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In the present study, astaxanthin was microencapsulated in a biodegradable material, calcium alginate, using a modified emulsion technology developed at our laboratory. The modified emulsion method involves the reaction between a sodium alginate emulsion and a calcium chloride emulsion. After mixing these emulsions, Ca2+ penetrates two oil-water layers to combine −COO-, and microparticles are formed with narrow size distribution and good dispersion due to the mild reaction speed. The microencapsulated astaxanthin showed much higher storage stability and antioxidant activity than the non-encapsulated astaxanthin. Cytostatic activity was preliminarily evaluated on adipose-derived stem cells, the microencapsulated astaxanthin showed significant cytostatic activity due to the improved solubility of astaxanthin caused by the good biocompatibility of calcium alginate. Characterization confirmed the existence of microparticles with high encapsulation efficiency (more than 85 %), uniform size distribution (1.61 µm), and sustained astaxanthin release, suggesting the prepared microparticles by the modified emulsion method have great potential in pharmaceutical, food, and cosmetic industries. [ABSTRACT FROM AUTHOR]

We have investigated the formation and evolution of zinc oxalate particles in internal aqueous droplets and their effects of emulsion interface properties. The formation of particles follows an aggregation-controlled mechanism that depends on the size of droplets and surfactant. The size of droplets determines the final shape of the particles by affecting the supersaturation ratio to form rod-like and sheet-like particles. The surfactant adsorbed on the particles changes the wettability, leading to the aggregation of the primary particles at the internal water-oil interface. Moreover, the adsorption can cause a higher level of impurity and defects in as-synthesized particles. This effect could be directly employed to fabricate heterojunction rectifier. [ABSTRACT FROM AUTHOR]

The water solubilization capacity (W0) of microemulsion system determines its physicochemical properties and interior structures. In this study, the effects of different kinds of additives such as inorganic salt, nonaqueous polar solvent, organic salt, amino acid, and polyethylene glycols (PEG series) on the water solubilization behavior of heptane/hexanol/TritonX-100/water microemulsion system have been studied in detail. The influence mechanism of every additive on W0 has also been proposed and discussed. Furthermore, the droplet size distribution and the interaction among the droplets have been investigated by dynamic light scattering technique with the presence of additives. The result shows that the hydrodynamic diameter of microemulsion droplet and the attractive interaction between the droplets increase with the increase of the water content and the additive concentration. This work presents a facile method to adjust the structure parameters and the interface strength of microemulsion system by adding additive to the system, and to direct the applications of microemulsion system in nanomaterials preparation and drug controlled release. [ABSTRACT FROM AUTHOR]

Abstract: The validity of percolation theories on TritonX-100/heptane/alkanol/water W/O (water-in-oil) microemulsion has been investigated based on conductivity analysis. The experiment results have proved that the microemulsion follows both Bernasconi–Weismann (BW) and effective medium theory with dipole–dipole interaction (EMTDD, clusters) theories in the water content range from W 0 =1 to W 0 =7. The results here are different from the reported microemulsions with CTAB, AOT or SDS as ionic surfactant and alkanols as cosurfactants, and those microemulsions always follow effective medium theory (EMT) perfectly. This suggests that nonspherical surfactant aggregates and droplet clusters exist in the microemulsion solution due to the dipolar interaction between the dispersed droplets. The size of water pool, the hydrodynamic diameter of droplet, and the number of surfactant and cosurfactant per droplet have been evaluated according to the two validated theories. The dynamic state and the calculated size distribution of droplets are agreed with the results detected by dynamic light scattering technique. The research has indicated that the percolation theories are also adaptable to nonionic surfactant microemulsions with low water content and the structure parameters of droplets can be calculated by the effective theories. [Copyright &y& Elsevier]

Abstract: ZnO nanostructures with different morphologies and optical properties were prepared by a simple microemulsion process, and PEG400 was used as a directing agent. The samples were characterized by TEM, XRD, FTIR, and TG-DTA analysis. The XRD spectra indicate that the ZnO crystal has a hexagonal wurtzite structure. Needle-like, columnar, and spherical ZnO samples were synthesized respectively with the increase of PEG400 concentration in Zn(NO3)2 solution. TEM images and thermogravimetric analysis reveal that the microemulsion interface and the PEG400 agent have a synergistic effect on the morphology and crystalline size transition of ZnO nanostructures. The optical properties of the samples were investigated by measuring the UV–Vis absorbance spectra at room temperature. All the samples exhibit strong UV absorption at around 365 nm. ZnO products with band gap energies at 3.06, 3.02, 2.95, and 2.85 eV were obtained with 0, 12.5, 25.0, and 50.0% of PEG400 in Zn(NO3)2 solution, respectively. The formation mechanism of the ZnO nanostructures was proposed and discussed in detail. The synergistic control of the microemulsion interface and the agent on the growth of crystal nuclei reported here provides an alternative approach for preparation of other well-defined nanostructures. [Copyright &y& Elsevier]

Abstract: Freeze/thaw treatment has been widely investigated for phase separation of oil-in-water (O/W) emulsions. However, it is a new application for destroying the inverted emulsions, water-in-oil (W/O) emulsions. In this study, freeze/thaw treatment was used to break the W/O emulsions with loosely packed droplets that were produced from the oils generally adopted as membrane phase in emulsion liquid membrane (ELM) process. The effects of emulsion system parameters and freezing conditions on demulsification performance were investigated. A near linear relationship was observed between demulsification performance and water content (30–65%). Demulsification performance greatly increased with the increase of droplet size (2.7–7.3μm), while it was slightly affected by oil type. Four freezing methods were employed including freezing in refrigerator, cryogenic bath, dry ice and liquid nitrogen. The best freezing method for water removal was freezing in cryogenic or dry ice, and its efficiency was over 70% for all experimental systems with 60% water content regardless of droplet size and oil phase type. Furthermore, microscopic process of demulsification was monitored using optical microscope and the coalescence of droplets was simulated. From the experiments, the gradual demulsification process induced by freeze/thaw was proven and a collision mechanism was proposed. Meanwhile, the volume expansion of water turning to ice and interfacial tension of oil–water interface were determined as main driving forces of demulsification. The proposed mechanism and driving forces can explain the influences of various parameters on demulsification performance well. [Copyright &y& Elsevier]