نشریه شیمی و مهندسی شیمی ایران
سال سی و پنجم شماره 3 (پیاپی 81، پاییز 1395)

In this study, as a blue light source, colloidal germanium nanoparticles were synthesized by a simple method and their optical properties were also studied.Polyvinyl pyrrolidone as a surface modifier and the particle size controller was used. To investigate the optical properties of prepared nanoparticles, UV-Vis absorption, and emission spectroscopy were employed. Fourier Transform InfraRed (FT-IR) spectroscopy was used to determine the type of chemical bond. FT-IR spectrum indicates that the germanium nanocrystals are well passivated with minimal surface oxidation. TEM was used to confirm particle size and morphology.Experimental results showed that the synthesized Ge nanoparticles have a spherical shape with size variation between 5 to 10 nm. Germanium nanoparticles exhibit blue light-emitting with PL peak located at 445 nm. Also, the direct optical band gap of Ge colloidal nanocrystals was evaluated by Tauc's theory. The direct band gap energy value of Ge colloidal nanocrystals is equal to 3.12 eV. The crystallinity of Ge nanoparticles was also evaluated by X-ray diffraction pattern analysis.

Ag/Zn-TiO2 nanoparticles with various ratio moles were synthesized via two different sol-gel and hydrothermal. The prepared samples were characterized by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Energy-Dispersive X-ray (EDX) spectroscopy,N2 adsorption-desorption isotherm, and Brunauer-Emmett-Teller (BET) analysis methods. Also,the influence of synthesis method on the crystalline structure, crystal size, surface area and photocatalytic activity of synthesized nanoparticles were investigated. Photocatalytic activity of prepared nanoparticles was investigated by photocatalytic removal of Methyl Orange (MO) under black light irradiation. Ag/Zn-TiO2 nanoparticles synthesized by hydrothermal method showed high photocatalytic activity during removal of methyl orange due to having pure anatase phase, an increase in the specific surface area, total pore volume, and the decrease in the crystallite size and agglomeration.

The great challenge of many drug candidates in the pharmaceuticals industry is their low bioavailability due to the poor solubility and low dissolution rate in the different solvent, especially in water. Reduce drug particle size to nano size including a method that is effective in obviation this problem. In this study, the antisolvent precipitation technique with confined two- impinging jets is developed to prepare nanoparticles of Indomethacin to overcome its poor solubility in water.The influence of the operating parameters, such as stirring speed, quenching ratio, drug solution concentration and overallvolumetric flow rate, were also experimentally investigated. The results of Scanning Electron Microscopy (SEM)photomicrographs was revealed that by increasing of stirring speed from without stirrer to 400 and 1200 rpm, the particle size decreased from 215 to 88 nm. In the investigation of the effect of changes of quenching ratio from 1:1.5 to 1:5 and 1:12, it was seen the particle size decreased from 129 to 86 and 80 nm. Increasing of concentration parameter from 10 to 50 mg/mL showed the decrease in particle size from 98 to 77 nm with aggregation. The investigation results of overall volumetric flow rate was showed that as it was increased from 300 to 600 ml/min, the particle size was decreased from 95 to 86 nm. Furthermore, the results of Differential Scanning Calorimetry (DSC) analysis confirmed that the pure metastable srystal of a-form was effectively prepared by the two-impinging jets method and this can dramatically increase its solubility.

Today, generation and storage of energy are one of the important areas of researches. Like an electrochemical battery, Supercapacitors are used to store electrical energy. Supercapacitors have attracted a great deal of attention thanks to their great advantages such as high power density, no memory effect, long life cycle and good stability. However, low specific energy is still their primary limiting factor for their usage as the electrical storage devices in industrial and commercial applications. Graphene-based materials are promising materials for use in supercapacitor electrodes. Despite many advantages of the graphene-based electrode, the major limitation of the low quantity of specific capacitance due to their low quantum capacitance remain. We explored the variations of quantum capacitance of graphene-based electrodes by functionalization and making defect. Overall, our results demonstrate that with creation of structural defects on functionalized graphene, a significant improvement in electrode capacity will be achieved. Some structural defects increase the capacity at the high voltage magnitudes. In contrast, some other structural defects increase the capacity at the lower voltage magnitudes. So, we could design the asymmetric Supercapacitors with high capacity using clever combination of functionalized graphene and structural defects.

Heterocyclic compounds containing two heteroatoms in the structure are well known molecules with diverse biologically activities. Among them, thiazoles, thiazolidines, thiazolidinones and thiazolones are the most important scaffolds associated in the structure of many naturally occurring biological active compounds. A simple and efficient procedure for the synthesis of 4-arylidene-2-alkylthio-4H-thiazol-5-ones, the thia analogue of azlactones, via the condensation reaction of an aldehyde with an amino acid based dithiocarbamate is described. Also the bis [2-(alkylthio)-thioazlactone] was prepared using terephthaldehyde. High to excellent yields of products, simple reaction procedure and synthesis of complex molecules with simple starting materials are the most advantages of this protocol.

3,6-Diphenylpyrazin-2,5-dione was prepared in two steps from reaction of phenylglyoxal monohydrate with ammonium acetate in water at room temperature, followed by subjecting with hydroxyl amine hydrochloride in the presence of NaOH in a mixture of EtOH/water under reflux conditions, and used as an efficient ligand in palladium catalyzed Heck reaction between aryl halides and various alkenes. The products were obtained in good to high yields.In addition to FT-IR and NMR, the structure of the ligand was also confirmed by single crystal X-ray crystallography. Easy preparation, inexpensiveness, and stability in air and moisture are the main advantageous of this ligand.

In this work, we synthesized a new thiophene derivative Schiff base as new luminophore. The aim of this study was determination of fluoride using 2-[(E)-(2-Hydroxy-4-methoxybenzylidene) amino] -4, 5, 6, 7- tetrahydro-1-benzothiophene-3-carboxamide [Ligand L] as new and intense fluorescence sensor by spectrofluorometric method. In this method, we optimized all reagents concentrations such as ionic, pH, luminophore concentration. Afterwards, we used a new fluorimetric method for determination of fluoride ion based on quenching effect of fluoride ion on fluorescence of thiophene derivative schiff base, as new luminophore. Despite previous methods, that had less selectivity and sensitivity, in this work we presented a new sensitive fluorimetric sensor for determination of fluoride with good selectivity, sensitivity and reproducibility. A linear calibration range was obtained from 4.31×10-6 – 4.70×10-4. The relative standard deviation was very good (1.098% for 10-4 M of F- and n=5) and the detection limit was acquired 2.1×10-6 M. In addition, interference of some anions and cations were investigated. The proposed method was successfully applied for the determination of fluoride in toothpaste samples.

Water gas shift reaction is an essential process of hydrogen production and carbon monoxide removal from syngas. In this research, noble metal (Rh, Pt, Pd, Ir, and Ru) nanocatalysts supported on alumina stabilized with magnesium oxide were prepared and employed in high temperature water gas shift reaction for production of hydrogen. The prepared samples were characterized by X-Ray Diffraction (XRD), N2 adsorption (BET), Temperature Programmed Reduction (TPR), H2S chemisorption and Transmission Electron Microscopy (TEM) techniques. The obtained results revealed that the prepared samples showed the BET surface area in the range of 85-179 m2/g. The TEM analysis results showed that the catalysts have a nanocrystalline structure with average crystal size of less than 5 nm, which is in agreement with H2S chemisorption results for measuring the active metal crystallite size. The obtained results indicated that among the prepared catalysts, Ru and Rh showed higher CO conversion due to undesirable methanation reaction. In addition, it was found that amount of methane formation was negligible over Pt catalyst, which implied that all converted carbon monoxide over this catalyst is related to the water gas shift reaction. This catalyst also exhibited stable catalytic performance without any decrease in CO conversion during 10 h time on stream.

A new and rapid methodology has been developed and applied successfully for the determination of trace levels of palladium in real water samples. This technique is based on the combination of In-Syringe Dispersive Liquid-Liquid microextraction (IS-DLLME) and micro-volume UV–Vis spectrophotometry. All extraction, preconcentration and separation steps were performed in a convenient 10-mL glass syringe. By means of a 1-mL syringe, a mixture of rhodanin (complexing agent), benzyl alcohol (extraction solvent) and ethanol (dispersive solvent) was injected rapidly into the sample solution through the tip of 10 mL syringe which leads to the complexation of palladium and its extraction into the alcoholic phase. The extractant containing the target analyte was then transferred into UV-Vis spectrophotometer for analysis versus standards which were made in the same manner as the analyte. In order to prevent of precipitation of rhodanin, cetylpyridinum chloride surfactant was added to the aqueous samples before extraction. The factors influencing the extraction efficiency such as type and volume of extracting and disperse solvent, pH and volume of the sample and amount of ligand and surfactant were investigated and optimized. The developed protocol was found to have a linear calibration curve in the concentration range between 120 - 2000 µg/L with a limit of detection of 75 µg/L. Excellent enrichment factor of 44.8 fold was observed for the analyte. The repeatability of the method was satisfactory (RSD≤ 5.81%) and the total analysis time including microextraction was less than 10 min. The method has been successfully applied for the analysis of palladium in three spiked tap, lake and treated water samples.

In this paper, we investigate structure and electronic properties such as lattice constant, bulk modules, compression, energy band structure also states and electronic density of the semi-conductor MgSe in hexagonal phase for B4 structure .We Calculate those mentioned above by applying the Full Potential-Linearized Augmented Plane Wave (FP-LAPW) method in the framework of Density Functional Theory (DFT) and by applying Wein2k-08 package. The obtained results showed the existence of energy gap straight 2.7 eV in Γ point. And also an ionic feature for this compound that is one of the properties of the II-IV group and being compatible enough with other experimental and theoretical results.

The current work considers the study of the application of polyacrylamide compounds in order to reduce and control seepage and water infiltration and also soil stabilization in the unlined earthen canals. Polyacrylamide compounds are a family of polymers with a wide range of physical and chemical properties. Of these compounds which being considered
in the design and supervision of current research and of which so far not reported any risks regarding human health, are those water soluble hybrid inorganic- organic compounds that could be used in reducing seepage through earthen unlined canals and other water conveying structures. However, this could easily be possible when these polymeric compounds in a known concentration and as combined with appropriate inorganic elements inside upstream channel parameters are applied on these structures, it transform into structures that could deposit on the bottom and sides of the channel, creating a layer impermeable to water.

One of the industrial problems is the phenomenon of wax precipitation of oil fractions. One of the ways to prevent wax precipitation is the use of chemical inhibitors to reduce the pour point. Studying the effect of additives on specific oil samples could help in solving the wax precipitation problems at various oil processing stages. Despite the studies that have been done, finding materials that can decrease the pour point and be economically acceptable from one view, and well optimized and acceptable from other chemical and environmental view is still an unsolved problem. So it’s important to use effective materials that can act on preventing wax precipitation,or on decreasing the amount of precipitate, thus as a result it can decrease the pour point temperature. In this study, the effect of industrial polymer additives and surfactants which are economically acceptable on the decrement of pour point temperature was studied using three oil products samples: light diesel, heavy diesel and the fuel oil, products of Esfahan Oil Refining Co. In this study, optimized type and concentration of additive was studied before additive was chosen. The results showed that the copolymer ethylene vinyl acetate 28% at a concentration of 500 ppm reduced the pour point temperature by 12°C for diesel, also the copolymer ethylene vinyl acetate 19% at a concentration of 300 ppm reduced the pour point temperature by 9°C for fuel oil. Also results of this study showed ethylene vinyl acetate copolymer can be used as the pour point depressant of diesel and fuel oil instead of kerosene and other refinery products.

In this paper, a model-based predictive control for hybrid systems based on the class of Piece Wise Affine (PWA) model is presented. Hybrid systems contain two distinct types of components.These components are subsystems with continuous and discrete dynamics which interact with each other. Optimal control methods for controlling these systems have the largest share which among them; model predictive control is considered more. The controller presented in this way has all the characteristics of classic predictive control and due to the quadratic programming method to solve the optimization problem, the calculation is easy. The control method proposed in this paper is designed based on Generalized Incremental Predictive Control (GIPC) and Piece Wise Affine (PWA) model. This method is applied on a pH neutralization process and is simulated using MATLAB software. The simulated results have confirmed the appropriate operation of the controller in facing of set point changes and buffer flow variations.