Том 68, № 7 (2023)

CeO2 nanooxide has been synthesized from cerium(III) nitrate using powdered cellulose (PC) and its mixture with sucrose as templates. The removal of templates from composites (PC–Ce(NO3)3 and PC–sucrose–Ce(NO3)3) has been carried out in two ways: via direct burning-out of PC (PC–sucrose) in an air flow and via burning-out of the carbonizate after template pyrolysis. Using UV and IR spectroscopy, X-ray powder diffraction (XRD), and electron microscopy, the influence of the template composition and the method of its removal on the physicochemical characteristics of CeO2 nanoparticles has been studied. A carbon–oxide material CeO2/C has been synthesized by pyrolysis of PC–Ce(NO3)3 and PC–sucrose–Ce(NO3)3 composites. It has been established that the pyrolysis of PC–Ce(NO3)3 and PC–sucrose–Ce(NO3)3 leads to the formation, in the carbonizate, of CeO2 (cerianite) nanoparticles with sizes of 3–4 and 1–2.5 nm, respectively. The average diameter of nanoparticles (according to XRD data) is 3.8 and 2.3 nm. CeO2/C synthesized from the PC–sucrose–Ce(NO3)3 composite contains cerium(III) oxide. All CeO2 nanoparticles in the carbon matrix have a hydroxyl–hydrate cover. The burning of the organic or carbon matrix of the composites leads, regardless of the template used and synthesis conditions, to the formation of CeO2 (cerianite) nanoparticles with the same average diameter of 25 ± 1 nm (according to XRD data), containing an admixture of the Ce(III) phase and having a hydroxyl–hydrate cover. Carbon is present in the material in trace amounts (≤0.15 wt %). The size scatter of CeO2 nanoparticles produced by burning out PC from the PC–Ce(NO3)3 composite is 15–30 nm. In those cases when the organic component from PC–sucrose–Ce(NO3)3 is subjected to burning or the pyrolysis stage of both composites is included in the synthesis process, the appearance of a fraction of larger CeO2 particles (50–60 nm) is observed. The correctness of the obtained data has been confirmed in the course of the model process of hydrogen peroxide decomposition.

Au, Fe, and AuFe nanoparticles were obtained by metal vapor synthesis using acetone as the dispersion medium. The composition and electronic structure of the particles were studied by TEM, SEM, XPS, XANES, and EXAFS. The Au and Fe particles with average diameters of 5.3 and 1.8 nm, respectively, were obtained. According to X-ray diagnostic methods, gold was in the main Au0 state, and the Au+ and Au3+ states are present in small amounts while iron existed as mixture of non-stoichiometric oxides with states close to Fe2+ and Fe3+. Bimetallic nanoparticles were solid solutions with a disordered structure and Au–Fe–O and Au–O–Fe bonds. A carbon-containing shell was detected for all types of metal particles. The obtained materials may be promising for the development of improved antimicrobial agents and new methods for treating cancer diseases.

X-ray powder diffraction, X-ray photoelectron, and Mössbauer spectroscopy are used to study the ionic and phase compositions of samples of powdered ferrogarnet Y2.5Ce0.5Fe2.5Ga2.5O12 obtained by gel combustion followed by crystallization in vacuum and additional annealing in air at 750°С. According to X-ray photoelectron and Mössbauer spectroscopy data, the iron and cerium cations in the homogeneous ferrogarnet structure are stabilized in the formal oxidation state Fe3+. At the same time, along with Ce3+, the surface of Y2.5Ce0.5Fe2.5Ga2.5O12 particles contains Ce4+ ions. The results obtained can be used to create functional materials for a new generation of magnetooptical devices.

Coordination compounds [Zn(H2O)4(Ur)2](NO3)2, [M(H2O)2(Ur)2(NO3)3] (M = Ce, Nd), and [Dy(H2O)(Ur)2(NO3)3] have been synthesized by the reaction of nitrates of zinc or rare earth elements with urea (Ur) in an aqueous solution. Their composition has been determined and structural features have been established using elemental analysis, IR spectroscopy, and X-ray diffraction analysis. For the zinc complex, a polymorphic transition has been found at 181 K.

A method for the synthesis of Fe(III)-based zeolite imidazolate framework at various metal to linker ratios was proposed. The resulting material was used as an adsorbent for zinc(II) and copper(II) ions. It was shown that the materials were composed of hexagonal particles and represented a microheterogeneous system with an average particle size of 0.05–0.1 μm. The isotherms of nitrogen adsorption in the pores of Fe-ZIF were measured. By processing of the isotherms, porous structure parameters for the samples were found. The adsorption of Cu2+ and Zn2+ ions from aqueous solutions at 298.15 K was studied and high degrees of metal extraction was demonstrated. The adsorption of copper and zinc ions was spontaneous in all cases. The highest coverages of the surface active sites were 0.96 and 0.71 for copper and zinc, respectively. The adsorption in the bulk of energetically homogeneous porous adsorbent and predominance of micropores in iron(III) 2-ethylimidazolate structure were established.

The formation of spin levels upon torsional deformation of nonchiral (n, n) carbon nanotubes has been theoretically studied. In the absence of mechanical deformation, nanotubes have inversion symmetry and a metallic band structure with a spin-degenerate state near the Fermi level. The twisting deformation breaks the inversion symmetry, so that the tube becomes chiral. As a result, due to the Rashba effect, the degeneracy of the levels is completely lifted and spin gaps are formed between the bands of predominantly α and β types.

The phase assemblage of the Li+,Na+,K+||F–,Cl–,Br– five-component reciprocal system was studied for the first time. The phase tree obtained by partition of the phase assemblage into stable elements is linear. It consists of the following stable elements: the LiF–NaF–KF–KBr–KCl pentatope, LiF–NaBr–NaCl–KCl–KBr–NaF hexatope, and NaCl–KCl–KBr–LiBr–LiCl–LiF–NaBr heptatope, linked by the LiF–NaF–KCl–KBr stable tetrahedron and the LiF–KBr–NaBr–NaCl–KCl square pyramid (pentatope). Phase equilibria in the LiF–KCl–KBr–NaBr–NaCl stable pentatope were studied by differential thermal analysis (DTA). Monovariant phase equilibrium L ⇄ LiF + NaClxBr1 – x + KClyBr1 – y occurs in the pentatope, where NaClxBr1 – x and KClyBr1 – y are continuous solid solutions (css) between NaCl and NaBr, KCl and KBr salt pairs, respectively. The composition of the mixture at point Min◻ 591 and the lowest monovariant equilibrium temperature were determined. A 3D computer model was designed as a projection of the phase assemblage on the LiF–KCl–KBr–NaBr–NaCl pentatope in KOMPAS-3D software. The volumes of crystallizing equilibrium phases were outlined.

Extended Debye–Hückel (EDH) theory was used to calculate activity coefficients in aqueous solutions of alkali-metal bromides at 298 K from experimentally determined values of their static permittivities. Calculations with non-optimized model parameters fit the nonmonotonic concentration-dependent trend of the activity coefficients and the cation radius–dependent trend of the activity coefficients. The latter is explained by hydration weakening and ion association strengthening in response to increasing cation radius in the salt series.

We have studied the preparation of magnetic graphitic carbon composites, which combine the adsorption properties of activated carbon with magnetic properties and properties intrinsic to graphite. The preparation method is efficient; it comprises modifying flax shive cellulose with citric acid to enhance the chelating ability of the flax shive cellulose matrix, impregnating the modified cellulose with iron chloride, and pyrolysis in an inert atmosphere to control the composition, morphology, specific surface, and porosity of hybrid carbon materials. The scenario of cellulose matrix pyrolysis was suggested using thermogravimetry. X-ray structural analysis was used to characterize the graphitic composites. The citric acid modification of cellulose helps to prepare a high-graphite (74%) carbon composite where the graphitization level of the graphite structure approaches the graphitization level of commercially available graphite at 700°С. Low-temperature N2 adsorption–desorption and ζ-potential measurements helped to suggest the adsorption mechanism for environmentally hazardous dyes. The greatest equilibrium adsorption of Methylene Blue (MB) and Methyl Orange (MO) dyes was 127.4 and 23.7 mg/g, respectively. The prepared composites can be used as adsorbents and fillers in polymer composite materials.

Aluminum anodizing in electrolytes comprising mixtures of several acids opens way to manufacture porous films of anodic aluminum oxide (AAO) with a widely tunable structure period. Study of thermal transformations in AAO films produced in mixed electrolytes is a separate task, as a complex chemical composition of the material can give rise to some specifics in subsequent annealing. Impurity oxalate and sulfate ions were detected in the AAO produced by aluminum anodizing in sulfuric acid/oxalic acid mixed electrolytes. The sulfate weight fraction appears about one order of magnitude higher than the oxalate weight fraction, and it increases as the concentration ratio of sulfuric acid to oxalic acid in the electrolyte increases. In the same way, the crystallization temperature of amorphous AAO to a mixture of low-temperature Al2O3 polymorphs increases in response to increasing concentration ratio of sulfuric acid and oxalic acid. Thus, the component ratio in the mixed electrolyte used influences the composition and thermal transformations of AAO.