An investigation on fluorescence quenching of certain porphyrins by colloidal CdS

Certain porphyrin derivatives namely meso-tetraphenylporphyrin (TPP), meso-tetrakis(4-carboxyphenyl)porphyrin (TCPP), meso-tetrakis(4-sulfonatophenyl)porphyrin (TSPP) were examined as sensitizers for colloidal CdS. The interaction of these porphyrins and colloidal CdS were studied by absorption, infrared, steady state and time resolved fluorescence spectroscopy and transient absorption techniques. The apparent association constants (K_app) resulting from adsorption of porphyrins on CdS surface were calculated from both absorption and fluorescence studies and they agree well. Using all the spectroscopic measurements we confirmed that the interaction between porphyrins and colloidal CdS occurs through ground state complex formation and the quenching follows static mechanism.