用自组装法制备聚合物纳米复合膜

文章比较了自组装法（ｓｅｌｆ－ａｓｓｅｍｂｌｙ,ＳＡ）与Ｌａｎｇｍｕｉｒ－Ｂｌｏｄｇｅｔｔ技术（ＬＢ）及其它方法在制备聚合物纳米复合膜时的优劣。ＳＡ法由于操作简单、膜的结构稳定性较高,因此较ＬＢ技术等具有更大的实用价值。利用ＳＡ法,可以制备各种有机聚电解质与其带相反电荷的有机聚电解质、粘土化合物及无机纳米颗粒等组成的聚合纳米复合膜。     

Nanofluidic Ion Transport and Energy Conversion through Ultrathin Free‐Standing Polymeric Carbon Nitride Membranes

Ions transport through confined space with characteristic dimensions comparable to the Debye length has many applications, for example, in water desalination, dialysis, and energy conversion. However, existing 2D/3D smart porous membranes for ions transport and further applications are fragile, thermolabile, and/or difficult to scale up, limiting their practical applicability. Now, polymeric carbon nitride alternatively allows the creation of an ultrathin free‐standing carbon nitride membrane (UFSCNM), which can be fabricated by simple CVD polymerization and exhibits excellent nanofluidic ion‐transport properties. The surface‐charge‐governed ion transport also endows such UFSCNMs with the function of converting salinity gradients into electric energy. With advantages of low cost, facile fabrication, and the ease of scale up while supporting high ionic currents, UFSCNM can be considered as an alternative for energy conversion systems and new ionic devices.     

Enzymatically Active Ultrathin Pepsin Membranes

Enzymatically active proteins enable efficient and specific cleavage reactions of peptide bonds. Covalent coupling of the enzymes permits immobilization, which in turn reduces autolysis‐induced deactivation. Ultrathin pepsin membranes were prepared by facile interfacial polycondensation of pepsin and trimesoyl chloride. The pepsin membrane allows for simultaneous enzymatic conversion and selective removal of digestion products. The large water fluxes through the membrane expedite the transport of large molecules through the pepsin layers. The presented method enables the large‐scale production of ultrathin, cross‐linked, enzymatically active membranes.     

Production of Enzymes by Plant Cells Immobilized by Sol-Gel Silica

Ajuga reptans cells are cultivated and used for production of invertase. These plant cells are immobilized by a sol-gel SiO₂ membrane, which is built up directly on the cell surface by exposure to a gaseous flow of silicon alcoxide precursors. The immobilization modifies the metabolic activity of cells, resulting in a 40-fold increase in invertase production with respect of free cells. Results concerning total release of proteins, cell growth and produced invertase activity are discussed, considering the absence of breeding, induced by SiO₂ immobilization, the prominent factor promoting the observed exceptional increase in invertase productivity.     

导电聚合物超薄膜的制备及性能表征

采用修饰LB膜法制备了导电聚合物聚-3,4-乙烯二氧噻吩/硬脂酸(PEDOT/SA)复合超薄膜. 将硬脂酸(SA)/FeCl3 LB膜暴露于EDOT单体气氛中, EDOT 单体在多层膜中聚合, 制备了PEDOT/SA多层复合LB膜. 紫外-可见光-近红外(UV-Vis-NIR)吸收光谱和X射线光电子能谱(XPS)分析表明EDOT单体在多层膜中发生聚合并生成PEDOT导电聚合物. 扫描电子显微镜(SEM)分析显示生成的PEDOT导电聚合物颗粒分散于硬脂酸LB膜中, 被LB 膜所包裹. 二次离子质谱(SIMS)及XPS分析还发现S元素含量随LB 膜的深度变化而变化, 表明PEDOT 较好地分散于多层膜中. 采用四探针电导率仪对复合多层膜的电导率进行了测试, 结果显示60 层复合LB 膜的电导率为2.6 S·cm-1, 比普通PEDOT薄膜的电导率高一个数量级, 且表现出较好的掺杂/脱掺杂能力. 研究还发现复合膜电导率与薄膜在EDOT 单体中处理时间有关, 处理时间至120 min 后电导率达到最大值并趋于稳定, 氧化剂浓度较低可能影响EDOT在LB膜中的聚合反应速率. 对复合LB 膜的气敏特性进行了分析, 发现在较低气体浓度范围(φ<30×10^-6), PEDOT 复合LB 膜有较快的反应速率, 气敏性与气体浓度呈非线性. 在较高浓度范围(φ=(30-120)×10^-6), 气敏性与浓度呈较好的线性关系. PEDOT复合LB膜对HCl气体表现出较好的响应恢复特性. 同时对PEDOT 复合膜相关的导电机理及气体敏感机理进行了分析.     

氧化铁磁性纳米粒子固定化酶*

纳米粒子作为酶固定化的载体,当其具有磁性时,制备的固定化酶易于从反应体系中分离和回收,操作简便;并且利用外部磁场可以控制磁性材料固定化酶的运动方式和方向,替代传统的机械搅拌方式,提高固定化酶的催化效率。在众多纳米材料中,氧化铁因其在磁性、催化等多方面的良好特性而倍受瞩目。本文对近年来各种氧化铁磁性纳米粒子固定化酶,尤其是固定化脂肪酶和蛋白酶的制备方法及其应用做了较为详细的阐述,对这些氧化铁磁性纳米粒子固定化酶的优缺点和发展前景进行了讨论。     

固定化酶法测定血清中葡萄糖和胆固醇

本文讨论了一种灵敏、高选择性的方法分别测定葡萄糖和胆固醇,并介绍了成二醛固定化酶(葡萄糖氧化酶或胆固醇氧化酶)后产生的过氧化氢借助于鲁米诺-铁氰化钾发光反应由流动注射法测定。对血清中样品的前处理和反应试剂浓度的影响也分别作了研究。本法有良好的线性工作范围,连续进样100次仍能保持工作的稳定性,相对标准误差为3.8～5.2%。     

固定化酶的制备及应用

酶的固定化及其酶促反应是最具发展前景的生物技术前沿领域之一。固定化酶已经广泛应用于生物化学、生物技术与工程、生物医学工程、化学化工等方面,将在人类社会可持续发展中发挥重要作用。本文综述了近期固定化酶制备及应用研究的进展。     

New Immobilized Enzyme Membranes for Tailor-Made Biosensors

Abstract

Commercially available polyamide preactivated membranes for immunodiagnostic use were found suitable for the preparation of immobilized enzyme membranes adaptable to biosensors. Membranes with immobilized glucose oxidese as model enzyme, tested with a microprocessor-based device involving an enzymatic electrode, gave excellent results. The extremely simple and fast procedure allows anyone to prepare such bioactive membranes easily, possibly from his own enzyme preparation and within a few minutes set up a specific probe from commercially available sensors.     

抗污染高分子分离膜研究进展

高分子分离膜已广泛应用于水处理、食品、生物医药等领域。然而,常用的膜材料如聚醚砜(PES)、聚砜(PSf)、聚偏氟乙烯(PVDF)等容易吸附蛋白质和微生物形成膜污染,进而影响膜的性能和使用寿命。膜污染尤其是膜的生物污染成为限制膜广泛应用的主要瓶颈之一。本文从亲水改性、抗菌改性及亲水抗菌双功能改性三方面综述了控制膜污染的研究进展和现状,并对其未来发展方向进行了展望。     

Thermoanalytical Studies of Polymeric Membranes for Immunoisolation

Preliminary studies concerning characterization of the structure of polymeric membranes for immunoisolation are reported. Laboratory-made cellulosic and polyurethane membranes for immunoisolation were investigated. Differential scanning calorimetry (DSC) was applied to determine the membrane structure, e.g. the pore diameter. The thermoanalytical measurements were carried out with a Perkin Elmer DSC 7 equipped with a CCA 7 cooling accessory. Diffusive transport across the hollow fiber membrane was evaluated in vitro by using albumin, creatinine and vitamin B₁₂. It was concluded that the DSC method is a useful tool for characterization of polymeric membranes for immunoisolation. Methodology, including experimental conditions, is proposed for capillary membranes. This revised version was published online in August 2006 with corrections to the Cover Date.     

Factors Influencing Photochromism of Spiro-Compounds Within Polymeric Matrices

Abstract

Photochromic polymeric materials have been commercialized in ophthalmic lenses, however, there are many other potential uses for this technology. The photochromic transitions are extremely sensitive to environmental conditions, thus offering the potential for modifying the kinetics to suit different applications. There are a significant number of photochromic molecular families, with different characteristics. The spiro-compounds, both spirooxazines and spiropyrans, have received the most attention as they have good coloration properties and spirooxazines also display good fatigue resistance. Consequently this review focuses on the inclusion of these compounds into polymer matrices. In addition we discuss decoloration and coloration behaviors, solvatochromism, mechanism of fatigue, and unusual synthetic approaches.     

Chemfet Based Microsensors Covered with Ion-Partitioning Polymeric Membranes

 The development of a new type of microsensors based on chemically sensitive field-effect transistors (CHEMFETs) covered with polymeric bulk ion-partitioning membranes is presented. For the construction of the microsensor, a PVC plasticized membrane containing two ionophores, one selective to protons and the other to the analyte cation of interest, is placed on the gate of a pH sensitive field-effect transistor which acts as the transducer. With the use of thin (5–10 μm) ion-partitioning membranes onto the pH-sensitive ISFET gate, the proton displacement out of the membrane and to the pH sensitive gate is fast and reversible. This displacement generates a signal that is directly related to the analyte concentration found in the test solution. Comparing the performance of CHEMFETs and ISEs selective to the monovalent potassium cation and the divalent calcium ion validates this novel CHEMFET response mechanism.     

Preparation and Characterization of Pepsin Immobilized on Polymeric Supports

Abstract

Immobilization of pepsin on crosslinked resinous materials SRF (salicylic acid-resorcinol-formaldehyde), Amberlite IRA-400, and poly-(vinyl alcohol) is reported. Enzyme concentration, pH of the coupling medium, and nature and concentration of crosslinking agents were optimized for the better retention of activity of immobilized pepsin. The immobilized systems were characterized through pH, thermal, and storage stabilities. Michaelis constant (K _m) and maximum reaction velocity (V _m) for the free and immobilized enzymes were calculated from Lineweaver-Burk plots. Effect of temperature on enzyme activity was studied, and the thermoinactivation constant (K _ti) and energy of activation (E _a) for free and immobilized enzymes were also calculated. The immobilized pepsin was used in a continuous fluidized bed reactor for the study of clotting of skimmed milk. Rate of coagulation was considerably high for the treated milk sample at 50°C and pH 6–6.2.     

Electrochemical Interfacial Polymerization toward Ultrathin COF Membranes for Brine Desalination

Ultrathin covalent organic framework (COF) membranes are urgently demanded in molecular/ionic separations. Herein, we reported an electrochemical interfacial polymerization strategy to fabricate ultrathin COF membranes with thickness of 85 nm, by actively manipulate self-healing effect and self-inhibiting effect. The resulting COF membrane exhibited superior performance in brine desalination with the permeation flux of 92 kg m⁻² h⁻¹ and the rejection of 99.96 %. Our electrochemical interfacial polymerization strategy enriches the fabrication approach of COF membranes and facilitates the rational design of ultrathin membranes.     

Sonochemical Synthesis of Spherical Silica Nanoparticles and Polymeric Nanocomposites

In this work spherical SiO₂ nanoparticles were synthesized by sonochemical method using a new Schiff-base as a capping agent. The silica nanoparticles were obtained by hydrolysis of tetraethyl orthosilicate in aqueous alcohol solution. The effect of different parameters such as molar concentration of Schiff-base ligands and ultrasonic irradiation on the morphology and size of the products was examined. The results demonstrated that applying the appropriate amount of Schiff-base could be effective in control of particle size. The influence of SiO₂ nanostructures on the flame retardancy of the poly styrene, poly vinyl alcohol, cellulose acetate and ethyl cellulose was studied. In-situ and ex situ nanocomposites were investigated and results confirm that flame retardancy of in situ nanocomposites were better than ex situ samples. HO···Si–O–Si···OH barrier prevents reaching of flame, heat and oxygen to the polymeric nanocomposites.     

Molecular and Morphological Designs of High Performance Polymeric Membranes

Currently, membrane separation techniques, such as reverse osmosis and ultrafiltration, play an important role in industrial separation technology. To develop high performance polymeric membranes, it is essential to design the molecular and morphological structures of the membranes for their specific applications. In the reverse osmosis field, we have developed several kinds of composite membranes for specific uses. Applications include ultrapure water production, seawater desalination, softening and desalination of brackish water, and recovery of valuable substances. In the course of development, thin-film composite membrane materials and membrane morphology have been analyzed intensively and are becoming clearer. These results enable us to control membrane performance by an optimum combination of membrane materials and membrane morphology. The morphological structure and chemical structure of the composite membranes were designed to optimize the performance of both the ultrathin layer and the supporting substrate layer for each membrane's application. As ultrafiltration is expanding to various fields, requirements for membrane performance have become more severe, especially for 1) sharpness of molecular weight cutoff, 2) solvent and high temperature resistance, and 3) fouling resistance (low nonspecific protein adsorption). To satisfy these requirements, we have developed a new ultrafiltration membrane. Owing to the high resistivity and hydrophilicity of its chemical structure, the membrane shows excellent solvent and high temperature resistance as well as fouling resistance. In addition, sharp molecular cutoff was realized by controlling membrane morphology.     

基于固定化酶的化学发光停流法测定D-氨基酸

基于固定化酶的化学发光停流法测定Ｄ－氨基酸封满良,黄玉文,宫志龙,章竹君（陕西师范大学化学系,西安,７１００６２）关键词固定化酶,化学发光,甲壳质,Ｄ－氨基酸自从发现人体有关组织及血桨中Ｄ－氨基酸的水平与某些疾病有关以来,已报道了许多测定Ｄ－氨基酸的...