Electronic structures and spectroscopic regularities of phenylene-modified SWCNTs

The equilibrium geometries and electronic structures for a series of single-wall carbon nanotubes (SWCNTs) modified with phenylene were studied using the density functional theory (DFT) at the B3LYP/6-31G(d) level. Of the four configurations of the phenylene-modified SWCNTs, the v-configuration in which the bond is perpendicular to the main axis of the SWCNT is the most thermodynamically stable. The increase in radii of the modified SWCNTs generally leads to a decrease in the energy gaps. The first absorptions in the electronic spectra of the modified SWCNTs compared with those in the electronic spectra of pristine SWCNTs are basically red-shifted. The chemical shifts of bridged carbon atoms connected with phenylene in the v-configuration are shifted downfield relative to those of the pristine SWCNTs. The aromaticity of the rings in SWCNTs is improved owing to the addition of phenylene.