Behavior of Tetraalkylammonium Bromide in Phase Transfer Catalytic Reaction at a Liquid/Liquid Interface as Studied by a Quasi-Elastic Laser Scattering Method

The liquid/liquid interface plays important roles in various processes such as phase transfer catalyst,solvent extraction and ion-selective electrode.     

Roles of gamma-Globulin in the Dynamic Interfacial Behavior of Mixed Dipalmitoyl Phosphatidylcholine/gamma-Globulin Monolayers at Air/Liquid Interfaces

This study investigated the roles of gamma-globulin in the dynamic interfacial behavior of dipalmitoyl phosphatidylcholine (DPPC)/gamma-globulin monolayers at air/liquid interfaces at 25 degrees C. The surface tension behavior demonstrated that gamma-globulin had a large adsorption time scale. Moreover, the surface pressure-area hysteresis behavior of adsorbed gamma-globulin monolayers suggested that no significant desorption occurred during the compression stage, and the respreading of gamma-globulin molecules at the interface during the expansion stage was slow. From the hysteresis behavior of adsorbed gamma-globulin monolayers with spread DPPC molecules, it was found that gamma-globulin molecules were expelled from the interface as DPPC molecules were in a condensed state. The squeeze-out of gamma-globulin molecules seemed to induce the loss of DPPC molecules at the interface with the extent depending on the initial gamma-globulin surface concentration. Furthermore, the expelled gamma-globulin molecules re-entered the monolayer and participated in the surface pressure increase during the following expansion stage. The exclusion of gamma-globulin associated with the removal of DPPC during monolayer compression and the re-entry of gamma-globulin during subsequent monolayer expansion represented a mechanism for DPPC depletion and gamma-globulin enrichment at the interface, which may explain the inhibitory effect of certain proteins on the surface activity of DPPC. Copyright 2000 Academic Press.     

Dynamic Surface Tension Behavior of a Mixed Insoluble/Soluble Surfactant Dispersion at Pulsating Air/Liquid Interfaces: Roles of the Soluble Surfactant

The influence of tyloxapol on the dynamic surface tension response of dipalmitoyl phosphatidylcholine (DPPC) dispersions at pulsating air/liquid interfaces was investigated. For a 1000 ppm DPPC dispersion prepared by sonication with a larger particle size, the dynamic surface activity of DPPC was strongly affected by the addition of 100 ppm tyloxapol. With a longer sonication time or smaller particle size, the DPPC inactivation was still observed but was somewhat less significant, resulting in slightly lower dynamic surface tensions. If a DPPC dispersion was sonicated in the presence of tyloxapol, the particle size of DPPC was greatly reduced by tyloxapol and the inhibitory effect of tyloxapol on the dynamic adsorption of DPPC may be significantly diminished. The results suggest that the competitive adsorption of tyloxapol may have a detrimental effect on the dynamic surface tension lowering ability of a DPPC dispersion with the extent depending on the DPPC dispersion state. Nevertheless, the dynamic surface activity of DPPC may be enhanced through the improved dispersion by tyloxapol if an appropriate preparation protocol is applied, and the inhibitory effect of tyloxapol may be reduced or overcome. Copyright 2001 Academic Press.     

液/液界面电化学及其进展

液/液界面电化学及电分析化学与研究萃取和化学传感机理、相转移催化、药物释放、模拟生物膜等密切相关,近年来备受到关注. 文中结合作者课题组工作,介绍、综述该领域近十几年、尤其在液/液界面微观结构、电荷（离子与电子）转移反应及界面功能化的新进展.     

利用金属有机框架铆钉分子催化剂在气液固界面上催化二氧化碳氢化

正二氧化碳(CO_2)氢化制甲酸具有重要的意义,将二氧化碳转变成基础化工原料和重要储能媒介。由于CO_2直接氢化为甲酸受热力学限制,往往需要在液相碱性环境中将氢化反应与酸碱中和反应偶联,使平衡右移。另外,反应体系往往需要比较高的氢气分压,以提高氢气在溶剂中的溶解度。近期,厦门大学固体表面物理化学国家重点实验室汪骋课题组和程俊课题组在常压催化CO_2     

Monolayer and Bilayer Formation of Molecular 2D Networks Assembled at the Liquid/Solid Interfaces by Solution-Based Drop-Cast Method

In recent years, extending self-assembled structures from two-dimensions (2D) to three-dimensions (3D) has been a paradigm in surface supramolecular chemistry and contemporary nanotechnology. Using organic molecules of p-terphenyl-3,5,3′,5′-tetracarboxylic acid (TPTC), and scanning tunneling microscopy (STM), we present a simple route, that is the control of the solute solubility in a sample solution, to achieve the vertical growth of supramolecular self-assemblies, which would otherwise form monolayers at the organic solvent/graphite interface. Presumably, the bilayer formations were based on π-conjugated overlapped molecular dimers that worked as nuclei to induce the yielding of the second layer. We also tested other molecules, including trimesic acid (TMA) and 1,3,5-tris(4-carboxyphenyl)-benzene (BTB), as well as the further application of our methodology, demonstrating the facile preparation of layered assemblies.     

Gibbs吸附公式在固-气和固-液界面吸附中的应用

Gibbs吸附公式本适用于各种界面的吸附研究 ,但由于有固体参与形成的界面界面能测定困难 ,至今Gibbs公式多只用于气 液界面的研究。本文讨论了Gibbs吸附公式在固 气和固 液界面吸附研究中的应用 ,主要是介绍将Gibbs公式与二维气体状态方程结合导出吸附等温式 ,因吸附而引起的固 气和固 液界面能变化规律 ,以及吸附过程中分子状态变化的有关信息     

不饱和聚酯/有机蒙脱土复合材料的固化动力学

用动态扭振法研究不饱和聚酯／有机蒙脱土复合材料的固化动力学行为。结果表明该实验体系能够很好地应用Flory理论和Avami方程进行拟合。用非平衡态热力学涨落理论对纳米复合材料的固化作了理论顸估,顸估结果与实验固化曲线有很好的相符性。有机蒙脱土的加入降低了不饱和聚酯的固化反应速率,对固化反应表现活化能和复合材料的形成过程没有很大的影响。根据实验结果分析不饱和聚酯在有机蒙脱土存在下的固化分为定型和熟化两个阶段,在一定的固化温度和填充含量下。从动态扭振曲线上可以明显地观察到这种“二次固化”现象。     

Determination of a Nonionic Surfactant by Electrolysis at a Liquid/Liquid Interface

The market and application for nonionic surfactants continues to increase steadily in recent years. Many analytical methods for those substance have been introduced. In this paper a new electrochemical method based on electrolysis at a liquid/liquid interface has been proposed for determination of a nonionic surfactant,emulsifier OP(EOP).     

Photoelectrochemical CO2 Reduction with a Rhenium Organometallic Redox Mediator at Semiconductor/Aqueous Liquid Junction Interfaces

Electrochemical and photoelectrochemical CO₂ reductions were carried out with Re(bh‐bipy)(CO)₃(OH₂) cocatalysts in aqueous electrolytes. Competition between hydrogen evolution and CO₂ reduction was observed under (photo)electrochemical conditions for both glassy carbon and CuInS₂ electrodes. The partial current density for CO generation is limited even though the additional potential is applied. However, electrochemical hydrogen evolution was suppressed under photoelectrochemical conditions, and the selectivity and partial current density for CO were considerably increased when compared to the electrochemical reduction in an identical electrode/electrolyte system. This finding may provide insights into using semiconductor/liquid junctions for solar fuel devices to overcome the limitations of electrolysis systems with an external bias.     

等度反相高效液相色谱法测定熊胆中磷脂类化合物

 摘要：建立了一种分离、测定磷脂酰胆碱（PC）、磷脂酸（PA）、心磷脂（CL）和磷脂酰甘油（PG）的等度RP-HPLC法。色谱条件为：在P-EC18柱上,用V（甲醇）：V（乙腈）：V（水）＝79:8:13的溶液作流动相,以2.0mL/min的流速进行等度洗脱,紫外检测波长205nm,谱带宽5nm。以熊胆为样品,经预处理后用所建立的方法进行分析,结果表明：6个熊胆样品中PC的质量比差别较大;PA的质量比除2号样品较低外,其余相近;PG除2号样品外都能检出,其中6号样品中PG的质量比稍大。PC的平均回收率为89     

大豆磷脂的高效液相色谱分析

采用正相高效液相色谱法,梯度洗脱程序和蒸发光散射检测器对大豆磷脂组成进行分析,在15min内将大豆膦脂中4种重要组分：卵磷脂,脑磷脂,肌醇磷脂和磷脂酸与其它组分完全分离,用外标法对这4种重要成分进行定量,线性范围为0．2－5．8g/L,回收率为96．7－100．8％;相对标准偏差为0．82％－1．34％,方法用于实际样品测定,获得满意的结果。     

Potential Screening at Electrode/Ionic Liquid Interfaces from In Situ X-ray Photoelectron Spectroscopy

A new approach to investigate potential screening at the interface of ionic liquids (ILs) and charged electrodes in a two-electrode electrochemical cell by in situ X-ray photoelectron spectroscopy has been introduced. Using identical electrodes, we deduce the potential screening at the working and the counter electrodes as a function of applied voltage from the potential change of the bulk IL, as derived from corresponding core level binding energy shifts for different IL/electrode combinations. For imidazolium-based ILs and Pt electrodes, we find a significantly larger potential screening at the anode than at the cathode, which we attribute to strong attractive interactions between the imidazolium cation and Pt. In the absence of specific ion/electrode interactions, asymmetric potential screening only occurs for ILs with different cation and anion sizes as demonstrated for an imidazolium chloride IL and Au electrodes, which we assign to the different thicknesses of the electrical double layers. Our results imply that potential screening in ILs is mainly established by a single layer of counterions at the electrode.     

Dynamic Interfacial Tension of Surfactant Mixtures at Liquid-Liquid Interfaces

Dynamic interfacial tensions for surfactant mixtures at liquid-liquid interfaces were obtained with a drop volume tensiometer. The surfactants tested were Triton X-100, palmitic acid, and Span 80 at both the water-hexadecane and water-mineral oil interfaces. Two-surfactant mixtures were examined with the surfactants initially dissolved in different phases to minimize bulk-phase interactions. For concentrations below the CMC, it was found that the adsorption kinetics of palmitic acid and Triton X-100 mixtures were dominated by the latter surfactant. Apparent diffusion coefficients were obtained for Triton X-100 both in the absence and in the presence of palmitic acid. These values were largely insensitive to the presence of palmitic acid. For mixtures of Span 80 and Triton X-100, the adsorption kinetics were found to be influenced significantly by both surfactants. In this case, relative changes in surfactant concentrations affected the dynamic interfacial tension of the mixed system. A previously proposed multicomponent adsorption model described the dynamic interfacial tension adequately at low concentrations of Triton X-100, when desorption could be neglected. At higher concentrations, modifications were needed to account for solubilization into the oil phase. These corrections allowed the model to describe the long time adsorption quite well. However, predicted values of short time interfacial tensions were overestimated, likely due to a synergistic interaction of the two surfactants. Copyright 1999 Academic Press.     

环氧树脂/PAMAM体系的固化动力学研究

用动态扭振法研究以聚酰胺-胺(PAMAM)为固化剂的环氧树脂／PAMAM体系的固化动力学行为。结果表明,该实验体系能够很好地用Flory理论和Avami方程进行拟合。     

Influence of Surfactants Synergism on the Adsorption Behavior at Air/Water and Solid/Water Interfaces

The influence of synergistic interaction between sodium dodecylsulfate (SDS) and N,N-dimethyldodecan-1-amine oxide (DDAO) on their adsorption at air/water and solid/water interfaces at 20°C is investigated. The critical micelle concentration values obtained from surface tension measurements indicated strong synergism between SDS and DDAO, according to regular solution model. The excess surface concentration (Γ) and the minimum occupied area by single and mixed surfactant monomers (A_min) at liquid/air interface were also calculated. The adsorption onto the activated charcoal and silica was then measured to find out the correlation between surfactant synergism and their adsorption at solid/water interface. The amounts of surfactant adsorbed onto 1 wt% activated charcoal follow the trend: SDS/DDAO > DDAO > SDS. SDS molecules do not adsorb onto 5 wt% silica substrate, while SDS/DDAO mixed system was found to have the highest adsorption behavior. The obtained indicate that SDS can be removed from water by mixing it with amphoteric surfactant.     

Determination of Minocycline by Semi-Differential Cyclic Voltammetry at a Liquid/Liquid Interface

Abstract

The voltammetric behaviour of minocycline at a water/nitrobenzene interface has been studied by normal, semi-differential and semi-integral cyclic voltammetry. The semi-differential cyclic voltammetry can be used as a rapid, simple method for determination of the antibiotic minocycline in the range of 5–200 ug/ml and the relative standard deviation is within 3%. Drug samples were analyzed and satisfactory results were found as compared with US Pharmacopoeia method.