Ab initio DFT study of 6-mercapto-hexane SAMs: effect of Au surface defects on the monolayer assembly

作者：Hu Hang; Reven Linda; Rey Alejandro D^*

来源：Molecular Simulation, 2013, 39(4): 292-298.

DOI：10.1080/08927022.2012.720018

• density functional theory
• self-assembled monolayer
• alkanethiol
• gold (001)

This paper reports a novel ab initio density functional theory (DFT) simulation approach to the study of surface defects in self-assembled monolayers (SAMs) on gold (001) surfaces. Surfaces defects can cause changes in gold atom spacing and the ligand footprint. DFT calculations of 6-mercapto-hexane on Au(001) surfaces have been performed as a function of ligand footprints of 18, 20, 22, 24 and 26 angstrom 2, using a slab geometry and periodic boundary conditions with varying gold atom spacing. The simulation results indicate that as the ligand packing density increases, the position of ideal binding sites changes from fcc to bridge sites. The packing density of 24 angstrom 2 corresponds to the highest binding energy and to a 28.85 degrees cant angle. These results are in good agreement with the experiments from ligand-capped gold nanoparticles. The simulation results also prove that the SAM structure of short-chain alkanethiols on gold is dominated by surface interactions rather than ligand interactions. The electron density mapping study confirms this observation, where only the top two layers of gold atoms contributed charge transfer to sulphur atom and no charge transfer was observed from the alkane chain.

• 出版日期2013-4-1
• 单位McGill