Materials Science Forum Vols. 620-622

Abstract: F-doped TiO2 has exhibited superior photocatalytic activity. However, its electronic structures and photocatalysis mechanism are still unclear. In the present work, the structural optimization and electronic structure of F-doped anatase TiO2 have been investigated by means of the first-principles pseudopotential total energy method. It has been demonstrated that F doping would modify the valence band at the lower energy direction in the F-doped TiO2. Calculation results confirm that doping of fluorine would not shift the absorption edge into the visible light region. Instead, we attributed its photocatalytic activity to the enhancement of the oxidative power of F-doped TiO2.

Abstract: Indium-alkali microfibers doped ceramic were prepared by the sol-gel process. The gels preparation samples, were heat treated at 700°C for different length of time. The products were characterized by means of XRD, SEM-EDS and UV–Vis-DRS. The XRD showed the formation of the Na2Ti6O13 phase whose crystallinity depends on the annealing time. The band gap calculated from the UV–Vis Kubelka-Munk function shows very similar values (3.53-3.55 eV). The SEM images of the indium-alkali titanates show microfiber clumps morphologies of about 5 µm, and the EDS spectra show that In2O3 is on the Na2Ti6O13 surface. The results of the evaluation of the In-Na2Ti6O13 semiconductors in the 2, 4-dichlorophenoxyacetic acid (2, 4-D) photodecomposition under UV light irradiation, show that the photoactivity depends on the time of heat treatment of the samples.

Abstract: Monoclinic crystal bismuth vanadate (BiVO4) was synthesized by the high temperature solid state reaction after ball milling the materials of Bi2O3 and V2O5. The influences of sintering times on the crystal phases and structures of BiVO4 powders were studied through the XRD、FTIR characterization. Fe-doped BiVO4 was prepared by doping ferric chloride to pure monoclinic crystal BiVO4 to improve the photo absorbance performance of BiVO4 and to promote the isolation of photo-induced carriers. Visible light activity of BiVO4 and Fe-doping BiVO4 were characterized using the UV-diffuse reflectance spectroscopy. The electrochemical behaviors of BiVO4 and Fe-doping BiVO4 were investigated under the condition of avoiding light or under light.

Abstract: The influence of the titania photocatalyst nano-particles to the skin is to be doubted. We studied the influence of different titania photocatalyst nanoparticles shape to the artificial skin like the human body under the UV light irradiation conditions. The decomposition degree of the artificial skin was evaluated from the monitoring of the amount of carbon dioxide generated from them by the titania photocatalyst nanoparticle activity. When spreading their titania nanoparticles on the skin sample, the carbon dioxide generated from the skin was not detected in the apatite coating titania nano-particle sample through was detected the sample coating no apatite. The result was considered not to have existed the influence on the skin samples because the titania nano-particle was not to touch the skin sample directly.

Abstract: Fluidized Bed Chemical Vapor Deposition (FB-CVD) method offers advantages over conventional Chemical Vapor Deposition method in coating three dimensional objects. In addition, catalysts prepared by FB-CVD method often show improved physicochemical properties. Thus, FB-CVD seems a useful method for coating TiO2 onto small beads, in view of their photocatalytic application in aqueous environment, for example. In this work, we produced TiO2 coated beads (1~2mm in diameter) of alumina, silica-gel, and glass in ~35nm thickness using FB-CVD method, and examined photocatalytic performance of TiO2 coated beads in the photocatalytic decomposition reaction of methylene blue solution. Based on the combined results of the decomposition reaction kinetics of methylene blue and FE-SEM images of the surface morphology of TiO2 coated beads, we were able to account for the photocatalytic performance with respect to characteristic features detected in the surface morphology.

Abstract: Nitrogen doped titania was coupled with the commercial titania nanoparticles by mechanical milling in liquid medium. When small amount of nitrogen doped titania was added into the commercial titania, higher intensity and longer lifetime of 1O2 was observed, and the photocatalytic activity was efficiently improved. The TiO2-xNy acts as the acceptor of photoinduced holes. The recombination of the electron-hole was effectively depressed by the heterogeneous electron transfer. This could be an effective way to obtain high active photocatalyst.

Abstract: This paper aims at the investigation of photocatalytic properties of titanium dioxide coatings covering on the surfaces of long blue-emitting afterglow CaAl2O4:Eu2+, Nd3+ elaborated by a sol-gel method. Morphologies and microstructures of the coatings were observed mainly by transmission electron microscopy (TEM) and analyzed by X-ray diffraction (XRD). The photocatalytic behavior of the TiO2-base surfaces was evaluated by the degradation of methyl orange (MO) solution. It suggested that a layer of TiO2 film mounted on the phosphor particles successfully. Also, the TiO2 coatings had remained its photocatalytic role on the as-prepared sample even after the light source was removed. The inner long blue-emitting afterglow had released blue afterglow after removing light source and allowed for reactive TiO2 surfaces to be held for the removal of methyl orange.

Abstract: Two types of titanium dioxide sol solutions were prepared using titanium tetra-isopropoxide, urea, 2-methoxyethanol and water. The prepared sol solutions were dip-coated onto fused silica plates. These as-prepared films were dried at 100 °C and then annealed at 650 °C. The annealed films were anatase type titanium dioxides. Visible light absorption by the films was observed in wavelengths longer than 400 nm. Also, photodegradation of methylene blue by visible light irradiation was accelerated in the presence of the films prepared by these methods.

Abstract: Thin films of various composition in the system of TiO2•SiO2 have been fabricated by the sol-gel process using Si(OC2H5) and Ti(OC3H7i)4 as precursors. TiO2•SiO2 films were formed on the glass substrate by spin-coating technique and heated at 500°C for 1 h. The relationship between hydrophilicity, photocatalytic properties and self-cleaning property with SiO2 addition and UV light irradiation were investigated. Photocatalytic activity of TiO2•SiO2 films showed decomposition of ~97% of acetaldehyde in 2 h and a water contact angle of ~10°. TiO2•SiO2 films can have more hydrophilic activity and less photocatalytic activity by increasing of SiO2 addition. XPS measurements revealed that the amount of organic compounds adsorbed on the films decreased with the UV light irradiation and SiO2 addition, because of the increased of both OH group contents in films and decomposed organic contaminants of the films surface.

Abstract: Visible-light responsible Mn-N-codoped TiO2 nanocrystal photocatalysts were synthesized for the first time by a simple hydrothermal synthesis method. X-ray powder diffraction (XRD) measurement indicated that all of the photocatalysts have an anatase crystallite structure and the increase of the doping concentration had less effect on the structure and particle size. Comparing to N-doped TiO2, a shift of the absorption edge of Mn-N-codoped TiO2 to a lower energy and a stronger absorption in the visible light region were observed. The Mn-N-codoped TiO2 showed a higher photocatalytic reactivity than undoped TiO2 and N-doped TiO2 for the photodegradation of rhodamine B (RhB) under visible light irradiation. The doping concentration had an optimal value, according to the highest photocatalytic activity. This suggested that Mn and N codoping has important effects on the improvement of visible-light responsible photocatalytic activity.