Raman characterization of single wall carbon nanotubes prepared by the solar energy route

A Raman scattering characterization is reported that confirms the preparation of single wall carbon nanotubes (SWNT) by the solar energy route. The results are presented for samples synthesized with various catalysts-mixtures of Ni and Co (Y, La)-and compared to those obtained from electric are discharge or laser ablation. In the light of the calculations of the vibrational spectra of SWNT by Eklund et al. (Carbon, 1995, 33, 959) it is shown that both the diameter and structure of the nanotubes depend strongly on the synthesis conditions. For the First time the presence of nanotubes with "zigzag" or "chiral" helical pitches for some of the samples are shown as well as a large distribution of tube diameters. (C) 1998 Elsevier Science Ltd. All rights reserved.