Objectives. The creation of ion-selective electrodes (ISEs) based on rare-earth element (REE) complexes in environmentally friendly biosystems is of interest due to the increased relevance of environmental management. The work sets out to study the possibility of using REE complexes for creating ISEs sensitive to cefazolin. The created potentiometric sensors can be used for rapid determination of antibiotics in microvolume samples. Methods. The work presents the synthesis of electrode-active REE complexes with cefazolin. In order to identify the obtained electrodeactive substances and investigate their physicochemical characteristics, the following methods were used: elemental analysis with a scanning electron microscope, infrared spectroscopy, simultaneous thermal analysis, and potentiometry. Results. Previously unstudied complexes of cerium and lutetium with cefazolin were obtained for use as an electrode-active substance for creating ISEs. The physicochemical characteristics of the complexes were investigated. For the created ISEs, the following characteristics were studied: performance characteristics, the dependence of electrode potentials on the analyte concentration, stability, and the response time of the electrode placed in the sample under study. The created membrane electrodes are stable, have a concentration range of operation of pC 1–3, and can be used in the pH range 4–8. Testing of the selectivity of the ISEs with respect to Na+ and K+ ions showed that the electrodes are effective even in a thousandfold excess. The performance of the electrodes was tested using model systems. Conclusions. Novel REE–cefazolin complexes were successfully demonstrated for use as electrode-active substances for the manufacture of membrane ISEs sensitive to cephalosporin antibiotics.

The self-assembly and gelation processes in low-concentrated aqueous solutions of L-cysteine and silver nitrate (cysteine–silver solution, CSS); low-molecular-weight water-soluble chitosan (CS); and a gelation initiator, CuSO4, have been studied by various physicochemical methods, namely, UV spectroscopy, dynamic light scattering, pH-metry, viscometry, and scanning electron microscopy. It has been found that the gelation of CSS, which is used as a gel precursor, under the action of chitosan (CS) and copper sulfate occurs in a narrow concentration range: CCH = 0.0100–0.0150 mg/mL, C_CuSO_4 = 0.4–0.6 mМ, CL-cys = 3.00 mМ, and C_AgNO_3 = 3.75 mM, when Ag+/Cys molar ratio is 1.27. Hydrogels of various CSS–CS and CSS–CS–CuSO4 compositions possess no high mechanical strength; however, they are stable in the course time. The structural elements of CSS, i.e., cluster chains of silver merchaptide (SM) zwitterions, are positively charged; therefore, no polyelectrolyte complexation occurs in CSS–CS and CSS–CS–CuSO4 hydrogels, because the pH of CSS is 2.6. Addition of CuSO4 to CSS–CS samples promotes the formation of a more strong hydrogel due to the association of SM clusters and CS molecules with sulfate anions and the coordination of Cu(II) ions with deprotonated carboxyl groups of different clusters.

In this paper, a study of a graphite intercalation compound by potassium was carried out using Raman spectroscopy. The purpose of the study was to determine the intercalation stage and study the influence of intercalated atoms on the vibrational properties of highly oriented pyrolytic graphite lattice. The intercalation of highly oriented pyrolytic graphite by potassium was performed using a two-zone method. Raman spectra were obtained for both pure and intercalated highly oriented pyrolytic graphite. The experiments carried out to identify the synthesized structures showed the formation of sixth stage graphite intercalation compound. Knowledge of the stage of the intercalated graphite compounds is important for its use as a superconducting material, as well as in supercapacitors. In addition, the intercalation stage is a key factor in obtaining graphene by chemical exfoliation of graphite intercalation compound, since the number of graphene layers will directly depend on the intercalation stage. In the obtained Raman spectra, the effect of G-peak splitting is observed, indicating a change in the vibrational properties of the graphite lattice during its intercalation due to the charge transfer from the intercalate to the carbon layers. The value of the transferred charge is determined using first-principles calculations.

The values of microhardness of specimens of paratellurite single crystals differing from each other in growth conditions and structural quality were measured. For the (110) plane, these values lie in the range 300–470 kg/mm2. It was determined that mechanical stresses in paratellurite can lead to significant deviations of microhardness values from average values.

This article presents the results of studying non-conducting biological, crystalline objects, powders, and glass composite samples using an ionic liquid by scanning electron microscopy. Ionic liquids based on alkylpyridinium dicyanamides studied in the work were obtained by a metathesis reaction. A solution of ionic liquid in acetone was used as a conductive coating for dielectrics. It was found that the use of ionic liquid is an alternative to the methods of metal and carbon sputtering on dielectric samples. Scanning electron microscopy images of samples obtained by such microscopy methods as low vacuum mode, the use of metal sputtering (Pt) on samples, and a study of samples without a conductive coating are presented. A comparative analysis of the results obtained by traditional methods and the method of applying ionic liquid to samples is carried out. It is shown that the use of electrically conductive ionic liquids with the thermal and chemical stability makes it possible to obtain high-resolution electron microscopic images and also allows visualization of the topographic and compositional contrast of the studied dielectric samples.

Supramolecular hydrogels based on low-molecular-weight compounds are a unique class of so-called “soft” materials, formed by weak non-covalent interactions between precursors at their millimolar concentrations. Due to the variety of structures that can be formed using different low-molecular-weight gelators, they are widely used in various fields of technology and medicine. In this study, we report for the first time an unusual self-assembly process of mixing a hydrosol obtained from L-cysteine and silver nitrate (cysteine–silver sol—CSS) with sodium halides. Modern instrumental techniques such as viscosimetry, UV spectroscopy, dynamic light scattering, zeta potential measurements, SEM and EDS identified that adding fluoride anions to CSS is able to form stable hydrogels of a thixotropic nature, while Cl−, Br− and I− lead to precipitation. The self-assembly process proceeds using a narrow concentration range of F−. An increase in the fluoride anion content in the system leads to a change in the gel network morphology from elongated structures to spherical ones. This fact is reflected in a decrease in the gel viscosity and a number of gel–sol–gel transition cycles. The mechanism of F−’s interaction with hydrosol includes the condensation of anions on the positive surface of the CSS nanoparticles, their binding via electrostatic forces and the formation of a resulting gel carcass. In vitro analysis showed that the hydrogels suppressed human squamous carcinoma cells at a micromolar sample concentration. The obtained soft gels could have potential applications against cutaneous malignancy and as carriers for fluoride anion and other bioactive substance delivery.

Introduction of dopants is a classic method for modifying the properties of materials, in particular, complex oxides of the perovskite family with the general formula ABO3. Ions located in positions A and/or B are substituted. In this case, their valence can coincide with the valence of the basic ion (isovalent substitution) or differ (heterovalent substitution). Sodium niobate (NaNbO3) is a convenient basis for producing ferroelectric solid solutions. Doping changes the properties of sodium niobate in a wide range, allowing the production of functional materials for various applications. In this paper, the effect of Bi3+ doping upon substitution of niobium ion Nb5+ on the structure and electrophysical properties of sodium niobate is studied. It has been shown that such compositions are characterized by a significant increase in electrical conductivity with increasing the doping concentration, a decrease in the Curie temperature, and a change in the grain structure. The dopant concentration is more than 10 mol. % leads to the formation of some secondary phases.

DOI: 10.26456/pcascnn/2024.16.219 Abstract: In our work, we used the finely dispersed polystyrene to produce porous samples of the piezoelectric ceramics. Samples of the sodium potassium niobate ceramics with pore concentrations of the 10, 20, 25, 30 and 40 volume percent were produced. The structure was analyzed and the temperature and frequency dependences of the dielectric constant of the obtained samples were investigated. It has been established that the presence of polystyrene in the process of sintering piezoceramic samples plays the role of a binder, which evaporates during high-temperature processing. At the same time, the binder contributes to stabilization of the dielectric properties of the ceramics. In the porous samples, there are no fluctuations of the permittivity in the low-frequency region, and the frequency range in which the permittivity values are independent of the frequency increases. It was found that already 34 volume percent of the pores worsen the mechanical strength of the sample. It is shown that the use of a simple problem of percolation theory does not allow assessing the mechanical strength of porous samples depending on the pore concentration.

The authors study magnetic properties of Heusler alloys with composition Ni54.4Mn17.6Ga26.2Si1.8 subjected to multiple isothermal forging. It is found that multiple isothermal forging shifts the temperatures of structural and magnetic phase transitions toward low values. Magnetization and the magnetocaloric effect are reduced slightly, and there is a qualitative change in the structure of the magnetic domain.

The article continues a series of studies of permanent magnets with different magnetization reversal mechanisms (nucleation, domain boundary displacement). In this work, a correlation is established between magnetic characteristics of permanent magnets (Y25 and AlNiCo) and the fractal dimension of magneto-optical images of their stray fields. Bismuth-containing ferrite-garnet films were used as an indicator. It is shown that the limiting values of the fractal dimension: 1,76 for a ferrite magnet and 1,85 for an AlNiCo magnet, are consistent with the results obtained for NdFeB (grade N35) and SmCo (grade KC37) magnets, as is the behavior of the field dependence of the fractal dimension. The behavior of the field dependence of magnetization Mmo(Hrev) has similar features to a similar dependence recorded for a permanent magnet NdFeB (grade N35), but the values of the demagnetizing fields for the Y25 sample are much smaller. The paper discusses the relationship between the mechanisms of magnetization reversal of permanent magnets and the behavior of the Mmo(Hrev) dependence.

In this study, a novel supramolecular composite, “photogels”, was synthesized by mixing of cysteine–silver sol (CSS) and methylene blue (MB). A complex of modern physico-chemical methods of analysis such as viscosimetry, UV spectroscopy, dynamic and electrophoretic light scattering, scanning electron microscopy and energy-dispersive X-ray spectroscopy showed that MB molecules are uniformly localized mainly in the space between fibers of the gel-network formed by CSS particles. Molecules of the dye also bind with the surface of CSS particles by non-covalent interactions. This fact is reflected in the appearance of a synergistic anticancer effect of gels against human squamous cell carcinoma even in the absence of light irradiation. A mild toxic influence of hydrogels was observed in normal keratinocyte cells. Photodynamic exposure significantly increased gel activity, and there remained a synergistic effect. The study of free-radical oxidation in cells has shown that gels are not only capable of generating reactive oxygen species, but also have other targets of action. Flow cytometric analysis allowed us to find out that obtained hydrogels caused cell cycle arrest both without irradiation and with light exposure. The obtained gels are of considerable interest both from the point of view of academics and applied science, for example, in the photodynamic therapy of superficial neoplasms.

Results are presented from optical profilometry and scanning probe microscopy studies of the structures and surface parameters of germanium single crystals exposed to an alternating magnetic field. A change in the relief and surface roughnesses of the crystals after magnetic field processing and a drop in their optical transmittance in the range of 1.8–23 μm are established.