General Method for the Fabrication of Hollow Microcapsules with Adjustable Shell Compositions

In this paper, a facile and general strategy has been proposed for the preparation of a series of microcapsules with the diverse shell compositions from silica to nonsilica (e.g., titania, zirconia, platinum, silver sulfide, cadmium sulfide, indium sulfide, and cadmium telluride) by simply alkaline treating the cationic polyelectrolyte precoated mesoporous silica spheres (MSSs) with or without the encapsulated guest species. The MSS acts both as the spherical template for the morphology of the final product and as the nanoreactor/reservoir of the nonsilica nanoparticles in their 3D-connected channels, while the cationic polymer precoated outside plays an interesting role of exonet or spherical scaffold for the construction of the shell in the final products through capturing and immobilizing the nanoparticles released during the core etching. The mechanism on the formation of the shell has also been revealed through investigating the morphology evolution of the samples during the alkaline treatment. Such a synthesis route could be extended to the fabrication of most of the alkaline-stable hollow microcapsules in principle.