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This does not exclude the possibility, that larger structural fragments (such as tetra-mers and pentamers) can also contribute to the low-frequency vibrational spectrum around the boson peak. On the basis of these results, the following model of the glass transition of glycerol can be proposed. At temperatures far above Tg (186 K), the lifetime of the MRO(More)
We describe, in detail, a readily scalable purification process capable of handling single-wall carbon nanotube (SWNT) material in large batches. Characterization of the resulting material by SEM, TEM, XRD, Raman scattering, and TGA shows it to be highly pure. Resistivity measurements on freestanding mats of the purified tubes are also reported. We also(More)
Ž. Single-walled carbon nanotubes SWNTs have been synthesized at milligram per hour rates by the catalytic decomposition of both carbon monoxide and ethylene over a supported metal catalyst known to produce larger multiwalled nanotubes. Under certain conditions, there is no termination of nanotube growth, and production appears to be limited only by the(More)
Field emission of electrons from individually mounted carbon nanotubes has been found to be dramatically enhanced when the nanotube tips are opened by laser evaporation or oxidative etching. Emission currents of 0.1 to 1 microampere were readily obtained at room temperature with bias voltages of less than 80 volts. The emitting structures are concluded to(More)
(nominal inner diameter: 0.6 mm) needles into rotating 40 wt.-% PEI (branched; average molecular weight, M w ~ 25 000; water-free; Aldrich) solutions in methanol. The SWNT/PEI composite fibers were characterized by SEM (LEO 1590 VP microscope) and micro-Raman spectroscopy (Jobin± Yvon Horiba high-resolution LabRam micro-Raman spectrometer; helium±neon(More)
Carbon nanotubes produced in arcs have been found to have the form of multiwalled fullerenes, at least over short lengths. Sintering of the tubes to each other is the predominant source of defects that limit the utility of these otherwise perfect fullerene structures. The use of a water-cooled copper cathode minimized such defects, permitting nanotubes(More)
The fluorescence spectra of individual semiconducting single-walled carbon nanotubes embedded in polymer films were measured during the application of controlled stretching and compressive strains. Nanotube band gaps were found to shift in systematic patterns that depend on the (n,m) structural type and are in excellent agreement with the predictions of(More)
A new method was used to measure the fraction of semiconducting nanotubes in various as-grown or processed single-walled carbon nanotube (SWCNT) samples. SWCNT number densities were compared in images from near-IR photoluminescence (semiconducting species) and AFM (all species) to compute the semiconducting fraction. The results show large variations among(More)
ZnS, an important wide-bandgap semiconductor, is a photo-luminescence material. [1] Due to its wide bandgap of 3.8 eV, doping of ZnS with elements such as Tb and Eu, [2] can produce a wide range of exciting optical properties. Quantum dots of core±shell structured CdSe/ZnS have been found to exhibit a lasing effect and can be used for fluoro-immunoas-says,(More)
We demonstrate that argon ion bombardment of single crystal sapphire leads to the creation of substrates that support the growth of vertically aligned carbon nanotubes from iron catalysts with a density, height, and quality equivalent to those grown on conventional, disordered alumina supports. We quantify the evolution of the catalyst using a range of(More)