A general and feasible method for the fabrication of functional nanoparticles in mesoporous silica hollow composite spheres

Abstract

This paper presents a general and feasible method for the fabrication of uniform hollow mesoporous nanocomposite silica spheres (HMNSs) loaded with functional nanoparticles (Au, Pt, Fe₃O₄, etc.) on their inner walls. In this approach, carboxylic-capped polystyrene (PS) spheres were first synthesized by a soap-free emulsion polymerization and then deposited on a layer of poly(diallyldimethylammonium chloride) (PDDA). Next, the functional nanoparticles were self-assembled onto the surfaces of the PS spheres through electrostatic interactions between the negatively-charged citrate groups and the positively-charged PDDA layer. After encapsulation of the hybrid shell derived from the sol–gel process of tetraethoxysilane (TEOS) and n-octadecyltrimethoxysilane (C₁₈TMS), followed by calcination, various HMNSs loaded with functional nanoparticles such as Au@SiO₂, Pt@SiO₂, Fe₃O₄@SiO₂, etc. could be fabricated. This approach allows the control of the numbers of functional nanoparticles loaded into the hollow spheres very easily and prevents nanoparticle aggregation effectively. As a prototype, the as-obtained Au@SiO₂ HMNSs displayed very good catalytic reusability.