| A microemulsion is defined as an optically isotropic, transparent, and thermodynamically stable dispersion formed by two or more immiscible liquids containing appropriate amounts of surfactants and possibly cosurfactants. Generally, it is believed that surfactants are necessary components for stabilizing a microemulsion. However, Smith et al. in1977reported an oil-continuous (W/O) microemulsion composed of hexane,2-propanol and water, which showed the traditional surfactant is not the necessary component for microemulsion. And this ternary system could be considered as a surfactant-free (or detergentless) microemulsion (denoted as SFME) and have attracted much attention. It is known that there are three kinds of microstructures in traditional microemulsions, that is, water-in-oil, bicontinuous and oil-in-water. But so far, the SFMEs reported were W/O, and water is used as the polar component. It is a interesting question that if BC and O/W microstructures exist in SFMEs. Recently, room tempreture ionic liquids (IL) have been widely studied, especially as green solvents to prepare microemulsions. Whether it can be used to prepare SFMEs or not is a meaningful subject for research. And it is also necessary to explore the possibilities of synthesis nanomaterials in SFMEs, which have matured in traditional microemulsions.In this paper, the phase behavior of a ternary system consisting of1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4), a hydrophilic ionic liquid (IL), toluene and double-solvent ethanol (which can be dissolved in both polar phase and non-polar phase) was investigated, and its microstructures were characterized. TiO2nanoparticles were prepared using IL-SFMEs as microreactors, and the photcatalysis activity of products for organic dyestuff were also studied in order to gain more insight about SFMEs and provide evidences for the SFME application in preparing nanomaterials.The main research contents and conclusions are summarized as follow:1. The phase behavior of bmimBF4/ethanol/toluene was investigated. A single-phase microemulsion region and a multiphase region were observed in the ternary phase diagram, showing that IL can be used as the polar phase to prepare nonaqueous SFMEs.2. The microstructures and the structural transitions of the microemulsion system were examined by cyclic voltammetry and electrical conductivity techniques, respectively. It was found that the microemulsion system could present three types, that is, IL-in-toluene (IL/O), bicontinuous (BC), and toluene-in-IL (O/IL), similar to traditional surfactant-based microemulsion systems. The three microstructures of the microemulsion system were further confirmed by freeze-fracture electron microscopy (FF-TEM) observations. According to these results, three subregions were identified in the single-phase microemulsion region.3. The polarity and the solubility of mineral salts of bmimBF4domains in the IL/O microemulsion were investigated by UV-visible spectroscopy using methyl orange and Ni(NO3)2as probes, respectively. The results showed that the polarity was lower than that of bulk bmimBF4, and increased with increasing bmimBF4content at a constant toluene/ethanol ratio. The bmimBF4domains exhibited good solubility for common inorganic salts.4. TiO2nonaparticles were synthesized in O/IL and IL/O SFMEs of bmimBF4, toluene and ethanol using tetrabutyl titanate as titanium source. Both the types of SFMEs and the methods of preparation have obvious influence on the morphologies of nonaparticles, and TiO2hollow spheres can be obtainted through single-microemulison technique in O/IL SFMEs while the TiO2nonaparticles synthesized by double-microemulisons method were solid spheres. The pecific surface area of TiO2hollow spheres were found to be44.89m2·g-1. The effect of calcined temperature on the crystal structure of TiO2nonaparticles was investigated. Results showed that the samples were amorphous without calcining, and became anatase when calcined in500℃, and finally transformed to rutile in800℃.5. The photcatalysis activity of the TiO2nanoparticles was studied using methylene blue, rhodamine B and methyl orange as the dye models, and the results showed that they have good properties in photocatalytic degradation.The main innovation spots of this thesis follow:1. Nonaqueous IL-SFME was prepared using1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4), a hydrophilic ionic liquid (IL) as the polar phase, which is the first report at present.2. Except IL/O microstucture which has been reported, BC and O/IL were also found in the SFMEs, and these results deepen the understanding of SFMEs.3. Anatase TiO2hollow spheres were synthesized in the O/IL SFMEs, which have a good behavior in photocatalytic degradation for organic dyestuff, showing that SFMEs have high application value in preparing inorganic material. |
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