نشریه شیمی کاربردی روز
پیاپی 44 (پاییز 1396)

The present study demonstrates the electrocatalytic oxidation of methanol in an alkaline medium on the modified glassy carbon electrodes. A thin film of Cu-poly(4-methyl, 1, 2-di-amino benzene) on multi-walled carbon nanotubes (MWNTs) modified glassy carbon electrode was used as anode for electrooxidation of methanol in the alkaline medium. The electrochemical behavior and electrocatalytic activity of the electrode were characterized by using cyclic voltammetry. The modified glassy carbon electrode consisting of a thin film of poly(4-methyl, 1, 2-di-amino benzene) which was formed by electropolymerization process. The effects of various parameters such as copper concentration, time of electrodeposition, number of CVs for pretreatment of the modified electrode in an alkaline solution on the electrooxidation of methanol have been investigated and the optimum values of each factors were suggested. The anodic oxidation of methanol with the modified electrode occurred at 0.75 V vs. Ag/AgCl and the treatment of the voltammetric data showed it was a purely diffusion controlled reaction. The modified electrode exhibits good catalytic activity for the oxidation of methanol in the wide concentration range 0.21-0.4 M.

In this project, theoretical studies on structure and nature of C→E and E→M bonds in some N-heterocyclic carbene complexes with general formula [NHC→E2H4→M(CO)5]; (E=Ge, Sn, Pb),(M=Cr,Mo,W) at M06/def2-TZVP level of theory have been reported. The interaction energies of C→E and E→M bonds for latter complexes were calculated and the results showed that the interaction energy in the presence of same substituents and M atom was decreased from Ge to Pb. Also, the amount of charges of elements in the complexes, charge transfer and Wiberg bond indices were calculated through NBO analysis. The EDA analysis was also used to nature of evaluated bonds in the latter complexes with ADF packages. The results showed that the contribution of electrostatic character in mentioned bonds of complexes studied here is larger than covalent character.

A4 explosive, containing 96.5 wt. % RDX and 3.5 wt. % paraffin wax, is one of the main components in the ammunitions, and warheads of military rockets and missiles. In this work, the thermal behavior and the decomposition kinetics of this explosive has been studied experimentally by non-isothermal differential thermal analysis technique (DTA) and thermal gravimetric (TG) methods, under various heating rates (2.0-8.0 °C/min). Kinetic parameters such as activation energy and frequency factor and critical ignition temperatures for thermal decomposition of these explosives have been evaluated via the fitting-model and free-model methods, proposed by International Confederation for Thermal Analysis and Calorimetry (ICTAC). The results show a single thermal decomposition process for A4, with the integral fitting- model of [-Ln(1-α)]1/3, indicating an autocatalytic degradation with 3-dimensional diffusion mechanism. The mean kinetic parameters of activation energy (Ea) and A of exothermic decomposition of these explosives, calculated by Kissinger, Ozawa, Friedman and KAS methods, are near to 190.397 kJ/mol and 1.89E min-1. The kinetics results were used for the estimation of mass loss prediction of mentioned explosives and were statistically compared to experimental accelerated ageing consequences. By using this method, it is possible to be predicted the lifetime of explosives in the temperatures near to decompositions regions.

Contamination of drinking water by organic materials (humic acid) and biological contamination (E.coli) even in small amounts during the water disinfection process by chlorine cause to the formation of disinfection by-products those impacts on human and other creatures’ health. In this study the ability of TiO2 to remove humic acid and E.coli from contaminated water was investigated. At first, using scanning electron microscopy (TEM) and XRD, the properties of TiO2 nanoparticles were determined. The samples of water containing different amount of humic acid and E.coli and TiO2 were inserted in photoreactor under UV (30W) irradiation. The effect of operational parameters including light intensity, TiO2 dosage and time was investigated. The results of experiments were revealed that under suitable conditions ([TiO2]= 245 mg/L, light intensity= 140 W/m2 and time=85 min) more than 94% of absorption in 254 nm and 70% total organic carbon were removed. Also, the photocatalytic process caused to inactivate the E.Coli, effectively.

Tin nano oxides (II /IV) (SnO/SnO2) were synthesized via a Sol - Gel method by using SnCl2 salt and starch media. The structures of these oxides were characterized and investigated by some spectroscopic methods such as SEM, XRD, UV, FT-IR. The effect of calcination temperature on the particle size of Tin nano oxides was investigated. The average particle size of these nano oxides are 11.75 and 11.19 nm by calculation with Debye- Scherrer equation. In the other part of this work, we study the antimicrobial properties of the synthesized synthesized metal oxides. In the results, nano-sized SnO2 is a good antimicrobial compound in the range of 10 mg per ml on the Gram negative bacteria. Nano-sized snow has not and antibacterial activity. Also the nano-sized SnO2 can to prevent of the grouting some gram negative bacteria, such as, Pseudomonas aeruginosa PTCC 1214, Escherichia coli PTCC 1330, Klebsiella and Albixs Candida PTCC 5027.

In this research a novel and economic optical sensor for determination of benzaldehyde (BA), which is a dangerous oxidation product of benzyl alchol in injection pharmaceuticals, is introduced. The optode is based on immobilization of 2, 4- dinitrophenylhydrazine in a PVC membrane. The response of the proposed optode was based on the nucleophilic addition of 2, 4- dinitrophenylhydrazine to BA that cause an increase in absorbance at 366 nm. Different variables affect the optical signal such as pH of solution, compositions of the membrane components and type of plasticizer were optimized. A universal buffer solution with pH 2 and dibutylphthalate were used as optimum measurement media and plasticizer, respectively. Under the optimum conditions, the optode has a response time of 6 min, linear concentration range of 4.0 − 100.0 ppm of BA with a detection limit of 0.6 ppm. The influence of interfering compounds possibly found in injection formulations on the BA determination was studied. The results showed that the prepared optical sensor has good selectivity to BA. The proposed optode has a reversible response and good repeatability. This optode was successfully applied to assay benzaldehyde in sodium diclofenac and piroxicam ampoules.

Molecular dynamics simulation is an appropriate method for microscpoic modeling of materials and is widely used in several fields of science and technology. Experimental measurement of thermodynamic properties of many materials is not economic due to time consuming and high cost of instruments. Using simulation methods such as molecular dynamics, thermodynamic properties of these materials can be computed and compared with experimental data. One of the important arguments in molecular dynamics simulation is application of appropriate combination ruls for dissimilar pair interactions. In this study, volumetric properties of 1-butyl-3-methylimidazolium hexafluorophosphate inonic liquid, acetonitrile, and their mixture are studied by molecular dynamics simulation and using three different combination rules for dissimilar pair interactions. Then the results are compared with experimental data inorder to evaluate validity of the applied combination rules.

In two recent decades, nucleus independent chemical shift (NICS) criterion was used to gauge the amount of aromaticity of organic and inorganic compounds in a lot of publications. In this study, aromatic, nonaromatic and antiaromatic character in different rings of coronene (C24H12) ,corannulene (C20H10), sumanene (C21H12) and circumtrindene (C36H12) bowl-shaped nanostructures, which are fullerene (C60) substructures was evaluated by this criterion. In the first, structures were optimized at B3LYP/6-311(d,p) level of theory and then analytical frequency calculations were done at the same level to ensure achieving the correct structures. NMR calculations were also done at the same level of theory to determine the magnetic shielding tensors in order to calculating NICS and NICSzz at the polygon surface and 1 Å above and below it for different rings of each molecule. These parameters were used to discuss local aromaticity, nonaromaticity and antiaromaticity character and were also used to determining overall aromaticity character of aforesaid four molecules. Results showed that NICS or NICSzz values are more negative for concave face than convex face for each molecule. Average of the NICSzz for coronene, corannulene, sumanene and circumtrindene molecules are equal to -21.57, -7.46, -16.13 and -0.52, respectively, therefore coronene and sumanene are very aromatic, corannulene is slightly aromatic and circumtrindene is nonaromatic.

In this paper, simulation results coming from finite element modeling of three-channel plasmonic sensor are presented and discussed. Plasmons are highly sensitive to changes in the refractive index of their surrounding environment, which is essential in identifying a subject specimen. In this paper, the output power for a sample of breast cancer cells, as well as sensor’s ability in assessing disease progression is presented. The sensor has the ability to decipher up to thousandth digit and provides three plasmon resonance wavelengths for the subject material. This characteristic is one of the main advantages of this sensor, since it increases the accuracy of a diagnosis. Sensor resolution of 10.86% was calculated for disease progression. Furthermore, it will be shown that changes in sensor’s length and consequently, sample’s volume, will have no effect sensor’s sensitivity. The proposed sensor has characteristics that set it apart from other sensors.
1- because of its structure, with little damping, it can limit and concentrate the light in the fiber,
2- it can identify two materials simultaneously,
3- three resonance peaks can be obtained simultaneously for a unique material, hence increasing diagnosis accuracy,
4- it can sense changes in refraction index up to thousandth digit.

Kinetic of Fischer-Tropsch synthesis on Fe-K-SiO2 catalyst was investigated based on alkyl mechanism and using differential evolution opptimization algorithm. In order to calculate products distribution on the basis of polymerization mechanism of Fischer-Tropsch synthesis, the rate constants of elementary steps in the mechanism must be determined. Therefore, the differential evolution technique was used. Then, these kinetic parameters were used to calculate the products distribution of Fischer-Tropsch synthesis on Fe-K-SiO2 catalyst under different experimental conditions. The results show the efficiency and accuracy of computational method in calculation of rate constant of alkyl mechanism and therefore products distribution of Fischer-Tropsch synthesis.

In this study, the adsorption of gallic acid onto poly ( ethylene terephthalate ) fibers grafted 2-hydroxy propyl methacrylate and acrylamide as a new adsorbent has been achieved through batch technique. The effect of pH, adsorbate concentration, adsorbent dose, temperature and contact time were studied. The best condition of removal of gallic acid was recorded ( pH = 10.0 , t = 80 min, cation exchange capacity = 128 mg/L ). The adsorption data were best fitted by langmuir isotherm and pseudo-second order kinetic models, as well.

In this research, biosynthesis of Ag nanoparticle investigated using Urtica extract. Different parameter such as temperature, pH, time and concentration of Ag salt optimize for this goal. Synthesized nanoparticle characterized by Uv-vis, XRD and TEM methods. Results show Ag nanoparticle synthesized in the size of 10 nm. In continuous, Ag nanoparticle was used for preparation of modified carbon paste electrode. And its effect investigated on electron exchange system for K4[Fe(CN6)] as a standard system. The obtained result shows that synthesized nanoparticle can be improved electrical conductivity of electron exchange in electrochemical systems.

There has long been concern about the issue of contamination by heavy metal because of their toxicity for plant, animal and human beings and their lack of biodegradability. Lead has toxic effects on human health. Thus, determination of this element is often required in environmental samples. In this research, solvent-assisted dispersive solid phase extraction (SA-DSPE) combined with flame atomic absorption spectrometry, was used for determination of trace amounts of lead in drinking water samples.
In this approach, the dispersion of the sorbent was achieved by injecting a mixture of solution of the sorbent and disperser solvent into the aqueous sample. Thereby, a cloudy solution formed. The cloudy state resulted from the dispersion of the fine particles of the sorbent in the aqueous sample. The cloudy solution was centrifuged and the enriched lead in the sediment phase dissolved in ethanol and determined by flame atomic absorption spectrophotometer. Some effective parameters for SA-DSPE, such as: pH, concentration of chelating agent, type and amount of sorbent, type and volume of dispersive solvent and salt effect were investigated and optimized. Under the optimized conditions, the detection limit for lead ions was 12.6 µg/L. Calibration curve was made in the range of 20-400 µg/L, obtaining good linearity (R2 = 0.9981). Finally, SA-DSPE was successfully applied for trace determination of lead in drinking water samples. SA-DSPE is environment friendly and strong against high contents of salt. The other benefits of the method are its simplicity, ease of operation, good precision, short extraction time, low cost, and a good enrichment factor.

The aim of this study is to synthesis of silica aerogel by TEOS, H2O, isopropyl alcohol and n-heptane as solvent and catalyst solutions of HCl and NH4F by sol-gel method in different parameters including molar ratios of IAP/TEOS, Total H2O/TEOS ,TMCS/TEOS and CNH4F and concentration of NH4F in solutions. The density, porosity, and refractive index of products were determined and reported. Aging process and solvent exchange were performed using isopropyl alcohol and %11 volume percent of TMCS in heptane solution. All samples were dried at ambient pressure in oven at 60 and 170 oC temperature. The drying diagrams were plot for products. Produced amorphous silica aerogel had good transparence, low density of o.o566 g/cm3 and large surface area 802 m2/g. In addition, density, porosity, pore volume, and refractive index of all samples were determined and reported. Tests of BET, X-ray, SEM for determining of their structure were also performed. FTIR analysis results confirmed the surface modification of products. Surface charge of aerogel was determined and adsorptions of methyl orange, methylen orange, methyl blue and methylene blue on both at pH 1 and pH 7 using UV/Visible were carried out. The results showed that the adsorption is higher at low pH

This article presents new and sensitive method for the determination of trace amounts of Palladium (II) by dispersive liquid–liquid microextraction(DLLME) combined with UV–vis spectrophotometry. The method is based on the complex formation of Pd(II) with Eriochrom cyanine R and using chloroform as extraction solvent. Cetyl Trimethyl ammonium Bromide(CTAB) was used as disperser agent. The effective parameters such as solution pH, concentration of Eriochrom cyanine R, type and volume of extraction solvent, concentration of CTAB and time of centrifuge were investigated and optimized. The method yields a linear calibration curve in the concentration range of 0.050–1.600 µg mL -1 of Pd(II), and the limit of detection is 0.008 µg mL-1. The relative standard deviations for eight replicate determinations of 0.100 and 1.000 µg mL-1 of Pd(II) were 3.7 % and 1.4%, respectively. The proposed method was successfully applied to preconcentration and determination of Pd(II) in tea, soil and water samples.