INVESTIGATION ON THE BEHAVIOR OF PORPHYRINS AT THE SURFACE OF THE COLLOIDAL SILVER PARTICLES

The behavior of meso-tetra(4'-hydroxyphenyl) porphyrin (T(4-HP)P) and o-5-(4'-hydroxyphenyl)-10,15,20-triphenylporphyrin (HPTPP) in a Ag sol system was investigated by W-vis spectra, surface enhanced Raman scat tering (SERS), fluorescence spectra and the measurements of luminescen ce lifetime. There was an obvious SERS effect when the porphyrins were adsorbed on the surface of colloidal silver particles. Meanwhile, a n ew peak was observed at about 460 nm in the absorption spectra. The ev idence suggests that T(CHP)P and HPTPP chemisorbed on the particle sur face of Ag sol to produce complex like metalloporphyrins. The apparent association constants for the two porphyrins and silver sol were 3.16 x 10(4) M-1, 2.79 x 10(4) M-1, respectively. It was found that silver sol was a fluorescence quencher by which above 90% of the fluorescenc e emission of T(4-HP)P and HPTPP could be quenched. The mechanism for fluoresence quenching was proposed to be a static process based upon t he measurements of fluorescence lifetimes. (C) 1997 Elsevier Science S .A.