Bulletin of the American Physical Society
2005 APS March Meeting
Monday–Friday, March 21–25, 2005; Los Angeles, CA
Session P27: Focus Session: Carbon Nanotubes: Functionalization II |
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Sponsoring Units: DMP Chair: Keith Perkins, NRL Room: LACC 501C |
Wednesday, March 23, 2005 11:15AM - 11:51AM |
P27.00001: Electrochemical Sensing with Individual Single-Wall Carbon Nanotubes Invited Speaker: The transport properties of molecular electronic devices can be strongly modulated by immersion in a liquid electrolyte. For example, early investigations with single-wall carbon nanotubes (SWNTs) used the electrolyte as a "liquid gate." That is, the conductance of SWNTs in a field-effect-transistor configuration was tuned via an electrochemical potential applied to the electrolyte. This concept was also extended to sensor applications in which molecules impinging upon the SWNT surface cause a rearrangement of screening ions and a corresponding change of the device conductance. In these approaches, the coupling between the device and the electrolyte is solely electrostatic, and no charge is transferred across the liquid-device interface. Here we demonstrate that individual SWNTs can also be used as electrodes for electron transfer reactions, that is, electrochemical reactions in which electrons are exchanged between a SWNT and redox-active molecules in solution. The rate of electron transfer to SWNTs is observed to be very fast. It can nonetheless be resolved in dc transport measurements due to the high diffusive flux of redox molecules resulting from the nanometer diameter of SWNTs. Interestingly, metallic and semiconducting SWNTs yield similar current-voltage characteristics; we show that this behaviour is consistent with theories of electron transfer in which the electronic structure of the SWNTs is explicitly taken into account. Finally, we demonstrate that noble metals can be controllably and selectively electrodeposited from aqueous solution unto individual single-wall carbon nanotubes, opening new routes for the functionalization of SWNT devices. Work done with K. Besteman, H. A. Heering, I. Heller, J. Kong, J.-O Lee, B. M. Quinn, F.G.M. Wiertz, K. A. Williams and C. Dekker. [Preview Abstract] |
Wednesday, March 23, 2005 11:51AM - 12:03PM |
P27.00002: Quantitative Characterization of Defect Densities in Single-Walled Carbon Nanotubes Yuwei Fan, Nathan Emmott, Philip G. Collins Carbon nanotubes are often imagined to be pristine, defect-free objects, but different types of synthesis and processing are known to result in materials of different qualities. We have developed a method for the quantitative characterization of nanotube defect densities which can readily be used to compare nanotubes from different batches or processes. The method relies on the enhanced chemical reactivity of defect sites as compared to the graphene lattice. By tailoring the potentials used in electrochemical deposition, we selectively seed the growth of metal particles at reactive defect sites without decorating the bulk of a carbon nanotube. Because the metal particles can subsequently be grown 50 nm in diameter or larger, they are easily counted by low magnification SEM imaging, allowing for good statistics and wafer-scale characterization. We will demonstrate the results of this method on a batch of CVD-grown nanotubes and compare the measured defect density against nanotubes from other sources. This work has been supported by NSF-DMR. [Preview Abstract] |
Wednesday, March 23, 2005 12:03PM - 12:15PM |
P27.00003: Probing the Phonon-Assisted Relaxation Process in DNA-wrapped Carbon Nanotubes Using Polarization Dependent Optical Spectroscopy Shin Grace Chou, Andrew Welsh, Georgii Samsonidze, Jie Jiang, Riichiro Saito, Flavio Plentz, Ado Jorio, Marcos Pimenta, Ming Zheng, G. Bibiana Onoa, Ellen Semke, Gene Dresselhaus, Millie Dresselhaus, Anna Swan, Bennett Goldberg, Selim Unlu In this study, polarization-dependent spectroscopy is carried out on DNA-wrapped single walled nanotube hybrids, deposited onto a Sapphire substrate. By using a nanotube sample highly enriched in one specific (n,m) species and an intense light source, the various phonon-assisted excitonic relaxation processes, in addition to the commonly observed electronic interband transitions, can be separately identified and studied in detail. The phonon-assisted relaxation processes involving different phonon branches is emphasized in this study. The MIT authors acknowledge supports under the Dupont-MIT Alliance, NSF Grants DMR 04-05538. [Preview Abstract] |
Wednesday, March 23, 2005 12:15PM - 12:27PM |
P27.00004: Electrical transport characteristics of DNA-wrapped carbon nanotubes contacted to palladium and palladium oxide electrodes Frank Jones, Paul Dentinger, Francois Leonard, Alec Talin DNA-wrapped carbon nanotubes (DNA-CNT) have generated attention due the ability to disperse cleanly into solution, and by the possibility of sorting nanotubes according to size and conductivity. In order to learn more about the effects of DNA on the electrical transport characteristics of single wall carbon nanotubes, we fabricate and test a series of devices consisting of DNA-wrapped CNTs placed across gold, palladium, and palladium oxide electrodes. In addition, we look at how DNA functionalized CNTs react to presence of hydrogen, which has previously been shown to affect the conductivity of CNTs when in contact with palladium. [Preview Abstract] |
Wednesday, March 23, 2005 12:27PM - 12:39PM |
P27.00005: Detection of Pathogens Using AFM and SPR Ashok Vaseashta A priori detection of pathogens in food and water has become a subject of paramount importance. Several recent incidents have resulted in the government passing stringent regulations for tolerable amounts of contamination of food products. Identification and/or monitoring of bacterial contamination in food are critical. The conventional methods of pathogen detection require time-consuming steps to arrive disembark at meaningful measurement in a timely manner as the detection time exceeds the time in which perishable food recycles through the food chain distribution. The aim of this presentation is to outline surface plasmon resonance (SPR) and atomic force microscopy (AFM) as two methods for fast detect6ion of pathogens. Theoretical basis of SPR and experimental results of SPR and AFM on E. coli O157:H7 and prion are presented. [Preview Abstract] |
Wednesday, March 23, 2005 12:39PM - 12:51PM |
P27.00006: Anomalously soft dynamics of water in carbon nanotubes Alexander Kolesnikov, Chun-Keung Loong, Nicolas de Souza, Christian Burnham, Alexander Moravsky, Raouf Loutfy Quasi-one-dimensional water encapsulated inside single-wall carbon nanotubes, here referred to as nanotube-water, was studied by neutron diffraction, inelastic and quasielastic neutron scattering. The study reveals that nanotube-water is a new state of water manifested by weak hydrogen bonds, extended intermolecular water-water distances and very large amplitude of water molecules vibrations. Molecular dynamics simulations well describe the observed spectra and give a possible nanotube- water structure in a form of a square-ice sheet wrapped into a cylinder next to the inner carbon nanotube wall and a water chain in the interior. The soft dynamics of nanotube-water arises mainly from the drastic change in hydrogen-bond connectivity of the central water-chain. [Preview Abstract] |
Wednesday, March 23, 2005 12:51PM - 1:03PM |
P27.00007: Observations of Simple and Complex Liquid Transport in Carbon Nanotubes Byong Kim, Shashank Sinha, Haim Bau Taking advantage of the optical transparency of template grown, carbon nanotubes (CNTs) with 15 nm thick walls, we studied experimentally and theoretically the capillary filling, condensation, and evaporation of glycerin, ethylene glycol, and DI water inside CNTs under room conditions [1]. All the liquids readily filled the CNTs by the action of capillary forces. The capillary filling was also used to study the filling of the tube with nanoparticles. Liquid, laden with 40nm-diameter fluorescent beads, was brought into contact with a 300nm diameter CNT. The liquid and the particles' transport were observed, respectively, with optical and fluorescence microscopy. Finally, a nanotube-based device that enables us to conduct controlled experiments of liquid and macromolecule transport with an electron microscope is described. [1] B. M. Kim, S. Sinha, and H. H. Bau, Nano Letters, 4, 2203 (2004). [Preview Abstract] |
Wednesday, March 23, 2005 1:03PM - 1:15PM |
P27.00008: Microscopic and spectroscopic studies of the surfactant-assisted dispersion process of CoMoCAT carbon nanotubes in water Adelina Santos, Douglas Alves, Valdirene Peressinotto, Clascidia Furtado, Mauricio Souza, Flavio Plentz, Henrique Ribeiro, Ado Jorio, Marcos Pimenta, Daniel Resasco Recent Raman studies carried out on the precipitant and supernatant fractions after the centrifugation step of the surfactant-assisted dispersion of CoMoCAT carbon nanotubes in water have indicated an apparent selectivity of the dispersion process for some specific tubes. To get a better understanding of this phenomenon, we have combined SEM, Raman spectroscopy and photoluminescence techniques to investigate in details the suspendability properties of CoMoCAT samples in aqueous solutions of anionic surfactants under different experimental conditions. [Preview Abstract] |
Wednesday, March 23, 2005 1:15PM - 1:27PM |
P27.00009: Noncovalent functionalization of single-walled carbon nanotubes with water-soluble porphyrins Jinyu Chen, C. Patrick Collier We have employed water-soluble porphyrin molecules [meso-(tetrakis-4-sulfonatophenyl) porphine dihydrochloride] to solubilize individual single-walled carbon nanotubes (SWNTs), resulting in aqueous solutions that are stable for several weeks. The porphyrin-nanotube complexes have been characterized with absorption and fluorescence spectroscopy, and with AFM. We find that the porphyrin/SWNT interaction is specific to the free base form, and that this interaction increases the effective pKa value for the protonation of the free base. Under mildly acidic conditions (pH less than 5) nanotube-mediated J-aggregates form which are unstable in solution and result in precipitation of the nanotubes over the course of a few days. Porphyrin-coated SWNTs can be precisely aligned on hydrophilic poly(dimethylsiloxane) (PDMS) surfaces by combing SWNT solution along a desired direction and then transferred to silicon substrates by stamping. Parallel SWNT networks and SWNT crossbars have been fabricated in this manner. [Preview Abstract] |
Wednesday, March 23, 2005 1:27PM - 1:39PM |
P27.00010: A Generic Method towards Periodically Functionalized Carbon Nanotubes Lingyu Li, Wenwen Cai, Stephen Kodjie, Kishore Tenneti, Christopher Li As a consequence of their extraordinary physical properties and large application potential, carbon nanotubes (CNTs) have attracted the interest of scientists and engineers since their discovery in 1991. However, in order to effectively explore the remarkable properties and manipulate CNT, one essential step involves their functionalization. Periodical pattering CNT is an extremely challenging yet attractive field of research, and up to date, very few reported CNT functionalization methods have dedicated on how to achieve the periodical pattern on CNT. Our study of functionalization of CNTs via controlled polymer crystallization method has resulted in ``nano hybrid shish-kebab'' (NHSK), which is CNT periodically decorated with polymer lamellar crystals. The morphology and periodicity of NHSK can be controlled by tuning experimental parameters such as concentration of polymers and CNT, crystallization temperature and time. Preliminary results show that the periodicity varies from 20-70nm. Similar results were successfully obtained from both Nylon 6, 6 and PE with different kinds of CNTs, which can prove this is a generic method to periodically functionalize CNTs. [Preview Abstract] |
Wednesday, March 23, 2005 1:39PM - 1:51PM |
P27.00011: Single-walled carbon nanotubes in superacid: partly ordered H$_{2}$SO$_{4}$, nanotube-templated crystallization and evidence for protonation W. Zhou, P.A. Heiney, H. Fan, R.E. Smalley, J.E. Fischer Liquid anhydrous sulfuric acid forms a partly ordered structure in the presence of single-walled carbon nanotubes (SWNTs). Room temperature x-ray scattering from well-aligned nanotube fibers immersed in acid shows that H$_{2}$SO$_{4}$ molecules align along the nanotube axis and form cylindrical ``shells'' wrapped around nanotubes and ropes. Differential scanning calorimetry of SWNT-acid suspensions exhibits concentration-dependent supercooling/melting behavior, confirming that the partly ordered molecules are a new phase. Temperature-dependent x-ray scattering further shows that crystallization of the bulk-like acid surrounding the structured acid shells is templated by the aligned SWNTs, while the structured shells remain partly ordered, at least for temperatures from 100K to 500K. The (2 0 0) or (-2 0 2) planes of the templated H$_{2}$SO$_{4}$ crystallites are parallel to the nanotube axes. This provides solid evidence for the direct protonation of SWNT since these planes display exposed hydrogen bonds. [Preview Abstract] |
Wednesday, March 23, 2005 1:51PM - 2:03PM |
P27.00012: Structural, thermodynamic and transport properties of functionalized carbon nanotubes from first-principles Young-Su Lee, Nicola Marzari We have studied the structural, thermodynamic and transport properties of carbon nanotubes functionalized via cycloaddition of nitrenes and carbenes, using our recently-developed band-structure and quantum conductance method based on maximally-localized Wannier functions. This approach allows us to study the effects of chemical functionalization on the transport properties of nanostructures containing thousands of atoms, while maintaining full ab-initio accuracy. We find that the stability of the two distinct sites of attachment on the sidewalls of achiral CNTs is strongly affected by diameter, due to the competition between elastic and chemical forces. A subtle interplay of electronic effects between $sp^2$ and $sp^3$ hybridization results in very significant differences for the transport properties of metallic nanotubes. [Preview Abstract] |
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