卷 51, 编号 1 (2017)

The action of 1- to 4-MeV protons on a copolymer of tetrafluoroethylene and hexafluoropropylene (FEP) in a vacuum is accompanied by the release of more than 25 gaseous products and a decrease in its thermal stability. During the course of proton bombardment, the predominant rupture of lateral C–CF₃ bonds with the release of CF₃ particles occurs along with the detachment of fluorine and hydrogen atoms yielding H₂ and HF. Unlike polytetrafluoroethylene, a distinctive feature of the radiolysis of FEP is a decrease by a factor of 5 in the probability of fluorine detachment from the FEP macromolecule by accelerated protons.

Results of targeted modification of the structure and properties of ordered arrays of zinc nanotubes (Zn NTs) by accelerated Xe⁺²² heavy ions with a fluence of 1 × 10⁹ to 5 × 10¹¹ cm^–2 in the energy range of 1.0–1.75 MeV/nucleon are reported. Dynamics of changes in the crystallite shape and orientation of Zn NTs before and after irradiation has been studied by X-ray diffraction. It has been shown that irradiation with accelerated ions has a significant effect on the texture coefficients of Zn NTs. In addition, at a fluence of 1 × 10¹¹ m^–2 or higher, the formation of loose areas in the structure of Zn NTs as a result of partial degradation of the crystal structure and, consequently, a decline in conductivity are observed.

It has been shown that a low fluorescence quantum yield of 2-amino-3-(2′-benzoxazolyl)-quinoline (ABO) and 2-amino-3-(2′-benzothiazolyl)-quinoline (ABT) is due to the relaxation process caused by excited state intramolecular proton transfer (ESIPT). Quantum-chemical calculations have revealed that ESIPT in these compounds is characterized by overcoming a potential barrier, with the lower basicity of the proton-accepting moiety in ABO resulting in a higher barrier than in ABT and, thereby, determining a substantial difference in their fluorescence quantum yields.

It is believed that the accumulation of all-trans-retinal (ATR) in retinal cells is responsible for photoinduced damage to the retina. However, ATR is formed within a photoreceptor cell disk in the process of photolysis and transferred to the cell cytoplasm, where it is converted in a high yield into the nonphototoxic compound retinol. Within the disk where ATR can be accumulated, retinol can form Schiff bases, which are also nonphototoxic compounds, with the amino groups of proteins and lipids. Thus, it is unclear in which concentrations free ATR can be accumulated inside a cell. In this study, it has been proposed to evaluate the concentration of free ATR in the cell from the yield of an excited triplet state because neither Schiff bases nor retinol can be transformed into an excited triplet state. It has been found that 70% ATR forms Schiff bases in the native cell in the equilibrium state, thereby, a considerably decreasing the probability that ATR is the main inducer of photodamage.

A spectral fluorescence study of photoinduced reactions in aqueous solutions has been carried out in order to examine the mechanisms of the oxidation of 5-hydroxy-6-methyluracil (I) in the ground and electronically excited states by molecular oxygen in the presence of copper(II) chloride. It has been found that 5,5,6-trihydroxy-6-methylpyrimidine-2,4-dione (II) is formed upon the photolysis of I. The spectral parameters (λ_max) and the quantum yields (φ) of fluorescence (FL) of compounds I (φ = 8 × 10^–4; λ_max = 362 nm) and II (φ = 17 × 10^–4; λ_max = 306, 330 nm) have been determined. A reaction scheme was proposed, according to which the photooxidation of I occurs through the steps of the generation of the radical cation I^•+ and the superoxide anion О₂^•- with the subsequent formation of 5,5,6-trihydroxy-6-methylpyrimidine-2,4-dione. The catalytic and inhibitory effects of Cu(II) ions on the oxidation of 5-hydroxy-6-methyluracil in the ground and electronically excited states, respectively, by the oxygen radical anion О₂^•- have been revealed.

A CO oxidation catalyst based on β–SiC and Pt nanoparticles has been synthesized and studied. The average size of Pt clusters on the surface of the plasma-chemical silicon carbide nanoparticles is close to 4 nm. It has been found that the rate of the CO oxidation reaction at low concentrations (100 mg/m³) in air at room temperature over the catalyst based on platinum and silicon carbide nanoparticles is 60–90 times that over a platinum black-based catalyst with a specific surface area of 30 m²/g. The Pt/SiC catalyst containing 12 wt % Pt has been found to provide the maximum CO oxidation rate.

The process of plasma-chemical conversion of germanium tetrafluoride in a radiofrequency discharge (13.56 MHz) has been studied. The dependences of the germanium yield on the specific energy input, the H₂/GeF₄ molar ratio, and the total pressure have been measured. The maximum germanium yield is more than 95%. The minimum specific energy consumption at an energy input of 9 MJ/mol is 9.4 MJ/mol or 2.6 kW h/mol Ge. A mechanism of plasma-assisted reduction of germanium tetrafluoride under the given the experimental conditions has been proposed.

A new method is proposed for the synthesis of powdered zinc oxide with the use of a plasma–solution system. The chemical and phase compositions and the morphology of the synthesized powders have been determined. It has been found that the calcination of powders obtained in the plasma–solution system leads to the formation of ZnO.