Vol 51, No 4 (2017)

Photochemical transformations induced by long-term continuous exposure to light have been studied. Using the developed theory and methods for calculating photochemical processes, computer experiments have been performed and their results have been analyzed for a large number of model systems and particular reactions. The excitation process has been considered in an explicit form, and the population of energy levels in excited states by absorption of light quanta has been taken into account. It has been shown that continuous optical excitation qualitatively changes the situation in comparison with pulsed excitation: the quantum yield is not zero even at very low quantum beat frequencies. For fast reactions, the kinetics of the process is exponential; in the case of slow reactions, concentration oscillations (on the order of 25% or more) arise, which are clearly manifested in the stationary state of the molecular system. The choice of the optimal photoirradiation time is an important factor in experimental design aimed to obtain a desired amount of the product. Molecular modeling makes it possible to a priori evaluate this quantity.

The quantum yield of the photolysis of 2-mercaptobenzothiazole (MBT) in the molecular form increases by a factor of 20 in the presence of the surfactants cetyltrimethylammonium bromide (CTAB) and cetylpyridinium chloride (CPCl) in comparison with aqueous solution. In the photolysis of the MBT ionic form, the quantum yield does not change in the presence of CTAB and decreases in the presence of CPCl. The maximums of the MBT absorption spectra shift with an increase in the surfactant concentration for both the molecular and ionic forms. Simultaneously, the MBT photolysis quantum yield increases. It has been shown that the quantum yield of MBT photolysis in water increases in the presence of compounds containing heavy atoms.

Lipid bilayers immobilized on highly porous silica gel monoliths (SLBs) have been proposed as templates for chemosensors. Procedures for preparation and characterization of SLBs have been developed and applied. Rotational dynamics and orientational ordering at different depths in a SLB membrane and, for comparison, in bilayer liposomes have been studied for the first time using n-PC phospholipid spin labels.

A graphene oxide aerogel synthesized from graphene oxide hydrogel and graphene aerogels have been synthesized using the sol−gel method by reducing a suspension of graphene oxide with various reducing agents: a mixture of hypophosphorous acid and iodine, L-ascorbic acid, sodium metabisulfite, and by hydrothermal treatment. The obtained aerogels have been studied by scanning electron microscopy, IR spectroscopy, Raman spectroscopy, X-ray powder diffraction, and X-ray photoelectron spectroscopy. Comparative studies of graphene aerogels have shown that their properties, namely density, specific surface area, reduction degree, surface morphology, defectiveness of graphene sheets, interlayer spacing, average sizes of coherent scattering regions, number of layers, and crystallite size in the basal plane in graphene crystallites depend on the method of synthesis.

Radical polymerization of tetrafluoroethylene (TFE) in solutions of trimethoxysilanes leads to the formation of fluoroalkoxysilane oligomers and the products of their subsequent hydrolysis and dimerization that occur when methoxyl groups are replaced by hydroxyl groups and Si–O–Si links to bind the oligomers are subsequently formed. The chain length of the oligomers increases with the initial TFE concentration, thereby leading to the formation of colloidal solutions. Colloid particles contain oligomers and solvent molecules, the number of which per TFE unit decreases as the chain length grows to 4–6. Partial replacement of the starting solvents, which are also capable of creating a silicone skeleton during polycondensation, makes it possible to control the number of fluoroalkyl chains attached to this skeleton.

The absolute values of the rate constants for heterogeneous recombination of chlorine atoms on the surface of aluminum and copper in the positive column of a glow discharge in Cl₂ have been determined using the pulse relaxation technique.

The literature on the modification of polylactide by high-energy chemistry methods including low-temperature plasma treatment, laser and electron-beam irradiation, bombardment with high-energy ions, and γ-irradiation has been surveyed. The main procedures for polylactide treatment by plasma, facilities used in these processes, and instrumental methods for the characterization of changes in the chemical structure and properties of the polymer have been described. Data on the application of polylactide modified by high energy chemistry methods and materials on its basis in medicine and biotechnology are presented.