Mechanochemical interaction of alkali metal metasilicates with carbon dioxide: 1. Absorption of CO<Subscript>2</Subscript> and phase formation

Processes proceeding during the mechanochemical activation of alkali metal metasilicates M₂SiO₃ (where M is Li, Na, K) are studied in the air and in an atmosphere of carbon dioxide. At the initial stage of activation in a centrifugal planetary mill in an atmosphere of carbon dioxide, the main portion of supplied mechanical energy is expended for grinding and the mechanosorption of CO₂ occurs in the regime of cleavage, i.e., on the freshly formed surfaces of particles. As the time of activation increases, the specific surface area becomes constant, which, however, does not substantially affect the rate of interaction between carbon dioxide and silicates. The absorption of CO₂ occurs in the regime of friction on the active sites of already formed surfaces and is accompanied by the tribodiffusion of gas molecules into structurally disordered layers of particles. With identical amounts of supplied energy, the CO₂/M₂SiO₃ molar ratio in the samples activated in the medium of carbon dioxide increases in the Li < Na < K series. The main product of mechanically induced interactions between Li₂SiO₃ and CO₂ is the X-ray amorphous carbonate-silicate phase. In the case of sodium and potassium metasilicates, the reaction of mechanochemical substitution occurs to form corresponding carbonates, hydrocarbonates, and amorphous silica. It is shown that the character of mechanochemical interaction between M₂SiO₃ and CO₂ depends on the change in the Gibbs energy of the transformation of silicate into corresponding carbonate, as well as on the melting temperature and the hygroscopicity of silicate.     

Effect of hydroacoustic treatment on the state of aqueous solutions of sodium alginate

Effect of a hydroacoustic treatment in a rotary-pulsed apparatus on the properties of sodium alginate solutions: dynamic viscosity, intrinsic viscosity, surface tension, and optical density, was studied. The contribution of the mechanical degradation of macromolecules to the observed decrease in the viscosity of alginate solutions was determined. The effect of the ionic strength of the solutions on their stability against hydroacoustic degradation was analyzed.     

Computational study of structure,electronic, and microscopic charge transport properties of small conjugated diketopyrrolopyrrole‐thiophene molecules

π‐Conjugated small molecules containing diketopyrrolopyrrole (DPP) and thiophene moieties represent a modern class of functional materials that exhibit promising charge transport properties and therefore have great potential as building blocks of active elements of electronic devices. As a starting point of this computational study, the molecular structure, electronic characteristics, and reorganization energies associated with electron or hole transfer are considered. Prediction of molecular crystal packing is followed by the calculation of couplings between adjacent molecules and detection of the effective charge transfer pathways. Finally, the rates of charge transfer process are evaluated. The obtained results shed light not only on the properties of materials containing low‐molecular species but also serve as a benchmark for further classical force‐field simulations of DPP‐based polymers.     

Synthesis of homogeneously mg-doped lithium niobate batch and study of the effect of non-metal impurities on the properties of LiNbO<Subscript>3</Subscript>:Mg crystals

The preparation conditions for the homogeneously doped precursor Nb₂O₅:Mg for the synthesis of granulated lithium niobate batch was studied. The effect of non-metallic impurities in the Nb₂O₅:Mg precursors and the lithium niobate batch on the characteristics of the melt–crystal system and the physicochemical and optical characteristics of the LiNbO₃:Mg crystals was established.     

Structure of Cs<Subscript>4</Subscript>(HSO<Subscript>4</Subscript>)<Subscript>3</Subscript>(H<Subscript>2</Subscript>PO<Subscript>4</Subscript>) single crystals

Single crystals of Cs₄(HSO₄)₃(H₂PO₄) are synthesized and studied for the first time. The new compound is found in the course of studies of the phase diagram of the CsHSO₄–CsH₂PO₄–H₂O triple system. Data on the atomic crystal structure of single-crystalline and powder specimens, as well as on structural phase transitions, are obtained.     

New crystals of the CsHSO<Subscript>4</Subscript>–CsH<Subscript>2</Subscript>PO<Subscript>4</Subscript>–H<Subscript>2</Subscript>O system

Cs₆H(HSO₄)₃(H₂PO₄)₄ crystals, grown for the first time based on an analysis of the phase diagram of the CsHSO₄–CsH₂PO₄–H₂O ternary system, have been investigated by structural analysis using synchrotron radiation. The atomic structure of the crystals is determined and its specific features are analyzed.     

Production of complex rubidium and cesium hydrogen sulfate‒phosphates

The solubility in the CsH₂PO₄?CsHSO₄?H₂O system at different temperatures (25, 50, and 75°C) is studied and the phase equilibria in the Rb₃H(SO₄)₂?RbH₂PO₄?H₂O system under isothermal conditions (at 25°C) are analyzed. The temperature and concentration conditions for forming Rb₂(HSO₄)(H₂PO₄), Rb₄(HSO₄)₃(H₂PO₄), Cs₄(HSO₄)₃(H₂PO₄), Cs₃(HSO₄)₂(H₂PO₄), Cs₂(HSO₄)(H₂PO₄), and Cs₆H(HSO₄)₃(H₂PO₄)₄ compounds (the latter has been obtained for the first time) are determined. The conditions for growing large single crystals of complex acid rubidium and cesium salts are found.     

3-nitro- and 3-bromo-3-nitroacrylates in reactions with phenyl azide

1,3-Dipolar cycloaddition of alkyl 3-nitro-and 3-bromo-3-nitroacrylates to phenyl azide gives regioisomeric alkyl 5(4)-nitro-1-phenyl-4,5-dihydro-1H-1,2,3-triazole-4(5)-carboxylates, the corresponding triazoles both with and without nitro group, and alkyl 3-nitro-1-phenylaziridine-2-carboxylates. Nitrotriazolecarboxylates were found to lose the ester moiety during chromatographic separation of the products on aluminum oxide. The structure of the products was determined on the basis of IR, ¹H NMR, and X-ray diffraction data.     

<Emphasis Type="Italic">N,N′</Emphasis>-Bis(9-anthrylmethyl)diamines as fluorescent chemosensors for transition metal cations

N,N′-Bis(9-anthryl)-substituted diamines, imidazolidines, and hexahydropyrimidines were synthesized, and their luminescence properties and complexing ability were studied. N,N′-Bis(9-anthrylmethyl)ethane-1,2-diamine and N,N′-bis(9-anthrylmethyl)butane-1,4-diamine were found to be effective and selective PET chemosensors for Zn²⁺ and H⁺, respectively. 2-[1,3-Bis(9-anthrylmethyl)hexahydropyrimidin-2-yl]-6-methoxyphenol can be used as fluorescent chemosensor for mercury(II) cations.     

Light-induced transformation of C60 films in the presence and absence of oxygen

The composition and structure of C₆₀ fullerite films prepared by discrete evaporation in quasiclosed volume, as well as their changes induced by laser irradiation, have been studied by ellipsometry and Rutherford backscattering. The starting film has a 150-Å thick stable top layer and a carbon to oxygen ratio of 10:1. Exposure of a film both to vacuum and to air results in formation of an insoluble photo-transformed phase, but in the second case the change in the refractive index implies the appearance of compounds with oxygen. The material does not undergo complete polymerization, although all structural changes cease at an irradiation dose of 10₄ photons per fullerene molecule. Treatment of the polymerized phase with organic solvents produces a porous structure, with the voids totaling 48% in the case of exposure in vacuum, and 30% when exposed in air.