Semiconductor to metal transition in SWNTs caused by interaction with gold and platinum nanoparticles

Single-walled carbon nanotubes (SWNTs) have been coated with gold and platinum nanoparticles either by microwave treatment or by the click reaction. 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 attached to metal nanoparticles. This conclusion is also supported by the changes observed in the radial breathing mode (RBM) bands. Ab initio calculations reveal that semiconductor–metal transition occurs in SWNTs due to Coulombic charge transfer between the metal nanoparticles and the semiconducting SWNTs.