[en] We studied the effects of thermal annealing of ZnO ceramics by X-ray photoelectron spectroscopy, photoluminescence and X-ray scattering methods. The ZnO ceramics fabricated from the high purity ZnO powder (99.999 %) were annealed at 950 .deg. C in air and in N₂ atmosphere. The ZnO ceramics annealed in N₂ atmosphere have O-rich condition. The concentration of antisite oxide(O_zn) increases when ZnO ceramics have the O-rich condition or N-compensation. As the concentration of antisite oxide(O_zn) increases, the photoluminescence intensity of the green band emission increases

[en] The synthesis of narrowly dispersed nanocrystalline TiO₂ was investigated with a surfactant aided solvothermal synthetic method in toluene solutions. When a sufficient amount of titanium isopropoxide, Ti[OCH(CH₃)₂]₄ (TIP), was added to the solution, the shapes of TiO₂ nanoparticles changed from spheres to rods. The aggregated microstructures of the nano-sized TiO₂ in systems of spheres, rods, and mixtures of spheres and rods was studied using TEM. The morphological shape of the aggregation was described in terms of the fractal dimensions. We used a box-counting method to get the fractal dimension of these systems. The fitted fractal dimensions for spheres, sphere/rod mixtures, and rods are D = 1.54, D = 1.81, and D = 1.89, respectively. The fractal dimension changed from 1.54 to 1.9 with the TIP/toluene ratio, indicating that the growth mechanism for aggregations showed different behaviors.

[en] Optical, structural and photocatalytic properties of TiO₂ thin films obliquely deposited on quartz glass substrate using an electron-beam evaporation method were investigated. The photocatalytic activity of the films was evaluated by photodecomposition of methylene blue. An increase in incident deposition angle increased the porosity and surface roughness of the TiO₂ films. As a result, the photocatalytic activity was enhanced with incident deposition angle up to 60 deg. However, a further increase in incident deposition angle to 75 deg. reduced the photocatalytic activity due to a lack of the crystalline phase.

[en] Morphological, structural and photocatalytic properties of graphene oxide (GO)/TiO₂ thin-film deposited on quartz substrate were investigated. The TiO₂ film was prepared by electron-beam evaporation and the GO film by spin coating method. The photocatalytic activities of the GO/TiO₂ film were evaluated by photodecomposition of methylene blue. There was synergistic effect between TiO₂ and GO which causes a rapid photo-induced charge separation and the reduction of the recombination of electron–hole pairs under the UV–visible light irradiation. GO on TiO₂ film also promotes the properties of adsorption of the dye, photon scattering probability, and interacting surface area. As a result, it leads to the enhancement of the efficiency of the photodegradation in GO/TiO₂ film. - Highlights: ► Graphene oxide (GO)/TiO₂ film exhibited improved charge separation and transport. ► GO/TiO₂ had higher photon scattering on surface and better adsorption than the TiO₂. ► Recombination of electron–hole pairs reduced under the UV–visible irradiation. ► Hydroxyl and epoxide groups in GO reduced during the photocatalytic process. ► TiO₂ achieved anatase phase by electron-evaporation method.

[en] Nanocrystalline TiO₂ powders were obtained by the solvothermal route from the Ti(OR)₄ precursor precipitated in toluene under different concentrations. The prepared titania is in the form of nanocrystalline anatase with different sizes dependent on the precursor concentrations. Average particle size is about 10 nm and 20 nm for contents of precursor below 10 mol% and above 50 mol%, respectively. TiO₂ nanoparticles tend to agglomerate to form sphere balls from the solutions of above 20 mol% concentration. Dependence of particle size on the anatase-rutile phase transformation was investigated by XRD study. Morphology of titania particles depending on annealing temperature was also investigated using scanning electron microscopy