Enhanced Photocatalytic Activity of 3,4,9,10-Perylenetetracarboxylic Diimide Modified Titanium Dioxide Under Visible Light Irradiation

A method to improve the photocatalytic activity of titanium dioxide by modification with a sensitizer and a metal oxide is proposed. To achieve this goal, we used metal oxides as dopants. In particular, CaWO4 and Gd2O2S:Tb were used because their 2.6 eV and 2.2 eV band gap energy and optical properties have a large positive effect on photocatalysis. The improvement in the photocatalytic activity of TiO2 modified with Gd2O2S:Tb under ultraviolet light irradiation is described in a previous study. The present work focuses on the sensitization of metal oxide-modified TiO2. Having observed the ultraviolet-visible absorption spectra of 3,4,9,10-Perylenetetracarboxylic diimide in the wide visible-light region from 400 nm to 650 nm and the broad peaks in its photoluminescence spectra at 695 nm and 717 nm, we decided to use this perylene dye to sensitize modified TiO2 to enhance its activity as a visible-light harvesting photocatalyst. We also explored the positive effects thin-film surface changes stemming from ultraviolet pre-treatment have on photocatalytic activity. Finally, we subjected several metal oxide-modified TiO2 products sensitized by the perylene dye to ultraviolet pre-treatment, obtaining the most active photocatalysts.