双连续微乳体系中PbS纳米管的控制合成(英文)

PbS nanotubes were synthesized by the tiny water channels in bicontinuous microemulsions consisted of p-octyl polyethylene glycol phenylether (OP)/n-amyl alcohol/cyclohexane/water. The possible formation mechanism of PbS nanotubes is also discussed based on their shape evolutions. The results indicate that the formation of PbS nanotubes is probably via the process of the nucleation, growth, assemblage and crystallization.     

Synthesis and characterization of PbS nanorods in W/O microemulsion system

PbS nanorods have been successfully synthesized in water-in-oil (W/O) microemulsion containing non-ionic surfactant OP, n-pentanol, cyclohexane, and aqueous solution. The effects of the molar ratio of water to surfactant (ω₀), the concentration of reactants and the ageing time on the morphologies of PbS nanoparticles were investigated. The microstructures, morphologies and properties of the synthesized products were characterized by means of X-ray diffraction, transmission electron microscopy, and ultraviolet-visible (UV-VIS) absorption spectroscopy, respectively. The results showed that the synthesized rod-like products are composed of cubic phase PbS. These nanorods have an average diameter of about 100 nm, and an average length of about 500 nm. In the UV-VIS absorption spectrum, the absorption edge of PbS nanorods exhibit a blue shift compared with that of bulk PbS, indicating the quantum confinement effect of PbS nano-particles     

Lipase-catalyzed enantioselective esterifications using different microemulsion-based gels

Chiral esters with high optical purity have been synthesized at 298.2 K from racemic 2-octanol and alkanoic acids using the commerical lipases fromChromobacterium viscosum (CV) orCandida sp. (SP 525) immobilized in microemulsion-based gelatin gels. The microemulsions consisted of water and alkanes stabilized by the anionic surfactant sodium 1,4-bis(2-ethylhexyl) sulfosuccinate (AOT) and the naturally occurring zwitterionic surfactant soybean lecithin, respectively. The enzymes were solubilized both in water-in-oil (W/O) microemulsions and in microemulsions with a bicontinuous structure. Different microstructures of the gels were chosen since the enzyme may undergo conformational changes in different environments resulting in different catalytic efficiencies toward competing substrates. Therefore, it is of great fundamental interest to know the phase behaviour and the microstructures of the used microemulsion systems. Phase diagrams were determined at 298.2 K for the systems water-hexane-AOT and ethanol/water (11)-hexadecane-soybean lecithin. The former system exhibited a large one-phase W/O microemulsion region, while in the latter a small one-phase region with bicontinuous structure was present. The kinetic enantiomeric ratios (E-values), as determined from enantiomeric excess (e.e.) values at a conversion below 0.5, were higher both in the W/O microemulsion as well as in the bicontinuous microemulsion using the SP 525 lipase, than using the CV lipase. On the other hand, the conversions were higher using gels based on W/O microemulsions (AOT stabilized) than using gels based on microemulsions with a bicontinuous structure (lecithin stabilized).     

无表面活性剂微乳液体系：N,N－二甲基甲酰胺/呋喃甲醛/水

通常微乳液一般由四个组分构成：水相、油相、表面活性剂和助表面活性剂。本文报道了一种不含表面活性剂的微乳液体系(简称SFME),由呋喃甲醛(油相),水和N,N－二甲基甲酰胺(DMF)三组分构成,不含传统的表面活性剂。对其相行为进行了研究,发现存在一个单相微乳液区和一个两相平衡区。采用电导率法和冷冻蚀刻电镜(FF-TEM)考察了单相区域中微乳液的微结构,结果表明可分为油包水(O/W)、双连续(BC)和水包油(W/O)三个区域。液滴直径介于40-70nm。     

Hollow-fiber membranes coated with polymerizable bicontinuous microemulsions

A new method has been successfully employed to prepare hollow-fiber membranes by coating and polymerizing bicontinuous microemulsions onto the internal surfaces of hollow-fiber membranes. The bicontinuous microemulsion consisting of water, a polymerizable zwitterionic surfactant of acryloyloxyundecyl dimethylammonio acetate, methyl methacrylate, and 2-hydroxylethyl methacrylate (HEMA) can form a transparent polymer thin film after polymerization. The hollow-fiber membranes as the supports for microemulsion coatings were fabricated from the spinning solution of polyethersulfone/diethylene glycol/N-methyl-2-pyrrolidone. The microemulsion coated hollow-fiber membranes were evaluated by the separation efficiency and the permeation rate of polyethylene glycol (PEG) solutions. The performance of coated membrane on the PEG separation is strongly dependent on the concentration of HEMA and water in precursor bicontinuous microemulsions. The pore size of the hollow-fiber membranes can be regulated between about 2 to 40 nm by varying the composition of precursor bicontinuous microemulsions. The characteristics of the coated membranes is believed to be directly related to the bicontinuous structures of precursor bicontinuous microemulsions. The use of polymerizable bicontinuous microemulsions enable one to better control the microstructures of coated membranes via in situ polymerization.     

Soft template inducing synthesis of CaC2O4 nanotubes

CaC₂O₄ nanotubes were controllably synthesized via the tiny water channels in the bicontinuous microemulsion at room temperature. The products were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and fourier transform infrared spectroscopy (FT-IR). The results indicate that as-obtained products are calcium oxalate monohydrate (COM) crystal. These nanotubes have diameters of about 100 nm and lengths of about 700 nm. The key controlling parameters such as the reactant concentration (ratio) and the aging time have been investigated. The possible formation mechanism of the CaC₂O₄ nanotubes was also discussed.     

Hydrotrope‐Solubilization Action of Urea in CTAB/n‐C5H11‐OH/H2O System

Urea can enhance the aqueous solubility of surfactant CTAB (hexadecyltrimethylammonium bromide) when it shows the hydrotrope action. It will show the hydrotrope‐solubilization action when the solubilized amount of n‐C₅H₁₁OH in O/W microemulsion and that of water in W/O microemulsion are increased. The mechanism of the hydrotrope‐solubilization action of urea is the increase of the stability of W/O and O/W microemulsion and structural transition from the lamellar liquid crystalline phase to the bicontinuous structure.     

Study on the Polarity of bmimPF6/Tween80/toluene Microemulsion Characterized by UV-Visible Spectroscopy

With the aid of nonionic surfactant Tween80, the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF₆) forms nonaqueous microemulsions with toluene. The phase diagram of the ternary system was prepared at 25°C. It was demonstrated that there were a single-phase region and a two-phase region in the ternary phase diagram. The single-phase region could be further divided into toluene-in-bmimPF₆, bicontinuous and bmimPF₆-in-toluene microemulsion regions by electrical conductivity. And by the use of methyl orange as an absorption probe, the polarity of the bmimPF₆-in-toluene microemulsion was probed by UV-vis spectroscopy. A relatively constant polarity of the microemulsion droplets is obtained in the bmimPF₆ microemulsion.     

Coating of multiwalled carbon nanotubes with polymer nanospheres through microemulsion polymerization

We report a simple and noncovalent method for coating multiwalled carbon nanotubes (MWCNTs) with polyaniline (PANI) nanospheres using a microemulsion polymerization method. In this method, aniline polymerization is performed with MWCNTs in the presence of sodium dodecyl sulfate (SDS), which serves as both a surfactant and a dopant. Morphological, structural, thermal, and electrical properties of MWCNT–PANI nanocomposites were analyzed. The TEM results of the nanocomposites prepared with surfactant reveal that 30–50-nm-diameter PANI nanospheres were coated on the surface of the MWCNTs. Composites prepared without surfactant were found to be in core–sheath-type cable structures. The conductivities of the nanocomposites synthesized through microemulsion polymerization were found to be one order of magnitude higher than both the conductivities of pure PANI and the composites prepared via in situ chemical polymerization without an assisting SDS surfactant. The mechanism for the formation of nanostructured composites is presented.     

Hydrolysis of Hydrophobic Esters in a Bicontinuous Microemulsion Catalysed by Lipase B from Candida antarctica

Selective enzyme‐catalysed biotransformations offer great potential in organic chemistry. However, special requirements are needed to achieve optimum enzyme activity and stability. A bicontinuous microemulsion is proposed as reaction medium because of its large connected interface between oil and water domains at which a lipase can adsorb and convert substrates in the oil phase of the microemulsion. Herein, a microemulsion consisting of buffer–n‐octane–nonionic surfactant C_iE_j was used to investigate the key factors that determine hydrolyses of p‐nitrophenyl esters catalysed by the lipase B from Candida antarctica (CalB). The highest CalB activity was found around 44 °C in the absence of NaCl and substrates with larger alkyl chains were better hydrolysed than their short‐chained homologues. The CalB activity was determined using two different co‐surfactants, namely the phospholipid 1,2‐dioleoyl‐sn‐glycero‐3‐phosphocholine (DOPC) and the sugar surfactant decyl β‐D ‐glucopyranoside (β‐C₁₀G₁). The results show the CalB activity as linear function of both enzyme and substrate concentration with an enhanced activity when the sugar surfactant is used as co‐surfactant.     

Sub-zero temperature behaviour of non-ionic microemulsions in the presence of propylene glycol by DSC

The five-component system is quite unique since it allows formation of reverse micelles with hydrophilic ethoxylated alcohol in the presence of ethanol and it facilitates dilution by water/propylene glycol (1,2-propanediol, PG) aqueous phase, all the way from a water-in-oil (W/O) microemulsion via a bicontinuous phase to an oil-in-water (O/W) microemulsion.The surfactant/alcohol/PG can strongly bound water in the inner phase so that it freezes below –10°C and acts in part as bound water and in part as non-freezable water. Upon dilution to >30 mass% aqueous phase (water/PG at constant mass ratio of 1/1) the system becomes bicontinuous and the aqueous layers are composed again from bound water. Even after complete inversion to O/W microemulsions the water in the continuous phase is strongly interacting with the PG/surfactant and remains bound or non-freezable. Water/PG/ethanol have a strong effect on the head groups (freezing below -10°C) and also on the hydrophobic tails (recrystallizing and melting) at lower temperature when dilution exceeds 45 mass% water/PG (1/1).No free water was detected neither in the W/O microemulsion's inner droplet domains nor when the microemulsion was either bicontinuous or when it was inversed to O/W. Continuous phase of resulting O/W microemulsion apparently is based on water/PG at a mass ratio of 1/1.This revised version was published online in November 2005 with corrections to the Cover Date.     

Structure and phase behaviour of the ternary system water, n-heptane and the nonionic surfactant Igepal® CA520

The phase behavior of the system water, n-heptane and the nonionic surfactant Igepal^® CA520 has been studied by visual inspection, high-performance liquid chromatography, polarizing microscopy and freeze-fracture electron microscopy. The phase diagram at 25?°C contains two large homogeneous microemulsion phases, an extended region of a lamellar liquid crystalline structure and some two- and three-phase regions. The oil-rich part of the phase diagram has been investigated by static and dynamic light scattering in order to examine the behavior of the collective diffusion coefficient and the scattering intensity in the presence of increasing concentrations of water, starting from the binary system of n-heptane and Igepal^® CA520. The results suggested that at a very low water content the aggregates of the microemulsion are small. With the exception of this region the structure is bicontinuous.     

Hydrotrope and hydrotrope-solubilization action of cephanone in CTAB/<Emphasis Type="Italic">n</Emphasis>-C<Subscript>5</Subscript>H<Subscript>11</Subscript>OH/H<Subscript>2</Subscript>O system

Cephanone is found to show the hydrotrope and hydrotrope-solubilization action in CTAB/n-C₅H₁₁OH/H₂O system. Cephanone can increase the solubilities of cationic surfactant CTAB or n-C₅H₁₁OH in water and water in n-C₅H₁₁OH. It can also increase the solubilization amount of n-C₅H₁₁OH in O/W microemulsion and that of water in W/O microemulsion, which makes the two regions of O/W and W/O microemulsion larger, and even linked together. The mechanism of the hydrotrope-solubilization action of cephanone is related to the location of cephanone in the palisade of microemulsion which causes the stability of O/W and W/O microemulsion to be enhanced and that of lamellar liquid crystal to be reduced. Therefore, the mechanism of hydrotrope-solubilization is the structural transition from lamellar liquid crystal to the bicontinuous structure.     

醇对高效氯氟氰菊酯微乳液相图的影响

通过电导率的测定研究了高效氯氟氰菊酯微乳液的结构结构及结构转变。在表面活性剂、高效氯氟氰菊酯环己酮溶液、醇相对含量一定的情况下,当醇为乙醇时,微乳液经历了由W/O到双连续最后到O/W型的变化;当醇为正辛醇时,微乳液经历了由W/O到液晶、双连续最后到O/W型的变化。绘制了不同条件下高效氯氟氰菊酯微乳体系的拟三元相图,讨论了醇种类、醇含量对各类型微乳区形成的影响。结果表明,随着醇碳链的增大,微乳区面积先增大后减小;醇(正辛醇)固定时,随着醇含量增加,微乳区面积先减小后增大。     

PbS nanostructures synthesized via surfactant assisted mechanochemical route

PbS nanocrystals using surfactant assisted mechanochemical route has been successfully prepared. The methods of XRD, SEM, surface area and particle size measurements were used for nanocrystals characterization. The XRD patterns confirmed the presence of galena PbS (JCPDS 5–592) whatever treatment conditions were applied. The strong observable peaks indicate the highly crystalline nature in formation of PbS nanostructures where preferential crystal growth in the (200) direction after chelating agent (EDTANa₂•2H₂O) addition has been observed. The mean volume weighted crystallite size 4.9 nm and 35 nm has been calculated from XRD data using Williamson-Hall method for PbS synthesized without and/or with chelating agent, respectively corresponding with surface weighted crystallites sizes of 2.9 and 18.8 nm. The sample prepared without surfactant yields the smaller crystallites and the higher microstrain compared with surfactant assisted synthesis. The obtained results illustrate a possibility to manipulate crystal morphology by combining effect of milling and surfactant application.      

Phase Diagram,Electrical Conductivity,and Viscosity Study of Alpha-Sulfonated Methyl Esters Derived from Palm Stearin/1-Pentanol/Hydrocarbon/Water Systems

Microemulsion region of sodium salt alpha-sulfonated methyl ester derived from palm stearin (α-SMEPS)/1-pentanol/alkane/water systems was constructed and investigated at 30.0 ± 0.1°C. The water-in-oil (w/o) microemulsion, bicontinuous structure, and oil-in-water (o/w) microemulsion regions were determined by both conductivity and viscosity methods. Results showed that the microemulsion region decreases and moved towards (α-SMEPS f 1-pentanol) rich corner with the increase in hydrocarbon chain length of alkane from C8 to C16. The changes in alkane chain length from C16 to C8 were found to have shifted the o/w microemulsion f bicontinuous structure f w/o microemulsion transitions of α-SMEPS self-assembly to the rich water corner.     

Hydrotrope and hydrotrope-solubilization action of penicillin-K in CTAB/n-C5H11OH/H2O system

Penicillin potassium salt (penicillin-K) is found to show hydrotrope action, which can increase the solubility of cationic surfactant CTAB in water. Penicillin-K also shows hydrotrope-solubilization action, which makes the W/O and O/W microemulsion more stable and increases the solubilized amount of n-C₅H₁₁OH in O/W microemulsion and that of water in W/O microemulsion for CTAB/n-C₅H₁₁OH/H₂O system. However, in this system, the presence of penicillin-K can decrease the stability of the lamellar liquid crystal phase due to its structure change to bicontinuous, which are proved by the mechanism of its hydrotrope-solubilization action.     

Extraction of cobalt by the AOT microemulsion system

The extraction of cobalt by Winsor II microemulsion system was studied. In the bis (2-ethylhexyl) sulfosuccinate sodium salt (AOT)/n-pentanol/n-heptane/NaCl system, AOT was used as a anionic surfactant to form microemulsion in n-heptane, n-pentanol was injected in the microemulsion as a cosurfactant. Co(II) was found to be extracted into the microemulsion phase due to ion pair formation such as Co²⁺(R–SO₃ ⁻)Cl. The influence of different parameters such as the volume ratio of aqueous phase to microemulsion, surfactant concentration, pH of the feed solutions, cosurfactant concentration as well as temperature on the extraction yield (E%) were investigated. The results showed that it was possible to extract 95% of cobalt by the AOT Winsor II microemulsion.     

Synthesis of Silicalite-1 in Bicontinuous Microemulsion Containing AOT

Silicalite-1 has been hydrothermally synthesized in a bicontinuous microemulsion of tetraethylenepentamine-sodium bis(2-ethylhexly) sulfosuccinate (AOT)-water system containing fluoride ions. The presence of AOT (an anionic surfactant) has been found to be essential for the formation of Silicalite-1 in bulk tetraethylene pentamine solvent. The tetrahedral binding sites of silicon atom have been confirmed by 29Si magic angle spinning NMR and FT-IR spectra. Thermogravimetric and differential thermal analysis studies on as-synthesized Silicalite-1 and X-ray diffraction pattern for calcined product established their structural stability. The scanning electron micrographs show the twinned and uniform morphology of crystals. The presence of additive (AOT) lengthens the nucleation period and helps to produce a large size crystal of Silicalite-1. Copyright 1999 Academic Press.     

Microstructure and structural transition in palm-kernel oil microemulsion using 1.5-order differential electroanalysis

The microemulsification in palm-kernel oil/cetyltrimethylammonium bromide/iso-pentanol/water system is investigated. The effect of iso-pentanol concentration in microemulsions on the size of single-phase microemulsion region is also discussed. It is found that the maximum microemulsion domain is obtained when iso-pentanol-to-cetyltrimethylammonium bromide mass ratio is 1.75. The diffusion coefficients of electroactive probe (ferrocene) in microemulsion microenvironment are measured by 1.5-order differential electroanalysis. The microstructure and structural transition from water-in-oil to oil-in-water microemulsions through a bicontinuous structure is examined. The results are found to be in agreement with that of conductivity measurements.