Vol 57, No 4 (2023)

The processes of freezing of water droplets sitting on a substrate after exposure to nanosecond spark discharges have been experimentally studied. It has been found that the droplets subjected to spark discharge treatment freeze much earlier than those unexposed to discharges. The analogy of the observed processes with the well-known Mpemba effect is noted. A qualitative explanation is given for the observed effect: rapid freezing is due to hydrated electrons, which are formed upon contact of water with plasma and play the role
of crystallization centers

Long-term field studies of the effect of presowing seed treatment of spring wheat (Triticum aestivum L.) with XeCl-excilamp UVB radiation on sowing qualities of seeds and plant productivity have been carried out. The features of morphogenesis at various stages of growth and development of wheat plants have been determined. A subdose of exposure has been identified that increases the crop yield. The studies prove the prospects of introducing UVB treatment into the pool of modern agricultural technologies.

High-spin products of photolysis of 1,3,5-triazido-2,4,6-trichlorobenzene in a 2-methyltetrahydrofuran solution frozen at 6 K has been studied using EPR spectroscopy in combination with quantumchemical calculations. It has been found that the photolysis of this triazide leads to the formation of a mixture of triplet 1,3-diazido-2,4,6-trichlorophenyl-5-nitrene, quintet 1-azido-2,4,6-trichlorophenyl-3,5-dinitrene, and septet 2,4,6-trichlorophenyl-1,3,5-trinitrene. The solvent effect on the EPR spectra and the magnetic
characteristics of nitrenes has been studied.

The possibility of using semiconductor nanocrystals in photodetectors for optical detection of open flame has been explored. The spectral range boundaries of response of flame detectors have been concretized. In accordance with this, colloidal lead sulfide nanocrystals absorbing in the range of 1–1.5 μm have been synthesized. Photoresistors with different ligand compositions have been made from these particles. For the obtained samples, the current–voltage characteristics were measured and the photosensitivity and specific
detectivity parameters were calculated. A theoretical estimate of the flame detection range has been made for the samples. It has been shown that a photosignal can be reliably detected at a distance of more than 80 m.

Carbon monoxide oxidation catalysts comprising Pt clusters on titanium dioxide with an oxide particle size of 6 and 20 nm have been synthesized. The catalysts have been studied using TEM, XRD, and XPS techniques, and it has been found that platinum clusters coated with a mixture of platinum oxides are formed on the support surface. The coherent scattering region of the Pt cluster is close to 5–6 nm for the studied oxide supports. The catalytic properties in the CO oxidation reaction at 295 K and low CO concentrations
(less than 100 mg/m3) have been examined. The catalyst based on titania with a particle size of 20 nm and a platinum loading of 10 wt % has been found to have the CO oxidation rate 100 times higher than that on platinum black with a specific surface area of 30 m2/g. The catalysts are promising for use in catalytic air purification systems.

The influence of the dose of presowing γ-irradiation of tubers on the anatomical and morphological structure, yield, and tasting properties of potatoes of the Meteor variety has been studied. Morphological disorders—beak-shaped and heart-shaped tubers of a large fraction and small tubers in the form of embryos—were found in potatoes grown from tubers irradiated with doses of 500–600 Gy, although no external anatomical and morphological differences were noted in the stems and leaves of potato plants in the course of the vegetative development regardless of the presowing irradiation dose of tubers. Irradiation of seed tubers with doses of 200–300 Gy led to the highest yield and profitability and the best tasting qualities of grown potatoes. Experiments on the toxicity of potato tubers irradiated with doses of 100–1500 kGy and juice released during their radiolysis with doses of 1200–5000 kGy showed no negative effect on the animals that consumed them. At the same time, the physiological processes of digestion, excretion, and metabolism in experimental animals were not inhibited and the level of glucose in their blood remained within physiological reference values. The experimentally established highest doses of γ-irradiation of potatoes and the doses of introducing aqueous dispersions of the irradiated products into mice (gram of substance per 1 kg of live weight of the animal) that did not cause clinical manifestations were 10 g/kg for powdered potato tubers irradiated with a dose of 1500 kGy and 20 g/kg for dried juice powder released in the course of irradiation of potato tubers with a dose of 2000 kGy.

This article considers physicochemical changes in the composition of potato tubers gamma-irradiated to doses of 5000 kGy, as studied by Fourier transform IR spectroscopy. Functional groups in the powders of skin, pulp, and juice of irradiated tubers have been examined. The carbonization and radiationinduced oxidation of the molecules of tuber constituents have been established. At doses above 1000 kGy, the hardness of tubers was completely lost, the integrity of the skin surface was violated, and an intense release of
juice began. It has been found that γ-radiolysis at a dose to 5000 kGy does not lead to the complete destruction of chemical bonds in the structure of the main compounds contained in potato tubers.

The oxidative and nonoxidative conversion of ethylene in a dielectric barrier discharge in the presence of water with the formation of predominantly unsaturated compounds (acetylene, butene, butadiene) has been studied. The efficiency of ethylene conversion in argon is shown in comparison with its oxidation by air into oxygenates. A simple theoretical estimate of the energy loss of discharge electrons in the feed gas mixture and simple kinetic calculations make it possible to explain both the change in the degree of ethylene conversion and the direction of the process

The nitration of phenol with plasma-activated water (PAW) generated by pulsed radiation of an electric spark discharge has been studied. Long-lived nitrogen-containing active species that accumulate in water during treatment are nitrous acid and the …ONOOH/ONOO− complex, which decomposes into peroxynitrite and peroxynitrous acid. Their concentration in PAW after 10 min of treatment was ~10−3 mol/L. When PAW is mixed with phenol in a 1 : 1 ratio, the identified reaction product is 4-nitrophenol. The yield
of nitration through PAW is equal to the nitration yield by the direct action of hot plasma radiation on a phenol solution.

A facility for conducting experiments on the microwave (MW) pyrolysis of peat at a source operating frequency of 2.45 GHz has been developed. The MW pyrolysis of peat for the production of low-molecular-weight organic components has been experimentally studied. The products of peat MW radiationinduced decomposition were determined, and reaction schemes for the degradation of peat components were proposed. A carbonaceous residue with relative carbon, hydrogen, nitrogen, and sulfur contents of 83–85, 4–5, 2–3, and <0.3 wt %, respectively, was obtained.