Plasma-Induced Crystallization of TiO₂ Nanotubes

Facile crystallization of titanium oxide (TiO₂) nanotubes (NTs), synthesized by electrochemical anodization, with low pressure non-thermal oxygen plasma is reported. The influence of plasma processing conditions on TiO₂ NTs crystal structure and morphology was examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). For the first time we report the transition of amorphous TiO₂ NTs to anatase and rutile crystal structures upon treatment with highly reactive oxygen plasma. This crystallization process has a strong advantage over the conventional heat treatments as it enables rapid crystallization of the surface. Thus the crystalline structure of NTs is obtained in a few seconds of treatment and it does not disrupt the NTs' morphology. Such a crystallization approach is especially suitable for medical applications in which stable crystallized nanotubular morphology is desired. The last part of the study thus deals with in vitro biological response of whole blood to the TiO₂ NTs. The results indicate that application of such surfaces for blood connecting devices is prospective, as practically no platelet adhesion or activation on crystallized TiO₂ NTs surfaces was observed.