Effect of Fullerene Encapsulation on Radial Vibrational Breathing-Mode Frequencies of Single-Wall Carbon Nanotubes

We investigate the effects of C-60 fullerene encapsulation on the radial breathing mode (RBM) of semiconducting single-wall carbon nanotubes (SWCNTs) under tunable laser excitations. The changes in the RBM frequencies after C-60 insertions show characteristic behavior; higher frequency shifts are observed in the case of smaller diameter tubes (d(t)less than or similar to 1.32 nm) and lower frequency shifts, in the case of larger diameter tubes (d(t)greater than or similar to 1.32 nm). The observed frequency shifts are satisfactorily explained by the diameter-dependent interaction between the encapsulated C-60 and the host SWCNTs.