Surfactant-Aided Surface-Enhanced Resonance Raman Spectroscopic Study of Some Anionic Dye Molecules

Abstract

Attempts to observe surface-enhanced Raman scattering (SERS) or surface-enhanced resonance Raman scattering (SERRS) of Eosin B, Evans Blue and Cu(II)PCS dyes using radiation from an argon ion laser 514 and 457 nm for excitation failed. However, in the presence of an appropriate amount of a cationic surfactant such as dodecyltrimethylammonium bromide and cetyltrimethylammonium bromide, the dye molecules exhibit the SERRS effect. UV–visible spectroscopy was found to be useful to understand better the activation behavior of the surfactants. From the UV–visible spectroscopic data, it is noted that the surfactant molecules cause aggregation of silver sols and interact with the dye molecules. The primary requirements for the surfactant to activate the surface-enhanced Raman (SER) effect of the anionic dye are the positive charge and the carbon chain length of the surfactant. Such a surfactant activation makes possible the observation of SER spectra of molecules which are not SERS-active under normal conditions.