非水反相微乳中NaCl纳米粒子的制备

在乙醇/Brij 30/十六烷反相微乳中利用无水NaAc与HCl反应制备了水可溶性晶态NaCl纳米粒子,平均粒径为 60 nm.与在甲酰胺/AOT/正庚烷反相微乳中制备的粒径约为1 μm的NaCl粒子进行比较,表明在特定条件下,非水微乳可以作为合成水可溶性纳米粒子的有效介质.     

甲苯对水/AOT/醇反相微乳液体系电导行为的影响

采用电导法研究了以二(2-乙基己基)琥珀酸酯磺酸钠(AOT)为表面活性剂、庚醇和癸醇分别与甲苯的混合溶剂为油相的反相微乳液体系在有无添加剂氯化钠时的电导行为。 结果表明,甲苯对水/AOT/癸醇体系电导渗滤有明显的抑制作用,而对水/AOT/庚醇体系没有影响;添加氯化钠对水/AOT/庚醇（癸醇）/甲苯体系的电导率基本无影响。     

AOT/H2O/油微乳液体系的浊度、密度和微观结构

建立了通过精密测量密度、折射率和浊度研究微乳液滴微观性质的方法,获得水与表面活性剂的摩尔比r分别为10.5和12的AOT/H2O/甲苯微乳液体系液滴的微观结构及相互作用参数,得到AOT分子的长度L=1.07 nm,用液滴间的相互作用讨论了相变温度与r的关系.用L=1.07 nm,通过密度测量得到AOT/H2O/甲苯和AOT/H2O/环己烷两个微乳液体系不同r值下液滴的微观结构参数,与文献报导的数据吻合得很好.发现在微乳液滴中的水的密度明显大于自由水的密度,并随溶剂变化,而AOT分子的构型不变.     

AOT/H_2O/油微乳液体系的浊度、密度和微观结构

建立了通过精密测量密度、折射率和浊度研究微乳液滴微观性质的方法,获得水与表面活性剂的摩尔比r分别为10.5和12的AOT/H2O/甲苯微乳液体系液滴的微观结构及相互作用参数,得到AOT分子的长度L=1.07nm,用液滴间的相互作用讨论了相变温度与r的关系.用L=1.07nm,通过密度测量得到AOT/H2O/甲苯和AOT/H2O/环己烷两个微乳液体系不同r值下液滴的微观结构参数,与文献报导的数据吻合得很好.发现在微乳液滴中的水的密度明显大于自由水的密度,并随溶剂变化,而AOT分子的构型不变.     

有机盐对水/AOT/醇反相微乳体系电导行为的影响

用二(2-乙基己基)琥珀酸酯磺酸钠(AOT)为表面活性剂研究了以正构醇(己醇、庚醇、辛醇、癸醇)为连续相的微乳体系的电导行为, 结果表明只有水/AOT/癸醇体系有水诱导的电导渗滤现象. 研究了有机盐(胆酸钠、水杨酸钠)及温度对电导行为的影响, 发现庚醇、辛醇体系电导率随胆酸钠浓度的增加而减小, 而癸醇体系电导率不受影响; 庚醇、癸醇体系的电导率随水杨酸钠浓度的增加而增大; 在5～40 ℃范围内lnσ(电导率的自然对数)与温度成很好的线性关系, 无论有机盐存在与否都没有温度诱导的渗滤现象. 根据Arrhenius-type公式估算了体系的电导活化能.     

乙腈非水体系中二甲基亚砜和咪唑的表面增强拉曼光谱研究

利用共焦显微拉曼系统研究了在乙腈非水体系中,二甲基亚砜(DMSO)与乙腈的竞争吸附,同时研究了咪唑在非水乙腈体系中的吸附情况.结果表明:在非水乙腈溶液中存在着明显的竞争吸附现象,咪唑和二甲基亚砜较乙腈分子在银电极上优先吸附,明显抑制了乙腈分子的吸附,随着电位负移,咪唑或二甲基亚砜逐渐脱附,更多的乙腈分子才得以接近电极表面并开始发生解离反应.     

反相微乳液中苯酚硝化反应选择性的研究

采用气相色谱内标法研究了苯酚在AOT/异辛烷/水、CTAB/正癸醇/异辛烷/水、DBSA/异辛烷/水3种反相微乳液中进行硝化反应的选择性;考察了表面活性剂种类、反应时间、反应温度以及反相微乳液的含水量等因素对反应选择性的影响.研究结果表明,苯酚在微乳液体系中的硝化反应具有明显的邻位选择性,阴离子表面活性剂DB-SA体系的邻位选择性最高,这与它同时具有微乳催化和酸催化作用有关.     

SDS/正癸醇/甘油与SDS/正癸醇/甲酰胺液晶结构

以极性有机物为溶剂制备展状液晶已经引起重视,但关于极性有机溶剂对层状液晶结构和稳定性影响的研究还很不够.我们曾以~2H NMR测量研究了以甲酰胺代替甘油为溶剂,对非水层状液晶SDS/C_(10)H_(21)OH/溶剂体系稳定性的影响.本文则以小角X射线衍射测量,研究以甲酰胺代替甘油后,对层状液晶SDS/C_(21)H_(21)OH/溶剂体系结构的影响。     

CTAB反相微乳液的稳定条件与纳米WO3的制备

以CTAB(十六烷基三甲基溴化铵)/正丁醇/正辛烷/钨酸钠水溶液构制反相微乳体系,通过测定体系电导率的方法确定相点并绘制反相微乳区拟三元相图。考察了该体系在不同条件下稳定存在的组成范围,选取实验最佳条件制备出纳米WO3。结果表明,表面活性剂与助表面活性剂的比、钨酸钠溶液的浓度对该反相微乳体系稳定区域的影响较大,当m(CTAB)∶m(正丁醇)=1∶2,钨酸钠浓度为0.05～0.08 g/mL时,体系有较大的反向微乳区,且当m(CTAB 正丁醇)∶m(正辛烷)=2∶3时,体系有最大溶水量;温度对该体系稳定区域的影响不大。在最适宜条件下,以0.08 g/mL的钨酸钠微乳液与盐酸微乳液,在40℃的水浴中反应7 h,制备出平均粒径约30 nm的WO3纳米粒子。     

磺化聚苯醚离聚体微乳化过程相反转的研究

以乙酰磺酸为磺化剂制备了磺化度为 3%～ 1 7%mol的磺化聚苯醚 (SPPO)并中和成盐 ,在一定的温度和搅拌速度下 ,加水将SPPO乳化成水包油的稳定水基微乳液。用乳化过程中的体系的电导率、粘度和表面张力的变化表征了乳化相反转过程。另外还研究了溶剂的极性和离子含量对SPPO溶液可乳化性和乳化过程的影响     

An example of how to use AOT reverse micelle interfaces to control a photoinduced intramolecular charge-transfer process

6-Propionyl-2-(N,N-dimethyl)aminonaphtahalene, PRODAN, is widely used as a fluorescent molecular probe due to its significant Stokes shift in polar solvents. It is an aromatic compound with intramolecular charge-transfer (ICT) states which can be particularly useful as sensors. In this work, we performed absorption, steady-state, time-resolved fluorescence (TRES), and time-resolved area normalized emission (TRANES) spectroscopies on PRODAN dissolved in nonaqueous reverse micelles. The reverse micelles are composed of polar solvents/sodium 1,4-bis-2-ethylhexylsulfosuccinate (AOT)/n-heptane. Sequestered polar solvents included ethylene glycol (EG), propylene glycol (PG), glycerol (GY), formamide (FA), dimethylformamide (DMF), and dimethylacetamide (DMA). The experiments were performed with varying surfactant concentrations at a fixed molar ratio W(S) = [polar solvent]/[AOT]. In every reverse micelle studied, the results show that PRODAN undergoes a partition process between the external solvent and the reverse micelle interface. The partition constants, K(p), are quantified from the changes in the PRODAN emission and/or absorption spectra with the surfactant concentration. The K(p) values depend strongly on the encapsulated polar solvent and correlate quite well with the AOT reverse micelle interface's zones where PRODAN can exist and emits. Thus, the partition toward the reverse micelle interface is strongly favored in DMF and DMA containing micelles where the PRODAN emission comes only from an ICT state. For GY/AOT reverse micelles, the K(p) value is the lowest and only emission from the local excited (LE) state is observed. On the other hand, for EG/AOT, PG/AOT, and water/AOT reverse micelles, the K(p) values are practically the same and emission from both states (LE and ICT) is simultaneously detected. We show here that it is possible to control the PRODAN state emission by simply changing the properties of the AOT reverse micelle interfaces by choosing the appropriate polar solvent to make the reverse micelle media. Indeed, we present experimental evidence with the answer to the long time question about from which state does PRODAN emit, a process that can be controlled using the unique reverse micelle interfaces properties.     

Intramolecular charge transfer reaction, polarity, and dielectric relaxation in AOT/water/heptane reverse micelles: pool size dependence

Intramolecular charge transfer (ICT) reaction in a newly synthesized molecule, of 4-(1-morpholenyl) benzonitrile (M6C), in AOT/water/heptane reverse micelles at different pool sizes has been studied by using steady-state and time-resolved fluorescence emission spectroscopy. The pool size dependences of the reaction equilibrium constant and reaction rate have been explained in terms of the average polarity of the confined solvent pools estimated from the fluorescence emission Stokes shift of a nonreactive probe, coumarin 153, dissolved in these microemulsions. The complex permittivity measurements in the frequency range 0.01相似文献   

Determination of water states and the structural parameters of W/O microemulsions

The states of water in sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/isooctane/water reverse(W/O) microemulsions system have been investigated by using Fourier transform infrared spectroscopy(FT-IR) technique. The broad peak obtained for hydroxy(O-H) of water has been resolved by least square curve-fitting. It has been observed that the water solubilized in microemul-sion droplets has four states, i.e. bound water with sulfo-group, free water, bound water with sodium counterion in the water pool of microemulsion droplets and a small amount of trapped water in the palisade layer of microemulsion droplets. The following have also been determined: the aggregation number (n), the radius of the water pool in the microemulsions(rw), the thickness of the bound water with sulfo-group(d1), the thickness of the bound water with sodium counterion(d2), the total thickness of the bound water (d) and the effective area of head groups of AOT(AAOT).     

Effect of the Media on the Quantum Yield of Singlet Oxygen (O2(1Δg)) Production by 9H‐Fluoren‐9‐one: Microheterogeneous Systems

The quantum yield (Φ_Δ) of singlet oxygen (O₂(¹Δ_g) production by 9H‐fluoren‐9‐one (FLU) is very sensitive to the nature of the solvent (0.02 in a highly polar and protic solvent, such as MeOH, to 1.0 in apolar solvents). This high sensitivity has been used for probing the interaction of FLU with micellar media and microemulsions based on anionic (sodium dodecyl sulfate, SDS; bis‐(2‐ethylhexyl)sodium sulfosuccinate, AOT), cationic (cetyltrimethylammonium chloride, CTAC) and nonionic (Triton X‐100, TX) surfactants. Values of Φ_Δ of FLU vary in a wide range (0.05–1.0) in both microheterogeneous media and neat solvent, and provide information on the microenvironment of FLU, i.e., on its localization within organized media. In ionic and nonionic micellar media, as well as in four‐component microemulsions, FLU is, to various extents, exposed to solvation by the polar and protic components of the microheterogeneous systems (water and/or butan‐1‐ol) in the micellar interfacial region (Φ_Δ=0.05–0.30). In contrast, in AOT reverse micelles (consisting of AOT as surfactant, cyclohexane as hydrophobic component, and water), FLU is located in the hydrophobic continuous pseudophase, and is totally separated from the micellar water pools (Φ_Δ≈1.0).     

Dynamics of solvent and rotational relaxation of glycerol in the nanocavity of reverse micelles

The dynamics of solvent and rotational relaxation of Coumarin 480 and Coumarin 490 in glycerol containing bis-2-ethyl hexyl sulfosuccinate sodium salt (AOT) reverse micelles have been investigated with steady-state and time-resolved fluorescence spectroscopy. We observed slower solvent relaxation of glycerol confined in the nanocavity of AOT reverse micelles compared to that in pure glycerol. However, the slowing down in the solvation time on going from neat glycerol to glycerol confined reverse micelles is not comparable to that on going from pure water or acetonitrile to water or acetonitrile confined AOT reverse micellar aggregates. While solvent relaxation times were found to decrease with increasing glycerol content in the reverse micellar pool, rotational relaxation times were found to increase with increase in glycerol content.     

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.     

The use of acridine orange base (AOB) as molecular probe to characterize nonaqueous AOT reverse micelles

The behavior of acridine orange base (AOB) in nonaqueous reverse micelles composed of n-heptane/AOT/polar solvent has been performed. Ethylene glycol (EG), propylene glycol (PG), glycerol (GY), formamide (FA), dimethylformamide (DMF), and dimethylacetamide (DMA) were employed as water substitutes. The studies were performed by static and time-resolved emission spectroscopy. Thus, the distribution of AOB between the two pseudophases of the aggregates was quantified by measuring the partition constants from emission spectra at different surfactant concentration. Similar values to those obtained by means of absorption spectroscopy were obtained. This match is indicating that AOB is not experiencing partition during the lifetime of the excited state. Partitioning to the micelles is strongly favored in micelles containing hydrogen-bond donor (HBD) solvents rather than non-HBD solvents. Variations of fluorescence lifetimes with AOT concentration confirm these results. By the solvatochromic behavior of AOB in the different systems it is shown that the microenvironment at the interface is distinct from that of the bulk polar solvent, indicating that the probe senses no "free" solvent. The steady state anisotropy (r) was measured for EG/AOT/n-heptane and DMF/AOT/n-heptane systems as representatives for HBD and non-HBD polar solvents, respectively. The value of r is higher in the micelles containing EG than that obtained with DMF, and increases with AOT concentration. This is explained as due to highly structured polar solvents in the inner core. EG is interacting with the polar heads of AOT through hydrogen-bond interaction, while DMF can only interact with the Na+ counterions. This is confirmed by the time-resolved emission spectra (TRES) of the probe in the micellar systems, in comparison with the bulk solvents.     

Excited-state proton transfer of 2-(2'-pyridyl)benzimidazole in microemulsions: selective enhancement and slow dynamics in aerosol OT reverse micelles with an aqueous core

Excited-state proton transfer (ESPT) of 2-(2'-pyridyl)benzimidazole (2PBI) in reverse micelles has been studied by steady-state and time-resolved fluorescence spectroscopy. The nanometer sized water pool in the n-heptane/Aerosol OT (AOT)/water microemulsion is found to promote tautomer emission of this probe, as is evident from the emergence of a Stokes shifted band at 450 nm at the expense of the normal emission band on increasing the water content of the system. In the nonaquous microemulsion with a methanol core, the normal emission is quenched but no tautomer emission is obtained. With an acetonitrile core, there is no change in emission properties. Similarly, there is no evidence of ESPT in Triton X-100 reverse micelles. This indicates the requirement of ESPT to occur in microheterogeneous media; the medium should be a ternary system comprised of water and a hydrophobic phase separated by a negatively charged interface. In the microemulsions with an aqueous core, the fluorescence decays of 2PBI at the red end exhibit rise times of 0.8 ns and the time-resolved area-normalized emission spectra (TRANES) exhibit an isoemissive point, indicating slow dynamics of the two-state ESPT of 2PBI in aqueous AOT reverse micelles. The origin of the selective enhancement in AOT microemulsions as well as the slow dynamics is explored using fluorescence spectroscopic techniques, with support from quantum chemical calculation.     

The Conductance Percolation and Droplets Dimension of AOT in Alkanol Systems

The conductance behaviors of AOT in alkanol (hexanol, heptanol, octanol, and decanol) reverse microemulsions have been investigated. The percolation phenomenon induced by water is observed in the water/AOT/decanol system at 15°C and 30°C, and the water/AOT/octanol system at 15°C. The percolation phenomenon of water/AOT/alkanol systems is discussed from the interaction between the hydroxy group of alkanol and the polar group of AOT, droplets diffusion coefficient, and the rate constant for droplets collision. The droplets size and diffusion coefficient of the water/AOT/alkanol systems have also been studied by modifying the water concentration. The results show that hydrodynamic diameter of droplets decreases and diffusion coefficient increases with the increasing of water content, which may be explained by the polarity of alkanol phase.     

Vibrational relaxation of azide in formamide reverse micelles

Static and ultrafast infrared spectroscopy have been used to measure absorption spectra and vibrational energy relaxation (VER) times for the antisymmetric stretching vibrational band of azide, N(3)(-), in formamide-containing reverse micelles (RMs). RMs were formed in n-heptane using the surfactant AOT, sodium bis(2-ethylhexyl) sulfosuccinate. The VER times were found to be significantly longer than in bulk formamide. The VER times became longer as the molar ratio of formamide to AOT, omega(F), was decreased. Decreasing omega(F) also resulted in substantial blue shifts of the azide static absorption band compared to the frequency in bulk formamide. The omega(F) dependent studies are consistent with expected size trends, where a larger RM results in more bulklike polar solvent and faster VER rates. These results are in contrast to aqueous AOT RMs where VER times were indistinguishable from those in the bulk and the static spectral shifts were much smaller. The differences between the static and dynamic behavior in aqueous and formamide RMs are related to differences in structural changes upon confinement in RMs.