Spectra of surface-enhanced Raman scattering of 1-propanethiol and 3-mercaptopropionic acid chemisorbed on thin silver films

The influence of chemisorption and intermolecular Van der Waals interaction s on the formation of surface-enhanced Raman spectra of 1-propanethiol and 3-mercaptopropionic acid coated as self-organized monolayers on vacuum-depo sited thin silver films and thin silver films annealed at high temperatures is studied. Optical properties of films of both types are found to he stro ngly affected by the chemical modification, which is associated with peculi arities of the monolayer formation. It is shown that the reorganization of the substrate surface can be associated with intense repulsion between alka ne chains of thiol when the distance between them decreases in comparison w ith the distance typical of crystalline paraffins. Conclusions on the prese nce and the nature of packing defects of short-chain thiols on the substrat e surface are made on the basis of the analysis of Raman and surface-enhanc ed Raman spectra. It is shown that the interaction between the first (propa nethiol) and the second (pyruvate) monolayers near the silver surface in th e water phase results in the reorganization of the first monolayer, in whic h conformers of propanethiol in the gauche-conformation with respect to the C(1)-C(2) bond prevail. (C) 2000 MAIK "Nauka/Interperiodica".