PURIFIED CARBON NANOPARTICLES INVESTIGATED WITH HREM AND RAMAN-SPECTROSCOPY

Previous studies of fullerene-related materials (nanotubes, onions, et c.) have been almost exclusively performed with electron microscopy me thods due to the heterogeneous character of the deposits produced in t he electric arc. We report Raman spectra of carbon nanotubes which hav e been purified following the procedure of Ebbesen et al. The purity o f the sample has been confirmed by high-resolution electron microscopy . The Raman spectra of carbon nanotubes with an average diameter of 10 -12 nm show very little disorder-induced scattering and no curvature-i nduced phonon softening, in contrast to unpurified material which cont ains a large number of carbon nanoparticles. These experimental findin gs are confirmed by lattice-dynamical calculations. Preliminary low-lo ss EELS measurements on nanotubes reveal significant differences for t he graphite interband transition and collective valence-electron plasm on excitation, which are attributed to the cylindrical structure of th e nanotubes.