Spectral and photochemical characteristics of CdSe nanoparticles stabilized in polymer-containing media

The optical characteristics of CdSe nanoparticles, produced in aqueous solutions and polymer films in the reaction of cadmium chloride and sodium selenosulfate, were studied. The main parameters that make it possible to vary the forbidden band width were identified. The absorption, photoluminescence, Raman, and nonstationary decolorization spectra of CdSe nanoparticles of various sizes were analyzed. It was demonstrated that under the conditions of pulsed irradiation the CdSe nanoparticles are capable of accumulating excess electrons and inducing redox transformations in components of the solution (oxygen, methylviologen, and sulfite ions). __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 3, pp. 150–155, May–June, 2006.     

Photoreduction of nitrobenzene to aniline in “hybrid” photocatalytic systems

Irradiation of suspensions of CdS in water-ethanol mixtures containing nibrobenzene with light at > 320 run does not in practical terms lead to the reduction of the nitrobenzene to aniline. It has been shown that the formation of aniline occurs when solvato complexes of vanadium(III) (PhNH₂=18.1·10^–3) and vanadium(IV) (PhNH₂= 2.84·10^–3) are added to the system. The photocatalytic reduction of nitrobenzene is accompanied by oxidation of the alcohol to acetaldehyde and acetal. The proposed process mechanism includes stages and acceptance of an electron photogenerated in the semiconductor by vanadium compounds and of a hole by molecules of the alcohol and subsequent stages of reaction of the reduced forms of vanadium, and also of the ethoxy radicals with nitrobenzene, which leads to its reduction.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 5, pp. 550–557, September–October, 1989.     

New photocatalysts: Dispersed semiconductor materials with microheterojunctions

We have obtained new semiconductor materials with microheterojunctions by substitution of surface cadmium ions in CdS by Cu(I), Cu(II), and Bi(III) ions. We have shown that the photocatalytic activity of their dispersions in the reaction of evolution of H₂ from alcohol-water mixtures is considerably higher than in the original cadmium sulfide.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 29, No. 3, pp. 270–274, May–June, 1993.We would like to acknowledge Academician V. D. Pokhodenko of the Academy of Sciences of Ukraine for drawing our attention to the prospects for investigation of complex photocatalytic systems based on semiconductors with different types of conductivity.     

Photochemical Synthesis and Spectral-Optical Characteristics of ZnO/Cu and ZnO/Ag/Cu Nanoheterostructures

The photoreduction of Cu²⁺ at the surface of ZnO nanoparticles and ZnO/Ag nanostructures was investigated. The spectral characteristics of the obtained ZnO/Cu and ZnO/Ag/Cu composites were studied in relation to the reaction conditions. It was shown that the ZnO/Ag nanoparticles have higher photocatalytic activity in the reduction of Cu²⁺ ions than the individual ZnO particles.     

Photochemical and photocatalytic properties of zeolites containing titanium(iv) complexes and metallic palladium

An attempt has been made to create organized, highly efficient photocatalytic systems in the example of composite materials consisting of blocks of a metallocomplex photocatalyst and a dark-stage catalyst, assembled on a zeolite matrix. The spectral and photochemical properties of these systems have been investigated, and also their use in catalysis of hydrogen evolution from alcohol-water media. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of the Ukraine, 31 Nauka Prospect, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 34, No. 2, pp. 103–108, March–April, 1998.     

Mechanism of photolysis of peroxy complexes of titanium(IV)

Conditions were found under which radical pairs become stabilized during the photolysis of peroxy complexes of titanium(IV) in alcoholic solutions. It was shown that precursors are dimeric complexes of titanium(IV) comprising peripheral peroxy ligands as well as a peroxy bridge. Irradiation by light corresponding to the peroxy ligand — the central ion charge transfer bands, leads to the initiation of an intraspheric reaction, as a result of which two peripheral peroxy ligands undergo a one-electron oxidation, while the bridge undergoes a two-electron reduction. The radical particles (HO₂ ^. and O₂ ) formed from the peripheral peroxy ligands become stabilized at strictly delineated distances relative to one another, which are determined by the structure of the initial dimeric peroxy complex of titanium(IV).Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 24, No. 6, pp. 678–685, November–December, 1988.     

Photocatalysis of reactions involving reduction of nitrogen-containing compounds by ethanol in an organized 18-tungsten diphosphate-cadmium sulfide system

Cadmium sulfide and heteropolytungstate were found to form an organized photocatalytic system providing separation of photogenerated charges. Reduction of nitrobenzene, nitrosobenzene, and phenylhydroxylamine to aniline has been investigated in this system; kinetic patterns have been established and quantum yields of the reactions have been determined.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 30, No. 4, pp. 206–210, July–August, 1994.The authors are grateful to the Fund for Fundamental Research of the Ukrainian State Committee on Science and Technology for supporting this work.     

Sensitization of cadmium sulfide by cyanine dyes in the photocatalytic production of hydrogen

The possibility of photocatalysis of hydrogen production from aqueous alcohol mixtures by heterostructures of cadmium sulfide with dyes under the action of light with >600 nm was shown. A probable mechanism of the sensitization is proposed on the basis of an examination of the spectral, photochemical, and electrochemical data obtained.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 31, No. 6, pp. 370–374, November–December, 1995.The authors are grateful to S. V. Shinkorenko for providing the dyes that they synthesized for the first time.     

Photocatalytic Synthesis of Composite CdSe/CdS Nanoparticles

We have shown that CdSe/CdS nanocomposites can be obtained in a photocatalytic reaction with participation of CdS nanoparticles from sodium selenosulfate. We have studied the kinetic characteristics of this process in detail and have shown that its most likely mechanism includes a step involving reaction between SeSO^3/2− anions and electrons generated in the conduction band of the CdS nanoparticles during irradiation and stabilized in traps on the semiconductor surface.__________Translated from Teoreticheskaya i Eksperimental’naya Khimiya, Vol. 41, No. 3, pp. 171–175, May–June, 2005.     

Nanostructural composite photocatalysts based on polycrystalline cadmium sulfide

The results of studies of new photocatalysts—composites of cadmium sulfide with nanoparticles or thin layers of copper(I), silver(I), mercury(I), copper(II), bismuth(III), antimony(III) and iron(III) sulfides—are reviewed. The optical and electrophysical characteristics, the ranges of photosensitivity, the nature of the increased activity and the peculiarities of the photocatalytic effects are discussed. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 22039 Kiev, Science Prosp., 31. Translated from Teoreticheskiya i éksperimental'naya Khimiya, Vol. 33, No. 5, pp. 306–321, September–October, 1997.