Facile fabrication of hollow mesoporous silica microspheres with hierarchical shell structure via a sol–gel process

Abstract A facile method for the preparation of polystyrene/silica (PS/SiO 2 ) composite microspheres via sol–gel process of tetraethylorthosilicate (TEOS) employing polyvinylpyrrolidone-functionalized monodispersed PS microspheres as template is proposed. Hollow mesoporous silica microspheres containing surface silica nanoparticles are successfully fabricated after the calcination of the composite microspheres. The shell thickness, the size of surface silica nanoparticles and the surface morphology of hollow mesoporous silica microspheres can be readily tailored by adjusting the concentrations of TEOS and ammonia (NH 4 OH). The formation mechanism of the products is detailed through the investigation of the products at different reaction conditions. At the low NH 4 OH/TEOS volume ratio (<1), intact hollow mesoporous silica microspheres with hierarchical raspberry-like structure can be obtained. This synthesis method is simple, straightforward and suitable for the preparation of the other biomineral nanostructures that are unique carriers in drug delivery, biological and catalytic applications. Graphical Abstract