Molecular structure of cysteamine monolayers on silver and gold substrates: Comparative studies by surface-enhanced Raman scattering

Monolayers of cysteamine (2-aminoethanethiol) frequently work as linkage layers for adsorption of other molecules on metal surfaces. We compared the structure of cysteamine monolayers formed on gold and silver and the influence of various electrolytes on the structure of monolayers formed on both substrates. The monolayers formed on silver contain significantly higher portion of a trans conformer than monolayers on gold. Probably monolayers on silver are self-assembled in such a way that higher portion of the amino groups is unbonded to the surface, thus being available for attaching other molecules. The structure of cysteamine monolayers formed on gold is considerably more stable and resistive to the influence of electrolytes as compared to the silver substrate. The greater stability of the monolayers on Au surface was ascribed to the strong affinity of the amine groups toward this metal.