卷 91, 编号 4 (2017)

Nanosystems based on zero-valent selenium and biocompatible polymer stabilizers (polyvinylpyrrolidone with molecular weight (MW) М_w = (10–55) × 10³, poly-N,N,N,N-trimethylacryloyloxyethylammonium methylsulfate with М_w = (30–250) × 10³ and polyethylene glycol with М_w = (1–40) × 10³) are studied by means of static and dynamic light scattering, and the resulting data are compared. Dense spherical multimolecular nanosystems are found to be formed. Morphological and thermodynamic characteristics of selenium-containing nanosystems, depending on the nature and MW of the polymer stabilizer, are determined. It is shown that the properties of nanosystems can be adjusted by varying the molecular weight of the polymer stabilizer.

A critical analysis is performed of existing literature data on the melting diagrams of systems whose components are a low-volatile metal and a high-volatile component. Models for the р–Т phase diagrams of binary systems are developed, and characteristic isobaric sections (partial state diagrams) are presented that correspond to the experimental data for real systems.

Thermodynamic and kinetic characteristics of cerium(IV) malonate complex formed in the first stage of cerium(IV) oxidation by malonic acid H₂Mal are studied using a spectrophotometer, a photometer, and a pH-meter at a ionic strength of I = 2 in the pH region of 0.3–1.6 in a sulfuric acid medium at a temperature of 296.8 K. Its composition is found to be CeOHMal⁺. The form of organic ligand is Mal²⁻; the thermodynamic parameters of its formation and kinetic parameters of its intramolecular redox decomposition are determined. The most likely scheme of the initial stages of redox proceeding in the Ce⁴⁺–SO₄^2-–H₂Mal system is discussed, and a quantitative model of it is proposed.

The effect acetic acid and sodium hydroxide additives in a 2-propanol aqueous solution of azeotrope composition have on the rate of nitrobenzene (NB) hydrogenation over spongy nickel and supported palladium catalysts is studied. Analysis of the experimental data indicates that adding acid slows the rate more than adding a base during NB hydrogenation on spongy nickel. The observed rate for spongy nickel falls in a series of solvents: 2-propanol–water (0.68 mole fraction) > 2-propanol–water (0.68 mole fraction) + NaOH (0.01M) > 2-propanol–water (0.68 mole fraction) + CH₃COOH (0.01 M). When a palladium catalyst is used, the addition of acid has less of an effect on slowing the rate of the reaction than that of the base: 2-propanol–water (0.68 mole fraction) > 2-propanol–water (0.68 mole fraction) + CH₃COOH (0.01 M) > 2-propanol–water (0.68 mole fraction) + NaOH (0.01 M).

The electronic absorption spectra of aqueous solutions of iodine monochloride ICl are studied. The spectra of as-prepared solutions display the absorption band associated with hydrated ICl molecules. An additional band indicating that molecular iodine was formed in the solution emerges in the spectrum as dissolution takes place. Only the band belonging to iodine monochloride remains in the absorption spectra, and no additional bands appear after chloride anions Cl⁻ are added to the solution. The absorption spectrum becomes more complex when ICl is dissolved in an alkaline medium. The band belonging to molecular iodine emerges in the spectra at low alkali concentrations, while being transformed to other shorter-wavelength bands at high alkali concentrations (рН ≥ 12).

Saturated aqueous solutions of lanthanide chlorides are studied by means of X-ray diffraction. Models of the investigated solutions are used to calculate quantitative characteristics of the immediate environment of ions in solutions using the obtained experimental data. It is established that all of the investigated systems are characterized by similar structures. Cations coordinate six solvent molecules in the first coordination sphere as the Ln³⁺–OH₂ distances become shorter upon transitioning from light to heavy ions. Non-contact ion associates form in all the systems.

Stability constants of the coordination compounds of nickel(II) and cobalt(II) ions with succinic acid anion in water–ethanol solvents are determined via potentiometric titration at ionic strength of 0.1 and at T = 298.15 K. It is found that logβ values of monoligand complexes of these ions and succinic acid anions rise along with the content of ethanol in solution (X_EtOH = 0–0.7 mole fractions). Based on an analysis of the thermodynamic characteristics of the solvation of the reagents involved in complex formation, it is found that the increased stability of succinate complexes of nickel(II) and cobalt(II) ions in water–ethanol solvents is mainly determined by the weakening of the solvation of succinic acid anion (Y²⁻).

Potentiometric measurements are made for the NaF–NaCl–H₂O system at 25, 50, and 75°C using Na⁺- and F^–-sensitive electrodes and a Ag/AgCl reference electrode in both liquid junction and liquid junction free cells. A correction for the liquid junction potential is introduced to the liquid junction cells. The activity coefficients are calculated using the Debya–Hückel equation in the third approximation. The NaF thermodynamic association constants are determined (logK° =–0.375,–0.29, and–0.25) with an error of ±0.1 log units at 25, 50, and 75°C, respectively.

Thermodynamic, surface and micellar properties of anti-inflammatory drug sodium 2-(4-isobutylphenyl) propionate (sodium salt of ibuprofen (NaIBF)) in aqueous/urea solution were studied by surface tension measurements at 298.15 K in the presence of anionic surfactant sodium dodecylsulfate (SDS). Critical micelle concentration (cmc), surface tension at cmc (γcmc), maximum Gibbs surface excess (Γ_max), minimum surface area per surfactant molecule at the air/water interface (A_min) etc. were determined in pure water as well as in aqueous urea solution. The theories of Clint, Rosen and Rubingh have been applied to describe the interactions between these amphiphiles at the interface and in the micellar solution. Various thermodynamic parameters have been calculated and discussed in detail.

The solutions of palladium PdBr₂ and lithium LiBr bromides in tetrahydrofuran (THF) at different concentrations were studied by UV–Vis spectroscopy. The data obtained were mathematically processed using various models. The best description was obtained with the model that includes the formation of four monomeric (PdBr⁺, PdBr₂, PdBr₃^-, PdBr₄^2-) and three dimeric (Pd₂Br₂²⁺, Pd₂Br₄, Pd₂Br₆^2-) palladium complexes. The equilibrium constants of the monomer and dimer complexation stages and the extinction coefficients of the palladium complexes were calculated. The spectra of the individual monomer and dimer palladium complexes were calculated using this model.

The changes in the UV–Vis absorption spectra of dimethylaminoazobenzene (DAB) in the cellulose triacetate (CTA) matrix during the absorption of gaseous hydrogen chloride and protonation of DAB in weakly and strongly acid solutions of hydrochloric and sulfuric acids were studied. The yellow-orange color of DAB and its analog aminoazobenzene (AAB) was shown to be due to the dimers, whose structure involves phenylaminyl type cations formed due to the promotion of the sp² electrons of the azo groups to the Rydberg R_3s orbitals of the azo groups and possessing Vis bands at 400–417 nm. The cations exist immanently as the dimers due to the Rydberg intermonomer bonds; the Vis bands of the dimers shifted toward 500–520 nm under the action of HCl (in CTA) and weakly acid media as a result of the formation of phenyl aminyl type pair cations, whose π* levels are split by Simpson’s mechanism, during the protonation of interrelated monomers. In the concentrated sulfuric acid, the Vis bands at 500–520 nm vanished because of the decomposition of the dimers into diprotonated monomers possessing Vis bands at 400–417 nm. The mechanism of transformations of chromogens responsible for the spectral transformation was given.

A density functional theory (DFT) calculations using B3LYP/6-311++G(d,p) method were carried out to investigate the relative stability of the molecules of β-carboline derivatives such as harmaline, harmine, harmalol, harmane and norharmane. Calculated nuclear quadrupole resonance (NQR) parameters were used to determine the ¹⁴N nuclear quadrupole coupling constant χ, asymmetry parameter η and EFG tensor (q_zz). For better understanding of the electronic structure of β-carboline derivatives, natural bond orbital (NBO) analysis, isotropic and anisotropic NMR chemical shieldings were calculated for ¹⁴N nuclei using GIAO method for the optimized structures. The NBO analysis shows that pyrrole ring nitrogen (N9) atom has greater tendency than pyridine ring nitrogen (N2) atom to participate in resonance interactions and aromaticity development in the all of these structures. The NMR and NQR parameters were studied in order to find the correlations between electronic structure and the structural stability of the studied molecules.

The formation of nanolayers of silicon and aluminum oxides, obtained by means of molecular layering (or atomic layer deposition (ALD technology)) on surfaces of GaAs, InAs, and InSb, is investigated. Conditions for the layer-wise growth of surface nanostructures are established, and some of their dielectric characteristics are estimated.

Micro-mesoporous titanosilicate precursors of the active absorption phase of a composite ceramic membrane are synthesized, and their textural and adsorption properties are investigated by means of low-temperature nitrogen adsorption/desorption. Low-temperature isotherms of nitrogen adsorption/desorption are analyzed using the BET, Langmuir, comparative t-plot, Barrett–Joyner–Halenda, and density functional theory methods. It is found that at high contents of silicon(IV) oxide, the resulting xerogels have surface areas of 656 and 890 m²/g according to the BET and Langmuir approaches, respectively, while the micropores’ inner and outer surfaces are 453 and 466 m²/g, respectively, according to the t-plot. According to the DFT distributions, the mesopore diameters of a sample can be adjusted in the range of 3–9 nm. By analyzing the type of capillary condensation hysteresis in the adsorption/desorption isotherms, it is shown that the pores in the samples are very bottle-like, even though their shape may be different in reality. It is found that in samples with high contents of titanium(IV) oxide, the pore throats are blocked during adsorbate desorption, due to the percolation effect. It is assumed that the stabilization of particles of titanium(IV) oxide by amorphous layers of silica protects the texture of titanosilicate xerogels from full contraction and the coalescence of particles during heat treatment ranging from 393 to 923 K.

It is found that the tension at the interfacial boundary of liquid phases formed by mixtures of acetonitrile–ethyl acetate–isopropanol (85 : 15 : 0 and 80 : 15 : 5 vol/vol/vol %) and water at 263 K falls exponentially as the concentration of phenols grows within 0–1 mg/mL. It is shown that the relatively low values of interfacial tension (11–32 mN/m) observed in cooled heterogeneous systems promote the redistribution of phenols between two liquid phases.

Optimum conditions of the dynamic concentration of copper(II) and silver(I) ions simultaneously present in a solution with N-(2-sulfoethyl)chitosan with a degree of modification equal to 0.5 and different degrees of crosslinking by glutaraldehyde are determined. The values of coefficients of selectivity K_Ag/Cu are determined under dynamic conditions. It is shown that the selectivity of the sorption of silver(I) increases (compared to copper(II)) as the degree of crosslinking of sorbents based on N-(2-sulfoethyl)chitosan is raised. Mathematical treatment of the obtained dynamic curves is performed according to the Thomas, Adams–Bohart, and Yoon and Nelson models. As a result, the values of dynamic capacity of sorbents, the rate constant of the reaction, and the release time of 50% of the sorbate are determined. The quantitative desorption of copper and silver from the surface of sorbents is achieved by using 1 mol/dm³ solution of nitric acid.

Loading properties are studied for the commercial porous layered capillary columns GASPRO, Rt-Q-BOND, and for columns with porous layers based on the divinylbenzene-vinylimidazole copolymer (DVB-VIm), poly(trimethylsilyl)propyn (PTMSP) and ordered silica of the MCM-41 type. It is shown that the loading capacity of a column based on MCM-41 is 5–10 times higher than in the other considered columns. The loading properties of porous layered columns and columns for gas–liquid chromatography are compared.

The change in electric conductivity and dielectric permittivity during the curing of epoxy–amine compositions in a mixture with the thermoplastic Ultem 1000 polyetherimide at 180°C is studied by means of dielectric spectroscopy. TGDDM epoxy resin and DADPS, MDEA, and MIPA amine curing agents are used as the epoxy–amine composition. The times of the gel and glass transition are determined from the time and frequency dependences of the dielectric response of the investigated mixtures. At a certain step of curing of epoxy–amine compositions, the separation of a new phase enriched with the thermoplastic is detected. This separation is accompanied by charge accumulation along the phase boundary and its interaction with the external electric field. In the dielectric spectrum, this effect of phase separation appears as an individual relaxation process with characteristic parameters of dielectric relaxation. It is found that at the final step of isothermal curing, there is a glass transition of the polymer, leading to a sharp drop in the reaction rate and stabilization of the dielectric response with respect to time. The detected steps of the reaction and the corresponding changes in the structure and rheology of the investigated polymer systems are characterized and confirmed by methods of viscometry and optical microscopy.

A novel red-emitting phosphor LiLaMgWO₆ : Eu³⁺ has been synthesized by a high-temperature solid-state reaction. X-ray powder diffraction (XRD) analysis and FT-IR spectra confirmed the formation of LiLaMgWO₆ : Eu³⁺ phase. The photoluminescence excitation and emission spectra, the concentration dependence of the emission intensity, decay curves, and UV–Vis absorption spectra of the phosphor were obtained. The phosphor could be efficiently excited by the near ultraviolet (NUV) and blue light, exhibiting red light emission. The decay time was also determined for various Eu³⁺ concentrations in LiLaMgWO₆. The calculated color coordinates of the emitted light lie in the red region. Therefore, the obtained results suggest that the prepared phosphors exhibit great potential for use as red emitting phosphor for white light emitting diodes.