Investigation on the behavior of porphyrins at the surface of the colloidal silver particles

Abstract

The behavior of meso-tetra(4′-hydroxyphenyl) porphyrin (T(4-HP)P) and meso-5-(4′-hydroxyphenyl)-10,15,20-triphenylporphyrin (HPTPP) in a Ag sol system was investigated by UV-vis spectra, surface enhanced scattering (SERS), fluorescence spectra and the measurements of luminescence lifetime. There was an obvious SERS effect when the porphyrins were adsorbed on the surface of colloidal silver particles. Meanwhile, a new peak was observed at about 460 nm in the absorption spectra. The evidence suggests that T(4-HP)P and HPTPP chemisorbed on the particle surface of Ag sol to produce complex life metalloporphyrins. The apparent association constants for the two porphyrins and silver sol were 3.16 × 10 4M −1, 2.79 × 10 4M −1, respectively. It was found that silver sol was a fluorescence quencher by which above 90% of the fluorescence emission of T(4-HP)P and HPTPP could be quenched. The mechanism for fluorescence quenching was proposed to be a static process based upon the measurements of fluorescence lifetimes.