TIME-DEPENDENT SERS OF PSEUDOISOCYANINE ON SILVER PARTICLES GENERATED IN SILVER BROMIDE SOL BY LASER ILLUMINATION

SERS spectra of pseudoisocyanine dye (PIC) in silver bromide sols show a strong time-dependence. The enhancement factor, in general, follows the formation (and destruction) of SERS-active colloidal silver in the silver halide sols by laser illumination during the Raman measurement. Changes in the relative intensities within a characteristic line triplet of the SERS spectrum show that the surface potential which is ''seen'' by the dye molecules shifts to more positive values with longer times. In particular, the values of the potential hint at the existence of Ag1 and Ag4...Ag6 clusters as SERS-active adsorption sites of the dye molecules in AgBr sols.