卷 91, 编号 13 (2017)

V₂O₅/S-doped TiO₂ was prepared by the sol-gel and impregnation methods. The adsorption of NO, NH₃, and O₂ over the catalyst was studied by in situ DRIFTS spectroscopy to elucidate the reaction mechanism of the low-temperature selective catalytic reduction of NO with NH₃. Exposing the catalyst to O₂ and NO, three types of nitrates species appeared on the surface. The introduction of S to TiO₂ could generate large amounts of acid sites for ammonia adsorption on the catalyst, which was believed to be an important role in the SCR reaction and hereby improved the catalytic activity. The results indicated two possible SCR reaction pathways for catalyst. One was that NO was absorbed to form nitrite species, which could react with NH₃ on Lewis acid sites, producing N₂ and H₂O. Another way was that NH₃ was adsorbed, then reacted with gas phase NO (E–R) and nitrite intermediates on the surface (L–H).

Various thermo-acoustical parameters of 1,4-dioxane, tetrahydofuran and ethylacetae solutions of 1,1′-bis(4-isopropyloxyacetylphenoxy)cyclohexane were determined at different temperatures using density, viscosity and ultrasonic speed and correlated with concentration. Linear increase of ultrasonic speed, specific acoustical impedance, Rao’s molar sound function, Van der Waals constant and free volume with concentration C and decreased with temperature. Linear decrease of adiabatic compressibility, internal pressure, intermolecular free path length, classical absorption coefficient, and viscous relaxation time with concentration and increased with temperature indicated existence of strong molecular interactions in solutions and further supported by positive values of solvation number. Gibbs free energy of activation decreased with C in all three systems. It is decreased with T in 1,4-dioxane, while increased in tetrahydrofuran and ethyl acetate. Both enthalpy of activation and entropy of activation are increased gradually with C in 1,4-dioxane, while they are negative and remained practically independent of concentration in 1,4-dioxane and tetrahydofuran systems.

The dissolution enthalpy and entropy of thiourea in ethanol have been calculated from solubilities of thiourea in ethanol at the mass fractions 0.54–0.88 and temperatures 292–320 K. The data can be used for the synthesis of isopropyl mercaptan.

By the conductivity measurements the effects of fructose and temperature (293–308 K) on the micellization of a cationic gemini surfactant (GS), pentanediyl-1,5-bis(dimethylcetylammonium) bromide in aqueous solutions have been investigated. The critical micelle concentration (CMC) of GS was measured at the different temperatures and fructose concentrations. An increasing trend of the CMC values is with addition of fructose. With increasing temperature, the CMC values are in a similar increasing trend. The CMC of GS by dye solubilization method at room temperature have been determined. The standard Gibbs energy, enthalpy and entropy of GS micellization have been evaluated. From these thermodynamic parameters, it was found that in presence of fructose, the stability of the GS aqueous solutions decreases.

The absorption feasibility of benzene molecule in the C₂₄, Si@C₂₄, Si-doped C₂₄, and C₂₀ fullerenes has been studied based on calculated electronic properties of these fullerenes using Density functional Theory (DFT). It is found that energy of benzene adsorption on C₂₄, Si@C₂₄, and Si-doped C₂₄ fullerenes were in range of –2.93 and –51.19 kJ/mol with little changes in their electronic structure. The results demonstrated that the C₂₄, Si@C₂₄, and Si-doped C₂₄ fullerenes cannot be employed as a chemical adsorbent or sensor for benzene. Silicon doping cannot significantly modify both the electronic properties and benzene adsorption energy of C₂₄ fullerene. On the other hand, C₂₀ fullerene exhibits a high sensitivity, so that the energy gap of the fullerene is changed almost 89.19% after the adsorption process. We concluded that the C₂₀ fullerene can be employed as a reliable material for benzene detection.

In this paper, using the B3LYP functional and CCSD(T) method with 6-311++G** basis set, the harmonic and anharmonic rate constants in the unimolecular dissociation of ethyl propanoate have been calculated using Rice–Ramsperger–Kassel–Marcus theory. The anharmonic rate constants of the title reaction have also been examined, the comparison shows that, the anharmonic effect especially in the case of high total energies and temperature for channels 3 to 6 is significant, so that the anharmonic effect cannot be neglected for unimolecular dissociation reaction of CH₃CH₂C(=O)OCH₂CH₃ both in microcanonical and canonical systems.

Complexatio of the La³⁺ cation with 1,13-bis(8-quinolyl)-1,4,7,10,13-pentaoxatridecane(Kryptofix5) was studied in pure solvents acetonitrile (AN), methanol (MeOH), nitrobenzene (NB), tetrahydrofuran (THF), methyl acetate (MeOAC) and in various binary solvent mixtures of AN–MeOH, AN–NB, AN–THF, and AN–MeOAC systems at different temperatures using the conductometric method. The stoichiometry of the complex was found to be 1 : 1 (ML). In all cases, the variation of the log kf with composition of the solvent was non-linear. This behavior is probably due to a change in the structure of these binary mixed solvents as the composition of the medium is varied. The stability order of the complex in pure nonaqueous solvents at 25°C increases in the order: AN > THF > MeOAC > MeOH > NB. The values of thermodynamic data (ΔH_c°,ΔS_c°) formation of (Kryptofix5.La)³⁺ complex are definitely solvent dependent.

In terms of FTIR study it was estimated that water forms the complexes with furan, thiophene, dichloromethane, tribromomethane in low temperature films at 90–150 K interval and with benzene in KBr matrix at ambient temperature. The mechanism of intermolecular interaction was simulated by ab initio calculation using DFT method. It was shown that complex formation occurs due to arising of hydrogen bond between hydronium ion of water cluster or single water molecule with organic components.

A model was developed that can be used to study the effect of gradual cholesterol intake by food on the HPA axis dynamics. Namely, well defined oscillatory dynamics of vital neuroendocrine hypothalamic-pituitary-adrenal (HPA) axis has proven to be necessary for maintaining regular basal physiology and formulating appropriate stress response to various types of perturbations. Cholesterol, as a precursor of all steroid HPA axis hormones, can alter the dynamics of HPA axis. To analyse its particular influence on the HPA axis dynamics we used stoichiometric model of HPA axis activity, and simulate cholesterol perturbations in the form of finite duration pulses, with asymmetrically distributed concentration profile. Our numerical simulations showed that there is a complex, nonlinear dependence between the HPA axis responsiveness and different forms of applied cholesterol concentration pulses, indicating the significance of kinetic modelling, and dynamical systems theory for the understanding of large-scale self-regulatory, and homeostatic processes within this neuroendocrine system.

This paper presents results concerning optical and electrical properties of galena natural mineral and of the interface layer formed between it and the potassium ethyl xanthate solution. The applied experimental method was differential optical reflectance spectroscopy over the UV–Vis/NIR spectral domain. Computations were made using the Kramers–Kronig formalism. Spectral dependencies of the electron loss functions, determined from the reflectance data obtained from the polished mineral surface, display van Hove singularities, leading to the determination of its valence band gap and electron plasma energy. Time dependent measurement of the spectral dispersion of the relative reflectance of the film formed at the interface, using the same computational formalism, leads to the dynamical determination of the spectral variation of its optical and electrical properties. We computed behaviors of the dielectric constant (dielectric permittivity), the dielectric loss function, refractive index and extinction coefficient, effective valence number and of the electron loss functions. The measurements tend to stabilize when the dynamic adsorption-desorption equilibrium is reached at the interface level.

Recently, polymeric materials have been filled with synthetic or natural inorganic compounds in order to improve their properties. Especially, polymer clay nanocomposites have attracted both academic and industrial attention. Currently, the structure and physical phenomena of organoclays at molecular level are difficultly explained by existing experimental techniques. In this work, molecular dynamics (MD) simulation was executed using the CLAYFF and CHARMM force fields to evaluate the structural properties of organoclay such as basal spacing, interlayer density, energy and the arrangement of alkyl chains in the interlayer spacing. Our results are in good agreement with available experimental or other simulation data. The effects of interlayer cations (Na⁺, K⁺, Ca²⁺), the cation exchange capacity, and the alkyl chain length on the basal spacing and the structural properties are estimated. These simulations are expected to presage the microstructure of organo-montmorillonite and lead relevant engineering applications.

Functionalization is an important method to change electrical and thermodynamic properties of carbon nanotubes. In this study, the effect of functionalization of a single-walled carbon nanotube (SWCNT) was investigated with the aid of density functional theory. For this case, a (5, 0) zigzag SWCNT model containing 60 C atoms with 10 hydrogen atoms added to the dangling bonds of the perimeter carbons was used. To model hydroxyl CNT two terminal H atoms were replaced by two –OH groups. All the functionalized CNTs are thermodynamically more stable and have higher dipole moment with respect to the pristine CNT. Depending on the positions of hydroxyl groups on CNT five isomers of C₆₀H₈(OH)₂ were obtained. The structure of these five isomers and molecular properties such as the HOMO–LUMO gaps, the dipole moments, and the density of state were calculated. Our results indicate that the HOMO–LUMO gap strongly depends on the placement of the hydroxyl groups on the nanotubes. The isomers were hydroxyl groups locate on the anti-position show the highest distortions in the structure of the CNT.

Co-doped ZnAl₂O₄ nanoparticles were prepared by hydrothermal method. The samples were characterized by XRD, HRTEM, EDX, FT-IR, XPS, PL, and UV–Vis, and the effects of cobalt doping on the microstructure and optical property of the samples were studied. The experimental results showed that Co-doped ZnAl₂O₄ nanoparticles synthesized by this method are single phase with cubic crystal structure, no other impurity phases were observed. Furthermore, with increasing the Co²⁺ concentration, the average crystallite size of the Co-doped samples became smaller. The absorption bands in FT-IR spectra are broadened in the low frequency region, the PL spectra had the red-shift and the UV–Vis peaks intensity gradually enhanced.

Core-shell structured Fe₃O₄@PPy microspheres are synthesized successfully through a facile polyol reduction method in combination with a modified Stöber method. We show that the as-prepared Fe₃O₄@PPy microspheres with high saturation magnetization, superparamagnetism, and good dispersibility have a high efficient adsorption capacity for high efficient removal of Pb(II) ions of up to 391.71 mg g–1 and a fast adsorption equilibrium time of 20 min. Furthermore, the lead-adsorbed Fe₃O₄@PPy microspheres can be rapidly separated from solution because of the excellent superparamagnetic properties. The composite Fe₃O₄@PPy microspheres are characterized using X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM). The adsorption data from our experiments show that the adsorption process fits well with the pseudosecond- order kinetic model and the adsorption isotherm follows the Langmuir isotherm model. The thermodynamic studies show that the adsorption of Pb(II) on Fe₃O₄@PPy microspheres is an endothermic and spontaneous process. Comprehensive comparison among adsorbents for the removal of Pb(II) ions that literature reported, reusability, high adsorption efficiency, fast adsorption equilibrium, and rapid magnetic separation make these Fe₃O₄@PPy microspheres very promising application for removal of Pb(II) ions from contaminated water.

We report the synthesis of electrochemically active LiMn₂O₄ nanoparticles at varied temperature and pH values by sol–gel method using urea as a chelating and combusting agent. The effect of pH and annealing temperature on the structure, morphology and electrochemical performance was evaluated. The results obtained by XRD, SEM, TEM, and FTIR show that LiMn₂O₄ has uniform porous morphology and highly crystalline particles that can be obtained at pH 7.0 and 8.0 and at a relatively lower temperature of 600°C. Cyclic voltammetry measurements showed reversible redox reactions with fast kinetics corresponding to Li ions intercalation/deintercalation at 600°C at neutral pH 7.0. Charge/discharge studies carried out at a current rate of 40 mA g^–1 reveal that LiMn₂O₄ synthesized at 600°C and pH 7.0 has the best structural stability and excellent cycling performance.

Zinc oxide (ZnO) nanostructured materials have received significant attention because of their unique physicochemical and electronic properties. In particular, the functional properties of ZnO are owed to its morphology and defect structure. ZnO particles were successfully synthesized by chemical precipitation. CTAB (cetyltrimethylammonium bromide), BS-12 (dodecyl dimethyl betaine) and graphene oxide (GO) were selected as templates to induce the formation of ZnO, respectively. By varying the amount of surfactant added during the synthesis process, the structural properties and the crystalline phase of the synthesized nanospheres were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), ultraviolet and visible spectrophotometry (UV‒Vis). Simultaneously, photo catalytic degradation of Rhodamine B (RhB) was carried out under natural sunlight irradiation while ZnO or ZnO/GO particles were used as catalyst. GO is prone to induce formation of wurtzite hexagonal phase of ZnO. Compared with CTAB and BS-12, ZnO/GO composites had a remarkably photocatalytic degradation.

The physicochemical properties of initial formulation, that is anionic/amphoteric surfactants mixture SLES/AOS/CAB (sodium lauryl ether sulfate (SLES), α-olefin sulfonates (AOS) and cocamidopropyl betaine (CAB) at ratio 80 : 15 : 5) with nonionic surfactant of amine oxide type (lauramine oxide (AO)) in various concentration (1–5%) were studied. To characterize the surfactants mixture, the critical micelle concentration (CMC), surface tension (γ), foam volume, biodegradability and irritability were determined. This study showed that adding of AO in those mixtures lowered both γ and CMC as well as enhanced SLES/AOS/CAB foaming properties, but did not significantly affect biodegradability and irritability of initial formulation. Moreover, an increase in AO concentration has a meaningful synergistic effect on the initial formulation properties. All those results indicates that a nonionic surfactant of amine oxide type significantly improves the performance of anionic/amphoteric mixed micelle systems, and because of that anionic/amphoteric/nonionic mixture can be used in considerably lower concentrations as a cleaning formulation.