Vol 91, No 10 (2017)

The morphological structure and gas transport properties of polyimide- and polyamide-imidebased rigid-chain polymers containing a fine carbon filler (a diamond blend) are studied. Gas transport properties are measured, and the effect exerted on these properties by intermolecular interaction between the functional groups of polymer chains and the fine filler is analyzed.

Kinetics of the reaction of aquacobalamin (H₂OCbl) with isoniazid (isonicotinic acid hydrazide, INH) in weakly alkaline, neutral, and weakly acidic media was studied using UV–Vis spectroscopy. It is shown that the reversible formation of a complex more stable than those of cobalamin(III) with pyridine and hydrazine occurs during the reaction. A mechanism of the reaction includes reversible stages of binding a neutral INH molecule by cobalamin(III) through an oxygen atom with its subsequent deprotonation, along with the reversible interaction of H₂OCbl and the negatively charged form of INH.

The kinetics and mechanism of interaction between pyridoxal and L-tryptophan, D-tryptophan, and their derivatives are studied. It is found that condensation reactions proceed via three kinetically distinguishable stages: (1) the rapid intraplanar addition of the NH₂ groups of the amino acids to pyridoxal with the formation of amino alcohols; (2) the rotational isomerism of amino alcohol fragments with their subsequent dehydration and the formation of a Schiff base with a specific configuration; (3) the abstraction of α-hydrogen in the product of condensation of pyridoxal with L-tryptophan, or the abstraction of СО₂ in the product of condensation of pyridoxal with D-tryptophan with the formation of quinoid structures, hydrolysis of which results in the preparation of pyridoxamine and keto acid or pyridoxal and tryptamine, respectively. Schiff bases resistant to further chemical transformations are formed in the reaction with tryptophan methyl ester.

Ab initio calculations of the energy parameters for a series of gas-phase reactions of the deprotonation of para-substituted toluenes (OH, CH₃, H, Cl, NC, CN, and NO₂ substituents) by CH₂Cl^–, H(O)C^–, CH₃O^–, H(F)N^–, NH₂C≡C^–, and CH₃C≡C^– anions (the conjugated acids are chloromethane (CH₃Cl), formaldehyde (Н₂CO), methanol (CH₃OH), fluoroamine (NH₂F), aminoacetylene (NH₂C≡CН), and methylacetylene (CH₃C≡CН), respectively) is performed using a technique of intramolecular reorganization proposed earlier. The equilibrium (E_a^eq) and nonequilibrium (E_a^neq) contributions to energy of activation E_а are found for distance Q(C…B) = 3.0 Å (where С and В are the central atoms of the acid and base). At this value of Q, the tunneling mechanism of proton transfer predominates. The results from calculations, together with similar data obtained earlier for reactions of the deprotonation of toluenes by СН₂CN^– anions, are considered from the viewpoint of the harmonic Marcus model. It is found that in the graph ΔE₀ − E_a^neq (where ΔE₀ is the internal energy of the reaction (for a collision complex)), the points for five reaction series with C-bases fall on the same quadratic (within the −11 to 12 kcal/mol range of ΔE₀) curve; the second curve, which includes points for the series with N- and O-bases (OCH₃^– and H(F)N^–) is shifted below the first curve by 1.5 kcal/mol. For most reaction series (except the one with the strongest bases, CH₂Cl^– and H(O)C^–), the curvature and slope of graph ΔE₀ − E_a^neq are in agreement with the theory. The correlations of energies E_a^neq, E_a^eq, E_а, and ΔE₀ with the energy of reaction ΔE₀₀ are satisfactorily described by quadratic equations as well. Differences between the structures of bases are reflected most by energy E_a^eq and the height of the proton tunneling barrier in the activated complex (AC) E_b. For the series of reactions of toluene with a set of bases, graphs ΔE₀₀ − E_a^eq and ΔE₀ − E_b show good linear correlation between the values (opposite in sign) of departures from straight lines drawn through the points for two C-bases of the same type (CH₂Cl⁻ and СН₂CN⁻).

Spectrophotometric investigation of Cu (II), Ni(II), Co(II), and Fe(III) complexes with 2,4-dihydroxyacetophonone 2,4-dichlorobenzoylhydrazone (H₂L¹) and 2,4-didydroxy-5-nitroacetophenone 2,4-dichlorobenzoylhydrazone (H₂L²) shows 1: 1 and 1: 2 complex formation between the pH range of 3.0 to 6.0 and also studied by jobs variation method at 0.1 M ionic strength at 30 ± 1°C specrtophotometrically. The conditional stability constants are determined for 1: 1 complexes. Effect of H₂L¹ and H₂L² ligand and its complexes on seed germination is studied.

A model has been suggested that describes the interaction of hydrated ions in electrolytes and allows the calculation of the main physical effects. The model explains the character of the curves of the activity coefficients. Binary solutions of uni-univalent electrolytes at concentrations from zero to several moles per liter and at temperatures from zero to a few dozens of degrees were studied. The results of simulation were verified by comparing them with many literature data.

The brilliant blue FCF acid–base properties in aqueous solutions have been studied and its ionization constants have been defined by tristimulus colorimetry and spectrophotometry methods. The scheme of the acid–base dye equilibrium has been proposed and a diagram of the distribution of its ionic-molecular forms has been built. It has been established that the dominant form of the dye was the electroneutral form, which molar absorptivity (ε₆₂₅ = 0.97 × 10⁵) increases with the increase of the dielectric permittivity of the solvent. It has been shown that the replacement of polar solvents by less polar ones is causing a bathochromic shift of the maximum absorption band of the dye, the value of which is correlated with the value of the Hansen parameter. Tautomerization constants have been defined in a number of solvents and associated with the value of the Dimroth-Reichardt parameter.

It is established that the formation of a viscous film on the surface of a melt is possible during the viscosimetry of Fe–B melts under normal conditions. It is noted that the film has a considerable effect on the results from measurements and can lead to the appearance of additional features on polyterms. Thermodynamic analysis of the composition of surface layers shows that a viscous film contains mainly boron oxide B₂O₃. It is concluded that the evaporation of B₂O₃ from the surface of the alloy produces additional anomalies on the polytherm of viscosity.

The method of isothermal dissolution was used to study the solubilities and the densities of the two systems MgCl₂–MgB₄O₇–H₂O and KCl–K₂B₄O₇–H₂O at 273 K. By the X-ray diffraction the equilibrium solids were determined. The phase diagrams and density versus composition diagrams of the systems MgCl₂–MgB₄O₇–H₂O and KCl–K₂B₄O₇–H₂O at 273 K were plotted. The both diagrams are consisted of one invariant, two stable solubility isothermal curves and two crystallization fields. The crystallization fields for the system MgCl₂–MgB₄O₇–H₂O corresponds to MgB₄O₇ · 9H₂O and MgCl₂ · 6H₂O. Those for the system KCl–K₂B₄O₇–H₂O corresponds to K₂B₄O₇ · 4H₂O and KCl.

The textural and structural properties of mixed oxides Ga₂O₃–Al₂O₃, obtained via impregnating γ-Al₂O₃ with a solution of Ga(NO₃)₃ and subsequent heat treatment, are studied. According to the results from X-ray powder diffraction, gallium ions are incorporated into the structure of aluminum oxide to form a solid solution of spinel-type γ-Ga₂O₃–Al₂O₃ up to a Ga₂O₃ content of 50 wt % of the total weight of the sample, accompanied by a reduction in the specific surface area, volume, and average pore diameter. It is concluded that when the Ga₂O₃ content exceeds 50 wt %, the β-Ga₂O₃ phase is observed along with γ-Ga₂O₃–Al₂O₃ solid solution. ⁷¹Ga and ²⁷Al NMR spectroscopy shows that gallium replaces aluminum atoms from the tetrahedral position to the octahedral coordination in the structure of γ-Ga₂O₃–Al₂O₃.

An expression for the average velocity of a semiconductor photomotor has been obtained. A threelevel model of the electron subsystem of a photomotor with arbitrary transition rate constants was considered, and the time dependences of the occupation of its electronic levels were calculated. Variation of the occupation of the levels with time determines the time dependence of the potential energy and the average velocity of the photomotor motion along the polar substrate. The optimum conditions of laser photoexcitation and the kinetic characteristics of electron transitions in the photomotor that provide the maximum velocity of its directional motion were determined.

Size dependences of the surface tension of spherical single-component droplets are calculated using equations of the lattice gas model for 19 compounds. Parameters of the model are found from experimental data on the surface tension of these compounds for a macroscopic planar surface. The chosen low-molecular compounds satisfy the law of corresponding states. To improve agreement with the experimental data, Lennard-Jones potential parameters are varied within 10% deviations. The surface tensions of different sized equilibrium droplets are calculated at elevated and lowered temperatures. It is found that the surface tension of droplets grows monotonically as the droplet size increases from zero to its bulk value. The droplet size R₀ corresponding to zero surface tension corresponds to the critical size of the emergence of a new phase. The critical droplet sizes in the new phase of the considered compounds are estimated for the first time.

The effect of silver nanoparticles (NPs) in the concentration range of ≤0.8 wt % have on direct current conductivity σ_dc of Ag-ED20 nanocomposite is studied by method of broadband dielectric spectroscopy (10⁻²–10⁵ Hz) method of broadband dielectric spectroscopy. It is found that temperature dependence σ_dc consists of two sections: above the glass transition temperature (T_g), the dependence corresponds to the empirical Vogel–Fulcher–Tammann law (Vogel temperature T₀ does not depend on the NP concentration); below T_g, the dependence is Arrhenius with activation energy E_a ≈ 1.2 eV. In the region where T > T_g, the σ_dc value grows along with NP concentration. It is concluded that the observed broken form of the temperature dependence is apparently due to a change in the conduction mechanism after the freezing of ion mobility at temperatures below T_g.

A modified polyacrylamide gel route was used to prepare SrFe₁₂O₁₉ magnetic nanoparticles; ethylenediaminetetraacetic acid (EDTA) was used as a carboxyl chelating agent. The phase purity, morphology and magnetic properties of as-prepared samples were analyzed via X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating sample magnetometery (VSM). XRD analysis indicates that high-purity SrFe₁₂O₁₉ magnetic nanoparticles can be synthesized at 700°C in air. The characteristic peaks of as-prepared sample at 210, 283, 321, 340, 381, 411, 432, 475, 532, 618, 686, and 726 cm^–1 were observed in Raman spectra. SEM and TEM show that the synthesized SrFe₁₂O₁₉ magnetic nanoparticles are uniform with the mean particle size of ~60 nm. VSM measurement shows that the maximum magnetic energy product (BH)_max of sample prepared using EDTA as a chelating agent is higher than that of sample prepared using citric acid as a chelating agent.

Carbon-supported oxide-rich Pd–W bimetallic nanoparticles were prepared by chemical reduction methods. The existence of oxides in the electrocatalysts is confirmed by X-ray photoelectron spectrum (XPS) and high resolution transmission electron microscopy. XPS analysis indicates that the oxygen atoms account for about 50% of all the atoms in Pd–W bimetallic nanoparticles. Compared to Pd/C catalyst, the carbon-supported oxide-rich Pd–W bimetallic nanoparticles exhibit a better catalytic activity for the anode oxidation of ethanol in alkaline media. The onset potential of the as prepared oxide-rich Pd_0.8W_0.2/C catalyst (Pd: W = 8: 2, metal atom ratio) for ethanol oxidation is negative shifted about 90 mV comparing to Pd/C catalyst. The oxide-rich Pd–W/C electrocatalysts provide a new model of noble-metal/promoter system as an extreme case of making the promoter (WO₃) closely adjacent to the noble metal (Pd) by fabricating nanoparticles containing both atom-clusters of oxides and the noble metal atoms.

γ-Fe₂O₃–SiO₂ composites are synthesized via the coprecipitation of a γ-Fe₂O₃ magnetic carrier (with specific surface S = 17 m²/g and pore volume V = 0.51 cm³/g) and silicon dioxide from an aqueous glass (sodium silicate) solution. The effect coagulation agent NaCl has on the coprecipitation process and structural characteristics of the composite is discussed. Adding NaCl to the aqueous glass solution prevents the formation of SiO₂ macrogel making it possible to obtain highly porous composites with high adsorption capacity for proteins cytochrome C and hemoglobin. It is established that a composite that is 50% SiO₂ and produced with the addition of 5% NaCl (S = 150 m²/g and V = 0.87 cm³/g) has a sixfold and twofold higher capacity (280 and 175 mg/g) for cytochrome C and hemoglobin, respectively, than the initial ferric oxide (45 and 82 mg/g). The capacity for cytochrome C and hemoglobin of a composite synthesized without NaCl (S = 50 m²/g and V = 0.45 cm³/g) is 19 and 20 mg/g, respectively, which is twofold and fourfold lower than those of the initial γ-Fe₂O₃. The dependence of protein adsorption on pH and the ionic strength of a solution is studied, and the conditions for the maximum adsorption and complete desorption of proteins are established. It is concluded that composites synthesized with additions of NaCl can be used as magnetocontrollable sorbents for the purification, concentration, and immobilization of proteins, and for the preparation of biocatalysts based on immobilized enzymes.

Donor–acceptor interactions between silver nanoparticles (NPs), resonance-excited by optical quanta of light, and halide ions are studied in aqueous solutions. It is shown that deactivation of the plasmon excitation of Ag NP proceeds according to the exchange mechanism of electron transfer. Plasmon excitation quenching constants are determined and a correlation between quenching and the donor properties of halide ions is found. The efficiency of electrostatic interaction between resonantly-excited Ag NPs and halide ions is studied, and their dipole moment is determined.

A way of organizing and processing the results from gas–chromatographic experiments to obtain chromatographic retention characteristics for a fixed concentration of sorbate in the gas phase or on the surface of the sorbent is proposed and substantiated. The suitability and expediency of such retention characteristics for describing the sorption properties of inhomogenous sorbents is demonstrated using a wide variety of adsorbents of different natures (activated carbons, swelling and nonswelling polymers, silicas and their silver derivatives) as examples.

The conductivity and electrochemical stability of choline chloride (ChCl) solutions with water contents ranging from 20 to 39 wt % are studied. Exposing ChCl to moist ambient air yields a highly concentrated aqueous solution that, as an electrolyte, exhibits the properties and variations in conductivity with temperature and concentration characteristic of other similar systems. Its electrochemical stability window, determined by cyclic voltammetry, is comparable to that of ChCl-based deep eutectic solvents (DESs). Products of the electrolysis of ChCl‒H₂O mixtures seem to be less toxic than those of Reline, Ethaline, and Maline.

Luminescent properties of pyrene in the ordered structure formed by the molecules of a surface-active substance represented by cetyltrimethylammonium bromide on a cellulose matrix preliminarily modified with silver nanoparticles are studied. Elevated intensity of fluorescence in the violet range of the spectrum of pyrene molecules solubilized in these structures is observed. This phenomenon is rationalized by the resonance of electron transitions of monomeric pyrene molecules in this range with plasmonic vibrations in silver nanoparticles.

Thin film CdIn₂Te₄/CdS solar cells were deposited onto the ITO-coated glass substrate by electron beam evaporation (e-beam) technique, and the the effect of annealing on their structural properties is studied. The annealing was performed under nitrogen atmosphere for 1 h. The manufactured solar cells were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray (EDAX) analysis. Crystallite size (D), inter-planer distance (d) and lattice constant (a) values were calculated for the thin film solar cell from XRD data. Annealed samples display well defined XRD patterns with three diffraction peaks. We observed increased peak intensity in the annealed films. EDAX analysis showed that only CdIn₂Te₄ is present in absorber layer and CdS is found in the window layer, but no impurity atoms are present the structure. It is observed that surface roughness of the annealed films incresed, according to SEM images. The I–V characteristics show that the current is increased for annealed thin films solar cells.

Imidazolium ionic liquids with alanine anion, [C_nmim][Ala] (n = 2, 3, 4, 5, 6), were prepared and characterized. The standard addition method was used to measure refractivity of the synthesized ionic liquids in order to eliminate the effect of water traces in the ionic liquids. The molar refraction and molecular polarizability were also calculated by Lorentz–Lorenz’s method. Using liner extrapolation, the semiempirical estimation method for optical properties of other ionic liquids with amino acid anions was established.

Kinetics of decomposition under the action of laser UV radiation is studied for alkynyl–phosphine complexes with bimetallic cores. It is shown that photodegradation is a zero order reaction, and the reaction rate depends on the substituents in the core of the complex. The sequence of decomposition processes is determined for the complexes after optical excitation. It is established that the rate of the ligand environment’s detachment is three times faster than that of the decomposition of the complexes’ cores. It is found that introducing halide ions into the structure of a cluster’s core increases the photochemical stability of the complexes.

The heat capacities and densities of three-component solutions NaI–CdI₂–N-methylpyrrolidone (NMP), KI–CdI₂–NMP, RbI–CdI₂–NMP, ВаI₂–CdI₂–NMP, NaNO₃–Cd(NO₃)₂–NMP at 298.15 K are investigated via calorimetry and densimetry. The values of the heat capacities and volumes upon the formation of three-component systems from binary solutions are calculated and discussed. It was established for all of the investigated systems that their deviations from additivity are due to the predominance of processes of acido complex formation.