Vol 50, No 3 (2016)

The ultrahigh-resolution mass spectra of a substance P peptide labeled with deuterium have been obtained. The use of an ion trap with dynamic harmonization has made it possible to resolve the hyperfine isotopic structure of peaks and to reliably distinguish the hydrogen isotopes from the isotopes of carbon in the composition of the test molecules. The deuterium–hydrogen exchange reaction of humic acids has been performed in a gas phase, and it has been shown that the resolving power attained is sufficient for reliable interpretation of the results.

A procedure for the bench-test simulation of the physicochemical interactions of polymers with flows of atomic oxygen and vacuum ultraviolet radiation in the ionosphere of the Earth has been developed. The threshold values of the ratios of the vacuum ultraviolet flux density to the flux of atomic oxygen, which characterize the synergistic effect on the ablation of polymers (the polyimides Kapton-H and PM-1E, polyethylene, and Teflon 100A) have been obtained.

Radiothermoluminescence (RTL) curves of mixtures of C20 and C24 n-alkanes have been deconvoluted into the curves of crystalline and disordered regions, and their change depending on the mixture composition has been analyzed. The shape of the total RTL curve of the mixture regardless of the its composition is fundamentally different from that shape of the sum of the curves of the individual components taken in the relevant ratios. The difference becomes noticeable at as low a C20 amount in the mixture as 2% and is manifested in the disappearance of the intense RTL peaks of the individual components and appearance of new intense peaks in temperature intervals other than those of the RTL peaks of the components. It has been shown that these changes correlate with changes of the crystalline structure of the mixture: a new crystalline structure other than the structure of any of the individual components emerges and the mixture becomes amorphous. High selectivity of charge trapping in disordered regions of the mixture has been revealed: the contribution of RTL of the disordered regions to the total curve is many times higher than their volume fraction in the mixture. This selectivity might be due to an increase in concentration of defects in the unordered regions of the mixture in comparison with their concentration in the pure alkanes. These defects are traps for electrons that are accessible to acceptors introduced into the mixture.

A method for fabricating form composite photoanodes based on titanium dioxide and phosphotungstic acid has been developed. The introduction of the polyoxometalate into a porous titanium dioxide layer increases the photoconversion efficiency of dye-sensitized solar cells and affects characteristics such as open-circuit voltage and short-circuit current.

Effect of the solvent nature on the kinetics of photoreduction of substituted benzoquinones in the presence of hydrogen donors has been studied. It has been found that the effective photoreduction rate constant (k_H) for quinones decreases with an increase in solvent polarity. For the 3,6-di-tert-butylbenzoquinone–1,2-N,N-dimethylaniline pair, the dependence of ln k_H on the difference of the reciprocals of optical and static solvent permitivities (1/ε _∞–1/ε₀) is stepwise with a break point corresponding to CH₂Cl₂. A similar relationship lnk_H = f(1/ε _∞–1/ε₀) is observed for the p-chloranil–mesitylene pair. In the study of the photoreduction kinetics for a series of seven o-benzoquinones in the presence of p-derivatives of N,N-dimethylaniline in CH₂Cl₂, it has been found that the dependence of k_H on the free energy of electron transfer (ΔG_e) has a maximum for the 3,6-di-tert-butylquinone-1,2–N,N-dimethylaniline pair at ΔG_e = 0.11 eV.

The kinetics of reduction of Cr(VI) by treating its aqueous solution in atmospheric pressure dc discharge in air has been studied at the discharge current range of 20–80 mA and the concentration range of 1.25–12.5 mg/L. The solution has served as the discharge cathode. It has been shown that the discharge treatment leads to a decrease in the Cr(VI) concentration to its steady-state value, with the latter depending on the discharge current and the initial concentration of the solution. The effective rate constants of the forward and reverse processes have been determined, the energy efficiency of the process has been evaluated, and possible mechanisms of the reactions involved have been discussed.