  Thick anatase films were fabricated on graphite substrates using a method of
anodic aqueous electrophoretic-deposition using oxalic acid as a dispersant.
Thick films were subsequently fired in air and in nitrogen at a range of
temperatures. The morphology and phase composition were assessed and the
photocatalytic performance was examined by the inactivation of Escherichia coli
in water. It was found that the transformation of anatase to rutile is enhanced
by the presence of a graphite substrate through reduction effects. The use of a
nitrogen atmosphere allows higher firing temperatures, results in less cracking
of the films and yields superior bactericidal performance in comparison with
firing in air. The beneficial effects of a nitrogen firing atmosphere on the
photocatalytic performance of the material are likely to be a result of the
diffusion of nitrogen and carbon into the TiO2 lattice and the consequent
creation of new valence band states.
