D. V. Sviridov

Photocatalytically-active and photocontrollable coatings based on titania-loaded hybrid sol-gel films

The photocatalytically-active coatings were obtained by immobilizing titania nanoparticles into a sol–gel-derived SiOx:ZrOx matrix. The resultant hybrid films show high photocatalytic, photobiocide and excellent corrosion protection properties which exhibit no degradation during the course of long-term irradiation with UV light. The possibility of a UV-induced opening of titania-based polyelectrolyte containers embedded into SiOx:ZrOx film is also demonstrated that opens fresh opportunities in developing photocontrollable coatings capable to release encapsulated chemical agents under illumination.

Nanoengineered Metal Surface Capsules: Construction of a Metal‐Protection System

The novel encapsulation system based on a sonochemically formed porous metal layer, which is continuous with the bulk metal is presented. The high surface area of this layer allows the upload of active components (corrosion inhibitors, antiseptics, antibiotics, DNA fragments, etc.). We propose two types of encapsulation systems. According to the Type I system, the spontaneous release of loaded components from the surface capsules can be prevented through chemisorption of the component to the porous metal capsules due to presence of –OH groups. In the Type II encapsulation system, complex formation between an active component and polyelectrolyte can be used. Both encapsulation systems suggested here could solve crucial problems in surface engineering and surface protection: adhesion of a protective system to the surface and release of an active compound on demand.

Photocatalytic microreactors based on TiO2-modified polyelectrolyte multilayer capsules

Spatially confined photocatalytic microreactors for microheterogeneous photoreduction of metal ions from aqueous solutions have been developed. The microreactors consist of hollow micron-sized polyelectrolyte capsules with photoactive TiO2 nanoparticles incorporated in the walls. Additional improvements in metal photoreduction efficiency were achieved by filling the microcapsule cavity with a more effective electron donor.

Magnetic photocatalysts of the core-shell type

Two magnetic core-shell type photocatalytic systems are presented: first, Zn0.35Ni0.65Fe2,O4-SiO2-TiO2, showed high activity in the photooxidation of oxalate, and the other, Fe3O4-Fe2O3-polyaniline: P2W18O62(6-), was tested in the reaction of SO2 photooxidation.

Effect of silver deposits on the photocatalytic activity of titanium dioxide for the removal of 2-chlorophenol in water

The effect of Ag photodeposition on the rate of photocatalytic degradation of 2-chlorophenol (2-CP) in aqueous suspensions of Degussa P 25 titanium dioxide has been studied using HPLC. For Ag contents between 5 x 10(-6) and 1.6 x 10(-4) wt%, the rate was slowest int he absence of Ag and increased with increasing Ag content. For a Ag content of 6 x 10(-4) wt%, the degradation rate was about 50% faster than with bare TiO2, and decreased for a Ag content of 7.2 x 10(-4) wt% and beyond, eventually becoming slower than unmodified TiO2. Bare TiO2 has been compared with the 6 x 10(-4) wt% Ag-TiO2 sample in terms of the variation of chlorohydroquinone (CHQ) and chloro-1,4-benzoquinone (CBQ) concentrations during 2-CP degradation, and also for the degradation of CHQ and CBQ separately. On the basis of these experiments, it is tentatively suggested that the net effect of Ag on 2-CP removal results from opposite influences, viz. the Ag+ cation-induced oxidation of CHQ to CBQ and the Ag0 particle-induced recombination of photoproduced charges, both influences being assumed to depend on the Ag particle size, itself related to the Ag content.

Titanium and Iron Oxide-Based Magnetic Photocatalysts for Oxidation of Organic Compounds and Sulfur Dioxide

New approaches to designing magnetic photocatalysts on the basis of microheterogeneous structures built according to the scheme “magnetic core–photocatalytic shell” were proposed. A procedure for preparing the Zn0.35Ni0.65Fe2O4/SiO2/TiO2 catalyst designed for the destructive oxidation of organic compounds, as well as the Fe3O4/Fe2O3/Fe4[Fe(CN)6]3: KCo[Co(CN)6] and Fe3O4/Fe2O3/polyaniline catalysts designed for the photo-oxidation of SO2, was considered. It was shown that the reduction of molecular oxygen proceeded primarily to H2O2, as a result of doping the polyaniline shell with 18-tungstophosphoric acid, and the quantum yield of the SO2 photo-oxidation reaction was doubled by coupling heterogeneous photocatalysis with homogeneous catalysis (involving the hydrogen peroxide formed).

Highly efficient generation of H2O2 at composite polyaniline/heteropolyanion electrodes: effect of heteropolyanion structure on H2O2 yield

A new highly efficient electrochemical H2O2 generating system based on polyaniline film doped with heteropolytungstate anions was developed. The oxygen reduction characteristics of polyaniline–heteropolytungstate composites were investigated using the rotating disk–ring electrode technique. Polyaniline electrode with immobilized heteropolytungstate anions of the Dawson structure (P2W18O626−) exhibits a 75% efficiency of H2O2 generation in the acid medium while polyaniline doped with heteropolytungstate anions of the Keggin structure (PW12O403−) reduces O2 predominantly by four electrons. It was established that the chemosorption of H2O2 during the reduction of O2 governs the efficiency of hydrogen peroxide generation.

Switching the Stiffness of Polyelectrolyte Assembly by Light to Control Behavior of Supported Cells

Polyelectrolyte block copolymer micelles assembled thin film is switched in response to local photocatalytic reactions on titanium dioxide, resulting in a layer of variable height, stiffness in response to visible light irradiation. Preosteoblasts migrate toward stiffer side of the substrates.

Transformations of mixed molybdenum-vanadium oxides in the oxidation of hydrocarbons by molecular oxygen

Structural-morphological transformations of molybdenum-vanadium mixed oxide catalysts of varying composition in the oxidation of hydrocarbons are studied by X-ray diffraction analysis, electron microscopy, electron paramagnetic resonance technique, and Raman scattering spectroscopy. It is shown that the catalytic reactions, which are analyzed in detail for oxides of various compositions, cause a considerable restructuring of the mixed oxides.

Oxidation of benzene on a vanadium-molybdenum catalyst in the presence of thiophene

The catalytic oxidation of benzene by air oxygen on a vanadium-molybdenum mixed oxide (1 − x)V2O5 · xMoO3 (x = 0.25) over a temperature range of 200–320°C is studied. It is shown that the introduction of small amounts of thiophene into benzene inhibits the oxidation to maleic anhydride in this temperature range. It is established that the operation of the catalyst is accompanied by significant changes in its phase composition and morphology, with a few first operation cycles being characterized by a high conversion of benzene. A possible mechanism of the process is proposed.