Bulletin of the American Physical Society
2006 APS March Meeting
Monday–Friday, March 13–17, 2006; Baltimore, MD
Session D18: Focus Session: Carbon Nanotubes: Synthesis and Growth II |
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Sponsoring Units: DMP Chair: Robert Hauge, Rice University Room: Baltimore Convention Center 315 |
Monday, March 13, 2006 2:30PM - 2:42PM |
D18.00001: Growth of Single-Walled Carbon Nanotubes with Size-Controlled Catalysts Yaqiong Xu, Kunal Shah, Behrang Hamadani, Richard Smalley, Robert Hauge A single-walled carbon nanotube (SWNT) growth system has been developed with chlorine-containing gas to control the size of catalysts during growth. The role of catalyst size has been studied with respect its effects on SWNT growth, such as random surface growth, organized vertical growth and SWNT seeds re-growth. The effect of catalyst size on SWNT etching will also be reported. [Preview Abstract] |
Monday, March 13, 2006 2:42PM - 2:54PM |
D18.00002: Seeded Growth of Single-Walled Carbon Nanotubes from Open-ended SWNT Substrates Myung Jong Kim, Erik Haroz, Hongwei Shan, Nolan Nichilas, Carter Kittrell, Robert Wheeler, Tia Benson-Tolle, Yeonwoong Jung, David Luzzi, T.J. Wainerdi, Howard Schmidt, Robert Hauge, Richard Smalley We prepared nanoscopically flat open-ended SWNT substrates from SWNT spun fibers by using the focused ion beam cutting technique followed by various etching and cleaning schemes or alternatively from vertically aligned SWNT film by flipping over. Deposited catalyst was docked to the open ends of SWNTs, and carbon feedstocks were catalyzed into continued single-walled carbon nanotube growth resembling 1D molecular epitaxy in both the cold wall furnace and the hot wall furnace setups. The data obtained from Raman spectroscopy indicates that the (n, m) structure of the newly grown SWNT was cloned from that of the pre-existing SWNT substrate. Such results lead us to believe that this method will provide us with a means of chirality-controlled SWNTs growth on a macroscopic scale using a fairy general and scalable setup in the future. [Preview Abstract] |
Monday, March 13, 2006 2:54PM - 3:06PM |
D18.00003: Position-Controlled, Rapid Growth of Single-walled Carbon Nanotubes D. Styers-Barnett, Z. Liu, C. M. Rouleau, H. Cui, D. B. Geohegan, A. A. Puretzky `Fast-heating' chemical vapor deposition (CVD) is a proven approach for the growth of long individual single-walled carbon nanotubes (SWCNTs). However, obtaining insights into how fast a carbon nanotube can grow is still of scientific and technical importance. Here, we describe a new CVD technique to synthesize SWCNTs using laser irradiation as the heat source. By adjusting the laser conditions, the heating time can be precisely controlled. Additionally, using a laser provides localization of the thermal energy, allowing position controlled growth. Temperature profiles of the substrate, measured by fast, in situ optical pyrometry, show controlled heating to CVD temperatures in a few seconds. Growth rate, yield, and diameter distribution of SWCNTs vary dramatically depending on catalysts, feedstock gases, and heating profile parameters, indicating this laser-CVD technique may provide local control over growth conditions and may pave a way for investigating the growth mechanism of `fast-heating' carbon nanotubes. [Preview Abstract] |
Monday, March 13, 2006 3:06PM - 3:18PM |
D18.00004: Effect of Catalyst Particle Size on CVD Growth of Single-Walled Carbon Nanotubes. A. Harutyunyan, E. Mora, J-W. Yoo, T. Tokune, A.J. Epstein A series of Fe catalysts with different mean diameter supported on alumina with different molar ratios were studied before and after SWNTs growth by using magnetic and Raman measurements to follow changes on catalyst particle size and its relationship with diameter of grown tubes. After the growth, based on blocking temperature values and Langevin function analysis, it was determined that for all catalysts, an increase and redistribution of particle size occurred. This is explained in terms of particle agglomeration, due to carbon-induced liquefaction accompanied with an increase in catalyst mobility. The free path of supported Fe particles was estimated to be $>$2.1nm. For big particles no correlation between catalyst size and nanotube diameter was observed. Analysis of the intensity of Breit-Wigner-Fano line contribution in the Raman G-band revealed that big catalyst particles are more selective to tubes chiralities, and more favorable to the growth of particular metallic tubes. [Preview Abstract] |
Monday, March 13, 2006 3:18PM - 3:30PM |
D18.00005: New empirical potentials between iron nanoparticles and oxide substrates Aiqin Jiang, Neha Awasthi, Aleksey Kolmogorov, Kim Bolton, Elena Mora, Toshio Tokune, Avetik Harutyunyan, Stefano Curtarolo Interaction of iron catalyst nanoparticles with a substrate may influence nucleation and growth mechanism of carbon nantobutes (CNT) by shifting the melting temperature of the supported iron particles. To account for this effect we have used ab initio calculations to develop empirical potentials between iron nanoparticles and oxide substrates. Simulations have been performed on Fe/Al$_{2}$O$_{3}$ system with Al$_{2}$O$_{3}$ substrate fully relaxed. We have demonstrated that the surface rearrangement effects are significant but can be naturally incorporated into a simple Morse potential, which describes the total nanoparticle-substrate binding. The influence of different substrate surface terminations and positions of Fe layers on the strength of binding are discussed. Potentials for Fe and other oxide substrates are also being evaluated. [Preview Abstract] |
Monday, March 13, 2006 3:30PM - 3:42PM |
D18.00006: Phase diagrams for Fe-C nanoparticles: A Molecular Dynamics Study Neha Awasthi, Aiqin Jiang, Aleksey Kolmogorov, Feng Ding, Kim Bolton, Elena Mora, Toshio Tokune, Avetik Harutyunyan, Stefano Curtarolo Fe nanoparticles are widely used as catalysts for carbon nanotube growth. In order to better understand the melting and phase transition properties of these nanoparticles, molecular dynamics (MD) simulations are performed to determine the melting point of Fe-C nanoparticles ($\sim $ 1- 4 nm size) as a function of size and carbon concentration. The temperature dependence of the total energy and the Lindemann index characterize the melting of nanoparticles. For free (unsupported) Fe-C clusters, it is observed that the eutectic point (in the phase diagram) shifts with nanoparticle size. We have investigated how the presence of a substrate affects the melting process of the Fe-C nanoparticles. [Preview Abstract] |
Monday, March 13, 2006 3:42PM - 3:54PM |
D18.00007: Carbon Nanotube Growth Under Applied Pressure: Mechanical Energy Output and Control of Film Structure A.J. Hart, A. Slocum We measure the force which can be exerted by a film of vertically-aligned carbon nanotubes (CNTs) as it grows by thermal CVD. The thickness of the film measured after a growth duration of 15 minutes decreases in an approximately linear fashion with the logarithm of pressure which is applied by placing a tungsten weight on the substrate prior to growth. With increasing pressure, the internal structure of the film changes from well-aligned, to less-aligned with bending and possible single-mode buckling of the CNTs, to predominately collapsed in an ``accordion'' pattern having a spatial wavelength of 0.1-1 $\mu$m. While the mechanical energy exerted is significantly less than major energetic steps in the growth reaction, a growing CNT film can lift tens of thousands of times its own weight. The equivalent volumetric energy density of 2.4$\times 10^4$ J/m$^3$ is comparable to muscle. We utilize this principle to fabricate CNT structures which grow to conform to the shape of an etched silicon template, which is clamped against the growth substrate. This technique surpasses traditional methods using two-dimensional catalyst patterns, as it enables fabrication of CNT structures having arbitrarily sloped surfaces, and does not require catalyst patterning. CNT films and structures having controlled density and conformation, such as fabricated by changing the pressure applied during growth, will be useful for applications including electrochemical energy storage and fluid filtration, and as scaffolds for biological materials. [Preview Abstract] |
Monday, March 13, 2006 3:54PM - 4:06PM |
D18.00008: Laser Irradiation Pretreatment Effects on Catalyst-Coated Silicon and Subsequent CVD Nanotube Growth C.M. Rouleau, G. Eres, H. Cui, D.B. Geohegan, I.N. Ivanov, A.A. Puretzky Developing methods for directed growth of nanotube arrays is important for many nanotube-based applications. Although we are currently growing mm-lengths of vertically-aligned nanotube arrays (VANTAs) from e-beam evaporated catalyst films, further enhancement of length, rate, and density are desired. One promising approach is catalyst modification using laser irradiation. Results are presented on the effects of pulsed KrF laser irradiation prior to chemical vapor deposition of VANTAs. Under typical conditions, a single laser shot was directed at a catalyst coated Si wafer to produce a well-defined laser affected zone. Fluences that ranged from 0.5 to 1.5 J/cm$^{2}$ were employed. In-situ videography was used to study VANTA growth rate in, and adjacent to, the laser affected zone. Atomic force microscopy was used to characterize catalyst surfaces prior to, and following, laser irradiation. The results show that the growth rates for VANTAs within the affected region improved remarkably. The efficacy of this technique in producing changes in VANTA length are shown. [Preview Abstract] |
Monday, March 13, 2006 4:06PM - 4:18PM |
D18.00009: Large-Scale `Surface-Programmed Assembly' of Carbon Nanotube-Based Biosensors Dong Joon Lee, Byung Yang Lee, Jiwoon Im, Minbaek Lee, Seunghun Hong The unique electrical properties of single-wall carbon nanotubes (swCNT) have generated a huge amount of research on nanoelectronic devices and nanosensors. However, a lack of mass-production method of such devices has been holding back their practical applications. Herein, we present a method to assemble a large scale array of swCNT-based biosensors. In this method, self-assembled monolayer patterns direct the `selective assembly' and `alignment' of swCNTs onto substrates in the swCNT solution without relying on any externals forces. Using this method combined with microfabrication, we successfully demonstrated the fabrication of 256 x 256 swCNT-junction array on transparent glass substrates. Furthermore, by immobilizing glucose oxidase or L-glutamate oxidase on the CNT junctions, we fabricated swCNT-based biosensors for real-time detection of glucose or L-glutamate, respectively. [Preview Abstract] |
Monday, March 13, 2006 4:18PM - 4:30PM |
D18.00010: A biomimetic functionalization approach to integration of carbon nanoutbes into biological systems Xing Chen, Un Chong Tam, Carolyn Bertozzi, Alex Zettl Due to their remarkable structural, electrical, and mechanical properties, carbon nanotubes (CNTs) have potential applications in biology ranging from imaging and tissue engineering. To realize these applications, however, new strategies for controlling the interaction between CNTs and biological systems such as proteins and cells are required. Here we describe a biomimetic approach to functionalize CNTs and therefore render them biocompatibility in order to facilitate their integration into biological systems. CNTs were coated with synthetic gycopolymers that mimic cell surface mucin gycoproteins. The functionalized CNTs were soluble in water, resisted non-specific protein binding and bound specifically to biomolecules. The coated CNTs could then be integrated onto mammalian cell surface by virtue of glycan-receptor interactions. Furthermore, the functionalized CNTs are non-toxic to cells. This strategy offers new opportunities for development of biosensor to probe biological processes. References: 1. X. Chen, G. S. Lee, A. Zettl, C. R. Bertozzi, \textit{Angewandte Chemie-International Edition} \textbf{43}, 6111 (2004). 2. X. Chen, U. C. Tam, J. L. Czlapanski, G. S. Lee, D. Rabuka, A. Zettl, C. R. Bertozzi, \textit{submitted}. [Preview Abstract] |
Monday, March 13, 2006 4:30PM - 4:42PM |
D18.00011: Temperature stability of ferritin as a catalyst for Carbon nanotube growth Richard Vanfleet, Mark Esty, Robert Davis In Carbon nanotubes grown with thermal CVD the distribution of tube diameters is dependant upon the growth catalyst. Use of biologically derived catalysts particles have been explored with the hope of narrower diameter distributions resulting from the tight distribution of catalyst particle diameters. Ferritin is the iron storage system in biological systems and consists of a protein shell with an iron hydroxide core. Previous use of catalyst particles generated from ferritin has not consistently resulted in narrow nanotube size distributions. To explore this inconsistency we have studied the particle distribution and temperature stability of surface deposited ferritin on various substrates by TEM. The effects of common substrates (Carbon, SiO$_{2}$ and Si$_{3}$N$_{4})$ on particle densities will be reported. We removed the protein shell with either a low temperature oxygen plasma or a high temperature anneal. With plasma removal of the protein shell the initial particle size and spacing distribution can be maintained at temperatures up to 600 C. [Preview Abstract] |
Monday, March 13, 2006 4:42PM - 4:54PM |
D18.00012: The Effect of Atomic Hydrogen on the Growth of Single-Walled Carbon Nanotubes Robert Hauge, Ya-Qiong Xu, Kunal Shah, Myung Kim, Richard Smalley The role of atomic hydrogen generated in situ with a hot filament has been studied with respect its effects on single-walled carbon nanotube (SWNT) etching and growth. SWNT growth has been studied for both random new surface growth and organized new vertical growth of SWNTs. Its effects on continued growth of SWNT seeds will also be reported. Comparisons will be made to previous studies of SWNT growth in the presence of atomic hydrogen. [Preview Abstract] |
Monday, March 13, 2006 4:54PM - 5:06PM |
D18.00013: Ultra-high-yield growth of vertical single-walled carbon nanotubes Guangyu Zhang, David Mann, Li Zhang, Ali Javey, Yiming Li, Erhan Yenilmez, Qian Wang, Hongjie Dai An oxygen-assisted hydrocarbon chemical vapor deposition method is developed to afford large-scale, highly reproducible, ultra-high-yield growth of vertical single-walled carbon nanotubes. It is revealed that reactive hydrogen species, inevitable in hydrocarbon-based growth, are damaging to the formation of sp2-like SWNTs in a diameter-dependent manner. The addition of oxygen scavenges H species and provides a powerful control over the C/H ratio to favor SWNT growth. The revelation of the roles played by hydrogen and oxygen leads to a unified and universal optimum-growth condition for SWNTs. Further, a versatile method is developed to form V-SWNT films on any substrate, lifting a major substrate-type limitation for aligned SWNTs. [Preview Abstract] |
Monday, March 13, 2006 5:06PM - 5:18PM |
D18.00014: Synthesis of Single Wall Carbon Nanotubes and Carbon Nanohorns by High Power Laser Vaporization D. B. Geohegan, A. A. Puretzky, D. Styers-Barnett, C. M. Rouleau, B. Zhao, H. Hu, H. Cui, I. N. Ivanov, P. F. Britt In this study we present the results of high volume, high yield synthesis of single wall carbon nanotubes (SWNTs) based on a high power industrial Nd:YAG (600 W av. power) laser vaporization of a composite C/Co/Ni target at elevated temperatures. The high power laser also allows us to synthesize single wall carbon nanohorns (SWNHs) as well as metal nanoparticle (e.g., Pt, Pd) decorated SWNHs. Efficiencies and similarities between the conditions for SWNH synthesis are compared with those for SWNTs. \textit{Ex situ} characterizations are compared with \textit{in situ }diagnostics (fast laser plume photography and target pyrometry) to correlate the synthesis conditions with the resulting products and gain insight into their formation processes. Research on Functional Nanomaterials at the Center for Nanophase Materials Sciences is supported by the U. S. Dep. of Energy, Div. of Materials Science, Basic Energy Sciences. The SWNH part of this research is supported by DOE Center of Excellence on Carbon-based Hydrogen Storage Materials. [Preview Abstract] |
Monday, March 13, 2006 5:18PM - 5:30PM |
D18.00015: \textit{In situ} Optical Monitoring and Modeling of Vertically-Aligned Carbon Nanotube Array Growth During Chemical Vapor Deposition A. A. Puretzky, D. B. Geohegan, H. Cui, G. Eres, I. N. Ivanov A detailed experimental study of vertically aligned carbon nanotube array (VANTAs) growth by chemical vapor deposition (CVD) based on time-resolved reflectivity and direct remote microscope imaging as a diagnostic to measure and control the length of VANTAs \textit{in situ} was performed. The VANTA growth was investigated between 500 \r{ }C and 900 \r{ }C on Si substrates with different evaporated multilayer catalysts and different feedstock gases. Nanotube lengths were controlled by rapid evacuation of the chamber. A kinetic model was developed to explain the observed growth kinetics, to discuss the main processes responsible for the growth of VANTAs, and to predict optimal growth conditions for single-wall carbon nanotube (SWNT) arrays. High quality VANTAs containing SWNTs were synthesized and characterized using Raman Spectroscopy. [Preview Abstract] |
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