Electron doping of small-diameter carbon nanotubes with exohedral fullerenes

The interaction between carbon nanotubes (CNTs) and exohedral fullerenes, which represent two types of carbon allotropes with extraordinary properties, has received little attention so far. The effect of exohedral fullerenes on CNTs’ electronic properties is essentially unknown. We report the electron doping of small-diameter semiconducting single-walled CNTs (SWNTs) with fullerenes such as 1-(3-methoxycarbonyl)propyl-1-$phenyl[6,6]C61$ ([60]PCBM). The resulting [60]PCBM-doped SWNTs demonstrate significantly enhanced electrical conductivity while still retaining characteristics of semiconducting nanotubes. Polymer nanocomposites based on air-stable, $n$-doped SWNTs show a (15–22)-fold enhancement in electrical conductivity compared with nanocomposites based on undoped SWNTs at the same nanotube loading level.