Tunable functionality and toxicity studies of titanium dioxide nanotube layers

In this study, we have developed a simple process to fabricate scalable titanium dioxide nanotube layers which show a tunable functionality. The titanium dioxide nanotube layers were prepared by electrochemical anodization of Ti foil in 0.4 wt.% hydrofluoric acid solution. The nanotube layers structure and morphology were characterized using X-ray diffraction and scanning electron microscopy. The surface topography and wettability were studied according to the anodization time. The sample synthesized displayed a higher contact angle while the current density reached a local minimum. Beyond this point, the contact angles decreased with anodization time. Photo-degradation of acid orange 7 in aqueous solution was used as a probe to assess the photocatalytic activity of titanium dioxide nanotube layers under UV irradiation. We obtained better photocatalytic activity for the sample fabricated at higher current density. Finally we used the Ciliated Protozoan T. pyriformis, an alternative cell model used for in vitro toxicity studies, to predict the toxicity of titanium dioxide nanotube layers in a biological system. We did not observe any characteristic effect in the presence of the titanium dioxide nanotube layers on two physiological parameters related to this organism, non-specific esterases activity and population growth rate.