Interaction of water‐soluble tetrakis‐(1‐methyl‐4‐pyridiniyl)‐porphyrin and CdS naonoparticles

The interaction between positively charged porphyrin TMPyP(4) (tetrakis-(1-methyl-4-pyridiniyl) porphyrin) and negatively charged surface of colloidal CdS nanoparticles has been studied by absorption spectrum, fluorescence spectroscopy, and time-correlated single-photon-counting methods. Addition of CdS colloid to a TMPyP(4) solution leads to TMPyP(4) adsorption onto the surface of CdS colloid with an apparent association constant of 4643 L/mol. This adsorption results in distinct changes in absorption spectrum of TMPyP (4) and the quenching of its′ fluorescence, but the biexponential fluorescence decay changes hardly. Nearly 90% of the fluorescence of 5 × 10−6 mol/L TMPyP(4) can be quenched with 1.5 × 10−4 mol/L CdS colloid. These spectral changes are attributed to the formation of a certain form complex TMPyP(4)-CdS.