Bulletin of the American Physical Society
APS March Meeting 2010
Volume 55, Number 2
Monday–Friday, March 15–19, 2010; Portland, Oregon
Session A20: Focus Session: Carbon Nanotubes: Functionalization and Growth |
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Sponsoring Units: DMP Chair: Jeff Blackburn, National Renewable Energy Laboratory Room: C120-122 |
Monday, March 15, 2010 8:00AM - 8:12AM |
A20.00001: Functionalization of Boron- and Nitrogen-Doped Graphene and Carbon Nanotubes: An \textit{Ab Initio} Study Nabil Al-Aqtash , Igor Vasiliev We study the mechanism of covalent functionalization of boron (B) and nitrogen (N) doped graphene and carbon nanotubes by carboxyl (COOH) groups. Our calculations are carried out using density functional theory combined with the generalized gradient approximation for the exchange-correlation functional. The binding energies and equilibrium geometries of carboxylated B/N-doped graphene sheets and carbon nanotubes are examined in cases of graphene and carbon nanotubes containing no defects, containing Stone-Wales defects, and containing vacancies. Our calculations show that B-doping increases and N-doping decreases the binding energy of COOH groups to defect-free and defective graphene and carbon nanotubes. This result is consistent with previous observations that carbon nanotubes and graphene act as electron acceptors with respect to COOH groups. [Preview Abstract] |
Monday, March 15, 2010 8:12AM - 8:24AM |
A20.00002: Electronic properties of double-wall carbon nanotubes and the effect of functionalization Jonathan Laflamme Janssen, Jason Beaudin, Michel C\^ot\'e Although promising for many electronic applications, further understanding of carbon nanotubes systems are required for practical designs. A difficulty currently hindering further development in this field is the considerable degradation of transport properties in a single-wall carbon nanotube (SWCNT) when it is subjected to ambient conditions or functionalized. Double-wall carbon nanotubes (DWCNT) could solve this problem, by allowing the outer tube to be functionalized while the inner tube would retain a pristine structure and it's promising electronic properties. However, our understanding of interactions between the tubes and their consequences on the system's electronic properties is still incomplete. In this presentation, we investigate those interactions using density-functional theory (DFT) calculations. In particular, we investigate separately the effects of structural deformations, Fermi energy realignment and electronic orbital overlap on the band structure of DWCNT. The effects of functionalization will also be addressed. [Preview Abstract] |
Monday, March 15, 2010 8:24AM - 8:36AM |
A20.00003: Electrical and Optical Properties of Covalently Functionalized Double-Walled Carbon Nanotubes Delphine Bouilly, Janie Cabana, Francois Meunier, Maxime Desjardins-Carriere, Francois Lapointe, Francis L. Larouche, Philippe Gagnon, Elyse Adam, Matthieu Paillet, Richard Martel Double-walled carbon nanotubes (DWNT) present a particular geometry in which the inner wall is isolated by the outer wall, while the latter is in direct interaction with the environment. Here, we studied optical and electrical properties of functionalized DWNT derivatives (f-DWNT) prepared by aryldiazonium reactions. We first present absorption spectra of f-DWNT films and resonant Raman spectra of individual f-DWNT assembled in devices. The results show that functionalization reaction occurs only at the surface of the outer wall, leaving the properties of the inner wall intact. Second, electrical transport experiments performed on individual f-DWNT field-effect transistors revealed that the inner wall carry electrical current with a similar intensity as for a single-walled carbon nanotube. Finally, we demonstrate that simple electrical measurements combined with covalent functionalization are sufficient to determine the metallic or semiconductor character of both walls. [Preview Abstract] |
Monday, March 15, 2010 8:36AM - 9:12AM |
A20.00004: High Quantum efficiency SWNTs Invited Speaker: |
Monday, March 15, 2010 9:12AM - 9:24AM |
A20.00005: Carbon Nanotube/CdSe Nanoparticle Hybrid Materials: Synthesis and Optical Properties Austin Akey, Chenguang Lu, Wei Wang, Irving Herman Carbon nanotubes present remarkable opportunities for construction of advanced nanomaterials with uniques properties, for use in sensors and optoelectronic device applications. Chemical attachment of nanoparticles to nanotubes has thus far resulted in low coverage; direct nucleation of particles on the tube sidewalls leads to a loss of control over particle size and monodispersity. We report the synthesis of novel heterostructures composed of single-walled carbon nanotubes and chemically attached, monodisperse cadmium selenide nanoparticles. The hybrid material is stable and resists aggregation; TEM and SEM characterization shows the nanotubes to be densely covered in nanoparticles. The nanoparticles used range in size from 3.5 to 6.0 nm in diameter, and exhibit strong quantum confinement. The hybrid materials are being investigated in the interest of finding new optical and/or electronic properties, which has lead to the observation of an anomalousmall Stokes shift in the photoluminescence. Results of ultrafast optical spectroscopy measurements on this phenomenon will be presented. [Preview Abstract] |
Monday, March 15, 2010 9:24AM - 9:36AM |
A20.00006: First-Principles Design of Conductance Switching in Functionalized Carbon Nanotubes Elise Li, Nicolas Poilvert, Nicola Marzari Functionalization of SWNT through addition reactions represents an effective method to engineer or manipulate carbon nanotubes. For armchair CNTs,the conductivity is often decreased by orders of magnitude by the introduction of monovalent functional groups which disrupt the conjugated $\pi$ network, whereas in [1+2] cycloadditions of carbenes or nitrenes, the sp$^2$ environment and therefore CNT metallicity can be recovered due to the sidewall bond breakage induced by the cyclopropane strain. In real systems, this bond cleavage depends heavily on the chirality and curvature of the tube, and the chemical nature of the addends. Here we explore the underlying mechanism of bond-cleavage chemistry in [1+2] cycloadditions on armchair carbon nanotubes using first-principles calculations. We find the high strain energy in cyclopropane moiety can be compensated by a through space $\pi$ orbital interaction between the addend and the CNT which lowers the HOMO energy significantly in closed-bond configuration. A bond opening or closing switch marked by large conductance change can therefore be devised by modulating the proximity of the addend $\pi$ system and the tube surface via optical or electrochemical control, which potentially has extensive applications in nanoscale devices. [Preview Abstract] |
Monday, March 15, 2010 9:36AM - 9:48AM |
A20.00007: Confirmation of the resonance energy transfer between Rare Earth-DNA-Carbon Nanotube complex Tetyana Ignatova, Hikmat Najafov, Slava V. Rotkin We used the resonance excitation spectroscopy combined with the time-resolved study of the excited states following the 20ps laser excitation to investigate the energy transfer between rare earth (RE) ions and single wall nanotubes (SWNT). Selectively excited Tb$^{3+}$ and Eu$^{3+}$ ions in water solution containing a high concentration of DNA-wrapped SWNT showed a small systematic energy transfer from RE to SWNT. The measured value of the resonant energy transfer is consistent with our theoretical estimation based on the spectral overlap of the corresponding absorption and emission spectra of energy acceptors and donors. We performed additional characterization to prove the ionization states of the RE ions using the high-resolution X-ray Photoelectron Spectroscopy. The observed shift of the 4d -- line of Tb is a signature of Tb$^{2+}$ state which corroborates our assumption of Tb chemical bonding with the DNA-SWNT complex. [Preview Abstract] |
Monday, March 15, 2010 9:48AM - 10:00AM |
A20.00008: Physisorption of Nucleic Acid Bases on Boron Nitride Nanotubes: A new class of Hybrid Nano-Bio Materials Saikat Mukhopadhyay, S. Gowtham, Ralph Scheicher, Ravindra Pandey, Shashi Karna We investigate the adsorption of the nucleic acid bases, adenine (A), guanine (G), cytosine (C), thymine (T) and uracil (U) on the outer wall of a high curvature semiconducting single-walled boron nitride nanotube (BNNT) by first principles density functional theory calculations. The calculated binding energy shows the order: G$>$A$\approx $C$\approx $T$\approx $U implying that the interaction strength of the (high-curvature) BNNT with the nucleobases, G being an exception, is nearly the same. A higher binding energy for the G-BNNT conjugate appears to result from a stronger hybridization of the molecular orbitals of G and BNNT, since the charge transfer involved in the physisorption process is insignificant. A smaller energy gap predicted for the G-BNNT conjugate relative to that of the pristine BNNT may be useful in application of this class of biofunctional materials to the design of the next generation sensing devices. [Preview Abstract] |
Monday, March 15, 2010 10:00AM - 10:12AM |
A20.00009: Growth and characterization of vertically aligned carbon nanotubes using PECVD Suman Neupane, Wenzhi Li Vertically aligned carbon nanotubes (CNTs) have been grown by using plasma enhanced chemical vapor deposition technique (PECVD). The density of the CNTs is controlled by the density of the nickel catalyst nanoparticles on silicon (Si) surface. Photolithography and nanosphere lithography have been employed to form a catalyst nanoparticle pattern on Si to grow periodic array of CNTS with controllable size and distribution. The electron emission properties of the CNT array have also been investigated. [Preview Abstract] |
Monday, March 15, 2010 10:12AM - 10:24AM |
A20.00010: In-Situ Growth of Carbon Nanotubes in a Microreactor Environment Silpa Kona, Cindy Harnett This work presents an approach to the in-situ growth of Carbon Nanotubes (CNTs) inside a micro scale environment using thermal chemical vapor deposition technique (Thermal CVD). Microreactors provide an ideal environment for exploration of extreme nanomaterial growth conditions, because they provide homogenous reactant temperature and concentrations, and the ability to work safely and economically at high temperatures and pressures over a broad range of flows. The study of Carbon Nanotube synthesis inside sub-mm channels and microfabricated reactors is of interest both fundamentally and for applications such as chromatographic channels. Carbon nanotubes (CNTs) are also excellent materials to be used as gas sensing elements as they exhibit changes in their electronic properties on being exposed to gases and are of interest in developing gas sensors operating at room temperature. Such micro scale CNT based sensing devices offer several practical advantages over the current sensors designs available, along with opening up avenues for a more efficient and better way of sensing gases. [Preview Abstract] |
Monday, March 15, 2010 10:24AM - 10:36AM |
A20.00011: Understanding the growth mechanism of carbon nanotubes via the ``cluster volume to surface area" model Sreekanth Mandati, Jens Kunstmann, Felix Boerrnert, Ronny Schoenfelder, Mark Ruemmeli, Kamal K. Kar, Gianaurelio Cuniberti The influence of mixed catalysts for the high yield production of carbon nanotubes (CNTs) has been studied systematically. Based on extensive experimental data a ``Catalyst Volume to Surface Area'' (CVSA) model was developed to understand the influence of the process parameters on the yield and CNT diameter distribution [1]. In our study, we present a refined version of the CVSA model developed by combining experiments and simulations. We discuss our current understanding of the growth mechanism and how the model might be used to increase CNT yields by using mixed catalysts.\\[4pt] [1] S. Tetali et al., ACS Nano (2009), DOI: 10.1021/nn9012548. [Preview Abstract] |
Monday, March 15, 2010 10:36AM - 10:48AM |
A20.00012: Potential of Mean Force between Aqueous Single Walled Carbon Nanotubes in Surfactant Solutions Alberto Striolo, Naga Rajesh Tummala, Brian H. Morrow Molecular dynamic simulations were conducted to calculate the effective potential of mean force (PMF) between two (6,6) SWNTs in the presence of aqueous surfactants at room conditions. The surfactants considered include sodium dodecyl sulfate (SDS) and flavin mononucleotide (FMN) surfactants. In the absence of surfactants our results show, as expected, a strongly attractive SWNT-SWNT PMF at short nanotube-nanotube separations. The presence of surfactants modulates the PMF profile. In the case of SDS we found that the potential of mean force does not depend significantly on the SDS surface density. The PMF shows a long-ranged weak repulsion between the SWNTs in the presence of the surfactants, coupled to strong attractive and repulsive regions when the SWNTs are close to each other. Unfortunately, the repulsive peak is not strong enough to prevent the aggregation of carbon nanotubes. Because FMN surfactants contain an aromatic isoalloxazine moiety and a chiral phosphate group, they couple more tightly with the SWNTs and yield a pronounced repulsive force between approaching SWNTs. Our results will help us identify the surfactant properties that allow us to manipulate nanotube-nanotube effective interactions. This is the key for designing nanotube-specific dispersing agents. [Preview Abstract] |
Monday, March 15, 2010 10:48AM - 11:00AM |
A20.00013: Electrical properties of electrospun polyaniline-polyethylene oxide nanofibrous membranes filled with single-walled carbon nanotubes Yung Woo Park, Bibekananda Sundaray, Ajeong Choi Highly conducting nanofibrous composite of well-oriented single-walled carbon nanotubes (SWNTs) in polyaniline (PANI) and polyethylene oxide (PEO) have been fabricated using electrospinning. The room temperature electrical conductivity show nearly four orders enhancement with highest (11.89wt {\%}) loading of SWNT, from their polymer blend counterpart. The temperature dependent conductivity results are fitted with the variable range hopping in addition to the fluctuation assisted tunneling conduction model. Results on coaxial electrospun polymer nanofibrous composites with SWNTs will be reported. [Preview Abstract] |
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