Low-temperature processing of thin films based on rutile TiO 2 nanoparticles for UV photocatalysis and bacteria inactivation

Using a low-temperature, simple, and economic processing technique, TiO2 nanoparticles (rutile phase) are immobilized in an inorganic matrix and then deposited on glass for bacteria inactivation in water. Using this low thermal budget method (maximum processing temperature of 220 C), thin films of immobilized TiO2 nanoparticles are obtained so that practical water decontamination after UV radiation is possible by avoiding the additional step of cat- alyst separation from treated water. In order to validate the photocatalytic activities of these TiO2 nanoparticles (pre- pared as thin films), they were tested for bacteria inactiva- tion in water under UV-A radiation (k ( 365 nm), while extensive characterizations by dynamic light scattering, X-ray diffraction, ultra violet-visible absorption spectros- copy, fourier-transform infra red spectroscopy, and profil- ometry were also carried out. Despite previous reports on the low or lack of photocatalytic activity of rutile-phase TiO2, inactivation of Escherichia coli in water was observed when thin films of this material were used when compared with the application of UV radiation alone. Physical character- ization of the films suggests that size and concentration- related effects may allow the existence of photocatalytic activity for rutile-TiO2 as long as they are exposed under UV-A radiation, whereas no effect on bacteria inactivation was observed for thin films in the absence of TiO2 or radi- ation. In brief, a low thermal budget process applied to thin films based on TiO2 nanoparticles has shown to be useful for bacteria inactivation, while possible application of these films on widely available substrates like polyethylene tere- phthalate materials is expected.