Assembly Of Au Janus Particles

Pickering emulsion is defined as the emulsion with the solid particles instead of the traditional surfactant as emulsifier. Pickering emulsion consists of solid particles, the aqueous phase and the oil phase. Compared with the traditional types of emulsion, Pickering emulsion has lots of advantages such as low emulsifier dosage, low toxicity and no pollution. Pickering emulsion has a good development prospect in cosmetic, food, medicine and other fields. Solid particle used to stabilize the Pickering emulsion is mainly clay, kaolin, SiO2 and so on. Recently, some novel solid particles emulsifier such as polymer microspheres, protein molecules and Janus particles were found and studied to stabilize the Pickering emulsion. Janus particles have a good application value because of the asymmetry of structure and the variety of composition. An application of Janus particles is used as a surfactant to stabilize emulsion. But the Janus particles must be modified by different groups, and have the characteristics of the amphiphilic.Au-Fe3O4 Janus particles were prepared in this paper. And high resolution electron microscopy was used to characterize the morphology. The three-phase contact angle of Au-Fe3O4 particles was obtained through the calculation of the water-air contact angle and the air-water contact angle. In addation, the properties of Au-Fe3O4 Janus particles used as emulsifier to stabilize Pickering emulsion were studied.On the surface of the Au-Fe3O4 Janus particles, the dopamine hydrochloride, CmPEG, twelve and eighteen thiol mercaptan were respectively used to modify the Janus particles. Accordingly, CmPED-DA-JP nanoparticles, CmPEG-DA-JP-ODT nanoparticles and CmPEG-DA-JP-DDT nanoparticles were prepared successfully. Besides, the performance of these nanoparticles was characterized through the infrared spectroscopy, thermogravimetric analysis method.The modified nanoparticles were used as emulsifier to stabilize the Pickering emulsion. The effect of solid particle concentration, oil-water ratio, the first dispersion medium, oil phase type on the stability of Pickering emulsion were studied respectively. The larger the solid particle concentration grow, thes maller the obtained emulsion droplets become. When the oil-water ratio of the system was increased, the emulsion was still an oil in water emulsion without the occurrence of phase inversion. When the hydrophilic solid particles were dispersed in the water phase, stable Pickering emulsion was obtained. On the contrary, stable Pickering emulsion would not obtained. The dipole moment of different oil plays an important role in the formation of emulsion. Compared with the polar solvent, non polarity solvent was easier to prepare the stable Pickering emulsion.