Abstract
l-Cysteine has been deposited on Au(111) surfaces from the solution phase. Chemical and structural information on the l-cysteine/Au(111) interface have been obtained by X-ray photoelectron spectroscopy (XPS) and scanning tunnelling microscopy (STM). XPS measurements provided a chemical characterisation of the interface. The deconvolution of the Au4f and S2p core level regions reveals a peak splitting, which can be explained by the formation of a chemical bond between the cysteine thiol group and the gold surface. The analysis of the N1s spectrum indicates that l-cysteine is present in the zwitterionic state. The STM structural characterisation performed in air at room temperature reveals that the molecular chemisorption results in the lifting of the 22× 3 gold reconstruction accompanied by the formation of depressions, a few nm in size, one gold layer in depth, as in alkanethiol/Au(111) systems. Molecular resolution images show that the l-cysteine overlayer forms a hexagonal lattice, which, in a few regions, presents a striped modulation.
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