Diameter-Dependent Band Gap Modification of Single-Walled Carbon Nanotubes by Encapsulated Fullerenes

Band gap photoluminescence (PL) of single-walled carbon nanotubes (SWCNTs) encapsulating C-60 fullerenes (nanopeapods) is examined over a wide range of diameters (similar to 1.25-1.55 nm). The encapsulated fullerenes induce characteristic PL peak shifts that strongly depend on the tube diameter (d(t)), and the 2n + m family type (type I [mod(2n + m, 3) = 1] and type II [mod(2n + m, 3) = 2]). This behavior can be explained by the strain-induced band gap shifts due to the C-60 insertion and the hybridization between the electronic states of SWCNTs and C-60. The present results provide significant insights into band gap engineering of SWCNTs in future nanodevices.