Doklady Physical Chemistry最新文献

The effects of components of intumescent systems based on silane-terminated polyether (STP) polymers on their thermolysis character were studied. Thermal analysis and fire-resistance tests showed that neither the molecular weight of the STP polymer, nor a moderate change in the ratio of components in the intumescent system relative to the selected base composition, has a significant effect on the thermolysis, whereas a change in the amounts of fillers such as kaolin and, in particular, titania, provides doubling of the fireproof rating of the studied coatings due to the structuring of the char foam formed upon thermal destruction and acts as a heat-insulating coating. These results may be of significant importance in the development of heat-expanding fire-protection compositions based on STP polymers.

This work is devoted to the search for methods of labeling powder materials. The labeling was performed with CdSe/CdS/ZnS quantum dots synthesized in an oleic acid medium. Cyanuric acid powder was selected as a bulk material model for the study. The choice of cyanuric acid as a model powder material was justified by its low toxicity, relative cheapness and accessibility, as well as insolubility in organic solvents used for the quantum dots synthesis. In addition, the criterion for choosing cyanuric acid was that its own luminescence spectrum was shifted relative to the spectra of the quantum dots selected for the study. The solubility of cyanuric acid in organic solvents used for the synthesis of quantum dots was evaluated; the flowability of the powder and the effect of exposure to solvents on it were analyzed. Samples of cyanuric acid powder marked with quantum dots with different luminescence peak positions and intensities were obtained. The luminescent properties of the obtained powders were investigated, the minimum amount of powder with quantum dots applied to the surface in the total composition sufficient for labeling was estimated, and the effect of applying quantum dots to the surface on the flowability of the powder was estimated. The possibility of marking bulk material with compositions of quantum dots with clearly defined monochromatic luminescence bands to create an invisible “fingerprint,” which is determined in laboratory conditions, is investigated.

The theoretical study of mechanical properties of the celecoxib (4-[5-(4-methylphenyl)-3-(trifluoromethyl)pyrazol-1-yl]benzenesulfonamide) form III crystal structure (space group P-1) has been carried out. For this purpose, increasing uniaxial deformations of the crystal structure along three axes of the crystal cell were simulated. To obtain the equilibrium structure of this crystal and structures under tensile strain, quantum-chemical calculations with periodic boundary conditions were performed by the DFT method at the PBE0/pob-DZVP2 level and by the HF-3c method with the following semiempirical corrections: Grimme dispersion correction (D3) for weak interactions, atom pair-wise geometrical counterpoise correction (gCP) for basis set superposition error, and correction for short-ranged basis set incompleteness effects (SRB). It was found that the analysis of stiffness tensor of only the equilibrium crystal structure did not provide the complete information about crystal mechanical behavior in different spatial directions, although this analysis made it possible to determine flexibility signs of the celecoxib structure in the (001) plane. In this case, the direction of maximal resistance of the structure to uniaxial deformation is not determined by specific intermolecular bonds and/or chains but is oriented almost parallel to the plane of conformationally rigid phenyl and pyrazole rings of the celecoxib molecule. The virtual tensile test has allowed to predict the manifestation of elastic properties of the celecoxib crystal in the (001) plane, up to 15% stretching along the crystallographic axes a and b. At greater strains along the a axis, a “non-healing” cavity is formed, which corresponds to the experimental observation of crystal transition to a brittle state. Analysis of the tensile test results confirmed the reliability of previously proposed brittleness/plasticity/elasticity signs for the prediction of dynamic mechanical properties, using the celecoxib crystal as an example.

Layered spheres of composition NiO/TiO₂–SiO₂–NiO have been synthesized, and their physicochemical, optical, and structural characteristics have been studied. These spheres consist of an inner nickel oxide layer and an outer TiO₂–SiO₂–NiO coating. The developed method allows to achieve a uniform distribution of elements and to enhance the interaction between the inner and outer layers. This increases the stability of the structure during heat treatment at the phase formation stage. Thermal analysis indicates that temperature significantly affects phase formation in TiO₂–SiO₂–NiO films. The temperature treatment mode that preserves the spherical shape of the material and facilitates the formation of nickel oxide and titanium dioxide in anatase modification has been selected: 100°C for 30 min, 200°C for 30 min, 300°C for 30 min, 350°C for 30 min, and 500°C for 1 h. This enables the achievement of optimal crystallization and adhesion between the layers. The nickel oxide incorporation into the TiO₂–SiO₂–NiO composition modifies the optical properties of titanium dioxide, reducing its band gap energy to 2.47 eV. This reduction enables visible light absorption, significantly enhancing photocatalytic potential. The synthesized NiO/TiO₂–SiO₂–NiO layered structures exhibit significant potential for environmental applications, including water and air purification, water splitting processes, and the degradation of organic pollutants under visible light.

The paper presents the results of experimental studies of the thermal characteristics of high-energy compounds based on low-sensitivity oxidants, 5-nitro-1,2-dihydro-3H-1,2,4-triazin-3-one, 1,3,5-triamino-2,4,6-trinitrobenzene, and 4,10-dinitro-2,6,8,12-tetraoxa-4,10-diazatetracyclo[5.5.0.0^5,9.0^3,11]dodecane, and tetrazole binders based on allylated poly-N-methyl-5-vinyltetrazole (PMVT-A). Differential scanning calorimetry and thermogravimetric analysis were used to study the thermal properties of the compositions, the features of thermolysis, and the chemical compatibility of the components. It was shown that binders based on PMVT-A plasticized with propylene glycol dinitrate or nitroamine/nitroester mixtures are fully compatible with the crystalline oxidant, 4,10-dinitro-2,6,8,12-tetraoxa-4,10-diazatetrcyclone[5.5.0.0^5,9.0^3,11]dodecane, and completely incompatible with 5-nitro-1,2-dihydro-3H-1,2,4-triazine-3-one.

The search for novel compounds with antimitotic properties has gained significant attention due to their potential to inhibit mitosis; which is crucial in cancer therapy as they can decrease the rapid division of cancer cells, potentially preventing tumor formation. In this study, we employed computational techniques, including DFT calculation, molecular docking and ADMET predictions to evaluate various properties such as chemical reactivity, intramolecular interactions, the inhibitory activity against an antimitotic target and pharmacokinetic properties of N-(4-acetyl-5-(4-(nitro)phenyl)-4,5-dihydro-1,3,4-thiadiazol-2-yl)-N-phenyl acetamide (NTPA). DFT calculations show that this compound exhibits more reactivity in polar medium with an electrophilic character. NBO analysis shows that a charge transfer is carried out within different fragments of the title compound. Our findings shed light on the potential of the title compound as a promising candidate for further development as an anticancer agent. ADMET predictions show that NTPA compound exhibits appreciable physicochemical and pharmacokinetic properties.

The paper considers the oxidation reactions of nanodispersed aluminum powder with water at room temperature in a reactor without stirring, heating, or other activation methods using a homogeneous mixture of powder with ice prepared in advance. The process is considered theoretically resorting to previously obtained data on the macrokinetics of reactions of dispersed aluminum with water, taking into account the melting of the ice mixture and warming-up to room temperature. An experiment confirming the obtained theoretical results is conducted. The solution to the problem of searching for controlled hydrogen generation modes in the reaction of nanoaluminum with water is relevant in connection with the development of hydrogen sources for fuel cells. The problem of optimizing the hydrogen generation modes in the aluminum reaction with water arises because the dynamics of the reaction of highly dispersed aluminum with water is accompanied by a sharp increase and sharp drop of the hydrogen pressure and begins even at room temperature, which complicates the preparation of the mixture under these conditions. Meanwhile, technologies using hydrogen as fuel require a uniform supply of the gas to the fuel cell. The paper describes the preparation of a homogeneous mixture of nanoaluminum powder with ice at a temperature below 273 K, when the reaction does not occur. Then the mixture is placed in a reactor at room temperature (290–298 K); the reaction begins gradually as the mixture is heated in a gradual mode without adverse abrupt self-heating effects. The temperature of the mixture, the degree of aluminum conversion, and the rate of hydrogen formation are measured as functions of time. The calculations were performed using the kinetic parameters for the Alex brand powder; it is considered that the mass of ice (water) significantly exceeds the stoichiometric one. Solution of the problem in the dimensionless form and the calculations resulted in interpolation equations for the time of complete aluminum conversion depending on the process control parameters. It is shown theoretically and experimentally that hydrogen is completely released in these process in a controlled mode within several hours, without thermal explosion caused by the exothermic reaction. The found patterns of the reaction can be further used to calculate the engineeting parameters of hydrogen generation systems using a pre-prepared mixture of nanoaluminum with ice.

In this current work, the potential antioxidant potency of the chosen Scutellarein is examined via quantum computations. The three prime mechanisms HAT, SETPT, and SPLET, followed by their extended version (tetra H-atom transfer (teHAT), tetra sequential electron transfer-proton transfer (teSETPT), and tetra sequential proton loss electron transfer (teSPLET)) extend their hands in explaining the active scavenging potential of Sc. The outcomes of the thermodynamical mechanisms show the H atom mechanisms is more prominent in showing the easy charge transfer pathway than that of the other two mechanisms in all three phases. The evaluation of the reaction enthalpy of Sc in different environments indicates that the solvent phase has an important effect in multiple sequential charge transfer mechanisms. All four H⁺/e^– trapping mechanisms fallouts are more notable in water than in PE and gas phases. The surface studies show the most promising sites for the electron withdrawing process.

The Aloe vera contain numerous minerals, vitamins and minerals with emollient, laxative, antibacterial, anti-inflammatory, antioxidant, aphrodisiac, hermetic, antifungal, antiseptic and cosmetic health care values due to the presence of many biologically active constituents. Because of these properties, it is considered necessary to further investigate its medicinal efficacy through chemical and physicochemical studies of extracts in solution. Therefore, in the current research project we aimed to explore the medicinal characteristics/potential of the extract of Aloe vera by studying various solution properties from physicochemical point of view and to explore the interactions of its extract with some biomolecules such as Vitamin C and Deoxyribonucleic acid (DNA). First, the leaves of Aloe Vera plant were collected and then their alcoholic extract was prepared. Then, the extract was studied for its various physicochemical properties in solutions, and its interaction with Ascorbic acid and DNA. These parameters were investigated in solutions by employing density, viscosity, surface tension and UV-Visible spectroscopy etc., measurements at various concentrations and temperatures. For the physicochemical studies of the aqueous solutions of extract, with and without DNA, various concentrations of extract solutions such as 0.5‒5% were used at various temperatures. In case physicochemical measurements, a solution containing 50 µM DNA was used as solvent while the concentration of extract in the mixture was varied. However, the UV-Visible procedure was carried out by maintaining the extract concentration at 1% while altering the DNA concentration in the range of 20‒200 µM. A similar approach was also employed for the interaction study of Ascorbic acid with extract. Based on the outcomes, it may be said that the binding of the extract with DNA and/or Vitamin C be of physicochemical nature and the dominating binding force be of hydrogen bonding between the oxygen/OH groups of the compounds present in the crude plant extract and hydrogen of DNA units.

The extensive use of herbicides such as atrazine and diuron has caused contamination of water sources posing a significant risk to the environment and human. Several methods have been employed in the removal of herbicides from water with adsorption offering a viable and a promising solution due to its relative low cost and environmental friendliness. In this study, the efficacy of Cuscuta japonica powder in removing atrazine and diuron from water was evaluated. Cuscuta japonica powder prepared from Cuscuta japonica vines and characterized using Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, Energy-dispersive X-ray Spectroscopy and Thermogravimetric analysis. Adsorption kinetics of the two herbicides was studied by varying the reaction time while maintaining all other conditions constant. The isothermal studies were done by carrying the adsorption studies at different initial concentrations while the thermodynamic studies were done by monitoring the adsorption process at different temperatures. The herbicides were prepared shortly before use. All the studies were carried in triplicates and blanks were used. Cuscuta japonica powder achieved a maximum percent removal of 85.23 and 79% for atrazine and diuron, respectively. The adsorption capacity of Cuscuta japonica powder for atrazine and diuron were 54.73 and 39.87 mg/g, respectively. The removal efficiency of the two herbicides from water decreased with increase in the molar mass of the herbicides. The adsorption process of atrazine and diuron onto Cuscuta japonica powder followed the Elovich kinetic model, recording R² values of 0.937 and 0.946, respectively, signifying a chemical adsorption process. The adsorption of the two herbicides best fitted the Langmuir isotherm model, with R² values of 0.983 for atrazine and 0.992 for diuron. The thermodynamic results showed that the adsorption process for the two herbicides onto the Cuscuta japonica powder was feasible, spontaneous, and exothermic as shown by negative values for ∆G and ∆H. The negative ∆S values obtained indicate increased order at the sorbent/solution interface during adsorption. This is the first report on the potential of Cuscuta japonica derived adsorbent in removal of pollutants from water. In conclusion, the invasive Cuscuta japonica has a potential application as an adsorbent for the removal of pollutants from water. This may serve as a cost effective way of eliminating this problematic plant.