Photoelectron Spectroscopic Study of Electronic Structures of l-Cysteine

概要

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The valence band structure of l-cysteine films was investigated by ultraviolet photoelectron spectroscopy (UPS) in the photon energy range of 40–100 eV. Smooth thin films were produced by vacuum evaporation and characterized by X-ray photoelectron spectroscopy, atomic force microscopy, and Raman scattering spectroscopy. The photon energy dependence of the UPS spectra indicates that electronic states close to the valence band maximum may be attributed to sulfur, while the other states in the higher-binding-energy region may be attributed to carbon, nitrogen, and oxygen. Molecular orbital calculation was performed on seven possible geometries of l-cysteine. The observed UPS spectrum is in good agreement with the simulated one in terms of the C3 geometry of l-cysteine. It is concluded that the sulfur-originated electronic state is located at the valence-band maximum, indicating that cysteine is one of the useful and promising materials in future bioelectronics.
2010-03-15