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通过后合成修饰方法(PSM)构筑了空心纳米球(Void@UiO-66-Ⅰ)和实心块(UiO-66-Ⅰ) 2种形貌的季铵盐功能化UiO-66-NH2(Zr), 得到兼具酸碱活性位点和氢键给体的新型功能化金属-有机框架材料. 通过一系列表征证明2种催化剂的成功合成, 并将它们用于催化转化CO2和氧化苯乙烯的环加成反应. 由于Void@UiO-66-Ⅰ催化剂的季铵盐部分含有大量的羟基和卤素阴离子, 可以通过氢键和亲核攻击与环氧化合物连接, 诱导环氧化合物开环, 促使反应顺利进行, 且催化剂的中空结构有利于物质进出催化剂, 起到加快反应速率的作用, 使得该催化剂在CO2与氧化苯乙烯环加成反应中表现出比实心块UiO-66-Ⅰ催化剂更好的催化性能. Void@UiO-66-Ⅰ催化剂在120 ℃, CO2压力为1.2 MPa, 反应时间为6 h, 无溶剂和助催化剂的反应条件下, 碳酸苯乙烯酯的收率和选择性分别为85.5%和95%. 相似文献
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Jianxun Li Jihao Shan Zhiqiang Kong Chunlin Fan Zijuan Zhang Bei Fan 《Journal of separation science》2020,43(2):486-495
In this study, an effective speed‐regulated directly suspended droplet microextraction method was developed to condense pesticide residues from teas through dispersive solid‐phase extraction prior to analysis by gas chromatography with tandem mass spectrometry. The extractant was intentionally dispersed into the sample solution in the form of globules through high‐speed agitation. This procedure increases the contact area between the binary phases and shortens the distribution equilibrium time. The fine globules reassembled by decelerating stirring speed, the extractant could be taken out for gas chromatography with tandem mass spectrometry. Recovery studies were performed under optimized extraction conditions by using matrix blanks fortified with pesticides at three concentrations (10, 50, and 100 µg/kg). Over 87% of the recoveries for the analytes in four tea matrices were acceptable given their recovery ranges of 70–120% and relative standard deviations of ≤20%. The limits of quantification of most pesticides were lower than 10 µg/kg and thus satisfied the requirements for maximum residue levels prescribed by the European Community. A total of 38 tea samples from local markets were analyzed by using the proposed method. Results showed that chlorpyrifos was the most frequently detected pesticide in teas. The method is a potential choice for the routine monitoring of pesticide residues in complex matrices. 相似文献
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Jianxun Li Xiaoyu Teng Wenwen Wang Zijuan Zhang Chunlin Fan 《Journal of separation science》2019,42(11):1990-2002
In this work, gas chromatography tandem with electron ionization and full‐scan high‐resolution mass spectrometry with a time‐of‐flight mass analyzer was evaluated for analyzing pesticide residues in teas. The relevant aspects for mass spectrometry analysis, including the resolution and mass accuracy, acquisition rate, temperature of ion source, were investigated. Under acquisition condition in 2‐GHz extended dynamic range mode, accurate mass spectral library including 184 gas chromatography detectable pesticides was established and retrieval parameters were optimized. The mass spectra were consistent over a wide concentration range (three orders) with good match values to those of NIST (EI‐quadrupole). The methodology was verified by the validation of 184 pesticides in four tea matrices. A wide linear range (1–1000 μg/kg) was obtained for most compounds in four matrices. Limit of detection, limit of quantification, and limit of identification values acquired in this study could satisfy the requirements for maximum residue levels prescribed by the European Community. Recovery studies were performed at three concentrations (10, 50, and 100 μg/kg). Most of the analytes were recovered at an acceptable range of 70–120% with relative standard deviations ≤ 20% in four matrices. The potential extension of qualitative screening scope makes gas chromatography tandem with electron ionization and mass spectrometry with a time‐of‐flight mass analyzer a more powerful tool compared with gas chromatography with tandem mass spectrometry. 相似文献
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A new cholesterol-based gelator with orotate unit (cholesterol orotate) was synthesised. The morphology and structure of the gels were investigated by scanning electron microscopy and powder X-ray diffractions. It is observed that the addition of melamine modulated the supramolecular self-assembly and aggregation mode, which originated from the intermolecular non-covalent interactions, as revealed by FT-IR and UV–vis absorption spectra. 相似文献
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There are highly intensive and stable line-spectrums in the radiated noise of passive target,and different targets have line-spectrums with different frequencies.This paper puts forward Conventional BeamForming(CBF) variance-of-frequency detector,which weights bearing spectrum using the variance of frequency of line spectrum with maximum amplitude in each azimuth. It is able to suppress multi-target interferences effectively,and detect faint signal in the background of strong interferences.What’s more,CBF variance-of-frequency detector needs only three-dimension display,while other line-spectrum detectors require for four-dimension display.The simulation and trial data analysis show that the CBF variance-of-frequency detector is able to detect faint line-spectrum target in the background of the continuous spectrum strong interferences. 相似文献
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A facile and efficient method for synthesis of 3-arylthiazol-2(3H)-one through the reaction of acyl azide and 1,4-dithiane-2,5-diol was reported. This reaction proceeded at 80?°C at first and then in acidic condition at room temperature, to afford products in good yields for a wide range of substrates and a possible mechanism has also been proposed. 相似文献
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一种基于频率方差加权的线谱目标检测方法 总被引:11,自引:0,他引:11
在复杂的多目标声场中,常规波束形成(CBF)检测器性能显著下降。本文提出一种基于频率方差加权的线谱目标检测方法——CBF频率方差检测器,利用被动目标辐射噪声中含有高强度的稳定线谱这一特征,用每个方位频率域的峰值频率方差对CBF输出的方位谱进行加权。该检测器可在多目标强干扰和同波束强相干干扰背景中检测到弱线谱目标,且只须三维显示,避开了传统的线谱检测四维显示的难点。仿真和海试结果表明,在多目标、强干扰的环境下,可以探测到弱线谱目标。 相似文献
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