Том 91, № 10 (2017)
- Год: 2017
- Статей: 39
- URL: https://journals.rcsi.science/0036-0244/issue/view/10340
Chemical Thermodynamics and Thermochemistry
Effect of diamond blend on the gas-separation properties of composite membranes
Аннотация
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.
Chemical Kinetics and Catalysis
Kinetics and mechanism of the reaction between aquacobalamin and isoniazid
Аннотация
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.
Kinetic characteristics of gas–liquid ozone reactions
Аннотация
An experimental chemical method for determining the kinetic characteristics (volumetric mass transfer coefficient and rate constant of a second-order reaction) of gas–liquid ozone reactions in a bubble column reactor is described. The calculation formulas are substantiated, and the ranges of values of the experimental factors that determine the method’s limits of applicability are found. The conditions under which the boundary-value problem of a gas–liquid ozone reaction of the second order can be reduced to a problem of a pseudo-first order reaction allowing an analytical solution are revealed.
Kinetics and mechanism of the condensation of pyridoxal hydrochloride with L-tryptophan and D-tryptophan, and the chemical transformation of their products
Аннотация
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.
Relationships between the activities of the growth centers of macromolecules in the TiCl4–Al(i-C4H9)3 catalytic system and the particle size of its catalytically active residue
Аннотация
The theoretical regularities of the physical modification of the TiCl4–Al(i-C4H9)3 catalytic system (dispersion of the particles of its catalytically active residue) in eddy flows created in a tubular eddy apparatus of diffuser confuser design were determined. The change in the particle size of the catalytically active residue of the TiCl4–Al(i-C4H9)3 catalytic system as a result of growth of macromolecules during the ion-coordination polymerization of butadiene (“wedging” effect) was described in terms of the probability theory. The relationships (at 298 K) between the activities of the growth centers of macromolecules in the TiCl4–Al(i-C4H9)3 catalytic system physically modified in eddy flows and not physically modified and the equivalent radius of the particles of its catalytically active residue were represented as functional dependences.
Using a modified Marcus model to analyze the Brønsted correlation of gas-phase reactions of the deprotonation of para-substituted toluenes by CH2Cl−, H(O)C−, CH3O−, H(F)N−, NH2C≡C−, and СH3C≡C− anions
Аннотация
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 (Eaeq) and nonequilibrium (Eaneq) contributions to energy of activation Eа 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 − Eaneq (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 − Eaneq are in agreement with the theory. The correlations of energies Eaneq, Eaeq, Eа, 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 Eaeq and the height of the proton tunneling barrier in the activated complex (AC) Eb. For the series of reactions of toluene with a set of bases, graphs ΔE00 − Eaeq and ΔE0 − Eb 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−).
Oxidation of white phosphorus by peroxides in water
Аннотация
A mixture of hypophosphorous, phosphorous, and phosphoric acids is formed during the anaerobic oxidation of white phosphorus by peroxides [ROOН; R = Н, 3-ClC6H4CO, (СН3)3С] in water. The rate of reactions grows considerably upon adding nonpolar organic solvents. The activity series of peroxides and solvents are determined experimentally. NMR spectroscopy shows that the main product of the reaction is phosphorous acid, regardless of the nature of the peroxide and solvent. A radical mechanism of oxidation of white phosphorus by peroxides in water is proposed. It is initiated by the homolysis of peroxide with the formation of НO∙ radicals that are responsible for the homolytic opening of phosphoric tetrahedrons. Further oxidation and stages of the hydrolysis of intermediate phosphorus-containing compounds yield products of the reaction.
Studies in stability constants of schiff base hydrazone complexes with transition metal ions. Effect of ligand on seed germination
Аннотация
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.
Synthesis and catalytic performance of ZSM-5/MCM-41 composite molecular sieve from palygorskite
Аннотация
ZSM-5/MCM-41 composite molecular sieve has been hydrothermally synthesized through a two-step crystallization process using palygorskite (PAL) as silicon and aluminum source. The products were characterized by various means and their catalytic properties for acetalization of cyclohexanone and esterification of acetic acid and n-butanol were also investigated. In the first step ZSM-5 zeolite could be formed from the acid-treated PAL after hydrothermal treatment using tetrapropylammonium bromide as template. XRD patterns, N2 adsorption and desorption data, and TEM images show that the composite obtained in the secondary step had a well-ordered mesoporous MCM-41 phase and a microporous ZSM-5 zeolite phase. Compared with ZSM-5, ZSM-5/MCM-41 composite possessed more total acid amount, weak acid sites and large pore structure due to the formation of MCM-41 and exhibited higher catalytic activity for the acetalization and esterification reaction.
Physical Chemistry of Solutions
Temperature and concentration dependences of the activity coefficients of electrolytes
Аннотация
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.
Transformations of methyl orange dimers in aqueous–acid solutions, according to UV–Vis spectroscopy data
Аннотация
The effect acidity has on the UV–Vis absorption spectra of azo dye methyl orange (MOD) in aqueous solutions of hydrochloric acid in the pH range of 1.7 to 7 and sulfuric acid in the 0.24 to 18 mol/L range of concentrations is investigated. The spectral transformations of MOD solutions are compared to the corresponding spectral transformations of solutions of dimethylaminoazobenzene (DAB), which is an azo dye akin to MOD. A close resemblance between the spectral transformations of MOD and dimers DAB2 is revealed. It is concluded that the ground state of MOD, like the ground state of DAB, consists of not individual molecules but of supramolecular dimers MOD2. It is found that dimers MOD2 in aqueous low-acidic solutions are reversibly protonated with the formation of di- and triprotonated forms, which reversibly dissociate into diprotonated monomers upon an increase in acidity. The structural formulas of the chromogenic groups responsible for the spectral transformations, and the mechanisms of their reversible transformations, are given.
The brilliant blue FCF ion-molecular forms in solutions according to the spectrophotometry data
Аннотация
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.
Hydration and dielectrical properties of aqueous pyrrolidinium trifluoroacetate solutions
Аннотация
Results from microwave measurements of the dielectrical properties of aqueous pyrrolidinium trifluoroacetate solutions at maximum water dispersion frequencies (13–25 GHz) and temperatures of 288, 298, and 308 K are given. The static dielectrical constants, times, and activation parameters of the dielectrical relaxation of solutions are calculated. The enthalpy and time of dielectrical relaxation activation are increased by deceleration of the motion of water molecules in the hydrate shells of ions. The changes in dielectrical parameters are in this case minimal in a series of aqueous solutions of diallylammonium salts with cations of different structures and degrees of substitution. It is shown that pyrrolidinium ions are characterized by weak hydrophobic hydration.
Features of polytherms of the viscosity of Fe–B melts
Аннотация
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.
Molecular interactions in aqueous solutions of polyborates at different acidity based on the Raman spectroscopy data at 25°C
Аннотация
Investigation of aqueous solutions of polyborates LiB(OH)4, Li2B4O5(OH)4, and LiB5O6(OH)4 at different acidity has been performed by Raman spectroscopy at 25°C. The geometries and Raman vibrational frequencies of H3BO3 in aqueous phase were calculated at different basis sets, and verified the veracity. The calculated characteristic Raman shifts of B(OH)3, B(OH)4−, B3O3(OH)4−, B3O3(OH)52−, B4O5(OH)42−, and B5O6(OH)4− were assigned to 880.0, 735.33, 599.06, 740.16, 551.67, and 521.04 cm−1, respectively. Assignments of the bands were tentatively ascribed by comparing the calculated Raman spectrum. The chemical species distribution and the relevant molecular interaction mechanisms in the polyborates solutions were suggested.
The phase and density diagrams of the systems MgCl2–MgB4O7–H2O and KCl–K2B4O7–H2O at 273 K
Аннотация
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.
Structure of Matter and Quantum Chemistry
Synthesis and properties of γ-Ga2O3–Al2O3 solid solutions
Аннотация
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.
“Chemical contraction” in rubidium–bismuth melts
Аннотация
The density and thermal expansion of liquid rubidium and rubidium–bismuth alloy containing 25.0 at % Bi were measured by the gamma-ray attenuation technique at temperatures from liquidus to 1000 K. The results of this study were compared with the data obtained by other authors. The molar volume of the Rb75Bi25 melt strongly deviates from the additivity rule for ideal solutions.
Effect of electron transition kinetics on the photomotor velocity
Аннотация
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.
Physical Chemistry of Nanoclusters and Nanomaterials
Surface tension of different sized single-component droplets, according to macroscopic data obtained using the lattice gas model and the critical droplet size during phase formation
Аннотация
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.
Metal-free current collectors based on graphene materials for supecapacitors produced by 3D printing
Аннотация
Supercapacitor (SC) current collectors with electrodes made of graphite oxide reduced during microwave exfoliation are produced from a commercial filament with a graphene component via layer-by-layer fusing with a 3D printer. The separator is made of a graphene oxide film. The current collectors are investigated by means of IR spectroscopy. Electrochemical tests are performed for the assembled SC that include tests of its cyclic stability up to 1000 cycles.
Temperature dependence of direct current conductivity in Ag-ED20 nanocomposite films
Аннотация
The effect of silver nanoparticles (NPs) in the concentration range of ≤0.8 wt % have on direct current conductivity σdc 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 σdc consists of two sections: above the glass transition temperature (Tg), the dependence corresponds to the empirical Vogel–Fulcher–Tammann law (Vogel temperature T0 does not depend on the NP concentration); below Tg, the dependence is Arrhenius with activation energy Ea ≈ 1.2 eV. In the region where T > Tg, the σdc 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 Tg.
Investigating the sensor response of ceria-containing binary metal oxide nanocomposites
Аннотация
The hydrogen sensing performance of ceria-containing nanocrystalline indium and tin oxides is investigated for different concentrations of added ceria. The sensor response of nanocrytsalline In2O3 is considerably enhanced at low CeO2 concentrations. In contrast, low levels of CeO2 cause a substantial drop in the sensor response of SnO2-based composite; at a 3 wt % level of added ceria, its hydrogen sensing ability is almost entirely suppressed. Possible causes of these effects are investigated via X-ray photoelectron spectroscopy (XPS) and X-ray diffraction. XPS data show that additions of CeO2 have different effects on the structure of the base oxides (In2O3 and SnO2), with implications for the hydrogen sensing performance of the composites.
Synthesis of SrFe12O19 magnetic nanoparticles by EDTA complex method
Аннотация
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.
A facile synthesis of azoviolet@Mn3O4 nanoparticles for supercapacitor
Аннотация
The azoviolet@Mn3O4 nanoparticles have been successfully synthesized using the azoviolet as a stable absorbed reagent for the supercapacitor. The prepared nanoparticles have been characterized by X-ray diffractometry, scanning electron microscopy, energy dispersive spectrometry, infrared spectrometry, surface area and pore size analysis. The cyclic voltammetry and galvanostatic charge/discharge measurements were performed in 1 M Na2SO4 aqueous solutions in a fixed voltage window of ~(0–1.00) V vs. Ag/AgCl. The specific capacitance at 1 A/g is 112.0 F/g. The azoviolets can improve the reaction areas of Mn3O4 nanoparticles in Na2SO4 aqueous solution for the supercapacitor.
Oxidation of ethanol on carbon-supported oxide-rich Pd–W bimetallic nanoparticles in alkaline media
Аннотация
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 Pd0.8W0.2/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.
Physical Chemistry of Surface Phenomena
Adsorption of proteins on γ-Fe2O3 and γ-Fe2O3/SiO2 magnetic materials
Аннотация
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.
Adsorption of organic molecules on a porous polymer surface modified with the supramolecular structure of melamine–cyanuric acid
Аннотация
The adsorption of organic molecules on the surface of a porous polymeric sorbent modified with a mixed cyanuric acid–melamine supramolecular structure is studied. The parameters of thermodynamic adsorption are considered and the contributions from intermolecular interactions to the Helmholtz energy of adsorption are assessed. Analysis of the molar changes in internal energy and adsorption entropy shows that the supramolecular structure formed on the surface could not exhibit dimension effects, indicating there were no cavities. The contributions from nonspecific interactions to the Helmholtz energy of adsorption generally fall, while those of specific interactions increase, indicating an increase in the polarity of the sorbent surface.
Donor–acceptor interactions between resonance-excited silver nanoparticles and halide ions in water solutions
Аннотация
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.
Physical Chemistry of Separation Processes. Chromatography
Nonlinear gas chromatography as a way of studying inhomogeneous sorbents
Аннотация
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.
Colloid Chemistry and Electrochemistry
Conductivity and electrochemical stability of concentrated aqueous choline chloride solutions
Аннотация
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.
Photochemistry and Magnetochemistry
Fluorescence of pyrene in the presence of silver nanoparticles on cellulose modified by surface-active substances
Аннотация
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.
Synthesis and characterization of Ln,Yb:BaGdF5 (Ln = Er, Ho) nanocrystals by hydrothermal method
Аннотация
The Er,Yb: BaGdF5 and Ho,Yb: BaGdF5 nanocrystal materials with the narrow particle size distribution was synthesized by a hydrothermal method at 180°C for 24 h. The phase structure and fluorescence properties were investigated by X-ray diffraction, scanning electron microscopy and up-conversion spectroscopy, respectively. The phase composition does not change with increasing the pH value, leading to the formation of a pure phase BaGdF5, while the solution was turbid state. The products show a good crystallinity, dispersion and uniform particle size distribution. Under the LD excitation at 980 nm, Er,Yb: BaGdF5 and Ho,Yb: BaGdF5 nanocrystal materials were researched in the visible range of the fluorescence spectrum. Er,Yb: BaGdF5 nanocrystals were achieved the launch of green, blue, and red. Ho,Yb: BaGdF5 nanocrystal with green and red light output were realized. The light-emitting belong to the two-photon transition process. And the possible mechanism for the corresponding up-conversion luminescence was also discussed. The Er,Yb: BaGdF5 and Ho,Yb: BaYbF5 nanocrystals with the narrow particle size distribution have potential applications in biological field as luminescence probes.
Investigation of the structural properties of annealed CdIn2Te4/CdS thin film solar cells produced by the electron-beam evaporation (e-beam) technique
Аннотация
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.
Other Problems and Physical Chemistry
Refractive properties of imidazolium ionic liquids with alanine anion [Cnmim][Ala] (n = 2, 3, 4, 5, 6)
Аннотация
Imidazolium ionic liquids with alanine anion, [Cnmim][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.
Short Communications
Kinetics of the photodecomposition of supramolecular alkynyl–phosphine complexes
Аннотация
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.
Stoichiometry of Zn(II)–heparin–glycine complex, determined using data from elemental and thermal analysis
Аннотация
Ternary polymer Zn(II)–heparin–glycine complex with the composition {Na3[ZnHepGly]·H2O}n, where Hep4− is the monomer chain of a heparin polyanion and Gly– is the chain of a glycine anion, is isolated in a solid state from a water solution, and is characterized via elemental and thermal analysis.
Ionic molecular interactions in solutions of cadmium salts in N-methylpyrrolidone in the presence of ions of alkaline-earth metals, determined using data from calorimetry and densimetry
Аннотация
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.
Thermodynamic characteristics of the acid–base equilibria of ethylenediamine-N,N′-diglutaric acid in aqueous solutions using calorimetric data
Аннотация
The enthalpies of reaction of betaine group neutralization of ethylenediamine-N,N'-diglutaric acid (H4L) at 298.15 K and at different values of ionic strength of 0.1, 0.5, 1.0 (KNO3) is measured by direct calorimetry. The standard thermodynamic characteristics of the protolytic equilibria of H4L are calculated.