Surface-enhanced Raman scattering of benzyl phenyl sulfide in silver sol: Excitation-wavelength-dependent surface-induced photoreaction

Ag sol prepared by the citrate-reduction method is a promising surface-enhanced Raman scattering (SERS) substrate that can be activated not only by 514.5 nm radiation but also by 568 nm and 632.8 nm radiation. Using these facts, the SERS of benzyl phenyl sulfide (BPS) in silver sol is revisited to assess the excitation-wavelength dependence of the C-S bond scission of BPS on Ag to produce surface-bound benzenethiolate. The SERS spectral features clearly indicate that the C-S bond cleavage of BPS on Ag occurs far more favorably under green light at 514.5 nm than under red light at 632.8 nm. The laser power-dependence study suggests further that the photodissociation of BPS proceeds on Ag via an initial single-photon absorption process rather than a multiphoton absorption one.