疏水性聚丙烯酸/聚乙烯醇/葡萄糖淀粉酶复合纳米纤维膜的制备及酶学性质

利用混合静电纺丝将葡萄糖淀粉酶(GA)固定于聚丙烯酸(PAA)/聚乙烯醇(PVA)纳米纤维膜上,并通过鉴定固定化GA的酶学特征检验PAA/PVA可否成为一种优良的酶固定化载体。 对其理化性质和酶学特征进行鉴定,经红外光谱(FT-IR)和扫描电子显微镜(SEM)表征发现,GA可成功包埋于PAA/PVA纳米纤维膜内部;对包裹固定的GA进行酶学性质鉴定,发现固定化GA的最适反应温度为68 ℃,比游离GA提高了9 ℃;固定化GA的适用pH值范围明显变宽;热稳定性和存贮稳定性显著增强且可以重复使用。PAA/PVA纳米纤维膜是一种优良的酶固定化载体,可以通过混合静电纺丝包埋法简便地将蛋白质分子固定于其内部,具有一定的应用前景。     

聚合物的静电纺丝

静电纺丝法是聚合物溶液或熔体在静电作用下进行喷射拉伸而获得纳米级纤维的纺丝方法.由纳米纤维制得的无纺布,具有孔隙率高、比表面积大、纤维精细程度与均一性高、长径比大等优点,从而赋予了静电纺丝纤维广泛的应用前景,它已在国内外引起了广泛的关注.本文介绍了静电纺丝的装置、基本原理及静电纺丝制备纳米纤维的研究进展,同时也叙述了其在各个领域的应用,最后展望了静电纺丝制备纳米纤维的发展方向及前景.     

聚丙烯腈电纺纤维的功能化

聚丙烯腈是一种性能优异、应用广泛的成纤聚合物,静电纺丝技术则可用于制备聚丙烯腈纳米纤维,本文对聚丙烯腈纳米纤维的功能化进行了综述.通过表面仿生修饰、碳纳米管填充等方法改性的聚丙烯腈电纺纤维被尝试作为酶固定化的载体材料,在显著提高载酶量的同时,能大幅度提高酶活性.糖基功能化的纳米纤维对特定的蛋白质具有较高的识别效率,可望用于蛋白质的分离与纯化.卟啉化的聚丙烯腈电纺纤维则在显示出荧光特性的同时,在催化、传感等方面具有潜在的应用前景.     

静电纺丝法制备新型吸附分离材料

随着现代经济、工业的发展,许多环境问题出现在了人类面前,对于新型吸附分离材料的需求也变得十分迫切。静电纺丝法是一种简单有效制备连续纳米长丝的技术,有着十分广阔的应用前景。由于静电纺丝法制备的纤维膜具有较大的比表面积、易于调控的微观结构及化学性质,静电纺丝法能够用于制备新型的吸附分离材料。本文对电纺纤维膜的制备与改性,以及电纺纤维膜在空气过滤、油水分离、重金属离子去除等领域的应用进行了介绍,同时对其未来的发展进行了展望。     

静电纺丝技术在锂离子动力电池中的应用

锂离子动力电池,作为动力源,要求其具有较高的比容量、倍率性能、热稳定性及优异的循环性能。静电纺丝技术是一种新型纳米纤维制备技术,因其制备的纳米纤维膜具有比表面积大和孔隙率高等特点,近年来在锂离子电池领域得到了广泛应用,有望成为大幅改善锂离子动力电池性能的关键技术。基于锂离子动力电池的特性,当前静电纺丝技术主要用于制备高孔隙率的纳米纤维膜、高分子共混膜及无机-高分子复合膜等隔膜材料以提高隔膜的机械性能和热稳定性;此外,静电纺丝技术还被用于改善磷酸铁锂等聚阴离子型正极材料及石墨负极材料的电化学性能。本文还针对上述研究中存在的问题,提出了未来静电纺丝技术在锂离子动力电池中应用的可改进的研究方案。     

电纺含银纳米粒子复合纤维的制备及应用

银纳米粒子由于其特殊的物理化学性质而被广泛应用,但其易团聚,影响实际使用效果。银纳米粒子可被负载到稳定载体上,获得具有优异性能的纳米复合材料,克服了团聚等缺限,大大改善应用效果和效率。采用静电纺丝技术制备银修饰纳米复合纤维材料是其中一种有效的方法,近年来在复合材料制备领域受到了广泛关注。本文综述了最近几年关于静电纺丝制备负载银纳米颗粒纤维复合材料及其应用的研究进展,重点介绍了静电纺丝制备负载银纳米纤维过程中纳米银的生成和负载方法,总结了有机主体和无机主体两种纺丝纤维的制备研究进展,详细介绍了负载银纺丝纤维在几个重要领域的应用及研究方向。     

同轴静电纺丝技术制备药物缓释载体的研究进展

由于纳米纤维在组织工程支架材料,药物传递载体等方面的潜在应用,使得具有高比表面积的静电纺丝纳米纤维得到了很大的关注。静电纺丝技术是一种简单、有效的微／纳米技术,而同轴静电纺丝则是在传统静电纺丝技术上发展起来的新方法,单步即可制备连续的壳一芯结构纳米纤维或中空纳米纤维。这也使得静电纺丝纳米纤维在组织工程和药物缓释等领域有...     

静电纺丝技术在二次电池和电催化领域的应用进展

静电纺丝技术是一种简单、高效制备一维纳米纤维的方法,其制备的纳米纤维一般经过后期热处理得到含碳复合物,具有操作简单、方法可控、产量可观等优点,得到的材料具有良好的导电性和快速的电子、离子传输路径,因此可用来广泛制备电极及催化材料.基于此,静电纺丝技术在二次电池(如锂/钠离子电池)和电催化领域有着广泛的应用.本综述不仅介绍了静电纺丝技术的原理,并且总结了其在纳米电极材料及催化领域的优势和标志性成果,并针对相关领域的问题进行了合理的探讨.此外,本文简要总结了现有的发展进程并指出了未来的发展方向,可对静电纺丝技术在先进能源材料的设计与制备上提供指导.     

静电纺丝纳米纤维薄膜的应用进展

静电纺丝是一种简单而高效制备高分子微纳米纤维的技术,由于设备和实验成本低、纤维产率高、制备出的纤维比表面积比较大、适用性广泛等独特的优势,近些年来备受关注。静电纺丝的应用是静电纺丝研究的最基本动力和终极目标,因此成为研究者一直努力的方向。为了研究静电纺丝应用的研究现状和主要发展方向,本文综述了静电纺丝纳米纤维薄膜几个主要的应用领域,包括组织工程、药物缓释、纳米传感器、能源应用、生物芯片和催化剂负载等,并展望了未来可能的发展方向。     

基于静电纺丝技术的多级结构聚合物纳米纤维复合材料的研究进展

静电纺丝技术是目前制备纳米纤维最重要的方法之一,以其制备的纤维具有直径可控、比表面积大、孔隙率高等优点,因而被广泛应用于过滤、催化、传感器及生物医学等众多领域.以静电纺丝纤维为模板可进一步构建多级结构的功能性聚合物纳米纤维复合材料,拓宽其应用范围.本文着重概述了近年来基于静电纺丝技术的简单共混型、核壳结构及多级结构的聚合物纳米纤维复合材料的制备、结构及性能,并展望了其应用研究前景.     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).