Russian Journal of Physical Chemistry A最新文献

A new theoretical approach attacking the process of sonoluminescence in water is presented. It suggests that light is generated through the transformation of a two-dimensional plasmon formed on the surface of a collapsing cavitation bubble, which occurs due to the condensation of dipoles in saturated water vapor. According to this model, the key features of sonoluminescence are explained by the strong electromagnetic fields associated with the plasmon. The proposed model adequately reproduces the typical shape of the sonoluminescence spectrum. Its fine structure is attributed to the giant Raman scattering of plasmon radiation by impurity gas atoms in water solutions. Additionally, the model accounts for the experimentally observed relationship between light yield, temperature, and pressure.

The intermolecular interactions of DNA/RNA with drugs exhibit important applications in human health and drug design. We investigated the interaction between ascorbic acid (AA), a commonly used drug in clinic, and cytosine, an important base of nucleic acids in DNA/RNA, using cyclic voltammetry (CV), ¹H NMR, density functional theory (DFT), quantum theory of atoms in molecules (QTAIM), natural bond orbital (NBO) and independent gradient model based on Hirshfeld partition (IGMH). The CV and ¹H NMR results revealed that the hydroxyl groups on the enediol of AA interacted with cytosine, making the electro-oxidation of AA difficult to occur and the downfield shift of H atoms (CH) on cytosine ring. Quantum chemistry calculations further proved the existence of O–H⋅⋅⋅N, O–H⋅⋅⋅O, C‒H⋅⋅⋅N, C–H⋅⋅⋅O, and N–H⋅⋅⋅O hydrogen bonding in the mixed system. It was found that the H atoms (H9 and H11) on enediol of AA, the N atom (N31) and carbonyl oxygen atom (O32) on the cytosine ring were the main action sites, for which H11 and N31 are more prone to be interacted with than H9 and O32.

Growing demands for quality and diversity of microelectronic devices require innovative approaches to designing and creating high-precision components, which is associated with the increasing complexity of device architecture and miniaturization of elements. Additive methods for forming microsized structures, including aerosol printing, are becoming a promising addition and, in the µm size range, an alternative to traditional photolithography due to reduced costs and process flexibility. A new approach has been developed, and a dry aerosol printer has been created based on the synthesis of nanoparticles in a pulsed gas discharge, their transportation in a gas flow, focused deposition, and sintering by laser radiation, which eliminates the use of solvents and functional additives. This enables the creation of clean microstructures without post-processing, which opens up wide possibilities for integrating dry aerosol printing into microelectronics process routes. The method is relevant for the formation of passive elements of microelectronics, plasmonic layers of optoelectronic devices, microsensors, and catalytic structures.

The polyacrylamide gel method (PGM) was applied to synthesize pure BaTiO₃ by using tetrabutyl titanate as the titanium source and adding NaOH to the precursor solution. A systematic investigation was performed to analyze the impact of the titanium source, acid, base, and sintering temperature on the purity of the BaTiO₃ phase. Using a PGM with NaOH in the precursor solution, tetrabutyl titanate as the titanium source, and a sintering temperature of 950°C is an effective way to obtain pure BaTiO₃. The BaTiO₃ exhibits high catalytic activity for the degradation of methylene blue (MB) dye under vibration and light irradiation conditions in situ, with or without the addition of 2 mL of H₂O₂. The catalytic experiments proved that the optimal catalyst content, dye concentration, cycle index and H₂O₂ concentration of the BaTiO₃ for the degradation of MB dye were 1.5 g/L, 10 mg/L, 4 and 2 mL, respectively. Under the conditions of ultrasound + light + O₂, BaTiO₃ produced hydrogen peroxide with a concentration of 1135 μmol/g in 180 min, providing conditions for the in-situ generation of hydrogen peroxide and the degradation of MB dye. According to in-situ experiments, BaTiO₃ can degrade MB dye completely within 90 min. A mechanism that combines vibration catalysis and photocatalysis was proposed based on numerous experiments and theoretical discussions. The technical reference provided by this experimental idea can be used by other catalysts to generate hydrogen peroxide in-situ and degrade organic dyes.

In relation to low temperature ortho–para-hydrogen conversion in the low-pressure range, the catalytic activity of systems based on Cu, Ag, and Au nanoparticles supported on γ-Al₂O₃ and bimetallic nanoparticles of the Cu–Ag and Au–Ag systems, as well as industrial Ni/Al₂O₃ and α-Fe₂O₃ samples, was determined. The ortho–para-conversion reaction on nanoparticles of group 1B metals occurs via a magnetic mechanism. Monometallic nanoparticles showed a higher activity than industrial samples. Cu and Ag demonstrated a pronounced synergistic effect during interaction. The catalytic activity of the copper-based sample with the addition of silver exceeds by more than 2 times the activity of the individual metal particles that form it and by 3 and 9 times the activity of the Ni/Al₂O₃ and α-Fe₂O₃ samples, respectively. The obtained data indicate the potential of Cu- and Ag-based bimetallic nanoparticles for low-temperature ortho–para-hydrogen conversion; however, research into their catalytic properties in the high-pressure range is necessary.

The mixing of hydrogen and air is investigated experimentally by injecting hydrogen into air and vice versa. The modes of mixing are investigated at volumetric flow rates of the injected gas ranging from 5 to 50 L/min, final absolute pressures of the mixture ranging from 1 to 5 atm, and final hydrogen concentrations ranging from 10 to 60 vol %. When injecting hydrogen into air, characteristic periods of mixing range from 3 to more than 24 h. When injecting air into hydrogen, characteristic periods of mixing range from 1.2 min to 1.2 h. The measured periods of mixing are approximated using empirical formulas.

Composite aerogels have been produced from reduced graphene oxide (rGO) with polytetrafluoroethylene and soy wax (rGO/PTFE and rGO/wax aerogels, respectively). It has been established that the specific capacity Q_w of the rGO/wax aerogel for solvents, oil, and petroleum products under comparison exceeds that of the rGO/PTFE aerogel. At the same time, the maximum value of the water-wetting angle for a flat surface of the rGO/wax aerogel was 142.4°, whereas this value for the rGO/PTFE aerogel was usually in the range of 161.9°−163.7°. Using the method of differential scanning calorimetry (DSC), it has been shown that the melting point of wax in the rGO/wax aerogel is by approximately 11°C lower than that of pure wax. In addition, the effect of swelling during sorption of solvents has been established for the rGO/wax aerogel. The work has shown among other things that high sorption capacity of material with respect to petroleum products depends not only on its hydrophobicity and oleophilicity, but also on its swelling capacity.

The liquid–solid and liquid–vapor phase equilibria in the oxalic acid (H₂Ox)–citric acid (H₃Cit)–water system at a temperature of 298.15 K (25°C) and 298.15–308.15 K, respectively, are studied. The stability regions of the H₃Cit⋅H₂O and H₂Ox⋅2H₂O crystalline hydrates are determined. Experimental data on water activity for solutions of the oxalic acid–citric acid–water ternary system are obtained; the saturated vapor pressure above solutions of the H₃Cit–H₂Ox–H₂O system is measured by the static method; water activity is determined by the dew point method. It is shown that water activity depends on temperature only slightly in a temperature range of 298.15–308.15 K. The solubility products of H₃Cit⋅H₂O and H₂Ox⋅2H₂O are calculated using the Pitzer model. A model that describes the thermodynamic properties of solution and phase equilibria in the H₃Cit–H₂Ox–H₂O ternary system with an accuracy that is not inferior to the experimental accuracy is developed.

The corrosion of low-carbon steel in solutions of 1 M H₂SO₄ + 1 M H₃PO₄ containing Fe(III) salts is studied relative to similar solutions of 2 M H₂SO₄ and 2 M H₃PO₄. Steel corrodes in these systems by reacting with the acid solution and salts of Fe(III). Partial reactions of the anodic ionization of iron and the cathodic reduction of H⁺ and Fe(III) cations occur on steel. The first two are characterized by kinetic control; the last, by diffusion control. The accelerating effect Fe(III) cations have on the corrosion of steel in the studied environments is mainly due to the reduction of Fe(III). A rotating steel disk electrode is used to study the effect the nature of solution convection has on the kinetics of Fe(III) reduction in the considered corrosion systems. Coefficients of diffusion are determined for Fe(III) cations in solutions of H₂SO₄, H₂SO₄ + H₃PO₄, and H₃PO₄ via the cyclic voltammetry method with using a Pt electrode, allowing the construction of model dependences of the cathode current density of a steel disk on its frequency of rotation. The dependences are then compared to experimental data in order to establish the reasons for the observed differences. It is assumed that the differences are determined by the release of hydrogen gas on steel, which both shields the steel’s surface and changes the flow of the aggressive environment near the electrode from laminar to turbulent. Empirical dependences of the rate of steel corrosion on the intensity of the medium’s flow in the considered environments, obtained using data on the mass loss of metal samples, are described by linear equation k = k_st + λw^1/2, where k_st is the rate of steel corrosion in a static environment, w is the speed of rotation of the propeller mixer that creates the flow of the medium, and λ is an empirical coefficient.

A dicationic ionic liquid of 1,2-bis(1-methylimidazolium-3)ethane dibromide of a new composition, having a solid state of aggregation, has been synthesized. The presence of the corresponding functional groups in the structure of the ionic liquid was confirmed by IR Fourier and NMR spectroscopy. It was established by viscosimetry that the viscosity of an aqueous solution of the dicationic ionic liquid increases with concentration due to association of the dicationic ionic liquid and water molecules. A conductometric study showed that the electrical conductivity increases with the concentration and temperature of the dicationic ionic liquid. The melting point of the obtained dicationic ionic liquid is 236 ± 0.5°C. The high melting point of the dicationic ionic liquid is explained by steric hindrances, caused by the fact that the imidazolium cations are linked to each other by an ethane chain, which promotes the convergence of ions and, as a result, does not prevent hydrogen bonding. At increased concentrations of the dicationic ionic liquid in aqueous solution, the surface tension of solutions decreases. The ion association is characterized by the negative Gibbs energy and enthalpy of aqueous solutions, which indicates that the interaction is spontaneous and exothermic.