Ag+ and Ag(0) coordination of porphyrins adsorbed on laser-ablated Ag colloids monitored by surface-enhanced resonance Raman scattering spectroscopy

The paper demonstrates the suitability of surface-enhanced resonance Raman scattering (SERRS) spectroscopy to monitor silver coordination of free base 5,10,15,20-tetrakis(1-methyl-4-pyridyl) porphyrin adsorbed on the Ag colloidal surface. Our approach based on factor analysis (FA) allows us to analyze time development of SERRS spectra in terms of varying content of particular porphyrin forms. Also their SERRS spectra can be isolated even if none of them is present singularly in any SERRS spectrum. Depending on the chemical properties of our systems, SERRS spectra of two different porphyrin metalated forms have been obtained: Ag+ and Ag(0) metalated. The latter form has been found to be evoked by pretreatment of the laser-ablated Ag colloids by the thiosulfate ions. The metalation kinetics obtained show a substantially slower metalation by Ag(0) than that by Ag+ cations.