Spectroscopic Investigations of Porphyrin-TiO 2 Nanoparticles Complexes.

This study presents the spectral characterization of TiO 2 nanoparticles (NPs) functionalized with three porphyrin derivatives: 5,10,15,20-(Tetra-4-aminophenyl) porphyrin (TAPP), 5,10,15,20-(Tetra-4-methoxyphenyl) porphyrin (TMPP), and 5,10,15,20-(Tetra-4-carboxyphenyl) porphyrin (TCPP). UV-Vis absorption and Fourier transform infrared spectroscopy-attenuated total reflection (FTIR-ATR) spectroscopic studies of these porphyrins and their complexes with TiO 2 NPs were performed. In addition, the efficiency of singlet oxygen generation, the key species in photodynamic therapy, was investigated. UV-Vis absorption spectra of the NPs complexes showed the characteristic bands of porphyrins. These allowed us to determine the loaded porphyrins on TiO 2 NPs functionalized with porphyrins. FTIR-ATR revealed the formation of porphyrin-TiO 2 complexes, suggesting that porphyrin adsorption on TiO 2 may involve the pyrroles in the porphyrin ring, or the radicals of the porphyrin derivative. The quantum yield for singlet oxygen generation by the studied porphyrin complexes with TiO 2 was higher compared to bare porphyrins for TAPP and TMPP, while for the TCPP-TiO 2 NPs complex, a decrease was observed, but still maintained a good efficiency. The TiO 2 NPs conjugates can be promising candidates to be tested in photodynamic therapy in vitro assays.