Plasma electrolytic titanium oxide applied for pathogenic bacteria inactivation

Photocatalysis over TiO₂ substrates is widely used in effluent treatment specially for organic compounds and for inactivation of pathogenic microorganisms. In the present work, TiO₂ coatings were synthesized by plasma electrolytic oxidation (PEO) and its pathogenic bacteria inhibitory photoactivity was investigated. The photocatalytic activity of TiO₂ coatings was investigated for the inactivation of Staphylococcus aureus and Salmonella bongori and the results were correlated with pore diameter and crystallite size. It was observed that both morphology and microstructure have an important role in the antibacterial photoactivity. The results show the larger the crystallite size and pore diameter the greater the photoactivity of the material. Porous materials that have a smaller pore diameter than the microorganism to be inactivated have low photoactivity. On the other hand, films that have pores with a diameter of the order or larger than the size of the microorganism to be inactivated present greater photocatalytic activity, once its pores allow the entrance and internal adsorption of the microorganisms, leading to the rupture of the cell membrane. Thus, in order to not sub-utilize the photocatalysts surface area, TiO₂ coatings for using in microorganism inactivation must be synthesized with pore diameter bigger than the size of the microorganism.