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61.
62.
Samaneh Salari Abdulrahman Bahrami Farhad Ghamari Farshid Ghorbani Shahna 《Chemical Papers》2018,72(8):1945-1952
The present study developed a liquid-phase microextraction based on hollow fiber coupled with graphite furnace atomic absorption spectrometry for the effective extraction and quantitation of lead from urine and blood samples. A multivariate design was used for the optimization of the experimental conditions to ensure high extraction efficiency. Six factors (solvent type, chelating agent, time extraction, temperature, donor phase pH, and acceptor phase pH) were obtained by screening eleven factors of the Plackett–Burman design; these were optimized using the central composite design of response surface methodology. The optimum conditions of donor phase pH, acceptor phase pH, temperature, and extraction time were 5, 9.5, 40 °C, and 120 min, respectively. In addition, oleic acid containing dicyclohexyl-18-krone-6 was used for the membrane phase. Under optimal conditions, the enrichment factor, limit of detection, and limit of quantification were obtained in the ranges of 21.3–18.7, 0.001–0.002 ng mL?1, and 0.008–0.01 ng mL?1, respectively, in urine and blood samples. The linearity of the calibration curve was established for the concentration of Pb in the range of 1–50 ng mL?1 (r2?=?0.9983). Finally, the performance of the developed method was evaluated for the determination of lead in urine and blood samples, and satisfactory results were obtained (RSDs <?10% with recovery >?95). 相似文献
63.
Parisa Pazhooh Roushan Khoshnavazi Leila Bahrami Elham Naseri 《Journal of the Iranian Chemical Society》2018,15(8):1775-1783
New nanocomposites containing sandwich-type polyoxometalate of [(PW9O34)2(HOSnIVOH)3]12? (P2W18Sn3) loaded onto Ln-doped TiO2 (Nd, Sm, Dy, Tb) nanoparticles were synthesized and their catalytic activities were assessed. The Ln–TiO2 nanoparticles and Ln–TiO2/P2W18Sn3 nanocomposites were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction, field emission scanning electron microscope, energy dispersive analysis of X-rays spectra and diffuse reflectance spectra. The photocatalytic efficiency of the Ln–TiO2 and Ln–TiO2/P2W18Sn3 were examined in the photodegradation of methyl orange and methylene blue solutions. It was revealed through different characterization techniques that the P2W18Sn3 was successfully loaded on the lanthanide-doped anatase phase TiO2 nanoparticles and the particles diameter were relatively 20–30 nanometers. It was revealed that doping by the lanthanide ions followed by loading of polyoxometalates improves the photocatalytic performance of TiO2 effectively. The effects of operational parameters and the kinetics of photocatalytic degradation under UV light were discussed. The prepared nanocomposites were stable and could be easily separated from the reaction system. 相似文献
64.
Samira Dadkhah-Tehrani Mehdi Shabani-Nooshabadi Mohsen Moradian 《Journal of the Iranian Chemical Society》2018,15(1):171-179
The electrochemical synthesis of some new 2-[(4-methyl-2-pyridyl)amino)-1,4-benzenediol derivatives was performed via the electrochemical oxidation of hydroquinones in the presence of 2-amino-4-methylpyridine in an aqueous solution. The results demonstrate that electrogenerated p-benzoquinone participated in the Michael-type addition reaction via an electrochemical–chemical (EC) reaction mechanism pathway and converted to the corresponding 2-[(4-methyl-2-pyridyl)amino)-1,4-benzenediol derivatives. These new compounds have been synthesized in high yields and purity without using any toxic reagents or catalyst at the surface of carbon electrode. 相似文献
65.
In this article, the palladium (II) mixed-ligand complex synthesized with reduced graphene oxides containing tetraethoxysilane and menthone oxime was used as an efficient solid catalyst for the Heck coupling reaction. To maintain stability and catalytic activity in the C–C bond reaction, graphene was considered due to the available surface as the solid support. Then, the structure of new heterogeneous catalyst was investigated by FT-IR, UV–Vis DRS, FE-SEM, EDX, AFM, XRD, ICP-OES, Raman, and TGA. The newly synthesized nanocatalyst have beneficial properties, including product’s easy separation, the shorter time to react, purity products (yield 79–99%), and easier work-up procedure. Furthermore, the catalyst was reused six times without significant degradation in catalytic activity and performance. 相似文献
66.
Introducing Fe2+ into Nickel–Iron Layered Double Hydroxide: Local Structure Modulated Water Oxidation Activity 下载免费PDF全文
Zhao Cai Daojin Zhou Maoyu Wang Seong‐Min Bak Yueshen Wu Zishan Wu Yang Tian Xuya Xiong Dr. Yaping Li Dr. Wen Liu Prof. Samira Siahrostami Dr. Yun Kuang Prof. Xiao‐Qing Yang Dr. Haohong Duan Prof. Zhenxing Feng Prof. Hailiang Wang Prof. Xiaoming Sun 《Angewandte Chemie (International ed. in English)》2018,57(30):9392-9396
Exploring materials with regulated local structures and understanding how the atomic motifs govern the reactivity and durability of catalysts are a critical challenge for designing advanced catalysts. Herein we report the tuning of the local atomic structure of nickel–iron layered double hydroxides (NiFe‐LDHs) by partially substituting Ni2+ with Fe2+ to introduce Fe‐O‐Fe moieties. These Fe2+‐containing NiFe‐LDHs exhibit enhanced oxygen evolution reaction (OER) activity with an ultralow overpotential of 195 mV at the current density of 10 mA cm?2, which is among the best OER catalytic performance to date. In‐situ X‐ray absorption, Raman, and electrochemical analysis jointly reveal that the Fe‐O‐Fe motifs could stabilize high‐valent metal sites at low overpotentials, thereby enhancing the OER activity. These results reveal the importance of tuning the local atomic structure for designing high efficiency electrocatalysts. 相似文献
67.
We report a simple and highly stereocontrolled strategy toward the total synthesis of isoprostanes based on a bicyclic alpha,beta-epoxy ketone intermediate 6. Bicyclo[3.3.0]octene scaffold permitted stereodirection of reagents allowing stereoselective epoxidation, diastereoselective ketone reduction, and regioselective epoxide opening otherwise not accessible with a simple cyclopentene framework. 相似文献
68.
The kinetics of the permanganic oxidation process of glycine, L-alanine and L-leucine in strong acid media were investigated using a spectrophotometric technique. Conclusive evidence has proven that the autocatalytic activity of Mn(II) in these reactions in strong acidic media is analogous to that of weak acid media, but in the former, Mn(II) ions should acquire a critical concentration for them to show autocatalytic characteristics. This critical concentration depends on the nature of the amino acid used. Considering the delayed autocatalytic behavior of Mn(II) ions, we herein present the rate equations and mechanisms satisfying observations for both catalytic and noncatalytic routes. The correspondence of the pseudo-order rate constants of the catalytic and noncatalytic pathways to Eyring law verify both the critical concentration as well as the delayed autocatalytic behavior concepts. In general, the onset of delayed behavior can be attributed to the concentration ratio of Mn(II) to amino acid which can be of a certain value for any particular amino acid. 相似文献
69.
A new, convenient method for the syntheses of 2-substituted benzimidazole and benzothizole is described. Short reaction times, large-scale synthesis, easy and quick isolation of the products, excellent chemoselectivity, and excellent yields are the main advantages of this procedure. 相似文献
70.
Highly hydrolytic and thermally stable sandwich-type polyoxometallates of [(A-β-SiW9O34)2(MOH2)3CO3]13− (M = Y3+ and Yb3+) have been synthesized at room temperature by stoichiometric reactions of the trilacunary ligand with M3+ in 0.1 M carbonate solution. The new complexes were isolated as sodium and mixed sodium/potassium salts and were characterized by elemental analysis, IR, 13C and 29Si NMR, UV–Vis spectroscopy, TGA, DSC and single crystal structure analysis. The crystal structure of the complexes consist of two lacunary Keggin moieties which are linked by a (H2OMO)3C belt into an assembly of virtual C2 symmetry. Each M3+ ion adopts a mono-capped trigonal-prismatic coordination. The C2 axis of the complexes and the local 3-fold axis of the MO6 group lies in the (H2OMO)3C belt plane. The trigonal prismatic geometry is achieved by the two terminal oxygen atoms of an edge shared pair of WO6 octahedra from each moiety and two oxygen from the belt, and the cap by one external water ligand. The hydrolytic and thermal stabilities of the complexes and the reasons that prove the retention of the isomeric form of the trilacunary ligand upon complexation are discussed. 相似文献