Ardabil, Iran

University of Mohaghegh
Ardabil, Iran
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In this study, the TNT-imprinted polymer shell was created on nano-sized Fe3O4 cores in order to construct the nano-sized magnetic molecularly imprinted polymer (nano-MMIP). For this purpose, the surface of the synthesized magnetic nanoparticles was modified with methacrylic acid. The modified particles were then utilized as the core on which the TNT-imprinted polymeric shell was synthesized. The synthesized materials were then characterized by scanning electron microscopy, FT-IR and thermal gravimetric analysis (TGA). The resulting nano-MMIP particles were suspended in TNT solution and then collected on the surface of a carbon paste electrode via a permanent magnet, situated within the CP electrode. The extracted TNT was analyzed on the CP electrode by applying square wave voltammetry (SWV). It was found that the oxidative signal of TNT is much favorable for TNT detection on the resulting magnetic carbon paste electrode. The electrode with nano-MMIP showed distinctly higher signal to TNT, compared to that containing magnetic non-imprinted polymer (MNIP) nanoparticles. All parameters influencing the method performance including extraction pH, extraction time and sorbent amount were evaluated and optimized. The developed method showed a dynamic linear concentration range of 1.0-130.0nM for TNT measurement. The detection limit of the method was calculated to be 0.5nM. The method showed appropriate capability for TNT analysis in real water samples. © 2014 .

A new molecularly imprinted polymer material having urea molecule selective cavities was introduced. Urea was properly dissolved in acetonitrile in the presence of an acidic functional monomer. Molecularly imprinted polymers with different compositions were examined and the roper formulation was selected. It was shown that the MIP had a considerable selectivity for urea in comparison to similar compounds such as thiourea and hydroxyurea. The obtained polymer was used as an adsorber for solid phase extraction (SPE) of urea in the aqueous samples. The extracted urea was determined by using a spectrophotometric method. Different parameters of SPE were optimized and the developed procedure was used for urea determination in real samples. The calibration graph of the method was linear in the range of 0.6-8.3μmolL-1. The detection limit was calculated to be 0.14μmolL-1. © 2010 Elsevier B.V.

In this work, recognition of target molecules by nano- and micro-sized molecularly imprinted polymers (nano-MIP and micro-MIP) was investigated by using electrochemical impedance spectroscopy (ESI). Modification of carbon paste electrode (CP) with promethazine (PMZ)-imprinted and non-imprinted polymers (MIP and NIP) influenced its ESI behavior, in both low and high frequency regions, approximately in the same manner. However, adsorption of target molecules on the electrodes, modified with different polymeric materials, influenced dissimilarly their ESI behaviors. Target molecules adsorption decreased bulk resistance of the MIP-based electrodes, whereas sorption of cross-reactant molecule increased this parameter of the electrode. This effect for bulky MIP-based electrode was more than that for the nano-MIP electrode. Swelling of the MIP materials, after target molecule recognition, was proposed as a main proof for this observation. However, bulk resistance of the NIP-based electrodes increased with adsorption of both target and foreign molecule. Swelling experiment indicated that in the presence of an organic solvent the bulky MIP particles expanded more than the nano-sized MIP. This led to erased memory effect in the bulky MIP. Scatchard plot showed that the recognition sites of the nano-sized MIP particles had more affinity to target molecule, compared to those of the bulky MIP particles. The prepared MIP based electrodes were used to plot the calibration curves based on the variation of bulk resistance of the electrodes versus PMZ concentration. Although, the MIP nanoparticles showed higher affinity for the target molecule the bulky MIP-based electrode was capable to determine target molecule at lower concentrations. © 2012 Elsevier B.V. All rights reserved.

In this work a paraoxon voltammetric sensor was introduced. Different methods for integration of molecularly imprinted polymer (MIP) and electrochemical transducer were investigated. Three techniques including MIP particles embedding in the carbon paste (CP) (MIP-CP), coupling of MIP with the glassy carbon electrode (GC) surface by using poly epychloro hydrine (PECH) (MIP/PECH-GC) and MIP/graphite mixture thin layer attachment onto the glassy carbon electrode (MIP/Graphite-PECH-GC) were tested. The prepared electrodes were applied for paraoxon measurement by using a three-step procedure including analyte extraction in the electrode, electrode washing and electrochemical measurement of paraoxon. The washing of electrodes, after paraoxon extraction, led to high selectivity of electrode for paraoxon. It was found that MIP-CP electrode had higher response to paraoxon in comparison to other tested electrodes. Besides, the washing process decreased response magnitude of MIP/PECH-GC and MIP/Graphite-PECH-GC but, the response of MIP-CP was not affected considerably by the washing. Parathion was chosen to evaluate the selectivity of MIP based sensors. It was proved that the MIP-CP had better selectivity, wider linear range and lower detection limit in comparison to other tested electrodes. The developed MIP-CP electrode was used as a high selective sensor for paraoxon determination in water and vegetable samples. © 2010 Elsevier B.V. All rights reserved.

An electronic nose (EN) based on an array of chemiresistors, combined with a preconcentrator unit, for the detection of some volatile organic vapors was developed. In order to choose the proper polymers, seven potential polymers were chosen from numerous available polymers according to the principle of the linear solvation energy relationship (LSER). Different possible sensors arrays (128 arrays) composed of these seven polymers were designed by full factorial design (FFD). Principal component analysis (PCA) showed that four of seven polymers had enough ability to recognize different gas classes. By using Hierarchical cluster analysis (HCA), the tested polymers were categorized into four main groups with respect to their recognition ability. Combination of the FFD with PCA and HCA, brought to the identification of 8 proper arrays containing four polymers in each array. Precisely evaluation of predicted arrays with respect to their calculated resolution factors showed that the electronic nose containing the polymers of 75% pheny125% methylpolysiloxane (OV25), hexafluoro-2-propanolsubstituted polysiloxane (SXFA), poly bis(cyanopropyl)-siloxane (SXCN) and poly(ethylene maleate) (PEM) was the most proper design for recognition of analytes of interest. The fabricated EN was used successively for target gas recognition at three different concentrations. © 2009 Elsevier B.V. All rights reserved.

The aim of the present study is to investigate the problem of modulation instability of an intense laser beam in the hot magnetized electron-positron plasma. Propagation of the intense circularly polarized laser beam along the external magnetic field is studied using a relativistic fluid model. A nonlinear equation describing the interaction of the laser pulse with the magnetized hot pair plasma is derived based on the quasi-neutral approximation, which is valid for the hot plasma. Also, the nonlinear dispersion equation for the hot plasma is obtained. The growth rate of the instability is calculated and its dependence on temperature and external magnetic field are considered. © 2012 American Institute of Physics.

Alizadeh T.,University of Mohaghegh
Separation and Purification Technology | Year: 2013

A new chromatographic procedure was developed for the separation of atenolol (ATN) enantiomers based upon chiral ligand-exchange principal. The separation was carried out on a C8 column. l-alanine and Cu 2+ were applied as chiral selector and central bivalent complexing ion, respectively. It was found that the kind of copper salt had vital effect on the enantioseparation. The separation on the C8 stationary phase was more efficient than that on the C18 column. The pH of mobile phase, organic modifier content of mobile phase, mole ratio of chiral ligand to bivalent ion and Cu(l-alanine)2 concentration in the mobile phase were found to be important in enantiomers resolution efficiency. Water/methanol (70:30) mixture containing l-alanine-Cu2+ (2:1) was found to be the best mobile phase condition for ATN enantioseparation. The concentration of Cu(l-alanine)2 complex in the mobile phase influenced either enantiomers resolution efficiency or the detection sensitivity. All effective parameters were optimized in order to satisfy both detection sensitivity of the method and its separation efficiency. The optimized HPLC method was utilized in some synthetic and human blood plasma samples. © 2013 Elsevier B.V. All rights reserved.

Razavi S.M.,University of Mohaghegh
International Journal of Biological Chemistry | Year: 2011

In the last decades, application of synthetic toxins for control of weeds, pests and plant disease caused serious environmental problems. Allelopathy is regarded as a natural strategy in plants protecting them against environmental enemies and competing plants. This process involve plant secondary metabolites that suppress the growth and development of surrounding biological systems and named as allelochemicals. Thus, allelopathy interactions between plants and other organisms may become an alternative to synthetic herbicides and other pesticides. Coumarins are known as a large group of plant secondary metabolites mainly originated from shikimic acid pathway. This compounds are widely distributed in the Apiaceae, Rutaceae, Asteraceae and Fabaceae families of plants. Up to now, there has been many reports on phytotoxic, fungitoxic, insecticide, antibacterial and nematocidal activity of different coumarins. This study demonstrated that some coumarins like imperatorin and psoralen exhibited considerable allochemical potential. Therefore, this compounds could be utilized to generate a new generation of bioherbicides and other pesticide chemicals that are more ecologically friendly. © 2011 Academic Journals Inc.

Sepehri Javan N.,University of Mohaghegh
Physics of Plasmas | Year: 2013

The present study is aimed to investigate the problem of modulation instability of an intense laser beam in the hot magnetized plasma. The propagation of intense circularly polarized laser beam along the external magnetic field is considered using a relativistic fluid model. The nonlinear equation describing the interaction of laser pulse with magnetized hot plasma is derived in the quasi-neutral approximation, which is valid for hot plasma. Nonlinear dispersion equation for hot plasma is obtained. For left- and right-hand polarizations, the growth rate of instability is achieved and the effect of temperature, external magnetic field, and kind of polarization on the growth rate is considered. It is observed that for the right-hand polarization, increase of magnetic field leads to the increasing of growth rate. Also for the left-hand polarization, increase of magnetic field inversely causes decrease of the growth rate. © 2013 American Institute of Physics.

Yari M.,University of Mohaghegh
Renewable Energy | Year: 2010

Based on available surveys, it has been shown that Iran has substantial geothermal potential in the north and north-western provinces, where in some places the temperature reaches 240 °C. In order to better exploit these renewable resources, it is necessary to study this area. Thus, the aim of this paper is a comparative study of the different geothermal power plant concepts, based on the exergy analysis for high-temperature geothermal resources. The considered cycles for this study are a binary geothermal power plant using a simple organic Rankine cycle (ORC), a binary geothermal power plant using an ORC with an internal heat exchanger (IHE), a binary cycle with a regenerative ORC, a binary cycle with a regenerative ORC with an IHE, a single-flash geothermal power plant, a double-flash geothermal power plant and a combined flash-binary power plant. With respect to each cycle, a thermodynamic model had to be developed. Model validation was undertaken using available data from the literature. Based on the exergy analysis, a comparative study was done to clarify the best cycle configuration. The performance of each cycle has been discussed in terms of the second-law efficiency, exergy destruction rate, and first-law efficiency. Comparisons between the different geothermal power plant concepts as well as many approaches to define efficiencies have been presented. The maximum first-law efficiency was found to be related to the ORC with an IHE with R123 as the working fluid and was calculated to be 7.65%. In contrast, the first-law efficiency based on the energy input into the ORC revealed that the binary cycle with the regenerative ORC with an IHE and R123 as the working fluid has the highest efficiency (15.35%). Also, the maximum first-law efficiency was shown to be given by the flash-binary with R123 as the working fluid and was calculated to be 11.81%. © 2009 Elsevier Ltd. All rights reserved.

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