Russian Journal of Physical Chemistry A最新文献

A stochastic approach is used to numerically study kinetics of the population of the triplet state of an electron donor molecule caused by photoinduced electron transfer from a donor to a paramagnetic acceptor and back. Conditions are determined and a general strategy is formulated for achieving maximum efficiency of the electron transfer-induced accumulation of triplet molecules. It is shown that solvents with fast dielectric relaxation contribute to an increase in the efficiency of the considered process.

Diffuse reflectance infrared Fourier transform spectroscopy of adsorbed carbon monoxide is used along with X-ray absorption spectroscopy to study the effect a second alloying metal (Zn, Cu) has on the electronic state and local structure of rhodium on the surfaces of Rh/HZSM-5 zeolite catalyst. It is established that introducing copper and zinc helps improve the stability of rhodium toward aggregation (the formation of clusters) under conditions of the oxidative carbonylation of methane into acetic acid. Compared to monometallic catalyst Rh/HZSM-5, where single atom rodium sites are partially aggregated into clusters, the proportion of Rh° is halved in the case of Rh–Zn/HZSM-5, and Rh clustering does not occur in the case of Rh‒Cu/HZSM-5. The stabilizing effect of Cu is due to the interaction between copper and rhodium cations on the surface of zeolite.

The interaction of the heterocyclic amino acid L-histidine (His) with the structural isomers of pyridinecarboxylic acids: picolinic (PA), nicotinic (NA), and isonicotinic (INA) acids in a phosphate buffer at pH 7.4 and T = 298.15 K was studied by calorimetry. The thermodynamic parameters were determined: binding constants, enthalpies of complexation, Gibbs energies, and entropies. It was established that for His and pyridine monocarboxylic acids, hydrogen bonding and electrostatic interactions are the main forces determining complexation in the buffer solution, as indicated by large negative enthalpy values and positive entropy values. The stability of the resulting complexes depends on the structural isomerism of pyridinecarboxylic acid and increases in the series: PA < NA < INA. It is shown that the enthalpy component of the Gibbs free energy of complexation makes the main contribution to stabilization of the formed complexes.

β-Ga₂O₃ is a wide bandgap material with promising applications in high performance electronics. Dopants play a vital role in optimizing device performance. Here, we systematically discussed the stability, electronic structure, and optical properties of trivalent rare earth ion (RE) doped β-Ga₂O₃ using the general gradient approximation method and Hubbard term. The theoretical results show that the doping systems, β‑Ga₂O₃:RE (RE = La, Ce, Pr, Nd, Pm, Sm, and Eu), are all stable and easy to form. It is worth noting that the β-Ga₂O₃:RE system becomes more stable with the decrease of the radius of the doping ions. When RE are doped into β-Ga₂O₃, the band gap is reduced and spin asymmetry occurs. The Nd, Pm, Sm, and Eu doping introduces the spin-up impurity energy level, which consists mainly of RE-4f states orbitals. Simultaneously, RE-4f induces spin asymmetry, causing the system to develop some magnetism. It is interesting to note that as the atomic number increases, the energy levels of the impurities move sequentially towards the top of the valence band. The conductivity of the system increases after the rare earth is doped with β-Ga₂O₃. And the absorption spectra of β-Ga₂O₃ show a red shift, which indicates that the visible light absorption of β‑Ga₂O₃ is improved by doping with rare earth elements, especially Sm and Eu.

In this study, a new azo derivative, namely methyl-5-((2-chloro-4-((2-(diethylamino)ethyl)carbamoyl)-5-methoxyphenyl)diazenyl)-2-hydroxybenzoate, was successfully synthesized through a multistep process involving the diazotization of metoclopramide, the addition of methyl salicylate, and subsequent temperature and pH adjustments. The synthesis yielded azo compound with 90%, and its structure was characterized using FT-IR and 1H-NMR spectroscopy. The synthesized azo compound was then evaluated as a corrosion inhibitor for carbon steel C45 in 0.1 M HCl, employing potentiodynamic polarization technique (Tafel extrapolation) over a temperature range of 293 to 313 K. The corrosion inhibition efficiency exhibited a concentration-dependent increase, reaching 94% at 300 ppm inhibitor concentration at 293 K, accompanied by a shift in corrosion potential towards the negative direction, indicating the cathodic nature of the inhibitor. Thermodynamic analysis revealed the influence of temperature on the corrosion inhibition efficacy, demonstrating increased activation energy and endothermic dissolution of carbon steel. These observations were supported by the theoretical density functional theory (DFT) method at the B3LYP/6-311++G basis set for the inhibitor.

A numerical two-dimensional spatial model is used to describe experimental results from the literature on the concentrations of O₂(a¹Δ_g) and O₂(b¹(Sigma _{{text{g}}}^{ + })) in a fast-flowing gas system free of plasma–chemical processes with the participation of electrons and ions. The concentration profiles of O₂(a¹Δ_g) and O₂(b¹(Sigma _{{text{g}}}^{ + })) are found to depend on gas pressure, the fraction of oxygen atoms in O/N₂ mixtures, and additions of O₂ to the gas mixture. The model emphasizes the need to consider detailed vibrational kinetics of ozone and its formation on the surfaces of tube walls. A new interpretation is proposed for the three-body recombination of oxygen atoms on M = N₂, O₂, allowing for the reverse dissociation of the produced highly excited molecules. The resulting functional dependence of recombination rate coefficient k_rec(T) is obtained and agrees well with the available measured temperature dependences k_rec(T). Pathways for the subsequent relaxation of excited oxygen molecules and atoms are identified.

The authors explore the possibility of synthesizing highly loaded mixed aluminum–cobalt spinels via the hydrochemical treatment of suspensions of a powder of the product of the centrifugal thermal activation of gibbsite in aqueous solutions of cobalt nitrate under room-temperature or hydrothermal conditions via X-ray diffraction, thermal, microscopic, adsorption, and chemical analysis. It is found that the heat treatment of products of hydrochemical interaction (xerogels) in the range of 350–850°C produces Co₃O₄ and CoAl₂O₄ spinel phases with different phase ratios, depending on the conditions of synthesis. The hydrochemical treatment of suspensions at room temperature ensures the dominant formation of a Co₃O₄ phase after calcination, while hydrothermal treatment at 150°C results in deeper interaction between the suspension components during treatment, ensuring the formation of CoAl₂O₄ after heat treatment. It is shown that the maximum content of CoAl₂O₄ spinel (90%, according to H₂-TPR) is observed for the hydrothermal product calcined at a temperature 850°C. The considered technique yields complex aluminum–cobalt compounds with different phase ratios, allowing the complete elimination of effluents. It also reduces the number of stages of synthesis, the amount of initial reagents, and 75 wt % of the total amount of nitrates, relative to using classical nitrate coprecipitation.

The colloid-chemical properties of water-soluble and poorly soluble poly(ethylene oxide) and poly(propylene oxide) block copolymers (pluronics), as well as the rheological properties of interfacial adsorption layers (IALs) formed by them and the polymer generated during polymerization initiation on the particle surface, were studied. The temperature, surfactant concentration, and polymer effects on the effective elastic modulus, determined during the lateral deformation of IALs, were evaluated. The strongest interfacial layers are formed by the poorly water-soluble pluronic, which contains a hydrophilic polyoxyethylene block surrounded by two hydrophobic polyoxypropylene blocks. The high strength of the interfacial adsorption layer on the particle surface affords polymer suspensions with high (up to 33%) polymer contents and narrow particle size distributions.

The present study reports on the synthesis of an ionic liquid-based nanocomposite and its characterization via structural, thermal and electrical analysis. The compound (M-EtOHmim) was prepared using green chemistry, where the organic cations exchange was achieved through the intercalation of 1‑(hydroxyethyl)-3-methylimidazolium chloride. The results showed that the molecules were successfully immobilized in the matrix yielding a good thermal stability up to 260°C. The DFT computation optimization was carried out to identify the adsorption mechanism. On the other hand, the electrical conductivity analysis revealed that charge transport is strongly related to structural defects and thermal energy. Accordingly, the corresponding electrical parameters were determined. It is evident that the modifications of montmorillonite with ionic liquid significantly changes the physicochemical properties of M-EtOHmim nanocomposite, which can be used in various fields.

Corrosion of low-carbon steel in a flow of H₂SO₄ solutions containing Fe₂(SO₄)₃ was studied, including media with additions of corrosion inhibitors—catamine AB (a mixture of quaternary ammonium salts) and IFKhAN-92 (3-substituted derivative of 1,2,4-triazole). In these media, partial reactions of anodic ionization of iron and cathodic reduction of H⁺ and Fe(III) cations occur on steel. The former two reactions are kinetically controlled, while the latter is diffusion-controlled. The accelerating effect of Fe₂(SO₄)₃ on steel corrosion in an H₂SO₄ solution is primarily due to the reduction of Fe(III). In contrast, in the inhibited acid, the accelerating effect of Fe(III) cations affects all partial reactions of steel. Data on corrosion of low-carbon steel in the flow of the given media, obtained from the mass loss of the metal samples, are in satisfactory agreement with the results of the study of partial electrode reactions. Steel corrosion in a flow of H₂SO₄ solutions, including in the presence of inhibitors, is accelerated by Fe₂(SO₄)₃. In these solutions, steel corrosion is determined by the convective factor, which is characteristic of diffusion-controlled processes. The IFKhAN-92 inhibitor, unlike catamine AB, significantly slows down steel corrosion in the flow of H₂SO₄ solution containing Fe₂(SO₄)₃. The reason for the higher inhibitory effects shown by IFKhAN-92 for steel in these solutions compared to catamine AB is the more significant slowdown of the partial electrode reactions of the metal.