Symposium Organizers
JoseAntonio Garrido Technische Universitaet Muenchen
Ken Haenen Hasselt University
Dean Ho Northwestern University
Kian Ping Loh National University of Singapore
Symposium Support
Institute for Materials Research (IMO)/IMOMEC-Hasselt University/IMEC vzw
Nanosystems Initiative Munich (NIM)
Seki Technotron USA
Technische Universitaet Muenchen
QQ1: Carbon Nanomaterials
Session Chairs
Tuesday PM, April 26, 2011
Room 3014 (Moscone West)
9:30 AM - **QQ1.1
Fundamentals and Applications of Monodisperse Carbon Nanomaterials.
Mark Hersam 1
1 Materials Science and Engineering, Northwestern University, Evanston, Illinois, United States
Show AbstractCarbon nanomaterials have attracted significant attention due to their potential to improve applications such as transistors, transparent conductors, solar cells, batteries, and biosensors [1]. This talk will highlight our latest efforts to develop solution-phase strategies for purifying, functionalizing, and assembling carbon nanomaterials into functional arrays. For example, we have recently developed [2] and commercialized [3] a scalable technique for sorting surfactant-encapsulated single-walled carbon nanotubes (SWCNTs) by their physical and electronic structure using density gradient ultracentrifugation (DGU). The resulting monodisperse SWCNTs enhance the performance of thin film transistors [4], infrared optoelectronic devices [4], and transparent conductors [5]. The DGU technique also enables multi-walled carbon nanotubes to be sorted by the number of walls [6], and solution phase graphene to be sorted by thickness [7], thus expanding the suite of monodisperse carbon nanomaterials. By extending our DGU efforts to carbon nanotubes and graphene dispersed in biocompatible polymers (e.g., DNA, Pluronics, Tetronics, etc.) [8], new opportunities have emerged for monodisperse carbon nanomaterials in biomedical applications.[1] J. Liu and M. C. Hersam, MRS Bulletin, 35, 315 (2010).[2] M. C. Hersam, Nature Nanotechnology, 3, 387 (2008).[3] http://www.nanointegris.com/[4] M. Engel, et al., ACS Nano, 2, 2445 (2008).[5] A. A. Green and M. C. Hersam, Nano Letters, 8, 1417 (2008).[6] A. A. Green and M. C. Hersam, Nature Nanotechnology, 4, 64 (2009).[7] A. A. Green and M. C. Hersam, Nano Letters, 9, 4031 (2009).[8] A. L. Antaris, et al., ACS Nano, 4, 4725 (2010).
10:00 AM - **QQ1.2
Nitrogen Vacancy Centers in Nano-scale Diamonds.
James Rabeau 1
1 Centre for Engineered Quantum Systems, Department of Physics and Astronomy, Macquarie University, Sydney, New South Wales, Australia
Show AbstractDiamond has been central to a number of new and exciting breakthroughs in quantum and biological science for the past several years. The underpinning feature of diamond that makes this possible is the ability to host bright and optically stable colour centres at room-temperature. Of the hundred or so optical defects in diamond, the nitrogen-vacancy (NV) centre has attracted the most attention primarily for its photo-stability, spin polarised optical transition and long spin coherence time. By combining and exploiting each of these in different ways, landmark demonstrations have been made including single photon emission, spin qubits, magnetometry and bright fluorescent biolabels.Recent experiments show that the properties of NV centers in extremely small host diamond crystals are not the same as what is observed in larger or bulk crystals [1]. Here we report on methods for exploring this behaviour in more detail and understanding what gives rise to the changes in optical behaviour. 1. C. Bradac, T. Gaebel, N, Naidoo, MJ Sellars, J. Twamley, LJ Brown, AS Barnard, T. Plakhotnik, AV Zvyagin, JR Rabeau, Nature Nanotechnology (2010) 5, 345-348, “Observation and control of blinking nitrogen vacancy centres in discrete nanodiamonds”
10:30 AM - **QQ1.3
The Carbon New Age.
Vitor Pereira 2 , Antonio Castro Neto 2 1
2 Graphene Research Centre, National University of Singapore, Singapore Singapore, 1 Department of Physics, Boston University, Boston, Massachusetts, United States
Show AbstractGraphene has been considered by many as a revolutionary material with electronic and structural properties that surpass conventional semiconductors and metals. Due to its superlative qualities, graphene is being considered as the reference material for a post-CMOS technology. Furthermore, graphene is also quite unusual electronically since its electric carriers behave as if they were massless and relativistic, the so-called Dirac particles. Because of its exotic electronic properties, theorists are being forced to revisit the conceptual basis for the theory of metals. Hence, graphene seems to be unveiling a new era in science and technology with still unseen consequences.
QQ2: Carbon Nanoelectronics
Session Chairs
Tuesday PM, April 26, 2011
Room 3014 (Moscone West)
11:30 AM - **QQ2.1
Electron Transport in Molecular Electronic Devices with Carbon Substrates.
Richard McCreery 1 2 , Andrew Bonifas 3 , Adam Bergren 2 , Haijun Yan 2 , Jie Ru 1 , Bryan Szeto 2
1 Chemistry, University of Alberta, Edmonton, Alberta, Canada, 2 , National Institute for Nanotechnology, Edmonton, Alberta, Canada, 3 , Ohio State University, Columbus, Ohio, United States
Show AbstractWe make “molecular junctions” consisting of aromatic molecules covalently bonded to disordered graphitic carbon substrates and completed with a Cu or Au “top contact”. The phenyl-phenyl bond present between the molecular layer and the substrate result in strong electronic coupling and good thermal stability. Microfabricated molecular junctions range from 2.5 x 2.5 to 400 x 400 um in area, and can withstand temperature excursions from 5 K to >450K without change in electronic behavior. Current voltage cycles are reproducible from sample to sample, yield is 90 – 100 %, and the devices may be voltammetrically scanned at least 109 cycles without observable changes in electronic behavior. The electronic characteristics of the junctions depend strongly on the structure and thickness of the molecular layer, but are weakly dependent on temperature. A detailed analysis of the conduction mechanism indicates that transport is consistent with tunneling of holes through the molecular HOMO, and governed by a modified Simmons relationship. However, the strong electronic coupling between the molecules, carbon substrate, and top contact result in a dielectric constant and HOMO energy which varies with the thickness of the molecular layer. The case of a carbon substrate, aromatic molecule, and carbon top contact is particularly interesting, since it represents a nonmetallic junction with conjugation maintained throughout the device. Not only does this device avoid possibly problematic metals, but it also represents an electronic system with a unique structure and unusual electron transport properties.(1)Bonifas, A. P.; McCreery, R. L.; Nat Nano 2010, 5, 612.(2)Bergren, A. J.; McCreery, R. L.; Stoyanov, S. R.; Gusarov, S.; Kovalenko, A.; J. Phys. Chem. C 2010, 114, 15806.(3)Yan, H.; McCreery, R. L.; ACS Applied Materials & Interfaces 2009, 1, 443.(4)McCreery, R. L.; Bergren, A. J.; Advanced Materials 2009, 21, 4303.(5)McCreery, R.; Wu, J.; Kalakodimi, R. J.; Phys. Chem. Chem. Physics. 2006, 8, 2572.
12:00 PM - QQ2.2
Carbon Composite Hybrid Electrodes for Energy Storage and Conversion.
Andrew Minett 1 , Peter Sherrell 1 , Joselito Razal 1 , Jun Chen 1
1 , University of Wollongong, Wollongong, New South Wales, Australia
Show AbstractThe development of new materials for electrochemical devices, including hydrogen fuel cells, lithium ion batteries and super-capacitors, is of great importance as society becomes ever dependant on more powerful portable energy devices. Over the past 20 years sp2 hybridised carbon systems, such as fullerenes, carbon nanotubes (CNTs) and graphene, have emerged as possible electrode materials for these devices. However, significant impediments in terms of processability, reproducibility and cost have prevented widespread production of commercial CNT electrodes.We have recently reported on the production and modification of a range of carbon nanotube and carbon nanotube-composite materials that act as hybrid energy storage/conversion devices. That is, materials with both high energy and power densities suitable for use in a range of applications. To demonstrate the versatility of these carbon composite electrodes, the introduction of metal nanoparticles for catalysis or enhanced electrochemical properties allows the use of these electrodes as either the anode or cathode in fuel cells or Li-ion batteries or as supercapacitor electrodes. Eight different metals have been deposited as nanoparticles or alloys by a simple microwave assisted polyol reduction method resulting in nanoparticle sizes as small as 4nm. Through XPS and EPR studies, these nanoparticle-CNT composites have shown remarkable cyclic stability essential for long term applications. Most importantly, energy densities of ~70Wh/kg at power densities up to ~10kW/kg for these composite electrodes highlight their promise for future commercial energy applications.
12:15 PM - QQ2.3
The Role of Nanotube Structure and Architecture on Electron Transfer at Carbon Nanotube Electrodes.
Jeff Martin 2 , Michael Roberts 1 , Ian Kinloch 1 , Robert Dryfe 2
2 School of Chemistry, University of Manchester, Manchester United Kingdom, 1 School of Materials, University of Manchester, Manchester United Kingdom
Show AbstractCarbon electrodes are at the heart of the majority of power devices and sensors. However, the electron transfer process between the carbon electrodes and the redox species in the electrolyte is still very poorly understood. In particular there is debate in the nanotube field on whether the carbon nanotubes have specific electrocatalytic properties or their increased performance compared to HOPG is due to the architecture of the nanotube electrodes (e.g. pore size and small cell effects). This paper will address this key question by drawing conclusions from a range of systems, including electrochemical hydrogen storage [1], enzyme-fuel cells (lacasse-nanotube direct electron transfer half cell) and fundamental studies.
Aligned arrays of multiwalled nanotubes were used as a model system. The nanotubes were grown on an oxidised silicon wafer by the pyrolysis of ferrocene and toluene. The arrays were then removed and a platinum wire attached to them to form the working electrode. Random aligned electrodes were also produced by making bucky paper from the same nanotubes. The surface chemistry of the nanotubes was varied by gas phase chemistry to give a range of water contact angles between 0 and 140°. This gas phase approach ensured that the aligned morphology of the nanotubes was preserved during the functionalisation. The electron transfer kinetics at the nanotubes were studied using cyclic voltammetry and chronoamperometry. A range of redox couples were used so that the effect of electrolyte (aqueous and organic) and ion sizes could be explored. The pores between the nanotubes appeared to have a significant effect on the electrochemical reponses of the nanotubes, which was confirmed by filling the pores between the nanotubes with paraffin wax. Finally, the role of the diffusion of species through the electrodes was studied by making electrodes with a hierarchy of pore sizes. These hierarchical electrodes were produced by sputtering platinum squares onto the silicon oxide substrate prior to nanotubes growth through a TEM mesh, so that the nanotubes arrays grew in the uncoated regions to form a grid.
[1] Are Carbon Nanotubes Viable Materials for the Electrochemical Storage of Hydrogen?, J.B. Martin, I.A. Kinloch, R.A.W. Dryfe, J. Phys. Chem C, 114 (10), 4693-4703, 2010
12:30 PM - QQ2.4
Direct Formation of Graphene-metal Hybrid on Dielectric Substrates by Metal-induced Crystallization.
Seong-Yong Cho 1 , Hyun-Mi Kim 1 , Min-Hyun Lee 1 , Do-Joong Lee 1 , Hong H. Lee 2 , Ki-Bum Kim 1 3
1 Materials Science and Engineering, Seoul National University, Seoul Korea (the Republic of), 2 School of Chemical and Biological Engineering, Seoul National University, Seoul Korea (the Republic of), 3 WCU Hybrid Materials Program, Department of Materials Science and Engineering, Seoul National University, Seoul Korea (the Republic of)
Show AbstractForming a graphene layer, single or multiple, directly on any surface, in particular on dielectric surface, is an issue yet to be resolved. Typically, the graphene layer has been formed on metals, and semiconductors, and then transferred onto a dielectric layer for device applications. Fabrication of graphene on dielectric surface was suggested by CVD and followed sublimation of whole copper catalyst, but it requires relatively long time to get rid of all the metal catalyst. The ability to form a graphene layer directly on any surface including dielectrics would greatly ease the complexity involved in device fabrication. One way of forming a graphene film is to utilize crystallization of an as-deposited amorphous carbon (a-C) layer to graphene layer that is catalyzed by a metal. The crystallization of a-C to graphitic structure can be traced to earlier studies in which the conversion of disordered carbons to graphite was accelerated by metals. For example, a-C was converted to graphite at 880C with Pd particles as a catalyst. Recently, a continuous Ni film was utilized to produce graphene at 650-950C. Studies have shown that a physical contact is needed between the metal and a-C for the crystallization, which in not surprising for the catalytic activity, and therefore the crystallization can occur along the path traced by the metal particles when they migrate. Catalysts attributes to lowering the temperature process which is 900~1000C for CVD process, thus relatively lower temperature process is desirable in device fabrication step. These studies suggest that if a thin continuous metal film on the a-C film is used for the crystallization such that the metal film splits into small crystallites in the course of annealing, continuous graphene-metal hybrid structure can be obtained on dielectric surface directly. The essence lies in the metal layer which will be broken-up being used as a hybrid material being used as a catalyst for the crystallization. The procedure involved is just to deposit a thin layer of a-C on a given surface followed by deposition of another layer of a metal such as Ni and then simply to anneal to 500-600C. No transfer of the film to insulating substrate is involved.
QQ4: Devices I
Session Chairs
Tuesday PM, April 26, 2011
Room 3014 (Moscone West)
4:30 PM - **QQ4.1
Functionalized Graphene Oxide for Resistive Switching Memory Device.
Byung Jin Cho 1 , Seul Ki Hong 1
1 Electrical Engineering, KAIST, Daejeon Korea (the Republic of)
Show AbstractResistive switching memory (ReRAM) has been widely investigated for future memory device because of its potential for high speed, low operation voltage and high packing density. Up to date, however, most of ReRAM was fabricated as MIM (metal-insulator-metal) structure where metal oxide was used as the insulator layer [1]. However, the ReRAM with metal oxide insulator does not provide possibility for the application to flexible electronics which is one of the most important directions for future electronic systems. In this work, we demonstrate that functionalized graphene oxide (GO) can successfully be used for flexible resistive switching memory devices. GO was synthesized by modified Hummers method [2]. Then, the graphene oxide layer was spin coated on the bottom electrode using a solution containing graphene oxide particles, H2O, and methanol. A special surface treatment on the metal electrode is done prior to GO spin coating to improve the adhesion and uniformity of the GO layer on the electrode material. The GO memory device with the optimized GO thickness can show good resistive switching characteristics such as ~103 on/off current ratio and excellent retention performance. In addition, the device possesses excellent flexibility, showing no degradation of memory performance even when the device is bent down to 4 mm radii and applied more than 1000 times of bending. However, it has been found that the MIM structure with GO insulator exhibits the switching operation only with some selected metal electrode combinations such as Al and ITO. Detailed investigation on such electrode dependence suggests that the interface between GO layer and the metal electrode is the critical factor to determine the occurrence of the switching operation. For the device with the electrodes which exhibit the switching operation, the set/reset operation is dominated by the movement of oxygen near the GO interface. However, the factor to determine the reliability of the GO memory is found to be the formation of conduction filament by the diffusion of metal ions from the electrode into the GO layer.
5:00 PM - QQ4.2
Graphene Photonic Circuit: Light Creation, Modulating and Detection.
Qiaoliang Bao 1 , Kian Ping Loh 1
1 Department of Chemistry, National University of Singapore, Singapore Singapore
Show AbstractGraphene has attracted enormous research interests due to its exceptional electronic transport properties and potential applications in nanoelectronics. The photonic properties of graphene are equally remarkable. Its universal optical conductance is defined by the fine structure constant and is independent of frequency over a wide range.Its zero-gap nature affords benefits the high bandwidth detection of light.[1] The easy saturation of its absorption due to Pauli blocking enables graphene to be used as saturable absorbers in broadband, ultrafast mode-locked lasers for telecommunication.[2,3] The two dimensional (2D) nature of graphene enables the design of photonic circuits with ultrathin channels, where graphene can assume different functions of light creation, routing or modulation and detection. Here we will review our recent progress to develop graphene photonic devices, which include mode-locked laser, light modulator and photodetector. Firstly we would like to review our initiative works on graphene mode-locked lasers. Due to wavelength independent saturable absorption in visible-to-near-infrared range, wide-band tuneable lasers were invented to generate ultra-short pulses in telecommunication C band (around 1550 nm)[2,3] as well as even short near-infrared wavelength at 1050 nm[4]. Stable mode locked pulses with single pulse energy up to 7.3 nJ and pulse width of 415 fs have been directly generated from the laser.[5] Secondly, we experimentally and theoretically investigated the interaction between graphene and transverse electromagnetic wave. By tuning the chemical potential of graphene, the sign of complex dynamics conductivity can be varied sensitively at infrared frequencies, which allow varying amount of contribution from intraband and interband conductivities, leading to certain modulation of light during propagation.[6] Last, we report our recent work in graphene-based photodetector. The use of graphene nanoribbons with a transport bandgap enables us to significantly suppress the dark current in phototransistor, which affords much larger signal-to-noise ratio and improved responsivity. We also highlight our progress in fabricating a printable graphene-TiO2 hybrid film for high-gain photodetection.[7] Reference:[1] Mueller, T., Xia, F. N. A. & Avouris, P. Nature Photonics 2010 4, 297-301.[2] Bao, Q., Zhang, H., Wang, Y., Ni, Z., Yan, Y., Shen, Z. X., Loh, K. P. & Tang, D. Y. Adv. Funct. Mater. 2009 19, 3077-3083.[3] Bao, Q., Zhang, H., Yang, J. X., Wang, S., Tang, D. Y., Jose, R., Ramakrishna, S., Lim, C. T. & Loh, K. P. Adv. Funct. Mater. 2010 20, 782-791.[4] Zhao, L., Tang, D. Y., Zhang, H., Wu, X., Bao, Q. & Loh, K. P. Opt. Lett. 2010 In press.[5] Zhang, H., Tang, D. Y., Zhao, L. M., Bao, Q. & Loh, K. P. Opt. Express 2009 17, 17630-17635.[6] Bao, Q. & Loh, K. P. In preparation 2010.[7] Manga, K. K., Wang, S., Jaiswal, M., Bao, Q. & Loh, K. P. Adv. Mater. 2010 In press.
5:15 PM - QQ4.3
Elastic Properties of Single Layer CVD Graphene Sheets.
Xiao Liu 1 , Thomas Metcalf 1 , Jeremy Robinson 1 , F. Perkins 1 , Brian Houston 1
1 , Naval Research Laboratory, Washington, DC, District of Columbia, United States
Show AbstractLarge-area, single-layer graphene sheets (SLGS) (~90-95% single layer) were produced by chemical vapor deposition (CVD) on copper foil. The SLGSs were removed from the Cu foil and re-deposited onto a high-Q, single-crystal silicon mechanical double-paddle oscillator. The surface of silicon oscillators were either hydrogen terminated (hydrophobic) or cleaned in oxygen plasma (hydrophilic). The oscillator has an extremely low background internal friction (~ 2×10-8) below 10 K, oscillating at ~5500 Hz in a mostly (~92%) torsional mode. The internal friction and shear modulus of the SLGSs were extracted from the change in resonance frequency and mechanical loss of the oscillators at low temperatures before and after an anneal at 300°C. The shear modulus for CVD grown SLGS is found to be approximately three times larger than that of multilayered reduced graphene oxide and CVD grown graphene on nickel with thicknesses varying from 5 nm to 90 nm reported earlier [1]. The internal friction of CVD grown SLGS on copper is found to be negligible within the uncertainty of the technique, and is much smaller than that of the multilayered reduced graphene oxide and CVD grown graphene on Nickel, where internal friction is as large as that of amorphous solids. Neither annealing nor surface treatments of silicon oscillators has a measurable effect on either the shear modulus or internal friction. This minimizes any possible film adhesion related impact to the measurement results. The measured shear modulus also agrees with recent theoretical calculations on SLGSs [3,4] and is approximately 200 GPa.[1] Xiao Liu, J.T. Robinson, Z. Wei, P.E. Sheehan, B.H. Houston, E.S. Snow, Diamond Relat. Mater. 19, 875 (2010).[2] J.T. Robinson, M. Zalalutdinov, J.W. Baldwin, E.S. Snow, Z. Wei, P. Sheehan, B.H.Houston, Nano Lett. 8, 3820 (1997).[3] F. Scarpa, S. Adhikari, A.S. Phani, Nanotechnology 20, 065709 (2009).[4] A. Sakhaee-Pour, Solid State Commun. 149, 91 (2009).* Work supported by the Office of Naval Research
5:30 PM - QQ4.4
Electrical Charging of Diamond/Water and Graphene/Water Interfaces.
Markus Dankerl 1 , Lucas Hess 1 , Moritz Hauf 1 , Stefan Birner 1 , Ian Sharp 1 , Martin Stutzmann 1 , Jose Garrido 1
1 Walter Schottky Institut, Technische Universität München, Garching Germany
Show AbstractDiamond and, more recently, graphene have been used for the fabrication of solution-gated field effect transistors (SGFETs), which have potential application in biosensing and bioelectronics. On the one hand, diamond SGFETs show excellent stability and very low electronic noise level. Graphene SGFETs, in addition to relatively low electronic noise levels, offer a very high sensitivity (mainly due to the high mobility of charge carriers) and a facile integration with flexible substrates, and thus having the potential to revolutionize the field of implantable devices. Despite the increasing use of SGFETs based on these two materials, a detailed understanding on how these devices work is still missing. In contrast to the well known MOSFET, where the conductive channel is separated from the gate electrode by an oxide or insulating film, in diamond and graphene SGFETs no insulator is used between the electronic material and the electrolyte. Instead, the ability of the diamond/electrolyte and graphene/electrolyte interfaces to behave as quasi-perfectly polarizable interfaces enables the capacitive charging in these structures. Thus, the gate capacitance of diamond and graphene SGFETs is no longer governed by the oxide but by the double layer formed between the material and the electrolyte. In this context, it is of uttermost importance to understand the double layer formation at the diamond/electrolyte and graphene/electrolyte interfaces. In this contribution, we will discuss our work on the characterization of diamond and graphene solution-gated field effect structures, as well as on the modeling of the diamond/electrolyte and graphene/electrolyte interfaces. Hall effect experiments performed in electrolyte allow us to have access to the modulation of the charge carriers as a function of the electrolyte gate potential. We have found that in order to understand the experimentally determined charging of the electronic material, a detailed description of the water structure in the vicinity of the hydrophobic diamond and graphene surfaces has to be taken into account. Using a numerical approach, we have determined the distribution of charges and potential across the diamond/electrolyte and graphene/electrolyte interfaces. The simulation results are in very good agreement with the experiments when an extended Poisson-Boltzmann distribution for ions in the electrolyte was considered, which takes into account the effect of the hydrophobic surfaces on the water dielectric constant, as well as specific interactions between the electrolyte ions and the solid surfaces.Our results demonstrate the importance of the hydrophobic nature of the diamond and graphene surfaces on the operation on SGFETs based on these carbon materials.
Symposium Organizers
JoseAntonio Garrido Technische Universitaet Muenchen
Ken Haenen Hasselt University
Dean Ho Northwestern University
Kian Ping Loh National University of Singapore
Symposium Support
Institute for Materials Research (IMO)/IMOMEC-Hasselt University/IMEC vzw
Nanosystems Initiative Munich (NIM)
Seki Technotron USA
Technische Universitaet Muenchen
QQ9: Poster Session: Carbon Functional Interfaces
Session Chairs
Jose Garrido
Ken Haenen
Dean Ho
Wednesday PM, April 27, 2011
Salons 7-9 (Marriott)
9:00 PM - QQ9.11
New Solvents for Single Walled Carbon Nanotube Dispersions.
Soumendra Barman 1 , Michael Vosgueritchian 1 , Arjan Zoombelt 1 , Zhenan Bao 1
1 Chemical Enginering, Stanford University, Stanford, California, United States
Show AbstractSingle walled carbon nanotubes (SWNTs) posses great potential for applications ranging from composite materials, sensors, flexible computing networks and transparent conducting electrodes. However, these next generation applications can only manufactured cost effectively if SWNTS are able to individually dispersed into solutions. Here, we explore SWNT dispersions utilizing new solvent systems and fabricate conductive films from these dispersions. UV-vis-NIR spectroscopy, Raman spectroscopy, AFM and semiconductor parameter analysis were used to experimentally characterize the results. We also use computational tools to explore charge transfer at the interface between the SWNT and solvent. The knowledge gained from this study can be used to open a new class of solvents for manufacturing as well as understand the fundamental mechanism for SWNT dispersion in organic solvents.
9:00 PM - QQ9.12
Cellulose Nanoparticle Mediated Dispersion of Single Walled Carbon Nanotube (SWCNT) and Elaboration of SWCNT /Cellulose Nanocrystals (CN) Multilayered Thin Films.
Christophe Olivier 1 2 , Olivier Chauvet 2 , Herve Bizot 1 , Bernard Cathala 1
1 UR 1268, Biopolymères, Interactions et Assemblages, INRA, Nantes France, 2 Institut des Matériaux de Nantes, IMN, UMR 6502 CNRS Université de Nantes, Nantes France
Show AbstractThe unique properties of single-walled carbon nanotubes (SWCNTs) have open opportunities to elaborate new composites with optimized properties such as high mechanical strength, electrical conductivity, and optical properties. SWCNTs have been involved in many studies. However limitations remain and for instance SWCNTs are well known to be poorly dispersible down to individual state in water rendering the elaboration of materials in aqueous environment difficult. To address this problem, the formation of complexes between SWCNTs and biopolymers has been investigated. A large number of complexes have already been prepared with protein, peptides, nucleic acids or polysaccharides. In this study, for the first time, we report the dispersion of SWCNTs by cellulose nanocrytals (CNs). Highly crystalline cellulose possesses outstanding physical properties such as high mechanical resistance and low density, and moreover benefits from tremendous natural abundance. Cellulose occurs in plant cell walls in the form of slender microfibrils, which are combined with other biomacromolecules to form supramolecular assemblies in which they that act as reinforcing network. Cellulose nanocrystals (CNs) are typically obtained from sulfuric acid hydrolysis of microfibrils that yields negatively charged short crystalline rods with a cross section between 3 and 20 nm and a length between 100 nm and several micrometers, depending on the biological origin. SWNTs dispersions were obtained after ultrasonication in CNs colloidal suspension and they were found to be stable during several months. Similarly to CNs suspension, SWNTs/CNs dispersions were used to elaborate multilayered thin films by the layer by layer method. Characterization of the dispersion, growth pattern of the films, Raman and optical properties of the films were investigated. Up to 8 bilayers, films of about 150 nm thick have been obtained. These films exhibit a deep blue color. The presence of isolated SWNTs in each bilayer is attested by characteristic Raman and luminescence signals. These films may be interesting for sensing applications energy storage or capture applications
9:00 PM - QQ9.13
Spectroscopic Identification of Bond Strain and π Interactions in a Series of Saturated Carbon-cage Molecules: Adamantane, Twistane, Octahedrane, and Cubane.
Trevor Willey 1 , Jonathan R. I. Lee 1 , Lasse Landt 4 1 , Daniel Brehmer 3 , Peter Schreiner 2 , Andrey Fokin 2 , Boryslav Tkachenko 2 , Nataliya Fokina 2 , Tony van Buuren 1
1 Condensed Matter and Materials Division, Lawrence Livermore National Laboratory, Livermore, California, United States, 4 , Technical University of Berlin, Berlin Germany, 3 SSRL, Stanford Linear Accelerator Center, Menlo Park, California, United States, 2 , Justus-Liebig University, Giessen Germany
Show AbstractNovel nanocarbons such as fullerenes, nanotubes, graphene, and nanodiamond reside at the cutting edge of nanoscience and technology. Along with chemical functionalization, geometrical constraints (such as extreme curvature in nanotubes or graphene, or defects within or at the surfaces of nanodiamond crystallites) can modify the electronic states of the nanocarbon material. Understanding the effects of bond strain on electronic structure is critical to developing nanoelectronic applications based on these materials. This paper presents a fundamental study of how bond strain affects electronic structure in a benchmark series of novel saturated carbon cage compounds. Adamantane, C10H16, the smallest diamondoid, and arguably the smallest nanodiamond crystallite, has carbon atoms essentially commensurate with diamond lattice positions and possesses by far the least bond strain of the series. Twistane has the same stoichiometry (C10H16), but introduces some strain into the cage. Octahedrane (C12H12) and cubane (C8H8) contain increasing amounts of bond strain, culminating in cubane where carbon-carbon bonds lie either parallel, or orthogonal to one another. Using gas-phase near-edge x-ray absorption fine structure spectroscopy to probe the unoccupied electronic states, we observe two major progressions across this series. First, a broad C-C σ* resonance in the absorption splits into two more narrow and intense resonances with increasing strain. Second, the first manifold of states previously associated with tertiary C-H σ* in the diamondoid series appears to broaden and shift to lower energy. This feature is more than twice as intense in cubane as octadedrane, even though these two molecules have similar stoichiometries (CxHx). The differences are entirely due to the shape rather than stoichiometry of the molecules, and we believe the larger intensity indicates a high degree of π interaction between parallel C-C bonds in the cubane.
9:00 PM - QQ9.14
Optical Properties of Carbon Nanoparticles.
Nikolay Melnik 1
1 , P.N.Lebedev Physical Institute RAS, Moscow Russian Federation
Show AbstractSamples of carbon nanoparticles obtained by different technologies (carbon plasma deposition, irradiation, anodic etching etc.) by Raman scattering and photoluminescence were studied. Typically, the nanoparticle is surrounded by a shell of another substance. We propose the following mechanism of the nanoparticle+environment photoluminescence: first the nanoparticle absorbs light, further excitation is transmitted to the external cover or environment where photorecombination occurs. The aim of this research is to check this mechanism.Research of the first- and second-order Raman scattering in various carbon samples (porous graphite, disorder and irradiation carbon) has shown that there are particles in which exist the core containing the carbon atoms with SP2-bound (“graphite-like” structure), and the external cover contains SP3-bound ("diamond-like" structure). Such particles cause a photoluminescence in visible region. In this case “graphite-like” core absorbs a photon, then the excitation is transferred to the “diamond-like” shell where the photorecombination occurs.Optical properties of natural diamonds irradiated electrons and helium ions are investigated. It is revealed, that at small doses of an irradiation intensity of a photoluminescence increases with dose increase. If the original diamond has a weak photoluminescence after an irradiation in a spectrum there is the intensive peak at 505nm which is responsible for the centers of radiating defects. In the beginning of an irradiation (at small dozes) inside of a diamond carbon particles with graphite structure surrounded with diamond structure carbon arise. Here the same graphite nanocluster absorbs a photon and the excitation is transferred to the diamond environment where photorecombination occurs.The optical properties of nanodiamonds with adsorbed biological molecules (lysozyme) are investigated. Nanodiamonds have a strong photoluminescence. Lysozyme molecules do not luminescence. However, the adsorption of lysozyme on the nanodiamonds surface changes the luminescence band shape. It is difficult to assume that the lysozyme molecule can greatly change in the nanodiamond physical properties at the room conditions. Usually there are carbon clusters on the surface of nanodiamonds, which absorb the exciting radiation and transmit the excitement in nanodiamonds. The presence of lysozyme molecules near the carbon cluster can change the nanodiamond excitation condition because of the interaction of biological molecules and graphite clusters. As a result, the changes of photoluminescence band shape of nanodiamond appear.Studies have shown that the nearest environment of nanoparticles can strongly affect the optical properties of nanoparticles. This is particularly evident when the size of nanoparticles becomes smaller than the size of the wave function excited state of the nanoparticle.
9:00 PM - QQ9.15
Charge Induced Macroscopic Strain Effects In Monolithic High-surface-area Carbon Aerogels.
Lihua Shao 1 3 , Juergen Biener 2 , H. Jin 1 , R. Viswanath 1 , T. Baumann 2 , A. Hamza 2 , J. Weissmueller 1 3
1 Institute of Nanotechnology, Karlsruhe Institute of Technology , Karlruhe Germany, 3 Institute of Materials Physics, Hamburg Technical University, Hamburg Germany, 2 Nanoscale Synthesis and Characterization Laboratory, Lawrence Livermore National Laboratory, Livermore, California, United States
Show AbstractHigh surface area materials such as bulk nanoporous materials are unique in a way that their surface and interface properties can start to dominate the overall material behavior. This allows one to design new functional materials with physical and chemical properties that are no longer determined by the bulk material, but that can be controlled by external variables. Here, we demonstrate that activated carbon aerogels (CAs) can be considered as an extreme case of such a material as they can be best described as a three-dimensional surface bulk material. Monolithic CAs are prepared through sol-gel polymerization of organic precursors that are subsequently supercritically dried and pyrolyzed in an inert atmosphere. Finally, the BET surface area can be increase to values in excess of 3000 m2/g by a thermal treatment in a carbon dioxide atmosphere. We show that charge injection in an electrochemical environment can change the surface electronic structure of this interface dominated material sufficiently to induce macroscopic strain effects, and that the observed length changes are comparable to those observed on more traditional piezoelectric materials.This work performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
9:00 PM - QQ9.16
Copper Crystallographic Dependence for Graphene Grown by Chemical Vapor Deposition.
Joshua Wood 1 2 3 , Scott Schmucker 1 2 , Austin Lyons 1 3 , Eric Pop 1 2 3 , Joseph Lyding 1 2
1 Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 2 , Beckman Institute, Urbana, Illinois, United States, 3 , Micro and Nanotechnology Laboratory, Urbana, Illinois, United States
Show AbstractGraphene grown on copper foils by chemical vapor deposition (CVD) has generated much interest due to wafer-scale processing and the prospect of large monolayer regions [1]. While these characteristics are promising, low carrier mobilities of ~4000 cm^2/(V*s) [1] and dendritic multilayer formation [2] suggest that the underlying Cu substrate interacts strongly with nucleating carbon species during graphene CVD. The Cu surface structure determines nucleation sites and the overall number of graphene grains, ultimately establishing the graphene’s structural integrity and carrier mobility. Most of these CVD processes employ polycrystalline Cu foil, which forms polycrystalline facets when annealed in Ar/H2 at temperatures at ~1000°C. Therefore, we grew graphene on dead-soft annealed, 99.9% pure Cu foils at 1000°C. The foil is patterned with Cu registration mesas by lithography and etching in oxone monopersulfate. After growth, we characterized a Cu mesa with electron backscatter diffraction (EBSD), Raman spectroscopy, and atomic force microscopy (AFM) techniques. EBSD data reveals the grain boundaries, annealing twins, and crystallographic facets of the Cu-graphene mesa, with the Cu(110) surface covering most of the mesa. Nonetheless, the mesa is crystallographically diverse, including (001), (232) and (443) annealing twins and (362), (111), and (441) facets. At 633 nm excitation, we correlate Raman maps of the G’, G, and D bands found in graphene with spatial EBSD data. We find that graphene growth is sparse or inexistent on annealing twins and non-primary crystal facets such as Cu(362) and Cu(441). Additionally, the graphene is distorted along Cu grain boundaries and monolayer on the Cu(110) surface. Analysis of the G’ band full width at half-maximum (FWHM) along the mesa shows that graphene does not grow on the Cu(232) or Cu(100) twins. Overall, the mesa has FWHM values of 56.9 ± 26.2 cm-1, 32.1 ± 23.0 cm-1, and 40.6 ± 28.4 cm-1, for G’, G, and D bands, respectively, the first statistical metric for FWHM on the Cu/graphene system shown. AFM measurements along the different crystal surfaces show no dependence for the G’ FWHM, IG’/IG, or ID/IG on RMS roughness. While nucleation might be enhanced with a rough surface [3], the graphene growth mechanism appears to be crystallographically dominated, where dominant Cu facets such as Cu(110), Cu(100), and Cu(111) are necessary. Hence, to engineer high quality graphene films, one must control the polycrystalline Cu structure to preferred facets by performing techniques such as long Ar/H2 anneals and chemical mechanical polishing.[1] Li et al., Science 324, 1312 (2009).[2] Bhaviripudi et al., Nano Lett. 10, 4128 (2010). [3] Pehrsson et al., Thin Solid Films 212, 81 (1992).
9:00 PM - QQ9.17
Post Transfer Treatment Study of CVD-grown Graphene for Electronic Application.
Hossein Sojoudi 1 , Anuradha Bulusu 1 , Samuel Graham 1
1 Mechanical Engineering Department, Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractPost transfer treatment of CVD graphene to improve its electronic and optical properties has been explored through annealing and doping. While such methods have shown improvement in graphene quality and performance, there is still a need for a systematic study to understand the physics behind these processes. In this regard, we present a comprehensive study of heat treatment and doping effects on CVD- grown graphene on copper foils using Raman spectroscopy, XPS, UV and Visible Spectroscopy as well as Kelvin probe to measure changes in work function of graphene. Low temperature annealing was found to be essential to remove impurities while the annihilation of lattice defects was observed at higher temperatures. Raman spectroscopy measurements after vacuum annealing revealed an environmental doping effect due to exposure to air. We demonstrated that the annealing also resulted in changes in residual stresses in the graphene as well as a shift in the binding energy of C and O groups on the surface. Chemical doping using acid treatment and metal intercalation showed a strong effect on changing the work function of the graphene. Finally, the long term stability of the chemically doped samples was investigated and will be presented.
9:00 PM - QQ9.18
Partially Hydrogenated Graphene: Semiconductor Material with a Tunable Gap and Its Non-destructive Optical Characterization.
Anatoli Shkrebtii 1 2 , Phillip McNelles 1 , Jose Luis Cabellos 2 , Bernardo Mendoza 2 , Franco Gaspari 1
1 Science, University of Ontario Institute of Technology, Oshawa, Ontario, Canada, 2 , Centro de Investigaciones en Optica, León, Guanajuato, Mexico
Show AbstractSince 2004 we have witnessed a spectacular growth of a research on graphene [1]. Although graphene demonstrates a lot of exciting properties, its zero-gap band structure limits graphene application in 2D microelectronics. As was demonstrated recently [2], hydrogenation of graphene produces a stable free standing film, graphane. However, its 5 eV gap is insulator-like rather than semiconducting. To tailor the films’ gap we proposed controlled hydrogenation of graphene[3], while the experimental confirmation of such processed has been published very recently [4]. To investigate further possibility of electron gap tuning of graphene based materials we extensively modelled from first principles the structural, electronic and optical properties of partially hydrogenated graphene. Hydrogen passivated graphene interfaces with 75%, 50%, 25%, 12% and 6% monolayer coverage and numerous hydrogen induced superstructures have been considered within hexagonal and rectangular supercells (containing up to 32 carbon host atoms). Electron and optical LDA DFT gaps between 1.5 and 0.2 eV, suitable for microelectronic application, were obtained for low hydrogen coverage. For such systems, hydrogen clustering (by saturating neighbouring C dangling bonds at the opposite sides of at the graphene sheet) is energetically most favourable and generally produces larger gap. In addition, ordering of hydrogen was observed at 50% of H, that offers a possibility of transforming 2D graphene to an array of 1D nanowires. More homogeneous H distribution with opposite bonding to C-host atoms is, in contrast, less energetically favourable or even structurally unstable. Calculated optical linear and nonlinear optical responses indicate they are not only the gap sensitive, but can provide an access to microscopic details of the 2D nano-sheets’ such as symmetry, hydrogen induced structure and degree of hydrogenation, chemical bonding and many others. This includes linear optical response and its anisotropy, second harmonic generation (SHG), recently proposed coherent control of injection current, and optical spin injection. The above nonlinear optical response can be extracted by terahertz radiation emission. The approach developed can used for graphene/graphane single layer or bilayer, formed, e.g., on top of SiC (0001), Ir(111) or Ni(111) surfaces, promising structures for device application. In such systems, experimental geometries may not provide conditions for complete hydrogenation of the 2D sheet(s).[1] K. S. Novoselov, A. K. Geim, S. V. Morozov, et. al. Science 306, 666 (2004)[2] J. O. Sofo, A. S. Chaudhari, and G. D. Barber, Phys. Rev. B 75, 153401 (2007)[3] A. I. Shkrebtii, J. L. Cabellos, N. Arzate, B. S. Mendoza, and P. McNelles, International School of Solid State Physics Epioptics-11, Erice, Sicily, 19-25 July 2010[4] D. Haberer, D. V. Vyalikh, S. Taioli, et al, Nano Letters 10, 3360 (2010)
9:00 PM - QQ9.2
Selective Growth of Carbon Nanotubes on SiC Using An Amorphous Carbon Precursor Layer.
Betty Quinton 1 2 , Bang-Hong Tsao 3 , Jack Burke 3 , Jacob Lawson 3 , J. Merrett 2 , James Scofield 2 , Paul Barnes 2
1 Material Science Engineering, Wright State University, Dayton, Ohio, United States, 2 Propulsion Directorate, Air Force Research Lab, Dayton, Ohio, United States, 3 , University of Dayton Research Institute, Dayton, Ohio, United States
Show AbstractCarbon nanotubes (CNTs) exhibit excellent electrical and thermal properties. Silicon Carbide (SiC) is a leading material for high temperature electronic devices. By combining SiC and CNTs, a new, more robust power module configuration may be achieved. Unfortunately, growing CNTs on SiC is a difficult task due to the formation of silicates and carbides, which are known to poison the catalytic activity needed for nanotube growth. This study has shown that growth can be sustained, however, by depositing a thin precursor layer consisting of amorphous carbon on the surface of the SiC. Furthermore, selected CNT growth was demonstrated by patterning selected areas of a given SiC sample via standard photolithography techniques prior to tube growth. After CNT growth on the SiC sample, space between the CNTs was filled with Ni via a chemical treatment to improve adhesion to the SiC and to increase overall structural integrity. Cross sectional TEM analysis was conducted to monitor quality of the Ni/CNT, CNT/SiC and Ni/SiC interfaces. The processing procedures and the resulting findings will be presented.
9:00 PM - QQ9.21
Photo-electrical Effect of Pristine and Functionalized Graphene Grown by Chemical Vapor Deposition.
Jian Lin 1 2 , Jiebin Zhong 1 , Jennifer Reiber Kyle 2 , Miroslev Penchev 2 , Mihri Ozkan 2 , Cengiz Ozkan 1 3
1 Mechanical Engineering, UC-Riverside, Riverside, California, United States, 2 Electrical Engineering, UC-Riverside, Riverside, California, United States, 3 Material Science and Engineering, UC-Riverside, Riverside, California, United States
Show AbstractIn this talk we present the photo-electrical effect of pristine and nitric acid treated graphene field effect transistors made by chemical vapor deposition (CVD). The results of the decreased electrical conductance and shift of Dirac point arise from the molecular photodesorption from graphene. When post treated with nitric acid the photodesorption efficiency was decrease from 52% to 21%, which was proposed to be caused by the passivation of oxygen-bearing functionalities to CVD graphene structural defects. This result provides a new strategy of stabilizing the electrical performance of CVD graphene which is promising candidate as highly conductively photoelectrical material.
9:00 PM - QQ9.22
Effect of Applied Bias on the Raman Scattering of Chemical-vapor-deposition-grown Graphene on SiO2 Films.
Dong Hee Shin 1 , Sung Kim 1 , Dong Yeol Shin 1 , Jungkil Kim 1 , Suk-Ho Choi 1
1 Department of Applied Physics, Kyung Hee University, Yongin, Kyungkido, Korea (the Republic of)
Show Abstract100 nm SiO2 films were fabricated on Si wafers by ion beam sputtering, and subsequently heated at 1100oC for 20 min by rapid thermal annealing. Single-layer graphene (SG) and few-layer graphene (FG) were grown on copper foil and nickel film, respectively, by chemical vapor deposition and then transferred on SiO2 films. The graphene layers were characterized by optical microscopy and micro-Raman image mapping. For ohmic contacts, Al electrodes of 10 mm length and 0.5 mm separation were deposited on the graphene films by using a shadow mask in a thermal evaporator. Bias voltages (VA) were applied to study the influence of electric field on Raman spectra of the graphene films. Raman spectra in the visible range were measured by varying VA from -2 to 2 V in steps of 0.2 V under an 532 nm (2.33 eV) laser excitation. For FG, the Raman intensities of the D and G bands exhibited significant but different dependences on VA. As VA increased under positively biased, the G band intensity monotonically decreased, but the D band intensity monotonically increased. In contrast, both the D and G band intensities increased with increasing VA under negatively biased. As VA varied from 0 to 2 V, the D and G bands were red-shifted from 1333 to 1343 cm-1 and from 1569 to 1580 cm-1, respectively. As VA varied from 0 to -2 V, the D band was red-shifted from 1569 to 1576 cm-1, whilst the G band was almost fixed at about 1336 cm-1. These results are compared with those for SG and discussed based on possible physical mechanisms.
9:00 PM - QQ9.23
Temperature-dependent Resistivity of Graphene Rippled on Size-controlled Si-nanocrystal Layers.
Seung Bum Yang 1 , Sung Kim 1 , Jungkil Kim 1 , Suk-Ho Choi 1 , Hong Kyw Choi 2 , Sung-Yool Choi 2
1 Department of Applied Physics, Kyung Hee University, Yongin, Kyungkido, Korea (the Republic of), 2 , Electronics and Telecommunications Research Institute, Daejeon Korea (the Republic of)
Show AbstractSiOx/SiO2 multilayers were prepared on n-type Si (100) wafers by ion beam sputtering and annealed to form silicon nanocrystals (Si NCs). Subsequently, chemical-vapor-deposition-grown few-layer graphene films were transferred on the surface of the Si-NC layers. The size of Si NCs was shown to be distributed from ~ 1.5 to ~ 3.8 nm as x varied from 1.8 to 1.0, as analyzed by x-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy. The period and amplitude of the ripple in graphene films were controlled by varying the size of Si NCs. The resistivity was measured by using coplanar two-probe geometry with Al contacts of 10 mm length and 2 mm separation. In the temperature range from 80 to 400 K, the resistivity at a fixed bias of 1V showed a decreasing behavior as x varied from 1.0 to 1.4, but an increasing one as x varied from 1.4 to 1.8, consistent with the change of C1s core-level XPS peak intensity. In contrast, above 400 K, the resistivity showed a minimum at x = 1.6. The resistivity varied from 1.6 to 2.8 kΩ depending on x and temperature. The x-dependent changes of the resistivity and the XPS binding energy are thought to be related to those of electronic properties of graphene caused by the variation of its corrugation on the Si-NC layer. The temperature-dependent resistivity was well fitted based on the mechanism of thermionic carrier injection over Schottky barriers, thereby producing barrier heights from 16 to 30 meV in the range of x = 1.0 to 1.8.
9:00 PM - QQ9.24
Mechanical Properties of Graphene and Graphite Including Vacancies Estimated by Molecular Dynamics Simulations.
Akihiko Ito 1 2 , Shingo Okamoto 2
1 Composite Materials Research Laboratories, Toray Industries, Inc, Masaki-cho, Iyo-gun Japan, 2 Department of Mechanical Engineering, Ehime University, Matsuyama Japan
Show Abstract Engineers focus attention on excellent mechanical and electronic characteristics of carbon materials in recent years. Then they are looking forward to applications to structural sub-assemblies and nano-electro mechanical systems such as electrochemical electrodes and filed emission. Carbon materials have various properties due to types of bond and atomistic structures, for example, diamond, graphene, carbon nanotube, fullerene. In particular, graphene has rigidity and strength which are nearly equal to those of diamond, and novel electronic properties. Then researches on graphene and graphite which is composed of graphene layers have been recently increasing. Pei et al. have presented a comprehensive study of the mechanical properties of hydrogen functionalized graphene using molecular dynamics simulations. They found that hydrogenation has significant influence on mechanical properties. Tsai et al. have investigated elastic properties of graphite and compared calculated material properties of the graphite with other published predictions. Defects often affect mechanical and electronic properties of materials.Recently direct evidence for defects ( vacancy, dislocation) in graphene layers has been reported. It is important to clarify relations between atomistic structure of graphene or graphite and mechanical as well as electrical properties when producing carbon materials with high performance. We investigated the mechanical properties of graphene and graphite including clustered distributed vacancies under tensile loading by molecular dynamics (MD) simulation. In the MD simulation, two types of potentials were used: the second-generational REBO (reactive empirical bond-oder) potential for covalent bond and the Lennard-Jones potential for the interlayer interaction. We found that the tensile strength drastically decreases up to 56% or less of pristine graphene with increasing the size of vacancies, on the other hand, the Young's modulus hardly changes. We also found that the glide dislocation of the angle of 60° against tensile direction is generated near a vacancy in graphene including vacancies under zigzag tension, and then the slip deformation occurs, and afterwards, fracture occurs, while the slip deformation doesn't occur in pristine graphene. The tensile strength decreases with increasing of the size of clustered vacancy in general. However the tensile strength of the graphene including the clustered sextuple-vacancy increases as the vacancy disappears by the progress of slip deformation. It was found that the frequency of the slip deformation in graphite including double–vacancy is less than that in graphene including double–vacancy. Our results suggest that the shape of vacancies affects the strength of graphene and graphite.
9:00 PM - QQ9.25
Chemical and Electronic Structural Change in the Nitrogen Implanted and Annealed Diamond Nanorods/Nanoflakes Spherule: In-situ High Resolution XPS and VB Studies.
Swathi Iyer 1 , Paul Maguire 1
1 Electrical and Mechanical Engineering, NIBEC, University of Ulster, Belfast, Belfast, Norther Ireland, United Kingdom
Show AbstractDiamond related nanomaterials such as the diamond nanowires, NCD, UNCD etc have in recent years attracted renewed interest mainly due to very high electrical conductivity, which is reported to be induced by nitrogen during the growth or due to post growth (doping) processes. Reactive ion implantation is one of the many widely acclaimed methods to modify the surface regions of carbon materials. Nitrogen, which acts as a donor can enhance the field emission of the diamond material due to the formation of additional energy levels in the band gap and electrical conductivity channels and also creates changes in the electron affinity levels. Ion implantation or extrinsic atomic doping of elements provides an excellent path to tune and optimise the electronic properties of the carbon material Novel diamond nanorod flakes (DNR) structures synthesised by MPECVD were bombarded by low energy (5 keV) nitrogen ions for times between 0 to 20 minutes and subsequently annealed. The changes incurred to the bonding structure upon ion bombardment and thermal treatment was investigated by the in situ high resolution XPS. By controlled ion bombardment and annealing, specific amount of defects can be generated, enabling the system to transform from sp3 C to sp2 C and vice versa. The impact of N-bombardment on DNR structures and their thermal stability were investigated. The C1 component (sp2 C) was up shifted by 0.3 eV due to the N-bombardment defect generation. Increasing bombarding times enhanced the fraction of sp2 CN and sp2 C rather than sp3 C. Increased ID/IG ratio and decreased intensity of the trans-PA peaks after N-bombardments indicated incorporation of nitrogen (28 at. %) at the grain boundaries. At elevated temperatures (800 C), decrease in FWHM of the C 1s and increase in the sp2 C concentration indicates the structure to becoming more graphite like. The N 1s splits at higher temperature and this may be due to the re-arrangement of the N bonding states. At higher temperature the broken metastable bonds created by the ion bombardment may be converted to sp2 C, thereby enhancing the population of sp2 C and sp2 CN. The thermal energy drives the defects into the substitution sites in the grain boundaries and the carbon matrix. The complete disappearance of the ν1 and ν3 along with the decrease of ID/IG ratio, with annealing indicates a graphitic transformation. The changes in the electronic band structure after the thermal and N-bombardment is currently being investigated.
9:00 PM - QQ9.26
Mechanical Properties of Single Crystal Diamond Estimated by Molecular Dynamics Simulation with the Second-Generation REBO Potential.
Shingo Okamoto 1 , Akihiko Ito 2 1
1 Department of Mechanical Engineering, Ehime University, Matsyama Japan, 2 Composite Materials Research Laboratories, Toray Industries, Inc, Masaki-cho, Iyo-gun Japan
Show Abstract The carbon materials such as diamond, carbon nanotube, graphene or fullerene have complex atomic structures and the variable modes of covalent. It is important to use an appropriate potential function in order to express their physical properties in molecular dynamics (MD) simulations. The second-generational REBO potential has been mainly used on simulations of carbon nanotubes and graphilte which are composed of sp2 carbon atoms. The second-generational REBO potential may be also able to simulate basic physical properties of diamond which is composed of sp3 carbon atoms as well as its bond length, bond energy, vacancy formation energy and so on, more exactly than other potential functions. Then we investigated the effets of the tensile direction and periodic boundary condition (PBC) on the mechanical properties of single crystal diamond (SCD) under tensile loading by MD simulation with the second-generational REBO potential. At first we investigated the relation between the tensile direction and the mechanical properties for the SCD model applying the PBC to three-axial directions. The tensile strength increases in order of the [111]-direction < [110] < [100], and Young’s modulus increases in order of [100] < [110] < [111] when the Poisson's ratio is assumed to be constant under the NVT ensemble and the PBC is applied to all directions of X, Y, and Z. We found that each qualitative relation between the mechanical property such as tensile strength or Young's modulus and the tensile direction is agreement with the both calculated results by the first principle and the cleavage energy method although our calculated results on the tensile strength are larger than the ones by the first principle for all tensile directions. Next, we investigated the effects of the PBC to the tensile strength and Young's modulus. The analysis models are composed of the restraint areas at both ends for the tensile direction and the motion one that can move by the interactive force between atoms. The MD simulations were carried out by moving the restraint area in one side by the constant velocity. The tensile strength and Young’s modulus of the [100]-direction are smaller than those of [110] when the PBC is applied only to the Y-direction under the NVT ensemble. It was found that each qualitative relation between the mechanical property such as tensile strength or Young's modulus and the tensile directions is agreement with the MD’s result using Tersoff potential. In addition, we found that constriction is generated when stress reaches the maximum value in the [100]-direction. Our results on the tensile strength and Young’s modulus for the SCD were qualitatively in reasonable agreement with the published ones for the first principle and MD with the Tersoff potential. Our results indicate that the second-generational REBO potential is also useful for MD simulations on tension of diamond.
9:00 PM - QQ9.27
High Quality p-type {111} Homoepitaxial Diamond Thin Films Produced for Diamond Based Devices.
Andrada Lazea 1 , Tokuyuki Teraji 1 , Yiuri Garino 1 , Satoshi Koizumi 1
1 Sensor Materials Center, Optical Sensor Group, National Institute for Materials Science, Tsukuba 304-0044, Ibaraki, Japan
Show AbstractThe quality of our boron-doped diamond films, grown by Microwave Plasma activated Chemical Vapor Deposition (MPCVD) on high pressure high temperature synthetic type Ib {111}-oriented diamond substrates, is primarily estimated from Hall measurements and low-temperature cathodoluminescence (CL) analysis. The evolution of films properties, obtained in the low methane concentration of 0.05% CH4/H2 ratio, is completed by surface morphology and incorporation of impurities investigations. Hall mobility values exceeding 550 cm2 V-1 s-1 at room temperature and CL excitonic peaks similar to p-type natural and synthetic CVD diamonds were achieved. In addition, a correlation between the particularities of our growth procedure and the improvement in opto-electrical properties is discussed.
9:00 PM - QQ9.28
Study of UV Photoresponse of Micro- and Nano-crystalline Carbon Structure Thin Films.
Frank Mendoza 1 2 , Vladimir Makarov 1 2 , Gerardo Morell 1 2
1 Physics, University of Puerto Rico, San Juan, Puerto Rico, United States, 2 Institute for Functional Nanomaterials, University of Puerto Rico San Juan, PR, USA., University of Puerto Rico, San juan, Puerto Rico, United States
Show AbstractThe room-temperature photosensitivity of micro- (MCD), submicro- (SMCD) and nano- (NCD) crystalline carbon structure thin films synthesized by hot-filament chemical vapor deposition was studied. The structure and composition of these diamond materials were characterized by Raman spectroscopy, scanning electron microscopy and X-ray diffraction. The UV sensitivity and time response was estimated for the various types of diamond materials and was studied using a steady state broad UV excitation source and two pulsed UV lasers. In our study, we demonstrate that they have high sensitivity in the UV region as high as 109sec-1mV-1 range, linear response in a broad intensity range below 320 nm and photocurrents around 10-4 - 10-5 A, short time response better than 100 ns, which is independent of fluency intensity.
9:00 PM - QQ9.3
Fabrication and Characterization of Structural and Electrical Properties of Ultrananocrystalline Diamond Nanowires.
Xinpeng Wang 1 2 3 , Anirudha Sumant 1 , Vishwanath Joshi 1 , Leo Ocola 1 , Bernd Kabius 4 , Daniel Lopez 1
1 Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois, United States, 2 Department of Physics, University of Puerto Rico, San Juan United States, 3 Institute for Functional Nanomaterials, University of Puerto Rico, San Juan United States, 4 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States
Show AbstractCurrently, there is tremendous interest in fabricating diamond nanowires (NWs) due to their extraordinary mechanical, electrical, and optical properties as predicated by theory for quasi 1-dimensional sp3 nanostructures. Synthesizing or fabricating these nanostructures is proving to be very challenging. To date, only a few attempts have been reported, either by etching single crystal diamond lithographically to produce diamond NRs or by coating Si nanowires with nanocrystalline diamond to produce diamond NWs. We report an approach based on e-beam lithography and reactive ion etching of ultrananocrystalline diamond (UNCD), to produce UNCD NWs with nanowire width in the range of 20-150 nm, and thickness of 80-100 nm with well-defined position and nanometer scale precision. We have fabricated nitrogen-doped UNCD NWs and characterized them using UV and visible Raman spectroscopy and transmission electron microscopy (TEM). Metal contacts (Au/Ti) were fabricated onto UNCD NWs by optical lithography and lift-off for electrical measurements. We will discuss preliminary structural studies of UNCD NWs and measurements of their electrical properties. The ability to fabricate UNCD NWs provides an opportunity to study the fundamental mechanism of transport processes in NWs, which will enable new ideas and possibilities for the fabrication of nanoelectronic devices and sensors with increased sensitivity and new functionalities for a variety of applications.
9:00 PM - QQ9.30
Modulation of Thermoelectric Transport Properties in Fermi Level Shifted Carbon Nanotube Films by Precipitating Nanoparticles on Nanotubes.
Yeontack Ryu 1 , Choongho Yu 1
1 Mechanical Engineering, Texas A&M University, College Station, Texas, United States
Show AbstractIn one dimensional structure, the Fermi level of carbon nanotube could be shifted to n type or p type direction by decorating metal nanoparticles or doping molecules, which indicates that the work function in the nanotube may increase or decrease depending on that of incorporating elements. It is expected that thermoelectric transport properties such as electrical conductivity and Seebeck coefficient can be modulated and optimized through the Fermi level shift. In this work, we sprayed the single walled and double walled carbon nanotube solutions, which are dispersed in water with an aid of SDBS (sodium benzenesulfonate) surfactant, on glass substrates in order to obtain thin films. Several metal nanoparticles such as Au, Cu, Ni, Fe, and La having different work functions were decorated on the surface of nanotubes by spontaneous reduction or a galvanic displacement. Carbon nanotube types or reduction potential differences between metal ions and electrode materials played an important role in controlling the Fermi level so as to find the optimal thermoelectric transport properties. We believe that this electron transport study enables us use decorated carbon nanotubes in thermoelectric application of carbon nanotubes.
9:00 PM - QQ9.31
Putting the Squeeze on Thermal Expansion in Polymer Films Using Carbon Nanotube Belts.
Alan Dalton 1 , Patnarin Worajittiphon 1 , Izabela Jurewicz 1 , Joseph Keddie 1 , Alice King 1
1 Physics, University of Surrey, Guildford United Kingdom
Show AbstractDrawing on our previous findings,[1] we have created ordered monolayers of monodispersed colloidal particles containing honeycomb-like networks of CNTs. In our previous work, we have shown that in 3-dimensions, such precise assembly of CNTs is facilitated by tuning the interface between the polymer and the CNTs using a non-ionic surfactant. The incorporation of CNT in a colloidal polymer film results in the formation of belt-like support equatorially surrounding each particle. The belt inhibits particle sintering upon heating. The mismatch in the polymer thermal expansion relative to that of the nanotube network hinders expansion in the plane of the film and as a result forces an increased expansion in the out-of-plane direction. As the material is heated above its Tg, colloidal particles expand and are squeezed out in the out-of-plane direction (“squeezing effect”) because of their in-plane confinement. We believe that this is the first time that the “squeezing effect” has been reported at the nano-scale. The maximum enhancement of thermal expansion of 200% is achieved when the percolating CNTs network is formed. Such strong enhancement of expansion perpendicular to the plane of the film could ultimately be utilized for a range of applications including the manufacturing of nanoscale sensors, switches and actuators. Moreover, the ability to thermally manipulate the surface contour at the nanoscale may have important implications in tissue engineering for manipulating cell adhesion, growth and movement as well as offering a potentially facile method to perform hydrophobic/hydrophilic surface switching. [1] I. Jurewicz et al. Macromol. Rapid Commun. 2010, 31, 609. [2] P. Worajittiphon et al. Adv. Mat. 2010 n/a. doi: 10.1002/adma.201003145
9:00 PM - QQ9.34
Improving the Wettability of Aluminum on Carbon Nanotubes.
Kang Pyo So 1 , Il Ha Lee 1 , Dinh Loc Duong 1 , Tae Hyung Kim 1 , Seong Chu Lim 1 , Kay Hyeok An 2 , Young Hee Lee 1
1 department of nanotechnology and science, Sungkyunkwan univ., Suwon Korea (the Republic of), 2 R&D Department, , Chonju Machinery Research Center, Chonju Korea (the Republic of)
Show AbstractThe wetting of a metal on carbon nanotubes is fundamentally difficult due to the unusual large difference of their surface tensions and is a bottleneck for making metal-carbon nanotube (CNT) composites. Here, we report a simple method to enhance the wettability of metal particles on the CNT surface by applying aluminum, which is the largest surface tension material. This method involves two steps: i) Al nanoparticles are decorated on multiwalled carbon nanotubes by electroplating and ii) Al powder is further spread on Al-electroplated CNTs, followed by high temperature annealing to accommodate complete wetting of the aluminum. The large surface tension difference is overcome by forming strong Al-C covalent bonds initiated by defects of the CNTs. The decrease of the D-band intensity, the G-band shift in the Raman spectroscopy, and the formation of Al-C covalent bonds, as confirmed by x-ray photoelectron spectroscopy, were in agreement with our structural model of CNT-vacancy-O-Al determined by density functional calculations.
9:00 PM - QQ9.35
Modification of the Outer Surface of Carbon Encapsulated Nanoparticles by Noble Metals.
Boris Bokhonov 1
1 , Institute of Solid State Chemistry, Siberian Branch, Russian Academy of Sciences, Novosibirsk Russian Federation
Show AbstractNew carbon nanomaterials of different morphologies (nanotubes, fullerenes, graphene) are among the most popular nano-objects under intense investigation over the last few decades. However, the investigation of both the physical and chemical properties of already known carbon nanostructures, such as metal core–carbon shell, may also turn out to be useful. This allows the mechanisms of reactions that occur during chemical transformations of composite carbon nanomaterials to be established as well as enables new applications to be found, or even improve the current characteristics for use in various areas. In this work we propose a new method for deposition of noble metal nanoparticles (Au, Ag, Pt and Pd) on the surface of the carbon shells of encapsulated metal (Ag, Ni, Fe, Cu, Bi) particles. Low pressure dc arc discharge was used to produce the carbon-encapsulated metal samples. The deposited materials consisted of spherical amorphous carbon-coated metal nanoparticles. The deposition of the noble metal nanoparticles (platinum, gold, silver) was performed using the galvanic replacement reaction. Electron microscope studies showed that for the short time of treatment with HAuCl4, H2PtCl6, H2PdCl6 or AgNO3 solutions, respectively, the metallic gold, platinum, palladium and silver nanoparticles, several nanometers in diameter, are deposited on the outer surface of the carbon shells of the encapsulated metal particles. With increasing treatment time, increasing numbers of noble metal nanoparticles on the surface of the carbon shells, and almost complete dissolution of the metal core, were observed. Relying on the known properties of the nanoparticles of this composition and morphology, we may assume that the obtained nanomaterials will turn out to be quite promising for applications such as catalysis and medicine.
9:00 PM - QQ9.38
Solvent-free Functionalization of Carbon Nanomaterials with Aliphatic Amines.
Juan Juan Rizo 1 , Victor Meza-Laguna 2 , , Flavio F. Contreras-Torres 1 , Elena Basiuk 1
1 Centro de Ciencias Aplicadas y Desarrollo Tecnologico, Universidad Nacional Autonoma de Mexico , Mexico Mexico, 2 Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico , Mexico Mexico
Show AbstractCarbon nanomaterials such as fullerene (C60), single-walled carbon nanotubes (SWNTs) and nanodiamond (ND) have gained much attention due to their unique properties and broad applications in such diverse areas as physics, chemistry, materials science, nanomedicine, etc. The chemical (in particular covalent) functionalization of carbon nanomaterials is considered as a crucial step toward their biomedical applications, where SWNTs and ND are intended to be used as a delivery vehicle for cancer cure. While the covalent functionalization of C60 and SWNTs is well documented in the literature, nanodiamond is a relatively new object in this regard. In the present study, we employed an ecologically friendly technique of solvent-free functionalization for the three carbon nanomaterials (that is, C60, SWNTs and ND) with four different aliphatic amines. The gas-phase functionalization for volatile (at elevated temperatures) 1,8-diamineoctane (DO) and octadecylamine (ODA), and direct heating in the melt for the polymeric polyethylene glycol diamine (PEGDA) and polyethylenimine (PEI) were used. The functionalized nanomateriales were characterized by using infrared and Raman spectroscopy, as well as thermogravimetric analysis. The morphology of the nanostructures obtained was characterized by atomic force microscopy. We found that both solvent-free methods were efficient in the nanomaterial functionalization. The possibility of development of functional devices such as specific biosensors and membranes through the chemical modification of carbon nanomaterials by amines is discussed.Acknowledgments: Financial support from the Institute of Science and Technology of the Federal District Government (grant ICYTDF 333/2009) is greatly appreciated.
9:00 PM - QQ9.4
Effect of Interlayer/Multilayer (TiAlN, TiCN, and TiN) on the Growth of Diamond Thin Films on WC Substrates.
Maneesh Chandran 1 , Chakravarthy G.v 2 , Kamaraj Muthusamy 2 , Mamidanna Rao 1
1 Physics, Indian Institute of Technology Madras, Chennai, TN, India, 2 Metallurgical Engineering, Indian Institute of Technology Madras, Chennai, TN, India
Show AbstractDiamond coated tungsten carbide (WC-Co) substrates are intensively used in industries for various applications. However, one of the continuing challenges associated with the diamond coatings on WC-Co substrates is the lack of proper adhesion between the substrate and the film, which results in a lesser life time for the diamond coated tools than the expected. An interlayer coating between the diamond film and the WC substrate can be a better approach to reduce this deleterious effect. Several interlayers have been proposed by different authors [1,2]. However a systematic comparison on the effect of interlayer/multilayer on the growth of diamond films on WC substrates has not been extensively studied. Here in, we report on diamond coatings on WC-Co substrates using hot filament CVD (HFCVD) system. The deposition was carried out with two different interlayer (TiCN and TiAlN) and a multilayer (TiN/Al2O3/TiCN) between the substrate and the thin film. Both the interlayers (TiAlN and TiCN) were deposited on to the WC-Co substrates using physical vapor deposition (PVD) technique and the multilayer (TiN/Al2O3/TiCN) were deposited using CVD technique [3]. The substrates were ultrasonically cleaned with ethanol and were seeded with diamond nano particles, dispersed in dimethyl sulfoxide (DMSO), using an ultrasonic cleaner for 10 min and placed inside the CVD chamber. The precursor gases used, were methane (60 sccm) and hydrogen (3000 sccm ). The set chamber pressure (10 Torr, 30 Torr and 50 Torr) was varied in order to vary the grain size from nanocrytalline diamond (NCD) to microcrystalline diamond (MCD). The tungsten (W) filament temperature was ~2200 °C and the substrate temperature was ~800 °C. The whole growth process was performed for three different time durations, viz, 1 h, 4 h and 6 h, for which the thickness was found to be ~1 µm, 3 µm, and 5 µm respectively. For comparison, we carried out diamond deposition on WC-Co substrate without any interlayer. Phase analysis of the diamond films on TiAlN and TiCN interlayer and multilayer (TiN/Al2O3/TiCN) were investigated by XRD with Cu Kα radiation, showed (111) orientation at 44° and (220) at 75°. The microstructure of the diamond film was observed using FESEM, showed dense packaged pinhole-free microstructure. The Raman spectra of the deposited films showed a sharp peak at ~1332 cm-1, that corresponds to active phonon mode of diamond. Diamond deposition on virgin WC substrates without any interlayer showed the formation of diamond like carbon (DLC), which contains both sp2 and sp3 hybridization. The sp2 hybridization was catalytically nucleated due to the presence of cobalt from the WC substrate. This results concludes that use of interlayer/multilayer was useful in suppressing the carbon-cobalt interaction. A systematic study on the effect of interlayer and multilayer coating on the structural, surface and mechanical properties of diamond films will be presented and discussed in detail.
9:00 PM - QQ9.40
Modification of sp2 Hybridized Carbon Materials With DNA Strands and Their Electrical Characterization.
Rob Vansweevelt 1 , Annick Vanhulsel 2 , Vincent Mortet 1 , Anitha Ethirajan 1 , Luc Michiels 3 , Chris Van Haesendonck 4 , Patrick Wagner 1
1 Insititute for Materials Research, Hasselt University, Diepenbeek Belgium, 2 VITO Materials, Flemish Institute for Technological Research, Mol Belgium, 3 Biomedical Research Institute, Hasselt University, Diepenbeek Belgium, 4 Laboratory of Solid-State Physics and Magnetism, Katholieke Universiteit Leuven, Leuven Belgium
Show AbstractThe relatively new and exciting thin forms of sp2 hybridized carbon are materials of great interest in the development of biosensors. They have a high surface to volume ratio and very interesting electrical properties. In order to investigate their potential as a biosensor platform they are functionalized with DNA strands and electrical transport measurements are performed. Carbon nanowalls (CNW) are a first type of material that is functionalized with DNA. CNW are a network of walls oriented perpendicular to their substrate, with each wall consisting of 4 – 6 stacked graphene layers. The edges of these walls are covalently bound with DNA strands through the photochemical attachment of a fatty acid linker molecule, followed by an EDC-mediated reaction to bind amino-labeled DNA. After attachment of the probe DNA strand, hybridization experiments with fully complementary and single mismatched target DNA strands are done. The second type of material that is used are ultrathin graphite flakes. Electrical transport measurements are done on these materials. They show a giant positive magnetoresistance effect and an anomalous Hall effect. Furthermore, efforts are taken to functionalize the basal plane of these ultrathin graphite flakes with DNA strands. A covalent way and a non-covalent way are investigated.The authors acknowledge financial support by FWO Flanders in the framework of the project “Structural and electronic properties of biologically modified graphene-based layers”.
9:00 PM - QQ9.41
Phage Displayed Peptides Binding to Graphene, Graphite, and Carbon Nanotubes.
Steve Kim 1 , Kuang Zhifeng 1 , Joseph Slocik 1 , Sharon Jones 1 , Laurie Wissler 1 , Yue Cui 2 , Barry Farmer 1 , Michael McAlpine 2 , Rajesh Naik 1
1 , Air Force Research Labs, Wpafb, Ohio, United States, 2 4.Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey, United States
Show AbstractThe development of a general functionalization platform for carbon nanomaterials and their device platforms could stimulate exciting scientific and technological opportunities. Oligopeptides are robust molecules for the selective recognition of a variety of chemical and biological materials. Phage display is a powerful method for identifying peptides that possess enhanced selectivity and binding affinity toward a variety of targets. Here we explore the binding properties of the phage displayed peptides to graphene, graphite, and carbon nanotube surfaces in the form of pristine micro patterns and devices. Our approach is based on a unique combination of comprehensive phage displayed peptide screening processes, along with novel patterning techniques, device fabrications, and computations. These results, combined with the large variety of novel materials for self-assembly and target analytes for sensing, could open up opportunities for applications in computing, sensing, hydrogen storage, and energy storage, etc.
9:00 PM - QQ9.42
Self-assembly of Meso-tetraphenylporphines on Graphite and Single-walled Carbon Nanotubes, as Studied by Scanning Tunnelling Microscopy and Molecular Mechanics.
Maria Bassiouk 1 , Edgar Alvarez-Zauco 2 , Vladimir Basiuk 1
1 Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Mexico-City, D. F. , Mexico, 2 Facultad de Ciencias, Universidad Nacional Autonoma de Mexico, Mexico-City, D. F. , Mexico
Show AbstractThe self-assembly of porphyrins on solid supports into highly organized functional arrays is an area of increasing research effort, offering numerous potential applications in the “bottom-up” approach to nanofabrication. Highly-oriented pyrolytic graphite (HOPG) is one of the most popular substrates to work with under ambient conditions, because it is electrically conductive, atomically flat, relatively inert and easy to clean; besides that, its structure is convenient to establish non-covalent interactions with the porphyrin molecules. The interest in non-covalent interactions of porphyrins with carbon nanotubes (CNTs) originates from the possibility of using nanotubes as another support for self-assemblies, as well as employing the CNT functionalization to improve their solubility and biocompatibility for biomedical applications. While detailed microscopic images of well-formed porphyrin assemblies on HOPG were reported by several research groups, there is an evident lack of information about the mechanisms explaining initial and intermediate steps in their formation. Furthermore, almost no information is available on the self-assemblies of porphyrin molecules on CNTs. Altogether, the above circumstances serve as good motives to appeal to theoretical tools combined with microscopic techniques in order to gain an insight. The goal of our work was to study the initial steps of self-assembly of meso-tetraphenylporphine ligand (H2TPP) and its cobalt(II) and nickel(II) complexes (CoTPP and NiTPP, respectively) on the surfaces of HOPG and single-walled CNTs (SWNTs). We performed molecular mechanics modeling (using MM+ force field) and scanning tunnelling microscopy (STM) imaging. Molecular modeling predicted a thermodynamic preference of H2TPP molecules to adsorb in monolayers on HOPG surface and nanotube sidewall, rather than their stacking or separation. On HOPG, the most favorable assemblies were predicted to be ribbons composed of interacting parallel chains of porphyrin units. On SWNT sidewalls, the thermodynamic preference pointed toward the formation of parallel and interacting long-period helices, giving rise to an almost full coverage of the nanotube surface. These preferable arrays on both types of carbon surfaces ensure the interaction of every porphyrin unit with as many neighbors as possible, in this way decreasing the potential energy of adsorption complexes. STM images obtained matched well the molecular modeling predictions. In particular, the formation of self-assembled porphyrin ribbons was a commonly observed phenomenon on HOPG; a preferential adsorption of porphyrin molecules near topographic defects of HOPG was found as well. On the nanotubes, a full coverage of the exposed portion of the sidewalls was observed, suggesting the formation of interacting long-period porphyrin helices.
9:00 PM - QQ9.44
A Critical Investigation of Defect Site Functionalization on Single Walled Carbon Nanotubes.
Elisa Del Canto 1 , Kevin Flavin 1 , Dania Movia 1 , Silvia Giordani 1
1 Chemistry / CRANN, Trinity College Dublin, Dublin Ireland
Show AbstractThe presence of carboxylated carbonaceous material in nitric acid treated single-walled carbon nanotube (SWNT) samples has recently brought renewed focus on the processes by which covalent functionalization of such materials are carried out. Using a widely reported 2-step purification/oxidation procedure, we have investigated the effect of basic treatment and solvent washing on the functionalization and final properties and behavior of SWNTs. We have demonstrated, using FT-IR, Raman and NIR-PL spectroscopies, that in the absence of NaOH treatment, COOH functionality is introduced directly onto SWNTs, and not only onto carbonaceous material present in the sample. Covalent functionalization of the oxidized materials was also investigated by attachment of a fluorescent probe, and ultimately, whether treated with base or solvent washed, the resulting materials are close to identical with respect to both their appearance and properties. In addition, we have demonstrated that using either of these purification/oxidation strategies, functionalized materials can be produced that still exhibit distinctive optical/electronic properties, as demonstrated by sustained structured spectroscopic absorption and emission features.
9:00 PM - QQ9.45
Investigation of the Chemical Bonds Between the Functionalized CNT and Metals.
Mina Park 1 , Byung-Hyun Kim 1 , Kwang-Ryeol Lee 1
1 , Korea Institution of Science and Technology, Seoul Korea (the Republic of)
Show AbstractIn the present work, we design the various hybrid structures of the single wall CNT and several metals such as copper, gold and aluminum complexes to understand and control the interactions between CNTs and metals in a systematic manner. The chemical interaction between functionalized defective CNT surfaces and metals is theoretically investigated using the first principle calculations based on the density functional theory method. Introduction of CNTs into a metal matrix has been considered to improve the mechanical properties of the metal matrix. However, the binding energy between metals and pristine CNTs wall is known to be so small that the interfacial slip between CNTs and the matrix occurs at a relatively low external stress. The enhancement of the interfacial strength between CNT and metal matrix is thus one of the key factors for successful development of the CNT/metal composites. Therefore, defective or functionalized CNT has been considered to enhance the interfacial strength of nanocomposites. We considered the various surface functional groups combined with topological defects, such as –O, –OH, –COOH, –N and –NO interacting with metals. We found that the oxygen of the surface functional group can enhance the interaction between the carbon and metals. The oxygen of the functional group could either promote electron exchange between metals and carbon atoms, thus, played a key role of a glue between the metals and the CNT surfaces. Among the oxygen-containing functional groups, the carboxyl group was the most optimized molecule with respect to the consistency of the binding energy enhancement of metals. These results strongly support the recent experimental work which suggested the oxygen on the interface playing an important role in the excellent mechanical properties of the CNT-reinforced Cu composite [1]. Meanwhile, the role of nitrogen of the functional groups is complicated and depends on the interacting metal elements. [1] Kim, K.T.; Cha, S.I.; Gremming, T.; Eckert, J.; Hong, S.H. Small 2008, 4(11), 1936.
9:00 PM - QQ9.47
The Diamond-solution Interface: The Surface Energy of Hydrogen Terminated Nanocrystalline CVD Diamond Derived from Contact Angle Measurements.
Stoffel Janssens 1 , Sien Drijkoningen 1 , Marc Saitner 1 , Hans-Gert Boyen 1 , Patrick Wagner 1 2 , Ken Haenen 1 2
1 , Institute for Materials Research, Diepenbeek, Limburg, Belgium, 2 Division IMOMEC, IMEC, Diepenbeek, Limburg, Belgium
Show AbstractNanocrystalline diamond (NCD) is a versatile material that is currently being put forward as a material of choice for a variety of applications that make use of its surface properties. In this work a determination of the surface energy (γ) for hydrogen terminated NCD (NCD:H) grown with microwave plasma enhanced chemical vapour deposition in an ASTeX reactor (AX6500) is presented. Five identical NCD:H samples of ~ 150 nm thickness were deposited on silicon substrates and examined with XPS to determine the surface groups and possible surface contaminations. In order to evaluate the surface energy, contact angle measurements were performed using the sessile drop method in combination with data analysis based on the 'OWRK' method [1-2]. Four possible ways to evaluate the surface energy (γ) of NCD:H are discussed:A.multiple water/alcohol solutions → calibrated with a variety of polymers(γ = 15 ± 3 mN/m);B.multiple water/alcohol solutions → calibrated with a variety of calibrated polymers(γ = 17 ± 6 mN/m);C.multiple water/alcohol solutions → values used from the article of Hong and Chen [3](γ = 28 ± 13 mN/m);D.water, ethylene glycol and diiodomethane(γ = 34 ± 5 mN/m).The latter method is the standard way to determine surface energies and this method leads to no significant polar interactions on the surface after data analysis, which is expected from NCD:H. However, the first three methods do show polar interactions on the surface to a certain extent. A possible explanation for this phenomenon is the presence of a higher adhesion force between alcohol and the NCD:H surface than between water and the NCD:H film. This would mean that these three methods lead to erroneous data because of the presence of a thin layer of alcohol on NCD:H, effectively leading to a water on alcohol system instead of the envisaged water/alcohol mixture on an NCD:H surface. Therefore, the use of water, ethylene glycol and diiodomethane to determine the surface energy of NCD:H seems to be the most reliable method. [1] D. Owens and R. Wendt, Jounal of Applied Polymer Science 13/8, 1741, 1969.[2] D. Kaelble, Journal of adhesion 2 (1970), 66.[3] L.-Y. Chen, F. Chau-Nan Hong, Diamond Relat. Mater. 12 (2003), 968–973.
9:00 PM - QQ9.48
Enhanced Neural Differentiation of Stem Cells on Carbon Nanomaterials.
Sung Young Park 1 , Jaesung Park 2 , Sung Hyun Sim 3 , Taekyeong Kim 4 , Kwang S. Kim 2 , Byung Hee Hong 3 , Seunghun Hong 1 4 5
1 Interdisciplinary Program in Nano-Science and Technology, Seoul National University, Seoul Korea (the Republic of), 2 Dept. of Chemistry, Pohang University of Science and Technology, Pohang Korea (the Republic of), 3 Dept. of Chemistry, Sungkyunkwan University, Suwon Korea (the Republic of), 4 Dept. of Physics and Astronomy, Seoul National University, Seoul Korea (the Republic of), 5 Dept. of Biophysics and Chemical Biology, Seoul National University, Seoul Korea (the Republic of)
Show AbstractIn strategies using stem cells (SCs) for brain repair and neural regeneration, it is important to develop an optimal scaffold which can promote cell adhesion, proliferation and differentiation for a long-time period. Carbon nanomaterials have attracted much interest for novel nanostructured scaffolds. However, their biological explorations for neural differentiation still need to be discovered. Herein, we report the enhanced neuronal differentiation of SCs on carbon nanomaterial-based substrates during long-term differentiation process. Our findings suggest that carbon nanomaterial-based substrate can be one of ideal extracellular scaffolds, which should open up various opportunities in stem cell research and regenerative medicine.
9:00 PM - QQ9.49
Flow Injection Microfluidic Device with Integrated Electrochemical Biosensor using Functionalized 3D Carbon Microstructures.
Varun Penmatsa 1 , Hiroshi Kawarada 2 , Chunlei Wang 1
1 MME, Florida International University, Miami, Florida, United States, 2 School of Science and Engineering, Waseda University, Tokyo Japan
Show AbstractPoint-of-care (POC) diagnostic devices capable of rapid detection with good specificity facilitate the early diagnosis of the diseases. The future of the POC devices depends on the effective miniaturization of laboratory procedures onto a single microchip. In this pursuit, microfluidic devices integrated with electrochemical biosensors play a significant role in the transition towards POC diagnostic devices because of low sample consumption and high sample throughput. In this work, we have fabricated a flow injection microfluidic device with functionalized 3-dimensional (3D) carbon microelectrodes for the detection of cholesterol. The high surface area 3-D carbon microstructures were fabricated by C-MEMS technique in which high aspect ratio patterned photoresist microstructures are pyrolyzed to carbon under inert atmosphere. The carbon surface was biofunctionalized by direct amination to form surface amino groups. The cholesterol oxidase was then covalently immobilized on the functionalized carbon surface by amide binding via NHS and EDC. The sensitivity and response time of the fabricated cholesterol sensor was tested for the typical cholesterol range in the human body. In addition, interference of glucose, ascorbic acid, and uric acid were also studied. The proposed system is promising as portable diagnostic device for cholesterol with real-time detection capability and good stability.
9:00 PM - QQ9.5
Transversal Cutting of Platelet Carbon Nanofibers to Form Uniform Graphene Discs.
Seong-Ho Yoon 1 , Donghui Long 1 , Jin Miyawaki 1 , Wei Li 1 , Isao Mochida 1
1 Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka Japan
Show AbstractGraphene is currently the most promising material in the realm of condensed-matter physics and nanoscience. The common source of graphene is high-quality graphite crystals. However, their irregular geomorphology makes it very difficult to produce graphene sheets with defined shape. In this work, we employed a new starting material, platelet carbon nanofibers, to isolate the graphene layers with defined disc shapes. A simple solution-based oxidative method has been used for transversal cutting of platelet carbon nanofibers. The diameter of discs is in accordance with the diameter of the parent PCNF, which can be controlled by catalyst size and temperature during the PCNF growth process. The thickness of graphenes discs are about 0.7-3 nm, which is strongly depended on the oxidative conditions. We have also developed a hydrothermal reduction method to split the oxidized graphene into very uniform graphene quantum dots. That is, to the best of my knowledge, the first report that using platelet carbon nanofibers to produce defined disc-shape graphene sheets and graphene quantum dots. These graphene layers with defined shape and graphene dots should significantly facilitate the application of graphene in a wide range of areas.
9:00 PM - QQ9.50
Carbon-nanoelectronic Field Effect Transistor Based High Frequency Biosensors.
Girish Kulkarni 1 , Zhaohui Zhong 1
1 Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan, United States
Show AbstractThe unique electronic properties of carbon based materials i.e. carbon nanotubes and graphene, enhances their interaction with the immediate environment. The sensitivity of transistor based biosensors however, suffers from the electrostatic screening due to mobile ions in solution. Here, we use carbon-nanoelectronic field effect transistor based high frequency biosensors for detection in high ionic strength solutions. The transistors are configured as high frequency mixers and the change in mixing current provides the sensing mechanism. At high frequencies, the ions are unable to follow the AC field and hence, electrostatic screening is minimized. In addition, the high transconductance of the transistor provides intrinsic gain for high frequency sensing. To prove this concept we demonstrate protein detection in ~100mM buffer solution with high sensitivity. The technique will be evaluated against both, low frequency transistor based biosensors and conventional dielectric sensing technique relying on impedance measurement. The result will lead to novel biosensors for point-of-care applications, where electronic sensors functioning directly in physiologically relevant condition are required.
9:00 PM - QQ9.51
Charge-transfer Doped Diamond Electrodes for Electrochemical Sensor Applications.
WaiLeong Chen 1 , Chiuan-Yi Li 2 , Shin-Hung Yei 1 , Shoupu Yeh 2 , Yonhua Tzeng 1 2
1 National Cheng Kung University Electrical Engineering and Computer Science, Microelectronic Engineering, Tainan Taiwan, 2 National Cheng Kung University , Institute of Nanotechnology and Microsystems Engineering, Tainan Taiwan
Show Abstract Diamond has high hardness, thermal conductivity, and chemical inertness, etc. It can be doped with boron and nitrogen to become a p-type and n-type semiconductor, respectively. When an undoped diamond surface is terminated with atomic hydrogen, it can exhibit negative electron affinity. When an electro-negative adlayer such as lightly acidic water in the atmosphere is adsorbed on top of a diamond surface which is terminated with atomic hydrogen and exhibiting negative electron affinity, valence electrons tunnel from the first few atomic layers of diamond surface to water adlayer. This charge transfer process results in p-type semiconductor surface of hydrogen-terminated diamond. Hydrogenation of diamond grains in polycrystalline film improves its electrical conductivity. The combined chemical inertness, biocompatibility, and electrical conductivity makes charge-transfer doped intrinsic diamond a good candidate for biochemical sensors applications. When compared to platinum electrodes, diamond electrodes have much lower background noise and a higher electrochemical potential window, which allows the detection of special compounds requiring electrochemical potentials exceeding the water splitting potentials for traditional electrodes such as platinum. Diamond films have been fabricated using DC- PECVD and Microwave Plasma Enhanced Chemical Vapor Deposition (MW-PECVD) in a gas mixture of methane diluted by hydrogen. Electrochemical characteristics of hydrogen-terminated diamond films, those after being exposed an air plasma for depleting surface hydrogen, and those re-hydrogenated diamond films will be reported based on examination by cyclic voltammetry in 0.1M H2S04 aqueous solution and [Fe(CN)]6-3/-4 aqueous solution with different scan rates (10mV/s, 20mV/s, 50mV/s, 100mV/s, 200mV/s). High current density and wide potential window have been observed in hydrogen-terminated diamond grown on silicon substrate. The surface morphology has been observed by SEM and atomic force microscopy (AFM); while the crystalline characteristics of diamond was examined by Raman spectroscopy.
9:00 PM - QQ9.52
Immunosensing Based on Patterned B-doped NCD Electrodes.
Lars Grieten 1 , Stoffel Janssens 1 , Natalie Vanden Bon 2 , Veronique Vermeeren 2 , Ward De Ceuninck 1 3 , Marcel Ameloot 2 , Ken Haenen 1 3 , Luc Michiels 2 , Patrick Wagner 1 3
1 Institute for Materials Research (IMO), Hasselt University, Diepenbeek, Limburg, Belgium, 2 Biomedical Research Institute, Hasselt University, Diepenbeek, Limburg, Belgium, 3 Division IMOMEC, IMEC, Diepenbeek, Limburg, Belgium
Show AbstractTo facilitate integration of diamond-based biosensors with established read-out strategies, patterned B-doped nanocrystalline diamond (B-NCD) electrodes were fabricated to be used in combination with electrochemical impedance spectroscopy. Thin (~100 nm) B-NCD films were grown on fused 1x1 cm silica substrates, followed by a patterning step to form four identical electrodes. After the deposition of a metal mask and an exposure of the complete configuration to an oxygen plasma for 2 minutes, four identical, coplanar and symmetrical structures on a single substrate were obtained yielding whole-diamond based conducting electrodes. TiN contacts (~300 nm) were deposited on these electrodes to facilitate electrical measurements.The diamond substrate was incorporated in an Electrochemical Impedance Spectroscopy (EIS) unit. Specific advantages of EIS experiments comprise fast, reliable and label-free readout of biological samples. The electrodes were sequentially measured over a broad frequency range between 100 Hz to 1 MHz in different buffer solutions which are relevant for biological measurements (PBS, PCR-buffer, NaOH). All electrode channels exhibit a stable and uniform behaviour, making them most suitable for a differential measurement set-up. Next the diamond electrodes were functionalized by adsorbing antibodies (receptor proteins) on the diamond electrodes. This serves as a recognition layer for C-Reactive Protein (CRP), a risk factor for cardiovascular diseases. The successful and specific bio-functionalization has been verified with confocal fluorescence microscopy using fluorescently Alexa labelled antibodies, also specific developed ELISA protocols indicate that after adsorption, the antibodies still exert their specific binding capability against CRP. This presents a functional biosensor based on whole-diamond electrodes which allow differential EIS measurements for CRP immunosensing in buffer- and human-serum solutions.
9:00 PM - QQ9.53
Highly-sensitive and Selective Detection of Hg2+ Ions Based on Direct Redox Reaction with Single Walled Carbon Nanotubes.
Tae Hyun Kim 1 , Chang-Seuk Lee 1 , Jongmin Won 1
1 Chemistry, Soonchunhyang University, Asan Korea (the Republic of)
Show AbstractThe rapid detection of mercury is crucial because of its harmful effect on human health. Various techniques have been demonstrated for the detection of Hg2+. However, previous approaches often suffer from bulky system size, sophisticated instrumentation, and the limitation in sensitivity and selectivity. Thus, there is a high demand to develop new approaches for Hg2+ detection with high sensitivity, selectivity, and great simplicity to protect our health and environment.Herein, we report the extremely strong response of single walled carbon nanotube (swCNT) conductance to the exposure of Hg2+ caused by the strong redox reaction between swCNTs and Hg2+ ions, which is quite unique compared with other metal ionic species. Furthermore, we successfully demonstrated highly-selective and sensitive Hg2+ sensors based on this unique redox reaction. Our sensors exhibited spontaneous and selective responses to Hg2+ ions with the detection limit comparable with those of other state-of-the-art methods and the maximum allowable limit of mercury ions in drinking water by US environmental protection agency (EPA) regulation.
9:00 PM - QQ9.54
Low Temperature Directly-growth Flexible CNT Biosensors.
Yun-Tzu Chang 1 , Tri Rung Yew 2
1 Materials Science and Engineering, National Tsing Hua University, Hsinchu City Taiwan, 2 Materials Science and Engineering, National Tsing Hua University, Hsinchu City Taiwan
Show AbstractIn this study, the biosensors which can provide real-time and quick-response detection are fabricated by carbon nanotubes (CNTs) grown directly on polyimide flexible substrate at low temperatures (≤400 °C). The vertically grown CNTs exhibit better sensitivity of the biosensors than coated CNTs because of their abundant surface area that can provide more bonding sites during detection. In addition, the surface of CNTs was modified with functional groups to improve electrical properties and biocompatibility. The CNTs were also modified with antibody for specific bonding for liver function detection. Finally, a biocompatible polymer was coated on CNT surface as an insulator for future applications of flexible biosensors on in-vivo sensing. The chemical bonding on the CNT surface was inspected by X-ray photoelectron spectroscopy. The amount of bound antibodies was characterized by enzyme-linked immunosorbent assay. The quality of CNTs was also measured by Raman spectrum. In addition, the morphology of CNTs was observed by scanning electron microscopy and high-resolution transmission electron microscopy. The electrical properties of biosensors were characterized by electrochemical impedance spectroscopy and cyclic voltammetry.
9:00 PM - QQ9.55
Electrons over Diamond.
Bradford Pate 1 , Matthew Ray 1 , Jeffrey Baldwin 1 , James Burgess 1 , Tatyana Feygelson 2 , James Butler 1 , Jonathan Shaw 1 , Maxim Zalalutdinov 1
1 , Naval Research Laboratory, Washington, District of Columbia, United States, 2 , SAIC, Washington, District of Columbia, United States
Show AbstractThe presence of electronic states above solid surfaces, spatially outside of the solid and created by the classical image potential, are well established on metals and semiconductors, as well as thin and thick film dielectrics. Over the past 4 decades, extensive experiment and theory efforts have established properties of image potential “surface electrons” on condensed rare gas dielectrics [1], most notably, liquid helium. Research continues to examine motion and microscopic control of surface electrons over liquid helium [2], as well as schemes for advanced computing [3]. On liquid helium surfaces, the combination of true negative electron affinity (NEA) with the image potential gives rise to a long lifetime (weeks) and high mobility (up to 108 cm2/V-sec) two-dimensional electron system (2DES). In the late nineties, Geis and co-workers took advantage of image potential states at the NEA diamond surface to demonstrate a novel triple junction emitter [4]. It is long speculated that electrons on NEA diamond would have similar properties as on liquid helium. Here, we examine the properties and opportunities for development of a 2D electron system (2DES) of image potential surface electrons over diamond. We discuss expected electronic properties, spectroscopy and material structures for lateral charge control. Our experimental effort to establish the lifetime, mobility, and lateral control of electrons over diamond will be presented.1. E. Andrei, Ed., Two-Dimensional Electron Systems on Cryogenic Substrates, (Kluwer Academic Press, Dordrecht, 1997).2. D. Rees, K. Kono, Journal of Low Temperature Physics 158, 301 (Jan, 2010).3. S. A. Lyon, Physical Review A 74, (Nov, 2006).4. M. W. Geis et al., Nature 393, 431 (Jun, 1998).
9:00 PM - QQ9.56
Field Emission Mechanism of Nitrogen-doped Diamond with Different C-N Concentration.
Tomoaki Masuzawa 1 , Yuki Kudo 2 1 , Yusuke Sato 1 , Ichitaro Saito 3 , Takatoshi Yamada 4 , Angel T. Koh 5 , Daniel C. Chua 5 , Teruo Yoshino 1 , Wang Chun 1 , Satoshi Yamasaki 2 6 , Ken Okano 1
1 Department of Material Science, International Christian University, Tokyo Japan, 2 Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba Japan, 3 Department of Engineering, University of Cambridge, Cambridge United Kingdom, 4 Nanotube Research Center, National Institute of Advanced Industrial Science and Technology, Tsukuba Japan, 5 Department of Materials Science and Engineering, National University of Singapore, Singapore Singapore, 6 Energy Technology Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba Japan
Show AbstractDiamond has been considered to be a strong candidate of the field emitter materials due to the negative electron affinity of its hydrogen-terminated surfaces. Development of chemical vapor deposition(CVD) technique even accelerated the research in this area. In previous studies, heavily nitrogen(N)-doped diamond grown by hot filament CVD was reported to exhibit a remarkably low threshold field of as low as 0.5V/µm. Recently, Yamaguchi et al. proved that the electrons are emitted from the conduction band of the heavily N-doped diamond, utilizing the negative electron affinity of ~0.8 eV. They also reported that electrons are emitted from the mid-gap level for lightly N-doped diamonds, which may be attributed to the field emission from either deep-donor level or defect level. The nitrogen concentrations in the N-doped diamonds were investigated by time-of-flight secondary ion mass spectroscopy (ToF-SIMS). The results suggested that there is a correlation between C-N concentration and the threshold field for electron emission. In order to clarify this correlation, N-doped diamond with different N concentrations were prepared and the field emission properties were analyzed. N-doped diamond samples with different nitrogen concentrations were prepared. Two samples were deposited using dimethyl urea, where the N concentrations in the reaction solutions were (a) 100ppm and (b) 10,000ppm respectively. A N-doped diamond doped with urea was used as a reference. N-doped diamond samples were grown by hot filament chemical vapor deposition (CVD). Acetone was used as a carbon source, and one of two types of N-sources, urea or dimethyl urea, was dissolved for N incorporation. Methanol was used as an intermediate solvent for adding urea into acetone, whereas dimethyl urea was directly dissolved into acetone.The nitrogen concentration in the form of C-N was evaluated for each of the samples using ToF-SIMS. The field emission properties were evaluated using emission current-anode voltage characteristics and threshold voltage-anode/cathode distance(V-d) plot, where anode-cathode voltages at emission current of 10-9A were defined as threshold voltages for comparison. Combined ultraviolet photoelectron spectroscopy and field emission spectroscopy was used to evaluate the energy level, where electrons are emitted from.
9:00 PM - QQ9.57
Photo Enhanced Thermionic Emission of Nitrogen-doped Hydrogen-terminated Ultra-nanocrystalline Diamond Films.
Tianyin Sun 1 , Franz Koeck 1 , Robert Nemanich 1
1 Department of Physics, Arizona State University, Tempe, Arizona, United States
Show AbstractDiamond and other carbon based materials have been under investigation for their application as electron emitters. With n-type doping and hydrogen surface termination an extremely low work function has been demonstrated on ultra-nanocrystalline diamond (UNCD) films, and low temperature (<400C) thermionic emission of such films has been reported by our group. Nitrogen-doped, hydrogen-terminated UNCD films display a work function as low as 1.3eV at a temperature of ~500°C, which suggests that visible light could stimulate photo-emission. By employing a Xe arc lamp in combination with band pass filters, the UNCD films have been illuminated with light from 340nm to 600nm, and the spectrum of the photoemitted electrons has been recorded. The spectrum is particularly interesting as the sample is heated from 400°C to 500°C, and features are identified from both thermionic and photo-emission processes. The results clearly establish the presence of photo enhanced thermionic emission. There is a complex interaction between the two processes as the temperature is heated. In addition, the two effects show an opposite dependence on the thickness of the film. These results reveal possible application of UNCD emitters as visible light photo cathodes.This research is supported through the Office of Naval Research.
9:00 PM - QQ9.58
Nanocomposites With CTNs As Electrode Material in Lithium Ion Batteries.
Mark Weiss 1 , Hubert Koller 1
1 , Institut fuer physikalische Chemie der WWU Münster, Münster Germany
Show AbstractMultiwalled carbon nanotubes (MWNTs) and TiO2 are combined in a nanocomposite to obtain a novel anode material for Li-ion-batteries. A sol-gel process is used to synthesize this nanocomposite. To increase the compatibility between the sol-gel matrix and the MWNTs a non-covalent modification is used. The structure of the nanocomposite, which is expected to play an important role for the electrochemical performance, is analyzed by XRD, N2 sorption measurement and SEM. The results show that the nanocomposite is microporous and crystalline (Anatase) with nearly fully isolated MWNTs. The electrochemical performance is analyzed by cyclic voltametry and cyclization of the nanocomposites as anode material in a Li ion battery.
9:00 PM - QQ9.59
Carbon Nanostructures as GPa High-pressure Cells.
Litao Sun 1
1 Key Lab of MEMS of Ministry of Education, Southeast University, Nanjing China
Show AbstractExperiments on individual nanoparticles are generally difficult but can be carried out by the techniques of modern in situ electron microscopy. Here we report an innovative in-situ experimental method that can provide insight into the deformation process of individual nanometer-sized metal crystals inside transmission electron microscope. Concentric closed-shell carbon nanostructures that contract under electron irradiation are used as nanoscopic deformation cells. Controlled irradiation of multiwalled carbon nanotubes can cause large pressure (up to 40GPa) buildup within the nanotube cores that can plastically deform, extrude, and break solid materials that are encapsulated inside the hollow cores [1]. The elastic and slow plastic deformations of nanometer-sized metal crystals inside carbon onions are monitored at an atomic scale by in-situ electron microscopy [2,3]. When the compression modulus of the crystals is known, the pressure can be calculated by precisely measuring the lattice spacings of crystals which are surrounded by compressing graphitic shells. A prevailing pressure of more than 20 GPa from graphitic cages show that these crystals deform near their theoretical strength limits. References: [1] L. Sun et al., “Carbon Nanotubes as High-pressure Cylinders and Nano-extruders”, Science 312, 1199 (2006)[2] L. Sun et al., “The elastic deformation of nanometer-sized metal crystals in graphitic shells” Appl. Phys. Lett. 89 263104 (2006)[3] L. Sun et al.,"The plastic deformation of single nanometer-sized crystals", Phys. Rev. Lett. 101, 15610(2008)
9:00 PM - QQ9.6
Preparation and Characterization of Vinyl and Organosilane-treated Carbon Nanofibers for Tribological Enhancement of Polyethylene Nanocomposites.
Weston Wood 1 , Katie Zhong 1
1 Mechanical and Materials Engineering, Washington State University, Pullman , Washington, United States
Show AbstractA critical aspect of polymer composite technology is that reinforcement is well-bonded to the polymer matrix. This is increasingly important for non-polar polymers such as polyethylene, in which interactions are limited to Van der Waals forces unless fillers are appropriately treated. In this work, we synthesized silane coatings onto carbon nanofibers (CNFs) specifically for reinforcement in polyethylene matrices. Two types of silane coupling agents were applied: octacdecyltrimethoxy-silane (ODTS) and vinyl trimethoxy-silane (VTS). The silane-CNF treatments were applied by refluxing in ethanol, after which the treated CNFs samples were dried in vacuum. The pH during reflux was adjusted in order to manipulate the reactivity of the silane groups. Characterization of each treatment was performed using Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and thermal gravimetric analysis (TGA). For ODTS, all characterization results confirmed the presence of the silane coating with varying thickness that depended on pH during the reflux of the surface treatment. In contrast, characterization VTS-treated CNFs did not show such pH-dependant coating thickness, and FTIR showed only trace amounts of VTS on the CNFs. For ODTS-treated CNF/polyethylene composites, a drastic improvement in the wear resistance was seen in the composites with the thickest coating, indicating improved interactions. These results demonstrated that ODTS-treated CNFs with thick coatings (>50nm) of ODTS have much potential for reinforcement in polyethylene composites.
9:00 PM - QQ9.60
Generating Electrical Contacts to Individual Carbon-based Nanostructures Using Dip-Pen Nanolithography.
Steve Park 1 , Zhenan Bao 2
1 Materials Science and Engineering, Stanford University, Stanford, California, United States, 2 Chemical Engineering, Stanford University, Stanford, California, United States
Show AbstractThe field of carbon-based and organic electronics has a wide variety of novel and exciting applications such as electronic paper, flexible displays, flexible solar cells and sensors. However, in order to properly engineer their performance, it is necessary to understand the intrinsic electronic properties of individual carbon-based and organic nanostructures at the nanoscale. Examples of such nanostructures include carbon nanotubes, graphene, single organic crystals, and individual organic grains. Despite such an essential need to characterize the structure/property relationships of the aforementioned nanostructures, this task has traditionally been hampered by the lack of a technique that can generate electrical contacts to individual nanostructures with high efficiency and without causing damages to the nanostructures. Herein, we introduce a technique of generating electrical contacts to individual nanostructures using Dip-Pen Nanolithography (DPN). Briefly stated, DPN uses an “inked” Atomic Force Microscopy (AFM) tip to directly deposit a material of interest onto a substrate with high resolution and registration. With its combined AFM imaging and lithographic capability, DPN has the unique ability to generate electrical contacts directly onto the nanostructure of interest, without having to perform multi-step alignment procedures. As an initial demonstration of our technique, we have successfully generated electrical contacts to carbon-based materials such as single-wall carbon nanotubes (SWNT) and graphene sheets, and have characterized their electronic properties. The methodology involves depositing a thin layer of Au onto a substrate with SWNTs or graphene flakes, and using DPN to deposit an etch resist at the ends of the nanostructures of interest, which after conducting wet-chemical Au etch becomes the Au electrical contacts. Additionally, using the multi-pen array, we have demonstrated that electrodes can also be patterned concurrently in a high-throughput manner with precise feature-size controllability and low tip-to-tip feature-size variability. Furthermore, the gap resolution of these electrodes has been controllably fabricated down to sub-100 nm regime. This development presents a novel high-throughput electrode fabrication technique with mild and simple processing conditions at a relatively low cost. Moreover, to demonstrate the efficacy of our multi-pen generated parallel electrodes, we have generated SWNT devices in a high-throughput manner with excellence device yield. In summary, we have developed a facile technique of generating electrical contacts to individual nanostructures using Dip-Pen Nanolithography and have utilized this technique to characterize individual SWNTs and graphene sheets. Currently, the technique is being extended to generating electrical contacts to other organic nanostructures.
9:00 PM - QQ9.61
Organic Solar Cells using Graphene/SWNT Transparent Thin Films as Transparent Conductive Electrodes.
Aaron George 1 , Ali Guvenc 2 , Wei Wang 1 , Jian Lin 3 , Jiebin Zhong 3 , Mihri Ozkan 2 , Cengiz Ozkan 3
1 Materials Science and Engineering, University of California Riverside, Riverside, California, United States, 2 Electrical Engineering, University of California Riverside, Riverside, California, United States, 3 Mechanical Engineering, University of California Riverside, Riverside, California, United States
Show AbstractThe organic solar cell shows potential as a viable option for photovoltaic devices because they can be produced in large volumes at relatively low production cost. Metal oxides such as ITO are brittle and are limited for use on flexible substrates unlike the widely used polymers in organic photovoltaic devices. A substitute for ITO demonstrating similar performance but lower cost is needed to further the possibility of making organic solar cells a strong economic option. In this work we replace the widely used electrode material ITO with a layer of 2D carbon nanostructure with carbon nanostructure CNT. This material is suitable as transparent conductive anode because it is highly transparent and highly conductive. The CNTs increase the surface area and therefore a large increase in absorption. We obtain Graphene/SWNT films with different thicknesses and the efficiencies of these solar cells are compared.
9:00 PM - QQ9.63
Hysteresis-free Operation of Carbon Nanotube Based Ferroelectric Field-effect Transistor.
Yeon sik Choi 1 , Jin-woo Sung 1 , Seok Ju Kang 1 , Cheolmin Park 1
1 , Yonsei University, Seoul Korea (the Republic of)
Show AbstractThe two dimensional random networks of Single-Walled carbon nanotubes (SWNTs) field-effect transistors have been a great attraction for exploiting their novel electronic properties, for instance as a semiconducting channel layer in a field effect transistor (FET) favorable for large area organic electronics. A CNT network transistor is composed of a mixture of semiconducting and metallic CNTs and exhibits a gating effect with an ON/OFF current ratio which depends on the numbers of metallic CNTs between the metal contact, and also depends on the contact resistance between the semiconducting CNTs and the electrodes. CNT network transistor offers greater field-effect mobility and better mechanical flexibility than other organic thin-film channels, and can be operated at the source-drain voltage orders of magnitude lower than that required for thin-film transistors of comparable size. One of the critical issues that prevents the development of CNT network transistor is the large hysteresis appearing often in the transfer characteristics of the source-drain current as a function of gate voltage. The origin of hysteresis is still unclear. A possible explanation is that the charge trapping by water molecules around the nanotubes and SiO2 surface change the channel conductance at a given voltage. We developed a new method to control I-V current hysteresis of a CNT network transistor via ferroelectric polymer gate insulator, such as poly(vinylidene fluoride-trifluoroethylene) P(VDF-TrFE). In P(VDF-TrFE), permanent dipole formation between hydrogen and fluorine atom can be rotated around carbon backbone upon application of electric field large enough to induce conformational change of the polymer chain, resulting in bistability. Ferroelectric field effect transistors also give rise to current hysteresis due ferroelectric bistability. Further, P(VDF-TrFE) as gate dielectric in CNT network channel allows us to control the I-V hysteresis windows of CNT network by controlling the ferroelectric polarization. As a result, when we combine the characteristics of ferroelectric material, for instance pyroelectric or piezoelectric, we can make not only hysteresis-free CNT network transistors but also pressure or temperature sensor.
9:00 PM - QQ9.64
Carbon Nanotube Poly NIPAM Thermal and Light Responsive Actuators.
Xiaobo Zhang 1 3 , Cary Pint 2 3 , Bryan Schubert 2 , Arash Jamshidi 2 , Ronald Fearing 2 , Ali Javey 2 3
1 Materials Science and Engineering, UC Berkeley, Berkeley, California, United States, 3 , Lawrence Berkeley National Laboratory, Berkeley, California, United States, 2 EECS, UC Berkeley, Berkeley, California, United States
Show AbstractPoly NIPAM (N-isopropylacrylamide) is a thermal responsive polymer that can be synthesized by polymerizing aqueous NIPAM monomer utilizing UV radiation or other synthetic methods. The main impetus to study this material is due to a novel thermally driven transition from a hydrated state to a dehydrated state, which has thus far motivated its use for drug delivery, chemical connectors, and optical switches. Here we demonstrate thermal responsive actuators with single-walled carbon nanotubes (SWNT) and poly NIPAM composites that appeal to these applications, but exhibit a response time that is significantly enhanced by the carbon nanotubes and can be optically driven. Hydrogels containing SWNT were produced by utilizing sodium deoxycholate-suspended SWNT in NIPAM monomer solution, followed by UV irradiation to induce polymerization. SWNT were found to be uniformly dispersed in the hydrogels, and the SWNT-pNIPAM hydrogels exhibited up to five times faster thermal response compared to pNIPAM actuators. Furthermore, these SWNT hydrogels demonstrated ultra-fast local response to near-infrared laser excitation on sub-millisecond time scales. Finally, to demonstrate the large-scale application of this work, we demonstrate a LDPE (Low Density Polyethelene)/CNT-pNIPAM bilayer design scheme to make programmable thermal and light responsive actuators which can self-assemble into different shapes upon heating up. This could enable a number of novel applications such as light-tracking solar devices or light-driven hinges for smart solar panels.
9:00 PM - QQ9.65
Polymer-assisted Dispersion Single-wall Carbon Nanotues for Fabrication of Transparent Conducting Film.
Wei-Chao Chen 1 4 , Hsiang-Ting Lien 2 , Tzu-Wei Cheng 3 , Chao-Chin Su 3 , Kuei-Hsien Chen 4 , Li-Chyong Chen 5
1 Department of Engineering and System Science, National Tsing Hua University, Hsinchu Taiwan, 4 Institute of Atomic and Molecular Science, Academia Sinica, Taipei Taiwan, 2 Institute of Polymer Science and Engineering, National Taiwan University, Taipei Taiwan, 3 Institute of Organic and Polymeric Materials, National Taipei University of Technology, Taipei Taiwan, 5 Center for Condensed Matter Science, National Taiwan University, Taipei Taiwan
Show AbstractThe development of technologies to deliver low cost flexible alternatives by using single walled carbon nanotubes (CNT) are fledgling but potential in optoelectronic devices, such as touch panel in smart mobile, and transparent conductive films. Although carbon nanotubes (CNTs) electrode show promise in having a prominent characteristics, none of these mentioned processes in literature promise uniform performance in large area. Here, we propose a method to fabricate CNTs films with highly dispersed hybrid solution accompanied ultrasonic spray coating [1]. Because of Van der Waal’s forces within individual CNTs, dispersion of CNTs in solvent is an important issue. By utilizing conducting polymer as surfactant to facilitate SWNTs disperse in solvent, we used different chain length of the tail group (from P3BT to P3DDT) and different backbone length (molecular weight from 25K to 85K) of the aforementioned conducting polymer. The results reveal that SWNTs mixed with the long tail group and short head group polymer exhibit relatively higher transmittance and conductivity than the rest. A previous study has shown that by reducing the bundle diameter, the junction resistance decreases and with it the number of pathways for charge transports [2]. Therefore, by manipulating different length of tail group and head group of polythiophene, we observed different diameter distribution of exfoliated carbon nanotubes. The various diameter distributions of CNTs were measured by DLS in solution, and through AFM in film. It is believed that the steric effect created by long tail group of polythiophene within two adjacent inter-tubes [3] enables the easy dispersion of CNTs in organic solvent instead of aggregating into bundles. Moreover, other interesting observation was found also between CNTs and polythiophene with the short head group. At low sonication energy, the short head group was found to interact more strongly with the out-surface of carbon nanotubes than the one with longer head group. According to the quantum efficiency measurement, the short head group polymer can interact with carbon nanotubes better at low process energy, thus getting a dispersed hybrid solution. However, to form highly dispersed hybrid solution using the long head group polythiophene, it would require higher process energy (> 30 kilojoule). The present DLS measurement also revealed a decrease in the bundle diameter results from using different length of tail and head group polymer mixed with SWNTs thus explains the increase in the film’s conductivity. Thus, TCF from these dispersions was observed to give good conductivity and high transparency, and the sheet resistance (90 ohm/square) and transmittance (81% in 550 nm) of electrode is almost competitive with other reported CNTs based transparent electrodes to date. Reference [1] R. C. Tenent, Adv. Mater, vol. 21, 3210, 2009[2] P. N. Nirmalraj, Nano Letters, vol. 9, No. 11, 3890, 2009[3] R. S. Cohen, JACS. 126, 14850, 2004
9:00 PM - QQ9.7
Graphene-doped Conducting Polymers.
Ryeo Yun Hwang 1 , Ok Kyung Park 1 , Hyun-Kon Song 1
1 i-School of Green Energy, UNIST, Ulsan Korea (the Republic of)
Show AbstractWe demonstrate that graphene, more specifically, reduced graphene oxide (rGO) can be incorporated as a dopant into a conducting polymer (CP). The enhanced electric and electrochemical properties of CPs by graphene doping are shown. The most essential process that makes CPs (e.g. polypyrroles, polyanilines and polythiophens) conductive is the doping process via which positive charges of polymer backbones are neutralized by anionic dopants during polymerization. The use of functional dopants would be the easy way to widen functionality of CPs. In this work, Poly-anionically functionalized rGO was used as the functional dopant for polypyrrole (pPy). The peculiar properties of graphene including high electric and thermal conductivity are introduced to the pPy film.pPy doped with rGO (pPy[rGO]) shows several advantages, compared with pPy doped with a conventional dopant.(i)pPy[rGO] has higher capacitance per unit mass.(ii)pPy[rGO] keeps electrically conductive in its reduced state. On the other hand, pPy doped with a conventional dopant turns insulating when it is reduced.(iii)Graphene can be easily patterned with pPy through electrodeposition on a patterned circuit.To complete the story from the synthesis of pPy[rGO] to its applications, superior performance of pPy[rGO]-based supercapacitors is demonstrated in terms of capacitance at high power charge/discharge. Also, an immunoassay using interdigitated nanoelectrode array of pPy[rGO] is presented as the second application.