Small molecule diffusion in a rubbery polymer near Tg: Effects of probe size,shape, and flexibility

A novel experimental approach involving fluorescence nonradiative energy transfer (NRET) is employed to study the Fickian diffusion of small molecules in rubbery poly(isobutyl methacrylate) (PiBMA) films near the glass transition, using a formalism that directly relates the small molecule translational diffusion coefficient, D, to changes in the normalized nonradiative energy transfer efficiency, E_N. Values of D for pyrene, 1,3-bis-(1-pyrene) propane (BPP), 1,3-bis-(1-pyrene) decane (BPD), 9,10-bis-phenyl ethynyl anthracene (BPEA), diphenyl Disperse Red 4 (DPDR4), and decacyclene in PiBMA are measured over temperatures ranging from approximately T_g to T_g + 25°C. Among these chromophores, significant differences in both the magnitude and temperature dependence of D are observed which are attributed to differences in molecule shape and flexibility, as well as molar volume. Other factors being equal, chromophore flexibility was shown both to increase the magnitude of D and to decrease its dependence on temperature, as does an increase in aspect ratio. For BPD, these effects are attributed to the ability of the flexible molecule to diffuse in a piecewise manner, requiring the cooperative mobility of fewer polymer chain segments than a rigid molecule of the same molar volume. For BPEA and DPDR4, this deviation from D being dominated by molar volume effects is attributed the to high aspect ratio of these elongated molecules. © 1996 John Wiley & Sons, Inc.     

The use of carbon black-supported sulfuric acid to initiate the cationic polymerization of cyclic ketene acetals

Stable polymers were made by the cationically initiated 1,2-polymerization of cyclic ketene acetals employing heterogeneous, activated carbon-supported sulfuric acid catalysts. A methodology has been established for the preparation of the carbon black of different acidic strengths. By adjusting either the acid strength or the amount of carbon black used, cyclic ketene acetals with different activities can be polymerized efficiently to form stable high molecular weight polymers. This methodology will be a useful tool for polymerization, copolymerization, and studies of the relative reactivities of the cyclic ketene acetals. The polymer structures were determined by FTIR, ¹³C-NMR, and ¹H-NMR studies. © 1996 John Wiley & Sons, Inc.     

异硫氰酸荧光素-溶菌酶的制备及晶体生长预研究

迄今尚未有适用于光源为488 nm激光扫描共聚焦显微镜研究用的溶菌酶. 为此, 用异硫氰酸荧光素作为探针标记了溶菌酶, 测定了溶菌酶标记物的紫外-可见吸收光谱和荧光光谱, 摸索了其晶体的生长条件. 实验结果表明, 在标记过程中异硫氰酸荧光素没有影响溶菌酶的生化性质, 标记后的溶菌酶可用于激光扫描共聚焦显微镜进行后续研究.     

Cu2＋和铜锌超氧化物歧化酶作用的光谱学研究

利用邻苯三酚自氧化法监测在磷酸盐缓冲体系中Cu^2＋对猪肝铜锌超氧化物歧化酶(CuZnSOD)活力的影响, 认为Cu^2＋与猪肝CuZnSOD存在直接相互作用. 通过荧光光谱方法研究了这种相互作用, 内源荧光的猝灭实验表明Cu^2＋与CuZnSOD形成1∶1型稳定配合物; 荧光猝灭的动力学分析表明配合物形成过程由两个独立步骤完成: 第一步是双分子快速缔合过程, 形成了结合疏松的配合物, 第二步是单分子慢速过程, 即松散的配合物“异构化”成为结合紧密的配合物. FTIR和CD证实相互作用过程伴随了蛋白分子构象的变化.     

瓜环与2,2''''-联吡啶衍生物的相互作用

利用~1H NMR技术、紫外吸收光谱及荧光光谱方法,考察了对六、七以及八元瓜环与多种2,2'-联吡啶衍生物相互作用形成的主客体配合物结构及光学性质.研究结果显示,不同的2,2'-联吡啶衍生物与瓜环作用不仅形成多种不同包结比的稳定包结配合物,且所形成的主客体包结配合物的结构及光谱性质也各不相同;同时用几种方法协同考察起到了互为补充、互为验证的良好效果.     

脂肪胺荧光衍生物的高效液相色谱分离及质谱鉴定

采用新型荧光衍生试剂2-(9-吖啶酮)-乙酸(AAA)进行柱前衍生并经荧光检测对脂肪胺进行了高效液相色谱(HPLC)分离和在线质谱定性.衍生物荧光激发和发射波长为λex=404nm,λem=440nm.30℃下在乙腈溶剂中用N-乙基-N′-[(3-二甲氨基)丙基]碳二亚胺盐酸盐(EDC)做催化剂,衍生反应20min后获得稳定的荧光产物.在HypersilBDSC18(4.6mm×100mm,5μm)色谱柱上,采用梯度洗脱对12种脂肪胺衍生物进行了优化分离.采用大气压化学电离源(APCISource)正离子模式进行在线柱后质谱定性,实现了各种脂肪胺衍生物的快速、准确测定.该方法具有良好的重现性,多数脂肪胺的线性回归系数大于0.9996,检测限为12.09~25.52fmol.     

三元铕配合物Eu(DBM)3L1的合成、晶体结构及发光性能

新型三元铕配合物Eu(DBM)3L1(DBM=二苯甲酰甲烷,L1=2-(3-硝基苯基)-咪唑并[4,5-f]-1,10-邻二氮杂菲)的晶体属单斜晶系,Cc空间群.中心铕离子分别与DBM配体的六个氧原子和第二配体的两个鳌合氮原子配位,形成八配位的扭曲四方反棱柱构型.配合物中性配体的共轭平面与相邻分子的DBM苯环平面(C(25),C(26),C(27),C(28),C(29))之间有明显的π-π相互作用.在紫外光激发下,配合物表现出较强的Eu3+的特征发射,第二配体对中心离子有较强的敏化发光作用.     

活性炭载体的超声波处理对钌/活性炭氨合成催化剂催化性能的影响

 利用超声波处理活性炭,并采用场发射扫描电镜、X射线能谱、N2物理吸附和CO化学吸附等表征手段,考察了超声波处理对活性炭表面形貌、化学组成、表面织构和催化剂钌分散度的影响. 以超声波处理的活性炭为载体,以钡和钾为助剂制备了一系列钌基氨合成催化剂,在10.0 MPa,10000 h-1和400 ℃的条件下进行了氨合成活性评价. 结果表明,超声波处理可有效除去活性炭表面的杂质,提高中孔比表面积占BET比表面积的比例. 超声波处理50 min的活性炭表面的杂质含量较低,中孔比表面积适中,以其为载体制备的钌基催化剂的活性较高,催化氨合成反应速率可达94.8 mmol/(g·h).     

微波消解-氢化物发生原子荧光法测定塑料原料及其制品中的砷、汞

采用微波消解进行样品前处理，以硫脲为预还原剂，用氢化物发生原子荧光法测定塑料原料及其制品中的砷、汞。测定砷和汞的线性范围均为0～8μg／L，砷、汞的检出限分别为0．005、0．076μg／L，测定结果的相对标准偏差分别为4.96％～7．38％、2．94％～7．20％(n=6)，回收率分别为92．0％～103．2％、92．0％～98.0％。     

铅、汞、镉离子的荧光传感器研究进展

化学传感器提供了方便、快捷、廉价的分析检测有毒重金属离子的方法,并具有很高的灵敏度和选择性.它在环境科学、分析化学以及生命科学等领域有广泛的应用前景.本文分别综述了pb²⁺、Hg²⁺、Cd²⁺几种有毒重离子化学传感器的最新研究进展,并展望了该领域的发展趋势.