Theoretical and Experimental Chemistry最新文献

Specific features of the localization of coumarin and xanthene dye molecules in ionic surfactant micelles of sodium n-dodecyl sulphate and cetyltrimethylammonium bromide have been studied by molecular dynamics simulation. It is shown that the change in the microenvironment of a dye molecule in a micelle after its protonation (deprotonation) depends on both the nature of such a dye and the sign of the micelle charge. It was established that the presence of a long hydrocarbon chain in a dye molecule does not prevent its movement during (de)protonation.

Samples of nanocrystalline graphite-like carbon nitride (CGCN) modified with magnesium chloride have been obtained. The synthesized Mg-CGCN samples have been characterized by UV and IR spectroscopies, X-ray diffraction, energy dispersive X-ray analysis, and scanning electron microscopy. It is found that Mg-CGCN exhibits 60% higher photocatalytic activity in the reaction of hydrogen evolution from aqueous ethanol solutions under visible light than undoped CGCN. This may be related to a change in electrophysical characteristics (potentials of allowed bands) resulting from the incorporation of Mg²⁺ ions into the CGCN structure, improved dissociation of photogenerated charges, and inhibition of their recombination.

CoL₃·DMF, [CoCdCl₂L₃]·0.5H₂O, and [CoMnCl₂L₃]·H₂O complexes, where HL is a product of the condensation of o-vanillin and methylamine have been obtained. The crystal structure of the latter complex has been determined by X-ray structural analysis. The study of the antioxidant activity of these complexes in a model reaction of radical-chain oxidation of benzyl alcohol with an atmospheric oxygen has proved a significant inhibition of this process at concentrations of the complexes of 10^–7-10^–6 mol/L. It is established that the inhibitory activity of the compounds depends on the nature of the metal ions present in the complex.

Foam-like binary Cu₂O/Ag₂O nanoheterostructures have been obtained by an electrochemical method. Their photoelectrochemical and spectral properties have been studied. The photocatalytic properties of these composites in the process of gas-phase reduction of carbon dioxide with water vapor have been studied. The formation of binary nanoheterostructures leads to an increase in methane yield and an increase in the amount of other organic products (acetaldehyde, ethylene, and ethanol) while the system is irradiated with visible light when compared to Cu₂O. This effect can be explained by the formation of a nanostructured Cu₂O/Ag₂O binary composite with a mutually consistent energy profile.

Nanosized TiO₂/ZrO₂=1:1 composites have been obtained by mechanochemical, ultrasonic, and coprecipitation methods. It is shown that mechanochemical and ultrasonic treatments of a TiO₂ and ZrO₂ mixture lead to size reduction of oxide particles, changes in X-ray diffraction spectra, the formation of a mesoporous structure of TiO₂/ZrO₂ samples, and an increase in their photocatalytic activity in the reaction of Gesagard (prometryn) herbicide destruction in an aqueous medium when compared to a mechanical TiO₂ and ZrO₂ mixture. It is found that the sample obtained by coprecipitation is X-ray amorphous with a well-developed surface, however, it is significantly inferior to samples obtained by alternative methods in terms of photoactivity.

The electronic and spatial structure of 3,4-ethylenedioxythiophene oligomer containing 12 units (E12) in 0, +1, +2, +3, and +4 charge states has been calculated by the method of density functional theory (B3LYP 6-31 G**). It is shown that electron conductivity in the oxidized oligomer E12⁴⁺ is provided by two bipolarons at the ends of the chain.

The peculiarities of propane dehydrogenation with carbon dioxide over zeolite catalysts of different structural types, in particular, BEA with incorporated Zn, Ga (Ta, Nb) heteroelements have been analyzed. The role of CO₂ as an oxidant, the effect of acid–base characteristics on propylene selectivity and yield, the stability of catalyst operation, and the routes of activation of reagents on acid–base sites of the surface are considered.

A comparative study of electrochemical properties of mono- and few-layer samples of nitrogen-doped graphene as nanosized sensor materials for the qualitative and quantitative determination of dopamine and uric acid has been performed. It is found that the few-layer graphene (NGr(f)) is characterized by high sensibility to dopamine, while monolayer one (NGr(m)) is characterized by high sensibility to uric acid in presence of considerable concentrations of ascorbic acid. XPS results show that the nitrogen content is 8.3 at.% in NGr(f) and 6.2 at.% in NGr(m). The analysis of Raman spectra allows to establish, that NGr(f) and NGr(m) have a defective structure. NGr(f) is characterized mainly by edge defects, while NGr(m) is characterized by vacancies, what obviously predetermines the differences in electrochemical properties of these materials.

A method of synthesis of oligomeric siloxane protic ionic liquids capable of condensation reactions has been developed as starting compounds in the obtaining proton exchange membranes for fuel cells. Their organic frame is characterized by a combination of amine centers of different basicity (aliphatic and imidazole types) neutralized with ethanesulfonic acid and secondary hydroxyl groups. A change in the degree of neutralization of the amine centers significantly affects the structure of the compounds and the mechanism of proton migration. The conductivity of the obtained compounds reaches 9.8·10^–4 S/cm at 100°C in the absence of moisture.

Effective catalysts of CO₂ hydrogenation towards methane were obtained by impregnation of aluminum oxide with cobalt and iron nitrates. The catalysts have been characterized by XRD, SEM-EDX, argon physisorption, and TPD with mass-spectroscopy analysis. It is shown that an increase in the amount of applied Co-Fe active mass in the composition of a nanocomposite catalyst leads to an increase in the CO₂ conversion and CH₄ yield.