多酸含量对无机/高分子复合薄膜结构及光致变色性能的影响

制备了一系列不同浓度的钨磷酸/聚乙烯醇(PWA/PVA)复合薄膜, 通过红外光谱、原子力显微镜、紫外-可见吸收光谱对复合薄膜的结构和光致变色性能进行了研究. 红外光谱分析结果表明, Keggin结构钨磷酸和聚乙烯醇分子的基本结构在复合薄膜中仍然存在, 钨磷酸分子与高分子底物间存在氢键作用, 形成电荷转移桥. 原子力显微镜(AFM)结果表明复合前后PVA薄膜表面形貌发生了显著变化, 复合膜表面形貌随钨磷酸含量的不同而不同. 在紫外光照射下, 复合薄膜由无色变为蓝色. 复合膜的升色速度和褪色速度均随着钨磷酸含量的增加而加快. 这些结果表明钨磷酸含量对复合膜的微结构存在影响, 从而导致了复合膜具有不同的光致变色性能.     

Amino acid catalyzed neogenesis of carbohydrates: a plausible ancient transformation

Hexose sugars play a fundamental role in vital biochemical processes and their biosynthesis is achieved through enzyme-catalyzed pathways. Herein we disclose the ability of amino acids to catalyze the asymmetric neogenesis of carbohydrates by sequential cross-aldol reactions. The amino acids mediate the asymmetric de novo synthesis of natural L- and D-hexoses and their analogues with excellent stereoselectivity in organic solvents. In some cases, the four new stereocenters are assembled with almost absolute stereocontrol. The unique feature of these results is that, when an amino acid is employed as the catalyst, a single reaction sequence can convert a protected glycol aldehyde into a hexose in one step. For example, proline and its derivatives catalyze the asymmetric neogenesis of allose with >99 % ee in one chemical manipulation. Furthermore, all amino acids tested catalyzed the asymmetric formation of natural sugars under prebiotic conditions, with alanine being the smallest catalyst. The inherent simplicity of this catalytic process suggests that a catalytic prebiotic "gluconeogenesis" may occur, in which amino acids transfer their stereochemical information to sugars. In addition, the amino acid catalyzed stereoselective sequential cross-aldol reactions were performed as a two-step procedure with different aldehydes as acceptors and nucleophiles. The employment of two different amino acids as catalysts for the iterative direct aldol reactions enabled the asymmetric synthesis of deoxysugars with >99 % ee. In addition, the direct amino acid catalyzed C(2)+C(2)+C(2) methodology is a new entry for the short, highly enantioselective de novo synthesis of carbohydrate derivatives, isotope-labeled sugars, and polyketide natural products. The one-pot asymmetric de novo syntheses of deoxy and polyketide carbohydrates involved a novel dynamic kinetic asymmetric transformation (DYKAT) mediated by an amino acid.     

现场热引发聚丙烯酸酯类电解质的性能及应用

应用热引发现场聚合方法制备聚丙烯酸酯类电解质,并考察其电化学性能.实验表明:该聚合物电解质具有 4. 5V的电化学稳定窗口,较高的室温电导率及良好的低温性能.当前驱体电解液中液态电解质含量为 85%时,其室温电导率为 3. 2×10-3S·cm-1, -30℃下的电导率达到 5. 6×10-4 S·cm-1.采用现场聚合技术制备的聚合物电池,其电化学性能与液态锂离子电池基本一致,首次充放电效率为 92. 1%, 1. 0C率放电容量为 0. 2C率的 95%, -20℃下的放电容量为室温容量的 72%,以 0. 5C率循环 300周后,仍保持初始容量的 85%以上.     

瓯柑石油醚提取物的GC-MS分析

为了研究瓯柑的挥发性成分和脂溶性成分, 采用GC-MS分析法进行分离鉴定, 并用面积归一法确定各成分的质量分数. 从瓯柑果肉石油醚提取物中分离鉴定出11种成分, 占总提取物的97.43%, 其主要成分为(Z, Z)-9, 12-十八碳二烯酸(37.46%)、γ-谷甾醇(22.91%);从瓯柑皮石油醚提取物中分离鉴定出10种成分, 占总提取物的99.79%, 其主要成分为柠檬烯(86.39%).     

四甲基吡啶卟啉与核酸相互作用的稳态和时间分辨光谱

采用稳态吸收和荧光光谱、圆二色谱和皮秒时间分辨荧光光谱手段, 研究了5,10,15,20-四[4-(N-甲基吡啶)]卟啉(TMPyP4)与腺嘌呤(A)、鸟嘌呤(G)、胸腺嘧啶(T)和胞嘧啶(C)等4种碱基, 以及相应的核苷、核苷酸和单链DNA的结合能力和光谱学性质. 研究结果发现, 嘌呤与TMPyP4的结合能力比嘧啶的强. 对于某一碱基系列, 结合能力强弱顺序依次为: 碱基~核苷<核苷酸<单链DNA. 时间分辨荧光谱研究发现, 除鸟嘌呤外, 核酸和TMPyP4复合物的荧光动力学均含有快(1~2 ns)和慢(约10 ns)两个衰减过程, 它们分别是由激基复合体和环境极性对激发态TMPyP4分子的影响所致. 单链DNA能诱导TMPyP4产生诱导圆二色信号, 而单分子(碱基、核苷、核苷酸)则无此功能.     

On the equivalence of acidic centers in H-beta zeolites tested by Fries rearrangement of phenyl acetate

The heterogeneously catalyzed liquid phase Fries rearrangement reaction of phenyl acetate was carried out on Beta zeolites reexchanged with different amounts of metal cations. The aim of this work was to determine the influence of the amount of Brønsted acid sites as the catalytic active centers on the conversion. Sodium and potassium ions as well as divalent calcium and zinc ions were used in the reexchange procedure. The conversion shows a linear dependency on the degree of ion reexchange following the theoretically expected values. So the results prove that the bridged hydroxyl groups are indeed the dominating active centers and that their strength seems to be independent of the degree of reexchange; consequently, their acidic strength should be identical. A special emphasis was placed on the reexchange with divalent metal ions. It was shown that one divalent ion is not able to replace two protons as is supposed to be necessary for the charge balance—so a 1:1 stoichiometry is needed to assume to explain the catalytic results.     

Synthesis,characterization, fluorescence and redox features of new <Emphasis Type="Italic">vic</Emphasis>-dioxime ligand bearing pyrene and its metal complexes

A new vic-dioxime ligand, N,N′-bis(aminopyreneglyoxime) (LH₂), and its copper(II), nickel(II) and cobalt(II) metal complexes were synthesized and characterized by elemental analyses, IR, UVVIS and ¹H and ¹³C NMR spectra (for the ligand). Mononuclear complexes were synthesized by a reaction of ligand (LH₂) and salts of Co(II), Ni(II), and Cu(II) in ethanol. The complexes have the metal-ligand ratio of 1: 2 and metals are coordinated by N,N′ atoms of vicinal dioximes. The ligand acts in a polydentate fashion bending through nitrogen atoms in the presence of a base, as do most vic-dioximes. Detection of a H-bonding in the Co(II), Ni(II), and Cu(II) complexes by IR revealed the square-planar MN₄ coordination of mononuclear complexes. Fluorescent properties of the ligand and its complexes arise from pyrene units conjugated with a vic-dioxime moiety. Fluorescence emission spectra of the ligand showed a drastic decrease in its fluorescence intensity upon metal binding. The electrochemical properties of the complexes were studied by the cyclic voltammetry technique. The nickel complex displayed an irreversible oxidation process while the copper complex exhibited a quasi-reversible oxidation and reduction processes based on the copper Cu(II)/Cu(III) and Cu(II)/Cu(I) couples, respectively.     

茶中儿茶素的分离分析方法研究进展

儿茶素类是茶叶药效的主要活性组分.天然产生的八大儿茶素为儿茶素(C)、表儿荼素(EC)、没食子儿茶素(GC)、表没食子儿荼素(EGC)、儿茶素没食子酸酯(CG)、表儿荼素没食子酸酯(ECG)、没食子儿荼素没食子酸酯(GCG)、表没食子儿茶素没食子酸酯(EGCG).本文综述了分离分析茶儿荼素的常用有效方法.     

正丁烷和异丁烷在改性纳米HZSM-5上的芳构化反应

用脉冲微反装置评价了正丁烷和异丁烷在氢型和锌改性的纳米ZSM-5催化剂上的反应活性和芳构化选择性.结果表明,在550℃下,异丁烷在氢型和不同锌负载量的纳米ZSM-5催化剂上的转化率都远高于正丁烷,但其芳构化选择性低于正丁烷.脱甲基活化是异丁烷和正丁烷的重要活化方式,也是影响其芳构化选择性的主要因素.锌改性在提高异丁烷和正丁烷转化率的同时,也促进了正丁烷和异丁烷的脱甲基活化.在混合丁烷进料反应的情况下,正丁烷和异丁烷的转化率与其单独进料时十分接近,这说明正丁烷和异丁烷共存时不会发生明显的竞争吸附和反应.纳米ZSM-5因晶粒度小,孔道短和微孔扩散阻力低而有利于异丁烷转化.     

氨基化镁铝类水滑石修饰电极及电化学杀菌

以层间插入十二烷基磺酸钠的镁铝类水滑石（Mg/Al-SDS-HTLc）,与十六烷基三甲基溴化铵（CTAB）和3-氨丙基三乙氧基硅烷（APS）缩合反应制备了氨基化镁铝类水滑石（Mg/Al-NH2-HTLc）。 然后以Mg/Al-NH2-HTLc修饰热解石墨电极,通过循环伏安法探讨了该电极对吸附在其表面的大肠杆菌的杀灭作用。 结果表明,被吸附的大肠杆菌在经过循环伏安扫描后死亡率达到98.68%,大肠杆菌的死亡可能是由于细胞膜中易氧化物质（如鸟嘌呤）被氧化所致。