Vol 90, No 1 (2016)

The thermochemical properties of melts of the binary Gd–In system were studied by the calorimetry method at 1470–1700 K over the whole concentration interval. It was shown that significant negative heat effects of mixing are characteristic features for these melts. Using the ideal associated solution (IAS) model, the activities of components, Gibbs energies and the entropies of mixing in the alloys of this systems and its phase diagram were calculated. They agree with the data from literature.

In the present study ultrasonic velocity (υ), density (ρ), and viscosity (η) of the mixtures of atenolol drug with ethanol have been measured at frequency 1 MHz in the concentration range 0.1–0.0125% at 303, 308, and 313 K using multifrequency ultrasonic interferometer. The measured values have been used for calculations of the mixtures acoustical parameters. These parameters explained molecular interactions existing in the solution.

We have elucidated the details of mechanism of CO oxidation catalyzed by Al_nPt (n = 1–11) clusters through first-principle density-functional theory (DFT) calculations. These subnanometer species transform into reaction complexes which catalyze CO oxidation through a kind of mechanism, occurring via Langmuir-Hinshelwood path. It is shown that mixing two different metals (Al and Pt) can have beneficial effects on the catalytic activity. The alloyed Al_nPt clusters are proposed as effective nanocatalysts at lower temperatures (equal to room temperature). The adsorption of O₂, CO, and their coadsorption at various sites of neutral Al_nPt (n = 1–11) clusters have been modeled. It was found that in all situations, Pt sites are the catalytically active centers for CO but that for O₂ molecule is not the same result.

The phase compositions of samples obtained during the treatment of anhydrous sulfates Ln₂(SO₄)₃ (Ln = La, Pr, Nd, Sm) in a stream with an excess of hydrogen in the temperature range of 400 to 1100°C at exposures of up to 420 min are determined. Kinetic schemes are compiled for the chemical transformations and changes of phase composition of the mixtures in coordinates of temperature and time that have six fields of the phase combinations: Ln₂(SO₄)₃, Ln₂(SO₄)₃ + Ln₂O₂SO₄, Ln₂O₂SO₄, Ln₂O₂SO₄ + Ln₂O₂S, Ln₂O₂S, and Ln₂O₂S + Ln₂O₃. Single-phase samples of Ln₂O₂SO₄ compounds are obtained at temperatures (°C) of 540–560 (La), 460–520 (Pr), 470–520 (Nd), and 480–520 (Sm). The temperatures (°C) of Ln₂O₂S compounds are 580–920 (La), 600–900 (Pr), 600–900 (Nd), and 600–800 (Sm). It is shown via electron microscopy that particles of La₂(SO₄)₃ in the shape of cylinders are converted into flakes of Ln₂O₂SO₄, predominantly flat Ln₂O₂S crystallites.

The oxidation of (Cl)(H₂O)IrTPP with atmospheric oxygen in the presence of concentrated H₂SO₄ accompanied by coordination of molecular O₂ and substitution of axial ligands was studied spectrophotometrically. In 16.785–18.09 М H₂SO₄ at 298–318 K, (Cl)(H₂O)IrTPP experienced two single-electron oxidations in sequence: with an increase in the oxidation state of the iridium cation and with formation of the π-radical cation form (HSO₄)Ir^IVTPP^•+ oxidized at the aromatic ligand (k²⁹⁸ = 7.2 × 10^–6 mol^–1 L s^–1). Referring to the literature data on the oxidation of (Cl)(H₂O)IrTPP in AcOH and CF₃COOH, it was shown that the medium acidity and the nature of the axial ligands affect the electron removal site in the chemical oxidation of (Cl)(H₂O)IrTPP with atmospheric oxygen in proton-donor solvents.

Changes in the viscosity, electrical conductivity, monomer concentration, and the size of growing molecules of polycondensed furfuryl alcohol are studied in solutions containing triethylene glycol and isooctylphenyldecaethylene glycol. The effect the solution compositions have on the condensation kinetics is considered.

The catalytic activity of vanadium doped TiO₂ in the ethylbenzene oxidative dehydrogenation with CO₂ was studied experimentally and theoretically. The experimental results showed that the reduction of ethylbenzene conversion and the styrene selectivity was caused by the transition of anatase to rutile phase. Theoretical results showed that the transition of the anatase to rutile phase was mainly caused by vanadium ions and oxygen vacancies.

The novel magnetic Co_0.5Mn_0.5Fe₂O₄-chitosan nanoparticles has the advantage of excellent biodegradation and a high level of controllability. The Co_0.5Mn_0.5Fe₂O₄-chitosan nanoparticles was prepared successfully. The size of the Co_0.5Mn_0.5Fe₂O₄-chitosan nanoparticles were all below 100 nm. The saturated magnetization of the Co_0.5Mn_0.5Fe₂O₄-chitosan nanoparticles could reach 80 emu/g and showed the characteristics of superparamagnetism at the same time. The image of TEM and SEM electron microscopy showed that the cubic-shape magnetic Co_0.5Mn_0.5Fe₂O₄ particles were encapsulated by the spherical chitosan nanoparticles. The evaluation on the interfacial properties of the product showed that the interfacial tension between crude oil and water could be reduce to ultra-low values as low as 10^–3 mN/m when the magnetic Co_0.5Mn_0.5Fe₂O₄-chitosan nanoparticle was used in several blocks in Shengli Oilfield without other additives. Meanwhile, the magnetic Co_0.5Mn_0.5Fe₂O₄-chitosan nanoparticles possessed good salt-resisting capacity.

The temperatures of nucleation and growth for gold and silver nanoparticles are quite close to each other in citrate-based seeded-growth synthesis. Hence, thorough temperature control during the synthesis of gold and gold–silver core–shell nanoparticles is expected to improve the yield of uniform non-aggregated nanoparticles suitable for selective contrasting of surface defects. Gold and gold–silver core–shell nanoparticles of size ranging from 20 to 160 nm were synthesized using various means of temperature control. The synthesized nanoparticles were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS) and UV–Vis spectroscopy. Model nanocracks were milled on pipeline steel specimen by focused ion beam (FIB). It was found that to produce large uniform core–shell nanoparticles, thorough temperature control is required during formation of the gold seeds and the silver shell. Moreover, the synthesized nanoparticles were used for selective contrasting of defects on metal surface.

In this paper, we present a systematic investigation into reactivity of 1,3-dipoles on coronene as model for nanographenes using the density functional theory (DFT). The calculations show that the dipole nature mainly involving the structure and electrical effect is the major influence on reactivity. The 18-valence-electron azomethine ylides shows more active than the other two types of 1,3-dipoles with 16-valence-electron to NG, which may due to a smaller singlet-triple splitting. The more electronegative terminate group leads a higher stability and chemical inertness of the 1,3-dipole. There the reactivity order is oxide < imine < ylide. The varied distortion energy which determines the activation energy depends on the deformation of the 1,3-dipole. It can be obviously observed the distortion energy increases as the strengths of two resonance bonds of the 1,3-dipole increase in each series. The less electronegative terminate group leads the more electron-deficient and the less electron delocalization of the 1,3-dipole and even the more stable of the intermediate, which leads the cycloaddition proceed easier. The trend that the activation energy decreases as the strengths differences of the two new bonds of intermediate is also very clear in each series. All the reactivities are consistent analyzing in frontier molecular orbitals (FMO) theory. Unlike the 1,3-DC toward some other dipolarophiles, the vast majority of the studied 1,3-dipole cycloaddtions (DC) are of largely negative Gibbs free energies (ΔG^≠) values which are spontaneous at the temperature. There is correlation between the extent of spontaneous of reaction and the activation energy. There is also good relationship between the activation energy and the reaction energy, which follows the Hammond postulate.

According to the method of Langmuir-Blodgett the thermodynamic behavior and the miscibility of the two phospholipids 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) with 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) in the mixed monolayer were evaluated in terms of the excess mean molecular area, excess Gibbs free energy and compressibility coefficient. DMPC and DOTAP were miscible and a repulsive interaction appeared between DMPC and DOTAP molecules at most of selected ratios and surface pressures. Meanwhile, the interaction between DSPC and DOTAP were attractive and the most stable monolayers were formed at the 3: 2 and 1: 4 stoichiometry. The morphology observations by fluorescence microscopy reveals that the size of the domains composed of DSPC were larger than DMPC.

In view of the great practical utility of aluminum–rare earth metal (REM) powders as adsorbents and catalyst supports, the dispersion composition and morphology of Al–3%Y alloy powder particles obtained by various methods (gas plasma recondensation, nitrogen sputtering) were studied by low-temperature nitrogen adsorption, scanning electron microscopy, XRD, etc. The phase composition of the powders was determined, and the amount of active aluminum was calculated. The nitrogen adsorption on the powder surface was studied experimentally at–196°С at relative pressures of Р/Р_s = 10^–3–0.999. The specific surface areas of the powders were determined.

The extraction of samarium and europium from a melt of a molar composition 73LiF–27BeF₂ into liquid bismuth with additions of lithium as a reducing agent at a temperature of 600–610°С was studied. The equilibrium distribution coefficients of samarium and europium were measured. In the metal fluoride salt melt under study, the valence of samarium and europium was shown to be equal to two.

A high energy density LiFePO₄/C material for lithium batteries was synthesized by controlled crystallization-carbothermal reaction, which has been experienced as an effective process for mass production of electrode materials. The structure and morphology of the LiFePO₄/C material were characterized by X-ray diffraction and Scanning Electron Microscope (SEM). The electrochemical properties of the synthesized nano-LiFePO₄/C were investigated by charge-discharge processing and cyclic voltammetry (CV). The initial discharge capacities of the LiFePO₄/C battery were 163.9, 158.4, 154.5, 151.4, and 142 mA h g^–1 at 0.1C, 1C, 2C, 5C, and 10C, respectively. The capacity of LiFePO₄/C material maintained 98.5% at the rate of 1C after 100 cycles, demonstrating excellent rate capability and cycling performance.

Terbium complex of ethylenediaminetetraacetate ([Tb(EDTA)]^–) intercalated Zn/Al layered double hydroxide (LDH), as an inorganic-organic green-emitting phosphor, was synthesized through an ion exchange method. X-ray powder diffraction (XRD) and Fourier transform infrared (FTIR) spectra exhibit a successful intercalation of [Tb(EDTA)]^– anions between the hydroxide sheets of the LDH. The basal spacing of 14.5 Å indicate a vertical arrangement of [Tb(EDTA)]^– anions with the maximal dimension in the gallery is adopted. The luminescent properties of this material were studied by excitation and emission spectra. The results show that the strongest emission peak of Tb³⁺ ion occurs at 544 nm. This material may supply a candidate of green light emitting phosphor.

Analytical equations for coefficients of dielectric permeability ε₁(ω) and dielectric losses ε₂(ω) of electrolyte solutions are obtained, based on the relationship between complex dielectric permeability and specific conductivity coefficients. The region of frequency dispersion is considered for dynamic dielectric permeability coefficient ε₁(ω) of an aqueous NaCl solution. Friction coefficients β_a and β_b, relaxation times τ_a, τ_b, and τ_ab, and dielectric permeability coefficient ε₁(ω) are numerically calculated for selected intermolecular interaction potentials \({\Phi _{ab}}(\left| {\bar r} \right|)\) and equilibrium radial distribution functions \({g_{ab}}(\left| {\bar r} \right|)\) over a wide range of variation in density ρ, concentration c, temperature T, and frequencies ω. The theoretically calculated results for ε₁(ω) are found to be in quantitative agreement with experimental data.

Models of liquid monoethanolamine with 1000 molecules in a basic cell in the form of a rectangular parallelepiped are constructed by means of molecular dynamics simulation in the temperature range of 293 to 453 K. The simulation is performed in the NVT mode at real densities, and in the NpT mode at p = 1 atm. Voids (pores) in monoethanolamine structure and the temperature dependences of their sizes are analyzed. It is established that the pores appear and disappear via fluctuation in different places. No dynamic relationship between them is observed; during heating, the radius of a maximal pore grows from 1.98 Å at 293 K to 2.53 Å at 453 K. The inner surface of the pores is notably enriched with oxygen and nitrogen atoms and considerably depleted of hydrogen atoms. At temperatures above 290 K, a maximal pore can freely enclose an argon atom. The pores available in monoethanolamine can freely enclose 20 mol % of helium at 293 K and 57 mol % at 453 K; the solubilities of argon are estimated as 0.1 mol % at 293 K and 6.4 mol % at 453 K. The radius of a maximal pore in monoethanolamine is greater than in ethylene glycol by ~0.1–0.3 Å.

A regression model for calculating the boiling point isobars of tetrachloromethane–organic solvent binary homogeneous systems is proposed. The parameters of the model proposed were calculated for a series of solutions. The correlation between the nonadditivity parameter of the regression model and the hydrophobicity criterion of the organic solvent is established. The parameter value of the proposed model is shown to allow prediction of the potential formation of azeotropic mixtures of solvents with tetrachloromethane.

Features of the electronic structure of the nonprotein part of the mutant form of the human hemoglobin molecule, HbS, are studied along with the magnetic state of the iron ion that is the “nucleus” of the active center of the molecule. It is found that the mutant form of the HbS molecule differs from a normal hemoglobin molecule by the distortion of the local environment of the iron ion, which changes the energy level splitting by a crystal field. As a result of ab initio calculations, the magnetic transition in the iron atom from the high-spin state to the low-spin state upon the addition of molecular oxygen to hemoglobin molecule is reproduced. It is established for the first time that a change in the crystal and electronic structure of the active center as a result of a mutation can lead to a substantial change in the energy of the bond between the active center of the hemoglobin molecule and an oxygen molecule.

Gas-phase adsorption of formaldehyde and gas- and liquid-phase adsorption of the methanediol anion on the (111) face of copper, silver, and gold was modeled in terms of the density functional theory and the cluster model of the metal single-crystal surface. In the gas phase, formaldehyde was found to be physically adsorbed on the metals, while the methanediol anion was found to be chemisorbed. It exists on the surface in two different stable states. In aqueous solution, the H₃CO₂^- anion can spontaneously dissociate into the formate ion and two hydrogen atoms.

The purpose of this research is to study the solar energy storage in norbornadiene (1)/quadricyclane (2) system by four direct attachments of substituents at two carbon atoms on both sides of the double bonds C₂=C₃ and C₅=C₆ in 1_X and 2_X; calculating the relative energies at B3LYP/6-311++G** level of theory. The solar energy storage of four electron donating substituents, (push-push effect), X (X =–NH₂,–OH) and four electron withdrawing substituents, (pull-pull effect) X (X =–CO₂H,–CONH₂,–NO₂ and CN) were examined. The solar absorption bands were calculated for 1_X. The DFT calculations reveal that the bands were shifted to the visible spectrum region when the electron withdrawing substituents were used rather than the electron donating substituents.

Formulas for estimating the thermodynamic work during the separation of components of binary and multicomponent mixtures are discussed and generalized. The difference between the work of separation determined from the separation potential and the thermodynamically estimated work during the isobaric–isothermal mixing of fractions separated at the ends of a cascade is calculated and explained.

Refractometric studies of amorphous SiO show that it is not a mixture of Si + SiO₂, but comprises silicon atoms in silicon-oxygen tetrahedra in all oxidation states (with an average value of Z = 2.06) and oxygen ions corresponding to this cation.