Quenching and enhancing of SERS of methyl orange after the addition of chlorine and nitrate anions

The influence of Cl− and NO3− anions on surface enhanced Raman scattering (SERS) of methyl orange adsorbed on “chemical pure” silver colloids was studied. It was found that NO3− could give rise to a large enhancement of SERS of methyl orange, while Cl− could obviously weaken the SERS intensity of this molecule. Both quenching and enhancing effects were discussed and compared with each other. It indicated the coadsorbed process of these adsorbed species, and different adsorption behaviors of the molecules on silver surface directly resulted in the difference. In addition, the results of TEM pictures and UV–visible spectral experiments have also confirmed the conclusion above.