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.     

Photochemical formation of semiconducting nanostructures

Existing data on photochemical and photocatalytic approaches to the formation of semiconducting nanoparticles and also binary semiconducting nanostructures and nanocomposites of semiconductors with metals and polymers are reviewed. The nature of the effect of irradiation on the synthesis and properties of the obtained nanostructures and the possibility of photocatalytic control of the structural and spectral parameters of nanostructural semiconducting systems are examined. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 44, No. 4, pp. 199–220, July–August, 2008.     

Synthesis and characterization of ZnO-doped cupric oxides and evaluation of their photocatalytic performance under visible light

ZnO–CuO binary oxide photocatalysts were synthesized by the liquid phase coprecipitation method. The catalysts were characterized by X-ray diffraction, transmission electron microscopy and UV–vis spectroscopy. The photocatalytic activity of the ZnO–CuO nanocomposites was estimated on the basis of decoloration of methyl orange dye under visible light. The effects of parameters such as calcining temperature, amount of catalyst and pH on the photocatalytic degradation efficiency of methyl orange solutions were investigated in detail. The maximum photocatalytic activity was obtained on ZnO–CuO nanocomposites with a calcining temperature of 350 °C, using a catalyst amount of 0.056 g/L and a pH of 7.5. The visible light-driven capability of ZnO–CuO nanocomposites is much better than that of commercially available TiO₂ photocatalysts under comparable conditions.     

Mechanism of reactions of photocatalytic synthesis of chlorohydrins

A mechanism of photocatalytic synthesis of chlorohydrins from olefins and peroxo complexes of titanium (IV) is proposed. It consists of formation of radical-containing complexes, their reactions with olefins, and decomposition of the α-oxides obtained by hydrogen chlorides. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prosp. Nauki, 252039 Kiev, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 33, No. 1, pp. 17–21, January–February, 1997.     

Photocatalysis of reaction of hydrogen production by cadmium and zinc sulfide nanoparticles incorporated into silicate matrices

Novel nanostructural materials have been prepared, their diffuse reflection spectra have been studied, and their electrophysical characteristics (width of forbidden band, position of conduction band) have been evaluated. It has been established that these materials have high photocatalytic activity, and the factors influencing this activity have been examined. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of the Ukraine, 31 Nauka Prospect, 252039 Kiev, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 33, No. 1, pp. 32–35, January–February, 1997.     

CdS nanoparticles in porous silicate glasses: energy characteristics, photocatalytic activity, and the effect of silver ion doping

Energy diagrams were constructed for CdS nanoparticles doped with silver ions and incorporated into silicate matrices, which are new nanostructural materials. The effect of the amount of silver introduced on the efficiency of the photocatalytic evolution of hydrogen from aqueous sulfide-sulfite solutions was demonstrated, and the interrelationship between the photocatalytic activity of these materials and their energy characteristics was established. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 34, No. 6, pp. 360–365, November–December, 1998.     

Photocatalytic reduction of methylene blue by formaldehyde in the presence of titanium dioxide and cadmium sulfide sensitized by (1-phenyl-5,6-benzoquinoline-2)-2,4-dihydroxystyryl iodide

New heterostructures of a dye, (1-phenyl-5,6-benzoquinoline-2)-2,4-dihydroxystyryl iodide, with TiO₂ and CdS were obtained and their photocatalytic activity in the reduction of methylene blue by formaldehyde was established under different irradiation conditions and with different dye concentrations. Explanations for the behavior found are proposed. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 44, No. 1, pp. 40–45, January–February, 2008.     

Photoelectrochemical behavior of nanostructural composites based on polycrystalline cadmium sulfide

Nanostructural composites can be used as suspension electrodes; they are made by substitution cadmium(II) at the surfaces of CdS microcrystals for Cu(I, II), Fe(III), Bi(III), and Sb(III). Features are considered in the photoelectrochemical action mechanism of the various nanocomposites. 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. 79–82, March–April, 1999.     

An effective nanocomposite of polyaniline and ZnO: preparation,characterizations, and its photocatalytic activity

The polyaniline/zinc oxide (PANI/ZnO) nanocomposites were prepared by in situ polymerization of aniline monomer with ZnO nanomaterials and applied as a photocatalyst for the degradation of methylene blue (MB) dye. The morphological observations elicited the agglomerations of PANI sheets which occurred due to the interaction between PANI and ZnO nanomaterials in PANI/ZnO nanocomposites. As compared to pristine PANI, the UV–vis spectra exhibited that the absorption peak of π–π* transitions considerably shifted to higher wavelength at 360 nm from 325 nm in the nanocomposites. The photocatalytic activity results indicated the substantial degradation of MB dye by ~76% over the surface of PANI/ZnO nanocomposite catalyst under light illumination. The PANI/ZnO nanocomposites showed three times higher photocatalytic activity to MB dye degradation compared to pristine PANI might due to high photogenerated electron (ē)–hole (h⁺) pairs charge separation.     

Chemical synthesis of Ni/TiO<Subscript>2</Subscript> nanophotocatalyst for UV/visible light assisted degradation of organic dye in aqueous solution

The Ni/TiO₂ nanoparticles with different Ni dopant content were prepared by a modified sol–gel method. The structure and photoinduced charge properties of the as-prepared catalysts were determined using X-ray diffraction, transmission electron microscopy, UV–vis diffuse reflectance spectroscopy and surface photovoltage spectroscopy techniques, and the photocatalytic efficiency of these catalysts was tested using an organic dye. It was shown that Ni modification could greatly enhance the photocatalytic efficiency of these nanocomposite catalysts by taking the photodegradation of methyl orange as a model reaction. With appropriate ratio of Ni and TiO₂, Ni/TiO₂ nanocomposites showed the superior photocatalytic activity than the single TiO₂ nanoparticles. Surface photovoltage spectra demonstrated that Ni modification could effectively inhibit the recombination of the photoinduced electron and holes of TiO₂. This electron–hole pair separation conditions are responsible for the higher photocatalytic performance of Ni/TiO₂ nanocomposites in the visible region of electromagnetic spectrum.     

Adsorption and photocatalytic properties of nanodimensional titanium–zinc oxide composites

We have prepared nanodimensional mesoporous titanium–zinc oxide composites consisting of anatase, rutile, and zincite. The pore volume and specific surface of the samples increase with increasing zincite content, while the pore radius decreases. The titanium–zinc oxide nanocomposites display greater photocatalytic activity than ZnO or TiO₂ and the rate constants for the decomposition of substrates increase with their increasing adsorption.     

The electronic structure of the bases of cyanine dyes and the barriers of their conformational transformations

The equilibrium geometry and electronic transitions of cyanine dyes and their bases and also the barriers to rotation of the terminal groups in the ground and excited states were calculated in the AM1 approximation. It was found that in contrast to the cyanine dyes the bases are closer in electronic structure to conjugated systems of the polyene type. The calculated barriers to rotation are significantly higher in the bases than in the dyes. Institute of Organic Chemistry, National Academy of Sciences of Ukraine, 5 Murmanskaya ul., Kiev 253094, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 4, pp. 222–226, July–August, 1999.     

Hierachical classification of physiologically active substances

In a first attempt at a hierarchical classification of physiologically active substances, these substances were divided into two classes corresponding to their effect on the main cellular signaling systems. That some general principles of the chemical structure of drugs do exist has been demonstrated using quantum chemistry methods, artificial intelligence, and biophysical approaches. Institute of Bioorganic and Petroleum Chemistry, National Academy of Sciences of Ukraine, 1 Murmanskaya ul., Kiev 253094, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 34, No. 4, pp. 199–213, July–August, 1998.     

Polymer nanocomposites based on polyamide 6 modified with fulleroid fillers

Polymer nanocomposites based on polyamide and fulleroid modifiers are synthesized through in situ polymerization, and their mechanical and electric properties are studied. After introduction of 0.001–0.1 wt % fulleroid modifiers, Young’s modulus and the strength of thermoplastic composites increases by 15–20%, practically independently of the amount of filler. This circumstance is due to the fact that the introduction of fulleroid fillers causes selective crystallization of polyamide 6 only in the α form. The introduction of fullerene fillers considerably improves the tribological characteristics of polymer nanocomposites, thereby decreasing the friction coefficient by a factor of 2. The electric properties of nanocomposites are studied also.     

Mechanisms of the coupling of one-and two-electron reactions in chemical and biochemical processes

The mechanisms of chemical and biochemical reactions in which one-electron stages ae coupled with two-electron stages are examined. The mechanisms of the coupling of the one- and two-electron stages in the electron-transport systems of the living cell are discussed on the basis of an analysis of chemical models. Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Sciences of Ukraine, 1 Murmanskaya ul., Kiev 253094, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 3, pp. 133–144, May–June, 1999.     

Optimization and Calculation of the EuCl<Subscript>3</Subscript>–MCl (M = Na,K, Rb,Cs) Phase Diagrams

By using the CALPHAD technique, an optimization of the binary EuCl₃–MCl (M = Na, K, Rb, Cs) systems has been carried out. To describe the Gibbs energies of liquid phases in these systems the new modified quasi-chemical model was used in the pair-approximation for short-range ordering. From the measured phase equilibrium data and the experimental thermo-chemical properties, the EuCl₃–MCl phase diagrams were optimized and calculated. A set of thermodynamic functions has been optimized based on an interactive computer-assisted analysis. The calculated phase diagrams and thermodynamic data are self-consistent.     

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.     

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.     

Synthesis and properties of inclusion compounds: Zeolites containing encapsulated transition-metal complexes

Published data and original results are surveyed on the synthesis, structure, and properties of a new type of inclusion compounds based on porous substances (zeolites) containing encapsulated transition-metal complexes. 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. 4, pp. 199–214, July–August, 1999.     

Influence of alkaline earth metals on the activity and sulfur stability of zeolites in the Nox−C3−C4 hydrocarbon selective reduction of no to nitrogen (SKV) process

The results of the influence of alkaline earth metal and magnesium cations on the activity and sulfur stability of catalysts based on synthetic mordenites and high-silicon zeolites with pentasil structures on the selective reduction of nitrogen oxides with C₃−C₄ hydrocarbons are presented. Doping the H-form of mordenite and pentasils with Ca, Sr, Ba, and Mg cations increased their activity and stability with respect to sulfur dioxide in the selective reduction of NO_x with a propane-butane mixture. L. V. Pisarzhevskii Institute of Physical Chemistry, Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 5, 317–321, September–October, 1999.