Layer‐by‐Layer Assembly of Metal–Organic Frameworks in Macroporous Polymer Monolith and Their Use for Enzyme Immobilization

New monolithic materials comprising zeolitic imidazolate framework (ZIF‐8) located on the pore surface of poly(glycidyl methacrylate‐co‐ethylene dimethacrylate) monolith previously functionalized with N‐(3‐aminopropyl)‐imidazole have been prepared via a layer‐by‐layer self‐assembly strategy. These new ZIF‐8@monolith hybrids are used as solid‐phase carriers for enzyme immobilization. Their performance is demonstrated with immobilization of a model proteolytic enzyme trypsin. The best of the conjugates enable very efficient digestion of proteins that can be achieved in mere 43 s.

     

Facile preparation Pt on Au dendrites supported on Si (100) and their electrochemical properties for methanol and CO electrooxidation

A new simple, time-saving method of preparing highly dispersed Pt nanoparticles with large electrochemically active area (ECA) on three-dimensional dendrite-like Au supported on Si (100) was successfully developed by electroless displacement deposition (EDD). The as-prepared catalysts were characterized by field-emission scanning electron microscope and high-resolution transmission electron microscopy. The electro-catalytic properties of Pt/Au/Si for methanol and CO electrooxidation were investigated by cyclic voltammetry, chronoamperometry, and electrochemical impedances spectra. The results show that Pt/Au/Si catalyst prepared by EDD method presents the higher electro-catalytic activity and higher stability than that of Pt/Si composite. The electro-catalytic activity of Pt supported on Au could be enhanced with the growth of Au, leading to the higher electro-catalytic properties toward methanol and CO oxidation. The anodic peak of CO of Pt/Au/Si catalyst showed negatively shifted with respect to similarly prepared Pt/Si electrode. The supposed schematic of the reaction was also introduced. Overall, the approach provides a convenient method to prepare the Pt catalyst on Au dendrites with high ECA properties for DMFC and PEMFC through bottom-up assembly.     

双硫脲金(Ⅰ)配合物(Cl-)的红外光谱及热分解机理的研究

测定了双硫脲金(Ⅰ)配合物(Cl^-)的红外光谱、差热曲线(DTA)、热重曲线(TG);测定在21个不同温度下配合物发生分解反应后产物的红外谱图;提出了配合物热分解机理的一些论断;估算了热分解反应的活化能和指前因子;查明了双硫脲金(Ⅰ)配合物在升温速度为10℃/min条件下在230-260℃温度范围内配位体中硫脲能发生同分异构转变,硫脲转变为异硫氰酸铵;分解反应从～240℃开始,～322℃结束,650℃以上Au₂S分解为金属金。     

Ultrasonically initiated emulsion polymerization of methyl methacrylate

The ultrasonically initiated emulsion polymerization of methyl methacrylate (MMA) was investigated. Experimental results show that sodium dodecyl sulfonate (SDS) surfactant plays a very important role in obtaining a high polymer yield, because in the absence of SDS, monomer conversion is near zero. Thus, the surfactant serves as an initiator and as interfacial modifier in this system (MMA/H₂O), and the monomer conversion increases significantly with increasing SDS concentration. An increase in the reactor temperature also leads to an increase in the monomer conversion. An appropriate increase in the N₂ purging rate also leads to higher conversion. The conversion of MMA decreases with increasing monomer concentration because of the higher viscosity of the system. With the experimental results, optimized reaction conditions were obtained. Accordingly, a high monomer conversion of about 67% and a high molecular weight of several millions can be obtained in a period of about 30 min. Furthermore, transmission electron micrographs show that the latex particles prepared are nanosized, indicating a promising technique for preparing nanoscale latex particles with a small amount of surfactant. In conclusion, a promising technique for ultrasonically initiated emulsion polymerization has been successfully performed. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3356–3364, 2001     

8-(4-取代苯基)-10,10-二甲基-6-苯基-10 H-吡啶并[1,2-a]吲哚盐的合成

2,3,3-三甲基-3H-吲哚高氯酸盐与取代查耳酮在异戊醇中反应,得到五种新的8-(4-取代苯基)-10,10-二甲基-6-苯基-10 H-吡啶并[1,2-a]吲哚盐[R=Me_2N-(3a),R=MeO-(3b);R=Br-(3c),R=H-(3d);R=O_2N-(3e)]通过元素分析和光谱测定确证了产物的结构。紫外光谱表明,λ_(max)与R有关,其次序为Me_2N—>MeO—>Br—>H—>O_2N—     

一个可修的和可降级的控制系统可靠性和可行性

研究了一个可修的和可降级的控制系统的可靠性和可行性．该控制系统是由Ｌ（＝ｍ＋ｎ）个子系统构成的．其中有ｍ个子系统是两相同部件组成的温储备系统，另外ｎ个子系统是单部件系统．当其中某些子系统故障时，系统完成任务的能力有所下降，但系统仍可运行．当另一些子系统故障时，则系统故障．因此，它是一个可降级的系统．为了描述系统的这种性能，考虑了系统的可行性，该控制系统也是可修的．通过利用扩展Ｍａｒｋｏｖ更新过程的方法和概率论，得到了该控制系统的一些可靠性指标，比如可靠度Ｒ（ｔ），系统瞬时可用度Ａ（ｔ）和稳态可用度Ａ，系统首次故障的平均时间ＭＴＦＦ等．同时也求得了该系统的一些重要的可行性指标，如系统的瞬时性能可用度Ａｃ（ｔ）和稳态性能可用度Ａｃ，系统首次故障前的平均性能ＭＣＦＦ等     

Liposomes from novel photolabile phospholipids: light-induced unloading of small molecules as monitored by PFG NMR

A molecular dithiane-based approach to synthesis of novel photolabile phospholipids is developed. These lipids are used in formulations with egg-POPC and cholesterol to prepare light-sensitive liposomes. Irradiation of such liposomes in PBS buffer (medium pressure mercury lamp, Pyrex filter, lambda > 300 nm) significantly increases the bilayer permeability and accelerates the release of entrapped small organic molecules by an order of magnitude. A simple assay, based on (1)H or (19)F PFG NMR measurements of diffusion coefficients, is developed to monitor light-induced unloading of the probe molecules.     

NONOSCILLATION FOR SECOND ORDER IMPULSIVE DIFFERENTIAL EQUATION

We prove nonoscillation results for a class of second order equation.The results generalize ones of Huang.     

Field emission and photoluminescence characteristics of ZnS nanowires via vapor phase growth

Large-area ZnS nanowires were synthesized through a vapor phase deposition method. X-ray diffraction and electron microscopy results show that the products are composed of single crystalline ZnS nanowires with a cubic structure. The nanowires have sharp tips and are distributed uniformly on silicon substrates. The diameter of the bases is in the range of 320-530 nm and that of the tips is around 20-30 nm. The strong ultraviolet emission in the photoluminescence spectra also demonstrates that the ZnS nanowires are of high crystalline perfection. Field emission measurements reveal that the ZnS nanowires have a fairly low threshold field, which may be ascribed to their very sharp tips, rough surfaces and high crystal quality. The perfect field emission ability of the ZnS nanowires makes them a promising candidate for the fabrication of flexible cold cathodes.     

飞秒脉冲泵浦光子晶体光纤产生1.3μm区域的光谱展宽

采用OPA产生的中心波长为1.2759 μm、平均输出功率为30 mW、重复频率为250 kHz、脉冲宽度为250 fs的光脉冲作为泵浦源,研究了PCF输出光谱随泵浦焦点与光纤端面的相对移动的光谱演变.在纤芯直径为2.0 μm、长度为1.8 m的光子晶体光纤中获得了近700 nm的光谱展宽,展宽的光谱从1.09 μm到1.79 μm,分析认为是高阶孤子的分裂和四波混频导致的光谱展宽,而在1.4 μm左右的光谱凹陷是由于光纤中OH离子的吸收造成的.PCF输出的光谱可应用在WDM通信和光互连网的超短脉冲多通道光源中.