Formation mechanism of carbon nanotubes in the gas-phase synthesis from colloidal solutions of nanoparticles

Single- and multi-wall carbon nanotubes have been synthesized by the gas-phase catalytic reaction of colloidal solutions of metal nanoparticles using a vertical flow reactor. The reverse micelle solution of the Co-Mo nanoparticles with the mean diameter of 11 nm dissolved in toluene was injected directly into the reactor maintained at 1200 °C. The nanoparticles and the solvent act as the catalyst and carbon source, respectively. When the concentration of the thiophene additive is low (1 wt.%), the formation of SWNT bundles preferentially occurred. The SWNT bundles were present together with the relatively small metal nanoparticles with the diameter of 0.5-5.5 nm. It is likely that the original nanoparticles with the diameter of 11 nm break into smaller ones, 1-2 nm diameters, which is suitable for the SWNT growth. The synactic effect of Co and Mo was also observed.