Sensitization of TiO2with phthalocyanines. Part 1.—Photo-oxidations using hydroxoaluminium tricarboxymonoamidephthalocyanine adsorbed on TiO2

Abstract

Hydroxoaluminium tricarboxymonoamidephthalocyanine has been adsorbed on TiO₂(Degussa P-25) particles. Water suspensions and solid samples were analysed by SEM and by IR, visible extinction, diffuse reflectance and fluorescence spectroscopy. Visible spectra showed that the dye is not highly aggregated on the surface. Fluorescence was completely quenched by the semiconductor. The sample is stable toward visible irradiation. The photocatalytic activity of the modified semiconductor for transformation of different substrates under visible irradiation in the phthalocyanine Q-band has been tested. While EDTA, oxalic acid and benzoquinone did not show any changes after irradiation, photooxidation of KI, phenol, thiophenol, 4-chlorophenol, hydroquinone and salicylic acid was observed. The analysis of the results as a function of the substrate redox potential suggests that the radical cation of the phthalocyanine, produced by electron injection of the dye into the TiO₂ conduction band, is the species responsible for the oxidation of the substrates. No reaction was found, at least for phenol, when TiO₂ free of AlTCPc was irradiated under the same conditions.