Quantitative determination of the surface concentration of phenazine adsorbed on silver colloidal particles and relationship with the SERS enhancement factor

SERS spectra of phenazine adsorbed on silver colloids have been investigate d. For ligand concentrations from 10(-4) to 10(-6) M, it was possible to ob tain the adsorption isotherm of phenazine by absorption measurements in the UV-visible region. Filtration of the ligand/hydrosol systems through suita ble filters containing aluminum oxide membranes allowed a complete removal of the metal particles from the filtrate. Determination by spectral analysi s of phenazine still dissolved in solution provided a quantitative estimate of the ligand adsorbed on the metal particles at different analytical conc entrations. Colloids activated by chloride anions were used in these experi ments to improve properly the Raman signal of the adsorbate. The results in dicate that the SERS enhancement exhibits factors up to 10(6), in agreement with the previous theoretical and experimental findings.