TiO2 thin films with different surface structures are prepared from alkoxide solutions containing polyethylene glycol PEG.via the sol-gel method. The effects of PEG addition to the precursor solution on the surface structures and photocatalytic activity of the resultant thin films are studied. The larger the amount of PEG added to the precursor solution, the larger the size and number of pores produced in the resultant films when PEG added to the gel films decomposed completely during heat-treatment. The adsorbed hydroxyl content of such porous thin films is found to increase with increasing amount of PEG. However, the transmittance of the films decreases due to the scattering of light by pores of larger size and bigger number in the films. Photocatalytic degradation experiments show that methyl orange is efficiently decolorized in the presence of the TiO2 thin films by exposing its aqueous solution to ultraviolet light and the suitable surface structures remarkably enhance the photocatalytic activity of TiO2 films.

Highly photoactive bi-phase nanocrystalline TiO2 photocatalyst was prepared by a solvent evaporation-induced crystallization (SEIC) method, and calcined at different temperatures. The obtained TiO2 photocatalyst was characterized with X-ray diffraction (XRD), transmission elec-tron microscopy (TEM) and BET surface areas. The photocatalytic activity was evaluated by the photocatalytic oxidation of acetone in air. The results show that solvent evaporation can promote the crystallization and phase transformation of rio2 at 100℃. When calcination temperatures are below 600℃, the prepared TiO2 powders show bimodal pore size distributions in the mesoporous region. At 700℃, the pore size distributions exhibit monomodal distribution of the inter-aggregated pores due to the collapse of the intra-aggregated pores. At 100℃, the obtained TiO2 photocatalyst by this method shows good photocatalytic activity, and at 400℃, its photocatalytic activity exceeds that of Degussa P25. This may be attributed to the fact that the prepared TiO2 photocatalyst has higher specific surface areas, smaller crystallite size and bimodal pore size distribution.

red on a soda-lime glass substrate by sol-gel dip-coating technique using TiO2 sols containing lead(II) nitrate. The thin films were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), UV-VIS spectroscopy and X-ray diffraction (XRD). A shift of the UV-VIS absorption towards longer wavelengths was observed, which indicated a decrease in the band-gap of TiO2 upon Pb doping. XRD results showed both pure and Pb-doped TiO2 thin films were polycrystalline, anatase type, and oriented predominantly to the (101) plane. A slight shift in the d-spacing for the Pb-doped film indicated the incorporation of Pb into the TiO2 lattice to form Pbx Ti1−xO2 solid solution. AFM results showed Pb-doped TiO2 thin films were composed of larger TiO2 particles and had rougher surface, compared with un-doped TiO2 thin films. XPS results showed that except for the enrichment of Pb near the surface, Pb exists in the forms of Pbx Ti1−xO2 and PbO. Dimethyl-2,2-dichlorovinyl phosphate (DDVP) was efficiently degraded in the presence of the Pb-doped TiO2 thin films by exposing the insecticide solution to sunlight. The mechanism of photocatalytic activity enhancement of the Pb-doped TiO2 thin films was discussed.

Mesoporous TiO2 nanometer thin films were prepared on fused quartz by the dip-coating sol-gel method from a system containing a triblock copolymer as a template (or pore-forming agent), and then calcined at different temperatures. These films were characterized by X-ray diffraction, atomic force microscopy, X-ray photoelectron spectroscopy, BET surface area and UV-visible spectrophotometry. The photocatalytic activity and photo-induced super-hydrophilicity of the films were evaluated by the photocatalytic degradation of acetone and water contact angle measurement in air, respectively. It was found that the thin films calcined at 700℃ not only show the highest photocatalytic activity, but also possess the greatest light-induced hydrophilicity and the slowest conversion rate from the hydrophilic to a hydrophobic state. The former is attributed to the fact that the films calcined at 700℃ are composed of anatase and rutile, whichis beneficial in enhancing the transfer of photo-generated electrons from the anatase to the rutile phase, reducing the electron-hole combination rate in anatase and enhancing its activity. The high light-induced hydrophilicity and slow hydrophilic to hydrophobic conversion rate are due to the synergetic effect of good photocatalytic activity, sufficient surface hydroxyl content and a degree of surface roughness. Because of their high specific surface areas and mesoporous structures, the photocatalytic activity of mesoporous TiO2 thin films is higher than that of conventional TiO2 thin films.

Transparent anatase TiO2 nanometer thin films with photocatalytic activity were prepared via the sol-gel method on soda-lime glass, fused quartz, and soda-lime glass precoated with a SiO2 layer. The resulting thin films were characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The photocatalytic activity of the various TiO2 films was evaluated by the photocatalytic decolorization of aqueous methyl orange. The diffusion of sodium and calcium ions from the soda-lime glass into the nascent TiO2 films was found to be detrimental to the photocatalytic activity of the resulting TiO2 films. Sodium and calcium diffusion into nascent TiO2 films was effectively retarded by a 0.3mm SiO2 interfacial layer formed on the soda-lime glass.