Preparation Of Silica-based Microspheres With Core/Shell Structure

Core-shell structured composite microspheres combine the properties of different materials, which make up the shortage of those microspheres with single component. Comparing with microspheres with single component, core-shell composite microspheres show their advanced and various properties, such as monodispersity, stability, modification, self-assembly behaviors, and applications in optics, electronics, magnetics, catalyst, chemical and biological processes. All of above properties can be tuned by proper designing the morphology and component of composite microspheres.Silica is a widely used material for preparing core-shell composite microspheres, for its easy operation, low-cost, stability and modifying functionality. With magnetical activity and selective absorbability, magnetic core-shell composite microspheres with silica shell can be used for purifying protein and separating cells. Furthermore, the colloidal crystals of these kind of magnetic composite microspheres can also be utilized as displays or sensors. Due to this, this thesis describes the following studies:1,In modified St?ber method, silica microspheres with good monodispersity were prepared. The relationship between the diameters of silica microspheres and hydrolysis temperature was studied. PS@SiO₂ composite microspheres were also prepared by surface depositing method using PS microspheres as template. The subsequent high-temperature calcinated silica hollow spheres can also be used as the backbone materials of liquid inverse opal.2,α-Fe₂O₃ colloids were synthesized by Hydrothermal Synthesis Method. The formation mechanism, including the relationship between the amount of chemicals and the particle size was discussed. After silica coating onto the surface of the synthesizedα-Fe₂O₃ cores,α-Fe₂O₃@SiO₂ composite ellipsoidal colloids with different aspect ratios were successfully synthesized. Under proper conditions and in L-B film method, these ellipsoidal colloids were close-packed into monolayer with two-dimensional arrays at air/water interface.3,In hydrothermal synthesis method,α-Fe₂O₃ colloids were synthesized by controlling the anion concentration. Parameters which effect the morphology of synthesized particles were discussed. Monodispersedα-Fe₂O₃@SiO₂ composite microspheres were synthesized in modified St?ber method and assembled into colloidal crystals. After the subsequent magnetization, magnetically active colloidal photonic crystals may be fabricated for furthermore magnetical and electrical responsing detecting.