The Studies On Preparation And Photocatalytic Activity Of Nanosized Composite TiO₂Hydrosol And Thin Film

In recent years, a novel nano-TiO₂photocatalytic degradation technology attracts greatattention due to its low cost, environment friendly and high photocatalytic degradationefficiency. However, the band gap of pure TiO₂is wide, so it can only use the ultraviolet rayswith wavelength of less than400nm. At the same time, the recombination of electrons andhole and the low utilization ration of sunshine lead to the decrease of efficiency. Based on thelatest research about the thin film materials and doping technology, we try to prepare a kind ofnovel nano-TiO₂composite thin film. This research mainly focuses on the optimization ofnormal temperature complexation, controllable hydrolyzation and doping ratio. Thephotocatalytic degradation performance is tested by the photocatalytic experiments. Thisdissertation is divided into two parts:1. The studies on preparation and photocatalytic activity of nanosized composite TiO₂hydrosol: Sr²⁺-doped nano TiO₂colorless and transparent hydrosol with an average particlesize of6nm was synthesized by a novel complexation-controlled hydrolysis method at roomtemperature by using TiCl₄, organic carboxylic acid, stabilizer, surfactant, NH₃·H₂O,Sr（OH）₂·8H₂O, and D-sorbitol etc as raw materials. Nanometer laser particle size analysisshows that the average particle size of sample is about6nm. XRD analysis shows that thesample is sharp titanium mineral crystal along with the extension of the backflow time. TheUV-Vis analysis found that the scope of the spectral response of the sample is broadened, andthe utilization rate of the sun is improved by doping Sr²⁺into TiO₂lattice. The maximumabsorption edge curve of the sample was extended from375nm （UV region） to425nm（visible region）, and the forbidden band width reduced from3.2eV to2.85eV. TheSr²⁺-doped nano TiO₂hydrosol exhibits optimal photocatalytic performance when the dopingcontent of Sr²⁺and refluxing time are1.8%and60min, respectively. The degradationefficiency of acid red3R dye solution with concentration50mg/L has reached96%afterexposed to sunlight for60min.2. The studies on preparation and photocatalytic activity of nanosized composite TiO₂thin film: Connect spray gun （0.5mm caliber） with air compressor, open the valve of aircompressor, and atmosphere get into cylinder through the filter. When the atmosphere reachesthe threshold, the air valve would close automatically. Then the Sr²⁺-doped nanoscaled TiO₂colorless and transparent hydrosol was poured into the high pressure spray gun and spayed atthe surface of glass or the inwall of beaker at the speed of30cm/s. Finally, the uniformtransparent nanoscaled TiO₂film was obtained. AFM analysis shows that the sample isspherical, uniform, and non-aggregated with particle size of about6nm. Optical contact angletest shows that the average contact angle of thin-film samples is about0.91°, which showsgood super-hydrophilicity. It can also be found that the degradation efficiency of acid red3Rdye solution with concentration50mg/L has reached80%after exposed to sunlight for60min when the pH value of solution between3and4. FT-IR analysis demonstrates that theas-obtained TiO₂film can make the-N=N-,-SO₃Na, and C-H of benzene groups oxidated andfractured, resulting in the degradation of acid red3R.