A general process for preparation of core-shell particles of complete and smooth shells

Core-shell particles have attracted much research attention in recent years because of the great potential in protection, modification, and functionalization of the core particles with suitable shell materials to achieve specific physical, chemical, and biological performance. A general approach for preparation of core-shell particles possessing complete and smooth shells is presented. The shell layer was constructed by introducing nanoparticles of desired shell material, prepared with the reverse micelle process, onto the core particle surface via layer-by-layer electrostatic adsorption, hydrophilic and hydrophobic interactions, and subsequent sintering. The proposed process is illustrated by coating silica spheres with four different shell materials, including Ag, CdS, ZnS, and TiO2. The successful formation of complete and smooth shell was examined with a novel light scattering intensity decay method and also by direct observation of scanning electron microscope and transmission electron microscope images.