ABSTRACT
The photocatalyzed degradation of organic environmental pollutants in the presence of large bandgap semiconductors such as Titanium dioxide (TiO2) and Zinc oxide (ZNO) has become a subject of increasing study over the last decade. An important way to extend the response of the semiconductor is by photosensitization. The quenching is due to the strong adsorption of the sensitizer on the semiconductor particles. This long lived charge at the semiconductor surface is responsible for controlling the photocatalytic properties of the semiconductor. The chapter shows that Suwanee River fulvic acid can be used to sensitize colloidal TiO2 and ZnO by charge injection. The key question then that arises is whether such a charge trapped on the semiconductor would be accessible for charge transfer to another substrate, such as a potential environmental pollutant. The importance of humic substances lies in their ability to initiate the photochemical transformation of organic compounds in natural water and their eventual degradation.
