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11.
Basheer C Wong W Makahleh A Tameem AA Salhin A Saad B Lee HK 《Journal of chromatography. A》2011,1218(28):4332-4339
Eight hydrazone-based ligands were synthesized, trapped in a silica sol-gel matrix, and were subsequently used in the micro-solid phase extraction (μ-SPE) of biogenic amines (BAs). The BAs investigated were tryptamine, phenylethylamine, putrescine, histamine, tyramine and spermidine. Prior to the extraction, dansyl chloride was added to the samples which were heated to 70°C for 10 min. The samples were extracted with μ-SPE, after which analytes were desorbed using acetonitrile via ultrasonication. The extracts were analysed by high performance liquid chromatography (HPLC) with ultraviolet detection. Of the eight ligands investigated as sorbents, benzophenone 2,4-dinitrophenylhydrazone was found to be the most promising. The enhanced π-π interaction between the analytes and the ligand facilitated the adsorption process. Under the most suitable extraction conditions, the method demonstrated good linearity with correlation coefficient of more than 0.985 over a concentration range of 1-50 μg L(-1). Satisfactory repeatability with relative standard deviations of 7.43-11.30% (n=3) were obtained. Detection limits ranged from 3.8 to 31.3 ng L(-1). The μ-SPE method exhibited lower recoveries (71.5-87.4%) when compared to the solid phase extraction technique (79.7-95.0%), but enrichment factors of 94-460 were obtained. The proposed μ-SPE-HPLC method was applied to the determination of BAs in orange juice purchased from local supermarkets, with satisfactory results. The orange juices were characterized by the presence of relatively high levels of putrescine (range, 550-2210 μg L(-1)) but tryptamine and phenylethylamine were not detected in any of the tested samples. 相似文献
12.
The oxidative decomposition mechanism of the lithium battery electrolyte solvent propylene carbonate (PC) with and without PF(6)(-) and ClO(4)(-) anions has been investigated using the density functional theory at the B3LYP/6-311++G(d) level. Calculations were performed in the gas phase (dielectric constant ε = 1) and employing the polarized continuum model with a dielectric constant ε = 20.5 to implicitly account for solvent effects. It has been found that the presence of PF(6)(-) and ClO(4)(-) anions significantly reduces PC oxidation stability, stabilizes the PC-anion oxidation decomposition products, and changes the order of the oxidation decomposition paths. The primary oxidative decomposition products of PC-PF(6)(-) and PC-ClO(4)(-) were CO(2) and acetone radical. Formation of HF and PF(5) was observed upon the initial step of PC-PF(6)(-) oxidation while HClO(4) formed during initial oxidation of PC-ClO(4)(-). The products from the less likely reaction paths included propanal, a polymer with fluorine and fluoro-alkanols for PC-PF(6)(-) decomposition, while acetic acid, carboxylic acid anhydrides, and Cl(-) were found among the decomposition products of PC-ClO(4)(-). The decomposition pathways with the lowest barrier for the oxidized PC-PF(6)(-) and PC-ClO(4)(-) complexes did not result in the incorporation of the fluorine from PF(6)(-) or ClO(4)(-) into the most probable reaction products despite anions and HF being involved in the decomposition mechanism; however, the pathway with the second lowest barrier for the PC-PF(6)(-) oxidative ring-opening resulted in a formation of fluoro-organic compounds, suggesting that these toxic compounds could form at elevated temperatures under oxidizing conditions. 相似文献
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近年来,分子内环加成反应已广泛用于甾体化合物全合成,其主要一步是由取代的苯并环丁烯热裂而成的5,6-二亚甲基-1,3-环己二烯发生区域专一和立体选择性的环加成反应,构成甾体骨架。现在用此法已合成了一系列消旋和光学活性的甾体化合物。 相似文献
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Caiyun Lin Yuying Li Weishan Tang Shufeng Zhou Xiaoping Rao 《Molecules (Basel, Switzerland)》2021,26(21)
Supramolecular hydrogels have attracted great attention due to their special properties. In this research, bio-based supramolecular hydrogels were conveniently constructed by heating and ultrasounding two components of dehydroabietic acid with a rigid tricyclic hydrophenanthrene skeleton and morpholine. The microstructures and properties of hydrogels were investigated by DSC, rheology, SAXS, CD spectroscopy, and cryo-TEM, respectively. The critical gel concentration (CGC) of the hydrogel was 0.3 mol·L−1 and the gel temperature was 115 °C. In addition, the hydrogel showed good stability and mechanical properties according to rheology results. Cryo-TEM images reveal that the microstructure of hydrogel is fibrous meshes; its corresponding mechanism has been studied using FT-IR spectra. Additionally, oil-in-water gel emulsions were prepared by the hydrogel at a concentration above its CGC, and the oil mass fraction of the oil-in-water gel emulsions could be freely adjusted between 5% and 70%. This work provides a convenient way to prepare bio-based supramolecular hydrogels and provides a new method for the application of rosin. 相似文献
18.
Zhao Fu Hongliang Feng Chanjuan Sun Xingdeng Xiang Wei Wu Jiancheng Luo Qingping Hu Anbo Feng Weishan Li 《Journal of Solid State Electrochemistry》2013,17(8):2167-2172
Polyethylene-supported polymethyl methacrylate/poly(vinylidene fluoride-co-hexafluoropropylene) separator for gel polymer lithium-ion battery use was prepared with a mixed solvent of n-butanol and acetone. The prepared separator was characterized with scanning electron spectroscopy and X-ray diffraction, and its performance was investigated by electrochemical impedance spectroscopy and battery charge/discharge test. Compared to the separator prepared with acetone, the separator prepared with the mixed solvent shows an enhanced porosity (from 42 to 49 %) and electrolyte uptake (from 104 to 125 %). The ionic conductivity of the corresponding gel polymer electrolyte is improved from 2.81 to 3.39 mS cm?1, the discharge capacity retention of the LiCoO2/artificial graphite battery is increased from 95 to 98 % after 100 cycles at 0.5 C, and the discharge capacity of the battery at 1 C increases by 4 %. 相似文献
19.
Xingde Xiang Weishan Li Zhihui Zhou Zhao Fu Jianfei Lei Yuli Lin 《Journal of Solid State Electrochemistry》2010,14(5):903-908
A new electrocatalyst, Pt/HxMoO3-C, for methanol oxidation, was prepared by dispersing platinum nano-particles on Vulcan XC-72 modified by hydrogen molybdenum
bronze (HxMoO3, 0 ≤ x ≤ 2). The modification of Vulcan XC-72 with HxMoO3 on was accomplished by reducing the adsorbed molybdic acid and the platinum nano-particles were dispersed on the modified
carbon by reducing chloroplatinic acid, with formaldehyde as the reductant. The prepared Pt/HxMoO3-C was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersion spectrometer, cyclic
voltammetry (CV), chronoamperometry (CA), and single-cell test, with a comparison of the electrocatalyst, carbon-supported
platinum (Pt/C) prepared under the same condition but without the modification. The results obtained from XRD and SEM showed
that the modification of Vulcan XC-72 with HxMoO3 reduced the platinum particle size and improved distribution uniformity of platinum on carbon. The results, obtained from
CV, CA, and the single-cell test, showed that Pt/HxMoO3-C exhibited better electrocatalytic activity toward methanol oxidation than Pt/C. 相似文献
20.
Jianfei Lei Xiaoping Li Weishan Li Fengqiang Sun Dongsheng Lu Yuli Lin 《Journal of Solid State Electrochemistry》2012,16(2):625-632
Arrayed porous iron-doped TiO2 was prepared by sol–gel with polystyrene spheres as template and used as photocatalyst for the degradation of methyl orange.
The structure and performances of the prepared photocatalyst were characterized with X-ray diffractometer, inductively coupled
plasma-atomic emission spectrometer, scanning electron microscope, UV-visible spectrometer, and methyl orange degradation
tests. It is found that the iron dopant does not change the crystal phase of TiO2 but affects its lattice constant, optical absorption, electronic conductivity, charge-transfer resistance, and activity toward
the degradation of methyl orange. The sample doped with 0.01 wt.% Fe (based on Ti) and with smaller pore size exhibits the
better photocatalytic activity. The degradation rate of methyl orange on the sample with a pore size of 190 nm is 2.3 times
that on the undoped sample with the same pore size. 相似文献