Ceria nanoparticle vesicles formed in sodium oleate aqueous solution with mesoporous silica coating

Fabrications of nanoparticle-assembled hollow structures have intensively been studied because of their unique properties applicable to catalysts, plasmonic materials and drug delivery systems. The present work proposes a novel method for the synthesis of nanoparticle vesicles in the presence of sodium oleate (NaOA). Our method is composed of two processes, one of which is self-assembly formation in the suspension of ceria nanoparticles (CeNPs) and NaOA, and the other is the fixation of the self-assembled structures with silica coating. The method is a facile one-pot synthesis conducted in weak basic conditions with and without ammonia. N-trimethoxysilyl-propyl-N,N,N-trimethylammonium chloride (TMAPS) and tetramethoxysilane were successively added for the silica coating. The structure of the product was submicron-meter sized hollow assembly of the ceria nanoparticles with outer silica shell, silica-coated CeNP vesicle. The calcined sample had meso-pore structures in the silica shells. The present method may open the door for application to various kinds of metal oxides and inorganic nanoparticles for obtaining nanoparticle vesicles.