Structural and optical characteristics of CdxZn1−x S nanoparticles stabilized in aqueous solutions of polymers

The structural and optical characteristics of Cd_xZn_1−xS nanoparticles, produced in aqueous solutions of sodium polyphosphate, polyvinyl alcohol, and gelatin, were studied. It was shown that the stoichiometric ratio of Cd(II) and Zn(II) in the nanoparticles can differ from that in the initial mixture. It was established that the main factors determining the final size of the Cd_xZn_1−xS nanoparticles are the nature and concentration of the polymer, the ratio of the initial concentrations of the reagents, and the temperature and duration of the post-synthesis treatment of the colloids. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 3, pp. 168–172, May–June, 2006.     

Effect of the Vanadium Content in V2O5/SiO2 Catalysts on Their Activity and Selectivity in the Partial Oxidation of Methane

The effect of the vanadium content on the catalytic characteristics of samples of V₂O₅/SiO₂, prepared by molecular layering, was investigated. It was shown that in the region of relatively small vanadium contents in the catalyst its surface concentration does not affect the selectivity of the process. The obtained relation between the initial selectivity and the relative reactivity of formaldehyde and the surface density of oxide-vanadium groups in the deposited catalyst is discussed.     

Photocatalysis by ZnS nanoparticles of the formation of ZnS/Au heterostructure in the reduction of complex ions of gold

The photocatalytic activity of ZnS nanoparticles during the reduction of the KAu(CN)₂ complex was found. The spectral characteristics of the nanocomposite ZnS/Au⁰ and also the principal kinetic relationships involved in its formation were studied. It was shown that the photoreaction has equilibrium character resulting from oxidation of the obtained gold by holes in the valence band of the zinc sulfide. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 41, No. 6, pp. 343–347, November–December, 2005.     

Immobilization of the enzymeL-asparaginase fromE. coli on polysaccharides. VI. Preparation and properties of polymeric derivatives based on dextran carbonates

Methods have been developed for obtaining soluble and insoluble dextran carbonates. The addition of the latter to E. coli L-asparaginase has given water-soluble, gel-like, and insoluble forms of the immobilized enzyme. The influence of the bound polymer on some physicochemical properties of L-asparaginase has been determined. The antileukemic action of soluble dextran derivatives of L-asparaginase has shown that their efficiency is greater than that of the native enzyme.A. Kirkhenshtein Institute of Microbiology, Latvian Academy of Sciences, Riga. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 432–436, May–June, 1993.     

The mechanisms of the formation of by-products in the catalytic synthesis of C-alkylimidazoles from diamines and carboxylic acids

The formation of 1-ethyl-2-methylimidazole (1-Et-2-MI) and 1-ethyl-2-methylimidazoline (1-Et-2-MIN), intermediates in the synthesis of 2-methylimidazole (2-MI) from ethylenediamine (EDA) and AcOH in the presence of a platinum-on-alumina catalyst, was studied. Using CH₃ ¹⁴COOH the incorporation of two acetate units into 1-Et-2-MI and 1-Et-2-MIN molecules was demonstrated. The same products were also obtained on dehydrogenation of 2-methylimidazoline (2-MIN) under mild conditions (220–230 °C). A part of the latter is transformed to N-ethyl ethylendiamine (EEDA) and EDA. These facts indicate that both 1-Et-2-MI and 1-Et-2-MIN result from hydrogenolysis of the imidazoline ring with subsequent ethylation. A reverse reaction, the C₅-cyclization of EEDA, was also observed. The formation of 2-MI is favored by increasing temperature.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 937–940, May, 1993.     

Structure and spectral-optical characteristics of Se,Se/CdS,and Se/Cd<Subscript>0.5</Subscript>Zn<Subscript>0.5</Subscript>S nanoparticles,stabilized in polymer-containing media

A method was proposed for the production of colloidal nanoparticles of selenium stabilized by polymers and surfactants, and their structural and optical characteristics were studied. It was shown that during the deposition of CdS and Cd_0.5Zn_0.5S on the surface of the Se nanoparticles followed by dissolution of the selenium with sodium sulfite it is possible to obtain network “nanoframeworks” with size 30–50 nm, formed by CdS or Cd_0.5Zn_0.5S particles measuring 3–5 nm. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 1, pp. 24–29, January–February, 2007.     

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.     

Influence of the composition of Co-containing perovskites on their catalytic properties in the conversion of methane into higher hydrocarbons in non-stationary conditions

The oxidative coupling of methane in a periodic regime was studied using Co-containing perovskites as solid oxidants. Partial substitution of strontium with alkali metals in the perovskite SrCoO₃ increased the activity and selectivity of the catalyst with respect to higher hydrocarbons. The substituted catalysts continued to work after many oxidation-reduction cycles. 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. 36, No. 1, pp. 47–52, January–February, 2000.     

Structure and electrophysical properties of a lead iron niobate-based amorphous material

An amorphous material based on lead iron niobate (PFN) is studied by X-ray diffraction and dielectric and Mössbauer measurements over a wide temperature range. The atomic structure of amorphous PFN is found to be substantially disordered, which suppresses the transitions into ordered states in the electric and magnetic dipole subsystems that are inherent in crystalline PFN. The dependence of electrical conductivity σ on field frequency ω is shown to correspond to the law σ ～ ω ^s , where parameter s decreases linearly with increasing temperature. This law corresponds to a hopping carrier transfer mechanism that is correlated due to the Coulomb interaction.