  In this work, we have developed economic process to elaborate scalable
titanium dioxide nanotube layers which show a tunable functionality. The
titanium dioxide nanotube layers was 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 was studied according to the
anodization time. The sample synthesized while the current density reached a
local minimum displayed higher contact angle. Beyond this point, the contact
angles decrease with the anodization time. Photo-degradation of acid orange 7
in aqueous solution was used as a probe to assess the photo-catalytic activity
of titanium dioxide nanotube layers under UV irradiation. We obtained better
photocatalitic activity for the sample elaborate at higher current density.
Finally we use 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 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.
