Bactericidal activity of nitrogen-doped metal oxide nanocatalysts and the influence of bacterial extracellular polymeric substances (EPS)

The antibacterial effect of nitrogen-doped TiO2 and ZrO2 were tested on Escherichia coli and biofilm heterotrophic bacteria under solar light illumination. The rates of photocatalytic inactivation for biofilm bacteria with soluble extracellular polymeric substances (EPS) stripped off and E. coli bacteria were found to be higher than those of the biofilm bacteria with intact EPS. Measurements of both bacterial count and cellular components (carbohydrate and protein) revealed that EPS play an important role in controlling the kinetics of solar-induced photocatalysis. TiO2−xNx and ZrO2−xNx doped with ethylenediamine as the nitrogen source showed improved photoactivity compared with TiO2−xNx using ethanolamine as the nitrogen source.