Thioglycolic acid on the gold (111) surface and Raman vibrational spectra

TL;DR

This study investigates how thioglycolic acid and its derivatives interact with the Au(111) surface, revealing their orientations and vibrational spectra, and proposing a mechanism for their deposition behavior.

Contribution

It provides detailed insights into the adsorption configurations and vibrational spectra of thioglycolic acid derivatives on Au(111), advancing understanding of surface interactions.

Findings

Molecules lie down on the substrate at low coverage.

Deprotonation alters molecular orientation on the surface.

Calculated Raman spectra identify atomic contributions to vibrational modes.

Abstract

The interaction of thioglycolic acid with the Au(111) surface is investigaged, and it is found that at the low coverage the molecule lies down on the substrate. If the mercaptan-hydrogen atom is eliminated, the resulting SCH_2COOH molecule is randomly oriented on the surface. If the carboxylic acid group in the HSCH_2COOH molecule is deprotonated instead, the HSCH_2COO^ molecule lies down on the surface. However, when the mercaptan-hydrogen atom in the HSCH_2COO^- molecule is removed, the resulting SCH_2COO^- molecule rises up to a certain level on the substrate. The calculated Raman vibrational spectra decipher which compounds and atomic displacements contribute to the corresponding frequencies. We thus propose a consistent mechanism for the deposition of thioglycolic acid on the Au(111) surface.