结构化乳液的理论、制备与应用Ⅱ.结构化微乳液

对乳液的结构化研究近来的进展进行了综述,涉及到普通乳液、微乳液和纳米乳液的结构、制备、性能及应用.其中,对连续相结构化乳液的叙述包含了溶致型液晶作为乳液连续相、热致型液晶作为乳液连续相以及凝胶连续相乳液三个方面,而在对其应用方面的介绍中,提及了嵌段共聚物作为连续相的实例和制备单分散乳液的一些技术.本文对微乳液和纳米乳液的介绍则主要分为结构、特征、形成机理、制备方法、应用、聚合工艺及机理等方面.     

Loading efficiency and surface conductance of heparin-modified poly(lactide-co-glycolide) nanoparticles

Poly(lactide-co-glycolide) (PLGA) nanoparticles (NPs) with surface modification of heparin were fabricated by microemulsion–diffusion method. These novel colloidal particles were stabilized by lecithin and Tween 80. The effects of lecithin on the loading of heparin onto PLGA NPs and on the surface conductance were analyzed. The electronic micrographs revealed that spherical colloids were prepared and the incorporation of heparin caused a slight coalescence of the particles. In addition, the average diameter of heparin-modified PLGA NPs was between 70 and 220 nm. An increase in the weight percentage of lecithin or in the concentration of heparin enlarged the average diameter. Based on constant amount of surfactants, the loading efficiency of heparin on the particle surfaces reached a maximum when the weight percentage of lecithin was 50%. Moreover, the surface conductance of heparin-modified PLGA NPs was improved by an increased weight percentage of lecithin. A high concentration of heparin in microemulsion also promoted the loading efficiency and surface conductance of heparin-modified PLGA NPs.     

Self-assembling properties of glycolipid biosurfactants and their potential applications

Biosurfactants (BS) produced by a variety of microorganisms show unique properties (e.g. mild production conditions, multi-functionality, higher environmental compatibility) compared to their chemical counterparts. The numerous advantages of BS have prompted applications not only in the food, cosmetic, and pharmaceutical industries but in environmental protection and energy-saving technology as well. Among BS, “Glycolipid type” BS are the most promising, due to high productivity from renewable resources and versatile interfacial and biochemical properties. Mannosylerythritol lipids (MELs), which are glycolipid BS produced by yeast strains of the genus Pseudozyma, not only exhibit excellent surface activities but also self-assemble to form different lyotropic liquid crystalline phases such as sponge (L₃), bicontinuous cubic (V₂) or lammellar (L_α). They also show induction of cell-differentiation against human leukemia cells, and high binding affinity towards lectins and immunoglobulins. Recently, the cationic liposome bearing MELs has been demonstrated to increase dramatically the efficiency of gene transfection into mammalian cells. These features of BS should broaden the applications in new advanced technologies. The current status of R&D on glycolipid BS, especially their functions and potential applications, is discussed.     

微乳液增敏催化荧光光度法测定叶酸的研究

报道了在微乳液介质中,当pH=3.5,以353 nm为激发波长,444 nm为发射波长,在该波长处测定钯(Ⅱ)作为催化剂催化KIO4与叶酸之间反应的荧光强度,从而间接测定叶酸的新方法.在最佳条件下,测定叶酸的线性范围为1.0×10-6～6.0×10-5 mol/L,检出限为1.0×10-7 mol/L,相对标准偏差小于2.20%,加标回收率在97%～105%范围内.CTMAB微乳液的引入可提高体系的灵敏度.结果表明,该方法具有很高的灵敏度、选择性和稳定性,可直接用于各种样品中叶酸的测定.     

稀土掺杂氟化镁钾纳米晶的合成及其光谱特性

采用微乳液法合成了Eu²⁺,Ce³⁺单掺和双掺KMgF₃纳米晶,分析了样品的结构与形态. 结果表明,所合成的样品均为单相,颗粒粒度分布均匀. 讨论了光谱特性并与高温固相法合成的产物作了对比. 研究发现,在KMgF₃纳米晶双掺体系中,由于Eu²⁺和Ce³⁺竞争吸收激发能,只能观察到Ce³⁺的发射带; 而在KMgF3多晶共掺体系中,因为存在Ce³⁺→Eu²⁺能量传递过程,只能观察到Eu²⁺的发射峰.     

蒽在SDS/BA/H2O体系中的光谱特征

用紫外-可见吸收光谱和荧光发射光谱研究了蒽在不同组成和结构的十二烷基硫酸钠(SDS)/苯甲醇(BA)/H20微乳液中的光谱特征,探讨了微乳液组成和结构对蒽光谱特征的影响,阐述了蒽在微乳液中的定位。结果表明,蒽位于O/W微乳液的膜相和油核;在SDS/BA/H2O W/O微乳液中,蒽定位于油连续相。     

AOT-水-正庚烷微乳液中脂肪酶催化拆分消旋布洛芬的研究

以手性高效液相色谱分析法为检测手段,研究了AOT-水-正庚烷微乳液反应介质中,脂肪酶催化消旋布洛芬的不对称酯合成反应。结果表明,在此反应介质中,消旋布洛芬与正辛醇能顺利地进行酯合成反应,转化率达0．3613,产物为光学纯度很高的S-构型布洛芬辛酯,其对映体过量值为0．9732。微乳液中的含水量叫。值（水与表面活性剂的摩尔数比）及AOT浓度主要影响酯合成反应转化率,对产物对映体过量值没有太大的影响;不同链长的脂肪醇不仅影响酯合成反应速率及其对应的最佳ω0值,还影响产物的对映体过量值。     

Size-controlled synthesis of SnO2 nanoparticles using reverse microemulsion method

Tin oxide nanoparticles were prepared using an ionic surfactant (sodium dodecyl sulfate) and tin (IV) chloride as an inorganic precursor via the reverse microemulsion method. The size of the nanoparticles is controlled by variation of water-to-surfactant ratio. Eliminating of surfactant in prepared nanoparticles was confirmed by the infrared spectroscopy after sequential calcinations. Transmission electron microscopy, surface area, pore volume, average pore diameter, pore size distribution and X-ray diffraction results were used for evaluation of size distribution, shape and structure of prepared SnO₂ nanoparticles. Transmission electron micrographs confirmed that the obtained materials are spherical nanoparticles. The X-ray diffraction results show the crystalline phases of all samples are SnO₂ with tetragonal structured crystal. In addition, the X-ray diffraction and transmission electron microscopy data showed that the size of SnO₂ nanoparticles decreased with decreasing the water-to-surfactant ratio.     

Anionic microemulsion to solvent stacking for on‐line sample concentration of cationic analytes in capillary electrophoresis

The common SDS microemulsion (i.e. 3.3% SDS, 0.8% octane, and 6.6% butanol) and organic solvents were investigated for the stacking of cationic drugs in capillary zone electrophoresis using a low pH separation electrolyte. The sample was prepared in the acidic microemulsion and a high percentage of organic solvent was included in the electrolyte at anodic end of capillary. The stacking mechanism was similar to micelle to solvent stacking where the micelles were replaced by the microemulsion for the transport of analytes to the organic solvent rich boundary. This boundary is found between the microemulsion and anodic electrolyte. The effective electrophoretic mobility of the cations reversed from the direction of the anode in the microemulsion to the cathode in the boundary. Microemulsion to solvent stacking was successfully achieved with 40% ACN in the anodic electrolyte and hydrodynamic sample injection of 21 s at 1000 mbar (equivalent to 30% of the effective length). The sensitivity enhancement factors in terms of peak height and corrected peak area were 15 to 35 and 21 to 47, respectively. The linearity R² in terms of corrected peak area were >0.999. Interday precisions (%RSD, n = 6) were 3.3–4.0% for corrected peak area and 2.0–3.0% for migration time. Application to spiked real sample is also presented.     

Fluorescence Quenching of Anthracene by N,N-Diethylaniline and Phenothiazine in Triton X-100/n-C10H21OH/H2O Microemulsion

IntroductionDuring the last decade,microemulsions haveplayed important roles in the development of bio-logical,material,environmental and other relatedfields[1— 4] .Although photo- induced electron trans-fer processes are of considerable interest in biologyand chemistry,up to now,most of the studies ofthe photo- induced electron transfer in micelle andinverse micelle have been limited to one- or two-component water/surfactant systems[5] .As theirextensions to microemulsion,only a very limited…