Catalytic inactivation of bacteria using Pd-modified titania

Pd and Pt-modified TiO2 were compared with un-modified TiO2 for the photocatalytic sterilization of Escherichia coli in water. Pd/TiO2 was found to work significantly faster than Pt/TiO2, and was also active in the absence of light; indicating an alternative mechanism to conventional titania photocatalysis. The Pd/TiO2 catalyst temporarily lost bactericidal activity after each use, but was re-activated by exposure to air prior to reuse. A direct correlation between oxidation state and antimicrobial activity was indicated for Pd/TiO2. XPS analysis confirmed the oxidation of Pd on the catalyst after exposure to air and the subsequent reduction when immersed in water.