1 , Sidney Cohen 3 , Ernesto Joselevich 1
1 Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot Israel, 2 School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States, 3 Chemical Research Support, Weizmann Institute of Science, Rehovot Israel
Show AbstractCarbon nanotubes have unique mechanical and electronic properties, which make them attractive building blocks for nanoelectromechanical systems (NEMS). Due to their high shear modulus and radial isotropy, they are especially suited as torsional springs and rotary bearings for nanoscopic pendulums and rotors. Furthermore, their electronic properties have been predicted to be modulated by torsion, which would enable their use as torsional transducers. Here we study the changes in the conductance of multi-walled carbon nanotubes under varying torsional strain. The results indicate that both the torque and the current are predominantly carried by the outermost wall. Upon increasing torsion, the conductance displays a series of oscillations, which are consistent with a shift of the corners of the first Brillouin zone of graphene across different subbands allowed in the nanotube. Beyond a critical torsion, the conductance irreversibly drops due to torsional failure, which allows us to determine the torsional strength of carbon nanotubes. Our results suggest that carbon nanotubes could be used as electronic sensors of torsional motion in nanoelectromechanical systems.
9:00 PM - II15.35
Ultra Strong Carbon Nanotube Fibers.
Lei Fu 1 , Qingwen Li 1 , Yuntian Zhu 1
1 , Los Alamos National Lab, Los Alamos, New Mexico, United States
Show Abstract9:00 PM - II15.36
Electrothermal Characterization of Metal-Carbon Nanofiber Junctions for Interconnect Applications.
Behrouz Sadrabadi 1 , Toshishige Yamada 1 2 , Drazen Fabris 1 , Jorge Gonzalez 1 , Patrick Wilhite 1 , Cary Yang 1
1 Center for Nanostructures, Santa Clara University, Santa Clara, California, United States, 2 , NASA Ames Research Center, Mountain View, California, United States
Show Abstract9:00 PM - II15.38
Carbon Nanotubes Shortening by γ-Irradiation under Mild Condition.
Chan-Hee Jung 1 , Dong-Ki Kim 1 , Jae-Hak Choi 1
1 , Korea Atomic Energy Research Institue , Jeongeup-si, Jeollabuk-do Korea (the Republic of)
Show AbstractCarbon nanotubes (CNTs) have attracted a considerable attention due to their extraordinary electrical, mechanical, and chemical properties. They have been considered as attractive candidates for various applications such as nanocomposites, displays, sensors, biomaterials, and energy storage. For these applications, short CNTs with small length (shorter than 1 μm) are favorable, but commercially available CNTs are long and entangled, which limits their applications. Various approaches including chemical etching, ultrasonic treatment and mechanical treatment have been developed. Also CNTs were reported to be cut by high energy irradiation as γ-ray and electron-beam. Even though these above-mentioned methods are efficient, they have some drawbacks such as high energy consumption, use of harsh chemicals, or structural damages to CNTs. In this study, we report a milder cutting method of CNTs using γ-irradiation process in aqueous solutions containing hydrogen peroxide, oxygen, or ozone. The cutting process was preformed at various doses. The cutting of the resulting CNTs was confirmed by TEM analysis. Also, the resulting shortened CNTs were characterized by Raman spectroscopy and XPS.
9:00 PM - II15.39
Modification of Y-junction Carbon Nanotube Properties by Focused Ion Beam and Electron Beam with Junction Defect Introduction.
Mariana Loya 1 , Jeongwon Park 1 , Prab Bandaru 1 , Sungho Jin 1
1 Materials Science and Engineering, University California San Diego, La Jolla , California, United States
Show AbstractY-junction carbon nanotubes offer an exciting possibility of nanoscale, self-gated transistors with abrupt switching and logic capabilities.1, 2 We have employed a focused ion beam from ZEISS 1540XB Cross Beam for introducing defects onto the junction portion of Y-Junction carbon nanotubes. Both subtractive and additive processes have been utilized to create or influence the defect morphology and stress state at the junction so that the electronic properties and transistor behavior are modified. Microstructural and electronic properties of such modified Y-junctions as result of the focused ion beam methods will be presented. Some Y-junction nanotubes come naturally with catalyst particles trapped at the very junction, while other Y-junction nanotubes come without trapped nanoparticles at the junction. The effect of the presence or absence of such nanoparticle defects or nano-hole defects on Y-junction properties can significantly affect the transistor properties, and an ability to artificially control such defects is highly desirably. The use of electron beam and high-temperature annealing to introduce junction defects and significant changes in the Y-junction nanotube properties will also be discussed. 1. P.R. Bandaru, C. Daraio, S. Jin, and A. M. Rao, " Electrical Switching Behavior and Logic in Carbon Nanotube Y-junctions", Nature Materials 4, 663 (2005).2. J. Park, C. Daraio, S. Jin and P.R. Bandaru, J. Gaillard and A. M. Rao, "Three-way gating capability of metallic Y-junction carbon nanotubes", Appl. Phys. Lett. 88, 243113 (2006).
9:00 PM - II15.4
Life Testing of Patterned MWCNTs for use as a Field Emitter in a TOF Mass Spectrometer.
Rachael Bis 1 , Stacy Snyder 3 , Bryan Hicks 2 , Jonathon Brame 2 , Stephanie Getty 1 , Todd King 1 , Patrick Roman 1 , David Allred 2
1 , NASA Goddard Space Flight Center, Greenbelt, Maryland, United States, 3 Department of Physics, Lehigh University, Bethlehem, Pennsylvania, United States, 2 , Brigham Young University , Provo, Utah, United States
Show AbstractMulti-walled carbon nanotubes are being evaluated as a field emitter material for the electron impact ionization source for a miniaturized time of flight mass spectrometer. A patterned array of MWCNT towers was grown by thermal chemical vapor deposition to form the cathode of a triode electron emission device. The MWCNTs were grown in vertical towers onto a silicon substrate to a height of approximately 10µm. Life testing was performed with the MWCNT grid using a triode configuration, where the MWCNT cathode is located 200µm from a grid electrode, and transmitted electrons are collected at an anode, 1.6mm from the grid. The cathode was negatively biased, compared to the grid and anode, and the emitted current was collected and measured independently at the grid and at the anode. Fowler-Nordheim tunneling behavior was observed, and a field enhancement factor of 900 was estimated. Life testing studies reveal that current was detectable at both the anode and the grid for over 500 hours. Stable current of 0.3µA was maintained at the anode for the first 350 hours of life testing, with reduced current of 0.06 µA for an additional 150 hours.
9:00 PM - II15.40
Optimization of Photosensitive Carbon Nanotube Paste for Field Emission Applications.
Kim Jinhee 1 , Lee Hansung 1 , Jeon Jihyeon 1 , Goak Jeungchoon 1 , Lee Naesung 1
1 Faculty of Nanotechnology and Advanced Materials Engineering, Sejong university, Seoul, Gunja-dong, Gwangjin-gu, Korea (the Republic of)
Show AbstractCarbon nanotubes (CNTs) have recently drawn strong interest due to their unique characteristics such as diverse electrical properties, high mechanical strength, and chemical stability, together with hollowness and high aspect ratios of extremely small diameters to great lengths. Such superior genetic features of CNTs enable them to be highlighted as one of the best materials ever for field emitters. Many approaches have been attempted to form CNT field emitters, such as screen printing of CNT paste, spaying or spin coating of CNT solution, selective growth of CNTs on substrates, etc, among which the screen printing method has been most widely used for practical applications to CNT-field emission displays or CNT-backlights of thin film transistor liquid crystal displays. This paper presents the fabrication processes and the field emission characteristics of a photosensitive CNT paste and of 10-µm-diameter dot arrays on glass substrates by using screen printing and backside exposure of UV light. We used thin multi-walled CNTs produced by catalytic CVD. The photosensitive CNT paste was fabricated by mechanically homogenizing CNT powders, photo-initiator, photo-sensitizer, acryl binder, and frit fillers in solvent, then followed by repeated three-roll milling for complete mixing and dispersion of ingredients in the polymer vehicle. In the screen-printing method, problematic is the weak adhesion of CNTs to substrate and the non-uniformity of electron emission. The filler was added to the CNT paste to improve the adhesion as well as to regulate the distance between CNT emitters in the dot-patterned arrays for uniform emission. A parametric study was performed on formulating the photo-sensitive paste by changing the amounts of fillers in the range of 5~15% and the powder sizes of fillers by high-energy milling, and the contents of CNTs (0.5~3%) and other ingredients. The compositions and rheological properties of the CNT paste were optimized in terms of field emission characteristics. Field emission measurements were carried out in a vacuum of ~ 5x10-7 torr at a gap of 300 µm between an anode and a cathode. Field emission characteristics were evaluated by voltage-current curves and emission luminous uniformity. This study will present the optimum formula of the photosensitive CNT paste and the excellent emission characteristics of the dot-patterned CNT emitter arrays.
9:00 PM - II15.41
A Single-walled Carbon Nanotube-based Nanocompass for High Spatial Resolution Magnetometry.
Jonathon Brame 1 , Stephanie Getty 2 , Johnathan Goodsell 1 , David Allred 1
1 Physics, Brigham Young University/ NASA, Provo , Utah, United States, 2 , NASA Goddard Space Flight Center, Greenbelt, Maryland, United States
Show AbstractA design for a single-walled carbon nanotube (SWCNT) nanocompass will be presented. The operating principle exploits the sensitivity of SWCNT electrical properties to strain. The sensor design resembles classical compass with electronic readout. The sensor consists of a magnetically responsive, high aspect-ratio Fe component suspended on a free-standing mat of electrically contacted SWCNTs. During operation, torque on the Fe needle will transduce ambient magnetic field strength into an electronic signal. We will discuss fabrication of the magnetometer and preliminary data as well as magnetic field- and temperature-dependence of electron transport measurements and sensitivity calculations.
9:00 PM - II15.43
Redox Chemistry of Single-walled Carbon Nanotubes.
Sandip Niyogi 1 , Stephen Doorn 1 , Sofiane Boukhalfa 1
1 C-CSE, Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show Abstract9:00 PM - II15.44
Aligned Carbon Nanotubes: Electrical and Optical Properties.
Shamim Mirza 1 , Haim Grebel 1
1 Electronic Imaging Center, New Jersey Institute of Technology, Newark, New Jersey, United States
Show Abstract9:00 PM - II15.45
Thermoelectric Properties of Aligned Carbon Nanotube Films.
Shamim Mirza 1 , Haim Grebel 1
1 Electronic Imaging Center, New Jersey Institute of Technology, Newark, New Jersey, United States
Show Abstract9:00 PM - II15.46
Optical Methods for Determining the Flexural Rigidity of Carbon Nanotubes: Experiment and Theory.
Chi-Nung Ni 1 , Christian Deck 1 , Kenneth Vecchio 1 , Bandaru Prabhakar 1
1 Mechanical and Aerospace Engineering, UC San Diego, La Jolla, California, United States
Show AbstractCarbon nanotubes (CNTs) have been predicted to have exceptional mechanical properties and considerable research effort has been expanded to confirm the same. There have been a number of studies reported in the literature to independently determine values of both the modulus (E) and the moment of inertia (I). However, in order to accurately predict the mechanical response of CNTs in deflection and buckling for many applications (nano-electro-mechanical systems, flow sensors, etc.), the product EI (flexural rigidity) is more relevant. In this work, we present a method of measuring the flexural rigidity of CNTs through monitoring their deflection under fluid flow. We conducted measurements on vertical CNTs grown on quartz substrates, arranged in periodic blocks, with lengths of 10-80 micrometers. The deflection of CNTs as a function of fluid flow speed was correlated with measurements of transmitted laser intensity, where a decrease in intensity with increased fluid velocity resulted from the bending of the CNTs. Simulations of this flow were based on the Stokes-Oseen equations with a correction for the small length scales associated with nanotube mats. Drag coefficients (as a function of Reynolds number) were estimated, and the fluid flow force exerted on the tubes was found. The experimental data on the deflections and the estimated force on the tubes from simulations are used for determining the flexural rigidity of CNTs, to be of the order of 10^(-15) Nm^2.
9:00 PM - II15.48
Characterization of the Mechanical Behavior of Carbon Nanotubes during Nanoindentation.
Siddhartha Pathak 1 , Yury Gogotsi 1 , Surya Kalidindi 1
1 Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania, United States
Show Abstract9:00 PM - II15.49
Electromechanical Properties of Nanotube Films.
Evelyn Doherty 1 2 , Jerome Joimal 3 , Sukanta De 1 2 , Philip Lyons 1 2 , Werner Blau 1 2 , Jonathan Coleman 1 2
1 School of Physics, Trinity College Dublin, Dublin Ireland, 2 Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin Ireland, 3 , Hewlett-Packard Limited, Dublin Ireland
Show Abstract9:00 PM - II15.5
Study of Electron Amplified Field Emission from Nanopowder Assisted Microchannel and Vertically Aligned Carbon Nanotubes.
Raghunandan Seelaboyina 1 , Srinivas Bodepalli 1 , Jones Kinzy 1 , Wonbong Choi 1
1 Mechanical and Materials Engineering, Florida International University, Miami, Florida, United States
Show AbstractOne of the most promising industrial applications of carbon nanotubes is in field emission based devices. For utilizing nanotubes as an electron source in high powered microwave devices higher current is required. Emission current from nanotubes can be further amplified by introducing an electron multiplier microchannel plate between the anode and the nanotube cathode. Amplification is achieved by secondary electron generation from the channels of microchannel plate. Recently we have demonstrated this phenomena via a commercial microchannel plate, however the amplification was limited (~7 times) due to the low secondary emission gain of the microchannel plate material. High gain from microchannel plate can be obtained by using high secondary electron yield materials, by increasing aspect ratio (length/diameter) or by applying high voltage. A novel ceramic (alumina) microchannel plate with high secondary emissive yield materials (nano-MgO) has been simulated with above requirements with charged particle optics (CPO), from which channel aspect ratio, tilt, and applied voltages were determined. In this presentation we will discuss the results on our new microchannel plate design (simulation), fabrication, and field emission current amplification from vertically aligned carbon nanotube tower structures and microchannel plate assembly.
9:00 PM - II15.50
Mechanical Properties of Ordered Single Walled Carbon Nanotube Networks.
Vitor Coluci 1 , Nicola Pugno 2 , Socrates Dantas 3 , Douglas Galvao 1 , Ado Jorio 4
1 Applied Physics, State University of Campinas, Campinas Brazil, 2 Department of Structural Engineering, Politecnico di Torino, Torino Italy, 3 Physics Department, Federal University of Juiz de Fora, Juiz de Fora Brazil, 4 Physics Department, Federal University of Minas Gerais, Belo Horizonte Italy
Show AbstractJunctions among single walled carbon nanotubes (SWCNTs) can be produced by introducing pentagon-heptagon pair defects into the hexagonal topology. Two SWCNTs can be welded by electron beam exposure at high temperatures resulting in "X", "Y", or "T"-like stable junctions induced by structural defects created during the beam irradiation. This type of arrangements opens up the possibility of creating carbon nanotube networks.We present here results of classical molecular dynamics simulations of the mechanical response of carbon nanotube networks (CNNs) under different types of mechanical tests. The interactions between carbon atoms were described by the adaptive intermolecular reactive empirical bond-order potential. The CNNs were constructed connecting SWCNTs through Y- or X-like junctions yielding to hexagonal and crossbar networks, respectively. Our results [1,2] showed that CNNs exhibit very high flexibility dependent on the network architectures, showing elasticity modulus ~10-100 GPa and bulk modulus ~10 GPa. Due to the network topology involving SWCNTs and junctions, different response mechanisms under normal deformation for suspended networks are expected. They are associated with the carbon nanotube stretching and nanotube-junction-nanotube angle bending which contribute differently depending on the degree of deformation of the network. Using the same heuristic method for generating SWCNTs from a graphene layer, CNNs can be rolled up to form CNNs with a tubular geometry. The resulting structures, the so-called 'super' carbon nanotubes (STs) [3], which are carbon nanotubes made of SWCNTs. Similarly to a (n,m) SWCNT, [N,M] ST with different chiralities can be constructed. The STs are represented as [N,M]@(n,m) and characterized by: the (n,m) SWCNT used to form them; the necessary junctions to weld consecutive SWCNTs; and the distance between these junctions. From tensile tests of impact loads, we have found that STs are more flexible than the SWCNT used to form them but in some cases they show comparable tensile strengths. The ST Young's modulus have been predicted to have an inverse dependence on the ST radius. During tensile deformations the shape and aperture of pores in ST sidewalls can be modified providing a way to vary the accessible channels to the inner parts of STs through the application of mechanical loads. The ST rupture occurs basically at regions near the SWCNT junctions and it is influenced by the ST chirality. Based on the predicted geometrical and mechanical properties, STs may represent hypothetical candidates for novel porous, flexible, and high-strength materials[1]V. R. Coluci,S. O. Dantas, A. Jorio, and D. S. Galvao, Phys. Rev. B 75, 075417 (2007).[2] V. R. Coluci, N. M. Pugno, S. O. Dantas, D. S. Galvao, and A. Jorio, Nanotechnology - in press.[3] V. R. Coluci, D. S. Galvao and A. Jorio, Nanotechnology 17,617 (2006).
9:00 PM - II15.51
Resilience of Carbon Nanotubes and Their Composites with Nanodiamond in Intense Gamma Radiation Environment.
M. Muralikiran 1 , J. Farmer 2 3 , X. Han 4 , J. Robertson 2 5 , Sanju Gupta 1 2
1 Electrical and Computer Engineering, University of Missouri, Columbia, Missouri, United States, 2 Research Reactor, University of Missouri, Columbia, Missouri, United States, 3 Physics, University of Missouri, Columbia, Missouri, United States, 4 , Brewer Sciences Inc., Rolla, Missouri, United States, 5 Chemistry, University of Missouri, Columbia, Missouri, United States
Show AbstractIn the family of advanced nanocarbons offering multifunctionality, carbon nanotubes (CNTs) are of great interest owing to their unsurpassable physical (mechanical, electrical, thermal, chem./bio.) and structural (high aspect ratio) properties for multiple technological applications [1-4]. It is believed that across the main radiation environments including heavy ions and, gamma and proton irradiation, different types of nanoscale materials may outperform their conventional counterparts, where the improvement is attributed to nanoscale functional entity and its apparent radiation resiliency [1-4]. For ‘harsh’ radiation environment applications, it is critical to demonstrate CNTs structural integrity and performance. We studied both the single- and multiwalled nanotubes (SW and MW) and their composites with ultra-nanodiamond forming true tetragonal-trigonal nanocomposites. Briefly, these materials were spin coated on one inch Si wafers coated with thermally deposited silicon dioxide for adhesion forming thin films. All the samples were subjected to gamma radiation fluxes of 5, 10 and 100 Mrads from 60_Co at a dose rate of ~ 1.5 Mrad/h. They were analyzed prior to and post-irradiation in terms of morphology and microscopic structure using electron microscopy and vibrational spectroscopy (both the Raman and Infrared) to establish the property-structure-processing relationship. Although the structure and dynamics of defects in carbon nanostructures as well as the mechanisms underlying their creation and transformation remain elusive [1-3], this investigation imparts insight into the nature of radiation induced events in nanotubes and nanocomposites for a) short-term space missions; b) radiation hard programmable logic circuits; c) radiation dosimeters, and d) radiation pressure sensors. The results are evaluated in terms of the structural transformation/ irregularities and to identify the radiation interaction mechanism at nanoscale. It is found that the MW nanotubes and their composites are relatively more robust than single-walled and that they reach a state of damage saturation. The findings are discussed in terms of radiation-induced microscopic defects aggregation, bonding re-arrangement, and amorphization collectively known as Wigner effect deduced from the position and intensity of D and G bands in Raman spectra which are also compared with graphite. The author (SG) acknowledges Dr. V. Padalko (Alit Co., Ukraine) for nanodiamond powder. *This work is financially supported in part by MURPI fund administered by the University of Missouri Research Reactor (MURR). [1] S. Gupta, R. J. Patel, N. Smith, Mater. Res. Soc. Symp. Proc. 863, Q6.3-Q6.9 (2005); [2] S. Gupta, R. J. Patel, N. Smith, et. al. J. Mater. Res. 21, 3109 (2006); [3] S. Gupta, N. Smith, R. J. Patel, et. al. Diam. and Relat. Mater. 15, 236 (2006); [4] B.W. Jacobs, V.M. Ayres, M.A. Crimp, et. al. Mater. Res. Soc. Symp. Proc. 851, 287 (2005).
9:00 PM - II15.52
Influence of Alignment on Mechanical Properties of Carbon Nanotube Fibers Prepared by Polymer-free Spinning Process.
Mikhail Kozlov 1 , David Novitski 1 , Ray Baughman 1 , John Fischer 2 , Paul Heiney 3
1 NanoTech Institute, University of Texas at Dallas, Richardson, Texas, United States, 2 Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States, 3 Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania, United States
Show Abstract9:00 PM - II15.53
Thermal Transport in Individual Single-Wall Carbon Nanotubes.
Michael Pettes 1 , Xiaoxia Gao 2 , Jae Hun Seol 1 , Anastassios Mavrokefalos 1 , Choongho Yu 3 , Li Shi 1
1 Department of Mechanical Engineering, University of Texas at Austin, Austin, Texas, United States, 2 Texas Materials Institute, University of Texas at Austin, Austin, Texas, United States, 3 Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show Abstract This work presents an experimental study of phonon transport in individual suspended single-wall carbon nanotubes (SWCNTs). Through the use of a suspended microdevice and transmission electron microscopy, the thermal conductance of three individual SWCNTs and for the first time, the thermal conductivity of one SWCNT have been obtained directly over the temperature range of 100 to 490 K. The thermal conductance shows no signs of Umklapp phonon-phonon scattering and remains approximately proportional to the ballistic conductance throughout the temperature range. The thermal conductivity of a 1.6 nm diameter, 4.72 μm long nanotube was found to increase with temperature as ~T1.5 throughout the temperature range indicating static scattering processes dominate transport in this regime. The measured thermal conductivity is greater than 1000 Wm-1K-1 above room temperature, ranking it among the best thermal conductors known. These results are in keeping with sound theoretical transport studies and are an order of magnitude lower than the predicted ballistic thermal conductance calculated for a defect-free (18,0) nanotube, i.e. the maximum allowable by quantum theory. The results contrast with thermal conductance measurements reported using a high-bias DC self heating method and yield further insight into nanoscale heat conduction mechanisms, providing impetus for further theoretical and experimental studies.
9:00 PM - II15.54
Magnetic Properties and Complex Permittivity and Permeability of Carbon Nanotubes.
Kunlin Wang 1 , Xuchun Gui 1 , Jinquan Wei 1 , Wenxiang Wang 1 , Yi Jia 1 , Feiyu Kang 2 , Jialin Gu 2 , Dehai Wu 1
1 , Key Laboratory for Advanced Manufacturing by Materials Processing Technology of Education Ministry, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China, Beijing China, 2 , Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, China, Beijing China
Show Abstract The magnetic properties and the complex permittivity spectra and complex permeability spectra of Fe-filled CNTs, annealed Fe-filled CNTs and double wall carbon nanotubes (DWCNTs) will be reported in this paper. The Fe-filled CNTs and DWCNTs were prepared by thermal-catalytic chemical-vapor deposition with ferrocene as precursor. The as grown Fe-filled CNTs were annealed for 15 h at 650 centigrade in argon ambient. And we obtained annealed Fe-filled CNTs. Magnetization measurements were carried out on the samples with a vibrating sample magnetometer (VSM) at room temperature. VSM result shows smooth S-shaped magnetization curves of the samples. The coercivity of the three type CNTs are far greater than the value for bulk iron (Hc=1 Oe). The annealed Fe-filled CNTs have stronger coercivity (Hc=520.53Oe) and saturation magnetization (Ms=32.22 emu/g) than as grown Fe-filled CNTs and DWCNTs. We believe that the stronger coercivity resulted from the annealed Fe-filled CNTs contained more ferromagnetic α-Fe. The coercivity and saturation magnetization of DWCNTs are 100.25 Oe and 21.72 emu/g, which resulted from the catalysts that remained in DWCNTs. The complex permittivity and permeability parameters were measured in a frequency range of 2–18 GHz. The magnitude of the permittivity spectra and permeability are steadily decreased with frequency for the three samples. The permittivity value of the annealed Fe-filled CNTs is higher than that of as grown Fe-filled CNTs and DWCNTs. The real permittivity and imaginary permittivity value of the annealed Fe-filled CNTs are about 330-100 and 300-200 between 2 to 6 GHz. The real and imaginary permeability values of the three samples fluctuated between 0.7 to 0.3 and 0.4 to 0.1 in 2-18GHz. The real permeability value of annealed Fe-filled CNTs is slightly higher than that of other samples. The complex permittivity and permeability of the three samples originates from CNTs wall and the ferromagnetic Fe metal catalyst inside the tubes.
9:00 PM - II15.55
Characteristics of Thermal Contact Resistance and Thermal Transport in Suspended SWCNTs Measured using Raman Spectroscopy.
I-Kai Hsu 1 , Rajay Kumar 2 , Adam Bushmaker 2 , Michael Pettes 3 , Todd Brintlinger 4 5 , Michael Fuhrer 4 , John Cumings 5 , Li Shi 3 6 , Stephen Cronin 2
1 Department of Materials Science, University of Southern California, Los Angeles, California, United States, 2 Ming Hsieh Department of Electrical Engineering, University of Southern California, Los Angeles, California, United States, 3 Department of Mechanical Engineering, University of Texas at Austin, Austin, Texas, United States, 4 Department of Physics and Center for Superconductivity Research, University of Maryland, College Park, Maryland, United States, 5 Department of Materials Science and Engineering, University of Maryland, College Park, Maryland, United States, 6 Center for Nano and Molecular Science and Technology, University of Texas at Austin, Austin, Texas, United States
Show AbstractWe investigate thermal transport in suspended carbon nanotubes and measure the ratio of thermal contact resistance to the nanotube intrinsic thermal resistance using Raman spectroscopy. The temperature profile along the nanotube is quantified by G-band Raman downshifts with two different laser powers. By applying the Fourier heat equation, the curvature and offsets of the temperature profile are found to be dominated by the ratio of thermal contact resistance to nanotube intrinsic thermal resistance. According to our model, the phonon transport in suspended nanotubes ~5microns in length is governed by the diffusive transport.
9:00 PM - II15.56
Exfoliation of Graphite Fibers for Enhancing Thermal Contact.
Yoichi Taira 1 , Kuniaki Sueoka 1
1 Tokyo Research Lab, IBM, Yamato Japan
Show AbstractCarbon grapheme based materials such as nanotubes and graphite, show a high thermal conductivity. This makes these carbon based system potentially useful in electronic applications where high thermal conductivity is necessary. In fact, nanotubes and graphite fibers show much higher thermal conductivity than copper or other metals. In the real system, we need to increase the volume density of the carbon material to achieve the high thermal conduction, which makes the graphite fibers more interesting because of their high packing density. Then, the carbon part has to be connected to the other systems usually made of a metal or a semiconductor. But the actual thermal resistance achieved by just contacting the end of the bundle of graphite fibers to a metal surface shows much larger resistance than what we can expect from the conductivity value. This large resistance is caused by the limited contact area of the metal graphite interface. Therefore, the thermal resistance due to the interface can be improved if we increase the contact area. Since a graphite fiber consists of a many layers of graphene structures, the interface contact area can be increased by physically separating the individual layers.We studied the modification of graphite fiber ends in order to improve the thermal contact at the interface. It is shown that the thermal resistance gets smaller when the graphite ends have a lot of branches than when they just end abruptly. We studied the creation of such branched structure by exfoliation of the ends of the graphite fibers. The exfoliation process we used was: 1) The graphite fibers are bundled and glued together by using a polymer adhesive, then the bundle is cut perpendicularly to the fiber direction to make a sheet of aliened carbon graphite fibers. 2) The graphite bundle sheet is then dipped into a nitric acid electrolysis bath. 3) The graphite ends soak up the nitric ions by the electrolysis. 4) After pulling out and drying the graphite sheet, the surface is irradiated with Nd:YAG laser pulses. We examined the conditions of this exfoliation. We confirmed that the graphite fiber ends were exfoliated or branched into many layers by the optical and electron microscopy. We could show the decrease of the thermal resistance by this exfoliation. Once this exfoliated graphite fibers are made, graphite fiber sheet can also be interfaced to a liquid material for the cooling applications.Since graphite fiber are conductive, can be the electrode and the exfoliated graphite fibers can also be interface to liquid or gas, this technique may be applied other electro-chemical system such as batteries or fuel cells in addition to the pure heat conduction applications.
9:00 PM - II15.57
Tensile Modulus of Carbon Nanotube Nano-Fibers Produced by Dielectrophoresis,
Jie Tang 1 , Han Zhang 1 , Pinwen Zhu 1 , Lu-Chang Qin 2
1 , National Institute for Materials Science, Tsukuba, Ibaraki, Japan, 2 Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
Show AbstractContinuous long carbon nanotube fibers with good mechanical stiffness and strength are highly desirable for use in composite materials. We have established a reliable and high throughput dielectrophoretic method to fabricate carbon nanotube fribils at room temperature. An electrical field was used to assist the alignment and assembly of the nanotubes dispersed in a liquid onto the apex of a metallic electrode. The length and orientation of the produced fiber are controlled and predetermined. In this study, we use an atomic force microscope (AFM) to measure the mechanical properties to characterize the radial compressional and tensile moduli of single-walled carbon nanotube nano-fibers produced by dielectrophoresis. The average value of tensile modulus is measured to be 205 GPa, which is higher than those produced by other methods. The tensile modulus of the nano-fibers increases with as the diameter of the nano-fibers decreases. The trend is explained by the changes in dieletrophoretic forces that densify the inter-tubular packing during the spinning process. A tensile modulus of GPa and a packing density of 85% were obtained with a fiber diameter of 55 nm.
9:00 PM - II15.58
Thermal Contraction of Individual Carbon Nanotubes Measured by Electron Diffraction.
Jiong Zhang 1 , Ji Li 3 , Jian-Min Zuo 1 2
1 Materials Science, Univ. Illinois, Urbana, Urbana, Illinois, United States, 3 Nuclear Engineering, University of Illinois , Urbana, Illinois, United States, 2 Materials Research Laboratory, University of Illinois , Urbana, Illinois, United States
Show AbstractUnderstanding the thermo-mechanical properties of carbon nanotubes requires the knowledge of the coefficient of thermal expansion (CTE). Previous X-Ray diffraction result obtained from many multi-walled carbon nanotubes (MWCNTs) shows an averaged thermal expansion along the radial direction [1]. Molecular dynamics simulation results of single-walled carbon nanotubes by different groups conflict with each other showing either thermal expansion or contraction [2, 3]. To resolve this controversy, we measured the thermal expansion of small carbon nanotube bundles and MWCNTs (obtained from the NANOCYL S.A., Belgium) using the nanoarea electron diffraction (NED) mode in a JEOL2010F TEM. Diffraction patterns were recorded from 300 k to 1070 k was using a Gatan heating holder. The electron diffraction patterns were first analyzed to determine the tube structure. We then measure the distances in radial and axial directions, respectively, in the diffraction patterns at different temperatures. And for each temperature the distance is averaged from three diffraction patterns taken separately. After the correction of the tube tilting angle, the measurement was used to calculate the radial and axial CTE. The result shows all these tubes have negative radial CTE from 300 k to 870 k (radial thermal contraction), while from 870 k to 1070 k there is a tendency for thermal expansion. For the axial CTE, the result shows all the tubes measured have a negative axial CTE from 300 k to 1070 k (axial thermal contraction).The radial CTE is on the order of -4×10-5 (k-1) from 300 k to 870 k, while the axial CTE is about -1×10-5 (k-1) from 300 k to 1070 k. Results will be explained based on the existing models and the interatomic potential [4].[1] Y. Maniwa, et al. Phys. Rev. B, 64, 073105 (2001)[2] Y. K. Kwon, S. Berber, and D. Tomanek. Phys. Rev. Lett. 92, 015901 (2004)[3] Chunyu Li and Tsu-Wei Chou. Phys. Rev. B, 71, 235414 (2005)[4] This work is supported by DOE BES
9:00 PM - II15.59
The Magnetic and Transport Properties of Template Synthesized Carbon Nanostructures.
Adam Friedman 1 , Myung Gwan Hahm 2 , Yung Joon Jung 2 , Latika Menon 1
1 Physics, Northeastern University, Boston, MA, Massachusetts, United States, 2 Mechanical Engineering, Northeastern University, Boston, Massachusetts, United States
Show Abstract CNTs prove to be extremely well suited to use to study resistance and electron conduction at the most basic level. Their unique properties can be further enhanced by inserting materials into the cavities of the CNTs. In this study, we use anodized porous alumina templates as a substrate to grow CNTs by CVD. We then use electrodeposition, to deposit Fe, Ni, Co, as well as semiconductor materials and noble metals as wires or nanoparticles. We measure the magnetic properties of the filled CNT arrays. We also form electrical contacts to the CNTs to measure their transport and magnetotransport properties, and the effect of changing diameter at varying temperatures down to 50 mK. Preliminary results will be presented.
9:00 PM - II15.60
Tensile Tests of Individual Carbon Nanotubes.
Weiqiang Ding 1 , Mingyuan Huang 2 , James Hone 2 , Kevin Kohlhaas 3 , Rodney Ruoff 3
1 Dept. of Mechanical Aeronautical & Engineering , Clarkson University, Potsdam, New York, United States, 2 Dept. of Mechanical Engineering, Columbia University, New York, New York, United States, 3 Dept. of Mechanical Engineering, Northwestern University, Evanston, Illinois, United States
Show AbstractNanoscale tensile tests were performed on individual multi-wall carbon nanotubes (MWCNTs) and single-wall carbon nanotubes (SWCNTs) with a custom-made nanomanipulator inside the vacuum chamber of a SEM. Individual CNTs were clamped to an AFM cantilever probe with the electron beam induced deposition (EBID) method, and were loaded in tension until fracture. The AFM cantilever, whose force constant was calibrated before the test with a resonance method, served as the force-sensing element. The applied tensile load was increased in discrete steps, and an SEM image was taken at each loading step. From image analysis the cantilever deflection and the nanotube elongation were obtained for each loading step, and the tensile load and the strain were calculated accordingly. The diameters of MWCNTs were characterized through TEM observation, while the diameter and chirality of each SWCNT were characterized with a Rayleigh scattering method prior to the test. The tensile stress in the nanotube was calculated by using 0.34 nm as the thickness of the shell. A stress/strain curve was thus obtained for each CNTs tested, from which the fracture strength, failure strain, and elastic modulus of each CNTs were obtained. The measured fracture strength values ranged from 10 to 66 GPa for 18 MWCNTs, and 19 to 62 GPa for 15 SWCNTs. The average Young’s modulus of the CNTs measured was around 1 TPa.
9:00 PM - II15.61
Resonant and Broadband Microwave Characterization of Single-Walled Carbon Nanotubes; Anisotropy Issues.
Chinmay Darne 1 2 , Lei-Ming Xie 2 , Divya Padmaraj 1 2 , Paul Cherukuri 3 , Wanda Zagozdzon-Wosik 1 2 , Jarek Wosik 1 2
1 Electrical and Computer Engineering, University of Houston, Houston, Texas, United States, 2 Texas Center for Superconductivity, , University of Huston, Houston, Texas, United States, 3 Department of Chemistry, Rice University, Houston, Texas, United States
Show Abstract9:00 PM - II15.62
Stabilization from Thermal Oxidation of Atomized Cobalt by Multiwalled Carbon Nanotubes.
B. Joshi 1 , N. Rawat 1 , Kalathur Santhanam 1 2
1 Center for Materials Science and Engineering, Rochester Institute of Technology, Rochester, New York, United States, 2 Department of Chemistry, Rochester Institute of Technology, Rochester, New York, United States
Show AbstractA great deal of interest on the interaction of a ferromagnetic atom with carbon nanotube has led to both theoretical (1-4) and experimental (5) investigations in recent times. The experimental work carried out on composited atomized iron and multiwalled carbon nanotubes showed a higher thermal stability for the iron (5) in accordance with the theory that proposes spin transfer in iron from 3d64s2 to 3d84s0 in the nanostructured environment. In this paper we wish to report a thermogravimetric study of compacted atomized cobalt and multiwalled carbon nanotubes. In this system the spin transfer in cobalt from 3d74s2 to 3d94s0 is possible in the presence of carbon nanotubes. Such a spin transfer opens up the possibility of making a new nanostructured material that would have impact in high temperature reactors. We report here the stabilization from the thermal oxidation of atomized cobalt when compacted with multiwalled carbon nanotubes. The thermal oxidation of cobalt was examined by thermo gravimetric analysis (TGA). The atomized cobalt shows thermal oxidation in air at about 275o C and this results in weight gain that is dependent on the temperature; higher the temperature greater is the weight gain. A large number of compacted cobalt-multiwalled carbon nanotubes have been prepared and examined by TGA. They show no weight gain at this temperature; it shows a weight loss of around 600o C that continues till about 800o C. This behavior is dependent on the amount of multiwalled carbon nanotubes in the compact. At mole ratio of multiwaled cabon nanotubes to atomized cobalt of 10 or higher this behaviour is observed. At less than this ratio, partial cobalt oxidation followed by the multiwalled cabon nanotube is observed. The samples were examined before and after the TGA experiments with Scanning Electron Microscope (SEM). The results demonstrate that cobalt is prevented from the thermal oxidation at its virgin temperature due to the protection given by the carbon nanotube nanostructure.1. Fagan, S.B., Mota, R Physical Review B 2003, 67(20), 2054 2. Fagan, S. B., Mota, R., Antonio J. R., Fazzio, A., Physica B:2003, 340-342, 982 3. Weissmann, M., Garcia, G., Kiwi, M., Ramirez, R., Physical Review B: 2004, 70(20), 2014014. Yagi, Y., Briere, T. M., Sluiter, M. H. F., Kumar, V., Farajian, A. A., Kawazoe, Y., Physical Review B 2004,69(7), 75411, 5. Kumar, M., Rawat, N., Santhanam, K.S.V., Effect of nanostructure on the thermal oxidation of atomized iron., Mat.Res. Soc. Symposium, 899E, 0899-N07-01.1, (2006)
9:00 PM - II15.7
Dielectrophoretic Deposition of Carbon Nanotubes with Controllable Density and Alignment.
Jason Moscatello 1 , Vijaya Kayastha 1 , Benjamin Ulmen 1 , Archana Pandey 1 , Yoke Khin Yap 1
1 , Michigan Technological University, Houghton, Michigan, United States
Show AbstractControlled deposition of carbon nanotubes (CNTs) across desired electrodes is important for the fabrication of nanoelectronic devices. Dieletrophoresis has been recognized as a convenient and affordable technique for the deposition of nanotubes and nanowires on electrodes. Although dielectrophresis has been quite well studied for dielectric particles, the application for depositing nanotubes and nanowires are still at the early stage of development. Here, we show that multi-walled carbon nanotubes (MWCNTs) can be deposited by dielectrophoresis with controllable density and degree of alignment. MWCNTs, grown by plasma-enhanced chemical vapor deposition were used. CNTs suspension was prepared by ultrasonication of the MWCNTs in ethanol for 2 hours. An electric field was applied across the electrodes while a drop of CNT/ethanol suspension was introduced on the gap. The field was applied until the suspension was dried. The minimum applied field strength and the AC frequency for CNTs alignment were 1Vpp/μm and 1 KHz respectively. A series of experiments have been conducted. These approaches have enabled the control of the density and alignment of the MWCNTs, which was not reported before. In addition, purification of the MWCNTs was also evidenced. Based on these new understanding, we have also successfully attached individual MWCNTs on AFM tips which may be used for various applications such as high resolution nano-probing, and individual electron field emitter. This work is supported by the U.S. Department of Army (Grant No. W911NF-04-1-0029, through the City College of New York), Defense Advanced Research Agency (Contract No: DAAD17-03-C-0115, through Army Research Laboratory), and the Center for Nanophase Materials Sciences sponsored by the Division of Materials Sciences and Engineering, U.S. Department of Energy (Contract No DE-AC05-00OR22725).
9:00 PM - II15.8
Effect of pH and Solution Conductance on Electrophoretic Directed Assembly of Single-walled Carbon Nanotubes.
Cihan Yilmaz 1 , Prashanth Makaram 1 , Sivasubramanian Somu 1 , Dan Jeannotte 1 , Ahmed Busnaina 1
1 Nanoscale Science and Engineering Center for High Rate Nanomanufacturing, Northeastern University, Boston, Massachusetts, United States
Show AbstractThe effects of pH and solution conductance on the electrophoretic directed assembly of single-walled carbon nanotubes into nanoscale trenches are studied experimentally. Water is used as a liquid medium for suspension solution of SWNTs and pH stability of the solution with respect to time is presented. In addition, the assembly rate as a function of time is studied. Correlation between these parameters is then analyzed for precise controlled assembly of SWNTs to enable high-rate manufacturing process.
9:00 PM - II15.9
Periodically Patterning on Individual Carbon Nanotubes.
Christopher Li 1 , Bing Li 1
1 Materials Sci. & Eng., Drexel University, Philadelphia, Pennsylvania, United States
Show AbstractPeriodic patterning on one-dimensional (1D) carbon nanotubes (CNTs) is of great interest from both scientific and technological viewpoints. Periodically patterned CNTs could directly lead to controlled two-dimensional (2D) or three-dimensional (3D) CNTs suprastructures, an essential step towards building future CNT-based nanodevices. Although both chemical and non-covalent CNT functionalization have attracted extensive attention during the past decades, very few efforts have been dedicated to periodically patterning on individual CNTs. We recently developed a novel “controlled polymer crystallization” method to functionalize CNTs. Using controlled solution crystallization, we were able to obtain polymer single crystals on the CNT templates. The resulting structure is similar to the shish kebab structure formed in flow induced polymer crystallization and is named as nano hybrid shish kebabs (NHSK). In this presentation, we will discuss the crystallization process of the NHSK formation. Solution, thin film crystallization can induce 3D NHSK formation while the physical vapor deposition method can be used to form the 2D NHSKs. The size effect of the CNT on the NHSK formation is significant: for small diameter CNT, orthogonal orientation of the polymer lamellae formed on the CNT while for large diameter carbon nanofibers, the lamellar crystals possess multiple orientations. This was attributed to the size-dempendent soft expitaxy growth mechanism. The periods were found to range from ~ 20 to 150 nm, depending on solution concentration, temperature and molecular weight of the polymers. By using well designed block copolymers, alternating pattering on the CNT templates with a period as small as 8 nanometers has been achieved. These polymer-patterned CNTs can be used to immobilize nanoparticles in a periodic fashion. Hibrid, hierarchically-ordered, CNT-based nanostructures were thus successfully achieved.
9:00 PM - II15: Physical
II15.22 Transferred to B2.1
Show Abstract
Symposium Organizers
Kenji Hata AIST
Annick Loiseau Laboratoire d'Etude des Microstructures (LEM)
Yoke Khin Yap Michigan Technological University
Ming Zheng DuPont Central Research and Development
II16: Biology and Chemistry of Carbon Nanotubes I
Session Chairs
Kenji Hata
Annick Loiseau
Yoke Khin Yap
Ming Zheng
Thursday AM, November 29, 2007
Room 312 (Hynes)
9:00 AM - **II16.1
Biomedical Application of Single-walled Carbon Nanotubes, from In Vitro to In Vivo.
Zhuang Liu 1 , Weibo Cai 1 , Xiaoyuan Chen 2 , Hongjie Dai 1
1 Chemistry, Stanford University, Stanford, California, United States, 2 Medical School, Stanford University, Stanford, California, United States
Show Abstract9:30 AM - **II16.2
Structure and Electrostatics of DNA-CNT Hybrids.
Anand Jagota 1
1 , Lehigh University, Bethlehem, Pennsylvania, United States
Show AbstractHybrids of DNA with carbon nanotubes (CNT’s) have proven to be useful for the dispersion, sorting, and manipulation of the latter. The structure of the hybrid appears to comprise of ssDNA chains wrapped around the CNT cylinder. Hybrids of other chain-like molecules with CNT’s are supposed to have a similar structure. The structure of the hybrid determines its behavior in solution. It thus affects dispersion, separation, and deposition onto a substrate. Using scaling arguments and molecular dynamics simulations we have studied various factors that contribute to the free energy of hybrid formation, including adhesion between DNA bases and the CNT, entropy of the DNA backbone, and electrostatic interactions between backbone charges. MD simulations show that a significant fraction of bases un-stack from the CNT at room temperature, which reduces effective adhesion between the two. For homopolymer wrappings we show that at low ionic strength the dominant influences on the structure are adhesion between DNA and CNT, and electrostatic repulsion between backbone charges on the DNA. With a simple analytical model we show that competition between these two can result in an optimal helical wrapping geometry. We will discuss how the structure and electrostatics of the hybrid influence the ability to sort them and to deposit them on a substrate.
10:00 AM - II16.3
Streptavidin Modified Single Wall Carbon Nanohorns: an Effective Anticancer Drug Delivery System.
Jianxun Xu 1 , Masako Yudasaka 1 , Minfang Zhang 1 , Sumio Iijima 1 2
1 , Japan Science and Technology, c/o NEC, Tsukuba Japan, 2 , 2Meijo University, 1-501 Shiogamaguchi, Tenpaku-ku, Nagoya Japan
Show AbstractSingle Wall Carbon Nanohorn (SWNH) is a new kind of nano-carbon material, which has horn-like structure with 2~5 nm diameter. Usually about 2,000 SWNHs assemble to form an spherical aggregate with diameter of around 80~100 nm.1 The SWNH aggregate emerges as an attractive candidate for a drug delivery system (DDS). It is specially promising to carry an anticancer drug, many of which are not water soluble and highly toxic, to make them effectively delivered, and released in a controlled way.In this study, we incorporated Docetaxel (Doc), an anticancer drug used for stomach cancer, breast cancer, non-small cell lung cancer and so on, into hydrogen peroxide treated SWNHs by modified nano-precipitation method. The weight percent of incorporated Doc is around 20%. Taking advantage of those carboxylic groups on SWNHs, we firstly introduced amine-PEO3-biotin to the conjugate to improve the hydrophilicity. Then, streptavidin, a small protein, was attached on the complex due to the high affinity between streptavidin and biotin. The weight percent of streptavidin is estimated roughly to be 25%. The streptavidin moiety on SWNH makes it easy to attach some other biotinylated peptides/proteins, to introduce more functions to the complex. Furthermore, we investigated the anticancer effectiveness of Doc@SWNH-Streptavidin using a stomach cancer cell line (ATCC NO.: CRL5973). The cytotoxicity experiment was conducted using WST-1 reagent (Figure 1). The cells were incubated with Doc, SWNH-Streptavidin and Doc@SWNH-Streptavidin (~3 ug/ml) respectively for two days. We found that the viability of the cells with Doc@SWNH-Streptavidin decreased dramatically: only 1/3 of that of the cells with SWNH-Streptavidin. It is noteworthy that Doc@SWNH-Streptavidin has a higher cytotoxicity to the cancer cells than Doc itself. These indicate that Doc can be delivered by SWNH-Streptavidin into the cells and the released Doc causes cell death. Thus, we think SWNH-Streptavidin could be an effective DDS.References: 1. S. Iijima, M. Yudasaka, R. Yamada, S. Bandow, K. Suenaga, F. Kokai, K. Takahashi Chem. Phys. Lett., 1999, 309, 165, and therein cited.
10:15 AM - II16.4
Single Stranded DNA Single Walled Carbon Nanotube Hybrids for the Detection of Gaseous Analytes.
Samuel Khamis 1 , Michelle Chen 2 , Robert Johnson 1 , A.T.Charlie Johnson 1
1 Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania, United States, 2 Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States
Show AbstractRecently there has been great interest in sensing strategies based on controlling the chemical affinity of single walled carbon nanotube field effect transistors (SWNT FET’s). The use of many different strategies both covalent and non-covalent has been established. Carbon Nanotubes derive their unique electronic properties partly to their precise atomic structure. Covalent functionalization schemes require altering this structure to attach chemical groups to the sidewalls of the Carbon Nanotube, and thus degrade the electronic properties of the carbon Nanotube. We report here on a means of non-covalently functionalizing carbon nanotubes with short sequences of single stranded DNA (ss-DNA) of ten different varieties in order to tune their chemical affinity. We extend this work to include the functionalization of our devices with single stranded RNA (ss-RNA) by means of the same non-covalent functionalization scheme. We find that our SWNT FET’s show responses to a panel of five different volatile organic analytes via a change in resistance that is specific to both the analyte being tested, and the sequence of the ss-DNA or ss-RNA adsorbed to the device. In this way we have developed a database of responses to ten varieties of ss-DNA and two varieties of ss-RNA that allow us to detect patterns or “footprints” specific to each to the sequence of the strand of ss-DNA in that hybrid, and not merely to the contents of each strand. This observation, and the number of different sequences of ss-DNA or ss-RNA available for a given length, opens up the possibility of creating a large number of sensors with widely varying response characteristics, as required for an “electronic nose” system for the detection and classification of vapor mixtures.
10:30 AM - II16.5
DNA Conformational Changes Induced by Single-Walled Carbon Nanotubes.
Valdirene Peressinotto 1 , Daniel Andrada 1 , Indhira Maciel 2 , Flavio Plentz 2 , Clascidia Furtado 1 , Antonio Claudio Braga 3 , Adelina Santos 1
1 Materials and Nuclear Fuel Division, Centro de Desenvolvimento da Tecnologia Nuclear - CDTN/CNEN, Belo Horizonte, Minas Gerais, Brazil, 2 Department of Physics, Universidade Federal de Minas Gerais - UFMG, Belo Horizonte, Minas Gerais, Brazil, 3 Chemistry Institute, Universidade Estadual de Campinas - UNICAMP, Campinas, Sao Paulo, Brazil
Show AbstractIt has been well documented that single-stranded DNA can bind to carbon nanotube (CNT) surface through π-stacking, resulting in a very stable helical wrapping around the tube [1-4]. This strong interaction makes the DNA/CNT hybrids very promising candidates for a new generation of nanoelectronic devices and nanoscale sensors and for biomedical applications. In addition, DNA wrapping renders CNTs dispersable in water and allows their separation by type [1]. All these applications require a fully understanding of DNA-nanotube interaction mechanism which is still lacking. We have carried a systematic study on the interaction of DNA with carbon nanotubes. In this work we present our findings on the helix arrangement of poly d(GT) and homopolymers of poly dA, poly dC and poly dT around single-wall carbon nanotubes (SWNTs). From our circular dichroim (CD) study, we demonstrate for the first time that purified SWNTs growth by HiPco and laser ablation techniques induce a clear conformational change of GT-DNA oligonucleotides from the right-handed configuration to the left-handed one, without any addition of divalent cations or other chemical species. For homopolymeric single-stranded DNA molecules, the CD results also indicate marked changes on the helical organization. In the particular case of poly dA (pH=8.0), our results indicate a pronounced improvement of the right-handed single-stranded helix form of the oligonucleotide. We further demonstrate that the conformation assumed by the GT-DNA sequences is dependent on the chemical groups attached to the SWNT surfaces and the ionic strength. FT-IR, UV-Vis-NIR absorption and AFM results suggest that carboxylic groups drive the poly d(GT)10 strand to assembly onto the carbon nanotube side-walls without wrap around them. For SWNT-COOH/d(GT)10 solutions the conformational change from right- to left-handed conformation was only observed after the addition of HgCl2. [1] M. Zheng et al., Science, 302, 1545, 2003. [2] H.Takahashi et al., Chem. Phys. Lett., 418, 535, 2006.[3] B. Gigliotti et al., Nano Lett., 6, 159, 2006.[4] J. H. Choi et al., Nano Lett., 7, 861, 2007.
10:45 AM - II16.6
Hydrosilylation on Single Walled Carbon Nanotubes (SWNTs): Conversion of Metallic SWNTs to Semiconducting SWNTs.
Yoonmi Lee 1 , Hyunseob Lim 1 , Ki Seok Jeon 2 , Hyeon Suk Shin 1 , Hye Ryung Byon 1 , Seung Min Jin 2 , Yung Doug Suh 2 , Hee Cheul Choi 1
1 Chemistry, Pohang University of Science and Technology, Pohang Korea (the Republic of), 2 , Korea Research Institute of Chemical Technology, Deajeon Korea (the Republic of)
Show AbstractIn order to realize practical applications utilizing high performance electrical properties of carbon nanotubes, selective growth or separation of semiconducting carbon nanotubes are highly demanded. We introduce a reliable hydrosilylation reaction through which sidewalls of metallic single walled carbon nanotubes (SWNTs) are selectively attacked by various silane compounds, resulting in conversion them into semiconducting SWNTs by opening band gaps. Hydrosilylation has been known to be an efficient pathway to saturate alkynes and alkenes in the presence of Lewis acid catalyst or by photoactivation. In the case of SWNTs, we found that triethylsilane is covalently coupled to benzene backbones of SWNTs at room temperature even in the absence of catalyst or photoactivation. As a control experiment, no covalent coupling has been observed when tetraethylsilane has been reacted. Successful hydrosilylation on SWNTs has been confirmed by examining the SWNT surface using atomic force microscope (AFM) and AFM-correlated Raman spectroscopy by which the degree of sp2 hybridization breakage in a single SWNT has been monitored. Moreover, predominant reactivity for metallic carbon nanotubes has been systematically studied by measuring dramatic electrical transport property changes using SWNT-field effect transistor (SWNT-FET) devices. Compared to the previously reported chemical route that uses diazonium salts as a coupling reagent, the hydrosilylation approach has much wider working reagent (silanes) concentration window.
11:00 AM - II16: BC-C-1
BREAK
II17: Device Integration I
Session Chairs
Kenji Hata
Annick Loiseau
Yoke Khin Yap
Ming Zheng
Thursday PM, November 29, 2007
Room 312 (Hynes)
11:30 AM - **II17.1
Carbon Nanotube LSI via Interconnect Technologies.
Yuji Awano 1 2 3
1 , Fujitsu Laboratories Ltd., Atsugi Japan, 2 , Fujitsu Limited, Atsugi Japan, 3 , MIRAI-Selete, Atsugi Japan
Show AbstractCarbon nanotubes offer unique properties such as highest current density exceeding 1E9 A/cm2, ultra-high thermal conductivity as high as that of diamond, ballistic transport along the tube and extremely high mechanical strength with high aspect ratio of more than 1000. Because of these remarkable properties, they have been expected for use as future wiring materials to solve several problems, for examples, electro-migration, heat removal and fabrication of a small-sized via in future LSIs. In this paper, we demonstrate present status of Multi-walled CNT material technologies and the potential of metallic CNT vias. In particular, we report our original catalytic nano-particle technique for controlling the diameter and density of CNTs. We have succeeded in forming a 40-nm via with the CNT density of 9E11/cm2, which is the highest density ever reported. The low temperature CVD growth and the electrical properties of CNT vias fabricated by a novel damascene process which is mostly compatible with conventional Cu interconnects are also discussed. It was found that the resistance of 60-nm-height vias was independent of temperatures as high as about 400K, which suggests that the carrier transport is ballistic.This work was partly completed as part of the MIRAI Project supported by NEDO.
12:00 PM - II17.2
Controlling the Dielectrophoretic Positioning of Single-Walled Carbon Nanotubes in Device Geometries.
Austin Akey 1 2 , Sarbajit Banerjee 1 2 , Sebastian Sorgenfrei 3 , Inanc Meric 3 , Sami Rosenblatt 1 3 , Brian White 1 4 , Nicholas Turro 4 , Stephen O'Brien 1 2 , Kenneth Shepard 3 , Irving Herman 1 2
1 Nanoscale Science and Engineering Center, Columbia University, New York, New York, United States, 2 Department of Applied Physics and Applied Math, Columbia University, New York, New York, United States, 3 Department of Electrical Engineering, Columbia University, New York, New York, United States, 4 Department of Chemistry, Columbia University, New York, New York, United States
Show AbstractThe precise placement of carbon nanotubes in device geometries is critical for their large-scale integration into the next generation of electronic devices. To controllably position nanotube interconnects and active elements, we use AC voltages to direct the alignment of nanotubes between microelectrodes. By optimizing the electrode geometry, applied voltage and frequency, load resistance, and type of nanotube sample used, we are able to achieve a substantial degree of control over the positioning of nanotubes in field-effect transistor geometries. Wrapping the nanotubes in anionic, cationic, and neutral surfactants and polymers allows the surface charge of the nanotubes to be manipulated, thus providing additional control over the dielectrophoresis of the tubes. The electrophoretic mobility of nanotube colloids is tuned by varying the solution pH, alkyl chain length of the surfactants, and the concentration of the surfactants. This can potentially be used to emphasize the difference in dielectric constant between semiconducting and metallic nanotubes, and thus to obtain some degree of chiral selectivity. Raman spectroscopy is used to probe this selectivity. Also, an in situ detection apparatus is being developed which would use lock-in amplification of an AC signal to detect the presence of individual nanotubes that cross the electrode gap during deposition. This detection system could be used to ensure that only a single nanotube is deposited across the gap, and thus assist in the integration of carbon nanotubes in complementary metal oxide semiconductor (CMOS) circuitry, with many applications in sensing and high-frequency electronics. Approaches for engineering the contacts to obtain optimal contact resistances will also be discussed. This work is primarily supported by the Nanoscale Science and Engineering Center at Columbia University, which is supported by the Nanoscale Science and Engineering Initiative of the NSF under Award Number CHE-0641523.
12:15 PM - II17.3
Real-time Electrical Characterization of Dielectrophoretic Assembly of Metallic Carbon Nanotubes.
Libao An 1 , Craig Friedrich 1
1 , Michigan Technological University, Houghton, Michigan, United States
Show AbstractThe authors report on a method of simultaneously depositing and monitoring dielectrophoretic (DEP) assembly of a small number of metallic carbon nanotubes (CNTs) onto micro-circuit electrodes. The excellent electrical, mechanical, and thermal properties of metallic CNTs make them suitable for nanoelectronics connections. One requirement is the need to assemble single or multiple metallic CNTs between electronic conductors. Among the present manipulation methods, DEP assembly has attracted much research, but confirming the DEP assembly results by scanning electron microscopy is tedious and time-consuming. The goal of this work was to develop a real-time monitoring method of DEP assembly that is simultaneous with CNT deposition. A time-varying impedance model of the electrode gap during CNT deposition was developed to evaluate the number of CNTs which span the gap by measuring the variation of gap impedance during the DEP. A HP 4284A precision LCR meter was used to generate an AC electric field while simultaneously measuring the impedance variation across the electrode gap. This reduces the requirement of SEM inspection and could help automate DEP assembly of CNTs.The DEP assembly process has a parallel resistance- capacitance equivalent circuit. Based on the literature, gap resistance may be several kilo-Ohms to several mega-Ohms when only one CNT is bridging the electrode gap, depending mainly on the contact resistance. The gap resistance is taken to be infinite when no CNTs are spanning the gap. During DEP, one CNT first deposits and bridges the electrode gap, then a second, third, and so forth According to our calculations, the precision LCR meter will detect the corresponding variations in the gap impedance and/or gap resistance indicating how many CNTs are bridging the gap. If too many CNTs are bridging the gap, the instrument may not recognize the number due to insignificant variation of gap resistance or impedance. We have experimentally determined the gap impedance when only CNT is bridging the electrode gap. Based on the model, we have determined the number of CNTs connecting the electrode pair by measuring the gap impedance variation during the assembly.We have performed experimental tests on this monitoring method and the expected results have been obtained, showing nearly instantaneous drops in gap impedance as each CNT bridges the gap. The number of CNTs bridging the gap has been confirmed by SEM images. The paper will present the models, predicted impedance drops, experimental setup, and results of a large number of CNT assembly and monitoring tests by this method.
12:30 PM - II17.4
Deposition and Meniscus Alignment of DNA-CNT On a Substrate.
Constantine Khripin 1 , Ming Zheng 2 , Anand Jagota 1
1 Chemical Engineering, Lehigh University, Bethlehem, Pennsylvania, United States, 2 , DuPont, Wilmington, Delaware, United States
Show AbstractWe present a study of deposition and meniscus alignment of DNA-carbon nanotube (DNA-CNT) hybrids on a silicon wafer coated with an alkyl-silane monolayer. We show that this process occurs in two stages: adsorption of DNA-CNT onto the hydrophobic surface and subsequent alignment by a passing meniscus. In our work we study how the pH, ionic strength, and time affect the density of nanotubes deposited on the surface. We also study how surface density of nanotubes and the speed of the meniscus motion affect alignment of nanotubes. Experimental results are interpreted using models for the kinetics of deposition and for forces that affect alignment by the meniscus. We show that this deposition and alignment process can be used to generate spatially varying surface patterns that may be useful for applications that require targeted placement of nanotubes on a surface.
12:45 PM - II17.5
Vertically Suspended Carbon Nanotube Network Junctions.
Byung Yang Lee 1 , Kwang Heo 1 , Seunghun Hong 1
1 School of Physics and Astronomy and NANO Systems Institute, Seoul National University, Seoul Korea (the Republic of)
Show AbstractLaterally-suspended carbon nanotube (CNT) devices have been utilized for various applications such as resonators, transistors, sensors, etc. However, it is still difficult, if not impossible, to prepare vertically-suspended CNT devices. Herein we report, for the first time, the fabrication of vertically suspended carbon nanotube (CNT) network junctions and present several applications.In this device, vertically-suspended CNT network with well-defined geometry connects two vertically-arranged electrodes. In our fabrication method, “surface-programmed assembly” method was utilized on a substrate with pre-patterned sacrificial patterns. Here, surface molecular patterns guided the ‘selective assembly’ and ‘precision alignment’ of CNTs on the substrate without using any external forces such as liquid flow, electric field, etc. After CNT assembly, electrodes were formed and the sacrificial structure was removed.Using our device, we demonstrated ammonia gas sensing. Furthermore, we also used the device for electromechanical sensing, where a mechanical stimulus to the top electrode was detected by measuring the current change through the vertically-suspended CNT channel.As far as we know, this is the first report on vertically-suspended CNT networks between two electrodes, and it should open a wide range of applications in nanoelectronics and nanobiotechnology.
II18: Device Integration II
Session Chairs
Kenji Hata
Jing Kong
Annick Loiseau
Yoke Khin Yap
Ming Zheng
Thursday PM, November 29, 2007
Room 312 (Hynes)
2:30 PM - **II18.1
Chirality-resolved Single-walled Carbon Nanotubes: Processing, Characterization, and Applications.
Mark Hersam 1
1 Materials Science and Engineering, Northwestern University, Evanston, Illinois, United States
Show AbstractThe utilization of single-walled carbon nanotubes (SWNTs) in large quantities for molecular electronics, optoelectronics, biosensors, and medical applications will require SWNTs of the same physical structure, electronic type, and band gap. Since current methods of synthesis produce mixtures of nanotubes with different physical structures and electrical properties, the development of strategies for the post-production separation of these one-dimensional materials is highly desirable. In this work, we demonstrate a scalable method for separating SWNTs by their diameter and electronic type (i.e., semiconducting versus metallic) using density gradient ultracentrifugation (DGU). Since DGU is a technique commonly utilized in biochemistry to separate and isolate different sub-cellular components, DNA from RNA, and even different sequences of DNA by their compositions, we initially focused on the bulk sorting of DNA wrapped SWNTs in aqueous density gradients [1]. This process led to enrichment of SWNTs by diameter - especially in the small diameter regime (i.e., SWNT diameter = 0.7 – 1.0 nm). However, DNA wrapping possessed several undesirable characteristics including prohibitive expense in large scale production, irreversible wrapping, and inefficient wrapping for SWNTs with diameters exceeding 1 nm. Consequently, subsequent work has focused on DGU of surfactant encapsulated SWNTs [2]. In particular, bile salt surfactants, such as sodium cholate (SC), have overcome the drawbacks of DNA. Furthermore, additional control over the density-structure relationship has been achieved by using co-surfactant mixtures of SC and sodium dodecyl sulfate (SDS). For example, highly efficient metal versus semiconductor separation has been achieved with SDS and SC co-surfactant mixtures. Characterization of the resulting sorted SWNT samples includes optical absorption spectroscopy, photoluminescence spectroscopy, Raman spectroscopy, atomic force microscopy, and direct charge transport measurements. Since DGU produces relatively large quantities of monodisperse SWNTs, this talk will conclude with our most recent efforts to realize enhanced performance in SWNT devices, such as thin-film field effect transistors and transparent conductors, using SWNTs sorted by DGU.[1] M. S. Arnold, S. I. Stupp, and M. C. Hersam, "Enrichment of single-walled carbon nanotubes by diameter in density gradients," Nano Letters, 5, 713 (2005).[2] M. S. Arnold, A. A. Green, J. F. Hulvat, S. I. Stupp, and M. C. Hersam, "Sorting carbon nanotubes by electronic structure via density differentiation," Nature Nanotechnology, 1, 60 (2006).
3:00 PM - II18.2
Chemical Functionalization for the Selective Placement and Separation of Single-Walled Carbon Nanotubes.
George Tulevski 1 , Ali Afzali 1 , James Hannon 1 , Phaedon Avouris 1
1 IBM Research Division, T.J. Watson Research Center, Yorktown Heights, New York, United States
Show AbstractSingle-Walled Carbon Nanotubes have attracted enormous interest for use as the active channel in electronic devices due to their outstanding transport properties. A major hurdle in the fabrication of such devices is the development of chemical tools to address major processing challenges such as selective placement and separation by electronic type. This work will highlight recent progress in the chemical functionalization of SWCNTs, both to facilitate selective placement into predefined positions on gate oxide surfaces and for their separation by electronic type. SWCNTs are first chemically functionalized with hydroxamic acid terminated organic compound that selectively binds to metal oxide surfaces (i.e. HfO2, Al2O3). Electron beam lithography is then employed to pattern narrow HfO2 trenches into which the functionalized SWCNTs selectively bind. Source and drain electrodes are then fabricated along the defined trenches to contact the SWCNTs, with the underlying HfO2 trench acting as the gate dielectric. The side walls of the patterned trenches induce alignment of the SWCNT along the length of the trench, allowing for ease in contacting either ends of the SWCNTs. The surface functionalization is spectroscopically shown to be fully reversible. Once the nanotubes are assembled into the trenches, the molecules are then removed leaving the unfunctionalized SWCNT behind with the same electrical properties as prior to functionalization. This technique allows for hundreds of working devices to be fabricated with high yield (~90%). The electrical properties of the subsequent devices are excellent, showing no deterioration of the electrical performance as a result of the placement process. This functionalization method is also shown, under certain conditions, to facilitate the separation of carbon nanotubes by electronic type. The reaction selectivity is confirmed both spectroscopically and by the fabrication of electronic devices. Since the functionalization succeeds in both the selective placement and separation of SWCNTs, it provides a potentially powerful tool for the fabrication of carbon nanotube electronics.
3:15 PM - II18.3
Self-sorted SWNTs for High On/off Ratio Thin Film Transistors.
Melburne LeMieux 1 , Soumendra Barman 1 , Zhenan Bao 1
1 Chemical Engineering, Stanford, Stanford, California, United States
Show AbstractUnderstanding the nature of the interaction between nanotubes and individual chemical functional groups is a prerequisite for the rational engineering of the future generations of sensors, computing networks, and nanoelectronics. This is just one of the issues of SWNT processing impeding large-scale, solution processed integration, along with reliable device fabrication including reproducible alignment and concentration of the nanotube network in SWNT high performance thin film transistors (TFTs). In this vein, we will present our work demonstrating how to separate SWNTs while simultaneously fabricating the SWNT network TFT and controlling density and alignment in a single step for reproducible devices. This is critical for the development of high performance, low voltage transistors in which an optimal alignment of SWNT can lead to an optimal number of inter-tube contacts thereby optimizing the contact resistance/charge transport relationship. However, even after alignment and concentration issues have been resolved, the major shortcoming of SWNT network TFTs is poor on/off ratio due to a chirality mixture always found in bulk SWNT solutions. Thus, chirality must be sorted to realize high performance SWNT electronics either by a self-sorting mechanism during fabrication of the TFT, or by post-treatment. The former is ideal, but not yet realized. We demonstrate a novel approach for sorting SWNT with molecularly thin functional nanolayers, and show high performance thin film transistors using the ‘self-sort’ nanotube network.
3:30 PM - II18.4
Transfer Printing of Massively Aligned Single-Walled Carbon Nanotubes for Nanoelectronics and Chemical Sensing.
Koungmin Ryu 1 , Fumiaki Ishikawa 1 , Nishant Patil 2 , Alber Lin 2 , Alexander Badmaev 1 , Lewis Gomez 1 , Akshay Kumar 1 , Pochiang Chen 1 , Subhasish Mitra 2 , H. S. Philip Wong 2 , Chongwu Zhou 1
1 Electrical Engineering, University of Southern California, LA, California, United States, 2 Electrical Engineering, Stanford University, Stanford, California, United States
Show AbstractSynthesis and manipulation of massively aligned single-walled carbon nanotubes are important steps for various applications, including high performance carbon nanotube integrated circuits and chemical / biosensor arrays. Previously we have successfully developed the synthesis of massively aligned carbon nanotube arrays on a-plane sapphire and quartz substrates, with nanotube lengths exceeding 200 um and diameters ~ 1-2 nm. In this talk we will present our recent advance on transfer printing of aligned nanotubes from the original sapphire/quartz substrates to virtually any other substrates, including glass, silicon, polymer sheets, and even fabrics. In addition, we have obtained sophisticated carbon nanotube networks by performing multiple transfers of nanotubes onto the same substrate at several orientations. The nanotube network transferred to quartz substrates was found to alter the quartz surface from hydrophilic to hydrophobic, while nanotube networks transferred to PET substrates were observed to be highly conductive, transparent, and flexible as well. Furthermore, based on transferred nanotube arrays on various substrates, we have successfully demonstrated nanotube transistors with on/off ratios ~ ten thousands, and chemical sensors for low-concentration nitrogen dioxide and 2,4,6-trinitrotoluene. This transfer printing technique may prove valuable for nanotube flexible electronics, and hybrid integration of aligned nanotubes with silicon electronics.
3:45 PM - II18.5
Transfer of Large Area Graphene Sheets from Carbonized 6H-SiC by a Direct Bonding Technique.
Akihiro Hashimoto 1 , Kousuke Iwao 1 , Satoru Tanaka 2 , Akio Yamamoto 1
1 Electrical & Electronics, University of Fukui, Fukui Japan, 2 Applied Quantum Physics and Nuclear Engineering, Kyusyu University, Fukuoka Japan
Show AbstractIt is very important to obtain a large area graphene region on a substrate such as SiO2/Si for progress of research of the graphene electronics. Until now, we have been able to obtain only about 100 square micron graphene region on the SiO2/Si substrate at maximum by the conventional methods. In the present paper, we have proposed a new formation method of a large area graphene sheet on SiO2/Si substrate, including a transfer method of the graphene sheets from the carbonized 6H-SiC substrates to SiO2/Si substrate by a direct bonding technique. The graphene layer formed on the 6H-SiC substrate is basically possible to be prepared to have considerably large area with atomically flat surface morphology. Therefore, it is expected that the proposed approach has a great advantage for the formation of the large area graphene sheet against to the conventional ones such as Scotch-tape method using HOPG. Moreover, the new approach also will be able to be extended easily to the device fabrication process to prepare selectively the graphene area arranged on the SiO2/Si substrates by including some modified processes of the direct bonding technique and/or the well-established semiconductor fine–pattern process like MEMS techniques.In the proposed method, a carbonized-layer on the 6H-SiC formed by rapid thermal annealing in a vacuum was used as the seed of the graphene sheets. (1) The graphene sheets formed on the SiO2/Si substrates was characterized by the interference optical microscope (IOM), the atomic force micro-scope (AFM) and Raman scattering spectroscopy (RSS). Typical IOM viewgraph of the graphene transferred region shows the successful transfer of the carbonized layer from the SiC to the SiO2/Si substrates. The opposite pattern was also observed on the annealed SiC substrate after the transfer. As the result of the new method, we have achieved the formation of the considerably large area graphene regions about 10 square mill-meters. From the Raman measurements, the transferred regions have been including the mono-layer and/or the several mono-layers graphene regions. If we will have larger and uniform area of the graphene sheets on the SiC substrates, we will be able to have the larger and more uniform transferred graphene area on the SiO2/Si, basically.We have successfully achieved the formation of the large area graphene regions about 10 square mill-meters by the new transferred method, and it will be possible to form the graphene area selectively as desirable special arrangement on the SiO2/Si substrate for the integrated carbon electrical circuits.Reference (1)K. Hayashi, S. Mizuno, S. Tanaka, H. Toyoda, H. Tochihara and I. Suemune, JJAP (Express Lett.) 44, L803 (2005).
4:00 PM - II18: Device 2
BREAK
II19: Biology and Chemistry of Carbon Nanotubes II
Session Chairs
Kenji Hata
Annick Loiseau
Yoke Khin Yap
Ming Zheng
Thursday PM, November 29, 2007
Room 312 (Hynes)
4:30 PM - **II19.1
Physical and Biological Studies of Single-Walled Carbon Nanotubes using Near-infrared Fluorescence.
R. Bruce Weisman 1
1 Dept. of Chemistry, Rice University, Houston, Texas, United States
Show AbstractThe intrinsic near-IR fluorescence of semiconducting single-walled carbon nanotubes (SWNTs) provides an increasingly useful tool for basic and applied research. Current studies will be illustrated by two project themes. In one, near-IR fluorescence microscopy is used to image segments of individual SWNTs while they are exposed to chemical reactants that quench the emission. Stepwise changes in emission intensity are clearly observed and identified as single-molecule reaction events. Analysis of the step heights reveals that each sidewall reactive event quenches excitons in a ~90 nm region of the nanotube surrounding the reaction site. This distance appears to be independent of SWNT (n,m) identity and is interpreted as the mean diffusional range of excitons as they undergo a one-dimensional random walk. Further studies will be described in which the chemical reaction sites are mapped with sub-diffraction resolution. A second project theme involves the use of near-IR fluorescence in developing SWNT biomedical applications. Here, rabbits were given i.v. injections of nanotubes suspended in biocompatible surfactant. Fluorimetric analysis was then used to monitor the concentration of SWNTs in the blood as a function of time after injection. Simple first-order decay was found with a circulation half-life of 1.0 hours. Near-IR fluorescence microscopy of tissue samples collected 24 hours after injection showed detectable nanotube concentrations only in the liver. Finally, progress will be reported on efforts to develop fluorimetric analysis into a quantitative tool for studying SWNT biodistributions and clearance in mammalian model systems.
5:00 PM - **II19.2
Optical Modulation of Single Walled Carbon Nanotubes: Fundamentals and Biomedical Applications.
Michael Strano 1
1 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show Abstract5:30 PM - II19.3
Novel Optoelectronic Transport Studies of Supramolecular Nanotube Assemblies.
Harsh Chaturvedi 2 , Jordan Poler 1 2
2 Center for Optics and Optoelectronics, University of North Carolina at Charlotte, Charlotte, North Carolina, United States, 1 Chemistry, UNC Charlotte, Charlotte, North Carolina, United States
Show AbstractSingle Walled Carbon Nanotubes (SWNT) are important materials for future devices and sensors. New-age optoelectronic devices can be made from assemblies of diverse nanostructured materials and SWNTs, providing enhanced functionality. Ruthenium complexes have very strong absorbance in the visible spectrum. SWNTs have exceptional electron accepting and charge transfer properties. We have shown specific binding of these complexes with the end of SWNTs. Properties of these supramolecular nano-assemblies are being investigated to develop applications like sensors and photovoltaic cells. Photon enhanced aggregation properties of SWNT due to these ruthenium complexes are demonstrated. These coordination-complex based molecular adsorbates onto the nanotubes affect the field effect transistor response of SWNTs. Ruthenium centered phenanthroline complexes exhibit a strong metal to ligand charge transfer. We believe that the nanotube quenches charge from the ligand after the complex has been optically excited. This results in optically altering the carrier density, and therefore the transport properties of the nanotubes. We believe this is due to charge transfer from the metal center through the ligand and finally onto the nanotubes. The devices have been fabricated using e-beam and conventional lithography. Photon induced affects on the charge transport are shown. These devices were imaged using atomic force microscopy, and scanning electron microscopy. Spectroscopic analyses of these devices are also shown. Advancements towards realizing real-time optoelectronic sensors and nano devices are demonstrated.
5:45 PM - II19.4
Biomolecular Functionalization of Carbon Nanotubes Using Closeable Cyclic Peptides and Other Designed Peptide Systems.
Gregg Dieckmann 1 2 , Ray Baughman 1 2 , Jonathan Coleman 3 , Alan Dalton 4 , Rockford Draper 1 2 5 , Inga Musselman 1 2 , Paul Pantano 1 2
1 Chemistry Department, The University of Texas at Dallas, Richardson, Texas, United States, 2 The NanoTech Institute, The University of Texas at Dallas, Richardson, Texas, United States, 3 Physics Department, Trinity College, Dublin Ireland, 4 Physics Department, University of Surrey, Guildford, Surrey, United Kingdom, 5 Department of Molecular & Cell Biology, The University of Texas at Dallas, Richardson, Texas, United States
Show AbstractII20: Poster Session: Biological and Chemical Properties and Devices
Session Chairs
Kenji Hata
Annick Loiseau
Yoke Khin Yap
Ming Zheng
Friday AM, November 30, 2007
Exhibition Hall D (Hynes)
9:00 PM - II20.1
One Dimensional Nanoarchitectures and Electronic Functionality.
Cengiz Ozkan 1
1 Mechanical Engineering, University of California at Riverside, Riverside, California, United States
Show Abstract9:00 PM - II20.10
Separation of Metallic Single Wall Carbon Nanotubes by Soluble Pentacene Derivative.
Cai-Hong Liu 1 , Yi-Yang Liu 1 , Hao-Li Zhang 1
1 State Key Lab of Applied Organic Chemistry, Lanzhou University, Lanzhou China
Show Abstract9:00 PM - II20.11
Separation of Metallic and Semiconducting HiPco Single-Walled Carbon Nanotubes Utilizing Their Density Differences Induced by Selective Functionalization.
Woo-Jae Kim 1 , Chang Young Lee 1 , Michael Strano 1
1 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractDiazonium salts, which selectively functionalize metallic single-walled carbon nanotubes (SWNT) over semiconducting in SWNT mixtures, can increase the SWNT densities on which diazonium salts are chemically attached. We applied this concept for separating the functionalized SWNT from nonfunctionalized using density-induced centrifugation. The SWNT mixtures, in which metallic SWNT were selectively functionalized over semiconducting by 4-hydroxybenzene diazonium salts, were separated into two distinct fractions after centrifugation: one moved to the top layer and the other moved to the bottom layer depending on the existence of functional groups on SWNT. UV-Vis-nIR absorption spectra and the changes of area ratio for disorder over tangential mode in 633nm-Raman spectra revealed that the top layer was enriched in nonfunctionalized-semiconducting SWNT, while the bottom layer was enriched in functionalized-metallic SWNT. These results indicate that functionalized SWNT become more dense than nonfunctionalized, due to the diazonium functional groups attached to SWNT, and are separated from SWNT mixtures. We also demonstrate that the purity of separated SWNT can be controlled by adjusting reaction selectivity and measure the electrical properties of these separated SWNT.
9:00 PM - II20.12
A Structure-Reactivity Relationship For Single-Walled Carbon Nanotubes Reacting with 4-Hydroxybenzene Diazonium.
Nitish Nair 1 , Woo-Jae Kim 1 , Monica Usrey 1 , Michael Strano 1
1 Chemical Engineering Department, MIT, Cambridge, Massachusetts, United States
Show Abstract9:00 PM - II20.13
Processing of High-Purity Single-Walled Carbon Nanotubes as Standard Reference Materials and Conductive Thin Films.
Bin Zhao 1 , Hui Hu 1 , Alex Puretzky 1 , David Styers-Barnett 1 , Ilia Ivanov 1 , Christopher Rouleau 1 , David Geohegan 1
1 , Oak Ridge National laboratory, Oak Ridge, Tennessee, United States
Show Abstract9:00 PM - II20.14
Tailoring Nanotube Dispersion with pH-Responsive Polymers.
Jaime Grunlan 2 1 3 , Lei Liu 1
2 Mechanical Engineering, Texas A&M University, College Station, Texas, United States, 1 Materials Science and Engineering, Texas A&M University, College Station, Texas, United States, 3 Chemical Engineering, Texas A&M University, College Station, Texas, United States
Show AbstractCarbon nanotubes are an exciting material due to their small size, high modulus, and high intrinsic conductivity. As a result, nanotubes hold significant promise for imparting electrical conductivity, mechanical strength, and thermal conductivity to polymeric materials. Despite this potential, the ability to control the dispersion and microstructure of nanotubes in solvents and solid composites remains a significant hurdle to their widespread use. The present work demonstrates a method to control the dispersion of single-walled carbon nanotubes in aqueous solution using weak polyelectrolyltes, such as poly(acrylic acid), poly(methacrylic acid), and polyethylenimine. As the pH of an aqueous mixture containing 1 wt% polymer and 0.1 wt% nanotube is altered, significant changes in suspension viscosity are observed due to changes in the dispersion state of the nanotubes. Cryo-electron microscopy was used to directly observe these microstructural changes that vary from highly exfoliated to heavily agglomerated. Drying these aqueous suspensions into composite films reveals pH-dependent microstructural differences that influence electrical conductivity. In poly(acrylic acid), nanotube exfoliation improves with increasing pH and these microstructurally-induced changes are reversible. This behavior has significant implications for the processing of carbon nanotubes and tailoring of composite properties. Many of the relationships described here could be applied to inorganic nanotubes and nanowires.
9:00 PM - II20.15
Clay Assisted Dispersion of Carbon Nanotubes in Epoxy.
Lei Liu 3 , Jaime Grunlan 1 3 2
3 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, 2 Chemical Engineering, Texas A&M University, College Station, Texas, United States
Show AbstractClay was introduced into single-walled carbon nanotube (SWNT)/epoxy composites to improve nanotube dispersion without harming electrical conductivity or mechanical performance. Unlike surfactant or polymer dispersants, clay is mechanically strong and known to exhibit good load transfer characteristics in polymer composites. Combining nanotubes and clay allows both electrical and mechanical behavior to be simultaneously enhanced. With just 0.05 wt% SWNT, electrical conductivity is increased by more than four orders of magnitude with the addition of 0.2 wt% clay. This improvement in conductivity is accompanied by an increase in storage modulus. Furthermore, the percolation threshold of these nanocomposites is reduced from 0.5 wt% SWNT to 0.1 wt% with the addition of clay. In effect, the dispersed clay acts as a template for the carbon nanotubes that causes them to become more exfoliated and better networked.
9:00 PM - II20.16
Preparation of Covalently Modified Single-Walled Carbon Nanotubes with Controlled Functionalization Ratio and Their Structural and Photophysical Properties.
Tomokazu Umeyama 1 , Noriyasu Tezuka 1 , Yoshihiro Matano 1 , Hiroshi Imahori 1
1 Graduate School of Engineering, Kyoto Univeristy, Kyoto Japan
Show AbstractDuring the last decades, noncovalent interactions between single-walled carbon nanotubes (SWNTs) and surfactants or polymers have been widely employed to prepare individually dispersed SWNTs in aqueous solvents. Although the structures and electronic properties of SWNTs are preserved after the solubilization, large excess of surfactants or polymers is required to achieve the solubilization as a result of the weak intermolecular interaction between the adsorbed molecules and SWNTs. Covalent attachment of functional groups to SWNTs can lead to the improvement of both solubility and stability of the functionalized SWNTs. It must be noted, however, that the covalent functionalization significantly alters the structural and electronic properties of pristine SWNTs. Therefore, it is of utmost importance to exploit covalent modification that allows us to achieve the sufficient solubility and retention of the intrinsic electronic properties of SWNTs after the significant, controlled degree of functionalization. In this study, we demonstrate that nucleophilic addition of enolate ion (Bingel reaction) to SWNTs under microwave irradiation can satisfy these demands.Sidewalls of acid-treated, shortened SWNTs linked with long alkyl chains at the tips and defect sites have been functionalized by Bingel reaction to examine the structures and spectroscopic properties in detail. As expected, the solubility of SWNTs in organic solvents is remarkably improved after the Bingel reaction. In addition, microwave-assisted Bingel reaction has been successfully applied to the sidewall functionalization of which the reaction rate is ca. 50 times faster than that under the conventional conditions. The degree of the sidewall functionalization (one adduct per 75 - 300 carbon atoms of SWNTs) was found to be controllable by changing the output power of microwave under the same temperature. Atomic force microscopy and transmission electron microscopy showed the progressive exfoliation of the SWNT bundles by the chemical modification. Furthermore, Resonant Raman and UV-vis-NIR absorption spectroscopies revealed that the electronic properties of SWNT are largely retained after the significant degree of the sidewall modification by Bingel reaction without apparent selective reactivity for metallic and semiconducting SWNTs. This is in remarkable contrast with conventional sidewall functionalization of SWNTs leading to the loss of their electronic properties. Thus, our covalent functionalization methodology can provide SWNT materials with both excellent solubility and inherent electronic properties which are highly desirable in solution-phase processing for the fabrication of SWNT-based molecular devices.[1] Umeyama, T.; Tezuka, N.; Fujita, M.; Matano, Y.; Takeda, N.; Murakoshi, K.; Yoshida, K.; Isoda, S.; Imahori, H. J. Phys. Chem. C, in press; [2] Umeyama, T.; Fujita, M.; Tezuka, N.; Kadota, N.; Matano, Y.; Yoshida, K.; Isoda, S.; Imahori, H. J. Phys. Chem. C, in press.
9:00 PM - II20.17
Preparation and Photophysical Properties of Nanocomposites of Single-Walled Carbon Nanotubes and Novel Conjugated Polymers.
Tomokazu Umeyama 1 , Naoki Kadota 1 , Noriyasu Tezuka 1 , Yoshihiro Matano 1 , Hiroshi Imahori 1
1 Graduate School of Engineering, Kyoto Univeristy, Kyoto Japan
Show AbstractCovalent and noncovalent functionalizations of single-walled carbon nanotubes (SWNTs) have led to considerable attention to exfoliate bundle structure of SWNTs [1,2]. Utilization of π−π interaction with conjugated polymers is one of the most promising methodologies for the debundling and solubilization of SWNTs. Thus, many studies have focused on the fabrication of nanocomposites of highly exfoliated SWNTs and π-conjugated polymers. However, the photophysical properties including energy transfer (EN) or electron transfer (ET) process between conjugated polymers and SWNTs have not been fully elucidated. Here we show the first unambiguous demonstration of EN from conjugated polymers to SWNTs in the composites by the near infrared (NIR) emission from the SWNTs. A novel conjugated polymer, poly[(p-phenylene-1,2-vinylene)-co-(p-phenylene-1,1-vinylidene)] (coPPV), has been prepared to examine specific interactions with SWNTs. The coPPV has the structural defect in the main chain of all-trans phenylene-1,2-vinylenes caused by 1,1-vinylidene moieties. It is expected that backbone structure of the copolymer can be fitted to the curvature of SWNTs more efficiently than the corresponding regular homopolymer, PPV, yielding individual SWNTs wrapped with the coPPV. The coPPV-SWNT nanocomposites were prepared by tip-sonication of a mixture of SWNTs and coPPV (1/10, w/w) in THF, centrifugation of the mixture, and filtration of the supernatant. The resultant solid on the filter, coPPV-SWNTs, was washed thoroughly and redispersed in THF with the aid of bath sonication. As expected, the dark brown solution without discernable particulates remained clear at least for 2 weeks, which is much more stable than that of all-trans PPV-SWNTs composite solution. UV-vis-NIR absorption spectrum of coPPV-SWNT in THF shows characteristic sharp peaks of SWNTs, demonstrating the high dispersing ability of coPPV. When fluorescence spectra of coPPV and coPPV-SWNTs in visible region are compared, the fluorescence intensity in coPPV-SWNTs relative to that in coPPV is reduced significantly, suggesting the occurrence of interaction between the excited state of coPPV and SWNTs. Furthermore, the NIR fluorescence contour plot of coPPV-SWNTs exhibits emission in the excitation wavelength range of 400–500 nm, where SWNTs show no absorption. This emission can be accounted by initial excitation arising from the π−π transition of coPPV, followed by EN from the excited coPPV to the SWNTs in the composites. Although there have been many reports on the NIR fluorescence of exfoliated SWNTs, this is the first example of enhancement of emission intensity by interaction with dispersing agents.[1] Umeyama, T.; Fujita, M.; Tezuka, N.; Kadota, N.; Matano, Y.; Yoshida, K.; Isoda, S.; Imahori, H. J. Phys. Chem. C, in press; [2] Umeyama, T.; Tezuka, N.; Fujita, M.; Matano, Y.; Takeda, N.; Murakoshi, K.; Yoshida, K.; Isoda, S.; Imahori, H. J. Phys. Chem. C, in press.
9:00 PM - II20.18
Percolation Phenomena in Organic Thin Film Transistors based on Langmuir-Blodgett Composite Film of poly(3-hexylthiophene) and Single-walled Carbon Nanotubes.
Jaehyun Park 1 , Gunchul Shin 1 , Gyu Tae Kim 2 , Jeong Sook Ha 1
1 Chemical and Biological Engineering, Korea University, Seoul Korea (the Republic of), 2 School of Electrical Engineering, Korea University, Seoul Korea (the Republic of)
Show AbstractThe percolation phenomena were investigated in organic thin film transistors (OTFTs) based on the composite films of regioregular poly(3-hexylthiophene) (P3HT) with single-walled carbon nanotubes (SWCNTs). The Langmuir-Blodgett technique enabled the reproducible fabrication of the percolative OTFTs made of P3HT and SWCNTs with a fine control of the relative composition. Depending on the relative ratio of SWCNTs, the critical behaviour near the onset of the percolation became significant. Below the percolation threshold, the source-drain current, Ids, did not change noticeably with the increase of the SWCNTs in the network. Within the transition range of the percolation, the on-off ratio increased sharply indicating the critical formation of the percolative conducting paths. At the high loading of SWCNTs, the saturation of the drain-source current and the small on-off ratio was confirmed, indicating the dominant metallic natures by SWCNTs. The percolative FETs can be a good way for enhancing the on-off ratio because of the effective contraction of the channel lengths and the critical behavior of the percolation threshold.
9:00 PM - II20.19
Preparation and Properties of Rubber Filled with Radial Single-walled Carbon Nanotubes.
Yoshinori Sato 1 , Kenji Hasegawa 2 , Nobuyuki Ito 3 , Kenichi Motomiya 1 , Balachandran Jeyadevan 1 , Kazuyuki Tohji 1
1 Graduate School of Environmental Studies, Tohoku University, Sendai Japan, 2 Polymer Research Laboratories, JSR Corporation, Mie Japan, 3 Material Characterization and Analysis Laboratory, JSR Corporation, Mie Japan
Show AbstractThe nanotube-filler used in the rubber applications is required to be easy to disperse in polymer [1,2]. The radial single-walled carbon nanotubes (radial SWCNTs) [3] with 1.5-2.0 nm in diameter and 50-100 nm in length are grown radially around the core metal particles, which are more easily dispersed in polymer than the semi-finite long SWCNTs. Here, we report the preparation of radial SWCNTs reinforced styrene–butadiene rubber (SBR) and investigate their properties.Ten weight percent of radial SWCNTs was blended with SBR to examine their effect on mechanical properties of the resulting composite, through the comparison with carbon black N339 (ASTM) as references. Radial SWCNTs resulted in an extraordinary hardness and low coefficient of repulsion, compared with N339. From microscopic surface analysis, the low dispersion of radial SWCNTs in the rubber matrix brought about lower fracture elongation and fracture strength as well as high hardness and low coefficient of repulsion.[1] L. Valentini, J. Biagiotti, J. M. Kenny and M. A. López Manchado, J. Appl. Polym. Sci., 89, 2657 (2003).[2] M. A. López Manchado, J. Biagiotti, L. Valentini and J. M. Kenny, J. Appl. Polym. Sci., 92, 3394 (2004).[3] Y. Sato, B. Jeyadevan, R. Hatakeyama, A. Kasuya, K. Tohji, Phys. Chem. Lett., 385, 323 (2004).
9:00 PM - II20.2
Conjugation of DNA-wrapped Single-walled Carbon Nanotubes and Quantum Dots.
Zhenping Zhou 1 , Tinh Nguyen 1 , Jeeseong Hwang 2 , Jeffrey Fagan 3 , Barry Bauer 3
1 Materials Research and Construction Division, National Institute of Standards and Technology, Gaithersburg, Maryland, United States, 2 Optical Technology Division , National Institute of Standards and Technology, Gaithersburg, Maryland, United States, 3 Polymers Division, National Institute of Standards and Technology, Gaithersburg, Maryland, United States
Show AbstractAnother novel nanotube-nanocrystal conjugation has been fabricated by the covalent linkage between DNA-wrapped single-walled carbon nanotubes (DNA-SWNTs) and quantum dots (QDs), featuring the water-soluble property. The structural and optical properties of this DNA-SWNTs/QDs conjugation have been characterized by various microscopy and spectroscopy. Compared to its counterpart formed by the acid-treated SWNTs and QDs, this DNA-SWNTs/QDs conjugation shows little peak shift in the optical absorption and Raman spectra, implying the DNA actually form a valid barrier for the possible electron transfer between QDs and carbon nanotubes.
9:00 PM - II20.20
Anisotropic Polymeric Matrix Composites with Oriented Carbon Nanotubes Containing Fe Nanoparticles: Preparation and Magnetic Properties.
Alessandro Chiolerio 1 , Paolo Allia 1 , Paola Martino 1 , Stefano Bianco 1 , Mauro Giorcelli 1 , Simone Musso 1 , Alberto Tagliaferro 1 , Marco Sangermano 2 , Giulio Malucelli 2 , Aldo Priola 2 , Marco Coïsson 3
1 Physics, Politechnic of Turin, Turin Italy, 2 Materials Science and Chemical Engineering, Politecnico di Torino, Turin Italy, 3 , Istituto Nazionale di Ricerca Metrologica, Turin Italy
Show AbstractPolymeric composite materials in the form of thick films was prepared, containing a dispersion of multi wall carbon nanotubes (MWCNTs), oriented by means of a static magnetic field. The MWCNTs (average diameter 50 nm; length 1 mm) were synthesized via tip-growth mechanism on uncoated Si (100), by a catalytic chemical vapor deposition (CVD), removed from the substrate, annealed at 400 °C in nitrogen flow in order to remove organic volatile species and ultrasonically dispersed directly into the monomer. Typical liquid epoxy and acrylate resins were used. They can undergo photopolymerization processes under UV radiation, in the presence of suitable photoinitiators. The concentration of MWCNTs was in the range 0.25 – 2 wt.%. In these conditions the rate of photopolymerization, as determined by real-time FT-IR spectroscopy, resulted a bit lower with respect to the pure monomers. Each MWCNT contains a ferromagnetic Fe nanoparticle, mainly localized in the tip of the tube. The Fe nanoparticle results from the catalyst decomposition and behaves as a magnetic dipole. This makes possible to exert a drag force on the dispersed MWCNTs by means of a magnetic field gradient, generated in our case by an array of permanent magnets whose magnetization direction was perpendicular with respect to the specimen plane. Orientation and viscous flow are possible before photopolymerization occurs. After the quick photocuring, the MWCNTs are “freezed” in their oriented state. Thus a composite having a geometrical anisotropy is obtained; this anisotropy may be reflected in its electronic, thermal, optical and mechanical properties, owing to the peculiarities of MWCNTs.Particular attention was devoted to the investigation of the magnetic properties of the cured materials by using an alternating gradient force magnetometer. Magnetization measurements were performed at room temperature on specimens produced both with zero and with external magnetic field, varying the rest time needed for the orientation to take place. During measurements, the magnetic field (H range: ± 18 kOe) was applied both in plane and out of plane. An anisotropic magnetic response has been observed, though consistent with some ordering effect provided by the external magnetic field. In any case, the magnetization in the plane of the film was found to be isotropic as expected.
9:00 PM - II20.21
Efficient One-step Surface Functionalization of Carbon Nanotubes with Polymer from Aqueous Solution.
Vincent Mévellec 1 , Sebastien Roussel 1 , Jerome Chancolon 3 , Martine Mayne-L'Hermite 3 , Pascale Chenevier 2 , Arianna Filoramo 2 , Guy Deniau 1 , Serge Palacin 1
1 Chemistry of Surfaces and Interfaces, CEA, Gif sur Yvette France, 3 Nanometric Structures, CEA, Gif sur Yvette France, 2 Molecular Electronics Laboratory, CEA, Gif sur Yvette France
Show AbstractDiazonium salts coupled with vinylic monomers were able to functionalize carbon nanotubes by simple iron redox activation in aqueous media. Hence, nano-sized carbon surfaces were shown to react with active radical species in solution through a covalent grafting process called Diazonium-Induced Anchoring Method, where diazonium salts are used both to initiate the polymerization of vinylic monomers in solution and to form a primer grafted polyphenylene like layer on the carbon surface. XPS, TEM and SEM analysis revealed that homogeneous polymer ultrathin films are grafted on carbon nanotubes and carbon fibers sidewalls. Raman spectroscopy further confirmed the covalent functionalization of single-wall carbon nanotubes.
9:00 PM - II20.22
Dispersion and Functionalization of Carbon Nanotubes by Conjugated Block Copolymer.
Qun Huo 1 , Jianhua Zou 1 , Lei Zhai 1 , Saiful Khondaker 1 , Liwei Liu 1
1 Nanoscience Technology Center, University of Central Florida, Orlando, Florida, United States
Show AbstractA general and facile approach of dispersing and functionalizing carbon nanotubes (CNTs) in one step was achieved using conjugated block copolymer without chemical modification of pristine CNTs. The block copolymer contains two structural segments, a conjugated poly(3-hexylthiophene) (P3HT) segment and a polystyrene (PS) segment. P3HT block forms pi-pi interactions with CNTs, therefore, breaks the strong van der Waals interactions between nanotube bundles, while the PS block provides a good solubility to the de-bundled CNTs and also a good compatibility with host polymer, PS matrix. An electrical conductivity percolation threshold of 0.03 wt% of carbon nanotube content was observed from a nanocomposite prepared from the dispersed CNTs and PS. Following the same concept and using different conjugated block copolymer, CNTs that are dispersable in organic or aqueous solution and sensitive to pH, light and thermal stimuli can be prepared.
9:00 PM - II20.24
Chromatic Carbon Nanotube Fibers.
Huisheng Peng 1 , Yuntian Zhu 1
1 Division of Materials Physics and Applications, Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show AbstractCarbon nanotube (CNT)-based sensors have received a great deal of attention, and their high sensitivity is mainly based on a drastic change of the electrical conductivity in response to an external stimulus. However, the use of the pristine non-assembled carbon nanotubes reported in these studies often involves tedious processes for integrating single carbon nanotubes into sensor devices, and the detection of reported CNT-based sensors relies on external instruments that record the difference before and after stimulus. Here we develop a new class of multifunctional CNT fibers sensors which respond to a wide arrange of stimuli with low cost, high sensitivity, good selectivity, and excellent stability. Particularly, the CNT fiber changes color from blue to red in response to stimuli, and this color switch can be directly observed by the naked eye.[1-3]1. Peng, H.; Tang, J.; Pang, J.; Chen, D.; Yang, L.; Ashbaugh, H. S.; Brinker, C. J.; Yang, Z.; Lu, Y. J. Am. Chem. Soc. 2005, 127, 12782-12783.2. Peng, H.;Tang, J.; Yang, L.; Pang, J.; Ashbaugh, H. S.; Brinker, C. J.; Yang, Z.; Lu, Y. J. Am. Chem. Soc. 2006, 128, 5304-5305.3. Peng, H. J. Phys. Chem. B 2007, in press.
9:00 PM - II20.25
Electrospinning of Polyamide 11 and MWCNTs-coated Nanofibers.
Kristopher Behler 1 , Mickael Havel 1 , Yury Gogotsi 1
1 Materials Science, Drexel University, Philadelphia, Pennsylvania, United States
Show AbstractPolyamide-11 (PA-11) and polyamide-12 (PA-12) are high-performance polymers. PA-11 is produced from a green raw material: castor beans, making it very interesting with the rising cost of oil and other sources of polymers. They show remarkable stability in high temperature, high pressure environments and outstanding chemical resistance (e.g. strong acids, bases and most organic solvents). Thus, they are used as gas and petroleum pipelines and can be exposed to salt water.While some polyamides have been successfully electrospun into fibers, PA-11 and PA-12 have remained a challenge. Using a mixture of formic acid and dichloromethane, PA-11 and PA-12 could be dissolved and subsequently electrospun into nanofibers of 100 nm and greater in diameter. Depending on the polymer concentration, ribbons and other structures were obtained in addition to the regular cylindrical fibers. The use of this new inexpensive solvent combination allows large volume manufacturing of polyamide nanofibers. Multiwalled Carbon Nanotubes (MWCNTs), which possess high electrical conductivity, were self-assembled onto the PA-11 electrospun mats. The resulting composite showed a dense MWCNTs coverage even at low weight percents, yielding high electrical conductivity, up to 100 S/cm.
9:00 PM - II20.26
Self-Assembling Tubules from Guanine/Cytosine Modules.
Ross Johnson 1 2 , Jesus Moralez 3 , Hicham Fenniri 1 2
1 , National Institute for Nanotechnology, Edmonton, Alberta, Canada, 2 Chemistry, University of Alberta, Edmonton, Alberta, Canada, 3 , Dupont Central Research and Development, Wilmington, Delaware, United States
Show Abstract9:00 PM - II20.27
Non-Covalently Modified SWNT Films as Electrodes for Conjugated Polymer Supercapacitors.
Merve Ertas 1 , Ryan Walczak 1 , Rajib Das 2 , Andrew Rinzler 2 , John Reynolds 1
1 Department of Chemistry, University of Florida, Gainesville, Florida, United States, 2 Department of Physics, Universiy of Florida, Gainesville, Florida, United States
Show AbstractElectrically conjugated polymers (CPs) and single walled carbon nanotubes (SWNTs) are demonstrated as electrode materials in supercapacitors, taking advantage of the high capacitances of CPs and the high surface area, mesoporous network of SWNTs. Poly(3,4-propylenedioxypyrrole) (PProDOP) was used as the main pseudocapacitance charge storage material and SWNT films were used as the current collector substrates. SWNT films provide mesoporous matrices, within which the polymer is mechanically interlocked. The specific capacitance and stability of the resulting supercapacitor are both substantially enhanced. These advantages were only realized once pyrene modified polyfluorene was used to enhance the interface between PProDOP and the SWNT films, thus improving polymer adhesion to the low energy nanotube surface. PProDOP films were prepared by in-situ electropolymerization onto SWNTs. Symmetrical solid state electrochemical capacitors were fabricated using polymeric gel electrolytes. For comparison, devices were also fabricated with gold electrode substrates. Capacitor performance was characterized using linear sweep voltammetry and galvanostatic charging-discharging. Capacitance values of the devices were observed to be in the range of 5-7 mF/cm2. With a 440 mC/cm2 charge density of polymer electrodeposited onto SWNT film (pre-coated with the pyrene modified polyfluorene) the device was measured to have 129 F/g capacitance. The supercapacitors consisting of the polymer on nanotube electrodes exhibited ca. 40% higher capacitance values than those on gold substrates. Additionally, a decrease in the total discharge time of the devices with the SWNT substrates was observed. The improved interface of the polymer to the nanotube substrate perhaps affects a decrease in interfacial resistance, giving rise to faster charging and discharging of the supercapacitors. Alternatively, the greatly enhanced polymer/substrate contact surface area alleviates a bottleneck to charge flow.
9:00 PM - II20.28
Spectroscopic Studies of Axial Strain in Individual Polymer Embedded Single-Walled Carbon Nanotubes.
Tonya Leeuw 1 , Dmitri Tsyboulski 1 , Pavel Nikolaev 2 , Sergei Bachilo 1 , Sivaram Arepalli 2 , R. Weisman 1
1 Chemistry, Rice University, Houston, Texas, United States, 2 , ERC Inc and NASA Johnson Space Center, Houston, Texas, United States
Show Abstract9:00 PM - II20.3
Synthesis and Evaluation of Ligand-Functionalized SWNTs as Transporter Agents for Tumor-Targeted Drug Delivery.
Jingyi Chen 1 , Shuyi Chen 1 , Xianrui Zhao 1 , Jonathan Patete 1 , Iwao Ojima 1 , Stanislaus Wong 1 2
1 , SUNY Stony Brook, Stony Brook, New York, United States, 2 , Brookhaven National Laboratory, Upton, New York, United States
Show AbstractWe designed and synthesized biotin-functionalized single-walled carbon nanotube (SWNT) conjugates as carriers for anti-cancer drug delivery. This conjugate includes a novel self-immolative disulfide-containing linker that enables the triggering of drug release and has been labeled with fluorescent probes. We characterized the conjugate by means of TEM, AFM, ATR-IR, and UV-visible spectroscopy. We have successfully demonstrated that this drug delivery system can selectively target and release the anti-cancer drug, e.g. a 2nd generation taxoid, to the tumor cells, which contain over-expressed biotin receptors on their surfaces, by means of in vitro confocal microscopy. The cellular uptake and drug release mechanism will be discussed. This particular drug delivery system integrates the nanoneedle effect of SWNTs with biotin-mediated-endocytosis to enhance the internalization of the prodrug into the tumor cells. We believe that the combination of biotin-functionalized SWNTs and the use of disulfide linkers for drug delivery system provides for several advantages over a conventional ligand-linker-drug delivery system, such as enhancement of drug payloads, solubility, and specificity.
9:00 PM - II20.30
Rendering Polymers and Polymer Blends Self-extinguishing through Carbon Nanotube/clay Synergy.
Seongchan Park 1 , Jaseung Koo 1 , Mayu Si 3 , Takashi Kashiwagi 2 , Jonathan Sokolov 1 , Miriam Rafailovich 1
1 Materials Science and Engineering, Stony Brook University, Stony Brook, New York, United States, 3 , Good Year, Akron, Ohio, United States, 2 Fire Research Division, NIST, Gaithersburg, Maryland, United States
Show AbstractWe have studied that polymers and polymer blends can be a new class of non-flammable nanocomosites in terms of self-extinguishing. PS and PMMA were chosen in this study because they are a typical immiscible and high flammable polymer blend. Additions of the standard flame retardant formulation of Decabromodiphenyl ether (DB) and Antimony Trioxide (AO) can give the system more effective to flame retardancy. We found that this traditional formulation had little effect in rendering this highly volatile polymer and polymer blend flame retardant. Although addition of 3 wt% of the Cloisite 20A decreased the heat release rate, it still did not make the systems self extinguishing. Addition of only 2 wt% of the MWCNTs, though, did produce a self extinguishing composite. We then investigated the microstructure of the composites in order to understand the nature of the synergy between the MWCNTs and the clay. Using EDAX analysis we found that the clays worked by improving the dispersion of the decabromodiphenyl ether component in PS/PMMA blend. Furthermore, the MWCNT prevented segregation and increased the viscosity of the polymers in the molten state. A series of TEM cross section that had been exposed to the flame showed that the MWCNTs did make themselves stick together with DB. The clays were partially exfoliated and were position at the PS/PMMA interface. In addition the FR agents were also presented near the clays. Upon thermal annealing, the clays prevented the phase separation of the PS and PMMA, The short MWCNTs, which are localized in the blend, were found to phase separation together with the PMMA phase, while the long MWCNT remained fixed at the PS phase. These results are a good agreement with their residues. More cracks were observed on surface of the short MWCNTs’ residue because of more electrostatic property of the short one. It can be believed that the short MWCNTs is stronger than the long MWCNTs in thermal conductivity of nanotubes. Therefore, degree of thermal conductivity may be a critical factor to explain self-extinguishing in nanotube-based polymers and polymer blends.
9:00 PM - II20.31
Tubulin binds, Interconnects and Encapsulates Carbon Nanotubes.
Cerasela Dinu 1
1 Center for Biotechnology and Interdisciplinary Studies, Department of Chemical and Biological Engineering, Rensselaer Nanotechnology Center, Rensselaer Polytechnic Institute, Troy, New York, United States
Show Abstract9:00 PM - II20.32
Solidification of Lanthanum Carbide-encapsulating Carbon Nanocapsules.
Ippei Waki 1 , Yoshinori Sato 1 , Masaru Namura 1 3 , Kenichi Motomiya 1 , Jeyadevan Balachandran 1 , Akira Okubo 2 , Hisamichi Kimura 2 , Kazuyuki Tohji 1
1 Graduate School of Environmental Studies, Tohoku University, Sendai Japan, 3 Manufacturing Technologies Department, Dowa Holdings Co., Ltd., Tokyo Japan, 2 Insutitute of Materials Research, Tohoku University, Sendai Japan
Show AbstractMammography screening is one of the attractive techniques to find out the breast cancer. It is a radiography method that compresses breasts with two boards in order to find out the cancer or calcification, indicating the existence of early breast cancer. Although the iodinated contrast material has been used, the blood capillaries around cancer have not been caught well with the present screening techniques. During the radiography, clearer contrasting images can be obtained by characteristic X-rays with an X-ray absorption edge that is shorter than that of the target materials. Lanthanum (La) containing materials are suitable for X-ray target materials as the characteristic X-rays of La (33.3 keV) are just shorter than the X-ray absorption edge of iodine (33.2 keV). An X-ray target material requires high melting point, heat conductivity, and electric conductivity. For example, Lanthanum possesses low melting point (1,191K), low heat conductivity (13.4 W/mK), and Lanthanum oxide (La2O3) possesses low electric conductivity. So these two materials are not suitable for X-ray target materials. In contrast, lanthanum carbide-encapsulating carbon nanocapsules (LaC2@CNCs), consisting of several graphene sheet capsules, are suitable for X-ray target material because they are expected to have high melting point (2523 K: LaC2), heat conductivity (129 W/mK: graphite), and electric conductivity (3×104 S/cm: graphite). Here, we report solidification process and evaluation of LaC2@CNC composites.LaC2@CNCs were synthesized by a direct current arc-discharge method between pure graphite rod and metal-loaded graphite rod. The anode rod was drilled and filled with composite of lanthanum oxide (La2O3) powder and graphite to make rod to contain 1.0 atom percent of La. Arc discharge was run with helium pressure of 100 Torr and arc-discharge current of 70 A. After arc discharging, the cathode deposit, containing LaC2@CNCs, was collected and ground using an agate mortar. Next, the ground sample was treated with 1M HCl acid in 333 K for 12 hours to remove La2O3. The resulting sample was ground using satellite mill in dry condition for 30 minutes with lanthanum boride (LaB6) powder, used as a binder. Each composite contained 20, 30, 40, and 50 weight percent of the cathode deposit. Spark plasma sintering (SPS) condition was carried out by varying the sintering pressure from 80 to 120 MPa and the sintering temperature from 1123 to 1323 K in order to make a sintered solid of 10 mm in diameter. The surface morphology and physical properties of the resulting sintered solid were characterized. The each result of the sintering solid will be reported in detail and discussed.
9:00 PM - II20.33
Functionalization of Carbon Nanotubes by Doping of Metal Atoms to the Side Walls.
Guangping Zheng 1
1 Mechanical Engineering, University of Hong Kong, Hong Kong China
Show Abstract9:00 PM - II20.35
Preparation of Polymer-grafted Multiwalled Carbon Nanotubes by γ-irradiation.
Chan-Hee Jung 1 , Dong-Ki Kim 1 , Junhwa Shin 1 , Youn-Mook Lim 1 , Jeun Joon-Pyo 1 , Phil-Hyun Kang 1 , Young-Chang Nho 1 , Jae-Hak Choi 1
1 , Korea Atomic Energy Research Institue , Jeongeup-si, Jeollabuk-do Korea (the Republic of)
Show AbstractBecause of their unique structure and remarkable electrical, mechanical and chemical properties, carbon nanotubes (CNTs) can be considered as attractive candidates for diverse nanotechnological applications such as displays, microcircuits, sensors, biomaterials, energy storage, gas storage, and many others. However, their lack of dispersibility and their difficult manipulation in any solvent have imposed great limitations on the use of CNT. Major efforts have been devoted towards any modification of the CNTs that could improve their processability. Typically, a chemical modification of CNTs is based on severe oxidation processes that often damage the nanotubes. Mild and single-step modification of CNTs is a valuable alternative to an oxidative treatment. There are many reports on a modification of CNTs such as (a) a covalent attachment of chemical groups, (b) a non-covalent adsorption or wrapping of various functional molecules, and (c) an endohedral filling of their inner empty cavity. Among them, a covalent reaction of CNTs with polymers is widely used because the long polymer chains help to dissolve the nanotubes into a wide range of solvents even at a low degree of functionalization. In this study, multi-walled carbon nanotubes (MWCNTs) were functionalized by radiation-induced grafting of various monomers such as styrene, acrylic acid, etc. onto the nanotubes. The dispersibility of the polymer-grafted MWCNTs was enhanced. The polymer-grafted MWCNTs were also characterized by 1H NMR, Raman spectroscopy, TEM, TGA techniques.
9:00 PM - II20.36
Influence of Nanotubes and Other Nanofillers on the Properties of Thermoset:thermoplastic Blends for Composite Matrices.
Marianne Kilbride 1 , Richard Pethrick 1
1 Pure and Applied chemistry, Strathclyde University, Glasgow United Kingdom
Show Abstract9:00 PM - II20.38
Dynamics of Surfactant-Suspended Single Walled Carbon Nanotubes in a Centrifugal Field.
Nitish Nair 1 , Woo-Jae Kim 1 , Richard Braatz 2 , Michael Strano 1
1 Chemical Engineering Department, MIT, Cambridge, Massachusetts, United States, 2 Chemical and Biomolecular Engineering, University of Illinois, Urbana-Champaign, Illinois, United States
Show Abstract9:00 PM - II20.39
Effects of the Pyrolysis Rate on the Electrical Properties of GPC: CNT Composite Material.
Bopha Chhay 1 , Daryush Ila 1
1 Center for Irradiation of Materials, Alabama A&M University, Normal, Alabama, United States
Show Abstract9:00 PM - II20.4
Thin Film SWNT-Biopolymer Nanocomposites: Production and Characterization of Protein and DNA Based Single-Walled Carbon Nanocomposite by Layer by Layer Assembly.
Virginia Davis 1 , Dhriti Nepal 1 , Shankar Balasubramania 2 , Aleksander Simonian 2
1 Dept. of Chemical Eng., Auburn University, Auburn, Alabama, United States, 2 Materials Engineering, Auburn University, Auburn, Alabama, United States
Show AbstractLayer-by-layer assembly (LBL) is a versatile technique for the controlled bottoms-up assembly of thin films. Properties of SWNT thin films are related to not only composition, but the degree of dispersion. Dispersions of highly debundled and individual SWNTs in DNA and lysozyme were achieved and used to produce thin films using the LBL process. The use of shear flows during film drying to create aligned layers of SWNTs was demonstrated. Dispersion quality was determined by UV-vis-NIR, atomic force microscopy, and rheology. The deposition process was monitored by UV-Vis-NIR absorbance spectroscopy which showed a linear increase in absorption with the number of bilayers confirming uniform surface coverage. Film deposition, quality and alignment were also assessed by a combination of surface plasmon resonance spectroscopy, Raman spectroscopy, cyclic voltametry, atomic force microscopy, and scanning electron microscopy. The role of substrate surface chemistry and the potential applications of these unique SWNT biocomposite materials will also discussed.
9:00 PM - II20.40
Carbon Nanohorn-Ferrocene Hybrids: Synthesis, Characterization and Photoelectron Properties for Applications in Energy Conversion Schemes.
Georgia Pagona 1 , Sofia Sotiropoulou 2 , Carl A. Batt 2 , Alan Maigne 3 , Masako Yudasaka 3 , Sumio Iijima 3 , Nikos Tagmatarchis 1
1 Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, Athens Greece, 2 Department of Food Scienc, Cornell University, Ithaca NY, New York, United States, 3 , Fundamental and Environmental Research Laboratories NEC Corporation and SORST-JST, Tsukuba, Ibaraki Japan
Show AbstractElectron transfer reactions are of particular interest for the study of fundamental biological reactions as well as for the development of efficient energy storage and conversion devices. Nanomaterials such as carbon nanotubes (CNTs) and fullerenes have been largely explored as building blocks in molecular electronics, with promising results. Recently, a new carbon allotrope within the family of CNTs, namely carbon nanohorns (CNHs), started to emerge. The CNHs are free of metal particles impurities, while possessing unique structural features such as the presence of five 5-membered rings at one terminal tip forming a highly strained cone and spherically aggregate during production forming dahlia-flowerlike structures. Their full realization in nanoscale electronics requires their solubilization and the controlled functionalization, where the interactions between the individual parts will be clearly understood.Ongoing efforts of our group concern the design, synthesis and systematic investigation of novel CNHs-based nanohybrids with electron-donor organic moieties. In this direction, we introduced ferrocene (Fc) organic moieties resulting in asymmetric donor-acceptor nanohybrid materials.The functionalization of CNHs was performed via the 1,3-dipolar cycloaddition of azomethin ylides, accomplishing the covalent connection of CNHs with ferrocene through a pyrolidine ring. The spectroscopic characterization of the nanohybrids revealed a broad adsorption in the UV-Vis region, without characteristic spectral bands. Morphological characterization using HR-TEM of the CNHs-Fc nanohybrids verified that functionalization was not detrimental to the CNH structure. Additionally, STEM and EELS mapping and analysis probed the uniform distribution of iron onto the skeleton of CNHs.The electron transfer reactions between the Fc donor moieties and the CNHs in the different hybrid material architectures, with respect to the location of the Fc moiety, were probed using photo-electrochemistry (cyclic voltammetry and linear sweep voltammetry). Under photoexcitation a photocurrent was generated and the proximity of the donor-acceptor moieties is found to control the electron acceptor or donor properties of the hybrids. This allows the fine tuning of the redox properties of the CNH based hybrids, a property that can find application in the design of molecular switches for electronic and bioelectronic devices.This work, conducted as part of the award (“Functionalization of Carbon Nanotubes Encapsulating Novel Carbon-based Nanostructured Materials”) made under the European Heads of Research Councils and European Science Foundation EURYI (European Young Investigator) Awards scheme, was supported by funds from the Participating Organizations of EURYI and the EC Sixth Framework Programme.
9:00 PM - II20.41
Carbon Nanotube Fibers with Excellent Mechanical and Electrical Properties.
Qingwen Li 1 , Lei Fu 1 , Lianxi Zheng 1 , Paul Arendt 1 , Dean Peterson 1 , Yuntian Zhu 1
1 MPA-STC, Los Alamos National Lab, Los Alamos, New Mexico, United States
Show AbstractThe unique structures of carbon nanotubes have endowed them with exceptional material properties, such as very high electrical and thermal conductivity, strength, stiffness, and toughness. They open an incredible range of applications in materials science, electronics, chemical processing, energy management, and many other fields. Processing carbon nanotubes into ordered assemblies, such as in the form of fibers or sheets makes it possible to explore their intrinsically high strength at a macroscopic level. In this aspect, carbon nanotubes fibers show great promise to compete with carbon fibers in strong and light-weight applications in the future (1-3). Carbon nanotube arrays are excellent precursors for spinning carbon nanotubes into fibers. However, the mechanical and electrical properties of spun fibers depend greatly on the growth of carbon nanotube arrays, packing density and tube-to-tube connections formed in the fiber. Here, we report our recent progress on how to process carbon nanotube fibers simultaneously with good strength and conductivity. The effects of some important processing parameters, such as the spinnability of an array, array length, clustering of carbon nanotubes, packing density of carbon nanotubes and some post-treatment approaches including post-twisting, re-organizing carbon nanotubes by capillary force and electrical field on the mechanical and electrical properties of carbon nanotube fibers have been investigated. With their excellent mechanical and electrical properties, the carbon nanotube fibers are promising for smart textile materials. References: 1) X.F. Zhang, Q.W. Li, Y. Zhu, et al., Ultra Strong, Stiff and Lightweight Carbon Nanotube Fiber, Adv. Mater, in press.2) Q.W. Li, Y. Li, Y. Zhu et al., Structure-dependent electrical properties of carbon nanotube fibers, Adv. Mater, in press.3) Q. W. Li, Y. Zhu et al., Sustained growth of long carbon nanotube arrays for fiber spinning, Adv. Mater., 2006, 18, 3160
9:00 PM - II20.43
A Molecular Approach to Orienting and Sorting Carbon Nanotubes for Electromechanical Devices.
Georgi Georgiev 1 2 , Christopher Rocheleau 1 , Mark Cronin 1 , Yaniel Cabrera 2 , Lei Yu 2 , Peggy Cebe 2 , Robert Doyle 1 , Aditya Ahlawat 1 , Brian Mulkern 1 , Jennifer Mongeau 3 , Alex Ogilvie 4
1 Department of Natural Sciences, Assumption College, Worcester, Massachusetts, United States, 2 Physics Department, TUFTS University, Meford, Massachusetts, United States, 3 , University of Massachusetts, Worcester, Massachusetts, United States, 4 , University of Maine, Orono, Maine, United States
Show Abstract9:00 PM - II20.45
Polyvinylpyrrolidone (PVP) Assisted Dispersion and Isolation of Single Walled Carbon Nanotubes in N-Methyl 2 Pyrrolidone (NMP).
Tawfique Hasan 1 , Vittorio Scardaci 1 , Francesco Bonaccorso 1 , PingHeng Tan 1 , Aleksey Rozhin 1 , Stephan Hofmann 1 , William Milne 1 , Andrea Ferrari 1
1 Department of Engineering, Cambridge University, Cambridge United Kingdom
Show AbstractWe report high quality dispersions of purified HiPco Single Walled Carbon Nanotubes (SWNTs) in N-Methyl 2 Pyrrolidone (NMP) without chemical functionalization. As the dispersing agent, we use Polyvinylpyrrolidone (PVP), a linear polymer. We achieve ca. 0.11 g/L SWNT concentration in the dispersion prepared by ultrasonic treatment followed by vacuum filtration. This is a one order of magnitude improvement with respect to previously reported dispersions of unfunctionalized SWNTs in NMP [1,2]. Photoluminescence excitation spectroscopy confirms the presence of isolated SWNTs as well as small bundles of SWNTs in these dispersions [1,3]. Mostly isolated SWNT suspensions with a concentration of ca. 0.002 g/L are obtained by a two-step ultra-centrifugation treatment of the abovementioned dispersions. Changes in relative photoluminescence intensity in the isolated SWNT dispersions indicate that the PVP aided dispersion mechanism is preferential to particular nanotube species.References:1.T. Hasan et al J. Phys. Chem. C in press, (2007)2.S. Giordani et al. J. Phys. Chem. B 110, 15708 (2006)3.P. H. Tan et al., cond.-mat. 0704.2303 (2007).
9:00 PM - II20.46
Fabrication of Ultrathin Multi-walled Carbon Nanotube Film using the Liquid/liquid Interface.
Jun Matsui 1 2 , Kohei Yamamoto 1 , Nobuhiro Inokuma 1 , Hironori Orikasa 1 , Takashi Kyotani 1 , Tokuji Miyashita 1
1 Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Miyagi, Japan, 2 PRESTO, JST, Kawaguchi, Saitama, Japan
Show Abstract Carbon nanotubes (CNTs) shows unique mechanical properties such as high tensile strength with flexibility as well as conductive or semiconductive properties, it can be applied in active materials in flexible electronics. For such applications, it is important to create a uniform ultrathin film of CNTs onto a flexible polymer substrate. Usually polymer materials cannot stand for high temperature condition used in CNT synthesis, solution based techniques which include, self-assembly, layer-by-layer assembly, and the Langmuir-Blodgett (LB) technique are suitable for fabricating a CNT ultrathin film. In this presentation, we will describe the fabrication of a densely packed ultrathin film of multi-walled carbon nanotube (MWCNT) using the liquid-liquid interface. The MWCNTs used in this study was synthesized using an anodic aluminium oxide (AAO) film as a template. Briefly, an aluminum plate was anodically oxidized for 26 min with a constant voltage of 10 V in sulfuric acid (20 wt %) to produce 5 μm-length straight nanochannels with a diameter of 10-20 nm in the aluminum oxide onto the plate. The anodically oxidized aluminum plate was used as a template for MWCNT synthesis. Chemical vapor deposition (CVD) of acetylene gas (600 degree Celsius) was carried out onto the oxidized plate to coat it with carbon. After CVD process, the template was dissolved by immersing it in 3 M NaOH aqueous solution and the librated MWCNTs were dispersed in ethanol. For fabricating the MWCNT ultrathin film using the liquid-liquid interface, the dispersion was diluted with water, and then hexane was added to the dispersion to create the liquid-liquid interface. When extra ethanol was added to the MWCNT water dispersion/hexane solution, MWCNTs were smoothly assembled at the interface to form an ultrathin film. The ultrathin film can be transferred onto a solid substrate using the Langmuir-Blodgett deposition technique. With addition of 10 vol% of ethanol to the solution, an ultrathin film of MWCNT with coverage of about 70 % was fabricated. Moreover, the multilayer film was fabricated by sequential deposition of the ultrathin film. The assembly mechanism and electric properties of the MWCNT ultrathin film will be also discussed.
9:00 PM - II20.48
Single Walled Carbon Nanotubes Functionalized with Polyaniline in Ionic Liquids.
Di Wei 1 , Carita Kvarnstrom 1 , Tom Lindfors 1 , Ari Ivaska 1
1 Lab of Analytical Chemistry, Abo Akademi University, Abo/Turku Finland
Show AbstractSingle walled carbon nanotubes (SWNTs) are covalently functionalized during the electro-polymerization of aniline in ionic liquids. In our experiment, 1-butyl-3-methyl-imidazolium hexafluorophosphate (BMIPF6) containing 1 M trifluoroacetic acid (CF3COOH) was selected as the ionic liquid media to individualize SWNTs and to perform the electropolymerization of aniline within. The morphology of the resulting composite material of SWNT and polyaniline (PANI) was studied by scanning electron microscopy (SEM). Covalent bonding was evi-denced by the increase of intensity ratio of the D band vs. G band in the Raman spectrum, whilst SWNTs may also be incorporated as big dopant anions to the PANI backbone. This pa-per provides a novel method by which large amount of SWNTs (15 mg/ml) can be modified by aniline electrochemically. p-type conducting polymer and n-type SWNTs can be thus co-polymerized and applied to organic photovoltaics.
9:00 PM - II20.49
Carbon Nanotubes – Polymer Composites as Nonlinear Optical Materials.
Vittorio Scardaci 1 , Tawfique Hasan 1 , Fengqiu Wang 1 , John Woods 1 , PingHeng Tan 1 , Aleksey Rozhin 1 , Ian White 1 , William Milne 1 , Andrea Ferrari 1
1 Department of Engineering, Cambridge University, Cambridge United Kingdom
Show AbstractSingle Wall Carbon Nanotubes (SWNTs) show strong saturable absorption in the near infrared region with ultra fast recovery time, i.e. they become transparent under high power irradiation [1,2]. They are thus suitable for application in nonlinear optical devices such as noise suppression filters and passively mode-locked lasers [3]. Here we report the processing and characterization of SWNT-based composites with polycarbonate and polyimide, which are highly transparent and stable to environmental conditions. Purified SWNTs are used to avoid non-saturable absorption from residual catalyst and carbon particles. SWNTs with different diameter distributions are dispersed in N-methylpyrrolidone (NMP) by strong ultrasonication aided by polyvinylpyrrolidone (PVP), followed by ultracentrifugation and/or microfiltration to remove residual impurities and large bundles. The polymer is then added to the solution and the mixture is finally dried. A freestanding film is obtained, with a uniform distribution of SWNTs on a sub-micrometer scale, as no aggregates can be resolved by optical microscopy. Vis-IR absorption spectrophotometry is used to study the linear optical properties. The saturable absorption is studied with a femtosecond laser source using a transmission loss method. We finally use our SWNTs-polymer to manufacture an ultra-fast fibre laser capable of sub-ps pulses [4].References:[1] Y.C. Chen et al., Appl. Phys. Lett. 81, 975 (2002)[2] A.G. Rozhin et al., Chem. Phys. Lett. 405, 288 (2005)[3] A.G. Rozhin et al., Phys. Stat. Sol. (b) 243, 3551 (2006)[4] V. Scardaci et al. Physica E 37, 115 (2007).
9:00 PM - II20.5
Hybrid Carbon Nanotubes for Gas Sensing.
Sean Brahim 1 , Steve Colbern 1 , Robert Gump 1 , Leonid Grigorian 1
1 Sensors/Carbon nanotubes, YTC America Inc., Camarillo, California, United States
Show AbstractWith the increasing demand for superior gas sensors of higher sensitivity and greater selectivity, intense efforts are being made to find more suitable materials with the required surface and bulk properties for use in practical gas sensors. In this work, we report on the fabrication and performance of novel metal-CNT hybrids as gas sensors. The adsorption of gaseous species on the hybrid material was characterized by changes in the CNT impedance. By varying the nature of the metal infiltrated into the CNT, we observe dramatically different responses among the hybrid sensors in response to the target analyte. The feasibility of this approach for gas sensing will be discussed with respect to (1) the metal-CNT hybrid materials, (2) the effect of environmental factors, and (3) the selectivity towards gaseous species being detected. These differential impedimetric responses created from a library of metal-CNT hybrid materials may function as a practical approach for offering enhanced sensitivity and selectivity for gas sensing.
9:00 PM - II20.50
Tin Oxide Nanoparticles Deposited Inside Multiwalled Carbon Nanotubes.
Takeshi Hashishin 1 , Takahiro Kishi 1 , Jun Tamaki 1
1 Applied Chemistry, Ritsumeikan University, Kusatsu Japan
Show AbstractThe nanocomposites between carbon nanotubes (CNTs) and metal oxides could be applied to functional materials fields such as gas detection, new catalyst, and so on. As first study of nanocomposite materials, we fabricated the conductivity-type sensor based on CNTs-tungsten trioxide composite for nitrogen dioxide detection and clarified to show the fairly good sensor response (= resistance in air / resistance in nitrogen dioxide) to dilute NO2, comparing that the sensor fabricated from only CNTs exhibited almost no response. Thus combinatorial nanomaterials would give us interesting phenomena.In this study, tin oxide nanoparticles with few nm in diameter were deposited outside as well as inside multiwalled carbon nanotubes (MWNTs) by simple precipitation.A solution mixture of 0.05wt% nickel acetate and ethanol was dropped by using micromanipulator, dried for 30 min to disperse homogeneously the solution mixture on silicon substrate. The Ni-deposited substrate was subsequently set on the electric furnace, and MWNTs were grown from nickel catalysts at 700 degree C for 1 hr under a gas mixture of argon and hydrogen by chemical vapor deposition. Acid treatment of MWNTs was performed by stirring for 30 min at 130 degree C in 30mL conc. nitric acid to remove nickel catalysts on the tip of MWNTs and amorphous carbon. Microstructural analysis of MWNTs indicated that the size of MWNTs was 20-50 nm in diameter and 10-100 micrometer in length and the nanotubes have also more than 1.5 of the G/D ratio by mean of TEM and Raman spectroscopy. There was also no damage to the microstructure of MWNTs by acid treatment. Tin oxide was deposited on MWNTs by sintering process of 400 degree C for 3 hr after immersed MWNTs in 1wt% tin tetrachloride aqueous solution. The solution containing MWNTs was vacuumed for 30 min to introduce tin oxide nanoparticles inside MWNTs. The tin oxide nanoparticles excessively deposited outside MWNTs were removed by ultrasonic treatment in which both frequency of 28 and 45 kHz were respectively irradiated to the exceed tin oxides outside MWNTs for 10 min. Bright-field TEM image indicated that tin oxides with ca. 3-5 nm particles in diameter were deposited inside/outside MWNTs with ca. 40 nm in diameter. This particle size can be expected to have high specific area providing many adsorption sites of gas molecules.
9:00 PM - II20.52
Controlling the Phase Behavior of Single-Walled Carbon Nanotube–Superacid Dispersions.
A. Nicholas Parra-Vasquez 1 3 4 , Virginia Davis 5 1 3 , Pradeep Rai 1 3 4 , Hua Fan 3 4 , Richard Booker 3 4 , Natnael Behabtu 1 3 4 , Valentin Prieto 1 3 , Robert Pinnick 1 3 , Jon Allison 3 4 , Carter Kittrell 2 3 4 , Wen-Fang Hwang 3 4 , Howard Schmidt 2 3 4 , Robert Hauge 2 3 4 , Richard Smalley 2 3 4 , Matteo Pasquali 1 2 3
1 Chemical and Biomolecular Engineering, Rice University, Houston, Texas, United States, 3 Carbon Nanotechnology Laboratory, Rice University, Houston, Texas, United States, 4 The Smalley Institute for Nanoscale Science & Technology, Rice University, Houston, Texas, United States, 5 Chemical Engineering, Auburn University, Aubrun, Alabama, United States, 2 Chemistry, Rice University, Houston, Texas, United States
Show AbstractSingle-wall carbon nanotubes (SWNT) have unique mechanical, thermal, and electrical properties; if retained on a macroscopic level, these could be exploited in industrial, biological, and scientific applications. However, due to their strong van der Waals attraction they are difficult to disperse. We report the first characterization of the effect of solvent quality on SWNT-liquid crystal morphology and phase behavior. Unlike in polymer liquid crystals, temperature has little effect on the phase transitions of SWNTs dispersed in superacids; however, we find that the protonating ability of the solvent controls the phase behavior. The isotropic-nematic phase boundary of SWNT-superacid dispersions shifts to higher SWNT concentrations at higher acidity. Solvent acidity also controls the morphology of liquid crystal. The microstructure of solid fibers spun from the liquid crystal dispersions can be altered by changing the solvent as well as the solvent removal process.
9:00 PM - II20.53
Novel Polyion Complex Based Carbon Nanotube Fibers.
Sandeep Razdan 1 , Pulickel Ajayan 1 , Swastik Kar 1 , Robert Vajtai 1 , Lijie Ci 1
1 Materials Science, Rensselaer Polytechnic Institute, Troy, New York, United States
Show AbstractFibers based on carbon nanotubes represent interesting architectures in terms of distribution of nanotubes in a quasi-one dimensional matrix and are useful for various applications such as supercapacitors, artificial muscles and wearable electronics. We have recently developed a technique to synthesize carbon nanotube fibers based on polyionic complexes. Polyions are special polymers that dissociate into charged species in water or other solvent medium. Upon combination of two such oppositely charged polyions (polycation and polyanion), a precipitate (polyionic complex) is formed which may be drawn like a fiber. We utilized this process to synthesize fibers of carbon nanotubes, drawn from the interface of a polycation/polyanion mixture. In the first step, carbon nanotubes were dispersed in a solution of 1 wt% polystyrene sulfonate (PSS) in water. Polystyrene sulfonate forms a stable dispersion with carbon nanotubes up to 1 wt% (10 mg/ml). This stable dispersion was then added to a solution of 20 wt% polydiallyldimethylammonium chloride (PDDA) where it formed a precipitate at the interface of the two polyelectrolytes. This precipitate is formed as a result of combination of PDDA as a host polycation and PSS as a guest polyanion, entrapping the dispersed carbon nanotubes in the process. The precipitate can then be picked up and drawn resulting in a black fiber containing carbon nanotubes. The drawn fibers were dried at 60°C for half an hour resulting in rigid brittle fibers of varying diameters from 10 – 200 microns. Scanning electron micrographs showed brittle fracture surfaces with well aligned nanotubes protruding along the fiber axis. Electrical measurement performed on fibers obtained using varying concentrations of carbon nanotubes in the original dispersions revealed a maximum conductivity of 2 – 3 S/cm for 1 wt% dispersion of nanotubes in PSS. However, since both polyelectrolytes involved in the fiber formation were water soluble, we observed that subsequent careful “washing” of the fibers with water before drying improved the conductivity of the fibers up to 30 – 50 S/cm. The scanning electron micrograph images of such “washed” fibers showed dense networks of nanotubes at the fracture interfaces, compared to the “unwashed” samples. The fibers also had a tensile strength of the order of 20 MPa owing to the brittle nature of the polyelectrolytes involved. We are currently investigating other polyelectrolytes such as chitosan, polyethyleneimine (PEI), polyacrylic acid (PAA) etc. to develop a universal technique for such fiber formation. We are also in the process of synthesizing multicomponent fibers with different additives such as gold nanoparticles, along with nanotubes. These fibers are promising for such applications as chemical sensors, electrodes, as well as flexible electronics.
9:00 PM - II20.54
Antenna Chemistry with Single Wall Carbon Nanotubes(SWNTs) -Field Induced Redox and Self-Assembly Process.
Juan Duque 1 , Matteo Pasquali 1 2 3 , Howard Schmidt 3
1 Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas, United States, 2 Department of Chemistry, Rice University, Houston, Texas, United States, 3 Carbon Nanotechnology Laboratory, The Smalley Institute for Nanoscale Science & Technology, Rice University, Houston, Texas, United States
Show AbstractOxidation-reduction chemistry of Single Wall Carbon Nanotubes (SWNT) is an emerging field which can potentially find applications in chirality and diameter separation of tubes. Here, we study the electron transfer from SWNT to reducible transition metal ions in solution under a broad band light irradiation (1367 – 222 nm) and electric field driven reactions. Atomic Force Microscopy (AFM) images showed substantial evidence that the tips of the tubes are focal point for the nucleation and growth of metal particles resulting in interesting and useful nanostructures.
9:00 PM - II20.55
Fiber Composites Reinforced by Aligned Carbon Nanotubes.
Brian Wardle 1 , Enrique Garcia 1 , Anastasios John Hart 1 , Namiko Yamamoto 1 , Alex Slocum 1
1 , MIT, Cambridge, Massachusetts, United States
Show AbstractWhile CNT-polymer composites are widely used as conductive plastics, mixing and dispersion-based techniques typically prevent incorporation of CNTs at concentrations beyond a few wt% and make it difficult to align CNTs within matrix materials. These hindrances have prevented CNT-based composites from achieving significant enhancements in mechanical properties, which are vital for structural applications. We present a platform for large-scale integration of aligned CNTs into existing advanced aligned and woven fiber composites, where locally high weight fractions of aligned CNTs significantly enhance mechanical and multifunctional characteristics, by reinforcing matrix-dominated interfaces between adjacent fibers and fiber layers (plies).Rapid wetting of long aligned carbon nanotube (CNT) forests [1] with off-the-shelf (no solvent added) commercial thermoset polymers is demonstrated experimentally and a technique for creating vertically aligned CNT composite microstructures of various shapes is presented [1]. Direct characterization of the mechanical properties of the nanocomposites structures reveals a 220% increase of the Young's modulus at 2% volume loading [3], supporting the feasibility of using these CNT forests in large-scale hybrid advanced composite architectures reinforced with aligned CNTs. A hybrid composite architecture consisting of aligned carbon nanotubes (CNTs), woven ceramic fiber cloth, and a thermoset epoxy, is described, fabricated, and tested [4]. Fabrication begins with growth of aligned CNTs on the surface of fibers in a ceramic fiber cloth using a thermal chemical vapor deposition process and a liquid-based catalyst, and nano-engineered laminates are constructed using conventional hand layup techniques. The strength of the interlaminar reinforcement is investigated experimentally, and initial results give 70% higher shear strength,160% higher interlaminar toughness, and 107 increase in electrical conductivity compared to an unreinforced laminate. Future research will focus on scalability and optimization of the CVD process, extension of the CVD growth to carbon fibers, and characterization of other properties such as mechanical properties, coefficient of thermal expansion (CTE), degradation, impact damage resistance and tolerance, and fatigue.References[1] A. J. Hart, A. H. Slocum, J. Phys. Chem. B 2006, 110, 8250 [2] E. J. García, A. J. Hart, B. L. Wardle, A. H. Slocum, Nanotechnology 2007, 18, 165602.[3] E. J. García, A. J. Hart, B. L. Wardle, A. H. Slocum, Adv. Mat. 2007, in press.[4] E. J. García, A. J. Hart, B. L. Wardle, A. H. Slocum, Proceedings of 48th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, Honolulu, HI (2007).
9:00 PM - II20.56
Synthesis of Nickel-nitrilotriacetic Acid Coupled Single-Walled Carbon Nanotubes for Directed Assembly with Poly-histidine Tagged Macromolecules.
Rachel Graff 1 , Michael Strano 1
1 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractNickel-nitrilotriacetic acid functionalized single walled carbon nanotubes have been synthesized for the directed assembly of poly-histidine tagged proteins onto the nanotube surface. Carbon nanotubes were first covalently functionalized with 4-carboxybenzene diazonium tetrafluoroborate that rendered them water soluble. The acid moieties on the carbon nanotube were covalently reacted with Nα,Nα-Bis(carboxymethyl)-L-lysine hydrate forming amide bonds to the nanotube complex. The nitrilotriacetic acid (NTA) moiety of the Nα,Nα-Bis(carboxymethyl)-L-lysine was complexed with nickel and used to specifically bind a poly-histidine-tagged photosynthetic reaction center (RC) from Rhodobacter sphaeroides. We demonstrate that the histidine-tagged RC protein specifically binds to SWNT-NTA-Ni and that the free RC-His in solution can be removed though histidine binding to Ni-NTA-agarose resin removed by filtration. The binding is reversible via addition of imidazole. The approach allows one to reversibly dock a carbon nanotube regioselectively to a His-tagged protein.
9:00 PM - II20.57
Purification and Chemical Functionalization of Boron Nitride Nnanotubes.
Aude Maguer 1 3 , Eric Doris 3 , Lionel Bresson 1 , Jean-Lou Cochon 2 , Charles Mioskowski 3 , Annick Loiseau 1
1 , LEM/ONERA, Chatillon France, 3 , CEA Saclay DSV/iBiTec-S/SCBM, Gif sur Yvette France, 2 , DMSC/ONERA, Palaiseau France
Show AbstractBoron nitride nanotubes are new tubular materials which are structurally related to carbon nanotubes and are made of one or several rolled-up hexagonal boron nitride sheets. Nanoelectronics, material science and medicine are among the potential application fields of these tubular structures. Single-walled boron nitride nanotubes (SWBNNTs) are being produced by continuous LASER ablation at the ONERA. The crude samples contain SWBNNTs and boron nitride cages but are also contaminated by boric acid and hexagonal boron nitride fragments. A purification method of these samples has been developed in order to get on one hand nanotube-enriched samples and on the other hand boron nitride cages. The process includes multiple cycles of sonication, centrifugation and filtration and has been shown to be efficient for different types of boron nitride nanotubes samples. Thanks to the presence of boron and nitrogen atoms that promise better reactivity than carbon, boron nitride nanotubes are expected to be good candidates for chemical functionalization. In addition, most of the foreseen applications require their dispersibility and compatibility with different solvents. Exohedral chemical functionalization of boron nitride nanostructures allows, as for carbon nanotubes, their suspension and solubilization in either aqueous or organic conditions. New methods of functionalization have been developed and applied to boron nitride cages, multi-walled and single-walled boron nitride nanotubes samples. Two different methods involve either strong interactions with the boron electron vacancy or stacking of a borazinic cycle on the boron nitride network. The efficiency of functionalization is demonstrated by macroscopic solubilization in organic solvents and transmission electron microscopy studies and its reversibility can be proven by dialysis against the corresponding organic solvent. Additional analysis methods in order to further confirm the functionalization are currently under evaluation.
9:00 PM - II20.58
Enhancement of Photoluminescence for Hybrid Nanotubes of Polymer Nanotubes Enveloped by Metal Nanotubes.
Jinsoo Joo 1 , Dong Hyuk Park 2 , Yong Baek Lee 3 , Hyun Seung Kim 4 , Dae Chul Kim 5 , Hyun Jun Kim 6 , Jeongyong Kim 7
1 Physics, Korea University, Seoul Korea (the Republic of), 2 Physics, Korea University, Seoul Korea (the Republic of), 3 Physics, Korea University, Seoul Korea (the Republic of), 4 Physics, Korea University, Seoul Korea (the Republic of), 5 Physics, University of Incheon, Incheon Korea (the Republic of), 6 Physics, University of Incheon, Incheon Korea (the Republic of), 7 Physics, University of Incheon, Incheon Korea (the Republic of)
Show AbstractWe observed an approximately hundred-fold enhancement of the peak intensity of photoluminescence for a single strand of light emitting polymers; polythiophene or poly (3-methylthiophene) nanotubes, coated with nanoscale copper, nickel, or cobalt metal; and so called - coaxial polymer and inorganic metal hybrid nanotubes. The photoluminescence for doped poly (3-methylthiophene) nanotubes also increased through nanoscale metal coating. This enhancement was determined through laser confocal microscope photoluminescence measurements with a high spatial resolution. For the coaxial hybrid nanotubes, the polymer nanotubes were electrochemically polymerized using a nanoporous template. The metals with nanoscale thickness were sequentially electrochemically deposited onto the polymer nanotubes. The hybrid nanotubes were visualized and confirmed through scanning electron microscope, transmission electron microscope (TEM), high-resolution (HR)-TEM, and elemental analysis. The enhancement of the photoluminescence might originate from the surface plasmon (SP) on the hybrid nanotubes. From ultra-violet and visible absorption spectra and calculations of local electric field enhancement for the hybrid nanostructures, the SP effects contributed to the enhancement of PL. The SP enhanced – PL of polymer and metal hybrid nanotubes could be significantly applied to organic based displays and nanoscale optoelectronics.
9:00 PM - II20.6
High Sensitive Carbon Nanotube Arrayed NO2 Gas Detector.
Joondong Kim 1 , Jin-Won Song 1 , Yeo-Hwan Yoon 1 , Young–Hyun Shin 1 , Eung-Sug Lee 1 , Chang-Soo Han 1
1 Nano-Mechanical Systems Research Center, Korea Institute of Machinery and Materials, Daejeon Korea (the Republic of)
Show Abstract9:00 PM - II20.7
Direct Assembly of Modified Proteins on Carbon Nanotubes in an Aqueous Solution.
Jae-Woo Kim 1 , Peter Lillehei 2 , Cheol Park 1 , Joycelyn Harrison 2
1 , National Institute of Aerospace, Hampton, Virginia, United States, 2 Advanced Materials and Processing Branch, NASA LaRC, Hampton, Virginia, United States
Show AbstractCarbon nanotubes (CNTs) have superior mechanical and electrical properties that have opened up many potential applications. However, poor dispersibility and solubility, due to the substantial van der Waals attraction between tubes, have prevented the use of CNTs in practical applications, especially biotechnology applications. Effective dispersion of CNTs into small bundles or individual tubes in solvents is crucial to ensure homogeneous properties and enable practical applications. In addition to dispersion of CNTs into a solvent, the selection of appropriate solvent, which is compatible with a desired matrix, is an important factor to improve the mechanical, thermal, optical, and electrical properties of CNT-based fibers and composites. In particular, dispersion of CNTs into an aqueous system has been a challenge due to the hydrophobic nature of CNTs. Here we describe an effective method for dispersion of both single wall CNTs (SWNTs) and few wall CNTs (FWNTs) in an aqueous buffer solution. We also show an assembly of cationized Pt-cored ferritins on the well dispersed CNTs in an aqueous buffer solution.
9:00 PM - II20.8
Vertcally Aligned Carbon Nanotube Arrays for Room Temperature Sensing of Ammonia and DMMP.
Suresh Rajaputra 1 2 , Ning Ma 1 , Raghu Mangu 1 2 , Patrcia Clore 1 2 , Dali Qian 3 , Rodney Andrews 3 , Janet Lumpp 1 , Vijay Singh 1 2
1 electrical & Computer Engineering, University of Kentucky, Lexington, Kentucky, United States, 2 Center for nanoscale Science & Engineering, University of Kentucky, Lexington, Kentucky, United States, 3 Center for Applied Energy Research, University of Kentucky, Lexingtoin, Kentucky, United States
Show AbstractVertically aligned carbon nanotube (CNT) arrays were fabricated by chemical vapor deposition in anodized aluminum oxide (AAO) templates without the use of a catalyst. The width of the CNT core was varied in the 2 nm – 40 nm range by controlling the pore size and inter-pore spacing in highly ordered AAO templates. Next, CNT/AAO arrays were integrated into both capacitive and resitive sensor designs for detecting ammonia, carbon dioxide and DMMP at room temperature. The response of CNT/AAO arrays to NH3, CO2 and DMMP at room temperature was measured. The sensor response was measured for concentrations ranging from 10 ppm to 5% ammonia in Nitrogen. Steady state values of 9% and 5% for room temperature sensitivity to 5% ammonia and 1% ammonia respectively, were obtained. Variations in the device resistance in test gas environments were interpreted in terms of a model where the multi-walled carbon nanotubes (MWCNTs) were thought to behave as p-type semiconductors. An analytical model for the sensor response was developed. The sensor response was correlated with the AAO template pore diameter, nanotube diameter and nanotube length.
9:00 PM - II20.9
Single-walled Nanotube Network based Hydrogen Sensors and Photodetectors.
Hau Wang 1 , Yugang Sun 2 , Chiun-Teh Ho 1 3 , Wei-Shan Hu 1 4 , Russell Cook 1 , Randall Meyer 3 , Yu-Tai Tao 4
1 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States, 2 Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois, United States, 3 Department of Chemical Engineering, University of Illinois at Chicago, Chicago, Illinois, United States, 4 Department of Chemistry, National Tsing-Hua University, Hsin-Chu Taiwan
Show AbstractSensors are playing a major role in safety devices, medical diagnosis, environmental control, manufacturing and security industries. Carbon nanotubes due to their small sizes, high surface areas, modest electrical conductivity, etc., became an ideal substrate for various sensing materials. In our current studies, random network of single-walled carbon nanotubes (SWNTs) was used to build a percolation pathway for charge transport. We have studied both commercial CVD SWNT drop coated thin films as well as SWNT network prepared with use of dry-transfer technique. Typical SWNTs have diameters between 1.5 and 2.5 nm as measured with AFM. When these SWNTs were thermally evaporated or electrochemically decorated with Pd nanoparticles, they became ultra-sensitive ambient temperature hydrogen sensors (Appl. Phys. Lett. 90, 213107 2007). We found the sensitivity is much higher than pure Pd thin film or Pd nanotube H2 sensors. In addition, both SiO2/Si wafer substrate and flexible plastic polyethylene terephthalate (PET) substrate were prepared. The flexible hydrogen sensors showed very good mechanical durability. We also found that SWNT network showed fast optical responses. These results with infrared-sensitive PbSe, PbTe nanoparticle decorated SWNT network will be presented.Work at Argonne National Laboratory as well as FESEM carried out at EMC are supported by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357.