Vol 69, No 2 (2024)

The formation of electric charges during the synthesis of complex oxide materials based on strontium hexaferrite SrFe₁₂O₁₉, including doped with lanthanum and cobalt ions, via the combustion of nitrate-organic precursors has been established. Precursors included polyvinyl alcohol or glycine as organic component. The intensity of charge generation was lower for precursors containing a larger amount of organic component. Data on the magnetic characteristics of the samples were obtained: magnetization, coercive force. The influence of an external magnetic field during the synthesis of hexaferrites significantly affected the coercive force of the samples and allowed to increase its values due to the formation of extended ensembles of nanoparticles. At the same time, such an effect on samples with a relatively low level of charge generation during precursor combustion was more effective. The relationship between the factors influencing the formation of extended aggregates is analyzed. The Sr_0.8La_0.2Fe_11.8Co_0.2O₁₉ samples had the maximum coercive force. One of the techniques for increasing the coercive force is a two-stage thermomagnetic treatment, including a low-temperature stage. The formation of branched extended structures at the macro- and micro-levels was found during the combustion of glycine-containing precursors.

Zinc sulfide doped with Mn²⁺ ions was synthesized in a homogeneous dodecane medium by the method of emerging reagents. By methods of chemical and X-ray phase analysis, IR spectroscopy, electron microprobe microscopy, identification of products was carried out, photographs of the surface of powder particles (SEM) were recorded. Based on the totality of the results, a conclusion is made about the formation of nanoscale objects having a polytype structure with a predominance of distorted cubic crystals forming agglomerates up to 10 microns in size in ZnS powder and up to 100 microns in ZnS–Mn powder. The formation of nanoscale ZnS particles is confirmed by spectral data. The effect of manganese ions on the photoluminescence (FL) of the powder is manifested by a change in the type of the descending branch of the ZnS–Mn FL band, it is associated with recombination processes at the levels of defects formed by Mn²⁺ ions in the ZnS structure at their low concentration.

Solid solutions of pyridinium bromo-iodobismutates were isolated from aqueous solutions and structurally characterized. The composition of the resulting solid solutions [HPy]BiX₄ and [HPy]₃Bi₂X₉ (X = Br, I) was found to depend on the ratios of pyridinium/bismuth and bromine/iodine in the initial solution. The existence of five polymorphic modifications in the system for [HPy]BiX₄ compounds was shown. Two different polymorphs were found for iodobismuthate [HPy]BiI₄.

Zn(II) complexes of the composition [ZnLⁿ₂X₂] and [ZnLⁿ₃(NO₃)₂] were synthesized, where n = 1, 2; X=Cl, Br, I; L¹=2-aminothiadiazole-1,3,4, L²=2-amino-5-methylthiadiazole-1,3,4. The obtained complexes were studied by elemental analysis methods, IR and 1H NMR spectroscopy. The structure of the [ZnL²₂Br₂] complex was determined by the RSA method (CIF file CCDC No. 2251742). The ligand molecules of 2-amino-5-R-thiadiazoles-1,3,4 (R = –H, –CH₃) are coordinated monodentately by an endocyclic nitrogen atom located in the α-position to the amino group. The polyhedron of the central atom of halide complexes is a slightly distorted tetrahedron, in the coordination sphere of which two halide atoms and two endocyclic nitrogen atoms are located. During complexation in the spectrum of the solution of the [ZnL²₂Br₂] complex, coordinated L² ligands undergo amino-imine tautomerization into a heterocyclic amine with a nitrogen atom in a heterocycle. The polyhedron of the central atom for nitrate complexes is a slightly distorted trigonal bipyramide, in the coordination sphere of which three nitrogen atoms of ligands are located in the equatorial plane and two oxygen atoms of two nitrate anions in the axial position.

The possibility of using the method of energy-dispersive X-ray spectroscopy for quantitative assessment of the chemical composition of igneous rocks without their transfer into solution is considered. Statistical processing of the measurement results was carried out and the error of the method in comparison with the inductively coupled plasma spectrometry method was shown.

The interaction in double and ternary systems containing Fe³⁺ ions and biologically active substances – succinic acid and/or one of the amino acids (glycine, glutamic acid, aspartic acid) has been studied by spectrophotometry, photometry, pH-metry and solubility techniques. The composition and stability constants of homo- and mixed-ligand complexes were determined at ionic strength I = 0.3; iron(III) succinate with the composition of Fe₂Suc₃ ∙ 3H₂O was isolated, its solubility constant was determined according to solubility data, lgK_S = –27.74 ± 0.12. The redox process in the iron(III)–succinate-anion system was noted over time.

Samples of sodium aluminosilicates obtained by hydrolytic deposition using rice straw of different varieties as silicon-containing raw materials were studied. The morphology of the particles was determined by scanning electron microscopy, the specific surface area (362–470 m²/g) was measured, IR spectra were recorded, and the chemical and phase composition of the samples was determined. The sorption properties of the obtained materials with respect to lead ions have been studied, the sorption capacity is 199–550 mg/g. An organic component was found and isolated in the samples, which is formed as a result of the deposition of aluminosilicates from rice straw hydrolysates, its composition was determined by thermogravimetry and IR spectroscopy. The effect of the organic component on the sorption capacity of plant-derived aluminosilicates has been investigated. The proposed sorption mechanism has been established. The approach used makes it possible to obtain aluminosilicates with a high sorption capacity, as well as safely dispose of rice straw.

Ferrites of non-ferrous metals are promising magnetic catalysts that can be easily separated from the reaction mixture after use by applying a magnetic field. However, these materials have a fast electron-hole relaxation time, which reduces their activity in photoreactions. This problem is overcome by creating hybrid nanostructures based on ferrites, for example with zinc oxides. The catalytic activity of such structures depends highly on the method of their synthesis. In this work, the alkaline co-precipitation of Fe²⁺ and Ni²⁺ ions, which have similar values for hydroxides, was used to obtain stoichiometric and homogeneous nickel ferrite precursors. The influence of the reaction parameters on the purity of the nickel ferrite phase and the size of the particles was studied using the experimental design technique. Spherical nanoparticles 15.9 ± 1.1 nm in diameter were produced under the optimal conditions identified. Based on the obtained material, NiFe₂O₄/ZnO magnetic composites of different quantitative compositions were prepared. The photocatalytic activity of the hybrid structures was demonstrated by photodegradation of crystal violet dye.