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排序方式: 共有664条查询结果,搜索用时 15 毫秒
31.
采用同轴静电纺丝技术,以硝酸铈、硝酸锌、聚乙烯吡咯烷酮、N,N-二甲基甲酰胺、甘油和氯仿为原料,制备了ZnO@CeO2 同轴纳米电缆。用差热–热重分析、X射线衍射、扫描电镜、透射电镜和能谱仪对样品进行了表征。结果表明,所得到的产物为ZnO@CeO2同轴纳米电缆,以晶态CeO2为壳层,晶态ZnO为芯层,电缆直径约90 nm,芯层直径约60 nm,壳层厚度约15 nm,电缆长度>300 μm,对其形成机理进行了分析。 相似文献
32.
以Ce3+为中心离子,N,N-二甲基甲酰胺(DMF)为有机配体,通过温度调节,合成系列形貌和电化学信号不同的铈配合物(Ce-COPs)。筛选出电化学信号最强的多面体状Ce-COP为信号探针。通过凝血酶(TB)与TB适体链之间的特异性识别作用,设计了一种简单通用的TB适体传感器。最优实验条件下,该传感器对TB的线性响应范围为1.0 fmol·L-1~1.0 nmol·L-1,检测限为0.94 fmol·L-1。此外,本方案方法与商品人凝血酶(TM) ELISA试剂盒检测结果相近。结果表明,我们构建的TB适体传感器具有良好的灵敏度、特异性、选择性和稳定性。 相似文献
33.
Electrospun cerium nitrate/polymer composite fibres: synthesis, characterization and fibre-division model 下载免费PDF全文
Cerium (Ⅲ) nitrate/poly(vinylpyrrolidone) (Ce(NO3)3/PVP) composite fibres have been prepared by electrospinning. After calcining the composite fibres in air at 500℃,CeO2 nanowires were obtained. The characterizations of the as-spun composite fibres and resultant nanowires have been carried out by a scanning electron microscope (SEM),an infrared spectrometer,an x-ray diffractometer and a fluorescence spectrophotometer. Interestingly,some unusual ribbon-like or twin fibres were observed besides the common fibres with circular or elliptic cross sections. We developed a fibre-division model resulting from Coulomb repulsion and solvent vaporization to interpret the formation of the ribbons or twin fibres,which has been confirmed by the SEM studies. Our results also indicate that the formation of the ribbons or twin fibres is less dependent on operation voltage and work distance. 相似文献
34.
For the first time, polyaniline-coated cerium oxide nanoparticles were synthesized in alkaline media and applied for preconcentration of ultra-trace levels of cadmium (??) in different real samples followed by electrothermal atomic absorption spectrometry. Cerium oxide nanoparticles were synthesized by a microwave method and modified by polyaniline to produce polyaniline-coated cerium oxide nanoparticles. Fourier-transform infrared spectroscopy and scanning electron microscopy were used to characterize the synthesized adsorbent. To optimize the critical experimental conditions; surface response methodology—Box–Behnken experimental design was used. On the basis of the results, pH 8.4, 10?mg of polyaniline-coated cerium oxide nanoparticles, 14.4?min extraction time, and 4.3?min desorption time were selected as the optimum conditions. Under the optimum conditions the calibration curve of cadmium (??) was linear in the range of 0.02–0.4?ng?mL?1 with a correlation coefficient of 0.9976. The relative standard deviation based on seven replicate analysis of 0.1?ng?mL?1 cadmium (??) was 4.2% and limit of detection was 0.005?ng?mL?1 cadmium (??). The analysis of certified reference material shows very good agreement with the certified value. Finally, the proposed method was applied for the determination of ultra-trace levels of cadmium (??) in different water, rice, and tea samples. 相似文献
35.
Sergey I. Lopatin Sergey M. Shugurov Andrej I. Panin 《Journal of mass spectrometry : JMS》2019,54(6):507-519
Gaseous CePO2 has been identified by Knudsen effusion mass spectrometry during vaporization of CeO2 and magnesium diphosphate from tungsten double, two‐temperature effusion cell. Structure and molecular parameters of gaseous cerium phosphate under study were determined using quantum chemical calculations. On the basis of equilibrium constants measured for gas‐phase reaction, standard formation enthalpy of CePO2 was determined to be ?508 ± 41 kJ ? mol?1 at the temperature 298 K. 相似文献
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37.
分别以Y沸石、活性碳和二氧化硅-壳聚糖(SiO2-CS)为载体、利用浸渍法制备了一系列负载型七水三氯化铈-碘化钠(CeCl3·7H2O-NaI)催化剂,考察了它们在叔丁基苯基醚的脱保护反应中的催化性能。 结果表明,SiO2-CS为载体的催化剂呈现出良好的催化性能和较高的稳定性。 另外,在中性条件下,SiO2-CS负载CeCl3·7H2O-NaI催化剂在叔丁基醚及1,3-二硫缩醛脱保护反应中呈现出较高的催化活性,从而避免使用强酸和强碱。 相似文献
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39.
Ru Zhang Shiquan Tan Bianling Zhang Pengcheng Hu Ling Li 《Molecules (Basel, Switzerland)》2021,26(18)
Among rare earth elements, cerium has the unique ability of regulating the growth of plant cells and the biosynthesis of metabolites at different stages of plant development. The signal pathways of Ce3+-mediated ginsenosides biosynthesis in ginseng hairy roots were investigated. At a low concentration, Ce3+ improved the elongation and biomass of hairy roots. The Ce3+-induced accumulation of ginsenosides showed a high correlation with the reactive oxygen species (ROS), as well as the biosynthesis of endogenous methyl jasmonate (MeJA) and ginsenoside key enzyme genes (PgSS, PgSE and PgDDS). At a Ce3+ concentration of 20 mg L−1, the total ginsenoside content was 1.7-fold, and the total ginsenosides yield was 2.7-fold that of the control. Malondialdehyde (MDA) content and the ROS production rate were significantly higher than those of the control. The activity of superoxide dismutase (SOD) was significantly activated within the Ce3+ concentration range of 10 to 30 mg L−1. The activity of catalase (CAT) and peroxidase (POD) strengthened with the increasing concentration of Ce3+ in the range of 20–40 mg L−1. The Ce3+ exposure induced transient production of superoxide anion (O2•−) and hydrogen peroxide (H2O2). Together with the increase in the intracellular MeJA level and enzyme activity for lipoxygenase (LOX), there was an increase in the gene expression level of MeJA biosynthesis including PgLOX, PgAOS and PgJMT. Our results also revealed that Ce3+ did not directly influence PgSS, PgSE and PgDDS activity. We speculated that Ce3+-induced ROS production could enhance the accumulation of ginsenosides in ginseng hairy roots via the direct stimulation of enzyme genes for MeJA biosynthesis. This study demonstrates a potential approach for understanding and improving ginsenoside biosynthesis that is regulated by Ce3+-mediated signal transduction. 相似文献
40.