Bulletin of the American Physical Society
2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009; Pittsburgh, Pennsylvania
Session H24: Focus Session: Chemical Modification of Nanotubes |
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Sponsoring Units: DCMP Chair: Traian Dumitrica, University of Minnesota Room: 326 |
Tuesday, March 17, 2009 8:00AM - 8:36AM |
H24.00001: Single Molecule Detection in Living Biological Cells using Carbon Nanotube Optical Probes Invited Speaker: Nanoscale sensing elements offer promise for single molecule analyte detection in physically or biologically constrained environments. Molecular adsorption can be amplified via modulation of sharp singularities in the electronic density of states that arise from 1D quantum confinement [1]. Single-walled carbon nanotubes (SWNT), as single molecule optical sensors [2-3], offer unique advantages such as photostable near-infrared (n-IR) emission for prolonged detection through biological media, single-molecule sensitivity and, nearly orthogonal optical modes for signal transduction that can be used to identify distinct classes of analytes. Selective binding to the SWNT surface is difficult to engineer [4]. In this lecture, we will briefly review the immerging field of fluorescent diagnostics using band gap emission from SWNT. In recent work, we demonstrate that even a single pair of SWNT provides at least four optical modes that can be modulated to uniquely fingerprint chemical agents by the degree to which they alter either the emission band intensity or wavelength. We validate this identification method in vitro by demonstrating detection and identification of six genotoxic analytes, including chemotherapeutic drugs and reactive oxygen species (ROS), which are spectroscopically differentiated into four distinct classes. We also demonstrate single-molecule sensitivity in detecting hydrogen peroxide, one of the most common genotoxins and an important cellular signal. Finally, we employ our sensing and fingerprinting method of these analytes in real time within live 3T3 cells, demonstrating the first multiplexed optical detection from a nanoscale biosensor and the first label-free tool to optically discriminate between genotoxins. We will also discuss our recent efforts to fabricate biomedical sensors for real time detection of glucose and other important physiologically relevant analytes in-vivo. The response of embedded SWNT in a swellable hydrogel construct to osmotic pressure gradients will be discussed, as well as its potential as a unique transduction mechanism for a new class of implantable sensors. \\[4pt] [1] Saito, R., Dresselhaus, G. {\&} Dresselhaus, M. S. \textit{Physical Properties of Carbon Nanotubes }(Imperial College Press, London, 1998). \\[0pt] [2] Barone, P. W., Baik, S., Heller, D. A. {\&} Strano, M. S. Near-Infrared Optical Sensors Based on Single-Walled Carbon Nanotubes. \textit{Nature Materials }\textbf{4}, 86-92 (2005). \\[0pt] [3] Jeng, E. S., Moll, A. E., Roy, A. C., Gastala, J. B. {\&} Strano, M. S. Detection of DNA hybridization using the near infrared band-gap fluorescence of single-walled carbon nanotubes. \textit{Nano Letters }\textbf{6}, 371-375 (2006). \\[0pt] [4] Heller, D. A. et al. Optical detection of DNA conformational polymorphism on single-walled carbon nanotubes. \textit{Science }\textbf{311}, 508-511 (2006). [Preview Abstract] |
Tuesday, March 17, 2009 8:36AM - 8:48AM |
H24.00002: Argon and Krypton Adsorption Isotherms on Single Carbon Nanotube Devices Zenghui Wang, Peter Morse, Jiang Wei, Oscar Vilches, David Cobden We have fabricated mass balances each consisting of an individual single-walled carbon nanotube suspended across a micron-sized trench in an oxidized Si wafer. The vibrational resonance frequency of a nanotube, which is in the range 50-500 MHz, is determined by monitoring the current through it while applying an electrostatic driving signal. By tracking changes in the resonance frequency we have measured isotherms of adsorbed mass vs vapor pressure for Ar ot Kr at liquid nitrogen temperatures. The sensitivity of the balances corresponds to just a few atoms. We have compared the monolayer mass shifts due to Ar and Kr, and measured a family of isotherms of Ar below 77 K. From the latter we calculated the isosteric heat of adsorption on the nanotube surface, which is found to be lower than that of Ar on basal plane graphite and only slightly larger than the latent heat of sublimation of bulk Ar at these temperatures. In one device we observed a phase transition in the adsorbed Ar near monolayer completion. In another device, which probably consists of two nanotubes joined in parallel, we observed enhanced adsorption at lower coverages which may be in the groove between the two nanotubes. This work is supported by the NSF, grant number 0606078. [Preview Abstract] |
Tuesday, March 17, 2009 8:48AM - 9:00AM |
H24.00003: Resonance Raman study of Polyynes encapsulated in single-wall Carbon Nanotubes with different diameters. L.G. Moura, L.M. Malard, D. Nishide, Y. Achiba, H. Shinohara, M.A. Pimenta Polyynes are one of the simplest linear carbon chains and they have been recently encapsulated in single-wall carbon nanotubes. The stability of encapsulated polyynes opens a way to investigate experimentally these sp-hydrized carbon structures and to study of electronic correlation effects in 1D systems with potential applications in nanoelectronics. In this work we present a resonance Raman study of C$_{10}$H$_2$ and C$_{12}$H$_2$ polyynes inside single-wall carbon nanotubes with different diameters, using many different laser energies in visible range. We show that the observed optical resonance energies of the polyynes depends on the diameter of nanotubes, the maximum of the resonances decreasing with increasing diameter of the nanotubes. Moreover, the resonance energy is generally lower for C$_{12}$H$_2$ than C$_{10}$H$_2$. We have also observed a red-shift and strong changes in the shape of Raman G band of the metallic nanotubes when they encapsulate the polyynes, and these results were interpreted in terms charge transfer between these two systems and its effect on the electron-phonon coupling of the nanotubes. We have also observed that the interaction between polyynes and nanotubes is stronger for nanotubes with small diameters. [Preview Abstract] |
Tuesday, March 17, 2009 9:00AM - 9:12AM |
H24.00004: Alkanes adsorbed on carbon nanotubes: specific surface areas and isothermal adsorption kinetics Dinesh Rawat, Toyohisa Furuhashi, Aldo Migone, Jose Antonio Ramirez-Pastor, Federico Roma, Jose Luis Riccardo We measured the specific surface area of single-wall carbon nanotube substrates using methane, ethane, propane and butane adsorption isotherms. The monolayer capacity for each gas was obtained from the BET equation. We found that the specific surface areas measured decrease as the length of the alkanes used to measure them increases. This trend may be explained by the fact that an increasing fraction of the substrate's surface should be left uncovered as longer adsorbates are used. We also studied the isothermal adsorption kinetics of these alkanes. We monitored the evolution of the gas pressure with time, from the instant at which the gas is added to the sample cell up until the time at which equilibrium is reached. Equilibration times for comparable fractional coverages increase with increasing alkane length. While the equilibration times decrease with increasing fractional coverage for methane and ethane, they increase with increasing coverage for propane and butane (this increase may be due to reorientation of the adsorbed molecules in the film). [Preview Abstract] |
Tuesday, March 17, 2009 9:12AM - 9:24AM |
H24.00005: Study of propane films adsorbed on Purified HiPco Carbon Nanotubes Toyohisa Furuhashi, Dinesh Rawat, Aldo Migone We investigated the adsorption characteristics of propane on purified HiPco single-walled carbon nanotubes for coverages limited to the first layer. We found two prominent substeps present in the monolayer; this suggests the presence of at least two distinct groups of binding energy sites in the substrate. The results are similar to those that we have found for ethane, but different from those we measured for butane, on the same substrate. We compare and contrast the characteristics of the isotherms for these three alkanes. A high-binding-energy (low-pressure) adsorption isotherm substep is present for all three alkanes. By contrast, the high- pressure substep (corresponding to adsorption on the outer surface area of the nanotubes bundles) shows a gradual smearing with increasing alkane length; this feature is barely resolvable for butane. We also found a gradual increase in the binding energy of alkane molecules with the increasing carbon chain length. This result confirms findings of simulation results for similar systems. [Preview Abstract] |
Tuesday, March 17, 2009 9:24AM - 9:36AM |
H24.00006: Adsorption of Nitro Aromatics on Single-Walled Carbon Nanotubes Erik Alldredge, Stefan Badescu, Thomas Reinecke, Navdeep Bajwa, F. Keith Perkins, Eric Snow Recent experiments with arrays of carbon nanotubes reveal a strong conductivity response after exposure to aromatic molecules containing nitro functional groups, such as nitrobenzene and trinitrotoluene. The detection of these compounds is of particular interest in the use of nanotube arrays as chemical sensors. To develop an understanding of the microscopic mechanisms involved, we perform detailed \textit{ab initio} calculations of adsorption geometries, charge configurations, and vibration spectra for these compounds on pristine armchair and zigzag nanotubes. We use density functional theory with localized orbitals in a cluster approach and the M05-2X functional that is appropriate for the weak interactions of physisorption for these systems. We find a strong increase in adsorption energy with the addition of each nitro group to a molecule (around 100 meV) and a gradual increase with nanotube size, in agreement with preliminary experimental results. For most of these compounds, little charge transfer ($<$ 0.1 $e)$ occurs. Finally, these calculations are compared with results for the adsorption at oxidation defects. [Preview Abstract] |
Tuesday, March 17, 2009 9:36AM - 9:48AM |
H24.00007: Transparent Boron-Doped Nanotube Films Xiaoming Liu, Hugo Romero, Humberto Gutierrez, Peter Eklund We report results of FTIR transmission and temperature-dependent resistance measurements on transparent thin films of bundled single-walled carbon nanotubes exposed to B2O3 at 1000C. This reaction is proposed to B-dope the films. Doping is observed to lower the T=300 K dc sheet resistance by a factor of five without changing the optical transmittance in the visible range and suggests that boron-doped SWNT provide a better approach to transparent electrodes. The optical transmission (T=300K) of SWNT and B- doped SWNT films measured in the range 50-7000 cm-1 show that the doped films have a greater optical density in the mid to far IR, consistent with the B-doping creating new free carriers. This optical result shows that the DC conductivity of the doped tubes is indeed higher, with the interpretation not being entangled with changes in the tube-tube contact resistance within the film, as would be the case in a dc conductivity measurement. Also the dc resistance of both B-doped and annealed SWNT films were measured over 10$<$T$<$300K. The data showed for the doped films the metallic term (linear in T) is $\sim $10 times greater than for the annealed and undoped films. Work supported by NSF NIRT ECS 06-09243. [Preview Abstract] |
Tuesday, March 17, 2009 9:48AM - 10:00AM |
H24.00008: Kinetic selectivity effects of binary mixtures on nanotube bundles: Internal and external adsorption Seyoum Tsige, Mercedes Calbi, Jared Burde We investigate kinetic selectivity effects that take place during the adsorption of a binary mixture inside a nanotube and on the external surface of a bundle. By using a kinetic Monte Carlo Scheme we allow adsorption on sites with different binding energy (external surface) and we restrict adsorption/desorption only to the end sites in the case of the internal adsorption. In both cases, we analyze the appearance of an overshoot in the fractional coverage of the weaker species (before equilibrium) observed previously for a single, homogeneous, one-dimensional chain. \newline [Preview Abstract] |
Tuesday, March 17, 2009 10:00AM - 10:12AM |
H24.00009: Temperature Programmed Desorption on Carbon Nanotube Bundles: a Computer Simulation study Nayeli Zuniga, Mercedes Calbi, Jared Burde We present a study of gas desorption on external surfaces of carbon nanotube bundles by means of a Kinetic Monte Carlo scheme. Starting with an initial coverage, we follow the amount of gas desorbed as the temperature increases for different values of initially occupied sites and initial temperature of the sample. We analyze the spectrum obtained in terms of the different binding energies of the adsorption sites. We also compare our results with some available experimental measurements on nanotube bundles and other nanostructures. [Preview Abstract] |
Tuesday, March 17, 2009 10:12AM - 10:24AM |
H24.00010: Scattering Process of Gas Molecules on Vertically Aligned Single-Walled Carbon Nanotubes Ikuya Kinefuchi, Yushi Harada, Junpei Kawasaki, Kei Ishikawa, Junichiro Shiomi, Shu Takagi, Shigeo Maruyama, Yoichiro Matsumoto Scattering process of gas molecules on quartz surfaces covered with vertically aligned single-walled carbon nanotubes (VA-SWNTs) was investigated using the molecular beam technique. We found that the surface modification with VA-SWNT films significantly enhances the energy transfer between gas molecules and surfaces at room temperature and makes the energy accommodation coefficient of helium, which tends to be small even for contaminated surfaces because of the large mass mismatch between helium and surface atom, close to unity. Our results demonstrate a potential application of VA-SWNTs as nanoscale fin structures to enhance heat transfer between gas phase and solid surfaces. As the surface temperature increases, however, the energy accommodation becomes less efficient since the small adsorption energy reduces the trapping probability of helium on carbon nanotube (CNT) bundles. The weak dependence of the accommodation coefficient on the film thickness suggests that gas molecules penetrate into the films because of their high porosity and suffer more than one collision with CNT bundles. [Preview Abstract] |
Tuesday, March 17, 2009 10:24AM - 10:36AM |
H24.00011: Carbon Nanotube CdSe Nanoparticle Hybrid Materials: Synthesis and Optical Properties Austin Akey, Chenguang Lu, Wei Want, Irving Herman Carbon nanotubes present remarkable opportunities for the construction of nanomaterials with unique properties, and for use in sensors and optoelectronic device applications. Chemical attachment of nanoparticles to nanotubes has thus far resulted in low loading; 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. Pyridine is used to strip the ligand shell from the nanoparticles, which are then bound to SWNTs in suspension. The resulting hybrid material is stable and resists aggregation; TEM and SEM characterization shows the nanotubes to be densely covered with nanoparticles. The nanoparticles used range in size from 3.5 to 6.0 nm in diameter, and exhibit strong quantum confinement. Also synthesized were hybrids of carbon nanotubes with core-shell CdSe/ZnS nanoparticles and with CdSe nanorods. The absorption and photoluminescence properties of the hybrid materials are also presented. [Preview Abstract] |
Tuesday, March 17, 2009 10:36AM - 10:48AM |
H24.00012: Electrochemical and Optical Characterization of Metal-Decorated Carbon Nanotubes Tatyana Sheps, Vaikunth R. Khalap, Alexander A. Kane, Philip G. Collins, Hyunmin Kim, Eric O. Potma Hybrid electrodes combining carbon nanotubes with metal and metal oxide particles are promising for many catalytic applications including energy conversion and energy storage. Understanding the chemical interactions between the nanotube substrate and the catalytic nanopaticle is crucial for optimizing these types of electrodes. Here, we describe techniques for interrogating the metal-nanotube interface on the single-molecule level, using isolated single-walled nanotubes (SWNTs) decorated by single metal particles as the most basic, representative element of a bulk hybrid electrode. The resulting composite and its chemical interface is studied by two complementary techniques, electrochemical voltammetry and Raman spectroscopy. Results comparing the electrochemical behavior with the surface chemistry are presented. [Preview Abstract] |
Tuesday, March 17, 2009 10:48AM - 11:00AM |
H24.00013: Electrochemistry of single-walled carbon nanotubes (SWCNTs) supporting single palladium nanoparticles Vaikunth R. Khalap, Tatyana Sheps, Alexander A. Kane, Philip G. Collins The capabilities to produce, chemically tailor, and label point defects [1-3] provide a versatile toolkit for studying complex model systems based on SWNCTs and catalytic metals. Here, we describe experiments on individual SWCNTs with and without point defects and Pd nanoparticles. In this single particle limit, the effects of a defect on a supported Pd nanoparticle can be very clearly discerned. Electrochemical voltammetry reveals an important interplay between the Pd catalytic activity and the defect termination chemistry. In addition, conductivity measurements reveal an enormous response to H2 gas, making the devices competitive commercial H2 sensors. This research is partly supported by NSF (CBET-0729630) and a GAANN fellowship (VRK). [1] B. Goldsmith et al, \textit{Science} \textbf{315} 77 (2007) [2] J. Coroneus et al, \textit{ChemPhysChem} \textbf{9 }1053 (2008) [3] Y. Fan et al, \textit{Nature Materials} \textbf{4} 906 (2005) [Preview Abstract] |
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