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1.
Shen D Han B Dong Y Wu W Chen J Zhang J 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(4):1228-1234
The effect of compressed CO2 on the solubilization capacity of water in reverse micelles of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in longer chain n-alkanes was studied at different temperatures and pressures. It was found that the amount of solubilized water is increased considerably by CO2 in a suitable pressure range. The suitable CO2 pressure range in which the solubilization capacity of water could be enhanced decreased with increasing W0 (water-to-AOT molar ratio). The microenvironments in the CO2-stabilized reverse micelles were investigated by UV/Vis adsorption spectroscopy with methyl orange (MO) as probe. The mechanism by which the reverse micelles are stabilized by CO2 is discussed in detail. The main reason is likely to be that CO2 has a much smaller molecular volume than the n-alkane solvents studied in this work. Therefore, it can penetrate the interfacial film of the reverse micelles and stabilize them by increasing the rigidity of the micellar interface and thus reducing the attractive interaction between the droplets. However, if the CO2 pressure is too high, the solvent strength of the solvents is reduced markedly, and this induces phase separation in the micellar solution. 相似文献
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Chen J Zhang J Han B Feng X Hou M Li W Zhang Z 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(31):8067-8074
The effect of compressed CO2 on the critical micelle concentration (cmc) and aggregation number of sodium bis-2-ethylhexylsulfosuccinate (AOT) reverse micelles in isooctane solution was studied by UV/Vis and fluorescence spectroscopy methods in the temperature range of 303.2-318.2 K and at different pressures or mole fractions of CO2 (X(CO2)). The capacity of the reverse micelles to solubilize water was also determined by direct observation. The standard Gibbs free energy (DeltaGo(m)), standard enthalpy (DeltaHo(m)), and standard entropy (DeltaSo(m)) for the formation of the reverse micelles were calculated by using the cmc data determined. It was discovered that the cmc versus X(CO2) curve and the DeltaGo(m) versus X(CO2) curve for a fixed temperature have a minimum, and the aggregation number and water-solubilization capacity of the reverse micelles reach a maximum at the X(CO2) value corresponding to that minimum. These results indicate that CO2 at a suitable concentration favors the formation of and can stabilize AOT reverse micelles. A detailed thermodynamic study showed that the driving force for the formation of the reverse micelles is entropy. 相似文献
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Shen D Zhang R Han B Dong Y Wu W Zhang J Li J Jiang T Liu Z 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(20):5123-5128
The effect of compressed CO2 and ethylene on the properties of Triton X-100/cyclohexane/water systems was studied at different temperatures and pressures. Surprisingly, it was discovered that the compressed gases had the functions of co-surfactants. At suitable pressures, the water-to-surfactant molar ratio (W0) was enhanced significantly by the dissolution of the gas in the solution. The microenvironment in the reverse micelles was investigated by UV-visible spectroscopy by using methyl orange (MO) as a probe. The influence of n-hexane, Na2CO3, NaHCO3, H2C2O4, and CaCl2 at various concentrations on the solubilization of water in the absence of compressed gases was also investigated in order to obtain some information about the mechanism of the interesting phenomenon. This new route to stabilize reverse micelles may have potential applications to other similar systems. Moreover, the results of this work provide some useful information to get insight into the mechanism of co-surfactants, because a conventional co-surfactant usually contains both polar group and hydrocarbon chain, and it is very difficult to clarify the functions these two groups, while the gases used in this work are small nonpolar molecules, which solely have the function of the hydrocarbon chain in a co-surfactant. 相似文献
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Minmin Tian Emin Arca Zdenek Tuzar Stephen E. Webber Petr Munk 《Journal of Polymer Science.Polymer Physics》1995,33(12):1713-1722
Block copolymers, when dissolved in a selective solvent, form spherical micelles. These micelles can selectively solubilize organic molecules otherwise insoluble in the pure solvent. In this study, we report solubilization of organic molecules by styrene-methacrylic acid block copolymer micelles in aqueous buffers. A light scattering technique was developed to determine the extent of micellar solubilization. Our results indicate that the extent of micellar solubilization depends on the chemical nature of organic molecules, specifically, on the interactions between the organic compound and polystyrene. A thermodynamic model has been developed to describe micellar solubilization. The theoretical calculation agrees reasonably well with the experimental results for two micellar samples examined. ©1995 John Wiley & Sons, Inc. 相似文献
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Wei Li Jianling Zhang Dr. Yueju Zhao Minqiang Hou Dr. Buxing Han Prof. Dr. Cailan Yu Jianping Ye 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(4):1296-1305
The study of the micelle‐to‐vesicle transition (MVT) is of great importance from both theoretical and practical points of view. Herein, we studied the effect of compressed CO2 on the aggregation behavior of dodecyltrimethylammonium bromide (DTAB)/sodium dodecyl sulfate (SDS) mixed surfactants in aqueous solution by means of direct observation, turbidity and conductivity measurements, steady‐state fluorescence, time‐resolved fluorescence quenching (TRFQ), fluorescence quantum yield, and template methods. Interestingly, all these approaches showed that compressed CO2 could induce the MVT in the surfactant system, and the vesicles returned to the micelles simply by depressurization; that is, CO2 can be used to switch the MVT reversibly by controlling pressure. Some other gases, such as methane, ethylene, and ethane, could also induce the MVT of the surfactant solution. A possible mechanism is proposed on the basis of the packing‐parameter theory and thermodynamic principles. It is shown that the mechanism of the MVT induced by a nonpolar gas is different from the MVT induced by polar and electrolyte additives. 相似文献
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Zhang J Liu Z Han B Liu D Chen J He J Jiang T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(14):3531-3536
In this work, a novel route to synthesize polymer/metal composite nanospheres has been proposed. This method combines the advantages that the polymer chains collapse and entangle in the presence of compressed CO(2), which acts as antisolvent, and the metal nanoparticles and polymers can be precipitated simultaneously from micellar solutions by the easy control of CO(2) pressure. Ag/polystyrene (PS) nanocomposites have been successfully prepared using this method. The transmission electronic micrographs (TEM) of the obtained nanocomposites show that the smaller Ag nanoparticles are immobilized by PS nanospheres of about 50 nm; the phase structure was characterized by X-ray diffraction (XRD). The Ag/PS nanocomposites show absorption properties at a wavelength of approximately 417 nm. The results of X-ray photoelectron spectra (XPS) and FT-IR spectra indicate that there is no chemical linkage or strong interaction between PS and Ag nanoparticles in the resultant products. This method has many potential advantages for applications and may easily be applied to the preparation of a range of inorganic/ polymer composite nanoparticles. 相似文献
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The micellar radii and the electron density of the polar and non polar regions in micelles have been determined by a small-angle X-ray scattering (SAXS) technique originally designed by Luzzati et al. and subsequently modified by Larsson. The model employed shows the micellar structure as consisting of a liquid hydrocarbon core and a polar shell comprising the ionic polar head groups plus the diffuse double layer of bound counterions. The shortcomings of the model are discussed in the light of a recent paper by Hayter & Penfold providing general support for the parameters obtained and the conclusions drawn.The results found for the binary aqueous systems of potassium hexanoate, sodium octanoate and sodium decanoate describes the micelles as having quite an open structure with a rather small truly anhydrous hydrocarbon core. The low electron density contrast found between the polar layer and the surrounding media prevents us from drawing conclusions as to the absolute value of the polar (total) micellar radius, although the changes in this radius seem relevant. The octane-1, 8-diol is found to partly penetrate the hydrocarbon core but mostly to reside in the polar shell or to remain in the bulk solvent. Both the cyclohexane and carbon tetrachloride seem to be solubilized in the interior of the micelle, the former causing a considerable swelling of the micelle. 相似文献
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介绍了在利用CTAB/正辛醇:三氯甲烷(4:1V/V)反胶团体系对牛血清白蛋白(BSA)进行相转移中,通过对萃取体系水相的pH值、离子强度、两液相的体积比、小分子糖(葡萄糖、蔗糖)及助表面活性剂(直链醇分子)等因素的改变,探讨了BSA在阳离子表面活性剂体系的萃取机理;研究结果表明选择合适的条件提取BSA时,萃取率可达到97%,反萃率达到了85%;找到实现牛血清白蛋白分离提纯的有效方法。 相似文献
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The solubilization of styrene molecules in aqueous dodeciltrimethylammonium Hydroxide (DTAOH) solution was studied by UV-Vis
spectroscopy. In short, fully ionized DTAOH aggregates the styrene molecules in the micelle double layer, oriented with their
vinyl group to the micelle core and the aryl ring to the intermicellar solution. At increased surfactant concentration, when
the aggregates incorporate counterions in their Stern layer, the orientation is maintained, but styrene molecules gradually
penetrate into the micelle core as the micelle size and degree of counterion union increased, until they were completely immersed
in the hydrocarbon core of rod-like micelles.
Received: 6 November 1996 Accepted: 10 February 1997 相似文献
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Calorimetric study of the solubilization of cholesterol,retinol and retinal by reversed AOT micelles
A. D'Aprano I. D. Donato F. Pinio Doctor in Biology thesis of F. Pinio V. Turco Liveri 《Journal of solution chemistry》1990,19(11):1055-1061
Distribution constants and standard enthalpies of transfer of cholesterol, retinol and retinal partitioned between n-heptane and water containing reversed sodium bis(2-ethylhexyl) sulfosuccinate (AOT) micelles as a function of the molar concentration ratio (R=[water]/[AOT]) were evaluated by a calorimetric method. The results indicate that, in spite of the bulky hydrocarbon radical, these solubilizates behave like alcohols with a short alkyl chain. Moreover, cholesterol is always solubilized in the palisade layer of the reversed micelles whereas retinol and retinal are preferentially solubilized in the aqueous pseudophase. The influence of the enthalpic and the entropic contributions to the transfer of the solubilizates from n-heptane to reversed AOT micelles are also considered. 相似文献
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A. D'Aprano I. D. Donato F. Pinio V. Turco Liveri 《Journal of solution chemistry》1989,18(10):949-955
A calorimetric method to evaluate, at the same time, the distribution constant and the standard enthalpy of transfer of a solute partitioned between organic phase and reversed micelles is proposed. The method was applied to the partition of methanol, 1-propanol and 1-pentanol between n-heptane and AOT reversed micelles containing water at 25°C. The results show that the distribution constant decreases as the alcohol alkyl chain length increases and that the solubilization site can change as the water content of reversed AOT micelles increases. In particular, at sufficiently high water content, methanol seems to be preferably solubilized in the aqueous pseudophase whereas 1-pentanol prefers always the palisade layer as site of solubilization.In part from Doctor in Biology thesis of F. Pinio, University of Palermo, Italy. 相似文献
14.
Differences between the rates of oxidation of substrates by horseradish peroxidase in buffer, aqueous micellar solution of
Brij 35 and in reverse micelles formed of Brij 30 in several hydrocarbons are discussed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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Rui ZHANG Jun HE Jun LIU Bu Xing HAN* Guan Ying YANG The Center for Molecular Sciences Institute of Chemistry Chinese Academy of Sciences Beijing 《中国化学快报》2002,13(9)
To date, polar microenvironments in apolar solvents have been successfully used in different ways, such as separation of proteins1, enzymatic or catalytic reactions in reverse micelles2. It is obvious that investigation of new method to create polar microenvironments is of great importance to both pure and applied sciences, and it is desirable that forming and breaking the microenvironments can be easily controlled. Compressed CO2 can dissolve in many organic solvents and the solubility can … 相似文献
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Zhang J Han B Zhao Y Li J Yang G 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(15):4266-4272
The micellization of amphiphilic molecules is an interesting topic from both theoretical and practical points of view. Herein we have studied the effects of compressed CO(2) on the micellization of Pluronics in water by means of fluorescence, UV/Vis spectra, and small-angle X-ray scattering. It was found that CO(2) can induce the micellization of Pluronics in water, and the micelle can return to the initial state of molecular dispersion after depressurization. Therefore, the micellization of Pluronics in water can be switched through the easy control of pressure. Different from the common micelles with hydrophobic cores, interestingly, this CO(2)-induced micelle has an amphiphilic core, in which hydrophobic and hydrophilic domains coexist. On account of the ability to dissolve both polar and nonpolar components in the micellar core, the CO(2)-induced micelles can improve the reagent compatibilities frequently encountered in various applications. In an attempt to address this advantage, this micelle was utilized as template to the one-step synthesis of Au/silica core-shell composite nanoparticles. Furthermore, the underlying mechanism for the CO(2)-induced micellization of Pluronics in water was investigated by a series of experiments. 相似文献
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Zhao Y Zhang J Han B Zhang C Li W Feng X Hou M Yang G 《Langmuir : the ACS journal of surfaces and colloids》2008,24(17):9328-9333
Lecithin is a very useful biosurfactant. In this work, the effects of compressed CO 2 on the critical micelle concentration (cmc) of lecithin in cyclohexane and solubilization of water, lysozyme, and PdCl 2 in the lecithin reverse micelles were studied. The micropolarity and pH value of the polar cores of the reverse micelles with and without CO 2 were also investigated. It was found that CO 2 could reduce the cmc of the micellar solution and enhance the capacity of the reverse micelles to solubilize water, the biomolecule, and the inorganic salt significantly. Moreover, the water pools could not be formed in the reverse micelles in the absence of CO 2 because of the limited amount of water solubilized. However, the water pools could be formed in the presence of CO 2 because large amounts of water could be solubilized. All of these provide more opportunity for effective utilization of this green surfactant. The possible mechanism for tuning the properties of the reverse micelles by CO 2 is discussed. 相似文献
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The effect of Cibacron Blue 3GA (CB) on the fluorescence emission spectra of bovine serum albumin (BSA) was investigated in
cationic reversed micelles formed with cetyltrimethylammonium bromide (CTAB) compared with that in aqueous phase. The anionic
CB had electrostatic interactions with cationic CTAB and affinity interactions with BSA in the reversed micelles. The addition
of CB in the reversed micellar phase led to a great decrease in the fluorescence intensity of BSA and a remarkable red shift
of the wavelength of emission maximum (λmax). The fluorescence intensity of BSA decreased and the λmax decreased 5 nm (blue shift) without the addition of CB in the reversed micellar phase. The fluorescence intensity of BSA
with the addition of CB had the strongest value in the aqueous phase with the presence of CTAB, a less strong value in the
reversed micellar phase, and a weak value in the aqueous phase without the presence of CTAB. The increase in λmax of BSA with the addition of CB in the reversed micellar phase might indicate the decrease in the hydrophobic microenvironment
of the Trp residue of BSA, contrary to those microenvironments in the absence of CB. 相似文献