Abstract

Surface enhancement of resonance Raman scattering (SERRS) from a series of laser dyes (sodium fluorescein, rhodamine 6G, rhodamine 110, rhodamine B, DCM, and coumarins) adsorbed on chemically deposited silver film is presented. The observed Ag–O, Ag–N spectral lines at ~200 cm⁻¹ confirm the chemisorbed nature of most dye molecules on the Ag surface. An assignment of the SERRS spectra of sodium fluorescein at various pH values verifies the structural and configurational changes of their cationic, neutral, and anionic forms and implies their different interaction behavior with the Ag surface. Sodium fluorescein is found to be a good surface fluorescence probe molecule owing to the sensitive change of its quantum efficiency with the pH value in solution. On Ag film, the fluorescence of sodium fluorescein becomes more intense as its quantum efficiency goes down. Comparing the fluorescence of laser dye on Ag film and a silica surface, we find that it is quenched on very low coverage Ag film and is enhanced on a moderate coverage Ag film.

© 1987 Optical Society of America