SERS studies on the structure of thioglycolic acid monolayers on silver and gold

Chemisorption of thioglycolic acid (TGA) on silver and gold has been studied using surface-enhanced Raman scattering. We found that the strength of TGA strongly decreased after adsorption. Significantly more decreased strength was observed for TGA adsorbed on Au. The average conformation of adsorbed TGA molecules depends on the kind of the substrate and on degree of dissociation of TGA. The higher portion of TGA molecules adopts trans conformation when layers are formed on the Ag substrate and when more carboxylic acid groups are deprotonated. The ratio of gauche to trans conformers of TGA molecules significantly changed during the incubation on silver. In the first stage of incubation the relative amount of a gauche conformer increases, but after about 1 h the gauche conformer starts to disappear. The average conformation of TGA adsorbed on the gold substrate did not change during the incubation.