Optical and photophysical studies on porphyrin doped TiO2 matrixes

The extinction coefficient, k(E), and refractive index, n(E), of zinc meso-tetra porphyrin (ZnP) when incorporated into nanoporous titania were measured in the range 1.7-4.2 eV, by using a method that accounts for both the microstructure and morphology of the semiconductor matrix. Optical and fluorescence spectra reveal the presence of a specific interaction between the porphyrin and TiO2 whereby ZnP becomes anchored onto the surface of porous titania in monomeric and as aggregated forms. Radiative decays and fluorescence quantum yields were determined for the two forms of ZnP. The work also included optical and fluorescence studies of ZnP bound to poly(4-vinylpyridine) (PVP). In this case formation of a ground-state complex, ZnP-PVP, prevents aggregation of the porphyrin. The complex is fluorescent, with two distinct radiative decays determined by the micropolarities of the PVP copolymer.