Russian Journal of Physical Chemistry B最新文献

A modified version of the use of the sol-gel process at the initial stage of the synthesis of a high-temperature superconductor Y_1–xFe_xBa₂Cu₃O_y with low Fe doping is proposed. The properties of the samples obtained by sol-gel and solid-state synthesis are compared. It is shown that a more uniform distribution of the dopant throughout the volume of the sol-gel samples makes it possible to obtain materials with improved microstructural and performance characteristics.

Composites of polyether polylactide (PLA) synthesized from natural raw materials with graphite nanoplatelets (GNPs), which represent a new type of composite materials based on biodegradable polymers, are obtained by the solid-phase method under the action of shear deformations. The porosity of the composites is evaluated and their electrical and mechanical properties are studied. The effect of UV radiation on the molecular weight and molecular weight distribution of PLA in PLA–GNP composites of different composites is investigated using the method of exclusion chromatography, and the effect of GNP nanofiller content on the change of their mechanical characteristics in the process of radiation is shown.

The aggregation properties of a number of 6,6'-disubstituted thiacarbocyanine dyes are studied by spectral-fluorescent methods: T-304, T-306, T-307, T-336 and, for comparison, thiacarbocyanine Cyan 2, which has no substituents in the 6,6'-positions, in aqueous buffer solutions, or in the presence of various types of surfactants. The method of moments is used to characterize the absorption spectra (band positions, width, shape). Substituents in the 6,6'-positions significantly increase the ability of dyes T-304, T-306, T-307, and T-336 to aggregate (dimerization and the formation of disordered aggregates with broad low-intensity absorption spectra). The introduction of surfactants leads to the rearrangement of the spectra associated with the complex nature of the equilibria between monomers and aggregates of various structures (including surfactant molecules, if present), and in particular, with a decrease in the contribution of disordered aggregates. However, the decomposition of dimeric aggregates of 6,6'-disubstituted cyanines is observed only at very high surfactant concentrations (~20 CMC or higher, where CMC is the critical micelle concentration). At the same time, the passing of surfactant concentrations through CMC does not significantly affect the spectral-fluorescent properties of the dyes, which is probably due to the rather strong interactions of the dyes with individual surfactant molecules and premicellar associates of the surfactants.

The photochemistry of the [Ir^IIICl₆]^3– complex in aqueous solutions is studied by the methods of stationary and laser flash photolysis. As a result the of absorption of a light quantum, parallel processes of photoaquation and photoionization occur. The aquated electron ({text{e}}_{{{text{aq}}}}^{ - }), which is formed with a quantum yield of 0.12 (excitation at 266 nm), is predominantly decayed in reactions with the initial complex and dissolved oxygen. The rate constant of the ({text{e}}_{{{text{aq}}}}^{ - }) capture by the [Ir^IIICl₆]^3– complex is measured. The main final photolysis products are Ir(III) complexes with different compositions of ligands and several percent of Ir(IV) complexes. The final products are formed in the time range from milliseconds to seconds.

The adsorption of four CO, CO₂, NO, NO₂ gas molecules in the atmosphere on titanium (Ti)‑doped monolayer SiC surface was investigated using the density functional theory (DFT) with equilibrium geometries optimized at the CAM-B3LYP/6-311+G(d, p) level of theory. The thermochemical, electric and magnetic properties data recommend that the adsorption of these gas molecules on Ti-embedded SiC sheet (SiC_sh) monolayer is more energetically desired than that on the pristine ones. Gas molecules of CO, CO₂, NO, NO₂ have been adsorbed on the Ti site of doped SiC monolayer through the formation of covalent bonds. Moreover, after the adsorption, the orientations of the gas molecules exhibited a tendency to orient in the inclined and parallel forms to monolayer SiC_sh. The DFT analysis explored that the monolayer SiC_sh with C and Ti-doped atoms possessing one satisfied valency increased the Van der Waal interactions between the gas molecules and the monolayer SiC_sh. Furthermore, the assumption of chemical adsorptions has been approved by the projected density of states (PDOS) and charge density difference plots. Charge density difference calculations also indicate that the electronic densities were mainly accumulated on the adsorbate of CO, CO₂, NO, NO₂ gas molecules. The results in this investigation can indicate the competence of transition metal doped silicon carbide nanosheet in sensor devices. The overall analysis showed that the adsorption strength of monolayer SiC_sh towards the chosen gas molecules follows the order: NO₂ > CO₂ > NO > CO.

In order to solve the problems of high elastic modulus and biotoxicity of human bone implants, Ti10Mo28Nb3Zr, a component with low elastic modulus that had been calculated and verified by first-principles experiments, was used as raw material to prepare bone implant titanium alloy with low elastic modulus and good biocompatibility by means of gel injection and microwave sintering methods. The effects of solid content on gel curing time, shrinkage, porosity, compressive strength and elastic modulus of the materials were analyzed by scanning electron microscope, X-ray diffraction, metallographic microscope and compression tests. When the solid phase content increases from 30 to 45%, the gel time reduces from 300 to 205 s. This indicates that a higher solid phase content results in a shorter gel curing time. Meanwhile, the axial shrinkage decreased from 13.67 to 6.43%, and the radial shrinkage decreased from 13.11 to 6.18%. Moreover, the compressive strength increased from 125 to 215 MPa, the elastic modulus increased from 10.46 to 25.11 GPa. The results provide a basis for the preparation of medical bio-titanium alloy by gel injection molding and its application in bone implant materials.

Estimates are made showing that when an exothermal reaction proceeds in an isothermal medium (in a thermostat), self-heating occurs, whose values are determined by the competition between the processes of heat input and heat removal. Relationships are obtained that make it possible to estimate the deviation of the observed values of the kinetic parameters from the true values and to reveal the influence of various parameters on these deviations.

The interaction of glycyrrhizin with the transmembrane domain of the E-protein of the SARS-CoV-2 virus (E-protein Trans-Membrane domain, ETM) in a homogeneous aqueous solution and in a model lipid membrane is studied using the selective nuclear Overhauser effect (selective NOESY) and NMR relaxation methods. The selective NOESY shows the presence of the interaction of glycyrrhizin with ETM in an aqueous solution, which is consistent with the published modeling data, which indicate the possibility of penetration of the glycyrrhizin molecule into the channel formed by the ETM molecules. However, this conclusion is not confirmed by the NOESY experiments in the model lipid membranes—bicelles. At the same time, the NMR relaxation method reveals the effect of glycyrrhizin on the mobility of both lipids and ETM molecules in bicelles. This suggests that GA affects the activity of the coronavirus E-protein indirectly through lipids.

The reflux technique was used to synthesize praseodymium-doped cadmium sulfide nanoparticles (Pr³⁺: CdS) with different doping concentrations 0, 5, 7, 9 and 11 at %. According to X-ray diffraction the samples were crystalline and hexagonal phase. Agglomerations of nanoparticles were observed from scanning electron microscopy image. When excited at 423 nm transitions of ³P₁ → ³H₅, ³P₀ → ³H₅, ³P₀ → ³H₆, ³P₀ → ³F₂ are obtained from the photoluminescence studies. The position, sharpness, and intensity increased with increase in concentration. Commission internationale de l’eclairage diagram shows that Pr³⁺ doped CdS had a hue almost white light, indicating that it might be used for solid-state illumination. For degrading methylene blue and methyl red, it was found that catalyst dose of 5 mg/L, pH 9 and pH 11 shows the best degradation percentage which is 89 and 94% respectively. Pr³⁺ doping enhanced methyl red and methylene blue degradation by photocatalyst. The experimental data matched both the Langmuir–Hinshelwood (L–H) and pseudo-first-order kinetics models. At the same ideal experimental conditions, the pseudo-first-order provided a better fit than the Langmuir–Hinshelwood kinetic model. The research suggests that Pr³⁺ doped CdS may operate effectively as a photocatalyst to detoxify harmful colors from wastewater.

The cytotoxicity indices (IC50) of Keggin’s phosphorus-molybdenum heteropoly acids (HPCAs) and their sodium and potassium salts on dog kidney cells (MDSC) are determined. The antiviral activity of these compounds against topical strains of influenza A (H3N2 and H1N1) is revealed. The dependence of the biological properties of polyoxometalates on the elemental composition of their molecules is confirmed. It is shown that when some of the molybdenum atoms are replaced by vanadium atoms, HPCAs and their salts acquire higher cytotoxicities, which increase monotonically as the number of substitutions increases. For the first time, the dependence of the biological activity of HPCAs and their salts on the mass of cations is established and interpreted. The values of semilethal doses (DL50) of these compounds are established in vivo (on outbred white mice). The values of the toxicity index (TI) for aqueous solutions of HPCA sodium and potassium salts are determined in a wide range of concentrations (from 0.05 to 15 μM) on a model of motile cells. It is established that HPCAs and their salts are moderately dangerous toxic substances and have selective antiviral activity, which at low concentrations (less than 15 μM) for influenza A strains is manifested mainly by a decrease in hemagglutination activity.