Preparation And Superhydrophilicity Of Thin Nanostructured TiO₂ Films Doped By Metal Ions

TiO₂ film has excellent photocatalytic and photoinduction superhydrophilic characteristics.It has broad application prospects in fields of catalytic degradation of organic matter in the light,desensitized solar cells,antifogging and self-cleaning.It was important to raise the utilization rate of visible light and to maintain hydrophilic stability of TiO₂ film.In the application of TiO₂,spectral response of TiO₂ doped by Rh,V,Ni,Cd,Cu, Fe or metal oxides will be generally widen in the 400 nm～600nm.A suitable metal or its oxide can increase hydrophilicity of TiO₂ film and reduce wavelength.In this article,TiO₂ films were doped by alkaline earth metal strontium,rare earth metal lanthanum and transition metal nickel,iron.The dependence of TiO₂ films doped by metal ions on the hydrophilicity was characterizaed and analysed.Research for three parts:First,SrO-TiO₂,La₂O₃-TiO₂ and NiO-TiO₂ collo sol were prepared using butyl titanate as premedicant by sol-gel method.Second, SrO-TiO₂,La₂O₃-TiO₂ and NiO-TiO₂ films were prepared on common glass substrates with dip-coating technique.Finally,these films were characterized by X-ray diffraction(XRD),infrared spectroscopy(IR)and visible absorption spectra.The hydrophilicity of these films was determined by measuring the water contact angles of these flims.The effects of the metal doped quantities,the intensity and the time of UV illumination on hydrophilicity of the films were studied.Experiment results show that:(1)XRD results showed that SrO-TiO₂ powder is smaller size than TiO₂ due to alkaline earth metals strontium doped.The film containing 1.0%Sr²⁺has the best hydrophilicity.The photoinduction superhydrophilic state of SrO-TiO₂ film can maintain a week in the dark.After UV illumination 60 min,the water contact angle rapidly decreased,close to 0°,full rollout on the film surface.It showed superhydrophilicity.(2)Titanium dioxide powder doped by La³⁺is the smaller than TiO₂.La₂O₃-TiO₂ film has better photoinduction superhydrophilicity than pure titanium dioxide film. The films containing 0.5%La³⁺had superhydrophilicity in the dark after 72 h. La₂O₃-TiO₂ film shifted the absorption spectra.It can absorb the visible light,and the transmission rate of the film was about 70%.(3)The water contact angle of NiO-TiO₂ film increased gradually as increasing amount of layers.By two-coating,the water contact angle of NiO-TiO₂ film increased 20°.By three-coating,the water contact angle hardly changed.After UV illumination, the weter contact angles were significantly decreased,all films showed hydrophilicity. As a comparative experiment,the film containing 1.5%Fe³⁺had superhydrophilicity after UV illumination.(4)The photocatalytic activitie of SrO-TiO₂ film or La₂O₃-TiO₂ film was superior to that of pure TiO₂ film.After UV illumination 60 min,the films contained 1.5%Sr²⁺or 1.0%La³⁺had the best photocatalytic activity.To sum up,Titanium dioxide powder doped by Sr²⁺or La³⁺has smaller size than pure TiO₂ powder.After UV illumination,the water contact angle rapidly decreased, showed superhydrophilicity.La₂O₃-TiO₂ film can absorb the visible light.The film containing 1.5%Sr²⁺or 1.0%La³⁺had the best photocatalytic activity.