Vol 52, No 2 (2018)

Spectral and photochemical properties of 1-(9-phehanthryl)-2-(2-quinolyl)ethylene (9Ph2QE) in neutral and protonated forms have been investigated. It has been found that both isomers of 9Ph2QE are photoactive. The quantum yield of trans–cis photoisomerization (ϕ_tc = 0.47) in the neutral form is typical of the diabatic photoisomerization; on passing to the protonated form, ϕ_tc increases up to 0.70. Thus, the double annelation of the 2-styrylquinoline phenyl group to form 9Ph2QE makes it possible to conserve the α-effect, which consists in an increase in the quantum yield to ϕ_tc > 0.5 on passing from the neutral to protonated form, whereas the effect disappears for other types of annelation (naphthylquinolylethylenes, 1-(9-anthryl)-2-(2-quinolyl)ethylene).

Thionine (ThH⁺) molecules form monomeric ThH⁺@CB7 (1: 1) and dimeric 2ThH⁺@CB8 (2: 1) complexes with cucurbit[7,8]urils (CB7) and (CB8) in water. Unlike the case free ThH⁺ molecules, the absorption spectrum of the complexes is characterized by a hypsochromic shift of the maximum by 6 and 41 nm for ThH⁺@CB7 and 2ThH⁺@CB8, respectively. The ThH⁺@CB7 complexes exhibit fluorescence, unlike the nonfluorescing 2ThH⁺@CB8 complexes. The monomeric complexes undergo intersystem crossing to the triplet state with a lifetime of 14 μs. The dimeric complexes have a very low quantum yield of the triplet state. The triplet state of the dimeric complexes was populated by photosensitized excitation by triplet–triplet energy transfer. The lifetime of the triplet state is ≈50 μs.

The effect of photo-and thermoactivation of the CdSe cores of colloidal quantum dots (CQDs) on the luminescent properties of the CdSe@CdS CQDs formed on them has been studied. It has been established that an optimum combination of the action of UV light and heat on the CdSe cores has a favorable effect on the luminescent characteristics of the CdSe@CdS CQDs formed on them, noticeably increasing the quantum yield of luminescence, narrowing the spectral emission band, and enhancing their stability.

The molecular–topological structure of polyamide before and after γ-irradiation has been first studied by thermomechanical spectrometry. The γ-irradiation with a dose up to 300 kGy does not change the topological structure of the polymer, the four-block pseudo-network structure of which contains crystalline segments of macromolecules and polyassociative entities of the cluster type in addition to low-and high-temperature amorphous blocks. During irradiation, only interblock mass transfer of the chain segments occurs, resulting in different dose-dependent values for the molecular weight of the chains, their weight fraction in each topological block, and the glass transition and molecular flow temperatures of the polymer. Radiothermoluminescence curves exhibit three maxima at 152, 200, and 330 K, of which the last one is detected in a temperature region close to the glass transition temperature of the high-temperature amorphous block on the thermomechanical analysis curve of the polymer.

The influence of γ-radiation on the structural and conducting properties of copper nanotubes, obtained by electrochemical synthesis in pores of on polyethylene terephthalate-based template matrices, has been studied. With the use of scanning electron microscopy, X-ray diffraction analysis, and electron diffraction analysis, it has been established that irradiation with γ-rays at doses of 50 and 100 kGy makes it possible to modify the crystal structure of the nanotubes, increasing their conductivity and decreasing the resistance of the nanosized entities without destroying their structure.

Ternary host–guest complexes have been first obtained from cucurbituril CB[8] as a host molecule and two guest molecules: nitroxyl probes of different structures and biologically important amino acids (AA) and aromatic compounds. To characterize the binding of the guests, parameters of the polarity of the environment and the rotational mobility of the spin probes have been used. These parameters have been shown to depend on the nature of the analytes. For the ternary complexes, in addition to the usual triplet ESR spectra from nitroxyl probes (S3), supramolecular ensembles consisting of three equivalent ternary complexes (“triads”) have been found, whose ESR spectra have a seven-component hyperfine structure (S7) due to delocalization of the unpaired electron over three nitrogen nuclei. The relative intensity of the S7 spectra increases with increasing NaCl concentration in the solution, and also depends significantly on the nature of the analyte and the spin probe. Quantum chemical calculations have shown that (1) to determine the stability of the complexes, it is necessary to allow for the van der Waals interaction, and (2) the complexes involving the zwitterionic form of AA are much more stable than those with the neutral form of AA.

A method is proposed for the simulation of chemical kinetics in a dielectric barrier discharge (DBD) with the use of an effective rate constant of electron–molecule reaction and a simple expression for its estimation. The results of the simulation of the kinetics of methane conversion in DBD in the presence of water are presented.

The effect of dielectric-barrier discharge plasma treatment on the valence state of metal ions in aqueous solutions of manganese, iron, cobalt, and nickel (Mn, Fe, Co, Ni) salts has been studied. The efficiency of recovery of sparingly soluble compounds of transition metals during the treatment of model solutions in a plasma reactor designed by the authors has been evaluated. The possibility of hydrogen peroxide formation in water by barrier discharge treatment has been shown, and the change in the redox potential of the system has been analyzed.