Preparation Of Functionalized SiO₂ Janus Particles Based On Emulsion Template Method

Janus colloidal particles with anisotropy and excellent functional integration properties have broad application prospects in the fields of materials science,biomedical science,and environment science.However,it has been a research difficulty in recent years for the preparation methods of Janus colloidal particles.Although,a wide variety of Janus structures have been designed using existing preparation methods.There are still some shortcomings in stable preparation ability of Janus colloidal particles.Moreover,there is an urgent need for a versatile Janus structural design route to meet the diverse needs of colloidal particles in practical applications.In this paper,a complete route was designed from controllable synthesis of SiO₂ microspheres as a colloidal model,to the preparation of Janus SiO₂ templates and SiO₂ Janus particles（SiO₂ JPs）.In this work,an example was provided for the programmed and diversified preparation of Janus colloidal particles.The main research contents are as follows:1)The monodisperse SiO₂ microspheres were controllably synthesized based on St（?）ber method and sol seed method,respectively.Firstly,the effect of the concentration of ammonia（NH₃·H₂O）,ultra-pure water（H₂O）,and tetraethyl silicate（TEOS）on the particles size and morphology of SiO₂ microspheres were explored in the St（?）ber method.And the submicron SiO₂ microsphere seeds（500 nm）with large particle size and good monodispersity were synthesized by adjusting the proportion of the concentration of NH₃·H₂O,H₂O,and TEOS.Then,the relationship between the secondary nucleation phenomenon and the single addition of TEOS was explored during the growth of SiO₂microspheres by the sol seed method.The secondary nucleation phenomenon was successfully suppressed by adjusting the times of TEOS addition.Finally,the SiO₂microspheres with good monodispersity could be controllably synthesized within the particle size of 2μm.2)The stable Janus SiO₂ templates were successfully prepared based on the Pickering emulsion method.Firstly,the factors affecting the formation of Pickering emulsion and its emulsification results were explored.The conditions for the preparation of Janus SiO₂templates were optimized as follows:1 g of paraffin,400μL of SiO₂ microspheres solution,1500 rpm of stirring speed,and 20 min of emulsifying time.Subsequently,the regulation of Janus SiO₂ templates by cationic surfactant DDAB has been studied,which indicated that the embedding depth of the SiO₂ microspheres on the Janus SiO₂ template increases with the increase of the DDAB concentration.Moreover,taking 500 nm and 2μm SiO₂microspheres as examples,the proportion of its asymmetric modified surface was controlled.3)The practicability of Janus SiO₂ templates were verified.Firstly,the pre-prepared SiO₂ Janus templates from Chapter 3 were modified with amino and sulfhydryl groups by silane coupling agents 3-aminopropyl triethoxy silane（APTES）and 3-thiopropyl triethoxy silane（MPTS）,respectively.And the SiO₂ Janus particles with asymmetric surface chemistry（SiO₂@NH₂ JPs and SiO₂@SH JPs）were successfully prepared.Secondly,the SiO₂@Pt JPs with asymmetric morphology and the SiO₂@FITC JPs with asymmetric fluorescence properties were prepared based on further modification of the anisotropy of SiO₂@NH₂ JPs and SiO₂@SH JPs.The versatility of Janus SiO₂ templates has been successfully verified by the preparation of functionalized SiO₂ JPs.