A. S. Shaporev

UV-shielding property, photocatalytic activity and photocytotoxicity of ceria colloid solutions.

UV-shielding property, photocatalytic activity and cytotoxicity (including photocytotoxicity) of citrate-stabilized ceria colloid solutions were studied. It was established that UV-shielding property (namely, the sun protection factor, the critical absorption wavelength and the UVA/UVB-ratio) of ceria nanoparticles are as good as those of titanium dioxide and zinc oxide nanoparticles. It was further demonstrated that ceria nanoparticles possesses substantially lower photocatalytic activity, which additionally decreases upon decrease in ceria particle size. It was found that colloid ceria solutions are non-toxic to mouse fibroblasts (L929) and fibroblast-like cells of African Green monkey (VERO). Moreover, ceria nanoparticles are capable to protect these cells from UV-irradiation-induced damage. It was proposed that nanocrystalline ceria could be used not only as UV-blocking material, but also as prophylactic and even therapeutic compound for sunburns treatment.

ZnO formation under hydrothermal conditions from zinc hydroxide compounds with various chemical histories

The sequence of phase transformations of zinc hydroxide compounds with various chemical histories during hydrothermal (HT) treatment is studied by X-ray powder diffraction and thermal analysis (TG/DTA). ɛ-Zn(OH)2 (wulfingite) is the major intermediate in ZnO production by the HT process. The micromorphology and photocatalytic activity of ZnO powders are studied.

Microwave-Assisted Hydrothermal Synthesis and Photocatalytic Activity of ZnO

The effect of synthesis temperature on the morphology of fine zinc oxide powders prepared by microwave-assisted hydrothermal processing of Zn(OH)2 suspensions has been studied using x-ray diffraction and low-temperature nitrogen BET measurements. The photocatalytic activity of the powders for Methyl Orange photodegradation has been assessed as a function of synthesis temperature. The results indicate that the specific surface of ZnO powders plays a key role in determining their photocatalytic activity.

Synthesis and thermal stability of nanocrystalline ceria sols stabilized by citric and polyacrylic acids

New methods are proposed for preparing aqueous sols of nanocrystalline ceria stabilized by citric or polyacrylic acid. Transmission electron microscopy and UV-Vis spectroscopy were used to study the stability of sols in hydrothermal treatment at temperatures in the range of 120–210°C.

Hydrothermal synthesis of efficient TiO2-based photocatalysts

We carried out a thorough study of the micromorphology, physicochemical properties, and photocatalytic activity of nanocrystalline anatase powders formed during the hydrothermal treatment of titanyl sulfate solutions of various compositions. A new procedure is proposed for the hydrothermal synthesis of nanocrystalline anatase having specific surface areas of ∼50 m2/g and photocatalytic activities exceeding the activity of the commercially available Degussa P25 formulation.

Hydrothermal synthesis and catalytic properties of superacid sulfated titania

The micromorphology and catalytic properties of nanocrystalline TiO2/SO42− superacid systems prepared by a conventional sol-gel process, as well as hydrothermal (HT) and microwave-hydrothermal (MW-HT) processes, were analyzed. The samples prepared by the HT process have no developed surfaces and, as a consequence, have no high reactivity in isobutylene oligomerization. The TiO2/SO42− samples prepared by single-step MW-HT synthesis in their morphologic, acid, and catalytic properties are competitive with the systems prepared by the conventional multistage sol-gel process.

Hydrothermal synthesis and photocatalytic activity of highly dispersed ZnO powders

The micromorphology of highly dispersed ZnO powders formed from Zn(OH)2 gels under hydrothermal conditions is studied by powder X-ray diffraction, X-ray diffraction analysis, and low-temperature nitrogen adsorption. The parameters of hydrothermal synthesis (heating rate, treatment duration, and temperature) are found to effect the microstructural characteristics of the products. The photocatalytic activity of the synthesized zinc oxide samples in the model reaction of Methyl Orange photodegradation is studied. The synthesis parameters for preparing ZnO powders with high photocatalytic activity are determined.