The effect of PbS nanoparticles on the formation of PbSe in aqueous solutions of sodium selenosulfate and lead(II)

It was established that PbS nanoparticles significantly increase the rate of formation of lead selenide during the reaction of Pb(NO₃)₂ and Na₂SeSO₃ in aqueous solutions of polymers. It was shown that the reaction product consists of PbS/PbSe nanoparticles with a “PbS core-PbSe shell” structure. A correlation was found between the forbidden band widths of the PbS nanoparticles and the PbS/PbSe nanostructures formed during the reaction. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 6, pp. 339–344, November–December, 2006.     

Molecular design in photocatalysis: Physicochemical principles for designing high-efficiency photocatalytic oxidation-reduction systems

We generalize the results of our research and develop the concept of molecular design as a strategy for controlling photocatalytic processes by designing organized systems in which all the conversions connected with electron transfer are coordinated.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 30, No. 4, pp. 175–191, July–August, 1994.We would like to express our deep appreciation to our colleagues A. V. Korzhak, N. F. Guba, and S. V. Kulik, the coauthors of our original papers which were the basis for this generalization.     

Photochemical properties of peroxo complexes of titanium,intermediate products in the photocatalytic liquid-phase oxidation of alcohols

A study has been made of the photochemical reactions of titanium(IV) peroxo complexes formed in the reaction of titanium tetrachloride with hydrogen peroxide in alcoholic solutions and which are characterized by intense charge transfer bands at 360–425 nm. Irradiation of the solutions with light of = 254 nm leads to the decomposition of the titanium(IV) peroxo complexes, the formation of titanium(III) compounds, as well as the oxidation of the alcohol to aldehyde. In the irradiated frozen solutions associated complexes of titanium(III), organic free radicals formed from the alcohol molecule, as well as peroxy radicals have been identified by EPR. Irradiation with light corresponding to the longwave band of the peroxo complexes leads to their decomposition but titanium(III) compounds and alcohol oxidation products are not formed in this case. In irradiated frozen solutions the formation of paramagnetic titanium(IV) complexes containing the fragment Ti...O ₂ has been established, as well as other paramagnetic particles identified tentatively as coordinated Ti...O ₂ ^· radicals or radical pairs. It is shown that the decomposition of hydrogen peroxide in the presence of titanium(IV) compounds is photocatalytic.Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 24, No. 1, pp. 67–74, January–February, 1988.     

CdS Nanoparticle Photocatalysis of the Chain Oxidation of Sulfite Ions by Molecular Oxygen

High photocatalytic activity was found for colloidal cadmium sulfide nanoparticles in the radical chain oxidation of sulfite ions by molecular oxygen in aqueous solution. The kinetics of this reaction was studied and a mechanism was proposed, which is in satisfactory accord with the experimental data.     

Photopolymerization of Butyl Methacrylate in the Presence of Nanoparticles of ZnO,Sensitized to Visible Light with Xanthene Dyes

The photopolymerization of butyl methacrylate in isopropanol with participation of nanoparticles of wide-gap semiconductor ZnO has been studied. The possibility of sensitizing ZnO nanoparticles to visible light with a series of halogenated fluoresceins has been established. The rate of photoinitiation of polymerization in the systems studied is principally determined by the rate of electron transfer from the photoexcited molecule of the sensitizer into the conduction zone of the semiconductor nanoparticles.     

Synergism in an organized photocatalytic system based on cadmium sulfide and titanium complexes

A nonadditive acceleration of oxidation-reduction processes has been observed in systems containing semiconductors and metal complex photocatalysts. The conditions necessary for synergism to occur have been analyzed for the example of the generation of H2 from aqueous alcoholic media with the participation of CdS and titanium(lV) complexes.Translated from Teoreticheskaya i Éksperimental'naya, Khimiya, Vol. 28, Nos. 5–6, pp. 407–410, September–December, 1992.The authors thank the Ukraine State Committee on Science and Technologyfor funding this study from the Fundamental Research Fund.     

Photopolymerization of Butyl Methacrylate Initiated by Hydrated Ferric Oxide Nanoparticles

Colloidal hydrated ferric oxide nanoparticles in 2-propanol solution are efficient initiators of the polymerization of butyl methacrylate by the action of UV and visible light. The kinetics of this reaction was established and elucidated. A mechanism of the photoinitiated polymerization involving photoexcited semiconductor particles was proposed in accord with the experimental and literature data.     

Photochemical reduction of sulfur in the presence of ZnO nanoparticles in ethanol

The photochemical reduction of sulfur by the action of ZnO nanoparticles of various shapes and sizes under the conditions of stationary and pulsed photoexcitation was studied. The mechanism of this process was proved; the main route to the formation of the reaction product zinc sulfide is reduction of the sulfur by photochemically produced metallic zinc. It was demonstrated that ordered agglomerates of ZnS nanoparticles in the form of nanotubes and nanorods are formed in the systems based on ZnO nanorods.     

Preparation and spectral properties of high-efficiency luminescent polyethylenimine-stabilized CdS quantum dots

Feasibility was demonstrated for obtaining ultrasmall colloidal CdS nanoparticles (with diameter about 2 nm) stabilized in aqueous solution by polyethylenimine with a narrow size distribution (~10%) and luminescing at 400-600 nm (quantum yield about 10%). Complexation between Cd^II and polyethylenimine is a necessary condition for formation of such nanoparticles.     

Combination of low-temperature photolysis and ESR spectroscopy as a method for investigating nonparamagnetic complexes

The possibility of the use of ESR for investigating coordination compounds formed by ions of transition metals having no d electrons has been demonstrated on the basis of an analysis of the data obtained on the low-temperature photolysis of labile complexes of titanium(IV), vanadium(V), and molybdenum(VI). Under the proposed procedure, the d complex is converted into a d¹ complex by means of photochemical reduction under conditions which are favorable to the maintenance of the coordination sphere unchanged, its ESR spectrum is recorded, and the parameters obtained are used to characterize the composition, structure, symmetry, and degree of aggregation of the original compound in the solution. The use of this procedure is restricted to the investigation of systems in which photochemical redox conversions are realized according to an outer-sphere mechanism; however, it may also be useful in the interpretation of the results of the photolysis of compounds which undergo inner-sphere conversions.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 2, pp. 197–203, March–April, 1989.