卷 90, 编号 12 (2016)

The heat capacity of a partially crystalline second-generation poly(phenylene-pyridyl) dendron with a dodecyl-decorated periphery is studied by high-precision adiabatic vacuum and differential scanning calorimetry in the temperature range of 6 to 530 K. The thermodynamic characteristics of the glass’s transition and melting are determined from the calorimetric data and the degree of its crystallinity is estimated (α = 30%). Standard thermodynamic functions (C_p°, H°-H°(0), S°-S°(0), and G°-H°(0)) for a partially crystalline dendron in the range of T → 0 to 480 K are calculated.

In the present research, a study on the thermodynamical properties of the quinary Co–Cu–Cr–Fe–Ni high-entropy alloys and ternary Ca–Sb–Yb is carried out by the models Kohler, Chou’s general solution method (GSM) and Muggianu. The dependences of composition variation on thermodynamic properties, such as enthalpy of mixing of Co–Cu–Cr–Fe–Ni alloys in simple FCC phase are investigated at the temperatures 1273, 1373, and 1473 K. Moreover, a comparison between the results of the three models and those of other theoretical models shows good mutual agreement.

The formal kinetics of calcium carbonate crystallization in aqueous solutions is studied at a stoichiometric ratio of Ca²⁺ and CO₃^2- ions. The kinetics of the process was monitored by convenient and reliable methods (complexometric analysis for calcium in an aqueous solution and energy dispersive and microscopic measurement of solid particle sizes). The effect the temperature and degree of supersaturation have on the periods of induction and mass crystallization and the equilibrium concentration of calcium ions in solution is estimated at continuously controlled pH and solution ionic strength. The kinetic parameters (n, k, τ_1/2, E_a) of calcium carbonate crystallization are calculated. It is shown that calcium carbonate with a calcite structure formed at a stoichiometric ratio of reagents, and changes in the temperature (25–45°C) and the solution’s degree of supersaturation (2–6) within the considered range had no effect on the characteristics of the solid phase.

Reactions of the oxidation of bivalent cobalt ions by ozone, of the spontaneous decomposition of trivalent cobalt, and of interactions between Co(III) and chloride ions in solutions of sulfuric acid are studied. The order and rate constant of the process of decomposition of Co(III) are determined. Information on the kinetics of the interaction between Co(III) and Cl^– is obtained. Kinetic patterns of the accumulation of Co(III) during the ozonation of solutions of CoSO₄ in sulfuric acid are explained. Molar absorption coefficients of Co(III) and Co²⁺ ions in the visible range of wavelengths are determined.

The physicochemical and catalytic properties of Cu-containing crystalline zirconia, obtained via sol–gel synthesis in the presence of Yb³⁺ ions and polyvinylpyrrolidone, are studied. DTG/DSC, TEM, XRD and BET methods are used to analyze the crystallization, texture, phase uniformity, surface and porosity of ZrO₂ nanopowders. It is shown that increasing the copper content (1, 3, and 5 wt % from ZrO₂) raises the dehydrogenation activity in the temperature range of 100–400°C and lowers the activation energy of acetaldehyde formation. It is found that the activity of all Cu/t-ZrO₂ catalysts grows under the effects of the reaction medium, due to the migration and redispersion of copper.

The enthalpies of complex formation of L-asparagine (HAsn^±) with Nd³⁺ and La³⁺ ions are determined calorimetrically at 298.15 K and an ionic strength of 0.5 (KNO₃). The thermodynamic characteristics of the formation of the NdAsn²⁺, NdAsn²⁺, LaAsn₂⁺, and LaAsn₂⁺ complexes are calculated.

Esterification of 3-hydroxy-2-naphthoic acid with homologous primary and secondary alkenyl alcohols with different chain lengths in the presence of N,N'-carbonyldiimidazole (CDI) and 1,8-diazabicyclo[ 5.4.0]undec-7-ene (DBU) in N,N-dimethylformamide gave the corresponding esters.

The interaction between carbon oxide and [Au_20–nCu_n]_q clusters (n = 0, 1, 19, 20 and q = 0, ±1) is studied by means of DFT/PBE in the scalar relativistic approximation. To establish the composition and structure of an adsorption site, isomers of bimetallic Au₁₉Cu and AuCu₁₉ particles with different positions of the heteroatom at an apex, edge, and face of the tetrahedral framework are considered. The optimized structures are used as the basis to determine the electronic properties of clusters (average bond energy per atom, difference of energies between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), ionization potential, electron affinity energy). The calculated parameters shrink as the copper content in clusters grows. Among the uncharged models, the highest CO adsorption energy is typical of Au₁₉Cu, the heteroatom of which lies at a cluster’s apex. The CO adsorption energy for cationic and anionic clusters grows in comparison to neutral clusters.

The oxygen reduction reaction (ORR) catalyzed by mononuclear and planar binuclear cobalt (CoPc) and iron phthalocyanine (FePc) catalysts is investigated in detail by density functional theory (DFT) methods. The calculation results indicate that the ORR activity of Fe-based Pcs is much higher than that of Co-based Pcs, which is due to the fact that the former could catalyze 4e^- ORRs, while the latter could catalyze only 2e^- ORRs from O₂ to H₂O₂. The original high activities of Fe-based Pcs could be attributed to their high energy level of the highest occupied molecular orbital (HOMO), which could lead to the stronger adsorption energy between catalysts and ORR species. Nevertheless, the HOMO of Co-based Pcs is the ring orbital, not the 3d Co orbital, thereby inhibiting the electron transfer from metal to adsorbates. Furthermore, compared with mononuclear FePc, the planar binuclear FePc has more stable structure in acidic medium and more suitable adsorption energy of ORR species, making it a promising non-precious electrocatalyst for ORR.

The conductivity of polymer composites with magnetic nanoparticles (MNP) containing magnetite and other MNP (Ni, Cu–Ni) in the layers and planar cells with Al electrodes is studied. For soluble polymers (polyvinylpyrrolidone and polyvinyl alcohol) containing 1–10 wt % of magnetite MNP, a substantial effect of MNP on surface conductivity is detected over a wide range (from 10^–10 to 10^–3 Ω^–1). It is shown that the addition of magnetite MNP not only results in a considerable change in cell conductivity, but also leads to its partially irreversible variation (by an order of magnitude or more) via minor modifications of the experimental conditions (temperature, electric field). For high-resistance samples with low probabilities of conducting chain formation, temperature current peaks are observed upon moderate heating (up to 350 K). These peaks are similar to the maxima observed upon polymer electret thermodischarges when the charges are captured by the deep centers associated with separate MNP or MNP aggregates. The type and position of the maxima are determined by the characteristics of the polymer matrix. For polyvinylpyrrolidone composites, the maxima are observed some time after heating (the echo effect). With composites based on solventborne polymers (polyalkanesterimides, soluble polyimide) and Ni, Cu–Ni MNP, no change in film conductivity measured electrophotographically is observed, due to the formation of a dielectric coating formed by polymer macromolecules adsorbed on the MNP surface. An explanation based on the possible formation of magnetic aggregates of magnetite MNP and conducting chains is proposed. Magnetic aggregation IPM is proposed as one way of controlling cell conductivity.

The plasmon effect that silver nanoparticles have on the luminiscent and generation properties of rhodamine 6G molecules in aqueous alcohol solutions is studied. It is found that the intensities of absorption and emission increase when silver nanoparticles are added to aqueous solutions of rhodamine 6G. It is shown that upon the laser photoexcitation of aqueous solutions of rhodamine 6G dye, spontaneous fluorescence occurs that is converted into stimulated laser emission as the pump power grows. It is found that an increase in intensity and a drop in the generation threshold of stimulated emission are observed when silver nanoparticles are added to a solution of rhodamine 6G. It is shown that the dependence of absorbance, the intensity of fluorescence, and the dye’s generation of stimulated emission on the concentration of silver nanoparticles in solution falls as the proportion of alcohol grows.

Silver nanoparticles have been prepared and tested for their ecotoxicity using daphnids as a hydrobiotic test. The toxicity was supposed to originate from Ag⁺ ions released into the aqueous solution. Also, the toxicity of the stabilizing agent was found to be comparable to that of silver nanoparticles.

A material with porous structures formed by jointed aza- and oxa-aza-crowns with peripheral OHgroups is synthesized on the basis of cellulose fabric and PVC transformed into hydroxyethylcyclam. Mesopores are mainly observed on the fiber surface. The specific surface of the material is 6 m²/g; the volume of free space is 0.112 cm³/g. Assuming the internal pores have a disk-like shape, their width is estimated at 2 nm. The material sorbs vapors of aliphatic and aromatic hydrocarbons, alcohols, aldehydes, ketones, amines, amides, nitriles, and sulfoxides. It also swells to a limited degree in organic solvents. When sulfuric acid or sodium hydroxide is sorbed in the pores, compounds of them with H⁺- and OH^–-conducting systems of hydrogen bonds are formed.

Synthetic ligands carrying a positive charge and capable of selective binding of bacterial endotoxins are covalently immobilized on surfaces of domestic hemosorbent Styrosorb-514 based on hypercrosslinked polystyrene. It is shown that the resulting sorbent aimed at treating sepsis exceeds imported specific hemosorbent in Toraymyxin™ columns in removing lipopolysaccharides, and can be used in domestically-produced Desepta columns.

Regularities of the sorption of 1,2,3,4-tetrahydroquinoline derivatives on octadecylsilyl silica gel and porous graphitic carbon from aqueous acetonitrile solutions were investigated. The effect the molecular structure and physicochemical parameters of the sorbates have on their retention characteristics under conditions of reversed phase HPLC are analyzed.

The mobility of ions in binary iron-based liquid metal systems is calculated for the first time, based on studies on the specific resistance and self-diffusion coefficient in a wide range of concentrations. It is established that iron ions move toward the anode in Fe–V and Fe–Mo systems, and toward the cathode in Fe–W and Fe–Pt systems; i.e., there is inversion of electrotransport for iron ions. When the concentration of a component is reduced, the mobility of its ions grows in modulus.

The kinetics and mechanism of chemiluminescence during the reduction of manganese(IV) ions with lactic acid in an H₂SO₄–AcOH medium are studied. Kinetic spectrophotometric measurements are used to determine the profiles of change in the concentrations of Mn(IV) and Mn(III) ions during the reaction. The results from kinetic spectrophotometric measurements are compared to the light yield kinetics. The quantum chemiluminescence and chemiexcitation yields reach record values.

Atomic displacement energy Δε_e in multicomponent sheet and lead-silicate glasses is calculated from the free activation energy of a viscous flow. The value of Δε_e is shown to remain constant in a rather wide range of temperatures in the glass transition region. Satisfactory agreement with calculations of Δε_e using the current formula incorporating the glass transition temperature and the fluctuation volume fraction frozen at this temperature is obtained. The validity of the above formula not only at the glass transition temperature but also in the temperature region adjacent to it is confirmed.

The formation of complexes of nickel(II) with L-homoserine at 298.15 K and ionic strengths I = 0.5, 1.0, and 1.5 (KNO₃) are investigated by potentiometry and calorimetry. Standard characteristics of studied equilibria (log K°, Δ_rG°, Δ_rH°, and Δ_rS°) are determined.