  Single-walled carbon nanotubes (SWNTs) have been coated with gold and
platinum nanoparticles either by microwave treatment or by the click reaction
and the Raman spectra of these SWNT-metal nanoparticle composites have been
investigated. Analysis of the G bands in the Raman spectra shows an increase in
the proportion of metallic SWNTs on attachment with metal nanoparticles. This
conclusion is also supported by the changes observed in the RBM bands.
Ab-initio calculations reveal that semiconductor-metal transition occurs in
SWNTs due to Columbic charge transfer between the metal nanoparticles and the
semiconducting SWNTs.
