Vol 68, No 8 (2023)

Solid solutions based on barium fluoride doped with rare earth element ions have been obtained by solid-phase synthesis. According to X-ray powder diffraction, the obtained samples have monophase fluorite structure. Increase in the concentration of rare earth element ions leads to decrease of crystal structure volume. Laser irradiation at 980 nm (radiation power of 1.2 W/cm2) produces luminescence in the visible spectral region. The presence of Yb3+ ion as sensitizer increases luminescence intensity for barium fluorides doped with Er3+ ions. Incorporation of Tm3+ ions into barium fluoride doped with Er3+ ions leads to decrease of total radiation intensity and the predominance of luminescence in the red spectral region. Color coordinates calculated from photoluminescence data by CIE 31 standard have been determined for the samples. The obtained materials of prescribed composition can transform infrared radiation into visible light.

The powdered bentonite/iron oxide composite material was synthesized by chemical co-precipitation. The grain size composition, morphology, crystal structure, porosity, and thermal stability of the obtained powder were investigated. It was established that iron oxide exists in the composite as the maghemite/magnetite solid solution with the formula Fe2.950O4. An increase in the viability of the bacterium Escherichia coli M-17 after culturing in the nutrient medium in the presence of the synthesized bentonite/iron oxide powder was found.

A new method for preparing Na1 + xZr2SixP3 – xO12 (0 < x < 3) based on pyrolysis of solution containing a mixture of organic components in rosin melt has been proposed. Effect of superstoichiometric amounts of sodium and phosphorus on the phase composition of synthesis products has been proved. It has been found that precursor for the sample of maximal purity of phase composition is prepared at molar ratio Na : Zr : Si : P = (1.15 + x) : 2 : x : (y – x), where y = 3 (1.20 + x)/(1 + x). Precursor calcination temperature is 1000°C. Different NASICON compositions without crystalline admixtures have been obtained in the range 1.5 ≤ x ≤ 2.12. The prepared samples have been studied by X-ray powder diffraction and scanning electron microscopy. The disclosed method of synthesis is promising for the preparation of NASICON as both bulk materials and thin layer coatings.

Octa(2,6-difluorophenyl)tetraazaporphyrinate magnesium(II) has been treated with 96% sulfuric acid to obtain octa(2,6-difluorophenyl)tetraazaporphyrin. Coordination reactions of octa(2,6-difluorophenyl)tetraazaporphyrin and metal exchange of its magnesium complex with copper and nickel salts in dimethylformamide have been studied. Cu(II) and Ni(II) complexes with octa(2,6-difluorophenyl)tetraazaporphyrin have been synthesized. The resulting compounds have been identified by electron absorption, IR and 1H NMR spectroscopy, and mass spectrometry. The structures of the synthesized compounds were optimized by the DFT method. The fluorescence quantum yields of the studied compounds have been determined.

A complex of zinc(II) with 2-hydroxy-5-ethylphenylphosphonic acid (H3L) of the composition [Zn(H2L)2(Н2О)2][Zn(HL)(Н2О)]·H2O (I) was synthesized, the structure of which was established based on data of X-ray diffraction and elemental analysis, quantum chemical calculations, as well as IR and electron absorption spectroscopies. The stability constants of H3L acid complexes with zinc(II) perchlorate in water were determined by potentiometric titration. The cytotoxic properties of H3L acid and complex I were studied for the first time on HeLa cells (human cervical adenocarcinoma). The results on the accumulation of complex I in HeLa cells were obtained by laser confocal microscopy.

The optimal geometries of (CaO)n and (MgO)n clusters at n = 2–30 have been found and the enthalpies of formation of 1D, 2D, and 3D structures have been determined using quantum-chemical DFT calculations. The calculation demonstrates that the formation of linear chains of Ca and Mg oxides practically does not occur, while the formation of two-dimensional (tiled) and three-dimensional (cubic) structures proceeds with a large release of energy. The competing process of formation of molecular rods consisting of planar six-membered rings (MO)3 has been considered, and it has been shown to proceed not through the stage of preliminary formation of six-membered rings, but directly from monomer units.

The paper describes a method for the optimization of liquid complex fertilizer (LCF) formulations using phase diagrams of multicomponent water–salt systems. The chosen optimization criteria are the concentration of solution and the set of salts that provide the most concentrated fertilizer at the set ratio N : P2O5 : K2O. The opportunities of the method are shown for exemplary three- and four-component systems. The compositions of eutonic solutions and the ratios of nutrients calculated for them are given. Experimental data confirm the influence of the salt set and a solubilizer (urea) on the solution concentration. The number of optimal compositions becomes greater as the number of components in the system increases. Phase diagrams help to determine whether the liquid fertilizer composition belongs to the 15 homogeneous regions and thereby to guarantee its long-term storage stability.

Here, we present the results of DTA and XRD studies of phase equilibria in the 6Ag2Se + Ag8GeTe6 ↔ 6Ag2Te + Ag8GeSe6 reciprocal system (system A). A Т–х diagram of the Ag8GeSe6–Ag8GeTe6 boundary system, several inner polythermal sections, isothermal sections at 300 and 1000 K, and the liquidus surface projection were plotted. The Ag8GeSe6–Ag8GeTe6 system is a partially quasi-binary system; it features continuous substitutional solid solutions between Ag8GeTe6 and the high-temperature cubic Ag8GeSe6 phase (the δ phase). Once solid solutions are formed, the polymorphic transition temperature in Ag8GeSe6 decreases, thereby stabilizing the ion-conducting cubic phase in the range of ≥40 mol % Ag8GeTe6 compositions at room temperature and below it. System A is shown to be a reversible reciprocal system; its liquidus surface is comprised of three fields, which relate to the primary crystallization of the solid solutions between the high-temperature Ag2Se and Ag2Te (α phase) phases, IT-Ag2Te-base solid solutions (β phase), and the δ phase. The subsolidus portion of system A features complex interactions related to polymorphism in the terminal compounds and in phases based on them

We employed contact alloying in the range 1000–1860°С to study the reaction specifics between SiC and Al2O3−(t + m)ZrO2(Y2O3) oxide composition. Real-time experiments with photographic recording of the changing size and shape of the Al2O3−(t + m)ZrO2(Y2O3) sample on a SiC ceramic substrate showed that Al2O3−(t + m)ZrO2(Y2O3) compositions react with the silicon carbide substrate in the range 1720–1860°С to melt and penetrate into (impregnate) the substrate. X-ray powder diffraction patterns were measured for samples taken from the contact area of the oxide composition with SiC directly on the substrate and in a chipped-off <1-mm-deep near-surface layer. ZrС, Al2Y4O9, and Al3.21Si0.47 were formed in the contact area via redox reactions involving oxide melt, in addition to 6H-SiC, Si and Al2O3, t-ZrO2 phases, which are the initial components of the substrate and oxide composition, respectively.

Cerium oxide sols functionalized with gallic acid (GA) in various molar ratios (CeO2@GA, 1 : 1, 1 : 2, and 2 : 1) were synthesized for the first time. The antioxidant activity of the obtained nanomaterials towards alkylperoxyl radicals was analyzed by the luminol-enhanced chemiluminescence assay. It was shown that CeO2@GA composites possess different types of redox activity, combining antioxidant and pro-oxidant properties. It was found that the redox activity of CeO2@GA composites is largely due to the ligand, gallic acid. Meanwhile, the immobilization of gallic acid on the surface of cerium dioxide nanoparticles leads to a decrease in its antioxidant and pro-oxidant activities. This effect is most pronounced in the case of the 2 : 1 CeO2@GA sol, in which the antioxidant and pro-oxidant capacities of gallic acid have decreased by 40 ± 3 and 58 ± 9%, respectively.