Russian Journal of Inorganic Chemistry最新文献

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.

Catalysts for an environmentally friendly method for hydrogen production (free from carbon oxide emissions) based on decomposition of methane were proposed. The catalysts represented iron-containing systems supported on a carbon material (biochar). The active component (Fe) was deposited by the incipient wetness impregnation method from a solution of iron(III) nitrate nonahydrate. The produced catalytic systems were tested in the decomposition of methane and studied by physicochemical methods of analysis (Raman spectroscopy, powder X-ray diffraction, transmission electron microscopy, elemental analysis, and atomic absorption analysis). The catalysts were found to have a graphite-like carbon structure accommodating uniformly distributed iron nanoparticles. The catalytic activity of the obtained systems in the temperature range of 500–850°C was determined. The maximum conversion of methane (12.2%) was observed at 700°C in the presence of iron-containing biochar synthesized at 250°C. The carbon product formed during the experiment consisted of carbon nanotubes and onion-shaped carbon.

Solid solutions of Co_1–xCu_xCr₂S₄ (х = 0–0.6), spanning the compositional range between the ferrimagnet СоCr₂S₄ (T_C = 222 K) and the ferromagnet CuCr₂S₄ (T_C = 377 K), were synthesized via a solid-state reaction. Their magnetic properties were studied using a AC magnetic susceptibility measurement method in the temperature range of 2–300 K under an alternating magnetic field with an amplitude of 1 Oe at various frequencies (100, 1000, 5000, and 10 000 Hz). The substitution of Co by Cu from x = 0 to x = 0.6 was found to increase the magnetic ordering temperature from 222 K to 287 K. The nature of the magnetic phase transitions was determined, revealing a transition to a frustrated spin-glass state in the sample with x = 0.05.

A combined quantum-chemical and molecular dynamics study of atomic layer etching of amorphous zinc oxide by β-diketones—acetylacetone, 1,1,1-trifluoroacetylacetone, and 1,1,1,5,5,5-hexafluoroacetylacetone—was carried out using the ORCA 6.0.1 and LAMMPS software packages. Within the framework of density functional theory at the PBE-D3BJ/def2-SVP level, the energy parameters of adsorption and desorption were investigated, and the induced surface stress was quantitatively evaluated. It has been found that acetylacetone induces the highest surface stress (1.62 eV) and enables spontaneous etching due to its low desorption energy (2.10 eV). The fluorinated derivatives exhibit a self-limiting interaction behavior: 1,1,1-trifluoroacetylacetone, with a desorption energy of 3.27 eV, induces a surface stress of 1.05 eV, while 1,1,1,5,5,5-hexafluoroacetylacetone causes the weakest effect on the surface structure (1.01 eV) with a desorption energy of 2.53 eV. The results suggest that 1,1,1-trifluoroacetylacetone can be considered the most suitable precursor for controlled atomic layer etching of zinc oxide.

The interaction of bis(dioxane) and bis(tetrahydropyran) derivatives of iron(II) bis(dicarbollide) [8,8'-{O(CH₂CH₂)₂Х}₂-3,3'-Fe(1,2-C₂B₉H₁₀)₂] (Х = O, CH₂) with pyridine in an inert atmosphere has been studied. It has been found that the ring-opening of oxonium cycles proceeds stepwise, with the formation of the corresponding mono- and dipyridinium iron(II) complexes. Using the bis(dioxane) dipyridinium derivative as an example, it was found that, when in solution, oxidation of the resulting products to the corresponding paramagnetic complexes of iron(III) is possible. This approach opens the way to obtain bifunctional iron bis(dicarbolide) derivatives with different substituents. The obtained compounds have been characterized by multinuclear NMR and IR spectroscopies, as well as high-resolution mass spectrometry. The structure of the symmetrical dipyridinium iron(II) complex [8,8'-(C₅H₅NCH₂CH₂OCH₂CH₂O)₂-3,3'-Fe(1,2-C₂B₉H₁₀)₂] was determined by single crystal X-ray diffraction.

This study presents a simple and efficient method for synthesizing nanocrystalline zinc oxide using glycerate precursors. Zinc glycerates were obtained through thermal treatment of a solution of zinc acetylacetonate monohydrate in glycerol, followed by additional thermal processing, which resulted in the formation of nanocrystalline ZnO. The synthesized ZnO nanoparticles were characterized using XRD, SEM, and DTA/DSC techniques. The gas-sensing properties of ZnO toward a wide range of analyte gases were investigated. It was demonstrated that nanocrystalline ZnO exhibits high sensitivity and selectivity to NO₂. The proposed approach opens new prospects for the development of cost-effective and efficient gas sensors based on semiconductor oxides.