Russian Journal of Inorganic Chemistry最新文献

New collagen–chitosan materials containing Ag nanoparticles, promising for the design of wound dressings, were synthesized from a porous hybrid material derived from collagen and chitosan in the powder and gel forms. An original process concept for the formation of hybrid biomaterials is presented. The materials were synthesized using powders of collagen and chitosan polymers pre-modified with Ag nanoparticles obtained by metal vapor synthesis. The metal-containing powder systems were used as precursors for the preparation of gels, which were freeze-dried to give porous hybrid materials. Nanocomposites were studied using XPS, PXRD, and SEM/EDX methods. Homogeneous distribution of Ag nanoparticles over the collagen–chitosan composite bulk was found, and the composition and electronic state of the metal in the material was examined.

Liquid-phase hydrogenation of styrene at the atmospheric pressure in aqueous media was studied on a series of Ni/SiO₂ supported nickel catalysts containing various nickel amounts (from 6 to 28 wt %). The effects of textural characteristics of the catalysts and its controlled deactivation with sulfide ions on the catalytic activity were studied. The dispersion increased in response to decreasing nickel content, but the active surface area of the reduced metal decreased. Partial deactivation was simulated by addition of a controlled amount of Na₂S in order to quantify the density and activity of various types of catalytic centers. The complete deactivatation of one Ni⁰ atom on the surface required 0.6 to 1.2 S^2– ions on the average, depending on the morphology of the catalyst. The poison resistance of the catalyst was analyzed in terms of the turnover frequency (TOF) and turnover number (TON_deact). Our results expand the understanding of deactivation schemes and can be used to develop new-generation catalysts that would be resistant to sulfur-containing impurities in hydrogenation reactions.

The dehydration of the hydrate of the neutral spin-crossover- (S = 5/2 ↔ S = 1/2) complex [Fe^III(Hthpy)(thpy)]·H₂O (1) based on the pyruvic acid thiosemicarbazone ligand (H₂thpy) has been studied by temperature-dependent ⁵⁷Fe Mössbauer spectroscopy. It has been shown that the release of water from the structure of polycrystalline sample 1 in the temperature range 92–160°С is associated with the formation of the neutral complex [Fe^II(Hthpy)₂] stabilized in the high-spin state (S = 2). A comparative analysis of the spectral parameters of complex 1 and the anhydrous neutral spin-crossover complex [Fe^III(Hthpy)(thpy)] (2) has revealed that complex 2 retains its spectral characteristics when heated in air in a similar temperature range.

Phase-change heat storage materials (PCMs) based on Zn(NO₃)₂·6H₂O, which undergoes phase transition in the range 25–40°C, were developed. The most stable composition was the one comprised of Zn(NO₃)₂·6H₂O/Co(NO₃)₂·6H₂O/expanded graphite/CMC. Its heat of crystallization with account for the heat capacity in the supercooled region was determined as 146.0 ± 7.3 and 140.6 ± 7.0 J/g and was comparable with the heats of melting before and after 500 thermal cycling cycles, equal to 147.4 ± 4.4 and 130.6 ± 3.9 J/g, respectively. The composition tested in a prototype electric underfloor heating film showed that the energy consumption for heating was 67% lower than for the heating film without the developed material.

A new method for the determination of water-soluble carbohydrates (glucose and fructose) using cross-linked polyvinyl alcohol–magnetite sensing composite films was developed. A digital image colorimetry technique with image processing in the RGB space was proposed for recording the analytical response of the sensing films. The water-soluble carbohydrates were determined in a phosphate borate buffer solution at pH of 8.5 and at a sodium tetraborate concentration of 0.05 moL/L. The film impregnated with a solution of iron salts for 2 min prior to precipitation of Fe₃O₄ particles proved to be most sensitive. The limit of detection of glucose and fructose in aqueous solutions was 11 mmol/L. The proposed approach was tested in analysis of natural monofloral honey samples. This method for determination of glucose and fructose does not require special laboratory equipment to measure the analytical response and can serve as an alternative to the photometric ferricyanide method for glucose and fructose determination.

Promising energy storage materials based on ZnCr₂O₄ spinel, synthesized on carbon fiber matrices, remain insufficiently studied in the context of their application in electrochemical supercapacitors. In the present study, the title materials have been synthesized by direct precipitation methods, sol–gel synthesis, and hydrothermal treatment followed by thermal processing. The main attention has been focused on the comprehensive investigation of the morphology, phase composition, and electrochemical characteristics of samples. The materials have been analyzed using X-ray powder diffraction, scanning electron microscopy, energy-dispersive spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The samples obtained by the sol–gel method with high-temperature treatment under an argon atmosphere have demonstrated high phase purity of the spinel, well-developed porous structure, and maximum specific capacitance. Impedance studies have revealed low resistance values indicating efficient charge transfer. The research results confirm the high potential of ZnCr₂O₄/carbon materials for the development of efficient and durable supercapacitors of new generation.

Thin zinc oxide films were synthesized via the AACVD method, with the synthesis temperature being the variable parameter, ranging from 350 to 500°C. The obtained ZnO particles were found to have a wurtzite structure with an average crystallite size of 26 ± 4 nm. Morphological analysis revealed that within the temperature range of 400–450°C, continuous films with an average particle size of 52 ± 14 nm are formed, whereas at synthesis temperatures of 350–375 and 475–500°C, films with an island-like morphology and an average size of 51 ± 13 nm are observed. The optical properties of the films were investigated, yielding estimated band gap values of 3.31–3.34 eV. A growth mechanism dependent on the synthesis temperature is proposed. The chemosensing properties of the films were studied at operating temperatures of 150–350°C using a wide range of analyte gases: CO, NH₃, H₂, CH₄, C₆H₆, ethanol, acetone, and NO₂. The thin films demonstrated high sensitivity (4–100 ppm) to volatile organic compounds (VOCs) at an operating temperature of 350°C. It was established that the sample with the highest surface roughness exhibited the greatest sensor response. The influence of humidity on the magnitude and shape of the signal obtained during acetone detection was also investigated.

Nickel-containing cubic pyrochlore Bi₂NiNb₂O₉ (space group (Fdbar {3}m), a = 10.53657(6) Å) was synthesized by the citrate method. At the synthesis temperature of 1050°C, low-porosity ceramics with unclear grain boundary outlines are formed. The disordered structure of pyrochlore (space group (Fdbar {3}m), a = 10.53784 Å, Z = 4) was refined by the Rietveld method based on X-ray powder diffraction data. The studied pyrochlore belongs to isotropically expanding oxide compounds with an average value of the thermal expansion coefficient of (6.4 × 10^–6)°C^–1 in the range of 30–750°C. Above 1110°C, thermal dissociation of Bi₂NiNb₂O₉ occurs with the formation of the impurity phase NiNb₂O₆. Bi₂NiNb₂O₉ is characterized by a high activation energy of 1.43 eV and a frequency- and temperature-independent permittivity of 144 (up to 300°C), low dielectric losses of ∼0.002 at 1 MHz. The studied ceramics can be used as a high-frequency dielectric material in the creation of multilayer ceramic capacitors.

Ultra-high-temperature ceramics based on zirconium and hafnium diborides are of great scientific and technical interest, as they can be very promising, including as components of descent vehicles for space exploration. To study the behavior of these ceramics under the influence of high-speed flows of dissociated gases of complex composition and to determine the effect of modifying the ZrB₂–HfB₂–SiC system with carbon nanotubes, the process of surface degradation under the influence of a subsonic flow of dissociated nitrogen containing 5 mol % CO₂ was examined. Despite the relatively low CO₂ content in the nitrogen plasma, the surface oxidation process dominated the conversion of the initial ZrB₂/HfB₂ into solid solutions based on monocarbonitrides of these metals. In this case, it was noted that a protective layer of silicate glass does not form on the surface, unlike similar materials under the influence of subsonic flows of dissociated air at temperatures <1750–1800°C.