Surface enhanced Raman spectroscopic study of 2- and 3-chloro-thiophene in silver hydrosol

Abstract

Surface enhanced Raman spectra (SERS) of 2-chloro and 3-chlorothiophene molecules in silver sol have been investigated. It is observed that though the molecules are principally adsorbed on the metal surface through the sulfur atom, the chlorine atom is also involved in the adsorption process. Considering the surface selection rule based on image dipole theory the experimental results suggest that the orientation of the molecules on the metal surface is such that the thiophene ring plane is nearly normal to the surface with the C 3–C 4 bond making a large projection on the surface normal and standing on the C 2–C 3 bond edge nearer to the metal surface. Ring plane of the 3-isomer is however more inclined to the metal surface than that of 2-isomer. No oligomerization of the chlorothiophenes is indicated in the SER spectra.