Adsorption of Cysteine on Cu(110) Studied by Core-Level Photoelectron Spectroscopy

Abstract

Adsorption and ordering of cysteine molecules on Cu(110) surface have been studied by photoelectron spectroscopy using synchrotron radiation and low-energy electron diffraction (LEED). Analysis of S 2p, N 1s, O 1s, and C 1s core levels as a function of the cysteine coverage on Cu(110) reveals quite different behavior from the previously studied case on a Au(110) surface. At low coverages there evolve sequentially two types of thiolates with the S 2p binding energy difference of 0.85 eV. The relative population of the two thiolates induces a structural change in the ordering from 2 × 1 to c(2 × 2). Only above half the saturation coverage the LEED pattern becomes diffuse and a configurational change of the molecule by protonation of the functional groups occurs. Such an unusual evolution of the cysteine adsorption on the Cu(110) surface is discussed in relation to chemical reactions and possible molecular rearrangement on the surface.