CATALYTIC EFFECTS OF HEAVY-METALS ON THE GROWTH OF CARBON NANOTUBES AND NANOPARTICLES

The effects of bismuth, lead, and tungsten on the cobalt-catalyzed syn thesis of single-layer carbon nanotubes and nanoparticles have been st udied. When co-vaporized with cobalt in an electric are, bismuth and l ead increase the yield of single-layer nanotubes and broaden the range of tube diameters, compared to the case where only cobalt is used. Tu ngsten is found to reduce the nanotube yield and does not change the t ube diameter distribution. Both tungsten and bismuth increase the grap hitization of the carbon encapsulating the cobalt particles found in t he soot, while lead does not. None of these three heavy metals catalyz es the formation of single-layer nanotubes without a transition metal present.