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941.
Pouneh S. Pourhosseini Reza Amani Ali A. Saboury Farhood Najafi Mohammad Imani 《Journal of the Iranian Chemical Society》2014,11(2):467-470
A series of poly(l-lactic acid)/poly(ethylene glycol) triblock copolymers with a PLA–PEG–PLA architecture were synthesized by a ring-opening polymerization (ROP) process. The copolymers were characterized by 1H NMR and GPC. The total number average molecular weights were in the range of 4,700–50,000, whereas the degrees of polymerization of the PLA and PEG blocks varied from 15 to 359 and from 68 to 136, respectively. The self-association of these copolymers in aqueous environment was studied by emission fluorescence spectroscopy of anilinonaphthalene probe and the critical association concentration (CAC) of the copolymers was measured. It was found that the micellization process of these copolymers was mainly determined by the length of the hydrophobic LA block, while the length of the hydrophilic PEG block had little effect. Furthermore, the low CAC values of the copolymers suggest that the copolymers form stable supramolecular structures in aqueous solutions. 相似文献
942.
Mohammad Yousefi Elham Noori Davood Ghanbari Masoud Salavati-Niasari Tahereh Gholami 《Journal of Cluster Science》2014,25(2):397-408
In this work, poly vinyl alcohol–ZnO nanocomposites were synthesized via two different in situ and ex-situ methods. In ex-situ, at first zinc oxide nanostructures were synthesized by one-step precipitation reaction between zinc acetate and sodium hydroxide. The effect of different surfactants such as poly vinyl pyrrolidone, poly vinyl alcohol and poly ethylene glycol on the morphology of ZnO nanostructures was investigated. Nanostructures were characterized by X-ray diffraction, scanning electron microscopy. The influence of ZnO nanostructures on the flame retardancy of the poly vinyl alcohol matrix was studied using underwriter laboratories UL-94 analysis. 相似文献
943.
Ali Akbarzadeh Seyed Omid Ranaei Siadat Mostafa Motallebi Mohammad Reza Zamani Mohammad Barshan Tashnizi Sakineh Moshtaghi 《Applied biochemistry and biotechnology》2014,172(4):2253-2265
Bioconversion of cellulosic material into glucose needs cellulase enzymes. One of the most important organisms that produces cellulases is Trichoderma reesei, whose cellulose enzymes are probably the most widely used in the industry. However, these enzymes are not stable enough at high pH and temperatures. The optimized synthetic endoglucanase II gene with Pichia pastoris codon preferences was secretary expressed in P. pastoris. Recombinant enzyme characterization showed maximum activity at pH 4.8 and temperature 75 °C, and it demonstrated increasing thermal stability in high temperature. The enzyme maintained its activity in a wide pH range from 3.5 to 6.5. The optimization of fermentation medium was carried out in shaking flasks. Recombinant protein expression at optimum conditions (pH 7, temperature 25 °C, and 1 % methanol induction) for 72 h demonstrated 2,358.8 U/ml endoglucanase activity units. To our knowledge, this is the highest acidic thermophilic endoglucanase activity that is reported in crude intracellular medium in P. pastoris. We conclude that P. pastoris is an appropriate host for high-level expression of optimized endoglucanase gene with improved thermal stability. 相似文献
944.
Y. C. Goswami Vijay Kumar P. Rajaram V. Ganesan Mohammad Azad Malik Paul O’Brien 《Journal of Sol-Gel Science and Technology》2014,69(3):617-624
Fluorine doped SnO2 nanostructures were grown using ultrasonic assisted sol–gel method. The gel was obtained by dissolving stannous chloride in methanol with ammonium fluoride as dopant followed by irradiation with ultrasonic vibrations. Obtained samples were characterized by structural, morphological and optical studies. All the peaks in the X-ray diffractograms are identified and indexed as tetragonal cassiterite structure. Negative slope of Williamson–Hall plots indicates compressive strain. Particle size of SnO2 nanostructures is decreases with increases in concentration of fluorine doping. Atomic force microscopy, scanning electron microscopy and transmission electron microscopy studies confirm the formation of ring like porous structures and then hollow tube like growth with increase in the fluorine concentration. Peaks in Raman spectra also indicate strong confinement in SnO2 particles. Distinct peaks in the PL spectra make the structure suitable for photovoltaic applications. 相似文献
945.
Mohammad Saraji Malihe Khalili Boroujeni 《Analytical and bioanalytical chemistry》2014,406(8):2027-2066
During the past 7 years and since the introduction of dispersive liquid–liquid microextraction (DLLME), the method has gained widespread acceptance as a simple, fast, and miniaturized sample preparation technique. Owing to its simplicity of operation, rapidity, low cost, high recovery, and low consumption of organic solvents and reagents, it has been applied for determination of a vast variety of organic and inorganic compounds in different matrices. This review summarizes the DLLME principles, historical developments, and various modes of the technique, recent trends, and selected applications. The main focus is on recent technological advances and important applications of DLLME. In this review, six important aspects in the development of DLLME are discussed: (1) the type of extraction solvent, (2) the type of disperser solvent, (3) combination of DLLME with other extraction methods, (4) automation of DLLME, (5) derivatization reactions in DLLME, and (6) the application of DLLME for metal analysis. Literature published from 2010 to April 2013 is covered. 相似文献
946.
A simple, efficient, and ecofriendly procedure has been developed using propane-l,2,3-triyl tris(hydrogen sulfate) as a catalyst for the synthesis of biscoumarin derivatives in water and solvent-free conditions. The significant features of the present protocol are simplicity, environmentally benign, high yields, no chromatographic separation, and recyclability of the catalyst. 相似文献
947.
Mohammad Behbahani Hamid Sadeghi Abandansari Mani Salarian Meysam Babapour Akbar Bagheri Mohammad Reza Nabid 《Mikrochimica acta》2014,181(1-2):129-137
We have designed and synthesized a thermosensitive tri-block copolymer for selective trace extraction of Pb(II) ions from biological and food samples. The polymer was characterized by Fourier transform IR and NMR spectroscopy, and by gel permeation chromatography. The critical aggregation concentration and lower critical solution temperature were determined via fluorescence and UV spectrophotometry, respectively. The effects of solution pH value, amount of copolymer, of the temperature on extraction and on phase separation, and of the matrix on the extraction of Pb(II) were optimized. Pb(II) ions were then quantified by FAAS. The use of this copolymer resulted in excellent figures of merit including a calibration plot extending from 0.5 to 160 μg L?1 (with an R2 of >0.99), a limit of detection (LOD) as low as 90 pg L?1, an extraction efficiency of >98 %, and relative standard deviations of <4 % for eight separate extraction experiments. Figure
In this paper, for the first time an intelligent system using a thermosensitive tri-block copolymer for selective trace removal of Pb(II) in biological and food samples was designed and its determination was carried out by flame atomic absorption spectrometry. 相似文献
948.
Nader Noroozi Pesyan Mohammad Jalilzadeh Nasim Yalabi Torkaman Ertan Şahin 《Journal of the Iranian Chemical Society》2014,11(1):35-45
Reaction of symmetrical and unsymmetrical (thio)barbituric acids with aldehydes in the presence of triethylamine afforded a new form of bis-(thio)barbiturate containing charge-separated inter- and eight-membered intramolecular H-bonds. The reaction products were obtained as bis-(thio)barbiturates containing eight-membered intramolecular H-bond in the presence of l-(+)-tartaric acid (TA). The intramolecular H-bond strength (kcal/mol) and corresponding pKa value for 4ab′ were estimated to be 37 kcal/mol and ?1.3, respectively. 相似文献
949.
Hadi Baharifar Ali Reza Fakhari Hakimeh Ziyadi Mohammad Ali Oghabian Amir Amani Reza Faridi-Majidi 《Journal of the Iranian Chemical Society》2014,11(1):279-284
In this work, electrophoresis was successfully used to separate three different polymer-coated magnetic iron oxide nanoparticles with similar sizes (nominally 50 nm) using high-pH borate buffer system. The coating polymers were dextran, polyethylene glycol, or carboxymethyl dextran. The results showed that the migration time of carboxymethyl dextran coated nanoparticles is the longest due to relatively more negative surface charges. Investigation of the effects of buffer concentration, pH, electric field strength and the capillary temperature, on electrophoretic properties of samples was also carried out. The results showed that pH, electric field strength and the capillary temperature had indirect relations with both of the migration time and the separation resolution of three different polymer-coated nanoparticles while the buffer concentration had a direct relation. 相似文献
950.
Thermal and pH Dual Responsive Copolymer and Silver Nanoparticle Composite for Catalytic Application
Luqman Ali Shah Wulian Chen Mohammad Siddiq Jianhua Hu Angang Dong Dong Yang 《中国化学》2015,33(4):467-472
N‐Isopropylacrylamide and vinyl imidazole copolymer, P(NIPAM‐co‐VI), was synthesized by free radical emulsion polymerization. Then, the copolymer and silver nanoparticle composite, P(NIPAM‐co‐VI)‐Ag, was prepared by in situ reduction of AgNO3 with NaBH4. Due to the coexistence of thermal‐responsive PNIPAM and pH‐responsive PVI, P(NIPAM‐co‐VI) and P(NIPAM‐co‐VI)‐Ag exhibited both thermal and pH responsibility, their size would change while altering the temperature or pH of the circumvent. Their thermal and pH dual responsive properties were studied by dynamic light scattering (DLS). P(NIPAM‐co‐VI)‐Ag could be stably dispersed in water at a pH range from 3.0 to 9.3, which is favorable to use P(NIPAM‐co‐VI)‐Ag as a catalyst in the reduction reaction of p‐nitrophenol. The reaction rate constant (kapp) increased with the decrease of pH or the increase of VI content in the copolymer. 相似文献