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.

Keywords:

• Carbon nanotubes
• hydrogen
• optical transmission spectra
• diffuse reflection

Acknowledgments

The work was supported by the RFBR grant No. 05‐03‐33119 and RAS Programs “New materials and structures” and “Influence of the atomic and electron structure on the properties of condensed media.”