Electronic and Vibration Spectra of Hydrogenated Carbon Single‐Wall Nanotubes

Abstract

Carbon single‐wall nanotubes (SWNTs) were loaded with 5.4 wt.% H by exposing to a hydrogen pressure of 50 kbar at 500°C. Investigation of the optical transmission spectra showed that the hydrogenation significantly suppressed the high‐frequency conductivity σ of free carries in the SWNTs and also eliminated the band‐to‐band electronic transitions. Instead, a narrow line of the C‐H stretching vibrational mode appeared at 2845 cm−1. A gradual removal of hydrogen from the hydrogenated SWNTs by vacuum annealing at T≥500°C resulted in an approximately linear decrease in the intensity of this line with decreasing hydrogen content. This evidenced that most H atoms in the hydrogenated SWNTs were covalently bonded to the carbon atoms. The complete removal of hydrogen by vacuum annealing at 700°C partly restored σ and the intensity of the electronic transitions characteristic of the initial SWNTs.