JOURNAL OF SCIENCES (ISLAMIC AZAD UNIVERSITY)
Year:2010 | Volume:20 | Issue:76 (CHEMISTRY ISSUE)|Papers Count:12

Introduction: since the discovery of carbon nanotubes they have attracted an enormous amount of interest because of their unique physical properties and many potential applications. For many carbon nanotubes applications, purified nanotube material is often desired.Aim: the CNTs as produced by the various synthesis techniques contain impurities such as graphite, amorphous carbon, fullerenes and metal catalyst particles. These impurities have to be separated from the carbon nanotubes before they can be used for more applications. Purification techniques have been devised in order to improve the quality and yield of carbon nanotubes. The principal aim in this research was the effect of air oxidation and acid treatment on purification of multi- walled carbon nanotubes.Materials and methods: Carbon nanotubes (CNTs) were grown on Fe/Ni bimetallic catalysts based on MgO by thermal CVD deposition technique. The purification of carbon nanotubes is carried out under oxidation and acid treatment with hydrochloric acid solution. Various analytical techniques such as: scanning electron microscopy (SEM), thermal gravimetric analysis (TGA) and Raman spectroscopy techniques were employed to investigate the morphology, graphitization and quality of the carbon nanotubes.Results: the scanning electron microscopy (SEM) images of the pristine CNTs (without any purification treatment) show that pristine CNTs contain many impurities and it is hard to trace nanotubes, the effect of air oxidation and acid treatment in dissolution of catalyst is quite visible. The X-ray diffraction analysis showed that the peaks of MgO and Fe/Ni catalyst were disappeared after purification. Also, the peak at 2q=26.5owas attributed to the graphite structure indicating the purification at the samples was complete. Raman spectroscopy technique was employed to investigate the quality of the carbon nanotubes. Intensity of the G-band to Intensity of the D-band (IG/ID), are used to estimate the quality of CNTs. The IG/ID ratio for the purified MWCNTs increased to 1.7 and indicates that some of the carbon impurities or defective structures of MWCNTs have been removed from the pristine sample. The TGA result show that CNTs yield of raw, oxidized and purified CNTs are about 28.6, 22.2, 92.6 % respectively.Conclusion: it is concluded that weight ratio of CNTs after air oxidation and hydrocholoric acid treatment were reached to 92.6 %.

Introduction: The global energy demand increases every year. So preparation of bio-fuel cells has been received much attention in recent years. Biofuel cell is an energy conversion device which is used biological materials as catalysts. A biofuel cell might be applied to implantable medical devices and biosensors.Aim: The goal of this investigation is to explore new applications of carbon nanotubes as new materials in facilitating the direct electron transfer between biomolecules and electrode.Materials and Methods: Glucose oxidase-based anode (Aspergillus niger) electrode of biofuel cell has been designed by using of multi-walled carbon nanotubes, due to the remarkable electronic and mechanical properties of multi-walled carbon nanotubes. In this study, the carbon electrode has been modified with the needlelike assembled multi-walled carbon nanotubes attached covalently to the carbon electrode and glucose oxidase attached to the multi-walled carbon nanotubes.Results: The linear rang of the bioanode to glucose concentration is from 10 mM up to 40 mM. By using this method, redox pick was achieved at 11 mA in 100 mM glucose containing solution.Conclusion: According to the results, presented method is more efficient than other methods with ensemble of multi-walled carbon nanotubes dispersed randomly on electrode surface to enhance direct electron transfer. Cyclic voltammetric results showed a pair of well-defined redox peaks, which corresponded to the direct electron transfer of glucose oxidase immobilized on needlelike assembled multi-walled carbon nanotubes, suggesting the method presented here may be used in glucose oxidase -based biosensors or as a bioanode in the biofuel cells.

Introduction: Protection and preservation of the environment especially aquatic environment from various contaminations is an intricate that human more than ever have get involved. Rivers are one of the main sources of water supply for agricultural, industrial and drinking purposes. Therefore, it is important to conserve this resource specially with occurring recent droughts, urban and rural developments. Among these contaminant effecting of encompassed material such as heavy metals. Because of poisionig and accumulating property on humans and aquatic heavy metals have damaged on environment. Source contamination hurmful anions such as NO3-, CrO42- , SO42- undesirable effect water and many problem water treatment installatio thus must decrease for wastewater and water. Zeolites abundant substance and Capacsity high absorption cation and anion. Application value substance wastewater treatmentan and problem removal.Aim: This study analysis Chemistry laboratory nature zeolite sulfte anion Determination. In this work nature zeolite with cation surfactant modified such as HDTMA and absorption water anion contamination determination.Results: In research showed surfactant absorption whit zeolite and product surfactant modified zeolite gerate variation zeolit characteristic.Conclusion: This study The proposed chemically modified carbon paste electrode based on surfactant modified zeolite (SMZ-CPE) might be a useful analytical tool for determination of sulfate in real samples. The obtained electrode was used as a new potentiometric sensor for sulfate determination. The electrode show Nernstian behavior toward sulfate electrode 10% (13X+50mM HDTMA).

Introduction: Nano-emulsions are a class of emulsions that can be transparent or translucent (size range 50-200 nm) or “milky” (up to 500 nm). The nano-emulsions applied in various industrial fields, for example, reaction media for polymerization, personal care and cosmetics, health care, and agrochemicals.Aim: In this research the formation of nanoemulsion is studied by phase inversion temperature method in system of n-hexadecane/Brij 30/water and the effect changes of NaCl concentration in aqueous phase on the system phase inversion temperature (PIT) and also the stability of nanoemulsions via time were studied.Materials and Methods: In this research the system of n-hexadecane/Brij 30/water with was selected as base and then concentration of NaCl has been varied and PIT in systems of relate measured by conductometric methods and the nanoemulsions were prepared in PIT of related. The transmission of nanoemulsions measured in 600 nm wavelength for comparison of size and stability theirs via time, then the size of droplets measured in selected of samples by TEM instruments.Results: The results shows decrease of PIT from 41oc to 26oc with rise of concentration of NaCl from 0.01 to1.00 mol per liter. The differences of transmission of nanoemulsion in all of NaCl concentrations in aqueous phase except 0.50 and 1.00 mole per liter has been constant until 336 hours approximately. The mean droplet diameter of nanoemulsions with NaCl concentrations 0.05, 0.10, 0.25mol per liter in aqueous phase were 10,7,10 nm with standard deviations 8.50, 3.27 and 5.10 respectively.Conclusion: The results show: The first with rise of NaCl concentration in the emulsion aqueous phase will decrease PIT; The second transmission of nanoemulsions have a little change in concentrations 0.01, 0.05, 0.10 and 0.25 M of NaCl aqueous phase in 25oc, that shows nanoemulsions are stable in this temperature but in concentrations 0.50 and 1.00 M transmission decrease rapidly, that shows these nanoemulsions are instable in this temperature. Finally average size of droplets selective nanoemulsions measured by TEM Instrument, with respect to other nanoenulsions prepared by other researchers were very lower.

Introduction: Citalopram Hydro bromide is one of the antidepressant medications that belongs to the family which are the Selective inhibitors of serotonin reuptake. Due to having minimal side effects this medication is now under a huge consideration from psychiatrics and also patients. Citalopram Hyrobromide is among the most important salt that are produced from Citalopram and its high degree of purity will cause more effectiveness and less side effects.Aim: to reach to a final product -citalopram hydrobromide-with 99% purity by using activated natural Zeolite named clinoptilolite as an adsorptive solid phase for citalopram and elimination of its impurities.Method: In this method produced Citalopram is solved in an Acid and then it is purified by adding Clinoptilolite that is an activated Zeolite then citalopram will be extracted, and finally its bromide salt has been prepared in a solvent. The product purity is being measured with high performance liquid chromatography (HPLC) device.Results and discussion:  the results of experiments have been inspected before adding Zeolite and after that. The results showed that adding Zeolite cause the degree purity to by increased from 93.75 to 99.45 and total amount of impurities decreased from 0.25 % to 0.064%. Other properties of product are in complete agreement with the standards of pharmacopeia of America.Conclusion: Analysis shows that in this method the degree of purity is increased and the amount of impurities is decreased. Besides the most important advantage of this method is that less amount of solvent is consumed.

Introduction: Isatin is a compound which has many biological effects such as antibacterial, antifungal, anti HIV and anticancer activities. The cyclopropane ring is a main structural part in many synthetic and natural compounds that exhibits many biological activities and chemists have tried to synthesis it by novel methods.Aim: In this study, a rapid and simple procedure was reported for the synthesis of new spiro isatin-cyclopropanes which prepared from 2-pyrazolines. These compounds have both isatin and cyclopropane moieties and may be of value in medicinal and pharmaceutical chemistry.Materials and Methods: The 2-pyrazolines were dissolved in toluene and then solid lead tetraacetate (LTA) was added to them at 40-50 oC and the reaction was continued for 10-20 minutes and new spiro isatin-cyclopropane compounds were prepared. The products were purified and their structures were deduced from their spectroscopic analysis.Results: The Kishner cyclopropanation needs higher temperatures. In this study, reaction was catalyzed with LTA and carried out in lower temperatures. One of the two resulted diastereomers was produced in higher yields than the other. For example, the diastereomeric ratio, 2a:3a=2.7:1, was determined by signal integrations in 1H NMR spectra of the mixture of compounds 2a and 3a.Conclusion: Some spiro isatin-cyclopropanes were synthesized in a rapid and simple procedure.

Introduction: The imprinting technique involves the formation of a complex between a template molecule and the functional monomers in an appropriate solvent. The procedure for synthesizing an MIP is based on the chemical polymerization of a functional monomer and a cross-linking agent in the presence of a molecule used as a template. Removal of the template yields a functional polymeric matrix with recognition sites complementary in functionality and shape to the print molecule structure. These MIPs have been employed in fields where a certain degree of selectivity is required.Aim: Simple and inexpensive extraction and detection of Metoclopramide (MCP) from biologic samples.Materials and Methods: After polymerization of SPE procedure, successful imprinting was confirmed by comparison of the recoveries between NIP and MIP particles. Molecular recognition properties, binding capability and selectivity of the MIPs were evaluated. UV spectroscopic determination of MCP was done at 309 nm and accuracy and precision was checked by the liquid chromatographic technique.Results: Polymer imprinted for MCP has been synthesized via a non-covalent molecular imprinting approach. The MIP has then been applied in a SPE procedure, which enables the selective extraction of MCP from biological samples, even when MCP is present at low concentrations. It was shown that recoveries of nearly 99% of a MCP standard solution and up to approximately 91% from spiked human urine and serum samples could be obtained after SPE. The binding capacity of the MIP for MCP was determined to be 113 mg g-1 (319 mmol/ g). The MISPE can be successfully applied to clean-up and preconcentration of MCP.Conclusion: Water-compatible molecularly imprinted polymers (MIPs) designed to enable the selective extraction of metoclopramide (MCP) from complex matrices such as biological fluids and human urine have been synthesized.

Introduction: Aromatic polyimides are heat resistant polymers that generally show excellent mechanical strength and stability. However, one of the drawbacks to the employment of these high performance polymers is the difficulty in processing due to their high melting temperatures or high glass transition temperatures. Copolycondensation is one of the possible ways for modification of polymer properties. Thus, for the processing of polyimides many copolyimides, such as poly (amide-imide) s, poly(sulfone-imide)s, poly (ether-imide)s, poly(ester-imide)s and other copolymers have been prepared.Aim: In this article, we describe synthesis and characterization a series of novel PAIs (5a-f) containing trimethylene and hydantoin segments between imide rings in the main chain by the direct polycondensation reaction of N-(4- carboxyphenyl)-trimellitimide (3) with six hydantoin derivatives (4a-f) in a medium consisting of N-methyl-2-pyrrolidone, triphenyl phosphite, calcium chloride and pyridine.Materials and Methods: All chemicals were purchased from Fluka and Merck Chemical Company. The 1H-NMR spectrum (300 MHz) was recorded on a Bruker Avance 300 spectrometer (Germany). Fourier transform infrared (FT-IR) spectra were recorded on a Galaxy series FTIR 5000 spectrophotometer (England).Results: Six new poly (amide-imide) s (5a-f) were prepared by direct polycondensation reaction of N-(4-carboxyphenyl)-trimellitimide (3) with six different of 5,5-disubstituted hydantoin derivatives (4a-f) using triphenyl phosphate (TPP) and pyridine as condensing agents in N-methyl-2-pyrolidone (NMP) solution containing dissolved calcium chloride. The polycondensation reaction produced a series of novel poly (amide-imide) s (5a-f) in high yields with inherent viscosities between 0.26-0.62 dL/g. The resulted polymers were characterized by elemental analysis, viscosity measurements, thermal gravimetric analysis (TGA and DTG), solubility test and FT-IR spectroscopy.Conclusion: This work involved the synthesis and characterization of several new PAIs (5a-f) by direct polycondensation reaction of N-(4-carboxyphenyl) trimellitimide (3) with different 5,5-disubstituted hydantoin derivatives (4a-f) using TPP and pyridine as condensing agents in NMP solution containing dissolved calcium chloride. These new PAIs are soluble in various organic solvents and have good thermal stability. These properties could make these PAIs attractive for practical applications, such as processable high-performance engineering plastics.

Introduction: Ardebile Propolis (bee glue) is a sticky dark-colored material that collected from living plant buds or exudates by bees, and mix it with wax and sugars. More than 180 compounds have been identified in world Propolis and many are biologically active. Flavonoids appear to be the principal components responsible for the biological activities of Propolis samples. Flavonoids are abundant, including apigenin, galangin, kaempferol, luteolin, Pinocembrin, quercitin, pinostrobin and etc.Aim: Investigation and identification of flavonoid compounds of %96 ethanolic extract of pooled Propolis samples collected from three different regions of Ardebile.Material and Methods: Ethanolic extract of pooled Propolis from three different regions of Ardebile to identified of flavonoids was analyzed by High Performance Liquid Chromatography (HPLC) method.Results:Ten individual flavonoid compounds were identified, and most of them indicate the chemical pattern of popular Propolis. They contained pinocembrin, pinocembrin chalcone, pinobanksin, pinostrobin, pinostrobin chalcone, galangin, apigenin, chrysin, tectochrysin and chromone. About three isolated components were not identified.Conclusion: The flavonoid compounds identified in Ardebile Propolis included flavones, flavanones, flavanolols, flavonols and chalcones. It is an interesting finding, since such compounds were found in tropical Propolis. These flavonoids have the biological activity. Thus, consumption of foods containing flavonoids has been associated with a variety of health benefits. This could be interest because it has been shown that bees have the ability to find in their environment Propolis.

Introduction: NMR analysis and hybrid-DFT based method (B3LYP/Def2-TZVPP) were used to investigate the correlation between 3-dimentional aromaticity and the dissociation energy of diborane, dialane, digalane and diindane to their corresponding monomers.Aim: The correlation between the aromatic character and the dissociation energy of diborane, dialane, digalane and diindane to their corresponding monomers have been investigated.Results: The results obtained showed that the dissociation energy decreases from diborane to diindane. The aromatic character of the above compounds is demonstrated by their Nucleus-Independent Chemical Shifts [NICS(0), NICS(0.2), NICS(0.4) and NICS(0.6)].Conclusion: Interestingly, there is a significant relationship between the decrease of the in-plane s22 (i.e. syy, the plane containing H atoms bridged) chemical shift components of the NICS values and the dissociation energies of dimmers to their corresponding monomers.

Introduction: quantitative structure-activity relationship (QSAR) study is one of best chemometrics methods for prediction of chemical and biological properties of various compounds.Aim: A quantitative structure-activity relationship (QSAR) study is suggested for the prediction of capacity factors (log k’) of 25 substances as solutes to two different stationary phases (polyethylene–silica and polyethylene–alumina) were analyzed to their quantum chemical descriptors and related to their retention behavior as expressed by the logarithms of their capacity factors (log k’).Material and Method: Ab initio theory was used to calculate some quantum chemical descriptors including electrostatic potentials and local charges at each atom, HOMO and LUMO energies, etc. Modeling of the log k' as a function of molecular structures was established by means of the partial least squares (PLS) and least squares support vector machines (LS-SVM). These models were applied for the prediction of the capacity factors, which were not in the modeling procedure.Results: The resulted models showed high prediction ability with root mean square error of prediction of 6.5621 and 0.4960 for PLS and LS-SVM, respectively.Conclusion: this research showed that LS-SVM method has a very good ability for prediction of capacity factors (log k’) for benzene derivatives.