Publications (22)135.74 Total impact

  • [Show abstract] [Hide abstract] ABSTRACT: Emulsions composed of an ionic liquid (IL) 3-methyl-1-octylimidazolium hexafluorophosphate, water, and surfactant TX-100 (poly(ethylene glycol)-tert-octylphenyl) were studied by laser confocal scanning microscopy, stability determination and electrical conductivity. Multiple water-in-ionic liquid-in-water (W/IL/W) emulsions were formed around water volume fractions ~0.70. Further studies showed that the W/IL/W multiple emulsions were formed through an inversion between water-in-IL emulsion and IL-in-water emulsion.
    No preview · Article · Dec 2011 · Journal of Colloid and Interface Science
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    [Show abstract] [Hide abstract] ABSTRACT: High-internal-ionic liquid-phase emulsions were formed for the first time. The novel emulsions are very stable and do not involve any volatile organic solvent. They have great potential of applications in different fields, such as material synthesis, extraction, encapsulation, and chemical reactions.
    Preview · Article · Dec 2011 · Chemical Communications
  • [Show abstract] [Hide abstract] ABSTRACT: Tailor-made emulsion: A CO(2) -in-ionic-liquid microemulsion was produced for the first time. The CO(2) -swollen micelles are "tunable" because the micellar size can be easily adjusted by changing the pressure of CO(2) . The microemulsion has potential applications in materials synthesis, chemical reactions, and extraction.
    No preview · Article · Oct 2011 · Angewandte Chemie International Edition
  • Wei Li · Jianling Zhang · Buxing Han · Yueju Zhao
    [Show abstract] [Hide abstract] ABSTRACT: Herein we investigated the effects of six hydrocarbon gases (methane, ethane, propane, ethylene, propylene and isobutene) on mixed cationic–anionic surfactant solutions by phase behavior observation, turbidity, conductivity, and fluorescence spectra. It was found that all these gases could enhance the stability of vesicles formed in the mixed surfactant solutions. The pressure for the stable vesicle formation is decreased with the increasing gas molecular chain length. The possible mechanism for the enhanced vesicle stability by compressed gases was discussed.
    No preview · Article · Oct 2011 · RSC Advances
  • [Show abstract] [Hide abstract] ABSTRACT: CO(2) can be used to separate surfactant and organic solvent completely in various surfactant/solvent solutions without contaminating the surfactants and solvents. We believe that the simple, efficient, and greener method has wide applications.
    No preview · Article · May 2011 · Chemical Communications
  • [Show abstract] [Hide abstract] ABSTRACT: 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.
    No preview · Article · Apr 2011 · Chemistry - A European Journal
  • Jianling Zhang · Buxing Han · Yueju Zhao · Wei Li · Yuanhui Liu
    [Show abstract] [Hide abstract] ABSTRACT: Herein it was found that CO(2) could trigger an O/W to W/O emulsion inversion via a W/O/W nanoemulsion. In comparison with the conventionally used liquid or solid additives, the unusual advantage of this method is that the emulsion morphologies can be switched reversibly by the control of CO(2) pressure. Besides, CO(2) can be easily removed by depressurization and thus no extra separation process is needed, and CO(2) can be recycled. Furthermore, other lipophilic gases of ethylene, propylene and isobutane can also induce the O/W to W/O emulsion inversion. A possible mechanism for the gas-triggered emulsion inversion was proposed.
    No preview · Article · Feb 2011 · Physical Chemistry Chemical Physics
  • [Show abstract] [Hide abstract] ABSTRACT: Pores and pores: Metal-organic framework (MOF) nanospheres with long-range ordered mesopores, the walls of which are composed of microporous structure units, were synthesized in binary solvent systems of ionic liquid and supercritical CO2. The MOF nanostructure has many potential applications and its preparation could easily be applied to MOFs with other metal ions and ligands.
    No preview · Article · Jan 2011 · Angewandte Chemie International Edition
  • [Show abstract] [Hide abstract] ABSTRACT: A simple and efficient route for the immobilization of noble metal nanoparticles onto metal–organic framework (MOF) has been designed in this work. The Ru/MOF nanocomposites were prepared using RuCl3·3H2O as a precursor in supercritical CO2-methanol solution at 200 °C. The as-synthesized Ru/MOF composite presented a high catalytic performance for the hydrogenation of cyclohexene and benzene. There was almost no activity loss after the catalyst was reused five times. The intermolecular interactions between the MOF and Runanoparticles were investigated by X-ray photoelectron spectra and FT-IR spectra. It was shown that the carboxylate groups of MOF were coordinated to Ru. The formation mechanism of the Ru/MOF nanocomposites in supercritical CO2-methanol solution through an inorganic reaction route was discussed. This method can be easily applied to the synthesis of other MOF-supported metal nanoparticles.
    No preview · Article · Jan 2011 · Green Chemistry
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    [Show abstract] [Hide abstract] ABSTRACT: The effect of CO2 on the properties of water/poly(oxyethylene)iso-octylphenyl ether (TX-100)/isooctane emulsions was investigated by direct observation, small angle X-ray scattering (SAXS), and UV-vis spectroscopy at 303.2 K in the pressure range 0–5 MPa. It was demonstrated that the droplet size of the emulsion was sensitive to the pressure of CO2, and the droplet size can be tuned in a wide range from the micron to the nanometre scale. When the CO2 pressure was 3.90 MPa, the droplet size reached a minimum value of 92 nm. To demonstrate the utilization of the CO2-responsive water/TX-100/isooctane emulsion, gold particles were synthesized using HAuCl4 as a gold precursor and TX-100 as a reducing reagent. It was shown that gold particles with different morphologies, such as nanowires, nanorods, and polyhedral nanocrystals could be synthesized by controlling the pressure of CO2.
    Full-text · Article · Nov 2010 · Soft Matter
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    [Show abstract] [Hide abstract] ABSTRACT: Here we found that CO(2) has high solubility in low-cost hydrocarbon surfactant liquids.
    Preview · Article · Nov 2010 · Chemical Communications
  • [Show abstract] [Hide abstract] ABSTRACT: The cetyltrimethylammonium bromide (CTAB)/water/heptane emulsion system with different CO(2) pressure has been studied. The phase behavior investigation shows the nanoemulsion can be formed at suitable pressure range. The generalized indirect Fourier transformation (GIFT) analysis of the small-angle X-ray scattering (SAXS) data has drawn a clear picture of the structural information of the nanoemulsion, which reveals that the droplet of emulsion has a double structure with both the outer and inner droplet size in nanometre range. Furthermore, the investigation of the heptane/CTAB/water/CO(2) emulsion system by using electrical conductivity confirms the emulsion type transforms from O/W to W/O/W. In addition, the effect of different CTAB concentration on the nanoemulsion formation has been studied. It is found that enough CTAB concentration is necessary for the inclusion of continuous water into oil droplets. We also explored the application of the W/O/W double nanoemulsion in material synthesis. Interestingly, the hollow silica spheres with double shells were obtained in this CO(2)-induced double nanoemulsion.
    No preview · Article · Oct 2010 · Physical Chemistry Chemical Physics
  • Yueju Zhao · Jianling Zhang · Buxing Han · Suqin Hu · Wei Li
    [Show abstract] [Hide abstract] ABSTRACT: The epoxidation of styrene in the cetyltrimethylammonium bromide (CTAB)/H2O/heptane/styrene/H2O2 emulsion system was investigated in the presence of compressed CO2. It was found that by controlling the CO2 pressure, the emulsion droplets can be changed in a wide range from micron to nanometre size; accordingly, the conversion was enhanced significantly with the reduced droplet size. At 5.27 MPa, the conversion in the emulsion (with droplet size of 39.5 nm) could be about 10 times higher than that in a surfactant-free system at the same pressure. The effects of other experimental conditions of CTAB concentration, reaction time, styrene concentration, amounts of H2O2, and alkalinity on the efficiency of the epoxidation were also studied, and a possible mechanism for the enhanced reaction efficiency with reduced droplet size was presented. This process has some unique advantages. For example, the reactant conversion can be easily tuned by controlling the pressure of CO2; CO2 can be used as bicarbonate source and no additional catalyst was used; CO2 can be easily removed by depressurization; the separation for the product is simple. It is believed that the CO2-tuned emulsions can be easily applied to many other chemical reactions.
    No preview · Article · Mar 2010 · Green Chemistry
  • [Show abstract] [Hide abstract] ABSTRACT: The effect of CO(2) on the microstructure of L-alpha-phosphatidylcholine (lecithin) reverse micelles was studied. The small-angle X-ray scattering (SAXS) results show that CO(2) could induce a cylindrical-to-spherical micellar shape transformation. Fourier transform infrared (FT-IR) and UV-vis techniques were also utilized to investigate intermolecular interactions and micropolarity in the reverse micelles at different CO(2) pressures. The reduction of the degree of hydrogen bonding between surfactant headgroups and water with added CO(2) was found to be the main reason for the micellar shape transformation. In the absence of CO(2), the hydrogen bonding between water and P=O of lecithin forms a linking bridge in the interfacial layer. Therefore, the free movement of the polar head of lecithin is limited and the cylindrical reverse micelles are formed. Upon adding CO(2) to the reverse micelles, the hydrogen bonds between lecithin and water in reverse micelles are destroyed, which is favorable to forming spherical micelles. Moreover, the CO(2)-combined reverse micelles were utilized in the synthesis of silica particles. Rodlike silica nanoparticles were obtained in the absence of CO(2), and ellipsoidal and spherical mesoporous silica particles were formed in the presence of CO(2). This method of tuning micellar shape has many advantages compared to traditional methods.
    No preview · Article · Mar 2010 · Langmuir
  • [Show abstract] [Hide abstract] ABSTRACT: 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 CO(2) 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 CO(2) could induce the MVT in the surfactant system, and the vesicles returned to the micelles simply by depressurization; that is, CO(2) 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.
    No preview · Article · Jan 2010 · Chemistry - A European Journal
  • [Show abstract] [Hide abstract] ABSTRACT: Monodisperse hollow silica spheres of uniform size and ordered mesoporous shells have been successfully fabricated in water/heptane/CTAB nanoemulsions induced by compressed CO(2).
    No preview · Article · Jun 2009 · Chemical Communications
  • [Show abstract] [Hide abstract] ABSTRACT: The effect of ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF6) on the micelles formed from cationic alkyl polyglycoside (CAPG), which is derived from renewable material, was studied by solubilization determination, UV–vis spectra, electrical conductivity and Freeze-fracture electron microscopy (FFEM). It was found that addition of small amount of the IL could enlarge the micelles significantly, which enhances the solubilization ability of the micelles considerably. The application of the IL-enlarged CAPG micelles in synthesis of nanomaterial and extraction of cholesterol was studied. It demonstrated that hollow silica spheres were formed in the presence of the IL. In addition, the extraction efficiency for cholesterol using CAPG micelles could be enhanced considerably by the addition of IL.
    No preview · Article · Mar 2009 · Colloids and Surfaces A Physicochemical and Engineering Aspects
  • [Show abstract] [Hide abstract] ABSTRACT: In this work, we studied the effect of compressed CO2 on the stability of vesicles formed in a dodecyltrimethylammonium bromide (DTAB)/sodium dodecyl sulfate (SDS) mixed surfactant system by combination of phase behavior and turbidity study, and UV-vis and fluorescence techniques. It was discovered that compressed CO2 could enhance the stability of vesicles significantly. This new and effective method to stabilize vesicles has some unique advantages over conventional methods. For example, the size and stability of the vesicles can be easily controlled by CO2 pressure; the method is greener because CO2 is a green reagent and it can be released completely after depressurization, which simplifies postseparation processes in applications. The main reason for CO2 to stabilize the vesicles is that CO2 molecules can insert into the hydrophobic bilayer region to enhance the rigidity of the vesicle film and reduce the size of the vesicles, which is different from that of conventional cosolvents (e.g., alcohols) used to stabilize vesicles. On the basis of this discovery, we developed a method to prepare hollow silica spheres using tetraethoxysilane as the precursor and CO2-stabilized vesicles as the template, in which CO2 acts as both the stabilizer of the vesicular template and the catalyst for the hydrolysis reaction of the precursor, and other cosolvents and catalysts are not required. Besides, the size of the silica hollow spheres prepared can be controlled by the pressure of CO2.
    No preview · Article · Jan 2009 · Langmuir
  • Jianling Zhang · Buxing Han · Wei Li · Yueju Zhao · Minqiang Hou
    [Show abstract] [Hide abstract] ABSTRACT: (Figure Presented) Changing under pressure: Compressed CO2 can switch the surfactant sodium bis-2-ethylhexylsulfosuccinate/water system between a lamellar liquid crystal (Lα) phase and a micellar solution (L1) reversibly at ambient temperature. Applications of this simple, clean, and energy-efficient process in material synthesis are explored, along with a possible mechanism for the phase-transition phenomenon.
    No preview · Article · Dec 2008 · Angewandte Chemie International Edition
  • [Show abstract] [Hide abstract] ABSTRACT: 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.
    No preview · Article · Sep 2008 · Langmuir