Physical Chemistry Research
Volume:6 Issue: 4, Autumn 2018

Quantitative structure-activity relationship (QSAR) study on the piperidone-grafted mono- and bis-spirooxindole-hexahydropyrrolizines as potent butyrylcholinestrase (BuChE) inhibitors were carried out using statistical methods, molecular dynamics and molecular docking simulation. QSAR methodologies, including classification and regression tree (CART), multiple linear regression (MLR), principal component analysis (PCA) and principal component regression analysis (PCRA). Three descriptors in three classes: 3D-Morse, WHIM and GETAWAY descriptors were selected by SPSS software and then applied in the final tree structure to describe the inhibitory activities. Docking simulations were carried out using AutoDock Vina softwares for all inhibitors. Docking results showed that the studied BuChE inhibitors have two commons binding modes. Molecular dynamics results obtained by Gromacs showed that the more potent inhibitor has more interaction with the enzyme and higher effect on the enzyme structure.

FeCe nanoparticles were synthesized by simple co-precipitation method using Iron chloride hexahydrate (FeCl3.6H2O) and cerium chloride (CeCl2•5H2O) as precursors in the presence of cetyltrimethylammonium bromide (CTAB) surfactant. The samples were characterized by high resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), vibration sampling magnetometer (VSM), electron dispersive spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR) at different temperatures. The XRD results showed that Fe-doped CeO2 was single-phased with a cubic structure. SEM images showed the rod-shaped particles of as-prepared sample in the range size of 40-80 nm and annealed smallest one around 15 nm in diameter at 500oC for 3 h. The TEM studies revealed the squared-like shaped nanosized particles. The sharp peaks in the FTIR spectrum determined the element of Fe-Ce nanoparticles. The EDS spectra showed peaks of iron and cerium with less impurity in the prepared samples. The result of magnetic measurements showed a coercive field and saturated magnetization around 1650 G and 0.04 emu/g for as-prepared samples, respectively.

Reaction behaviors and kinetics of catalytic oxidation of toluene with different feed flows over Pt/Zr(x)-HMS catalysts with Si/Zr ratio equal to 5, 10, 20 and 35 were investigated over a wide temperature range (200 – 500 oC). Results show that Pt/Zr(x)-HMS performs more easily toluene oxidation. The kinetic data were fitted by the Power-law and Mars–van Krevelen kinetic models. The fitting results show that the Mars–van Krevelen model (R2 > 0.99) is more suitable for predicting the conversion of toluene than the Power law model (R2 = 0.53), and the Mars–van Krevelen model can accurately express the reaction rate of this process.

Visible light active graphitic carbon nitride/reduced graphene oxide/silver oxide nanocomposites with a p-n heterojunction structure were synthesized by chemical deposition methods. Prepared samples were characterized by different physico-chemical technics such as XRD, FTIR, SEM, TEM and DRS. Photocatalytic activity investigated by analyzing the Acid blue 92 (AB92) concentration during the time under visible light. Effects of pH, dye concentration, photocatalyst dosage and different scavengers on photocatalytic performance explored. Maximum photocatalytic degradation observed at pH=7. Silver nitrate among other scavengers demonstrated maximum activity for dye degradation. Photocatalyst with 400 ppm concentration showed the highest activity. Proposed mechanism and reaction kinetics discussed.

In this work, the results relating to the mean activity coefficient measurements for ionic liquid of 1- propyl -3 methylimidazolium bromide, [PMIm]Br in ethanol+ water mixtures have been reported using potentiometric measurements at T=( 298.2, 308.2 and 318.2)K. The electromotive force (emf) measurements were performed on the galvanic cell of the type:Br-ISE│[PrMIm] (m) ethanol (wt.%), H2O (1−wt) %│ [PrMIm] -ISE, in mixed solvent system containing 0, 10, 20, 30% mass fractions of ethanol over ionic strength ranging from 0.0010 to 2.0000 mol•kg−1. The Pitzer ion-interaction model was used to analyze the activity coefficients for studied system. The Pitzer ion-interaction parameters (β(0), β(1) and Cϕ) were determined and employed to calculate the mean activity coefficients, the osmotic coefficients and excess Gibbs free energies for the whole series the studied system.

Kombucha Scoby is a colony consisted from bacteria, yeast and cellulosic pellicle that present fantastic performances in various fields. Besides anti-toxicity and antimicrobial specifications of Kombucha scoby, this unique colony can be used for waste water treatment and removal of heavy metals. Herein, efficiency of graphene oxide/Fe3O4 nanoparticles (GO/Fe3O4) and Kombucha Scoby in the removal of Pb (II) from synthetic wastewater were examined and compared. The characteristics of GO/Fe3O4 nanoparticles were analyzed using FTIR and SEM. Moreover, the effect of significant parameters such as pH (1-7), temperature (10-60 oC) and amount of adsorbent (1-200 g/L) on the removal of Pb (II) ion from aqueous solution was investigated. Obtained results showed that the maximum adsorption efficiency was obtained at a temperature of 50 oC and adsorbent amount of 0.3 and 15 g using GO/Fe3O4 and Kombucha Scoby, respectively. Additionally, pHPZC values of 6.1 and 6.2 were obtained for GO/Fe3O4 and Kombucha Scoby, respectively. The maximum adsorption efficiency for GO/Fe3O4 and Kombucha Scoby were found to be 98.08 and 99.73 %, respectively. Likewise, the adsorption isotherm behavior of Pb (II) on adsorbents were investigated using Langmuir and Freundlich models. Achieved results showed that the Langmuir isotherm model was better fitted with experimental data. Furthermore, the maximum adsorption capacity by Langmuir model for GO/Fe3O4 nanoparticles and Kombucha Scoby were found to be about 114.9 and 126.6 mg/g, respectively. Generally, achieved results revealed that Kombucha Scoby, which is a cost affordable colony, can remove Pb (II) ions from water better than GO/Fe3O4.

In this work, an electrolyte-UNIQUAC model was developed by replacement of Boltzmann weight binary interaction parameters by the nonextensive Tsallis weight. A summation of the long-range electrostatic term (Debye-Huckel equation) and a short-range interaction term were considered in the calculation of thermodynamic properties. A framework proposed by Chen and co-workers was employed for the derivation of the local mole fractions. Application of the nonextensive theory increased the degree of freedom of the present model (T-E-UNIQUAC). Furthermore, the strength of the model lies in its ability to calculate individual activity coefficients of ions. The applicability of the T-E-UNIQUAC model has been tested using aqueous electrolyte solutions and results have been compared with Messnaoui, Chen and Pitzer models.

Nowadays, due to the decline in oil supplies on the one hand and raising the price of petroleum, on the other hand, countries have led to other sources of fuel and energy. The use of methods such as the production of light hydrocarbons from synthesis gas is highly regarded by the Fischer-Tropsch process, in these countries. This process is performed by heterogeneous catalysts, which consist of two parts. The first part is a catalyst support (generally porous and made of silica) and the second is an active phase, which is generally made of metal. In fact, the catalyst is the heart of Fischer -Tropsch process. In this study, iron-cobalt-cerium tri-metallic nano-catalyst based on silica was prepared by the wet impregnation method. The catalyst was tested in a fixed bed micro-reactor and a wide range of products was analyzed by GC technique. By increasing temperature, the CO conversion was increased and the efficiency of products was improved. Finally, the structure of nano-catalyst was characterized using the technique of scanning electron microscopy (SEM) to realize the particle size and surface properties of the catalyst.

The Fischer–Tropsch Synthesis (FTS) activities of cobalt-based catalysts supported on carbon nanotubes (CNTs) and functionalized carbon nanotubes (FCNTs) are investigated in this work. The cobalt-based catalysts are synthesized by the reverse micro-emulsion technique using a non-ionic surfactant, and characterized by the Brunauer-Emmett-Teller, X-ray diffraction, H2 chemisorption, temperature program reduction, and transmission electron microscopy techniques. The activities of the synthesized catalysts are evaluated in terms of the FTS production rate (g produced hydrocarbons /g.cat./h) and selectivity (percentage of the CO converted to hydrocarbon products). According to the TEM results, the synthesized cobalt nanoparticles have a narrow size distribution and are mostly confined inside the functionalized CNTs (FCNTs) . These nanoparticles are highly reducible as evidenced by the reduction peaks of the FCNT catalyst shifting to low temperatures. In comparison to non-functionalized CNT, FCNT increases the FTS rate and CH4 selectivity and decreases the C5+ selectivity as a catalytic support. In addition, the FCNT support preserves the high dispersion and reducibility of cobalt, which can be attributed to the hydrogen spill-over effect of the functional groups present on the CNT surface.

The present research investigated the impact assessment of modified rice bran as a heterogeneous catalyst and production of biodiesel from rice bran oil (RBO). Several variables including temperature, catalyst concentration, amount of methanol and reaction time were optimized in order to produce high quality RBO biodiesel with maximum yield. The results showed that obtained conditions for trans-esterification of RBO with methanol and carbon-based acidic heterogeneous catalyst were 65℃ reaction temperature, 6h reaction time, 10:1 molar ratio of RBO to methanol and 1.5%(w/w) catalyst. The produced rice bran oil methyl ester was suitable to be used as a fuel in engines. Considering the availability and renewability, methyl ester rice bran can be easily produced in large quantities as a sustainable and reliable energy resource for multi-functional applications.

The influence of Sodium dodecyl sulfate and Triton X-100 surfactants on the two-phase pressure drop and two phase flow regime of water-air and gas condensate-air in upward vertical pipe were investigated for various gas/liquid flow rates. Sodium dodecyl sulfate and Triton X-100 reduced the pressure drop of single phase water flow by 11% and 29% compared with that of pure water single phase flow at water velocity of 13 m/s. For condensate single phase flow, Sodium dodecyl sulfate and Triton X-100 reduced the pressure drop by 9% and 17% compared with that of condensate single phase flow with no surfactant at gas condensate velocity of 13 m/s. The maximum efficiency of Sodium dodecyl sulfate and Triton X-100 in reducing the pressure drop of water-air system were 67.1% and 79.8%, respectively, compared with that of pure water-air two-phase flow. For gas condensate-air system, the maximum efficiency of Sodium dodecyl sulfate and Triton X-100 in reducing the pressure drop was 57.1% and 36.7%, respectively, compared to that of pure condensate-air two-phase flow.

In this work, the interactions of the crocin and dimethylcrocetin (DMC) as anti-cancer drugs with a Dickerson DNA was investigated. Molecular dynamic simulations of Crocin, DMC and DNA composed of twelve base pairs and a sequence of the d(CGCGAATTCGCG)2 were executed for 25 ns in water. Binding energy analysis for each of the complexes in three definite parts of B-DNA showed that Van der Waals interactions are the most important part of energy. Crocin-DNA interactions are greater than that of DMC-DNA, due to a longer Π-conjugation. The most probable interactions were detected by Gibbs energy analysis, which shows that the stabilizing interactions of the DNA with crocin and DMC are located in the major and minor grooves of the DNA, respectively. In the case of DMC, the binding energy of the A-T rich sequence is more than that of G-C, which is different from crocin. Radial distribution function analysis showed that two sharp peaks of the CO…NH and HO…OC parts, during the complex formation at 2.16 Å and 2.28 Å, are related to the new hydrogen bond formation between DMC and crocin with DNA, respectively. Also, non-classical H-bonds were considered by taking part of the CH group of the drug with the OC and NC groups of the DNA, which play an important role in the stability of the DNA in the corresponding complex.

In this study, NiFe2O4 magnetic nanoparticles as adsorbent for zinc (Zn) were coated on sand particles. Adsorption studies were conducted to investigate the efficacy of contact time, pH, adsorbent dosage, initial zinc ion concentration and temperature on removal efficiency. To decide the most fitting kinetic model, the suitability of pseudo-first order and pseudo-second order model was compared and the most appropriate kinetic model was determined to be pseudo-second-order. Langmuir, Freundlich and Dubinin–Radushkevich isotherms were assessed and the most suitable isotherm was observed to be Langmuir model. The maximum adsorption capacity obtained from Langmuir model was 57.14 mg/g. The calculated thermodynamic parameters indicated the endothermic and spontaneous character of the adsorption process. In addition, the adsorbent can easily be removed by a simple filtration process.

In this study, Ag nanoparticles were loaded successfully into poly acrylic acid hydrogel (PAA) as a matrix to prepare PAA-Ag nanocomposite catalyst. The prepared catalyst was characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transform infrared spectrophotometer (FT‐IR), thermal gravimetric analyzer (TGA), inductively coupled plasma atomic emission spectrometer (ICP), and X‐Ray photoelectron spectroscope (XPS). The catalyst with NaBH4 was used to degrade some common pollutant dyes such as methyl orange (MO), rhodamine B (Rh. B), and methylene blue (MB) in water. UV-visible spectrophotometer was applied to determine the initial and final concentration of dyes. Some effective factors on degradation such as the amount of catalyst, the initial concentration of dye, time, and pH were investigated. The results demonstrated that the amount of catalyst equals to 0.02 and 0.03 g with 0.01 g of NaBH4 in 50 mL water, are appropriate to completely degrade 50 ppm of MO, Rh. B, and MB, respectively at pH=6.5 in less than 15 minutes.

Graphene is an anode material that is expected to be a good alternative for graphite to increase the capacity and rate-capability of lithium-ion batteries. Graphene synthesis is always accompanied by defects in the structure. The most common defect in graphene is the divacancy (DV) defect. In this study, the effect of this defect on the adsorption of lithium was studied by density functional theory method, and also the doping effect of silicon and germanium atoms on the defective graphene structure was investigated. The bandgap energy of DV-defected graphene, which has an inverse relationship with electrical conductivity, is steady with the addition of germanium, but decreases with the addition of silicon. In all cases, along with lithium adsorption, the bandgap energy is increased, so that the germanium doped compound has the highest bandgap and the structure with no doped atom has the least bandgap. However, the difference in the minimum and maximum bandgap in structures is very low. The results show that the addition of silicon and germanium leads to stronger adsorption of lithium which means it is possible to raise the charge-discharge capacity of graphene through doping with elements while the material still has a high charge/discharge capability.