Photocatalytic production of hydrogen from water–alcohol media with the participation of mesoporous TiO<Subscript>2</Subscript>

Samples of mesoporous TiO₂ containing 80-85% of anatase and 15-20% of rutile with average particle and pore sizes of ∼10 nm and specific surface areas of 70 m²/g were obtained. The nanohetero structures TiO₂/Cu formed during photocatalytic reduction of Cu^II exhibit photocatalytic activity in the release of hydrogen from water–ethanol mixtures. The quantum yield with respect to atomic hydrogen amounts to 1.5.     

Quantum-sized effects and the nature of the primary photoprocesses in copper(I) and copper(II) sulfide nanoparticles

The spectral and semiconductor properties of copper(I) and copper(II) sulfides in aqueous solution were studied. The colloids studied display quantum-sized effects. Two types of optical transitions, namely, indirect band-band and intraband transitions, are responsible for light absorption by the nanoparticles in the visible range. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 2, pp.92–98, March–April, 1999.     

Semiconductor heterojunctions and composites based on cadmium and bismuth sulfides as new redox catalysts

Heterojunctions and composites made of the semiconductors cadmium and bismuth sulfides have been examined as photocatalysts for producing molecular hydrogen from aqueous alcoholic solutions. Kinetic laws are derived together with the quantum yields of the reaction under various conditions and spectral characteristics of the photocatalysts.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 30, No. 4, pp. 197–201, July–August, 1994.We are indebted to the Fundamental Research Fund of the State Committee of the Ukraine for Science and Technology for support in this research.     

Preparation and optical properties of a new nanostructural material: Silver-ion-doped CdS nanoparticles in silicate matrices

Porous silicate glasses containing cadmium sulfide nanoparticles doped with silver ions have been prepared; light absorption and luminescence have been investigated; and a new general route for the cretion of nanostructural materials of this type has been mapped out. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 34, No. 5, pp. 297–301, September–October, 1998.     

Photocatalytic Reduction of Zn(II) with Participation of ZnS Nanoparticles

We have studied the photochemical processes occurring in colloidal ZnS solutions containing zinc chloride and sodium sulfite as additives. Irradiation of such systems leads to reduction of Zn(II), the rate of which increases as the size of the ZnS nanoparticles decreases. Based on analysis of the kinetic curves for the reaction, we hypothesize that photoreduction of Zn(II) is a two-electron process. __________ Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 41, No. 4, pp. 231–235, July–August, 2005.     

Optical Characteristics of Colloidal Nanoparticles of CdS Stabilized with Sodium Polyphosphate and Their Behavior during Pulse Photoexcitation

The optical and photophysical characteristics of quantum-dimensional particles of CdS stabilized in water (the oscillator force of the first exciton transition, the forbidden band width, the conduction and valence band potentials) were determined. It was established that pulse excitation of CdS nanoparticles gives rise to nonstationary bleaching of the colloid, due to the accumulation of excess electrons in the conduction band. Their amount and their consumption rate are determined by the nature and concentration of the electron donors and acceptors present in the system.     

Quantum Size Effects in Semiconductor Photocatalysis

The characteristics of photocatalytic systems based on nanostructural semiconductors, characterized by quantum size effects, are discussed. An analysis is made of the consequences of exciton quantum confinement in the volume that are significant for photocatalysis and, in particular, the increase in the energy of photogenerated charges with decrease in the particle size, the photoinduced polarization processes, and also the simultaneous display of these effects. Possible ways of further increasing the effectiveness of systems based on nanostructural semiconductors are examined. __________ Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 41, No. 4, pp. 199–218, July–August, 2005.     

Photoinduced variations in the size of nanoparticles of CdS in colloidal solutions

The possibility of decreasing the size of colloidal nanoparticles of CdS in the oxidative photocorrosion reaction in the presence of methylviologen and of increasing their size during photocatalytic reduction of sulfur in ethanol in the presence of cadmium acetate. A dependence of the quantum yield of the latter reaction on the initial size of CdS nanoparticles was observed, which was interpreted as a result of quantum size effects. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 3, pp. 170–175, May–June, 2007.