Bulletin of the American Physical Society
2006 APS March Meeting
Monday–Friday, March 13–17, 2006; Baltimore, MD
Session Y18: Focus Session: Carbon Nanotubes: Adsorption and Gas Surface Interactions with Carbon Nanotubes |
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Sponsoring Units: DMP Chair: Aleksey Kolmogorov, Duke University Room: Baltimore Convention Center 315 |
Friday, March 17, 2006 8:00AM - 8:12AM |
Y18.00001: Adhesion of single functional groups to individual carbon nanotubes: electronic effects probed by \textit{ab-initio} calculations Jeffrey Grossman, Giancarlo Cicero, Giulia Galli The interfacial interaction of simple functional groups (-NH$_{2}$, -CN, -CH$_{3}$ -CHOCH$_{2})$ with single wall carbon nanotubes (SWCNT) was investigated using \textit{ab-initio} calculations. Binding energies and attachment forces were computed using Density Functional Theory (DFT) in the local density approximation, and Quantum Monte Carlo calculations were employed to test DFT accuracy in describing weak interactions for the controversial case of an oxygen molecule. We find that computed energies and forces are very sensitive to small variations of the electronic charge on the nanotube. In particular, the presence of a solvent (polar or non-polar), and thus of a small charge transfer from or to the tube, may alter the relative strength of adhesion forces for different functional groups, as compared to vacuum. [Preview Abstract] |
Friday, March 17, 2006 8:12AM - 8:24AM |
Y18.00002: Tunable Nanoresonators Constructed from Telescoping Nanotubes Kenneth Jensen, Caglar Girit, William Mickelson, Alex Zettl We have created a tunable mechanical nanoscale resonator with potential applications in precise mass, force, position, and frequency measurement. The device consists of a specially prepared multiwalled carbon nanotube (MWNT) suspended between a metal electrode and a mobile, piezo-controlled contact. By exploiting the unique telescoping ability of MWNTs, we controllably slide an inner nanotube core from its outer nanotube casing, effectively changing its length and tuning its flexural resonance frequency. [Preview Abstract] |
Friday, March 17, 2006 8:24AM - 8:36AM |
Y18.00003: Interlayer forces in telescoping nanotubes Andras Kis, Kenneth Jensen, Shaul Aloni, William Mickelson, Alex Zettl The ability to fabricate low-friction surfaces and lubricants is one of the key requirements for the miniaturization of mechanical systems, especially on the nanoscale where friction and surface adhesion often dominate over gravity and even electrostatic attraction. In this context, multiwalled carbon nanotubes (MWNT) have been proposed as the ideal nanobearing because of their inert, ultra-smooth surfaces and the narrow separation between their neighboring shells that prevents the accumulation of contaminant particles between sliding parts. In analogy with graphite, the weak van der Waals interaction between nanotube shells could provide the equivalent of lubrication, allowing easy relative sliding of nanotube layers. We have externally induced telescoping motion in MWNTs while measuring the force acting between the two layers involved in this motion. The restoring van der Waals force is comparable with theoretically predicted values. Defects are found to modulate this force and can lead to jamming. [Preview Abstract] |
Friday, March 17, 2006 8:36AM - 8:48AM |
Y18.00004: Registry-dependent interlayer potential for graphitic systems Aleksey Kolmogorov, Vincent Crespi Standard applications of density functional theory (the local density approximation (LDA) and the generalized gradient approximation (GGA)) without nonlocal corrections do not adequately describe the exfoliation energy of graphite. The GGA, in particular, does not show any binding at physically meaningful interlayer distances. However, the {\it variation} in the energy under interlayer shifts, defined predominantly by the overlap of $\pi$ orbitals, is nearly identical in the two approximations and appears to be much more sound than previously suspected. We combine these results with experimental information on the exfoliation energy to create an improved registry-dependent classical potential for the interlayer interaction in graphitic structures. [Preview Abstract] |
Friday, March 17, 2006 8:48AM - 9:00AM |
Y18.00005: Adsorption of simple aromatic molecules on single-wall carbon nanotubes Lilia M. Woods, Stefan C. Badescu, Thomas L. Reinecke Understanding the adsorption of aromatic molecules on carbon nanotubes is important for nanotube functionalization. We perform ab-initio plane-wave calculations for the adsorption of benzene derivatives such as nitrobenzene, aniline and toluene, using pseudopotentials in the local density approximation. We find that the minimum energy configurations of the molecules are flat along the nanotube, in agreement with experiments on polar molecules [1], and that the dominant part of the binding is physisorbtion. The physisorbed benzene used for reference lies in a graphite-stacking configuration, whereas benzene derivatives have small deviations from this perfect alignment. The deviation from ideal $\pi -\pi $ stacking is a complex process that involves the hybridization between molecular and nanotube levels, a small charge redistribution, and in some cases the formation of narrow conduction bands in the energy gap of semiconductor nanotubes. We trace the differences between derivatives to the properties of the molecular fragments attached to the benzene ring. [1] Snow E.S. et al, Science 307 (5717), 1942 (2005) [Preview Abstract] |
Friday, March 17, 2006 9:00AM - 9:12AM |
Y18.00006: DNA-CNT Interaction - A Density Functional Approach Ralph Scheicher, S. Gowtham, Rajeev Ahuja, Ravindra Pandey Standing at the intersection of the biological regime and the nanomaterials world, DNA-coated carbon nanotubes (CNT) possess features which can make them attractive for a range of applications, e.g., as highly specific nanosensors [1], or as a method to efficiently separate CNTs according to their structure [2]. It is therefore certainly worthwhile to obtain a detailed understanding of the binding between the bases in DNA and the surface of CNTs, preferably from first principles. To this end, we have studied the interaction between single-stranded DNA and single-walled CNTs (SWCNTs) using density functional theory. More specifically, we were interested in assessing the differences in the interaction of the four different bases in DNA, and how important the underlying structure of the CNT is for the orientation of the bases relative to the tube axis. We will report our results on the binding energy, the charge density, and the respective distortion in the electronic structure of the constituents of this hybrid system, depending on the geometrical properties of the CNT and the relative positioning of the DNA. \newline \newline [1] C. Staii \textsl{et al.}, \textsl{Nano Letters} \textbf{5}, 1774-1778 (2005) \newline [2] M. Zheng \textsl{et al.}, \textsl{Science} \textbf{302}, 1545-1548 (2003) [Preview Abstract] |
Friday, March 17, 2006 9:12AM - 9:24AM |
Y18.00007: Molecular hydrogen adsorption on the boron-doped graphene sheet in presence of magnesium and transition metal ZhaoHui Huang, Vnicent Crespi Adsorption of hydrogen molecules onto a boron-doped graphene sheet in the simultaneous presence of magnesium and a transition metal has been studied using density functional methods. This setup is inspired by magnesium dihydride. We obersve that there form bonds between metal and boron atoms, which suggest a potential way to prevent metal from aggregating. Macroscopic aggregation of metal atoms makes this structure useless to adsorb hydrogen. We present results for different combination of transition metal and magnesium, and compare the binding energy of hydrogen molecule adorbed onto those structures. [Preview Abstract] |
Friday, March 17, 2006 9:24AM - 9:36AM |
Y18.00008: Controlled Confinement and Release of Gases in Single-Walled Carbon Nanotube Bundles Christopher Matranga, Bradley Bockrath A simple procedure is described which locks small quantities of SF$_{6}$, CO$_{2}$, and $^{13}$CO$_{2}$ into opened single-walled carbon nanotube (SWNT) bundles and keeps the gas inside the SWNTs above the desorption temperature of these molecules. The confinement technique involves opening the SWNTs with ozonolysis at 300 K followed by vacuum annealing at 700 K. Gases are then cryogenically adsorbed into the opened SWNTs and a locked into the SWNT pores by functionalizing the sample with a low temperature ozone treatment. The low temperature ozone treatment functionalizes the entry ports into the SWNT pores which in turn create a physical barrier for gases trying to desorb through these functionalized ports. The samples are stable under vacuum for periods of at least 24 hours and the trapped gases can be released by vacuum heating to 700 K. Reduced quantities of the trapped gases remain in the SWNTs even after exposure to room air. Fourier Transform Infrared Spectroscopy is used to monitor the functionalities resulting from the ozone treatment and to detect the trapped gas species. [Preview Abstract] |
Friday, March 17, 2006 9:36AM - 9:48AM |
Y18.00009: Physisorption Kinetics in Carbon Nanotube Bundles Jared Burde, M. Mercedes Calbi The possibility of adsorbing gases in the interstitial channels that lie between nanotubes in a bundle is still the subject of much discussion because experimental observations do not seem to confirm the existence of adsorbed gases on this site as it has been predicted by several theoretical studies (that assume infinitely long tubes). After exploring the potential energy surfaces near the ends of the tubes, we have recently shown how the presence of a high binding energy site right before the entrance of the channel slows down the adsorption rate of H$_{2}$ dramatically $^{1}$. Using a Kinetic Monte Carlo scheme, we present here a comprehensive study of the adsorption kinetics in the channels modeling the transport of various gases through the ends of the bundle. In order to facilitate the comparison with adsorption experiments, the results are given in terms of the equilibration time as a function of coverage, for different temperatures. In addition, the effect of cluster formation at the end of the bundle is analyzed. $^{1}$ M. Mercedes Calbi and J. L. Riccardo, \textit{``Energy barriers at the ends of carbon nanotube bundles: Effects on interstitial adsorption kinetics''}, Phys. Rev. Lett. \textbf{94}, 246103 1-4 (2005). [Preview Abstract] |
Friday, March 17, 2006 9:48AM - 10:00AM |
Y18.00010: Adsorption of TCNQ on the inside and outside surface of single-wall carbon nanohorn aggregates Ryota Yuge, Masako Yudasaka, Jin Miyawaki, Toshinari Ichihashi, Hideto Imai, Yoshimi Kubo, Sumio Iijima Storage and release of various materials into/from single-wall carbon nanohorns (SWNH), a type of single-wall carbon nanotubes, have been studied well, thus SWNHs have become potentially useful in many fields. However, not much is known about the mechanism of adsorption on the walls of SWNHs, which we have investigated using Tetracyano-$p$-quinodimethane (TCNQ). SWNHs were pretreated with O$_{2}$ at 550$^{o}$C to open holes, followed by the treatment with H$_{2}$ at 1200$^{o}$C to remove functional groups (SWNHh). Thermogravimetric analysis revealed that the quantities of TCNQ inside and outside were estimated to be about 0.07 and 0.11 g per 1 g of SWNHh, respectively, which did not increase even for the TCNQ overdosing. Raman spectra of TCNQ adsorbed on SWNHh (TCNQ/SWNHh) showed red shifts of several vibration modes of TCNQ, while the C=C ring stretching (CCr) showed the large blue-shift. This indicates that the quinoid ring of TCNQ strongly interacted with graphene sheets of SWNHh. The blue-shift of CCr Raman-peak is not observed for the charge transfer complexes such ash TTF/TCNQ, Cu/TCNQ, and so on. We will discuss the reason for the large-blue shift of CCr peak of TCNQ adsorbed on SWNHs in the talk. [Preview Abstract] |
Friday, March 17, 2006 10:00AM - 10:12AM |
Y18.00011: Investigation of Fluorinated and Hydrogenated Carbon Nanotubes by STM Dharmpal Takhar, Z. Gu, A. A. Peera, W. E. Billups, J. L. Margrave, K. F. Kelly There is a great deal of interest in the functionalization, in particular fluorination, of carbon nanotubes for the purposes of solvation and subsequent chemical reaction. Towards this end, we report the investigation of fluorinated nanotubes by variable-temperature STM. The atomic-scale fluorine coverage on the fluorotubes with composition was observed as a function of annealing temperature. Upon heating of the fluorotubes, we observe the subsequent desorption of the fluorine initiated around 240 $^{o}$C and proceeding up to 650 $^{o}$C. At higher temperatures, all the fluorine desorbs revealing a number of small defects. Further heating leads to cutting of the fluorotubes which is initiated at these defect locations. We compare these results to our recent investigation of dihydrogen functionalized carbon nanotubes. [Preview Abstract] |
Friday, March 17, 2006 10:12AM - 10:24AM |
Y18.00012: Fast Mass Transport through Sub-2nm Carbon Nanotubes Jason K. Holt, Hyung Gyu Park, Yinmin Wang, Michael Stadermann, Alexander B. Artyukhin, Costas P. Grigoropoulos, Aleksandr Noy, Olgica Bakajin We report gas and water flow measurements through microfabricated membranes with sub-2nm aligned carbon nanotubes as pores. The measured gas flow exceeds predictions of the Knudsen diffusion model by at least an order of magnitude. The measured water flow rate exceeds values calculated from continuum hydrodynamics models by two to three orders of magnitude and agrees with flow rates extrapolated from molecular dynamics simulations. The gas and water permeabilities of these nanotube-based membranes are orders of magnitude higher than those of commercial polycarbonate membranes, despite having an order of magnitude smaller pore sizes. These properties should enable more energy-efficient nanoscale filtration, as well as fundamental studies of mass transport in confined environments. [Preview Abstract] |
Friday, March 17, 2006 10:24AM - 10:36AM |
Y18.00013: STM Investigation of Functionalized Carbon Nanotube Self-Assembly on Gold Jun Zhang, Lei Zhang, Valery Khabashesku, Andrew Barron, Kevin Kelly Self-assembly has proven a powerful technique for patterning and building devices at the nanometer level. Scanning tunneling microscopy (STM) is the ideal tool for probing the chemistry and physics of these types of nanostructures. Building upon on our previous carbon nanotube research, we have investigated thiol- and thiophene-functionalized nanotubes. The motivation is to use these functional groups as a means to self-assemble tubes on surfaces by exploiting the well-established Au-S chemistry. Thiol and thiophene substituted nanotubes were assembled on bare gold surfaces as well as inserted into hexanethiol self-assembled monolayers and imaged by STM. The thiol and thiophene functional groups work as anchors, strongly binding the SWNTs to the gold. Additionally, we have measured the size and spatial distribution of the functional groups along the nanotube sidewalls. [Preview Abstract] |
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