Phase transitions in KNO3 embedded in MCM-41 films with regular nanopores

This paper reports on a comparative study of phase transitions in nanocomposites made up of KNO₃ embedded in 10-μm-thick MCM-41 films with unidirectional pores 4.0 nm in size on an aluminum substrate and of nanocomposites prepared in the form of potassium-nitrate-filled pressed MCM-41 powders with 3.7-nm pores. The temperature dependences of linear permittivity and the amplitude of third harmonic generation have been measured under heating and cooling. The structural transition from phase II to phase I shifts under heating relative to that occurring in bulk KNO₃ toward lower temperatures for potassium nitrate in the film and toward higher temperatures for the pressed MCM-41-based nanocomposite. A significant difference has been observed also within the region of existence of ferroelectric phase III. The data obtained suggest that the shifts of phase transition temperatures observed in the conditions of nanoconfinement are influenced markedly not only by pore size and geometry but also by other factors.     

A capillary gas chromatographic column with a porous layer based on the divinylbenzene-vinylimidazole copolymer

Capillary columns with a new sorbent based on the divinylbenzene-vinylimidazole organic copolymer are proposed. The properties of the prepared columns are discussed. It is demonstrated that columns based on the divinylbenzene-vinylimidazole polymer with different selectivities can be prepared by varying the relative amount of vinylimidazole in the initial polymerization mixture. The examples of separation of light hydrocarbons, permanent gases, and oxygen-containing compounds are given.     

Design,Synthesis and Assay of Novel Methylxanthine–Alkynylmethylamine Derivatives as Acetylcholinesterase Inhibitors

Xanthine derivatives have been a great area of interest for the development of potent bioactive agents. Thirty-eight methylxanthine derivatives as acetylcholinesterase inhibitors (AChE) were designed and synthesized. Suzuki–Miyaura cross-coupling reactions of 8-chlorocaffeine with aryl(hetaryl)boronic acids, the CuAAC reaction of 8-ethynylcaffeine with several azides, and the copper(I) catalyzed one-pot three-component reaction (A³-coupling) of 8-ethynylcaffeine, 1-(prop-2-ynyl)-, or 7-(prop-2-ynyl)-dimethylxanthines with formaldehyde and secondary amines were the main approaches for the synthesis of substituted methylxanthine derivatives (yield 53–96%). The bioactivity of all new compounds was evaluated by Ellman’s method, and the results showed that most of the synthesized compounds displayed good and moderate acetylcholinesterase (AChE) inhibitory activities in vitro. The structure-activity relationships were also discussed. The data revealed that compounds 53, 59, 65, 66, and 69 exhibited the most potent inhibitory activity against AChE with IC₅₀ of 0.25, 0.552, 0.089, 0.746, and 0.121 μM, respectively. The binding conformation and simultaneous interaction modes were further clarified by molecular docking studies.     

Porous-layer capillary gas chromatography columns with a hybrid structured sorbent based on alkyltriethoxysilane

Porous-layer capillary columns with a hybrid organic-inorganic sorbent based on structured silica are described. Properties of the prepared columns are discussed. Examples of separating C₁–C₄ hydrocarbons and a mixture of solvents on the obtained columns are presented. It is shown that changes in the organic component content of the original sol make it possible to control the selectivity of porous-layer columns.     

Solubility of Lead Nitrate in Aqueous Solutions of Nitric Acid and Zinc Nitrate

Solubility of lead nitrate in the system H₂O-Zn(NO₃)₂-HNO₃ was studied using the simplexlattice design method. The equations describing the effect of nitric acid and zinc nitrate concentrations on the content of lead nitrate in solution at 25 and 55°C were derived.     

Effect of the synthesis temperature of porous carbon-metal oxide composites on the gold particle morphology

The state of gold deposited from a chloride solution on the surface of the porous magnetite-carbon composite obtained from modified birch saw dust at 400 and 800°C was studied by electron microscopy, X-ray photoelectron spectroscopy, and XRD analysis. The shape and size of the deposited gold crystallites depend on the synthesis temperature of the composite. The deposited gold crystallites were mainly ray-shaped at the synthesis temperature of 400°C and spheroid at 800°C.