Russian Journal of Inorganic Chemistry最新文献

The effect of the surface roughness (160 or 45 nm) of polycrystalline α-Al₂O₃ wafers on the composition, structure, and properties of titanium oxide coatings formed on the wafers upon chemical assembly in a set number (up to 600) of molecular layering (ML) cycles comprising an alternating exposure of the substrate to titanium tetrachloride and water vapor was studied. X-ray fluorescence analysis and scanning electron microscopy (SEM) showed that the titanium concentration was higher in samples with the higher initial surface roughness. The coordination states of titanium in the oxide coatings according to UV–Vis diffuse reflectance (UV–Vis DRS) spectra correspond to aluminotitanate, tetrahedral, and anatase-like structures, the ratio between which depends both on the coating thickness and on the substrate surface roughness. Atomic force microscopy (AFM) showed that layers consisting of larger particles were formed on substrates of higher roughness. At the same time, as the thickness of the coating increased, its roughness increased, too, and the oxygen gas sensitivity in the sensors increased.

New hybrid materials based on Ag, Cu, AgCu nanoparticles and their conjugates with quercetin were obtained using an environmentally friendly method of metal-vapor synthesis (MVS). The composition and electronic state of the nanocomposites were studied by XPS, powder X-ray diffraction, and SEM/EDX. It was found that modification of metals with flavonoid leads to stabilization of smaller particles in the conjugate compared to metal powders. Powder X-ray diffraction studies showed that the average crystallite size of metals upon introduction of quercetin decreases from 4.1 to 3.6 nm for Ag and from 8.7 to 4.8 nm for Cu. According to XPS analysis, the bimetallic composites and their conjugates consist primarily of silver in its metallic state (Ag⁰), with minor contributions from Ag⁺ and silver acetate species. Copper, however, is present in a mixture of oxidation states: Cu⁰, Cu⁺, an Cu²⁺. The data indicate that the bimetallic nanoparticles form a solid solution with a disordered structure, characterized by the presence of Ag–Cu, Ag–O–Cu, and Ag–O–Cu–O– bonds.

Powders of Mg₃(PO₄)₂·22H₂O, MgHPO₄·3H₂O, NaMg₄(PO₄)₃·xH₂O, and NH₄MgPO₄·6H₂O have been synthesized by precipitation at 25°C from solutions of different salts, magnesium oxide, and phosphoric acid. Depending on precursors, products of different compositions were obtained at pH 9 and characterized using X-ray powder diffraction, X-ray electron spectroscopy, and static light scattering. The selection of sintering mode for printed sample was carried out using TG and DTA to determine temperature range to remove organic component of printing suspension. A fundamental possibility has been shown for preparing porous ceramics by 3D printing from magnesium orthophosphate obtained by solution method with maximal amount of crystal water (Mg₃(PO₄)₂·22H₂O) and average size of agglomerates of 28.3 μm and Kelvin structure. This method opens a prospect for the use of ceramics based on magnesium phosphate, in particular magnesium orthophosphate, in regenerative medicine.

Nickel-rich layered oxides are currently the preferred cathode active materials (CAMs) for lithium-ion batteries. However, the performance of CAMs is known to degrade when they are stored in ambient air due to surface reactions of the material containing residual lithium ions with atmospheric moisture and carbon dioxide to form lithium hydroxide and lithium carbonate. The residual lithium compounds on the CAM surface increase manifold upon long-term storage in contact with the atmosphere (ambient storage), with an attendant degradation of the electrochemical performance properties of the CAM, in particular, a 25% decline in specific discharge capacity at 0.1 C current density and a 50% decline at 1 C current density. New methods are proposed for the regenerating calcination of CAMs that have been stored in contact with air, and the addition of supplementary amounts of LiOH helps to achieve the highest capacitive characteristics of stored and then regenerated CAMs.

A comparative analysis of the surface processes of atomic layer deposition (ALD) of AlMo_xO_y using H₂O, molybdenum dioxide (MoO₂Cl₂), and trimethylaluminum (Al(CH₃)₃, TMA) or aluminum chloride (AlCl₃) has been carried out. The effect of the aluminum precursor nature on the composition and oxidation state of molybdenum in the films has been studied. According to X-ray photoelectron spectroscopy evidence, the molybdenum content in the obtained films is lower than the aluminum content. Molybdenum with oxidation states Mo⁺⁶, Mo⁺⁵, and Mo⁺⁴ was also detected in the films; the ratio of the atomic concentration of Mo⁺⁶ to the reduced forms was 0.76 : 1 in the case of the TMA process, and 6.3 : 1 in the case of AlCl₃. Replacing TMA with AlCl₃ in the ALD of AlMo_xO_y decreased the amount of reduced Mo in the films, as well as the total molybdenum content. To evaluate the thermodynamic parameters of the proposed reactions for the ALD processes using AlCl₃ and TMA, quantum-chemical DFT calculations were performed, which enabled the explanation for the observed differences in the films.

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.