Interaction of S-histidine, an amino acid, with copper and gold surfaces, a comparison based on RAIRS analyses

The adsorption of S-histidine on gold and copper well-defined surfaces has been characterised by reflection absorption infrared spectroscopy (RAIRS), a surface technique that gives chemical as well as orientational information. Analyses were carried out in a UHV chamber. The RAIRS data are in agreement with the following conclusions. Under low pressure of histidine, 10−8 mbar, histidine molecules form an adsorbed molecular layer on Au (1 1 1) and Cu (1 1 0) surfaces. On gold, histidine mainly adsorbs through the depronated carboxylate group in a quasi-upright geometry that maintains the imidazole ring far from the surface. On copper, the histidine NH2 and COO− groups are involved in the interaction with the surface, with the cycle closer to the surface.