Studies of Carbon Nanotubes and Fluorinated Nanotubes by X-ray and Ultraviolet Photoelectron Spectroscopy

Carbon single-walled nanotubes (SWNTs) and fluorinated SWNTs (F-SWNTs) were investigated by core and valence band X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). The core spectra were interpreted by chemical shift calculations based upon CNDO calculations, and the valence band spectra were calculated using ab initio molecular orbital calculations. Both calculations used various molecules representing different structural models for SWNTs and F-SWNTs. Core XPS studies of SWNTs showed carbon and small amounts of chemisorbed oxygen, while F-SWNTs showed a C 1s region split into four principal components with peaks shifted by 1.25, 4.00, and 7.20 eV from the principal carbon peak. The valence band showed characteristic features that could be interpreted by calculated spectra. The model for SWNTs consisted of a carbon framework with terminating hydrogen atoms. This study indicates that it is possible to see significant differences in the photoelectron spectra for different nanotube structures, especially in the case of fluorinated nanotubes. The fluorinated nanotubes of this study give the best agreement with the calculated spectra for an armchair arrangement nanotube.