静电纺丝法制备纤维素纳米纤维的研究进展

纤维素纳米纤维很好的结合了纤维素的重要属性和纳米材料的各项特性,但纤维素大分子之间存在大量氢键,使得纤维素较难溶于普通溶剂,导致通过静电纺丝法直接制备纤维素纳米纤维具有一定的难度.而先采用静电纺丝法制备纤维素衍生物纳米纤维,再对纤维素衍生物纳米纤维进行水解也是制备纤维素纳米纤维的一种有效方法.本文对近年来这两种纤维素纳米纤维制备方法的研究进行了综述,并对静电纺制备纤维素纳米纤维的发展前景做出了展望.     

静电纺丝制备醋酸纤维素复合纳米纤维的研究进展

静电纺丝技术就是通过带电聚合物溶液或熔体的喷射来制备纳米纤维,是一种制备纳米纤维材料简单有效的技术。醋酸纤维素(CA)易溶于有机溶剂,常作为纤维素的替代材料应用于静电纺丝领域。本文总结了近年来国内外采用静电纺丝技术制备CA复合纳米纤维的研究新进展,重点介绍了CA/CNTs复合纳米纤维、CA/金属粒子复合纳米纤维、CA/金属氧化物复合纳米纤维、CA基载药复合纳米纤维、CA/PAN复合纳米纤维、CA/PVA复合纳米纤维、CA/CS复合纳米纤维等CA复合纳米纤维的研究进展以及潜在的应用领域。     

静电纺丝法制备纳米抗菌纤维的研究进展

纳米抗菌材料是防止细菌等致病微生物对人们生产、生活的破坏而发展起来的一类新型材料.在纳米抗菌材料的众多制备方法中,静电纺丝是一种成本低,工艺可控的技术,制备的纳米纤维具有比表面积大、孔隙率高、纤维均匀等特点.本文作者首先简述了静电纺丝技术以及该技术制备纳米抗菌纤维材料的特点;接着按照菌剂种类不同,对静电纺丝技术制备的抗菌纤维材料进行归类,将其分为无机抗菌纤维材料、天然抗菌纤维材料和复合抗菌纤维材料3类,并对其研究进展进行了评述;最后对静电纺丝技术制备纳米抗菌纤维的研究现状进行了总结与展望.     

纤维素及其衍生物的高压静电纺丝

高压静电纺丝作为一种制备纳米纤维的先进技术,近年来受到普遍关注。而纤维素和纤维素衍生物由于其优越的性质已应用于各个领域。运用高压静电纺丝技术对纤维素及其衍生物进行研究,开拓了新的研究领域和发展方向。本文介绍了高压静电纺丝技术的研究背景和原理,总结了近几年研究者们在纤维素以及纤维素衍生物高压静电纺丝方面的工作进展,尤其对不同溶剂体系溶解纤维素用于静电纺丝的优缺点进行了比较,评述了这方面的前沿性探索研究,并对未来的发展进行了展望。     

静电纺丝纳米纤维膜固定化酶及其应用*

静电纺丝是一种简单有效的制备聚合物纳米纤维的技术,在组织工程、药物控释和传感器等方面具有广泛的应用。采用静电纺丝技术制备得到的纳米纤维膜具有比表面积大、孔隙率高和易于分离回收等优点,可以作为一种优良的酶固定化载体,目前在酶固定化领域受到了广泛的关注。本文综述了近年来静电纺丝纳米纤维膜固定化酶的研究进展,在阐述静电纺丝纳米纤维膜制备技术的基础上,详细介绍了纳米纤维膜表面担载法和包埋法固定化酶的原理和方法,分析了不同固定化方法的优缺点,并讨论了静电纺丝纳米纤维膜固定化酶的应用前景,对静电纺丝纳米纤维膜固定化酶的发展方向进行了展望。     

静电纺丝制备杯芳烃功能化纳米纤维的应用

静电纺丝技术是制备连续微纳米纤维的一种简单易行且高效的方法,所制备的纳米纤维因其独特的结构尺寸和广泛的应用领域而备受材料科学界的青睐。 作为第三代超分子主体化合物的杯芳烃及其衍生物因其独特的分子结构、优异的离子选择识别性和吸附性能而显示出广阔的应用前景。 本文简述了静电纺丝制备杯芳烃功能化纳米纤维的原理,系统地探讨了其作为吸附剂和催化剂载体的应用以及静电纺丝与杯芳烃相结合的优势。 讨论了目前静电纺丝制备杯芳烃功能化纳米纤维存在的问题,对未来的发展方向进行展望。     

静电纺丝法制备PHB基纳米纤维材料的研究进展

聚β-羟基丁酸酯(PHB)作为一种天然的可生物降解材料,因其良好的生物相容性,广泛应用于生物医用领域.而静电纺丝技术是获得纳米纤维最理想的方法之一,目前已成功制备出多种不同类型的纳米纤维,尤其在制备复合纳米纤维方面取得了显著成果.本文论述了国内外静电纺PHB基纳米纤维的研究现状和进展,重点介绍了静电纺PHB基纳米纤维影...     

静电纺丝制备二氧化钛复合纳米纤维的研究进展

纳米二氧化钛作为光催化剂与聚合物复合制成纳米纤维,在污水处理、光伏电池、传感器、锂离子电池等领域具有广泛的应用潜力。本文综述了近年来国内外静电纺丝制备二氧化钛纳米纤维的研究现状,重点介绍了不同类型二氧化钛纳米纤维的制备以及贵金属沉积、离子掺杂、半导体复合和表面光敏化等方法对二氧化钛纳米纤维的改性,展望了二氧化钛纳米纤维的发展前景。     

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...     

定形相变复合材料的研究进展——静电纺丝法

静电纺丝是制备定形相变复合材料的重要方法之一,本文综述了静电纺丝法制备定形相变复合材料的研究进展,主要包括溶液静电纺丝、溶液-溶液同轴静电纺丝、熔融-溶液同轴静电纺丝和静电纺纳米纤维膜物理吸附等,总结了静电纺丝常用的固-液相变材料(如脂肪族长链烷烃、大豆蜡、脂肪酸及其二元低共熔物、脂肪酸酯和聚乙二醇等)和支撑材料(如醋酸纤维素、聚对苯二甲酸乙二醇酯、聚乙烯吡咯烷酮、聚偏氟乙烯、聚乳酸、聚氨酯、聚酰胺6、聚丙烯腈及其碳纳米纤维等)。     

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.     

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.     

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.     

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%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

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.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.