Volume 42, Nº 1 (2023)

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.

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.

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.

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.

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.

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.

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.