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膜/液界面浓度极化现象的介电解析 总被引:1,自引:0,他引:1
对由强、弱荷电膜和溶液构成的膜/液非均匀体系,在10-107Hz频率范围进行了介电测量,在直流偏压下,该体系显示了二个显著的介电弛豫.利用具有电导率分布相,即浓度极化相的介电理论对强行电的离子交换膜的结果进行了介电解析,从实验上测得的介电参数求出了反映膜/液界面浓度极化层构造的参数,讨论了该体系产生介电弛像的原因、说明了介电理论的合理性,并提出了膜/液界面体系产生介电弛豫现象的可能机理. 相似文献
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壳聚糖膜对水杨酸吸附及释放过程的实时介电谱法研究 总被引:8,自引:0,他引:8
制备了壳聚糖膜,并且测量了壳聚糖膜/水杨酸溶液、含水杨酸的壳聚糖膜/蒸馏水两个膜/液体系的介电谱,在100~700kHz频率范围,发现两种体系都存在显著的介电弛豫现象,而且该弛豫的特征参数随壳聚糖膜在相应溶液相中浸泡时间的不同而变化.将该体系介电模型化、并利用在Maxwell-Wagner界面极化理论上建立的公式对介电谱进行解析,得到了体系中两相——壳聚糖膜相和溶液相的介电常数和电导率随时间的变化曲线.通过分析电导变化曲线得知,壳聚糖膜对溶液中的水杨酸有吸附现象,而含有水杨酸的壳聚糖膜在蒸馏水中可以缓慢释放出水杨酸;吸附过程包含的机制有氢键的形成、疏水力和扩散;而水杨酸的脱附过程则包含吸附过程几种机制的逆反应.理论分析和解析结果都验证了介电谱方法对吸附和释放过程实时监测的有效性. 相似文献
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自组装膜技术在电分析化学中的研究与应用 总被引:9,自引:0,他引:9
本文对自组膜(SAMs)在电分析化学中的研究和应用进行了比较全面的综述。SAMs是单分子膜化学修饰电极发展的最高形式,本文着重阐述了硫醇/金单分子层自组膜在微电极、生物电化学和生物传感器、液相色谱电化学、电催化、光谱电化学等电分析化学研究领域中的应用,并进行了展望。 相似文献
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冠醚修饰的固体支撑双层类脂膜的形成及性能研究 总被引:3,自引:1,他引:3
用饱和了胆固醇和饰用冠醚的角鲨烷/氯仿溶液作成膜液,制备了冠醚修饰的固体支撑双层类脂分子膜。重点考察了成膜物种及技术对膜稳定性及电特生影响。其膜电势随接触水相中的变化呈现Nernst响应,线性范围10^-4-10^-1mol/L。 相似文献
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电沉积二氧化钛纳米微粒膜的光电化学性能和表面形貌研究 总被引:19,自引:1,他引:19
采用光电流谱,透射光谱和扫描探针显微镜技术对电沉积法制备的二氧化钛纳米微粒膜的光电化学性能和表面形貌进行了研究,结果表明,不同制备条件下的二氧化钛纳米微粒膜具有与紧密的半导体电极不同的光电化学性质,并探讨了其光电化学性能与表面形貌关系。 相似文献
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聚酰亚胺LB膜研究进展 总被引:4,自引:0,他引:4
聚酰亚胺(PI)是一种高性能聚合物材料,通过Langmuir-Blodgett膜(LB膜)技术实现PI分子排列的有序化,可以使PI的某些性能更充分体出现来,详细总结了PILB膜的制备方法,对其在气体分离,光敏性,液晶取向,介电以及光电导等方面性质的研究现状进行了较为全面的综合,对PILB的研究和应用前景作了简要展望。 相似文献
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Uroš Grošelj Mojca Žorž Amalija Golobič Branko Stanovnik Jurij Svete 《Tetrahedron》2013,69(52):11092-11108
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. 相似文献
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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. 相似文献
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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%). 相似文献
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Shashikant U. Dighe Surya K. Samanta Shivalinga Kolle Sanjay Batra 《Tetrahedron》2017,73(17):2455-2467
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. 相似文献
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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. 相似文献
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An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions. 相似文献
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Synthesis of substituted pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles from the Morita-Baylis-Hillman derivatives of acrylates via saponification followed by Curtius reaction is described. 相似文献
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An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction. 相似文献
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Jona Mirnik Eva Pušavec Kirar Sebastijan Ričko Uroš Grošelj Amalija Golobič Franc Požgan Bogdan Štefane Jurij Svete 《Tetrahedron》2017,73(24):3329-3337
A series of 20 CuAIAC reactions between eight 4-acylamino substituted pyrazolidine-3-one-1-azomethine imines and four terminal ynones were performed using Cu0 as catalyst. The corresponding fluorescent cycloadducts were obtained in very high yields upon simple workup. Thus, Cu-metal turned out to be a better catalyst than CuI in terms of yield and ease of isolation. Availability of azomethine imines, mild reaction conditions, and simple workup enable a “click” access to libraries of densely substituted 2,3-dihydro-1H,5H-pyrazolo[1,2-a]pyrazol-1-ones. Reactivity of differently substituted dipoles was evaluated experimentally and by quantum chemical methods (DFT). 相似文献