SERBS of free base porphyrin in laser-ablated colloids:: evidence for three different spectral porphyrin forms

We report a new spectral form of 5,10,15,20-tetrakis(1-methyl-4-pyridyl)porphyrin (H2TMPyP) observed in laser-ablated Ag colloids. The appearance of this form can be induced by the addition of thiosulfate ions to the Ag colloid-H2TMPyP system. Factor analysis of time-evolved SERBS spectra enabled us to extract a pure spectrum of this form that differs from previously reported SERBS spectra assigned to the free base and Ag+ metalated forms of the porphyrin. Referring to the well known ability of thiosulfate ions to remove silver cations from Ag surfaces, we tentatively attribute the new spectral form to H2TMPyP metalated by neutral silver. Copyright (C) 2002 John Wiley Sons, Ltd.