The effect of surface symmetry on the adsorption energetics of SCH3 on gold surfaces studied using Density Functional Theory

Adsorption of methanethiol onto the three, high symmetry gold surfaces has been studied at the density functional level using a linear combination of atomic orbitals approach. In all three cases the bond energy between the thiolate radical and surface is typical of a covalent bond, and is of the order of 40 kcal mol−1. For the (1 1 1) surface the fcc hollow site is slightly more stable than the bridge site. For the (1 0 0) surfaces the four-fold hollow is clearly the most stable, and for the reconstructed (1 1 0) surface the bridge/edge sites either side of the first layer atoms are preferred. The calculated differences in binding energy between the three surfaces indicate that the thiolate will preferentially bind to the Au(1 1 0) or (1 0 0) before (1 1 1) surface, by about 10 kcal mol−1. The (1 1 0) surface is slightly more favourable than the (1 0 0), although the energy difference is only 3 kcal mol−1. The results suggest the possibility of selectively functionalising the different facets offered by a gold nanoparticle.