Guanine adsorption on the Cu(110) surface

The adsorption of guanine on Cu(110) has been studied by soft X-ray photoelectron spectroscopy (XPS) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The valence band spectra, carbon and nitrogen 1s XPS and N K-edge absorption spectra were measured for a thin film, sub-monolayer and saturation coverage. We show that hydrogen bonding causes a significant core level shift in the thin film. At saturation coverage, guanine is tilted at 70° with respect to the surface, and bonds through the N1 nitrogen atom. On reducing the coverage, the orientation changes and the tilt angle of the molecular plane is reduced. For both coverages, guanine is singly deprotonated at the N1 site, and annealing to a higher temperature (500 K) is probably accompanied by further deprotonation of the amino groups.