Surface-enhanced Raman Scattering （SERS） of the Spectral Sensitizing Dyes in Silver Chloride and Silver Sulfide Sols

The surface-enhanced raman scattering （SERS） spectra of 1-ethyl-3’-methyl-2-thiacyanine iodide （D-1）, 1, 1’-diethyl-2, 2’-cyanine iodide （D-2） and crystal violet （CV） adsorbed on the surface of the silver chloride and silver sulfide colloids have been recorded and discussed. The amount of dye adsorbed on silver chloride was measured by using the phase seperation technique and the spectral analysis method. Sodium thiosulfate can significantly quench the SERS of the D-2 molecules and increase the amount of D-2 adsorbed on silver chloride. On the other hand , ferricyanide can not quench the SERS of D-2. The contrary results were obtained when silver chloride colloids were displaced by silver colloids. The foregoing experimental results suggest that the surface Ag⁺ of the silver chloride colloids plays an important role in the adsorption as well as in the SERS of the D-2 molecules, which is associated with the SERS-active sites, and the chemical enhancement mechanism takes an important role in the SERS of the spectral sensitizing dyes on silver chloride and silver sulfide colloids.
The mechanism of desensitization has been examined by using the SERS technique. It is found that the sensitizing dye D-2 is displaced from the surface of the silver chloride colloids by the desensitizing dye CV. On the other hand, the sensitizing dye D-1 is not displaced from the surface of the silver chloride colloids by the desensitizing dye CV.