Editor’s column

A.V. Blinov, E.D. Nazaretova, Z.A. Rekhman, M.A. Pirogov, A.V. Samovolov, D.B. Golik
North-Caucasian Federal University

Abstract: Within the framework of this work, the optimization of synthesis and study of dispersive characteristics of selenium nanoparticles stabilized by octadecyltrimethylammonium bromide was carried out, and the study of the aggregate stability of the obtained nanoparticles from the active acidity of the pH of the medium was carried out. At the first stage, quantum-chemical modeling of the interaction process of selenium nanoparticles stabilized by octadecyltrimethylammonium bromide was carried out, which resulted in the establishment that the addition of octadecyltrimethylammonium bromide forms an energetically favorable and chemically stable interaction. The interaction of OTAB with selenium occurs through the quaternary amino group and is energetically favorable (ΔE > 2399 kcal/mol) and chemically stable (0,031 ≤ η ≤ 0,057 eV). The synthesis was carried out using a chemical reduction method in an aqueous environment. Solution of selenous acid and octadecyltrimethylammonium bromide was prepared at a constant temperature and stirred, and a separate solution of the reducing agent, selenous acid, was added to the precursor solution with a stabilizer. The synthesis was optimized using an experimental design matrix with varying
concentrations of system parameters. The samples were studied using photon correlation spectroscopy and acoustic electron spectroscopy. As a result of the research, it was found that the optimal sample has an average hydrodynamic diameter of 36 nm and a ζ-potential value of 46 mV. Then, the coagulation stability of selenium nanoparticles stabilized by octadecyltrimethylammonium bromide was studied in relation to changes in the pH of the medium. To conduct the study, buffer solutions with pH values ranging from 1,81 to 11,98 were prepared. The obtained samples of selenium nanoparticles stabilized by octadecyltrimethylammonium bromide were mixed with buffer solutions in a 1:1 ratio. As a result of the studies of the obtained samples, it was found that the change in the active acidity of the pH of the medium does not have a significant effect on the values of the average hydrodynamic diameter and ζ-potential of the samples at any point in the selected pH range of the medium.
Keywords: selenium nanoparticles, octadecyltrimethylammonium bromide, acoustic electron spectroscopy, photonic correlation spectroscopy, synthesis optimization

D.P. Bernatsky, V.G. Pavlov
Ioffe Institute

Abstract: The formation of clusters of potassium and cesium atoms on the surface of tungsten and rhenium crystals has been studied. The study was carried out using field electron microscopy, field desorption microscopy, and time-of-flight mass analysis of ions desorbed by an electric field. To determine the masses, particles adsorbed on the sample surface were desorbed with a high-voltage pulse lasting several ns, and the ion flight time from the sample to the detector was measured. The experiments were carried out in an ultrahigh vacuum (p < 10-9 Torr). Alkali metal atoms were deposited on the surface of tungsten and rhenium field emitters from an external spray. As a result of the measurements, not only monatomic alkali metal ions were detected, but also cluster ions containing up to seven atoms. The number of ions of each mass depended on the electric field strength on the surface of the emitters. As the field strength increases, the number of monatomic ions increases slightly at first and then decreases. In the opposite way, the number of cluster ions depends on the field strength. As the field increases, the number of cluster ions initially decreases, then increases. When a certain value of the field strength is reached, the emission of both monatomic and cluster ions stops. The described patterns are probably related to the movement of the field desorption zone, and, accordingly, the cluster identification area along the surface of the tip-shaped sample. The number of desorbed cluster ions reflects the cluster distribution over the sample surface. At low field strengths, ions are desorbed only from the area near the tip apex. This area consists of a densely packed crystal plane and wide steps surrounding this plane. As the tension increases, the desorption zone expands and passes through the rounded area of the surface between the flat faces, and the number of cluster ions
decreases. Then, desorption begins from the lateral faces and steps, and the number of ion clusters being desorbed increases. Thus, it can be assumed that clusters are predominantly formed and located on a surface with steps of densely packed planes.
Keywords: adsorption, cesium, potassium, tungsten, rhenium, electric field, ions

A.R. El Zanin, S.V. Boroznin, N.P. Boroznina, I.V. Zaporotskova
Volgograd State University

Abstract: In this paper, an analysis of the current state of the domestic coal industry was carried out based on up-to-date statistical data, key challenges and risks associated with both global trends and factors of external economic pressure were described. As a possible measure to support the profitability of coal mining and ensure the socio-economic sustainability of the regions involved in this sphere, it is proposed to consider the production of carbon nanomaterials from coal. The rapidly growing market of carbon nanomaterials could provide an additional incentive for the development of knowledge-intensive and high-tech enterprises based on the coal industry. Various groups of methods allowing obtaining carbon nanomaterials from coal were considered, including ultrasonic liquid-phase exfoliation, hydro- and solvothermal synthesis, direct chemical synthesis, assuming no need for energy-consuming processes, mechanochemical activation, arc-discharge and plasmochemical methods, chemical vapor deposition. As part of the consideration of each of the approaches, a detailed description is given of the techniques that make it possible to obtain a wide variety of carbon nanomaterials: carbon quantum dots, graphene, carbon nanotubes, fullerenes. In conclusion, based on the information provided by the review, the most economically feasible production strategies are identified both in the short and long term.
Keywords: coal, carbon dots, graphene, carbon nanotubes, fullerenes, synthesis methods

Z.V. Shomakhov¹, S.S. Nalimova², V.A. Moshnikov^2
1 Kabardino-Balkarian State University named after H.M. Berbekov
² Saint Petersburg Electrotechnical University «LETI»

Abstract: Plasmonic nanostructures based on metal oxides modified with noble metal nanoparticles have been attracting increasing attention among researchers working in fields such as photodynamic therapy, biosensors, photonics, optoelectronics, surface-enhanced Raman spectroscopy, and catalysis. The characteristics of these nanocomposites depend on the size of nanoparticles and are determined by the methods and conditions used for their synthesis. In this paper, approaches to the synthesis of «plasmonic nanoparticles – metal oxide» nanocomposites – are analyzed. Methods for producing metal nanoparticles on the surface of pre-synthesized metal oxides are considered, including various methods of precipitation from the gas and solution phases. A group of methods for the single-stage synthesis of nanocomposites is identified, which includes variations of the sol-gel method and others. The particle size, particle size distribution, and uniformity of the arrangement of metal nanoparticles in the formed nanocomposites are analyzed. The possibilities of controlling the interaction of components in nanocomposites are shown by using diffuse reflection spectroscopy by the appearance of absorption bands corresponding to plasmon effects. The interaction of components leads to a decrease in the band gap of composite materials. Additional diagnostic methods are Raman spectroscopy and X-ray photoelectron spectroscopy, which analyze changes in the position of characteristic peaks, as well as the Kelvin probe method in scanning probe microscopy.
Keywords: plasmonic nanoparticles, metal oxide, nanocomposites, synthesis, optical spectroscopy

V.M. Skachkov¹, K.I. Sabanin², I.S. Medyankina¹, E.A. Bogdanova³, N.A. Sabirzyanov^1
1 Institute of Solid State Chemistry of the Ural Branch of RAS
² Ural Federal University named after the first President of Russia B. N. Yeltsin
³ JSC «Giredmet»

Abstract: The article discusses a technologically simple method for the autoclave production of ultrafine hydroxyapatite, suitable for the manufacture of pharmaceutical compositions, medicines and preparations. A thermodynamic assessment of the possibility of the reaction depending on the ratio of the initial components and technological modes was carried out. The temperature range, the feed rate of the phosphoric acid solution, the optimal concentrations of the initial components, their stoichiometric ratio, which ensures a high yield of the final product and its degree of purity, have been experimentally established. The synthesis products are certified using state-of-the-art physico-chemical analysis methods. The composition of the final product was monitored by X-ray phase analysis, differential thermal analysis, the surface morphology of the synthesized products was evaluated by scanning electron microscopy, and the surface characteristics by the Brunauer-Emmett-Teller method. A patent has been obtained for a simple technological method developed as a result of the work for the production of amorphous hydroxyapatite with a high degree of purity.
Keywords: hydroxyapatite, synthesis, autoclave, technological parameters, biomaterials

Z.A. Akhmatov^1,2, F.Kh. Khokonov^2,3, I.N. Sergeev^2
1 Kabardino-Balkarian State University named after H.M. Berbekov
² Institute for Nuclear Research of the RAS
³ Kabardino-Balkar Scientific Center of the RAS

Abstract: Graphite intercalated compounds have attracted significant attention from researchers due to their unique physical properties. Metals and molecules introduced into the interplanar spacing of graphite can act as donors or acceptors of electrons. This means that intercalation with different chemical elements can influence the carrier concentration in graphite. As a result, graphite intercalated compounds can exhibit different electronic, thermal and magnetic properties. In this work, the possibility of modifying the electrophysical properties of highly oriented pyrolytic graphite by intercalating it with potassium atoms is demonstrated. Intercalation of highly oriented pyrolytic graphite by potassium was performed using a two-zone method. The intercalation stage of the sample was determined from Raman spectra data. Measurements of the electrophysical properties of pure and intercalated graphite were carried out using the van der Pauw method (four-probe method). It has been shown that intercalation of highly oriented pyrolytic graphite by potassium leads to a decrease in its specific resistance and Hall constant, while there is a significant increase in the concentration and mobility of charge carriers. Considering that the change in the electrophysical properties of graphite during its intercalation occurs without the destruction of the crystalline structure, which leads to a deterioration in the physical characteristics, it can be said with confidence that this method is one of the most promising in modifying electronic, surface, and other properties of layered carbon materials.
Keywords: Highly oriented pyrolytic graphite, electrophysical properties, Hall constant, alkali metals, intercalation, two-zone method, Raman spectroscopy

K.V. Suliz, A.V. Pustovalov, A.V. Pervikov
Institute of Strength Physics and Materials Science of Siberian Branch of RAS

Abstract: Nanoparticle samples of (NiCoCrFeAl)_xO_y with 18, 30, and 35 at.% Al were synthesized via the joint electrical explosion of wires in an Ar + 25 mol.% O₂. It has been established that spherical nanoparticles with a predominantly spinel-type crystal structure are formed during the joint electrical explosion of wires containing the specified metals in concentrations ranging from 5 to 35 at.%. The lattice parameter of the spinel phase decreases from 8,251 to 8,182 Å as the aluminum content increases from 18 to 35 at.%. Energy-dispersive spectroscopy data confirm a homogeneous distribution of metals within the nanoparticles. It is shown that it is necessary to take into account not only the ratio of metals in the explosion products, but also the thermodynamic conditions for the formation of nanoparticles. These conditions are determined by the pressure and thermal conductivity of the buffer gas used to obtain (NiCoCrFeAl)_xO_y nanoparticles with a given crystalline structure using the method of joint electrical explosion of wires.
Keywords: multicomponent oxide, nanoparticles, exploding wires, transmission electron microscopy, energy dispersive analysis, X-ray phase analysis

L.S. Elbakyan, I.V. Zaporotskova
Volgograd State University

Abstract: An analysis of the influence of boron impurities on the adsorption activity of boron-modified carbon nanotubes with respect to methyl methacrylate have been done. Research on the adsorption of methyl methacrylate can contribute to understanding mechanisms of sorption and help in the development of new functional materials. To complete the picture, the effect of boron concentration (from ~16% to 50%) on the final properties of the composite has been studied in the framework of the study. To predict the possibility of creating a stable «polymer-nanotube» complex, a theoretical study was performed using the quantum chemical density functional theory. The results were compared with the previously obtained results of a study of pure carbon nanotubes with a structural unit of methyl methacrylate. It has been found that polymethyl methacrylate molecules were adsorbed on the surface of nanotubes with significantly higher energy (~45-50%) than on pure nanotubes. The results of calculations of the electronic structure and electrostatic potentials have shown that a significant redistribution of the electron density occurs during the interaction between borocarbon nanotube and the methyl methacrylate monomer. This is expressed in an increase in the positive charge on the boron atom and an increase in the negative charge on the carbonyl oxygen of the monomer, which indicates the emergence of a strong donor-acceptor and Coulomb attraction between them. As a result, the structure of a borocarbon nanotube complex with methyl methacrylate was modeled. Its stability is ensured by physical adsorption, accompanied by a significant Coulomb contribution. Thus, borocarbon nanotubes, being p-type semiconductors, can provide better control over the electrical conductivity of the composite and create new ways for use in flexible electronics and sensors. It is also possible to expect a significant increase in the tensile strength, modulus of elasticity and impact strength of the composite with the same degree of filling due to the effective load transfer from the polymer matrix to the reinforcing bunts.
Keywords: polymethyl methacrylate, borocarbon nanotubes, polymer nanocomposites, density functional theory, adsorption interaction, electrostatic potential

A.V. Shergin¹, P.K. Shidlovskaya¹, E.A. Belaya¹, V.V. Fadeev^2
1 Chelyabinsk State University
² South Ural State University (National Research University)

Abstract: This paper presents an ion-exchange method for synthesizing yttrium aluminum garnet powders using a synthesized cation-exchange material based on sulfonated polystyrene. This material was obtained by heterogeneous sulfonation of polystyrene using concentrated sulfuric acid. Optimum synthesis conditions were determined, namely: the amount of the required cation-exchange material, the holding time in a solution containing Y³⁺ and Al³⁺ cations, and heat treatment conditions. It was found that compliance with these conditions allows obtaining single-phase products with the maximum yield. When deviating from the optimal conditions, the final product is contaminated with residues of the organic matrix and the intermediate product Y₄Al₂O₉. The phase composition of the obtained samples was determined by powder X-ray diffraction methods; it corresponds to the garnet structure with the Ia3d space symmetry group. The paper presents studies of the particle surface morphology and determines the particle sizes of the powder using scanning electron microscopy. The samples are flake-shaped nanoparticles, the particle size varies from 30 to 100 nm, partially aggregated into clusters of sizes from 1 to 10 μm.
Keywords: ion exchange synthesis, yttrium aluminum garnet, optical materials, nanopowders, cation exchange material, organic matrix, sulfonated polystyrene

D.D. Filippov, A.A. Nagdalyan, A.V. Blinov, Z.A. Rekhman, A.B. Golik, M.A. Pirogov, D.B. Golik
North Caucasus Federal University

Abstract: In this work, samples of cobalt (II, III) oxide nanoparticles stabilized with alkyldimethylbenzylammonium chloride were obtained by chemical precipitation in an aqueous medium. This material has a wide range of applications in electronics, agriculture, and medicine due to its magnetic, antibacterial, and conductive properties. Investigations were carried out using X-ray phase analysis, scanning electron microscopy, and infrared spectroscopy as well as quantum chemical modeling of the interaction of alkyldimethylbenzylammonium chloride and cobalt (II, III) oxide nanoparticles. During the study of the phase composition, it was found that the resulting sample has a cubic crystal lattice with a spatial face-centered group. Based on analysis of the microstructure, it was found that the sample was formed from irregularly shaped agglomerates ranging in size from 8 to 47 microns, consisting of spherical nanoparticles with a diameter from 50 to 75 nm. As a result of computer quantum chemical modeling, it was found that the interaction of cobalt (II, III) oxide nanoparticles with alkyldimethylbenzylammonium chloride is energetically favorable and chemically stable and occurs through nitrogen cation, which is confirmed by the results of infrared spectroscopy. Analysis of the obtained spectra showed that the interaction of cobalt (II, III) oxide with alkyldimethylbenzylammonium chloride occurs in the range of 1522-1630 cm^-1 through the ionized amino group NH₂⁺.
Keywords: nanoparticles, cobalt (II, III) oxide, alkyldimethylbenzylammonium chloride, stabilization, computer quantum chemical modeling