Bulletin of the American Physical Society
2006 APS March Meeting
Monday–Friday, March 13–17, 2006; Baltimore, MD
Session Z18: Focus Session: Carbon Nanotubes: Double Wall Nanotubes, Sheets and Chains |
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Sponsoring Units: DMP Chair: Feng Wang, University of California, Berkeley Room: Baltimore Convention Center 315 |
Friday, March 17, 2006 11:15AM - 11:51AM |
Z18.00001: Tube-tube interaction and high curvature effects in double wall carbon nanotubes Invited Speaker: Recent results will be reported on the consequences of the interaction between peapod grown inner shell carbon nanotubes and the corresponding outer shell tubes in double wall carbon nanotubes (DWCNTs). The results were obtained from resonance Raman experiments on natural and $^{13}$C isotope substituted nanotubes, from time resolved NMR experiments and from calculations which include tube-tube interaction and high curvature effects of the inner tubes. The Raman analysis of the radial breathing mode of the inner tubes exhibits extremely narrow line widths which indicates unusual long phonon life times. It also confirms family behaviour of the tubes and the large number of observed lines is a consequence of pair spectrum response between inner shell and outer shell tube pairs. The response from the RBM is used to demonstrate reversible filling and release of the fullerenes from the tubes. Measurements of the longitudinal relaxation time T$_{1}$ in NMR experiments from $^{13}$C substituted inner tubes reveal a Korringa behaviour for temperatures above 150 K. This indicates a metallic character of the inner tubes. Below 20 K the metallicity is lost and a gap of about 4 meV opens up. The properties of the inner tubes will be discussed in the frame of a inner shell-outer shell orbital hybridization and curvature enhanced electron-phonon interaction. [Preview Abstract] |
Friday, March 17, 2006 11:51AM - 12:03PM |
Z18.00002: Density Functional Calculations of the $^{13}$C NMR Chemical Shifts in Single-Walled Carbon Nanotubes Jochen Autschbach, Eva Zurek Nuclear Magnetic Resonance (NMR) chemical shifts of single--walled carbon nanotubes were computed for capped finite--sized tube fragments and for infinite--length tubes. Molecular density functional calculations using atom--centered basis sets have been performed for the electronic structure and $^{13}$C NMR chemical shifts of (5,0), (9,0) and (10,0) single-walled carbon nanotube (SWNT) fragments. For the (9,0) tube, a C$_{30}$-capped fragment appeared to be a more suitable model to represent an infinite tube then a fragment capped with hydrogens. Thus, the study of the finite (5,0) and (10,0) tubes were restricted to the systems capped with carbon hemispheres. The chemical shift for the (9,0) system [1] is in good agreement with experimental data that were recently obtained from a solution of functionalized nanotubes. Further, we have calculated the $^{13}$C chemical shift for a number of infinite small-radius SWNTs using a plane--wave approach. Here, the effect of inter-tube interactions upon the chemical shift was also considered. The results will be compared with those obtained for the finite systems. We believe that our computations may be useful in determining new experimental methods which rely upon NMR to characterize a nanotube sample.\\ \noindent [1] E. Zurek, J. Autschbach, \textit{J. Am. Chem. Soc.} {\bf 126}, 13079 (2004). [Preview Abstract] |
Friday, March 17, 2006 12:03PM - 12:15PM |
Z18.00003: Comparative Raman spectroscopy study of Single-Wall and Double-Wall carbon nanotube systems doped with $H_2SO_4$ Eduardo Barros, Antonio G. Souza Filho, Yoong-Ahm Kim, Hiroyuki Muramatsu, Takuya hayashi, Morinobu Endo, Mildred Dresselhaus In this work, we performed Raman experiments on a mixture of Single-wall and Double-wall carbon nanotubes for different relative concentrations and using different laser energies. Two sets of samples were analyized, one which was exposed to $H_2SO_4$ for 5$s$ and one which is pristine. The $H_2SO_4$ is known to act as an acceptor for the electrons of graphitic materials. The effect of the hole doping on the vibrational and electronic properties of the double and single-wall carbon nanotubes is probed using Resonant Raman scattering with different excitation energies probing different nanotubes. The inner and outer walls of double-wall nanotubes can also be studied at the same time for selected excitation energies. A detailed analysis of the charge transfer in single wall and double wall nanotubes and its effects on the nanotube properties is obtained. [Preview Abstract] |
Friday, March 17, 2006 12:15PM - 12:27PM |
Z18.00004: Spectroscopy of Functionalized Double-Walled Carbon Nanotubes J. Shaver, J. Kono, F. Liang, W.E. Billups, R.H. Hauge, E. Flahaut Double walled nanotubes are of recent interest for spectroscopic study partly due to the protected nature of the inner tubes. Functionalization of single walled nanotubes has been used to increase solubility, though this comes at the expense of disrupting the electronic properties. We present spectroscopy of DWNTs functionalized with various organic and inorganic compounds. Photoluminescence, Raman, and coherent phonon oscillations are utilized to determine the effect of sidewall modification of outer tubes on the DWNT spectra. [Preview Abstract] |
Friday, March 17, 2006 12:27PM - 12:39PM |
Z18.00005: Defects in single and double wall carbon nanotubes Jian-Min Zuo, T.K. Kim We show that single and double wall carbon nanotubes grown by catalytic chemical vapor deposition can change its chirality and create junctions along the tube direction. These tubes often appear straight (perfect) in electron images. The change in structure is often subtle and only detectable by electron diffraction. The experimental evidence of defects, structure determination and consequence on tube transport properties will be presented and discussed. [Preview Abstract] |
Friday, March 17, 2006 12:39PM - 12:51PM |
Z18.00006: Resonant Raman scattering in Br2-adsorbed double wall carbon nanotubes Antonio Souza Filho, Morinobu Endo, Hiroyuki Muramatsu, Yoong A. Kim, Takuya Hayashi, N. Akuzawa, Riichiro Saito, Mildred S. Dresselhaus The vibrational and electronic properties of Br2-adsorbed double-wall carbon nanotubes (DWNTs) were investigated by resonance Raman scattering. We have found that Br2 molecules interact with the DWNTs and their intercalation characteristics are completely reversible upon thermal annealing. Upshifts in the Raman frequencies for the tangential modes and depression of their Raman intensities indicate that electrons are transferred from the nanotubes to the Br2 molecules. Metallic nanotubes are specially sensitive to the adsorption of Br2 molecules, even when they are the inner tubes of DWNTs. The vibrational spectra of the bromine dopant also provide information about the intercalation process. [Preview Abstract] |
Friday, March 17, 2006 12:51PM - 1:03PM |
Z18.00007: Growth transition from single wall- to double walled- carbon nanotubes by using acetylene gas Vijaya Kayastha, Yoke Khin Yap Based on a growth model that we have proposed for multiwalled carbon nanotubes (CNTs) [1, 2], we found that similar mechanism is applied for the growth of single wall- and double walled- CNTs by acetylene gas. This model combines disociative adsorption of acetylene molecules on Fe catalyst and the vapor-liquid-solid mechanism. Basically, the growth is the consequence of optimization of decomposition rate of acetylene molecules as referred to the diffusion rate and segregation rate of carbon into and from the catalyst. For the growth of single wall- and double walled- CNTs, catalytic film consists of layers of aluminum, iron, and molybdenum were used. We found that samples grown at $\sim $600-700 $^{o}$C contained more than 80{\%} double walled CNTs with diameters in the range 3-5nm and length 15 $\mu $m. These CNTs are vertically aligned on substrates. As the temperature increased to 1000 $^{o}$C the growth of single wall CNTs are detected. [1]. Kayastha et al., APL 86, 253105 (2005), [2] Kayastha et al., APL 85, 3265 (2004). [Preview Abstract] |
Friday, March 17, 2006 1:03PM - 1:15PM |
Z18.00008: Electronic structure of a linear carbon-atom chain inside single-walled carbon nanotubes Romeo de Coss, Alejandro Tapia, Cesar Cab, Jorge Medina, Gabriel Canto, Cesar Acosta Recently has been reported a new type of one-dimensional carbon structures. Carbon nanowires formed by a linear carbon-atom chain inside an armchair (5,5) carbon nanotube has been observed using high-resolution transmission electron microscopy. In the present work we have studied the electronic structure of a linear carbon-atom chain inside the (5,5) and (8,0) single-walled carbon nanotubes (SWCN) using the Density Functional Theory. The calculations where performed with the pseudopotentials LCAO method (SIESTA code) and the Generalized Gradient Approximation (GGA) for the exchange-correlation potential. We have analyzed the band structure, the local density of states (LDOS), and the local orbital population. We find charge transfer from the nanotube to the linear chain in both systems chain@(5,5) and chain@(8,0). However, the electronic character of the chain and nanotube sub-systems in chain@SWCN is the same that in the corresponding isolated chain or SWCN systems. [Preview Abstract] |
Friday, March 17, 2006 1:15PM - 1:27PM |
Z18.00009: Optical Anisotropy of Aligned Single Wall Carbon Nanotubes Jeffrey A. Fagan, Barry J. Bauer, Idan Mandelbaum, Matthew L. Becker, Erik K. Hobbie The optical properties of single wall carbon nanotubes (SWCNTs) are of significant importance for a variety of applications, particularly for fractions containing well defined tube lengths and chiralities. In this work, stable suspensions of DNA wrapped SWCNTs were mechanically aligned by dispersing them in amorphous polymer films, and their intrinsic optical anisotropy measured through a combination of polarized light spectroscopy, polarized Raman spectroscopy, and small-angle neutron scattering (SANS). Conventional measures of nematic alignment in the stretched polymer films typically varied from 0.7 to 0.9. The quality of the nanotube dispersion within the centimeter scale polymer film samples was also directly investigated by means of atomic force and electron microscopy. We obtain the intrinsic optical anisotropy of the SWCNTs over a broad range of photon energies, with a number of well-resolved absorption peaks corresponding to specific SWCNT chiralities. [Preview Abstract] |
Friday, March 17, 2006 1:27PM - 1:39PM |
Z18.00010: Boron Nanotubes and Boron Sheets -- New Perspectives for Nanotechnology Jens Kunstmann, Alexander Quandt We report about a recent ab initio study of boron nanotubes (BNTs). The latter were first predicted by theory, and have recently been synthesized experimentally. To understand the basic properties of BNTs, we have derived a structure model for an extended boron sheet (i.e. a boron analogue of a single graphene sheet) as a possible structural precursor of boron nanotubes. This sheet has a puckered structure, high stiffness, and anisotropic bonding properties. Puckering turns out to be the key mechanism for stabilizing sp sigma bonds lying along the armchair direction of the sheet. The BNTs have puckered surfaces as well, and their chiral angles are defined in a range from 0 to 90 degree. We show that all ideal boron nanotubes are metallic, irrespective of their radii and chiral angles, and discuss the possible existence of helical currents in chiral BNTs. Furthermore we show that strain energies of BNTs depend on their radii AND on their chiral angles. This unique property could be the basis of a new structure control mechanism in nanotechnology that permits to make nanotubes of a specified type, only. Zigzag nanotubes for example seem to have very little strain energy, if any. Therefore they should be highly susceptible to structural collapses, and might not exist at all. [Preview Abstract] |
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