


Vol 42, No 1 (2023)
Kinetics and mechanism of chemical reactions, catalysis
Electrically Enhanced Catalytic Activity of Gold Nanocoatings in Carbon Monoxide Oxidation
Abstract
Measurements are reported of the increase in catalytic CO oxidation rate on gold nanocoatings obtained by applying a positive or negative electrical voltage of variable magnitude to a coating. In experiments on an initial mixture of 1.8% СО + 10.2% О2 + Ar and a coating with a starting particle size of 0.2 to 3 nm, conducted at 430°C and atmospheric pressure, the extent of the CO oxidation rate enhancement caused by a stepwise increase in the applied positive voltage initially amounts to 28% at +10 V and then declines to 20% at +30 V. Applying a negative voltage has a weaker effect: after an initial increase by 12% at –10 V, the extent of the enhancement of the CO oxidation rate declines to 7% at –30 V. Quantum chemical calculations are performed to determine the heats of association for CO and O2 with the simplest electrically neutral or electrically charged Au3 cluster, as well as the heats of the reaction for Au3CO + O → Au3CO2 and Au3CO2 → Au3 + CO2 involving differently charged Au3 complexes. Based on the calculated results, an explanation is proposed for the increased catalytic CO oxidation rate on electrically charged gold nanocoatings.



Kinetics of Thermal Decomposition of 1,1-Bis(Methoxy-NNO-Azoxy)-3-Nitro-3-Azabutane
Abstract
The thermal decomposition of 1,1-bis(methoxy-NNO-azoxy)-3-nitro-3-azabutane is studied under isothermal and nonisothermal conditions. The heats of its melting and thermal decomposition are 29.1 kJ/mol (7.0 kcal/mol) and 387 kJ/mol (92.5 kcal/mol), respectively. The composition of gaseous products of thermal decomposition is analyzed. The reaction takes place autocatalytically. The reaction center in the molecule of the studied substance is the diazene oxide group. The mechanism of the process is proposed. The limiting stage of the reaction includes a five-membered cyclic transition state.



Электрические и магнитные свойства материалов
Electrophysical Properties of Binary Carbon Nanocomposites
Abstract
The electrophysical properties of powders of carbon hybrid nanosized composites are studied depending on the content of single-wall carbon nanotubes (CNTs) and thermally reduced graphite oxide (TRGO). The effect of the bicomponent composition of the hybrid material is studied and the results of measurements of the specific low-frequency electrical conductivity at a frequency of 1 kHz, complex dielectric permittivity, and conductivity at a frequency of 9.8 GHz for the powders given above are presented. The effect of γ-irradiation on the measured characteristics of the powders is revealed. Research is aimed at finding fillers for modern effective composite radio-absorbing materials.



Chemical physics of biological processes
Effect of an Ultralow Dose Effect of the Antioxidant Resveratrol Under the Influence of Heat Stress Factor on the Membrane Structure of the Mitochondria Isolated from the Pisum sativum L. Pea Germ
Abstract
The effect of the antioxidant resveratrol on the structure of mitochondrial membranes isolated from Pisum sativum L. pea germ exposed to a heat stress factor is studied. The temperature dependence of microviscosity is used as the structural characteristics of the membranes. The microviscosity is determined by the method of electron spin resonance (ESR). Heat stress leads to a decrease in the crystallinity of mitochondrial membranes. It is shown that ultralow doses (ULDs) of resveratrol restore the structure of the lipid bilayer of the mitochondria after exposure to heat stress (HS) to a state similar to intact plants.



Structural Groups of Natural Phospholipids Taking Part in Complexation with Flavonoids
Abstract
The parameters of the UV spectra of quercetin, dihydroquercetin, genistein, preparations of natural phospholipids (PLs), and mixtures of flavonoids with PLs in chloroform are determined by mathematical processing of these spectra using the Gauss method. It is shown that the position of the maximum of band II in the UV spectra of the studied flavonoids does not depend on the nature of the solvent, and the dependence of the optical density of bands II and I in solutions of these flavonoids on their concentration obeys the Bouguer–Lambert–Beer law. It is found that the parameters of the UV spectra of natural lipids significantly depend on the polarity of the solvent and the composition of PLs. Using genistein as an example, it is shown that the flavonoid interacts with the conjugated double bonds of fatty acids of PLs and nitrogen- and phosphorus-containing groups of PLs also participate in the formation of complexes.



Chemical physics of polymeric materials
Effect of Water on the Structure of Polyethylene–Polylactide Binary Blends and Polyethylene–Polylactide–Aged Polyethylene Ternary Blends
Abstract
The effect of water on double and triple polyethylene (PE)–polylactide (PLA) blends of various compositions, including those with the addition of aged polyethylene as an analog of recycled polymer is studied in this paper. It is established that the composition of the blends directly affects its characteristics, especially when exposed to water as an aggressive factor. PE–PLA composites have a maximum degree of water absorption of about 7.5%, and in the presence of the third component, oxidized polyethylene in the amount of 40 and 50 wt %, the degree of water absorption increases to 10%. It is shown by IR spectroscopy that after the action of water, structural elements belonging to PLA are destroyed, which is due to the more active interaction of water molecules with PLA molecules, while the characteristics of the polyethylene matrix remain practically unchanged.



Structural Features of Polylactide Films Obtained from a Melt and Solution
Abstract
The morphology and structure of polylactide film samples obtained from a melt and from a solution in chloroform are studied. The crystallization process of polylactide takes place under nonisothermal conditions. It is determined that the melting and crystallization points of the polylactide sample obtained from the solution are, respectively, 2 and 4°C lower than the sample obtained from the melt. Using optical polarization microscopy, it is shown that the sample obtained from the solution has a spherulite structure, while spherulites are not detected in the polylactide sample obtained from the melt. The X-ray diffraction patterns of the polylactide samples crystallized from the solution and melt are different. Well-defined reflexes characteristic of the crystalline modification of the α-form are recorded on the diffractogram of the sample obtained from the solution. The pressed polylactide sample has an initially X-ray amorphous structure, which partially transforms into a crystalline structure during annealing for 60 min at 90°C. X-ray diffraction analysis revealed differences in the degree of crystallinity over the thickness of the polylactide sample obtained from the solution.



Technological Parameters of Epoxypolysulphone Binders Modified with Furfuryl Glycidyl Ether
Abstract
An epoxy polysulfone binder modified with an active diluent, furfuryl glycidyl ether (FGE), is studied. The addition of FGE significantly improves the technological parameters of the high-viscosity binder. The processing temperature of modified binders varies in the range of 80 to 120°C depending on the FGE concentration. The phase decomposition of the binder during its preparation is not observed, but occurred during curing. The glass transition temperature of matrices based on the obtained binder remains at a high level: 100–107°С. The type of phase structure formed during the curing of the hybrid binder depends on the concentration of FGE and polysulfone PSK-1.



Structural and Mechanical Properties of Hydrogels Based on Polyelectrolyte Complexes of N-Succinyl-Chitosan with Poly-N,N-Diallyl-N,N-Dimethylammonium Chloride
Abstract
This article studies the structural and mechanical properties of polymer hydrogels based on polyelectrolyte complexes of N-succinyl-chitosan (NSC) with poly-N,N-diallyl-N,N-dimethylammonium chloride, depending on the composition of the reaction mixture and the conditions for obtaining complexes. The types of intermolecular interaction between the components of the complexes are studied by IR spectroscopy. The causes of swelling of coacervates based on polyelectrolyte complexes of N-succinylchitosan-chitosan with poly-N,N-diallyl-N,N-dimethylammonium chloride are analyzed. The relationship between the composition of coacervates and the structural-mechanical and transport properties of the gels formed from them is established. The developed approach to create elastic-viscous systems can be implemented when creating gel-like polymeric materials capable of self-organization into systems with controlled characteristics of the structure.



ХИМИЧЕСКАЯ ФИЗИКА НАНОМАТЕРИАЛОВ
Interaction of Gold Nanoparticles with Cyanine Dyes in Cholesteric DNA Submicroparticles: Impact of the Way of Their Introduction into the System
Abstract
The results of two different ways of introducing SYBR Green I (SG) and PicoGreen (PG) cyanine dyes, as well as ultrasmall gold nanoparticles (GNPs) in a cholesteric liquid-crystalline dispersion (CLCD) of DNA, are compared: preliminary incubation with DNA and introduction in a ready-made dispersed system. In the absence of dyes and in the presence of SG, the preliminary incubation of GNPs in a DNA solution leads to an increase in the destruction of its cholesteric phase. At the same time, more efficient quenching of SG fluorescence was observed upon the injection of GNPs in a ready-made dispersed system. For the case of PG, the order of introduction of the components does not affect either the properties of the DNA CLCD or the fluorescence of the dye.



Химическая физика атмосферных явлений
Modeling the Time-Dependent O3 Uptake on a Methane Flame Soot Coating Under Conditions of Competitive O3/NO2 and O3/N2O5 Adsorption
Abstract
The uptake of O3 (1 × 1012–5× 1013 cm−3) on a methane soot coating preliminarily exposed to N2O5, is studied using a flow reactor with a movable insert. Based on the dependence of the ozone uptake coefficient on the exposure time and O3 concentration, the uptake mechanism is established and a number of elementary parameters are obtained that describe the uptake process at arbitrary O3 concentrations. Based on the Langmuir representation of adsorption, a model description of the uptake on soot under conditions of the competitive adsorption of O3/NOx, where NOx = NO2 and N2O5, taking into account the multistage uptake process, is proposed. Based on the developed model and elementary parameters describing the uptake of O3, NO2, and N2O5 on a fresh soot surface, as well as the uptake of ozone on a surface pretreated with NO2 and N2O5, numerical estimates were made of the additional contributions to the ozone uptake for two real scenarios of the O3/NOx ratio. For an industrial region in winter, when the ozone concentration is minimal (10 ppb O3, 17 ppb NO2, and 4 ppb N2O5), the additional integral contribution to the uptake of O3 on the reaction products of NO2 with soot is 68%, and in the case of N2O5, it is 3.6%. For the same region in summer, at the maximum ozone concentration (36 ppb O3, 17 ppb NO2, and 4 ppb N2O5), the analogous contributions will be 20 and 1%, respectively. The reasons for this difference are discussed.



Biologically Active UV Radiation in the 21st Century
Abstract
Data on the ozone content in June and January of 1980 and 2100 obtained using the SOCRATES two-dimensional interactive model of the average atmosphere are presented. Based on these data, using the Fast simulation of downward UV doses, indices and irradiances at the Earth’s surface program developed at the Norwegian Institute for Atmospheric Research, the change in the main factors of biologically active solar radiation by the end of the 21st century, including data related to the formation of erythema and vitamin D in humans, is calculated. It is shown that the parameters of biologically active radiation by the end of the 21st century may change compared to 1980; however, this will not pose a significant threat to human health.



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