Preliminary investigation of solution diffusive behavior on V-doped TiO2 nanotubes array by electrochemical impedance spectroscopy.

V-doped TiO2 nanotubes array was successfully fabricated on a Ti-V alloy via an electrochemical anodization process. The crystal phase and surface morphology of the nanostructured film were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The solution diffusive behavior on TiO2 nanotubes was investigated by electrochemical impedance spectroscopy (EIS) analysis in an aqueous electrolyte containing 0.05 M Na2SO3. A schematic diagram of the interface solution induced into nanotube by photocatalysis on V-doped TiO2 under visible light irradiation was proposed in the study. Considerable photogenerated holes migrate to the interface of TiO2/electrolyte and react with OH-, forming hydroxyl radicals, which induce the electrolyte into the nanotube and improve the hydrophilicity. It was found that the photoelectrocatalytic reaction of TiO2 nanotubes determined the diffusion behavior of the solution; faster diffusion was observed on the V-doped TiO2 nanotubes array under visible light irradiation. The results also demonstrated that EIS is a powerful tool for characterizing the complicate diffusion behavior within the porous nanostructures.

A novel NO2 sensor based on TiO2 nanotubes array with in-situ Au decoration.

Au decorated TiO2 nanotubes array was successfully fabricated on a Ti-Au alloy via an electrochemical anodization process. The crystal phase and microstructure of the TiO2 nanotubes array were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM), respectively. Au particles were well distributed among TiO2 nanotubes and acted as the catalyst. It was found that the sensor based on Ti-Au alloy anodization can be a promising sensor which was highly sensitive to low concentrations of nitrogen dioxide (NO2), and response at room temperature. The sensitivity of Au-decorated TiO2 nanotubes sensor was 36.11 to 8 ppm NO2 at room temperature. Meanwhile, the resistance signal of Au-decorated TiO2 sensor changes quickly within 80 s upon exposure to 8 ppm NO2 at 35 degrees C, the undecorated TiO2 however takes much more time (>110 s) to respond and the resistance signal remains unstable.