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A rapid, efficient, and new solvent terminated dispersive liquid–liquid microextraction technique coupled with HPLC was developed for selective extraction and analysis of s‐triazine herbicides from environmental water samples. Important parameters influencing the extraction process including type and volume of extraction and disperser solvent, extraction time, sample pH, ionic strength, and extraction temperature were successfully optimized. Under the optimal conditions, there are excellent linear relationships between the analytical results and concentration in the range of 10–400 mg/L for atrazine, propazine, prometryn, and terbutryn. LOD and LOQ ranged from 0.60 to 2.33 μg/L and 2.0 to 7.7 μg/L, respectively. Performance of the analytical technique was evaluated by carrying out the repeatability and reproducibility analyses that were ranged from 2.86 to 5.66% and 4.64 to 5.89% for 100 μg/L of each target analyte, respectively. The proposed method has been successfully applied to the analysis of real water samples and acceptable relative recoveries over the range of 65.93–101.46%, with RSDs ≤ 8.80%, were obtained. The overall results have been compared with the literature values. Thus, the method developed could efficiently be used for selective extraction of the target analytes from complex matrices, particularly environmental waters. 相似文献
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A metathesis reaction between unsolvated NaB(3)H(8) and NH(4)Cl provides a simple and high-yield synthesis of NH(4)B(3)H(8). Structure determination through X-ray single crystal diffraction analysis reveals weak N-H(δ+)---H(δ-)-B interaction in NH(4)B(3)H(8) and strong N-H(δ+)---H(δ-)-B interaction in NH(4)B(3)H(8)·18-crown-6·THF adduct. Pyrolysis of NH(4)B(3)H(8) leads to the formation of hydrogen gas with appreciable amounts of other volatile boranes below 160 °C. Hydrolysis experiments show that upon addition of catalysts, NH(4)B(3)H(8) releases up to 7.5 materials wt % hydrogen. 相似文献
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Beyene Gashaw Senbeta Teshome Mesfin Belayneh Zhang Qinfang 《Optical and Quantum Electronics》2020,52(3):1-9
Optical and Quantum Electronics - Numerical simulation of opto-electric characterization of GaAs/GaSb core–shell nanowire solar cells is presented, using a finite difference time-domain... 相似文献
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Gamachis Sakata Gurmesa Dr. Tamiru Teshome Dr. Natei Ermias Benti Dr. Girum Ayalneh Tiruye Prof. Dr. Ayan Datta Dr. Yedilfana Setarge Mekonnen Dr. Chernet Amente Geffe 《ChemistryOpen》2022,11(6):e202100289
Using first-principles calculations, biaxial tensile (ϵ=2 and 4 %) and compressive (ϵ=−2 and −4 %) straining of Na2MnSiO4 lattices resulted into radial distance cut offs of 1.65 and 2 Å, respectively, in the first and second nearest neighbors shell from the center. The Si−O and Mn−O bonds with prominent probability density peaks validated structural stability. Wide-band gap of 2.35 (ϵ=0 %) and 2.54 eV (ϵ=−4 %), and narrow bandgap of 2.24 eV (ϵ=+4 %) estimated with stronger coupling of p–d σ bond than that of the p–d π bond, mainly contributed from the oxygen p-state and manganese d-state. Na+-ion diffusivity was found to be enhanced by three orders of magnitude as the applied biaxial strain changed from compressive to tensile. According to the findings, the rational design of biaxial strain would improve the ionic and electronic conductivity of Na2MnSiO4 cathode materials for advanced rechargeable sodium-ion batteries. 相似文献
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The dinucleating ligand, 2,6-bis{[(2-(2-pyridyl)ethyl)(2-pyridylmethyl)-amino]-methyl}-4-methylphenol) (L1OH) reacts with Mn(ClO4)2.6H2O to form the dinuclear complex [Mn2(II,II)(L1O)(mu-OOCCH3)2]ClO4 (1). The electrolytic oxidation of 1 at 0.7 V (vs Ag/AgCl) produces the mixed valent complex [Mn2(II,III)(L1O)(mu-OOCCH3)2](ClO4)2 (1ox) quantitatively, while electrolysis at 0.20 V converts 1ox back to 1. X-ray crystallographic structures show that both 1 and 1ox are dinuclear complexes in which the two manganese ions are each in distorted octahedral coordination environments bridged by the phenoxo oxygen and two acetate ions. The structural changes that occur upon the oxidation 1 to 1ox suggest an extended pi-bonding system involving the phenoxo ring C-O(phenoxo)-Mn(II)-N(pyridyl) chain. In addition, as 1 is oxidized to 1ox, the rearrangements in the coordination sphere resulting from the oxidation of one Mn(II) ion to Mn(III) are transmitted via the bridging Mn-O(phenoxo) bonds and cause structural changes that render the site of the second manganese ion unfit for the +3 state and hence unstable to reduction. Thus the electrolytic oxidation of 1ox in acetonitrile at 1.20 V takes up slightly greater than 1 F of charge/mol of 1ox, but the starting complex, 1ox, is recovered, showing the instability of the Mn2(III,III) state that is formed with respect to reduction to 1ox. Variable-temperature magnetic susceptibility measurements of 1 and 1ox over the temperature range from 1.8 to 300 K can be modeled with magnetic coupling constants J = -4.3 and -4.1 cm(-1), respectively showing the weak antiferromagnetic coupling between the two manganese ions in each dinuclear complex, which is commonly observed among similar phenoxo- and bis-1,3-carboxylato-bridged dinuclear Mn2(II,II) and Mn2(II,III) complexes. 相似文献
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Daniel B. Larsen Dr. Allan R. Petersen Dr. Johannes R. Dethlefsen Dr. Ayele Teshome Dr. Peter Fristrup 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(46):16621-16631
The molybdate‐catalysed transfer hydrodeoxygenation (HDO) of benzyl alcohol to toluene driven by oxidation of the solvent isopropyl alcohol to acetone has been investigated by using a combination of experimental and computational methods. A Hammett study that compared the relative rates for the transfer HDO of five para‐substituted benzylic alcohols was carried out. Density‐functional theory (DFT) calculations suggest a transition state with significant loss of aromaticity contributes to the lack of linearity observed in the Hammett study. The transfer HDO could also be carried out in neat PhCH2OH at 175 °C. Under these conditions, PhCH2OH underwent disproportionation to yield benzaldehyde, toluene, and significant amounts of bibenzyl. Isotopic‐labelling experiments (using PhCH2OD and PhCD2OH) showed that incorporation of deuterium into the resultant toluene originated from the α position of benzyl alcohol, which is in line with the mechanism suggested by the DFT study. 相似文献
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Lemma Teshome Tufa Khalid Siraj Tesfaye Refera Soreta 《Russian Journal of Electrochemistry》2013,49(1):59-66
Electrochemical application of bismuth film modified glassy carbon electrode was studied with the objective of lead detection. Bismuth film on glassy carbon substrate was formed in a plating solution of 2 mmol/L Bi(NO3)3, in 1 mol/L HCl at ?1.1 V (vs. Ag/AgCl) for 300 s. Lead was detected by differential pulse anodic voltammetry in acetate buffer of pH 5.0 in the concentration range of 7.5 nmol/L to 12.5 μmol/L. Factors influencing the anodic stripping performance, including deposition time, solution pH, Bi(III) concentration, potential, pulse amplitude, pulse width, have been optimized. Three linear calibration plots in the range 7.5 nmol/L to 0.1 μmol/L, 0.25 to 1 μmol/L, 2.5 to 12.5 μmol/L with regression coefficients of 0.991, 0.986 and 0.978 respectively were obtained. The theoretical detection limit equivalent to three times standard deviation for 7.5 nmol/L lead (n = 5) was calculated to be 5.25 nmol/L utilizing a 5 min deposition time and sensitivity 83.97 A L/mol. The sensitivity and detection limit of the method was compared with reported voltammetric methods for detection of lead and the result obtained was found to be promising for determination of lead. 相似文献
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2D spin-dependent scattering of slow unpolarized beams of electrons by charged nanomagnets is analyzed in the Born approximation. The obtained scattering lengths are larger than those from the neutral nanomagnets approximately by one order. It is shown that for particular parameters of the system it is possible to polarize completely the scattered electrons in a narrow range of scattering angles. The most suitable system for realization of these effects is 2D Si electron gas with immersed nanomagnets. 相似文献
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Teshome B. Yisgedu Dr. Xuenian Chen Dr. Scott Schricker Prof. Jon Parquette Prof. Edward A. Meyers Dr. Sheldon G. Shore Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(9):2190-2199
Chains of cages : Neutral/ionic [B12H12]2? boron‐cage‐functionalized methacrylate and styrene homopolymers or copolymers (see picture) are non‐crystalline solids, Tg increases as the number of B12 cages in the chain of polystyrene increases, and homopolymers retain more weight than the copolymers when heated to 400 °C.