活性氮与溴分子反应的实验研究

在流动反应管中, 利用高纯N₂空心阴极放电制备活性氮, 研究了活性氮与溴分子碰撞反应得到的发射光谱. 在540～800 nm波段观察到了较强的NBr(b¹Σ^＋→X³Σ^－)跃迁发射谱, 在292 nm处观察到了Br₂(D'→A')辐射跃迁. 实验结果表明, 得到的NBr(b¹Σ^＋)显示出了非弛豫的发射特征, 最高振动能级为ν'＝9. 激发态的NBr(b¹Σ^＋)是由活性氮中的N(²P)原子与Br₂直接反应生成的.     

Equilibrium Studies on Reactive Extraction of α-Cyclohexylmandelic Enantiomers Using Hydrophilic β-Cyclodextrin Derivatives Extractants

β‐Cyclodextrin (β‐CD) is negligibly soluble in organic liquids and can be modified to achieve a higher solubility in water. In this paper, racemic α‐cyclohexyl‐mandelic acid (α‐CHMA) was separated by chiral reactive extraction with aqueous β‐cyclodextrin derivatives. Hydroxypropyl‐β‐cyclodextrin (HP‐β‐CD), hydroxyethyl‐β‐cyclodextrin (HE‐β‐CD), and methyl‐β‐cyclodextrin (Me‐β‐CD) were selected as chiral selectors for reactive extraction of α‐CHMA enantiomers from organic phase to aqueous phase. Factors affecting the extraction efficiency were investigated, including the types of organic solvents and β‐CD derivatives, the concentrations of the chiral selector and α‐CHMA enantiomers, pH and temperature. The experimental results demonstrate that HP‐β‐CD, HE‐β‐CD, and Me‐β‐CD have stronger recognition abilities for S‐α‐CHMA than for R‐α‐CHMA. Among the three derivatives, HP‐β‐CD shows the strongest separation factor for α‐CHMA enantiomers. A high enantioseparation efficiency with a maximum separation factor (α) of 2.02 is observed at pH 2.5 and 5°C.     

均匀设计RulrSnLa/Ti氧化物涂层的回归与灰色关联分析

对RuIrSnLa四元金属氧化物涂层的组成进行了研究.采用均匀设计、偏最小二乘回归(PLS)与灰色关联度分析相结合的方法,以使用寿命、伏安电量、析氯电位、析氧电位及析氧析氯电位差为考察指标,对电化学性能的影响因素进行了主次分析,并对涂层配方进行了优选.结果表明:Ir对提高阳极的使用寿命影响最大.其次是Ru,Sn是提高析氧电位的主要元素,而La对提高阳极电催化活性,降低析氯电位及增大析氧析氯电位差起着主要作用,PLS分析认为,La对阳极稳定性呈负效应.采用偏最小二乘回归与灰色关联度相结合的分析方法,可以优势互补,为多元金属氧化物涂层的成分设计和理论研究提供依据.     

含噻唑环的二肽基肽酶Ⅳ抑制剂的设计、合成和降血糖活性研究

设计并合成了16个含噻唑环的二肽基肽酶Ⅳ(DPP-Ⅳ)抑制剂,利用IR,1H NMR,13C NMR和HR-MS表征了它们的结构.通过小鼠口服糖耐量实验测试了它们的降血糖作用,结果显示其中两个化合物具有很强的降血糖作用,一个与格列齐特相当,另一个强于格列齐特,显示了在治疗Ⅱ型糖尿病方面的前景.构效关系研究发现,这16个化合物的构效关系呈现出明显的规律.     

Synthesis of an AIE-active fluorogen and its application in cell imaging

A fluorogen named 1-decyl-1-methyl-2,5-bis{4-[(N,N-diethylamino)methyl]phenyl}-3,4-diphenylsilole (3) was synthesized. It emitted weakly as isolated molecule but strongly as supramolecular aggregate, showing a characteristic behavior of aggregation-induced emission (AIE). The molecules of 3 formed highly emissive nanoparticles in aqueous media, which quickly and selectively marked cytoplasm of HeLa cells and posed no toxicity to the living cells. The fluorogen is thus a promising candidate material for cell imaging as a sensitive, selective and cytocompatible biosensor. Supported by the Research Grants Council of Hong Kong (Grant Nos. 603008, 601608 and 602707), the National Natural Science Foundation of China (Grant No. 20634020) and the CAO GuangBiao Foundation of Zhejiang University.     

The effect of nanolayer AlF<Subscript>3</Subscript> coating on LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> cycle life in high temperature for lithium secondary batteries

The surface of the spinel LiMn₂O₄ was coated with AlF₃ by a chemical process to improve its electrochemical performance at high temperatures. The morphology and structure of the original and AlF₃-coated LiMn₂O₄ samples were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM). All the samples exhibited a pure cubic spinel structure without any impurities in the XRD patterns. It was found that the surfaces of the original LiMn₂O₄ samples were covered with a nanolayer AlF₃ after the treatment. The charge/discharge of the materials were carried at 220 mA/g in the range of 3.0 and 4.4 V at 55°C. While the original LiMn₂O₄ showed 17.8% capacity loss in 50 cycles at 55°C, the AlF₃-coated LiMn₂O₄ (118.1 mA h/g) showed only 3.4% loss of the initial capacity (122.3 mA h/g) at 55°C. It is obvious that the improvement in cycling performance of the coated-LiMn₂O₄ electrode at 55°C is attributed to the presence of AlF₃ on the surface of LiMn₂O₄. Published in Russian in Elektrokhimiya, 2009, Vol. 45, No. 7, pp. 817–819. The article is published in the original     

Ozone source attribution during a severe photochemical smog episode in Beijing, China

Beijing,the capital of China,frequently suffers from the high levels of ozone in summer.A 3-D regional chemical transport model,the Comprehensive Air Quality Model with extensions(CAMx),has been used to simulate a heavy O3 pollution episode in Beijing during June 26―July 2,2000.Ozone Source Apportionment Technology(OSAT) and Geographic Ozone Assessment Technology(GOAT) were applied to quantify the contributions of the precursor emissions from different regions to O3 concentrations in Beijing,to identify the...     

Macroscopic and spectroscopic characterization of selenate, selenite, and chromate adsorption at the solid–water interface of γ-Al2O3

The interaction of selenate, selenite, and chromate with the hydrated surface of γ-Al₂O₃ was studied using a combination of macroscopic pH edge data, electrophoretic mobility measurements, and X-ray absorption spectroscopic analyses. The pH edge data show generally increased oxyanion adsorption with decreasing pH, and indicate ionic strength-(in)dependent adsorption of chromate and selenate across the pH range 4–9, and ionic strength-(in)dependent adsorption of selenite in this pH range. The adsorption of chromate peaks at pH 5.0, whereas for selenate and selenite no pH adsorption maxima are observed. Electrophoretic mobility measurements show that all three oxyanions decrease the zeta potential of γ-Al₂O₃ upon adsorption; however, only selenite decreased the pH_PZC of the γ-Al₂O₃ sorbent. EXAFS data indicate that selenite ions are coordinated in a bridging bidentate fashion to surface AlO₆ octahedra, whereas no second-neighbor Al scattering was observed for adsorbed selenate ions. Combined, the results presented here show that pH is a major factor in determining the extent of adsorption of selenate, selenite, and chromate on hydrated γ-Al₂O₃. The results point to substantial differences between these anions as to the mode of adsorption at the hydrated γ-Al₂O₃ surface, with selenate adsorbing as nonprotonated outer-sphere complexes, chromate forming a mixture of monoprotonated and nonprotonated outer-sphere adsorption complexes, and selenite coordinating as inner-sphere surface complexes in bridging configuration.     

Mesoporous SBA-15 materials modified with oxodiperoxo tungsten complexes as efficient catalysts for the epoxidation of olefins with hydrogen peroxide

A hybrid mesoporous SBA-15 material (2a) containing an oxodiperoxo tungsten complex of the type [WO(O₂)₂L] (L = pyrazolylpyridine) was synthesized by a post-grafting route. The organic–inorganic hybrid catalyst was characterized by means of XRD, N₂ adsorption–desorption and FT-IR. The catalytic property of 2a in the epoxidation of cyclooctene with H₂O₂ as the oxidant was investigated in comparison with other three kinds of hybrid tungsten containing SBA-15 materials bearing ethylenediamine, imidazole or 4,4′-bipyridine ligands. It was found that all oxodiperoxo tungsten catalysts were active at the reaction temperature of 55 °C with CH₃CN as solvent. However, only the catalyst with the pyrazolylpyridine ligand showed good recoverability and relatively high stability against leaching of active tungsten species. Moreover, this catalyst showed very high efficiency for H₂O₂ utilization, and its catalytic activity could be further improved by using solvent mixtures of CH₃CN and CH₃COOH.     

Studies on melt flow properties during capillary extrusion of PP/Al(OH)3/Mg(OH)2 flame retardant composites

The apparent melt shear viscosity of polypropylene (PP) composites filled with aluminium hydroxide (Al(OH)₃) and magnesium hydroxide (Mg(OH)₂) was measured by means of a melt flow rate instrument under experimental conditions of temperature ranging from 170 to 195 °C and load varying from 2.16 to 12.5 kg, to identify the effects of particle size and content. The results showed that the melt shear flow of the composites obeyed the power law under the experimental conditions, the dependence of the melt apparent shear viscosity (η_a) on temperature was consistent with the Arrhenius equation, and the sensitivity of the η_a for the composite melts to temperature increased with addition of flame retardant. The η_a of the composites decreased with increasing apparent shear rate. The η_a increased with an increase of the content of flame retardant, but this rate of increase decreased with a rise of temperature or load. When the particle size of flame retardant was smaller than 5 μm, the η_a of the composites increased with increase of particle size of flame retardant, and then reduced with a further increase of particle size of flame retardant.