TIME-DEPENDENCE OF THE SURFACE-ENHANCED RAMAN-SCATTERING FROM CRYSTALVIOLET ADSORBED ON AG THIN-FILMS

Surface enhanced Raman scattering from crystal violet molecules adsorb ed on Ag thin films was studied employing the attenuated total reflect ion configuration. Systematic variations of the enhanced Raman intensi ty with time were observed on the samples in which the crystal violet molecules were accumulated into aggregated clusters. The intensity fir st progressively increases to reach a maximum value, stays at the maxi mum for certain periods of time, then gradually decreases to a plateau , and stabilizes. The intensity variation period is different from one sample to the others, and it can take as long as several weeks before the intensity stabilizes. On the other hand, no intensity variation w as observed on the samples in which the crystal violet molecules were less stacking and uniformly distributed over the film surface. We attr ibute the observed variation of the enhanced Raman intensity to the re distribution of the. crystal violet molecules adsorbed on the films.