Control of nucleation and growth of gold nanoparticles in AOT/Span80/isooctane mixed reverse micelles

In this study, we demonstrate that mixed reverse micelles are good candidates to be used as nanoreactors for formation of shape-controlled high-quality colloidal nanocrystals and nanowires under mild conditions. Manipulation of the rate of nucleation and subsequent growth of the Au in the mixed reverse micelles induce drastic changes in the particle shape and structure. Here we demonstrate that control of the nucleation and growth kinetics of the Au in the mixed reverse micelles can be used to vary the shapes of the resulting particles from a nearly spherical morphology to cylinders, trigons and cubics. The characterization of the resultant particles, the effects of synthesis conditions (such as concentration of NaCl, addition of glycerol, and reaction temperature) on particle sizes, particle size distribution, and shape of particle formation have been investigated. This study will help us to understand the chemical control synthesis of crystal growth processes at the atomic level.     

混合反胶束的电导与微结构研究

反胶束是两亲分子在非极性溶剂中形成的一种有序组合体，在医药、化工、采油、胶束催化及酶催化等领域中有重要应用．与胶束溶液相比，人们对反胶束的形成与结构的了解至今仍不充分．特别是对于由混合表面活性剂形成的反胶束的研究几乎无人涉及．本文采用动态光散射、电导及荧光光谱等手段对阴离子表面活性剂AOT与非离子表面活性剂形成的混合反胶束进行了研究，旨在探讨利用表面活性剂的复配来调节和控制反胶束的结构和性能．亚实验部分二异辛基磺化琉璃酸钠（AOT，Sigma公司）；Brij30为含4个氧乙烯基（EO基）的十二碳醇（AcrosOrgani…     

阴离子与非离子表面活性剂复配体系反胶团的电导研究

在SDS/Tween60/正己醇/环己烷/水形成的反胶团复配体系中,电导率(κ)与水和表面活性剂的摩尔比(W0)关系曲线上存在最大值,随着复配体系中SDS的摩尔分数(xSDS)增大,最大增溶水量(W0,max)向W0值更大的方向移动.xSDS≤0.5时,随着xSDS的增大,W0,max所对应的电导率值增大;xSDS≥0.5时,其电导率值减小.在AOT/Tween60/环己烷/水体系中,出现了与SDS/Tween60/正己醇/正己烷/水体系类似的现象,但W0,max所对应的电导率值,随着xAOT的增大而增大,不会出现极大值,两者的差异主要是由于助表面活性剂醇的影响.在SDS/TritionX-100/正己醇/环己烷/水体系中也印证了该结论.     

STUDY ON PERCOLATION OF MIXED REVERSE MICELLES

The temperature-induced percolation behaviors of AOT reverse micelles in the presence of nonionic surfactants have been studied. The effects of water content, solvent and concentration of electrolyte in solubilized water have also been investigated. It was found that the percolation temperature of AOT reverse micelles was decreased by adding nonionic surfactants, and more pronounced effects were observed with the increase of EO chain length and content of nonionic surfactants. The increase of molecular volume of the solvent and the increase of concentration of the added NaCl electrolyte have shown assisting and resisting effects on the process, respectively. The apparent hydrodynamic diameter of droplets of different mixed reverse micelles has been measured using dynamic light scattering, by which the percolating mechanism of mixed reverse micelles was discussed in combination with the results obtained from conductivity measurements.     

Physicochemical investigation of the solubilization of ytterbium nitrate in AOT reverse micelles and liquid crystals

A wide investigation of the solubilization of the water-soluble salt Yb(NO₃)₃ in sodium bis(2-ethylhexyl)sulfosuccinate (AOT) reverse micelles and AOT liquid crystals has been carried out. After saturation of water/AOT/organic solvent w/o microemulsions with pure Yb(NO₃)₃, the Yb(NO₃)₃/AOT composites were prepared by complete evaporation under vacuum of the volatile components (water and organic solvent) of the salt-containing microemulsions. It was observed that these composites can be totally dissolved in pure n-heptane or CCl₄, allowing the solubilization of a noticeable amount of Yb(NO₃)₃ in quite dry apolar media. By UV–vis–NIR, FT-IR, and ¹H NMR spectroscopies, some information on the state of Yb(NO₃)₃ within AOT reverse micelles were acquired, whereas by small angle X-ray scattering (SAXS), it has been ascertained that Yb(NO₃)₃ is quite homogeneously distributed as very small clusters among the reverse micelles. An analysis of SAXS and wide-angle X-ray scattering spectra of Yb(NO₃)₃/AOT composites leads to the hypothesis that, also in these systems, Yb(NO₃)₃ is dispersed in the surfactant matrix as very small clusters.     

吨染料与反胶束体系中CdS的光敏电子转移

用ＡＯＴ／异辛烷／水反胶束体系制备出了不同尺寸大小的纳米ＣｄＳ,并以曙红（ＥＯ）和孟加拉玫瑰红（ＲＢ）为探针分子,研究了它们与硫化镉微粒间的光致电荷转移相互作用,用光照实验和ＥＳＲ技术研究了这些染料向ＣｄＳ的导带注入电子的过程并讨论了作用机理     

FT-IR Investigation of the State of Iron(III) Chloride Clusters Confined in AOT Reverse Micelles Dispersed in Carbon Tetrachloride

The state of the water-soluble salt iron(III) chloride in AOT reverse micelles dispersed in carbon tetrachloride has been investigated by FT-IR spectroscopy. Interestingly, while the entrapment of a lot of water-soluble inorganic salts in AOT reverse micelles requires preliminarily the presence of significant amounts of water within the micellar core, solubilization of FeCl₃ occurs without the need to add water in the micellar solution reaching the very high solubility value, expressed as the maximum salt-to-surfactant molar ratio, of 1.30. The analysis of the spectral features of the investigated samples leads to hypothesize that iron(III) chloride is confined within the reverse micellar core as small size melted clusters of ionic species arising from the reactions

THE EFFECTS OF MIXED MICELLES OF SURFACTANTS ON POLYMERIZATION OF ACRYLAMIDE

The polymerization of acrylamide in mixed micellar solutions of surfactants, initiated by NaHSO₃ has been studied at 20 and 3Q° C with time variable method of thermokinetics for 1. 5-order reaction. The results indicate that the mixed micellar systems of cationic or anionic with zwitterionic surfactants (SLS/ CTAB, SLS/ TTAB, SLS/ SDS) and cationic with nonionic surfactants (Brij 357sol; CTAB, Bri-J35/TTAB, Brij35/ DTAB) have catalytic effect on the polymerization in the order, at 20° C. SLS/ SDS SLS/ TTAB SLS/ CTAB Brij35/ CTAB at 30° C SLS/ SDS SLS/ TTAB≈ / CTAB Bri-j35/ DTAB= sBrij35/ TTAB as Brij35/ CTAB, while Brij35/ SDS mixed micellar system has inhibition. These effects are attributed to the effect of the Stern layer of mixed micelles on the step of initiator (HSOT) to form free radical.     

THE EFFECT OF MIXED MICELLES OF SURFACTANTS ON THE ALKALINE HYDROLYSIS OF ESTERS

The alkaline hydrolysis of aromatic and normal aliphatic acid esters have been studied at 25°C In mixed micellar solution of surfactants (Brij35—SDS, Brij35 — DTAB, Brij35—TTAB.Brij35-CTAB. Triton X—100 —CTAB, Triton X— 100 —SDS) with UV spectrophotometry and the method of thermokinetics The critical mice liar concentrations of the corresponding systems have also been measured with UV spectrophotometry in this paper. K_jnln micellar pseudo-phase has been calculated- The ratios of ki.to ki.for all mixed micellar systems Investigated are less than 1. The results indicate that these reactions are inhibited by the mixed micelles and the mixed micelles exhibit a greater effect of Inhibition on the reactions than those do In corresponding single ones. The reason for this is that the micropolarity of the compact Stern layer of mixed micelle is lower, and the micro viscidity Is higher. The Inhibition effect! also depend on the hydrophobic chain length of the surfactants and the hydrophobicity of the substrate.     

半导体纳米粒子在反胶束中的合成及其与芘分子间的跨相电子转移

本文在AOT/异辛烷反胶束中合成了CdS和ZnS半导体纳米粒子。粒子的荧光量子产率随胶束水含量的增大而减小。这可以归结为水含量增大导致胶粒表面Cd²⁺或Zn²⁺离子浓度降低,因为这两种离子在胶粒表面富集有利于形成硫空位,从而增大光生电子-空穴对的发光复合。研究发现,Ag⁺离子可以有效猝灭CdS和ZnS纳米粒子的荧光发射,该猝灭过程可以用Ag⁺离子在胶束中的Poisson分布来描述。以溶解在有机相中的pyrene作电子给体,在光激发下可以向CdS粒子注入电子,而和ZnS粒子间没有电荷转移发生,这可以解释为两种半导体的导带边相对于pyrene激发态氧化电位所处的位置不同。Cu²⁺或Ag⁺离子在ZnS颗粒表面吸附,可以形成Cu_xZn_1-xS或Ag_2xZn_1-xS复合粒子,降低ZnS粒子的导带位置,从而使之能够接受来自pyrene激发态的电子。实验结果证实了这种论点。     

INDUCTION OF CRYSTALLIZATION OF SPECIFIC CALCIUM OXALATE HYDRATES IN MICELLAR SOLUTIONS OF SURFACTANTS

ABSTRACT

The influence of octaethylene glycol mono-n-hexadecyl ether (C₁₆EO₈) and sodium dodecyl sulphate (SDS) on the crystallization of calcium oxalate from 0.3 mol dm^?3 sodium chloride solutions has been investigated. The critical micellar concentration (CMC) of C₁₆EO₈ in water and 0.3 mol dm^?3 NaCl was determined by surface tension measurements (CMC_H2O=CMC_NaCl = 7.2.10^?6 mol dm^?3). The kinetics of precipitation of calcium oxalate was followed by Coulter counter, and solid phases were characterized by polarized microscopy, thermal analysis and X-ray powder diffraction patterns. Under the precipitation conditions employed, the thermodynamically stable monohydrate, CaC₂O₄?H₂O (COM) was the predominant crystalline form. In the presence of micellar solutions of C₁₆EO₈ precipitation of this phase was facilitated as evidenced by higher initial precipitation rates and higher precipitate volume and number of particles, as compared to the controls. Micellar solutions of 50S retarded precipitation but induced crystallization of calcium oxalate dihydrate, CaC₂O₄?(2+×)H₂O (COD, x≤0.5). Thus at c(SDS>CMC the precipitates contained ≥85 mass % COD. The results are discussed in relation to previously reported data on the precipitation of calcium oxalate in the presence of dodecyl ammonium chloride     

THE EFFECT OF SLNGLE AND MIXED MICELLES OF SURFACTANTS ON POLYMERIZATION OF ACRYLAMIDE

Acrylamide is conveniendy polymerized in aqueous solution lo a water soluble polymer. The measurements of kinetic parameters of polymerization of acrylamide, in aqueous and micellar solution, have been earned out by conduction calorimeter. The polymerization is initiated by sodium sulfite and sulfite-persulfate redox system. The effect of initiator and monomer concentration as well as temperature and surfactants on polymerization rale constant has been investigated. The analog thermogram method has been employed to calculate the rate constants. The activation energy is calculated from Arrhenius relationship and molecular weights are determined by viscometry. Rate equations have been derived and reaction mechanism hove been suggested. The rate of reaction is found to increase with temperature and monomer concentration.     

Preparation and characterization of Pluronic/TPGS mixed micelles for solubilization of camptothecin

To increase the solubility and cytotoxicity of poorly soluble anticancer drug camptothecin (CPT), mixed micelles made of Pluronic P105 (P105) and d-alpha-tocopheryl polyethylene glycol 1,000 succinate (TPGS) were prepared. The interaction of Pluronic and TPGS was studied and critical micelle concentration (CMC) was used to evaluate the micellar stability towards dilution. Poorly soluble anticancer drug CPT was incorporated into the mixed micelles. The solubility of CPT by the mixed micelles was more than that of the free drug. The cytotoxicity of the CPT-loaded mixed micelles against MCF-7 cancer cell in vitro was remarkably higher than that of the free drug.     

丙烯酰胺-苯乙烯双亲嵌段共聚物水溶液的表面活性及增溶性

在微乳液介质中制备了系列的丙烯酰胺 (AM)与苯乙烯 (St)的双亲嵌段共聚物 (PAM b PSt) ,用紫外分光光度法测定了共聚物的组成 ,用乌氏粘度计测定了共聚物的特性粘数 [η],并用其相对表征共聚物的分子量大小 .重点研究了双亲嵌段共聚物 (PAM b PSt)疏水链段在水溶液中的缔合行为、共聚物的表面活性及其对有机物的增溶性能 ,考察了共聚物分子组成 (疏水链段含量 )与分子量对其表面活性与增溶性能的影响规律 .研究结果表明 ,由于疏水链段的憎水性 ,PAM b PSt的分子链在水溶液表面会形成表面吸附 ,从而降低水溶液的表面张力 ;而在水溶液中 ,在疏水相互作用下 ,PAM b PSt分子链中的苯乙烯疏水链段会形成分子间或分子内的胶束 ,烃类有机物可增溶其中 ;疏水链段含量越大 ,分子量越小 ,PAM b PSt的表面活性与增溶性能越强     

烷基磷（膦）酸萃取剂钠盐与非离子表面活性剂AEO_9混合体系胶团的形成和分子间的相互作用

本文研究了烷基磷（膦）酸萃取剂钠盐ＮａＥＨＥＨＰ，ＮａＤＴＭＰＰ，Ｎａ_２（ＭＥＨＰ）与非离子表面活性剂ＡＥＯ_９以不同比例复配后水溶液胶团的形成及分子间的相互作用，结果表明混合胶团的形成使ＣＭＣ大大降低。分子间在胶团中的相互作用强弱为：Ｎａ_２（ＭＥＨＰ）体系＞ＮａＤＴＭＰＰ体系＞ＮａＥＨＥＨＰ体系，分子间在表面层的吸引作用小于同体系分子间在胶团中的相互作用，这一结果有利于混合胶团的形成。     

HEXADECYLTRIMETHYLAMMONIUM BROMIDE + TETRADECYLTRIMETHYL-AMMONIUM BROMIDE MIXED MICELLES IN AQUEOUS GLYCOL OLIGOMERS

The conductances of hexadecyltrimethylammonium bromide (HTAB) + tetradecyltrimethylammonium bromide (TTAB) mixtures over the entire mole fraction range of HTAB (α_HTAB) were measured in pure water as well as in the presence of various aqueous ethylene glycol oligomers containing 5, 10 and 20 wt% of each additive in their respective binary mixtures at 30°C. From the conductivity data, the critical micellar concentration (cmc), degree of counter ion association (χ) and the standard free energy of transfer of the surfactant hydrocarbon chain from the medium to the micelle (ΔG^O _HP ) for HTAB and TTAB were computed. From the conductivity data of mixed surfactants systems, apart from cmc and χ, the regular solution theory parameters were also computed in order to explore the non-ideality in the mixed micelle formation in the presence of additives. The micellar parameters of both kind of surfactants and their mixtures show a significant dependence on the amount as well as on the number of repeating units of glycol oligomers. However, the non-ideality of mixed micelle formation remains unaffected in the presence of additives. These results have been explained on the basis of the medium effects of aqueous additive and it has been concluded that there are no significant interactions of glycol oligomers with the micelles of single and mixed surfactants.     

PHOTOPOLYMERIZATION IN THE MICELLAR SYSTEMS Ⅳ THE PHOTOSENSITIZATION EFFECTS OF THE BENZOPHENONES WITH DIFFERENT CHARGE IN IONIC MICELLAR SYSTEMS*

The photosensitization effects of the benzophenone derivatives having different charges, such as cationic BP(BP—CH_2—N~+ (C_2H_5)_3Br~-) (PKT-1), anionic BP(BP—COONa) and the neutral BP in the various ionic micellar systems were studied. From the photopolymerization of MMA initiated by the various BP/TEA in different micellar systems, the results obtained show that the polymerization rate is in the order of PKT-1>BP>BP—COONa in the SDS anionic micelle. On the contrary, the order changes to BP—COONa>BP>PKT-1 in the CTAB cationic mieelle, and to BP—COONa≈PKT-1>BP in the PKT-3 functional micelle. It is noteworthy that the PKT-1/SDS system is more efficient with its quantum yield more than 50 times compared with that of simple BP/H_2O system.     

PHASE BEHAVIOR IN SYSTEMS OF NONIONIC SURFACTANT/ WATER/ OIL AROUND THE HYDROPHILE-LIPOPHILE-BALANCE-TEMPERATURE (HLB-TEMPERATURE)

The phase diagram of the C₁₂H₂₅(OCH₂CH₂)₅OH/water/tetradecane system was studied around the critical solution temperatures of surfactant-water and surfactant-oil phases. Although the phase behavior is very complicated due to the formation of liquid crystalline phase, basic phase-changes around the three-phase region, consisted of a water, a surfactant and an oil phases, are the same as those in a short-chain nonionic surfactant system.     

羧甲基纤维素-十二烷基醇聚氧乙烯醚丙烯酸酯共聚物表面活性剂在水溶液中的胶束形态

采用动态激光光散射及环境扫描电镜研究了羧甲基纤维素型高分子表面活性剂在水溶液中的胶束形态 .结果表明 ,共聚物在水溶液中的形态完全不同于羧甲基纤维素分子 ,亲水疏水链段的引入 ,使共聚物分子聚集形成了以疏水链段为核心的棍状胶束结构 .高分子表面活性剂水溶液体系的归一化一级相关函数不符合单指数衰减 ,表明胶束形态的多分散性 .在 0 .0 0 5%～ 1 %浓度范围内 ,胶束粒子大小均分布在两个区域 ,随共聚物浓度增大 ,低粒径区保持在 3 0～ 1 0 0nm范围 ,为单分子区 ;而高粒径区随浓度增大移向更高值 ,表明多分子胶束不断长大 .     

Investigation on the basic hydrolysis of crystal violet in mixed reverse micelles formed with AOT and nonionic surfactants

 The kinetics and thermodynamics of the basic hydrolysis of crystal violet (CV) in mixed reverse micelles formed with anionic surfactant AOT and nonionic surfactants have been investigated. It was found that the mixed reverse micelles had inhibitory effects on CV hydrolysis compared with the normal aqueous solution, and the equilibrium constant K of the reaction in mixed reverse micellar systems is smaller than that in pure water. The influence of water content and surfactant composition in reverse micelles on the second-order rate constant k ₁ of the positive reaction, on the first-order rate constant k _-1 of the reverse reaction, as well as on the equilibrium constant K of the reaction has been studied, and the results obtained were interpreted in terms of the nature of surfactants and the properties of microenvironment where the reaction took place. Received: 24 October 1997 Accepted: 18 March 1998