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.

f F, N, and Si elements. The F and N came from the precursor solution, and the amount of F decreased with increasing calcination temperature. Two sources of Si were identified. One was from the SiF6 2-ions, which were formed by a reaction between the treatment solution and quartz substrate. The other was attributed to the diffusion of Si from the surface of quartz substrate into TiO2 thin film at 700℃ or higher calcination temperatures. With increasing calcination temperature, the photocatalytic activity of the TiO2 thin films gradually increased due to the improvement of crystallization of the anatase TiO2 thin films. At 700℃, the TiO2 thin film showed the highest photocatalytic activity due to the increasing amount of SiO2 as an adsorbent center and better crystallization of TiO2 in the composite thin film. Moreover, the SiO2/TiO2 composite thin film showed the lowest PL intensity due to a decrease in the recombination rate of photogenerated electrons and holes under UV light irradiation, which further confirms the film with the highest photocatalytic activity at 700℃. When the calcination temperature is higher than 700℃, the decrease in photocatalytic activity is due to the formation of rutile and the sintering and growth of TiO2 crystallites resulting in the decrease of surface area.

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.

A novel and simple method for preparing highly photoactive nanocrystalline F-doped TiO2 photocatalyst with anatase and brookite phase was developed by hydrolysis of titanium tetraisopropoxide in a mixed NH4F-H2O solution. The prepared F-doped TiO2 powders were characterized by differential thermal analysis-thermogravimetry (DTA-TG), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis absorption spectroscopy, photoluminescence spectra (PL), transmission electron microscopy (TEM), and BET surface areas. The photocatalytic activity was evaluated by the photocatalytic oxidation of acetone in air. The results showed that the crystallinity of anatase was improved upon F-doping. Moreover, fluoride ions not only suppressed the formation of brookite phase but also prevented phase transition of anatase to rutile. The F--doped TiO2 samples exhibited stronger absorption in the UV-visible range with a red shift in the band gap transition. The photocatalytic activity of F-doped TiO2 powders prepared by this method exceeded that of Degussa P25 when the molar ratio of NH4F to H2O was kept in the range of 0.5-3.

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.

Sulfur-doped titanium dioxide exhibits a strong visiblelight-induced antibacterial effect. The new photocatalyst can effectively kill Micrococcus lylae, a common Grampositive bacterium. The relationship between sulfur concentration and the bactericidal activity of S-doped TiO2 was investigated. Results from DMPO spin-trapping electron spin resonance measurements confirm the formation of hydroxyl radicals, which is the origin of the considerable bactericidal activity under visible light irradiation.

Transparent TiO2 nanometer thin films with high photocatalytic activity were prepared on soda-lime glass substrates via the sol-gel method using the TiO2 sol solution. The valency state of Ti element and the chemical compositions in TiO2 thin films were analyzed with X-ray photoelectron spectroscopy (XPS). Experimental results showed that besides Ti, O and C elements there is a small amount of Na and Ca elements diffused from the glass substrates and besides Ti(IV) there is a certain amount of Ti(III) and Ti(II) in TiO2 thin film. Heating temperature of 500 C may be adopted to convert TiO2 gel films into TiO2 (anatase) crystalline films and also the TiO2 (anatase) crystalline films show the highest photocatalytic activity. It was also found that the heat treatment for a suitable time at 500 C improves remarkably the photocatalytic activity of the TiO2 thin film, although for too long a time, rather deteriorates it. These results are explained on the basis of the changes in the surface structure and Ti3C concentration with the heat treatment time.

Bimodal mesoporous titania powders with high photocatalytic activity were prepared by hydrolysis of titanium tetraisopropoxide in the presence of HNO3 or NH4OH under ultrasonic irradiation. The powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), BET surface areas, and X-ray photoelectron spectroscopy (XPS). Photocatalytic activity was evaluated by the photocatalytic oxidation of acetone in air. The effects of catalysts added during hydrolysis on the microstructure and photocatalytic activity of the TiO2 powders were investigated. The results showed that HNO3 enhanced the growth of brookite, while NH4OH not only retarded phase transformation of the TiO2 powders from amorphous to anatase and anatase to rutile but also suppressed the growth of brookite. All TiO2 powders calcined from 400 to 600℃ showed bimodal pore-size distributions in the mesoporous region: one was intraaggregated pores with maximum pore diameters of ca. 4-9nm and the other interaggregated ones with maximum pore diameters of ca. 3550nm. At 700℃, the pore-size distributions of all samples exhibited monomodal distribution of the interaggregated pores due to the collapse of the intraaggregated pores. The photocatalytic activity of the TiO2 powders prepared by this method and calcined at 400℃ exceeded that of Degussa P-25 when the molar ratio of HNO3 or NH4OH to H2O was less than 0.05.

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.

Transparent anatase mesoporous TiO2 (MTiO2) and TiO2 nanometer thin films were prepared on soda-lime glass and fused quartz via the reverse micellar method and sol-gel method, respectively. The as-prepared MTiO2 and TiO2 films were then treated by dipping them in aH2SO4 solution. TheMTiO2 and TiO2 films before and after surface acid treatment were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray diffraction (XRD), BET surface area and UV-VIS spectrophotometry. The photocatalytic activity of the samples was evaluated by photocatalytic oxidation of acetone in air. Itwas found thatMTiO2 thin films showed higher photocatalytic activity than that of the TiO2 thin films. This was attributed to the fact that MTiO2 thin films were composed of smaller monodisperse spherical particles about 15nm and had higher specific surface areas. Furthermore, the monodispersity of TiO2 particles was beneficial to transfer and separation of photo-generated electrons and holes in the inner of and on the surface of TiO2 particle and reduced the recombination of photo-generated electrons and holes. The films deposited on quartz showed the highest photocatalytic activity because films deposited on quartz exhibited a better crystallization and had no sodium contaminant. The photocatalytic activity ofMTiO2 andTiO2 thin films deposited on different substrates after treated withH2SO4 solutionwas significantly enhanced. Acid treatmentwas particularly effective forMTiO2/glass andTiO2/glass, which showed activity enhancement of four and over two times, respectively. This increase in activity has been correlated with the reduction of sodium ions and the increase in the adsorbed hydroxyl content on the surface of TiO2 films.