Adsorption of methylene blue and its N-demethylated derivatives on the (111) face of coinage metals: The importance of dispersion interactions.

Abstract

The adsorption of methylene blue and its N-demethylated derivatives on the (111) surface of three coinage metals is investigated using density functional theory with and without the inclusion of dispersion interactions. It is shown that the adsorption of these dye molecules on the metal surfaces can be largely classified as physisorption as the adsorption energy is dominated by dispersion interactions. While the molecules are found to adsorb on Au and Ag parallel to the surface with molecular geometries basically unaltered, the adsorption on Cu(111) features a butterfly configuration, accompanied by the largest adsorption energies among the three metal surfaces. The significant covalent character on Cu(111) is analyzed from the perspective of electronic structure.