Showing papers by "S. Roth published in 2001"
TL;DR: In this article, the hydrogen storage in purified single-wall carbon nanotubes (SWNTs), graphite and diamond powder was investigated at room temperature and ambient pressure, and the maximum value of overall hydrogen storage was found to be 1.5 wt %, as determined by thermal desorption spectroscopy.
Abstract: The hydrogen storage in purified single-wall carbon nanotubes (SWNTs), graphite and diamond powder was investigated at room temperature and ambient pressure. The samples were sonicated in 5 M HNO3 for various periods of time using an ultrasonic probe of the alloy Ti-6Al-4V. The goal of this treatment was to open the carbon nanotubes. The maximum value of overall hydrogen storage was found to be 1.5 wt %, as determined by thermal desorption spectroscopy. The storage capacity increases with sonication time. The sonication treatment introduces particles of the Ti alloy into the samples, as shown by X-ray diffraction, transmission electron microscopy, and chemical analysis. All of the hydrogen uptake can be explained by the assumption that the hydrogen is only stored in the Ti-alloy particles. The presence of Ti-alloy particles does not allow the determination of whether a small amount of hydrogen possibly is stored in the SWNTs themselves, and the fraction of nanotubes opened by the sonication treatment is unknown.
295 citations
TL;DR: In this paper, single crystalline germanium nanowires were synthesized from gold nanoparticles based on a vapor-liquid-solid growth mechanism using argon as a carrier gas.
Abstract: Single crystalline germanium nanowires have been synthesized from gold nanoparticles based on a vapor–liquid–solid growth mechanism. Germanium powder was evaporated at 950 °C, and deposited onto gold nanoparticles at 500 °C using argon as a carrier gas. The diameter of the germanium nanowires ranged from 20 to 180 nm when gold thin films were utilized as the substrate, while the nanowires grown from 10 nm Au particles showed a narrower diameter distribution centered at 28 nm. The growth direction of germanium nanowires is along the [111] direction, determined by high resolution transmission electron microscopy. Transport measurements on individual Ge nanowires indicate that the wires are heavily doped during growth and that transport data can be explained by the thermal fluctuation tunneling conduction model.
156 citations
TL;DR: In this paper, the non-ohmic current-voltage characteristics of the single-wall carbon nanotube network were investigated at low temperatures, and the temperature dependence of resistivity at low current was found to be non-metallic negative d ρ /d T from T = 1.4-300 K.
42 citations
TL;DR: In this paper, the electrical transport properties of iodine doped polyacetylene (PA) nanofibers were measured as function of temperature in micron and sub-micron scale.
38 citations
36 citations
TL;DR: In this article, the phonon symmetries in the Raman spectra of single and multi-wall nanotubes were investigated by using linearly and circularly polarized light.
Abstract: We investigated the phonon symmetries in the Raman spectra of single and multiwall nanotubes. By using linearly and circularly polarized light we measured the Raman tensor invariants on unoriented carbon nanotubes. The ratio between the antisymmetric and the isotropic invariant shows that Raman scattering in semiconducting single wall tubes is mainly due to fully symmetric ${A}_{1(g)}$ phonons with a strongly uniaxial Raman tensor. With the help of recent experiments on aligned nanotubes we calculate the relative intensities for the high-energy modes of different symmetry. Compared to single wall tubes the intensity of the ${E}_{1(g)}$ and ${E}_{2(g)}$ symmetry phonons in multiwall tubes is 1.5 times stronger. The antisymmetric component of the resonant Raman process was found to be zero in all measurements.
30 citations
TL;DR: In this paper, a single carbon single-walled nanotube (SWNT) was used to demonstrate the viability of a single-nano-actuator based actuator.
25 citations
TL;DR: In this article, a single polyacetylene (PA) nanofiber, a single-walled carbon nanotube (SWNT)-rope, and a lithographically prepared stripe of poly(2-methoxy-5-(2-ethyl hexyloxy)-p-phenylene vinylene) (MEH-PPV) were measured.
21 citations
TL;DR: In this article, the I-V characteristics of I-doped polyacetylene (PA) nanofibers were measured as function of temperature and the gate dependence showed the charge carrier to be hole with a mobility μ FET ∼ 4.4×10 -5 cm 2 /Vs at 233K.
20 citations
TL;DR: In this paper, the authors used ultrahigh vacuum scanning tunneling microscopy (STM) to investigate Cr-filled multiwalled carbon nanotubes and found that strong apparent height variations along the tube axis are sensitively dependent on the imaging bias.
Abstract: We have used ultrahigh vacuum scanning tunneling microscopy (STM) to investigate Cr-filled multiwalled carbon nanotubes Dendritic and bamboo features were observed in this material Anomalous contrast effects, resulting in extreme width-to-height ratios, are ascribed to tip effects as well as to intrinsic electronic properties of the filled tubes In particular, we find that strong apparent height variations along the tube axis are sensitively dependent on the imaging bias These results suggest that Cr filling of carbon nanotubes results in strong electronic interactions between tube and filling materials
13 citations
07 Nov 2001
TL;DR: In this article, the hydrogen storage capacity in mechanically treated single wall carbon nanotubes (SWNTs) was investigated by applying three mechanical methods: ball milling, ultrasonication and rubbing.
Abstract: The hydrogen storage capacity in mechanically treated single wall carbon nanotubes (SWNTs) is investigated in this paper. In order to open the nanotubes three mechanical methods were applied: ball milling, ultrasonication and rubbing. Changes induced by the treatment were analyzed by Raman spectroscopy. The amount of hydrogen stored by the SWNTs reaches fractions of weight percents only. In the case of sonicated specimens, the hydrogen storage can be ascribed to titanium particles incorporated during the treatment.
TL;DR: In this article, the authors obtained V O -polyaniline nanorods, as it has been 25 yX ε(n) resistances in the temperature range from RT to 140 K, on 20-nm thick and 300-800-nm long deposited on a sample holder.
TL;DR: In this paper, a single-walled carbon nanotube (SWCN) rope is contacted to a 4-probe Au/Pd electrode in the Coulomb blockade regime.