Russian Journal of Physical Chemistry B最新文献

The study presents a comparative analysis of the machine learning methods effectiveness for classifying Raman spectra to enable automated identification of organic and inorganic compounds. A dataset contains about 2000 spectra of 20 organic and inorganic compounds, obtained using a 785 nm laser source, was compiled for the research. The experimental setup included a laser, optical elements for signal shaping and filtering, and a diffraction gratings spectrometer for data acquisition. Prior to model training, baseline correction and normalization of spectra to the maximum value were performed. The classification algorithms employed were logistic regression, support vector machines, random forest, gradient boosting, k-nearest neighbors (k-NN), as well as a combination of k-NN with dimensionality reduction via principal component analysis. Test experiments performance was evaluated using receiver operating characteristic (ROC) analysis and the area under the curve (AUC) metric was calculated. An analysis of algorithm parameters, runtime, and spectral data processing specifics was conducted, enabling a comprehensive characterization of each method for the given dataset. The implementation of machine learning methods for the identification of organic and inorganic compounds with a signal-to-noise ratio of about 8 and an AUC value of at least 0.95 for binary classification is shown.

Silicon carbide (SiC) has been designed and charchterized as an anode electrode for lithium (Li), sodium (Na), beryllium (Be) and magnesium (Mg)-ion batteries due to forming Li₂(SiC), Na₂(SiC), Be₂(SiC) and Mg₂(SiC) nanoclusters. A vast study on energy-saving by Li₂(SiC), Na₂(SiC), Be₂(SiC) and Mg₂(SiC) complexes was probed using computational approaches due to density state analysis of charge density differences (CDD), total density of state (TDOS), electron localization function (ELF) for hybrid clusters of Li₂(SiC), Na₂(SiC), Be₂(SiC) and Mg₂(SiC). A small portion of Li, Na, Be or Mg entered the Si–C layer to replace the alkali and alkaline earth metals sites could improve the structural stability of the electrode material at high multiplicity, thereby improving the capacity retention rate. Higher Si/C content can increase battery capacity through Li₂(SiC), Na₂(SiC), Be₂(SiC) and Mg₂(SiC) nanoclusters for energy storage process and improve the rate performances by enhancing electrical conductivity. Besides, SiC anode material may advance cycling consistency by excluding electrode decline and augments the capacity owing to higher surface capacitive impacts.

This paper studies the chemical modification of a polymer promising for the development of gas separation membranes to improve its CO₂ selectivity. The possibility of the introduction of butylimidazolium bromide (BIm⁺Br^–) into the structure of poly(1-trimethylsilyl-1-propyne) (PTMSP) using a two-stage process—bromination of the initial polymer with N-bromosuccinimide and subsequent interaction with a tertiary amine, N-butylimidazole—is demonstrated. Supercritical CO₂ and CHF₃, which have a number of advantages over organic solvents, such as nontoxicity, nonflammability, and environmental safety, are used as the reaction media. Depending on the conditions of the process, the proposed method makes it possible to regulate the BIm⁺Br^– content in the polymer structure. The resulting modified polymers are characterized by good film-forming properties, thermal stability, and increased resistance to aliphatic, alicyclic, halogenated, and aromatic hydrocarbons. It is found that with an increase in the BIm⁺Br^– content in the polymer, the selectivity of CO₂/N₂ and CO₂/CH₄ separation increases while maintaining high gas permeability. These results open up new possibilities for the development of efficient membrane materials for gas separation in industrial conditions.

A thermodynamic assessment of the optimal conditions for obtaining hydrogen during ammonia pyrolysis in a Swiss-roll reactor with separate supply of ammonia and air was carried out. The calculations were carried out for a volumetric flow of ammonia equal to 1 mol/s at atmospheric pressure. To evaluate the modes of ammonia pyrolysis with the production of hydrogen, the proportion of hydrogen burned was varied by changing the molar flow of oxygen. The ratio of volumetric gas flows and thermal powers of incoming and outgoing flows was calculated. Optimal process characteristics for different values of ammonia pyrolysis temperature have been determined.

Rhein (C₁₅H₈O₆), a natural hydroxyanthraquinone compound widely found in traditional Chinese medicinal herbs, exhibits a range of pharmacological activities due to its unique planar structure, including anticancer, anti-inflammatory, antimicrobial, and anti-Alzheimer’s disease effects. This study employed density functional theory to comprehensively analyze the reactive sites of the rhein molecule using various theoretical methods, including: localized orbital locator (π-electron), Mulliken charges, electrostatic potential, atomic local ionization energy, and dual descriptor. This study not only provides a molecular-level mechanism for understanding the bioactivity of rhein but also offers theoretical guidance for the development of novel rhein derivatives to enhance their biological activities.

Scavenging hazardous gases of carbon monoxide (CO) and nitrogen oxide (NO) by using transition metals of Cr, Co, Cu, Zn which have been implanted on the boron nitride nanocage, (BN₂)₅, have been studied by computational chemistry. Based on NQR analysis, X-substituted on (BN₂)₅ has shown the lowest fluctuation in electric potential and the highest negative atomic charge. Moreover, the parameters of NMR method have indicated that the yield of electron accepting for atom substitution on the BN(X) through gas molecules adsorption can be ordered as: Cu > Co ( gg ) Cr > Zn for CO adsorption and Co ≈ Cr > Cu > Zn for NO adsorption that exhibit the strength of covalent bond between chromium, cobalt, copper, zinc, and CO or NO towards toxic gas removal from air. In fact, the adsorption of CO or NO gas molecules can remark spin polarization on the BN(X) which specifies that these nano-surfaces may be employed as magnetic scavenging surface as a gas detector. Regarding IR spectroscopy, substituted nanocages of BN(Cr), BN(Co), BN(Cu) and BN(Zn), respectively, have the most fluctuations and the highest adsorption tendency for gas molecules which can direct specific inquiries on the individual impact of charge carriers (gas molecule-nanocage), as well as atom substitution on the overall structure. Gibbs free energy has shown that the maximum efficiency of (Cr, Co, Cu, Zn)-substituted on (BN₂)₅ for gas molecules adsorption depends on the covalent bond between CO or NO molecules and BN(X) as a potent sensor for air pollution removal.

For the first time, a noncatalytic transesterification reaction (alcoholysis) of bornyl acetate in commercial fir needle essential oil (FNEO) is carried out using supercritical lower alcohols: methanol, ethanol, and isopropanol. Only the use of methanol is shown to ensure high conversion and selectivity of the reaction. For example, at 350°C after 1 h of the reaction in an autoclave reactor, 93% selectivity for borneol with 90% conversion of bornyl acetate is achieved. A further increase in the reaction time leads to a decrease in selectivity for borneol due to an unexpected increase in the concentration of camphor.

Cell-based cancer analysis constitutes a significant investigatory methodology for monitoring the progression of cancer across different stages by quantifying the density of circulating tumor cells (CTCs) present in the bloodstream. Among the array of contemporary microfluidic techniques, dielectrophoresis (DEP), recognized as an electrokinetic phenomenon and a label-free detection modality, is particularly esteemed by researchers in the field. In the present study, a microfluidic device featuring semi-circular electrodes operating at a low voltage of approximately 1.5 V is proposed with the objective of isolating CTCs from various subtypes of white blood cells (WBCs). The employment of a low voltage is essential for maintaining the viability of biological cells, an aspect of paramount importance in medical applications. Through computational simulation with the finite element method, the electric potential profiles, the paths of the cell particles, and the DEP forces on cells were elucidated.

Lean hydrogen-air flames exhibit pronounced susceptibility to intrinsic instabilities. Discrepancies in thermal and mass diffusivities subject these flames to coupled thermodiffusive and hydrodynamic instabilities, complicating practical implementation of hydrogen-based fuels. Small-scale perturbations on an initially planar flame front grow exponentially, inducing local acceleration and wrinkling. While early-stage evolution under infinitesimal perturbations is well-studied theoretically and numerically, real-world scenarios involve finite-amplitude perturbations (e.g., from obstacles, droplets, particles, or non-uniform flows)—a regime requiring further investigation. This study numerically examines instability development triggered by both small-scale perturbations and perturbations with amplitudes comparable to the flame thickness. Two initiation mechanisms are implemented: (1) localized temperature elevation and (2) finite-amplitude spatial distortion of the flame front. Results demonstrate that initial perturbation amplitude critically influences instability patterns, alters growth rates, and can destabilize modes otherwise stable under infinitesimal disturbances. These findings support development of subgrid combustion models and can be used for the analysis and interpretation of flame propagation phenomena in multiphase systems.

Polyvinyl alcohol/alumina precursor solution was prepared using economical aluminum chlorohydrate as the aluminum precursor and water as the solvent. The precursor solution was subsequently employed in electrospinning process to yield alumina nanofibers. The relationship between various Polyvinyl alcohol factors, such as degree of hydrolysis, molecular weight and dosage, and morphology of alumina nanofibers via electrospinning method was studied. The Polyvinyl alcohol with a lower molecular weight was used, the precursor solution viscosity decreased, facilitating the finer alumina nanofibers. Conversely, higher molecular weights of Polyvinyl alcohol resulted in more viscous solution, giving rise to coarser fibers that were prone to breakage. Notably, when Polyvinyl alcohol model 1788, characterized by an alcohol alcoholysis degree of 88% and a molecular weight of approximately 75 000, was used as the spinning aid, the precursor solution displayed remarkable stability as Newtonian fluid behavior. When Polyvinyl alcohol of type 1788, 1799, 2488 and 3588 was used as spinning aid, the crystal grain sizes of the prepared alumina fibers were 27, 107, 68 and 144 nm, and the pore sizes of the fibers were 40, 90, 78 and 121 nm, respectively. It indicated that the pore size and grain size of the alumina fibers prepared electrospinning were relative with the molecular weight and alcohololysis degree of Polyvinyl alcohol As the dosage of Polyvinyl alcohol increases, the viscosity of the precursor solution increases, and the diameter of the final fiber increases. The 1788 precursor solution was also found to be optimal for the electrospinning process, enabling the production of a significant quantity of fibers with superior morphology. The resulting fibers possessed a diameter of 250 nm and were composed of the α-Al₂O₃ phase.