Bulletin of the American Physical Society
2008 APS March Meeting
Volume 53, Number 2
Monday–Friday, March 10–14, 2008; New Orleans, Louisiana
Session B30: Focus Session: Carbon Nanotubes and Related Materials III: Synthesis |
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Sponsoring Units: DMP Chair: Chun Ning Lau, University of California, Riverside Room: Morial Convention Center 222 |
Monday, March 10, 2008 11:15AM - 11:51AM |
B30.00001: Novel Functions in Double Walled Carbon Nanotubes Invited Speaker: Nano-sized carbon nanotubes with hollow core were observed when hydrocarbons were catalytically decomposed in the existence of nano-sized catalyst such as iron at higher temperature. Up to now, this catalytic chemical vapor deposition (CCVD) method has been utilized as the most powerful technique for the selective and large-scale production of carbon nanotubes. Since large amount of multi-walled carbon nanotubes (up to 250 ton/year) are available, much efforts has intensified on the development of their industrial usages. A recent hot topic has focused on the synthesis of double walled carbon nanotubes (DWNTs) because these tubes are more thermally and chemically stable when compared to single wall carbon nanotubes (SWNTs); they also exhibiting the 1D character of a quantum wire. In addition, DWNTs could also be used in the fabrication of electron field emitter and nano-composites. Very recently, we have successfully prepared highly pure and crystalline DWNTs by the combination of the CCVD and the subsequent oxidative purification process. In this talk, I will describe the preferential growth of DWNTs over SWNT or MWNTs, their structural characterizations using various analytic techniques and their possible applications. We found that these coaxial tubes consist of two relatively round, small and homogeneous-sized (below 2 nm in the outer shell) concentric tubules and are packed in a hexagonal array. Then, I will discuss a novel and stable structure consisting of flattened tubules containing two SWNTs via the coalescence of two adjacent tubes, chemical doping effect as a tunable way of electronic structure of DWNTs, and formation of atomic scale metal wires in the hollow core of DWNTs. Finally, I will report their transport properties as well as their performance in field effect transistors as compared with those of SWNTs. Therefore, in the near future, it may be possible that DWNTs replace SWNTs in specific carbon nanotube devices used today. [Preview Abstract] |
Monday, March 10, 2008 11:51AM - 12:03PM |
B30.00002: Electron Spin Resonance in Single-Walled Carbon Nanotubes W. D. Rice, J. Kono We have performed electron spin resonance (ESR) measurements on various types of single-walled carbon nanotube (SWNT) samples. As catalyst particles were chemically removed from the SWNTs, the linewidth of the conduction electron spin resonance (CESR) signal became smaller, reaching 43 G at 5 K for acid-purified HiPco SWNTs. For every type of SWNT tested, a ferromagnetic resonance (FMR) signal was observed; we show that this is attributed to catalyst particles. The $g$-factor for the CESR signal was slightly shifted from the free electron value; as purity increased, the resonance moved closer to $g$ = 2.003. The conduction electron signal increased as the temperature was decreased, indicating that we are observing both Pauli and Curie paramagnetism. No spin gap for either laser-oven acid-purified or HiPco acid-purified SWNTs was seen when the temperature was taken from 295 K to 5 K. In addition, the FMR signal decreased as the temperature was decreased. SWNTs suspended in aqueous surfactant solutions were also measured. As a function of purity, the FMR signal was substantially decreased. We show that as a function of metal catalyst content, the ESR lineshape of SWNTs changes significantly. [Preview Abstract] |
Monday, March 10, 2008 12:03PM - 12:15PM |
B30.00003: IPS verification of the integrity of CNTs walls after purification. Patricio Haberle, Samuel Hevia, Rodrigo Segura, Manish Chhowalla We report results from measurements by inverse photoemission spectroscopy (IPS) from single wall carbon nanotubes (SWCNTs). We have used this technique to verify the influence of strong purification procedures on the integrity of the tube walls. The purification included an HNO$_{3}$ immersion in a solution for 3 hours, before a 400 \r{ }C annealing. Even though the thin layers of CNTs present a high conductivity, the treated tubes trap the electronic charges from the IPS electron beam. A possible explanation for this apparent inconsistency is that the acid treatment induces the formation of charge traps in the outside tubes of the bundles. RAMAN spectroscopy from the same samples, with and with out the acid treatment, show almost no variations. The IPS signal is extremely sensitive to the conditions of the tube's external wall, while Raman spectroscopy can detect signals form inner tubes. Using IPS may then prove useful to determine electronic quality of CNTs arrays. [Preview Abstract] |
Monday, March 10, 2008 12:15PM - 12:27PM |
B30.00004: High surface area, porous nanotube film supercapacitors. Rajib K. Das, Ryan M. Walczak, John R. Reynolds, Andrew G. Rinzler Recently, I-H Kim \textit{et al.} [a] described high performance supercapacitors based on ruthenium oxide electrodeposited on multi-walled carbon nanotube mats. We recently developed a method for producing enhanced porosity single wall carbon nanotube (SWNT) films based on co-filtration of sacrificial nano-spheres and the SWNTs in the filtration based film fabrication. Here we follow Kim \textit{et al.} in electrodepositing ruthenium oxide onto the porous SWNT films. Performance of the devices will be discussed. a. I-H Kim, J-H Kim, Y-H Lee and K-B Kim J. Electrochem. Soc. 152, A2170 (2005) [Preview Abstract] |
Monday, March 10, 2008 12:27PM - 12:39PM |
B30.00005: Controlled Fabrication of Single Electron Transistors from Single-Walled Carbon Nanotubes Paul Stokes, Saiful I. Khondaker Single-walled carbon nanotubes (SWNTs) are considered to be an ideal material for quantum electronic applications such as single electron transistors (SETs). However, fabrication of SET based devices is still in its infancy. Controlled fabrication of SWNT-SETs has been demonstrated by introducing kinks using AFM. However, AFM manipulation is time consuming and reproducibility can be extremely challenging. Here, we show a novel approach to fabricate controllable and reproducible SETs using SWNT. SWNTs were placed on 100 nm wide local Al/Al$_{2}$O$_{3}$ bottom gates and then contacted with Pd source and drain electrodes with 1 um spacing on Si/SiO$_{2}$ substrates. The Al gate serves two purposes (i) it defines tunnel barriers at the edges of the gate electrodes by introducing buckles, and (ii) it acts as a local gate to tune the number of carriers in the central island. Low temperature electronic transport measurements show coulomb oscillations up to 125 K. The stability diagram shows a charging energy of $\sim $ 13 meV and energy level spacing of $\sim $ 5 meV. These energies are consistent with a quantum dot size of $\sim $100 nm, thus verifying the dot is defined and controlled by the 100 nm wide aluminum oxide gate. [Preview Abstract] |
Monday, March 10, 2008 12:39PM - 12:51PM |
B30.00006: Nanotube enabled thin film transistors utilizing low mobility organic semiconductors. Bo Liu, Mitchell McCarthy, Youngki Yoon, Doyoung Kim, Zhuangchun Wu, Franky So, Paul H. Holloway, John R. Reynolds, Jing Guo, Andrew G. Rinzler We describe a novel organic thin film transistor architecture enabled by single walled carbon nanotubes. Initial devices exhibit 2 orders of magnitude current modulation at useful currents despite the use of low mobility organic semiconductors (that exhibit no detectable current in a conventional TFT architecture). Modeling shows that the present devices function principally via Shottky barrier modulation, however as the source drain distance is reduced bulk modulation should also occur, with corresponding improvements in performance. [Preview Abstract] |
Monday, March 10, 2008 12:51PM - 1:03PM |
B30.00007: Structural and Electronic Properties of Single-Walled Carbon Nanotube Heterojunctions Joydeep Bhattacharjee, Young Woo Son, Bhupesh Chandra, James Hone, Jeffrey B. Neaton Inspired by recent experiments[1], we present a systematic approach to construct structural models of mostly linear single walled carbon nanotube (SWCNT) heterojunctions. A minimum number of 5-7 defects is found to be required to join two SWCNTs of differing chiralities. Using nearest-neighbor tight-binding and first-principles density functional theory, we explore the sensitivity of the heterojunction electronic structure and transport properties to different arrangements of the interfacial 5-7 defects, and discuss their implications for future experiments and nanoelectronic applications. \begin{thebibliography}{1} \bibitem{bj} B. Chandra, J. Hone, {\it Unpublished}. \end{thebibliography} [Preview Abstract] |
Monday, March 10, 2008 1:03PM - 1:15PM |
B30.00008: Synthesis and Structure of Carbon Nanotube Junctions and Co$_{9}$S$_{8}$ Nanowire-filled Carbon Nanotubes Wenzhi Li, Gaohui Du We describe the synthesis of carbon nanotube junctions and Co$_{9}$S$_{8}$ nanowire-filled carbon nanotubes by pyrolysis of thiophene on cobalt catalyst in chemical vapor decomposition. The formation of these nanostructures is strongly dependent on the thiophene vapor concentration during the material synthesis. The carbon nanotube junctions have hollow channels while the filled carbon nanotubes have solid Co$_{9}$S$_{8}$ cores. The encapsulated Co$_{9}$S$_{8}$ nanowires are single crystals, and their lengths are about 10 $\mu $m with their [110] direction parallel to the axis of the carbon nanotubes. It is postulated that the filling of the Co$_{9}$S$_{8}$ nanowires results from the volume increase of the catalyst induced by a phase transition from cobalt to cobalt sulfide and the spatial confinement of the carbon nanotubes as nano-molds. [Preview Abstract] |
Monday, March 10, 2008 1:15PM - 1:27PM |
B30.00009: Adsorption of Alcohols and Alkanes 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 (CNTs) reveal a strong electrical response during exposure to polar alkane derivatives such as linear alcohols C$_{n}$H$_{2n+1}$OH, which is in contrast with the weak response to linear alkanes C$_{n}$H$_{2n+2}$. To develop an understanding of the microscopic mechanisms involved, we perform detailed \textit{ab initio} calculations of adsorption geometries and charge configurations for the size parameter $n$ from 1 to 8 on pristine zig-zag and armchair CNTs. We use Density Functional Theory with localized orbitals in a cluster approach, along with the M05-2X functional appropriate for the weak interactions of physisorption for these systems. We find that adsorption energies are larger for alcohols than for alkanes and increase linearly in energy with length of the molecule $n$ for both alcohols and alkanes (at 35 meV and 40 meV per additional CH$_{2}$, respectively). This is found to be in good agreement with the binding energy per additional CH$_{2}$ estimated from the fast conductance response measurements for both alcohols and alkanes using a simple kinetic theory model. We estimate small charge transfers for all molecules, which suggest that the electric response is dominated by the scattering from the dipole moments of the adsorbates. [This work is supported by the Office of Naval Research.] [Preview Abstract] |
Monday, March 10, 2008 1:27PM - 1:39PM |
B30.00010: Adsorption of neon and tetrafluoromethane on carbon nanohorn aggregates: differences in specific surface area values Vaiva Krungleviciute, Masako Yudasaka, Sumio Iijima, Aldo Migone We have measured adsorption isotherms for two different adsorbates, neon and tetrafluoromethane, on dahlia-like carbon nanohorn aggregates. The experiments were performed at similar relative temperatures for both gases. The measurements were conducted to explore the effect of adsorbate diameter on the behavior of the resulting adsorbed systems. We measured the effective specific surface area value of the nanohorn sample using both gases, and we found that this quantity was about 22{\%} smaller when we determined this quantity using tetrafluoromethane, the larger molecule. Isosteric heat and binding energy values were also determined from our measurements. We will compare our experimental results with those from a computer simulation study performed by Prof. M. Calbi. The simulations help us understand the source of the observed differences in the measured specific surface values, as well as the coverage dependence of the isosteric heat of adsorption for both gases. [Preview Abstract] |
Monday, March 10, 2008 1:39PM - 1:51PM |
B30.00011: Application of nanohorns to anti-cancer drug carriers Masako Yudasaka, Minfang Zhang, Kumiko Ajima, Jin Miyawaki, Tatsuya Murakami, Kunihioro Tsuchida, Sumio Iijima Potential applications of single-wall carbon nanohorns (SWNH) that have shown no acute toxicity in various tailored animal experiments, to the drug delivery system have been studied. We previously reported that the drugs were able to be incorporated inside SWNH at room temperature through liquid phase, and chemical modifications with hydrophilic molecules enhanced dispersion of SWNHs in aqueous solutions. The modifications with the tumor-targeting molecules were also possible. The contrast agent attachments enabled the in vivo visualization of SWNHs by magnetic resonance imaging. We show in this report how the effects of anti-cancer drugs were influenced by being incorporated inside SWNHs, and discuss its reasons. [Preview Abstract] |
Monday, March 10, 2008 1:51PM - 2:03PM |
B30.00012: Building Physical Carbon Nanoparticles from Small-World Networks: Density Functional Theory Calculations Jeremy A. Yancey, M.A. Novotny, Steven R. Gwaltney We have performed B3LYP/6-31G* Density Functional Theory calculations on carbon cluster nanoparticles built with (pseudo) small-world network topologies to determine whether they are stable and can exist in nature. Such particles may have novel material properties due to their (pseudo) small-world nature [1]. We have embedded a ring of carbons with one or more small-world connections made with and without additional carbon atoms. No carbon is allowed to make more than four bonds. The energy per atom of these (pseudo) small-world carbon systems is compared with benchmark carbon clusters including monocyclic rings, linear rods, graphene fragments, and various fullerenes from C$_{20}$ to C$_{60}$. The energy per atom and vibrational frequency calculation results for these materials indicate that there are pure-carbon small-world nanomaterials that are reasonable for real world synthesis. We present both NMR and IR spectra for these nanoparticles. [1] M.A. Novotny, \textit{et al}, J. Appl. Phys, \textbf{97}, 10B309 (2005). [Preview Abstract] |
Monday, March 10, 2008 2:03PM - 2:15PM |
B30.00013: First-Principles Study of Carbon Nanoframeworks Tailored for Hydrogen Storage Eunja Kim, Philippe Weck, Balakrishnan Naduvalath, Hansong Cheng, Boris Yakobson Based on first-principles calculations, we propose a novel class of 3-D materials consisting of small diameter single-walled carbon nanotubes (SWCNTs) functionalized by organic ligands as potential hydrogen storage media. Specifically, we have carried out density functional theory calculations to determine the stable structures and properties of nanoframeworks consisting of (5,0) and (3,3) SWCNTs constrained by phenyl spacers. Valence and conduction properties, as well as normal modes, of pristine nanotubes are found to change significantly upon functionalization, in a way that can serve as experimental diagnostics of the successful synthesis of the proposed framework structures. Ab initio molecular dynamics simulations indicate that such systems are thermodynamically stable for on-board hydrogen storage. In order to increase the hydrogen uptake in the interstitial cavity of such nanoframeworks, we are currently investigating the possibility of Li deposition on these nanostructures. [Preview Abstract] |
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