Quantitative surface-enhanced resonance Raman scattering analysis of methylene blue using silver colloid

Quantitative analysis of methylene blue (MB) has been performed with Surface Enhanced Raman Scattering, SERS, using citrate reduced silver colloid activated with NaCl. In this study, the combination of SERS occurring at the proximity of the plasmon surface and of resonance Raman with excitation wavelength matched to the maximum absorbance of the molecule being analyzed, was successfully applied to maximize the Raman scattering intensity. The surface-enhanced resonance Raman scattering (SERRS) spectra of aqueous solutions of the dye at various concentrations were collected in right-angle scattering geometry configuration which results favorable when nanocolloidal dispersions are used. The MB concentration was correlated with the intensity of the peak centered at 1,625cm(-1) in the SERRS spectrum and this correlation resulted in an extremely sensitive quantitative investigation of the MB with limit of detection in pM level. Among others, this method can be easily applied for the examination of both the selectivity of waste water purification membranes for relevant small molecular weight contaminants or/and the solar photocatalytic effectiveness of such membranes for the degradation of pertinent pollutants by their quantitative assessment in the permeate at very low concentration range.