THE SURFACE WETTABILITY PROPERTIES OF TiO₂ NANOTUBE ARRAY FILMS WITH DIFFERENT OXYGEN VACANCY CONCENTRATION

The TiO₂ nanotube array films were prepared by anodization，then annealed at different temperatures under different atmospheres to obtain oxygen-deficient TiO₂ nanotube array films with different oxygen vacancy concentration.The experimental results showed that with the increase of the annealing temperature all the contact angles of the samples decreased gradually and present super hydrophilic state（contact angle very close to 0°），but the contact angle of the sample annealed in Argon gas decreased obviously lag behind.Deposing these samples in dark for 100 days，the contact angles of them all increased，and the biggest change was still from the sample annealed in Argon gas（contact angle greater than 90°）.After 3 h under illumination with the simulated sunlight，they all returned to the super hydrophilic.After repeated experiments it was found that the wettability switched was reversible.Further characterization analysis revealed that the morphologies of the samples were not much different after annealing treatment under various atmosphere，but their crystallinity and the oxygen vacancy concentration were obviously different.Therefore，the contact angle of the sample annealed under different atmosphere was both depended on its concentration of oxygen vacancy and its crystalline.Especially the surface wettability of samples related to oxygen vacancy should be paid more attention on this research field.