S. Lebedkin

Dimerization of C70 under high pressure: Thermal dissociation and photophysical properties of the dimer C140

We have recently shown that solid C70 efficiently converts into a cap-to-cap dimer C2hC140 at pressure of ∼1 GPa and temperature of ∼200 °C [1]. Here we report on measurements of the thermal dissociation of C140 (purified by chromatography) at ambient pressure and its photophysical properties, in particular photogeneration of singlet oxygen (1O2). The kinetics of dissociation of C140 in the solid state between 130 and 200 °C is well described by a simple first-order process, with an activation energy of 1.6±0.03 eV (compare to 1.75±0.05 eV for the C60 dimer C120 [2]). In contrast, the thermal dissociation of C140 dissolved in o-dichlorobenzene shows different, non-Arrhenius behavior, suggesting a strong influence of the molecular surroundings. The quantum efficiency of 1O2 generation in solutions of C140 and C120 is close to unity, i.e. similar to that of C70 and C60.

Hydrogen storage in carbon nanotubes: A neutron scattering investigation

Samples of closed and opened single-walled carbon nanotubes (SWNT’s) were charged with hydrogen and investigated by neutron time-of-flight spectroscopy. Contributions of H2 adsorbed by SWNT’s are observed and analyzed with respect to their microscopic dynamics for different temperatures.

Modification of the Electronic Properties of Carbon Nanotubes: Bundling and B ‐ and N ‐ doping

We report on a substantial modification of the electronic properties of single‐walled carbon nanotubes (CNTs) via tube‐tube interactions and incorporation of structural defects (boron and nitrogen atoms). Using Raman and photoluminescence spectroscopy, we observed a decrease of the electronic interband transition energies Eii in tube bundles compared to individual tubes of pure CNTs. Weak (off‐resonance) Raman signals from BxNyCz nanotubes at relatively high B and N concentrations can be attributed to an increase of the interband energies.

Large diameter single-wall carbon nanotubes obtained by pulsed laser vaporization

We found that the addition of FeS to C:Ni:Co targets and/or H2 to a process gas (Ar) results in the efficient growth of large diameter single-wall carbon nanotubes (SWNTs) under pulsed laser vaporization conditions. The addition of both FeS and H2 has a particularly strong effect, shifting the tube diameters to the range of ∼2–5.6 nm. As prepared SWNT materials were characterized by SEM, HRTEM, Raman spectroscopy, thermogravimetric analysis and other methods.