Synthesis and characterization of mesoporous and superparamagnetic bilayered-shell around silica core particles

Abstract

Multifunctional bilayered shell around monodispersed silica core particles was prepared by wet-chemical synthesis process. The first outer layer was composed of mesoporous silica and the second internal layer was composed of superparamagnetic Fe3O4 nanoparticles. Ferrite nanoshell was synthesized by assembling of oppositely charged ferrite (Fe3O4) nanoparticles on the surface of the monodispersed silica core particles (having average size of ~0.5µm and prepared by hydrolysis and condensation of tetraethylortosilicate). The obtained Fe3O4 layer was superparamagnetic and had very weakly developed pore structure. The second layer on the previously obtained particles with silica core and Fe3O4 shell was formed by deposition of silica nanoparticles from a silicate solution. To allow electrostatic assembling of the silica nanoparticles and formation of external silica layer around the silica/Fe3O4 particles, the latter were functionalized with poly(diallyldimethylammonium chloride) (PDDA). Obtained silica layer had well developed pore structure with average pore size of 10nm. The obtained composite particles with two functional layers can be used in bioengineering for immobilization of enzymes inside external mesoporous silica layer while internal superparamagnetic ferrite layer would allow magnetic separation from reaction mixture.