Influence of electrolytes on the structure of cysteamine monolayer on silver studied by surface‐enhanced Raman scattering

Abstract

Abstract Monolayers of cysteamine (2‐aminoethanethiol) frequently work in aqueous solutions of electrolytes as linkage layers for adsorption of other molecules on metal surfaces. We determined the influence of various ions on the structure of the cysteamine monolayer with surface‐enhanced Raman scattering (SERS). The surrounding (pH, electrolytes) considerably influences the conformation of adsorbed cysteamine molecules. Direct spectral evidence of the interaction of cysteamine with an Ag surface through AgN bonds in the gauche conformation is given. It was found that chlorides and iodides significantly increase the proportion of the gauche conformer. Probably these anions additionally stabilize the gauche conformer by the formation of hydrogen bonds with NH 2 groups in addition to the direct NAg bond. Raman measurements also revealed that cations, which can form strong coordination bonds with amino groups (Cu 2+ , Ni 2+ or Co 2+ ), change the structure of the cysteamine layer by transforming the trans into a gauche conformer. In contrast, an increase in the proportion of trans conformers is observed with increase in the concentration of H + in the ambient electrolyte. Possible explanations for these experimental findings are discussed. Copyright © 2001 John Wiley & Sons, Ltd.