Bulletin of the American Physical Society
2006 APS March Meeting
Monday–Friday, March 13–17, 2006; Baltimore, MD
Session B18: Focus Session: Carbon Nanotubes: Synthesis, Processing and Characterization |
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Sponsoring Units: DMP Chair: David Luzzi, University of Pennsylvania Room: Baltimore Convention Center 315 |
Monday, March 13, 2006 11:15AM - 11:51AM |
B18.00001: Density gradient ultracentrifugation of single-walled nanotubes Invited Speaker: We demonstrate the bulk separation and enrichment of single-walled carbon nanotubes (SWNTs) by diameter via density gradient ultracentrifugation.(1) Means for sorting SWNTs by their physical and electronic structures are essential for future electronic and optical applications where semiconducting SWNTs mono-disperse in diameter are necessary. The separation is driven by subtle variations in the buoyant density of these nanomaterials with small changes in their physical structure. After centrifugation in a density gradient, focused bands of various colors consisting of isolated SWNTs are clearly visualized by eye. By fractionating the centrifuge tube and characterizing the absorbance and photoluminescence spectra of the sorted SWNTs, it is apparent that SWNTs of decreasing diameter are increasingly more buoyant. This scalable and non-destructive separation strategy uses centrifugation equipment already utilized in the solution-based processing of carbon nanotubes, and simultaneously separates isolated and aggregated SWNTs, which sediment to larger buoyant densities due the reduced solvation and surface-to-volume ratios of these larger structures. Along these lines, the removal of aggregates and spurious materials is evidenced by significantly lower background absorbencies in optical absorbance spectra. For the case of isolated SWNTs, we propose a geometric-based hydration model to describe the unexpected trend of increasing density with increasing diameter. The effectiveness of this technique is best demonstrated for SWNTs that are small in diameter. For example, in the small diameter regime, it is possible to sort the (6,5) and (7,5) tubes, which differ in diameter by only 0.7 {\AA}. (1) M. S. Arnold et al. Nano Lett. 5 (2005) 713-718. [Preview Abstract] |
Monday, March 13, 2006 11:51AM - 12:03PM |
B18.00002: Determination of Diameter, Helicity, and Handedness of Carbon Nanotubes by Electron Diffraction Zejian Liu, Lu-Chang Qin We report a systematic procedure to determine the diameter, helicity and handedness of multiwalled carbon nanotubes by using nanobeam electron diffraction technique. Diameter and helicity of a nanotube can be measured directly from the scattering intensity distribution on the non-equatorial layer lines in its electron diffraction pattern, while the handedness information need be derived from several diffraction patterns of different orientations when if there exist concentric shells of the same helicities in the nanotube. Two selected examples of metallic triple-walled carbon nanotubes are presented to illustrate the detailed structure determination. [Preview Abstract] |
Monday, March 13, 2006 12:03PM - 12:15PM |
B18.00003: Diameter Recognition of Single Walled Carbon Nanotubes by Water-Soluble Proteins Koji Matsuura, Takeshi Saito, Toshiya Okazaki, Satoshi Ohshima, Kohei Mizuno, Don Futaba, Kenji Hata, Motoo Yumura, Sumio Iijima The hybrid of proteins and single walled carbon nanotubes (SWCNT) is a promising advanced material that possesses both functions of associated proteins and SWCNTs. Using SWCNTs of varying diameter, synthesized by two distinct methods, Direct-Injection-Pyrolytic-Synthesis [1] (0.8- 1.2 nm) and super-growth chemical vapor deposition [2] (mean diameter of 3 nm), we observed diameter-selective dispersion for two differing proteins which is driven by the sizes of the hydrophobic pockets in the proteins. Hybrid solutions of both lysozyme (LYS) and bovine serum albumin (BSA) dispersed the smaller diameter SWCNTs as observed by absorbance and photoluminescence spectroscopy. The larger diameter SWCNTs were dispersed in the BSA solution, while not dispersed by LYS. A decrease in the mean molar ellipticity observed by far-UV circular dichroism spectroscopy following the removal of unadsorbed proteins suggests a loss in $\alpha $-helical contents of the proteins. These results, in addition to the difference in size of BSA and LYS (10 and 4 nm, respectively), indicate the hydrophobic pockets corresponding to the protein morphology can recognize the SWCNT diameters. [1] Saito et al. J. Phys. Chem. B (2005) 109, 10647. [2] Hata et al. Science (2004) 306, 1362. [Preview Abstract] |
Monday, March 13, 2006 12:15PM - 12:27PM |
B18.00004: Structure determination of a nine-wall carbon nanotube by nanobeam electron diffraction. Qi Zhang, Zejian Liu, Lu-Chang Qin, Xinluo Zhao, Yoshinori Ando Multiwalled carbon nanotubes are composed of a series of coaxial single walled carbon nanotuebs. While great progress has been made in determining the atomic structure of single-walled carbon nanotubes, few direct measurements of the atomic structure of multiwalled carbon nanotubes have been available. Meanwhile, it is still a challenging task to determine the atomic structure of nanotubes with large diameter. In this work, the atomic structure of a nine-walled carbon nanotube was determined by nanobeam electron diffraction with the assignment of the chiral indices of each and every individual shell. The chiral indices of the innermost tubule has chiral indices [5,5], corresponding to the C$_{60}$ molecule. The diameters are from 0.678 nm to 6.445 nm with inter-shell spacings between the neighboring tubules in the range of 0.309 nm to 0.408 nm, the helical angles from 11.51$^{o}$ to 30$^{o}$, in which eight tubes are falling in the high helicity from 15$^{o}$ to 30$^{o}$. [Preview Abstract] |
Monday, March 13, 2006 12:27PM - 12:39PM |
B18.00005: Quantitative Characterization of Defect Densities in Single-Walled Carbon Nanotubes Yuwei Fan, Brett Goldsmith, Philip Collins The prevailing conception of carbon nanotubes and particularly single-walled carbon nanotubes (SWNTs) continues to be one of perfectly crystalline wires. We have demonstrated a selective electrochemical method which labels point defects and makes them easily visible for quantitative analysis. High-quality SWNTs are confirmed to contain one defect per 4 um on average, with a distribution weighted towards areas of SWNT curvature. While this defect density compares favorably to high quality, silicon single crystals, the presence of a single defect can have tremendous electronic effects in one-dimensional conductors like SWNTs. We demonstrate a one-to-one correspondence between chemically-active point defects and sites of local electronic sensitivity in SWNT circuits, confirming the expectation that individual defects may be critical to understanding and controlling variability, noise, and chemical sensitivity in SWNT electronic devices. By varying the SWNT synthesis technique, we further show that the defect spacing can be varied over orders of magnitude. The ability to detect and analyze point defects, especially at very low concentrations, indicates promise of this technique for quantitative process analysis, especially in nanoelectronics development. This work is partly supported by NSF grant DMR-0239842. [Preview Abstract] |
Monday, March 13, 2006 12:39PM - 12:51PM |
B18.00006: Shape Engineerable Single Walled Carbon Nanotube Solid as a Flexible Conducting Mesoporous Material Don N. Futaba, Kenji Hata, Tatsuki Hiraoka, Takeo Yamada, Kohei Mizuno, Yuhei Hayamizu, Tatsunori Namai, Yozo Kakudate, Osamu Tanaike, Hiroaki Hatori, Koji Miyake, Shinya Sasaki, Motoo Yumura, Sumio Iijima We present a new form of carbon nanotubes (CNT) material where CNTs are aligned and packed densely in a bulk solid. This single-walled carbon nanotube (SWNT) solid is fabricated from liquid-induced collapse of the sparse as-grown SWNT forest synthesized by super-growth CVD [1], which results in a 20x increase in mass density and a 70x increase in the Vickers hardness while retaining alignment and high surface area. As such, SWNT solid is an ideal form of CNTs for material and energy storage. The high surface area and well-defined microscopic structure imply that SWNT solid can be regarded as a conductive and flexible mesoporous material. In addition, we can engineer shapes suitable to the application. These unique characters make SWNT solid as a valuable material for supercapacitor electrodes and flexible heaters. Furthermore, we show how partial shrinking of the as-grown material creates a \textit{handle} for robust mechanical and electrical connection to demonstrate exceptional tribological character and wear rate. The SWNT solid promises to open new frontiers in within the carbon nanotube field. [1] K. Hata \textit{et al}, Science, \textbf{306}, 1241 (2004). [Preview Abstract] |
Monday, March 13, 2006 12:51PM - 1:03PM |
B18.00007: Filtration Patterning of Single Walled Carbon Nanotube Films David A. Daly, Zhuangchun Wu, Andrew G. Rinzler Carbon nanotubes are increasingly being explored for applications exploiting the bulk electrical conductivity of aggregate nanotubes in the form of fibers and films. Attractive in this regard are electrical conductivities orders of magnitude greater than those of conducting polymers, while retaining many of the useful features of polymers, e.g. flexibility, transparency (in thin films) and alternative device fabrication strategies. Here we describe a novel, non-lithographic patterning technique that should also be applicable to other nano-materials. The technique is based on our method for forming thin, pure nanotube films on the surface of a filtration membrane followed by transfer of the film to the desired substrate.$^{1}$ To generate patterned films we block the pores of the filtration membrane in the inverse of the ultimately desired film pattern, prior to film formation on the surface of the membrane. The nanotubes only accumulate in the membrane regions that are not occluded, resulting in the desired pattern. Blocking of the membrane pores is accomplished with use of a commercial printer. Implementation and limitations of the technique will be discussed. 1. Z. Wu, Z. Chen, X. Du, J. M. Logan, J. Sippel, M. Nikolou, K. Kamaras, J. R. Reynolds, D. B. Tanner, A. F. Hebard, A. G. Rinzler, Science 305, 1273 (2004). [Preview Abstract] |
Monday, March 13, 2006 1:03PM - 1:15PM |
B18.00008: The Order in Vertically Aligned Carbon Nanotube Arrays Howard Wang, Zhiyong Xu, Gyula Eres Vertically aligned carbon nanotube (CNT) arrays can exploit the remarkable properties of individual nanotubes in macroscopic applications. Here we report the first measurements of the degree of alignment order in as-grown vertically aligned CNT arrays using small angle neutron scattering. The scattering patterns reveal continuously varying alignment order along the growth and two distinctly different morphologies of CNTs. The observations are discussed in the light of growth mechanisms. [Preview Abstract] |
Monday, March 13, 2006 1:15PM - 1:27PM |
B18.00009: Physical properties of self-assembled monolayers of carbon nanotubes V.A. Samuilov, J. Galibert, V. Ksenevich, N.A. Poklonski, L. Forro, J. Koo, K. Yoon, M. Rafailovich, J. Sokolov The controlled method of self-assembly of functionalized carbon nanotubes into 2-D layers with highly regular structure and unique electronic properties has been developed. We use the Langmuir-Blodgett (LB) technique and newly developed inverted LB techniques. The alignment carbon nanotubes in the self-assembled 2-D layers was also introduced. The methods we propose, could be used for covering large surfaces with dense, molecularly ordered ultra-thin films of nanotubes of controlled thickness and orientation. The electrical, thermal conductivity and magneto-transport properties of the monolayers (arrays) of multi-wall and single-wall carbon nanotubes in the temperature range 1.8-300K and in magnetic fields up to 35 T have been tested. [Preview Abstract] |
Monday, March 13, 2006 1:27PM - 1:39PM |
B18.00010: Linear Dichroic Cell Based on Magnetic Alignment of Carbon Nanotubes Y. J. Lee, J. Shaver, S. Zaric, J. Kono Single-walled carbon nanotubes align with a magnetic field due to their anisotropic magnetic properties. A simple yet sensitive setup utilizing a balance detector has been constructed to study the alignment of micelle-suspended single-walled carbon nanotubes. We present alignment data in response to static and dynamic magnetic fields. The results of our ensemble measurements show that the amount of signal change depends on the strength and frequency of the applied magnetic field, thus allowing us to determine the minimum field required to align single-walled carbon nanotubes. This data can then be analyzed to characterize the physical parameters of the carbon nanotubes and to determine information about the time scale of the alignment process and local environment. [Preview Abstract] |
Monday, March 13, 2006 1:39PM - 1:51PM |
B18.00011: The Conformation of Polymers Dispersing Single-Walled Carbon Nanotubes in Water. Yael Dror, Yachin Cohen, Wim Pyckhout-Hintzen Amphiphilic polymers have been used to disperse single-walled carbon nanotubes (SWCNT) in water. The polymer conformation around the nanotube surface is important for understanding the nature of the interactions leading to successful dispersions. Two extreme cases are ``tight wrapping'' of the polymer around the nanotube and ``loose adsorption'' of solvated polymer coils on the nanotube surface. We studied aqueous dispersions of SWCNTs with an alternating copolymer of styrene and sodium maleate (PSSty) by small-angle neutron scattering (SANS) and cryo transmission electrons microscopy (cryo-TEM). Dispersion of long, isolated nanotubes and thin bundles was revealed by cryo-TEM. The SANS patterns (at different solvent contrasts) were evaluated by a modification of Pedersen's ``cylindrical block copolymer micelle'' model, depicting the nanotube-polymer complex as composed of a thin core, the radius of which is about 20 A thus containing about 3-4 nanotubes, surrounded by a thick corona of water-swollen polymer coils with a radius of gyration of 150-170 A. Long-term stabilization is achieved by the steric barrier provided by the adsorbed polymer coils reinforced by electrostatic repulsion due to charged groups distributed along the polymer. [Preview Abstract] |
Monday, March 13, 2006 1:51PM - 2:03PM |
B18.00012: High performance field emission in hybrid carbon nanotube-PDMS composite Caterina Soldano, Swastik Kar, Yung J. Jung, Saroj K. Nayak, Omkaram Nalamasu, Pulickel M. Ajayan We present a novel method of fabricating flexible carbon nanotube polymer composites by embedding aligned multi-walled carbon nanotube (MWNT) architectures into a polydimethylsiloxane (PDMS) polymer matrix. These structures are easily transferable, electromechanically robust and extremely flexible, and therefore suitable for applications as multifunctional flexible electronic devices. A combination of controlled placement of aligned multi-walled nanotubes on pre-patterned locations and an effective suppression of mutual screening gives these devices impressive field emission properties. With large field emission factors ($\beta \sim $10$^{4})$ and low (sub 1V/$\mu $m) turn-on fields, these composites can easily operate at high current densities ($>$1mA/cm$^{2})$ at relatively low voltages making them also suitable for applications in electrically and mechanically stable flexible sensors and display devices. [Preview Abstract] |
Monday, March 13, 2006 2:03PM - 2:15PM |
B18.00013: Thermal Oxidation Profiling of Single-Walled Carbon Nanotubes Brian Landi, Cory Cress, Chris Evans, Ryne Raffaelle A method of thermal oxidation profiling (TOP) to monitor the properties of single-walled carbon nanotube (SWNT)-containing samples has been developed. In the present analysis, the thermal decomposition of raw and acid-refluxed SWNT samples is evaluated by a systematic series of oxidative thermal treatments with subsequent calculation of the SWNT mass retention using a verified purity assessment technique. The TOP results indicate that there are no discernable regions of a raw soot TGA curve that can be ascribed to SWNT combustion independent of impurity influence. In contrast, the acid-refluxed SWNT sample shows that chemical oxidation of the metal can enable optimization of SWNT retention during thermal purification. The established understanding allows for purification efficiencies (the highest purity at the maximum retention) of 75{\%} w/w to be achieved in laser-produced SWNTs, without modification to the diameter distribution. [Preview Abstract] |
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