Preparation and characterization of core-shell monodispersed magnetic silica microspheres

Core-shell monodispersed magnetic silica microspheres with tailored dimensions and compositions have been fabricated by consecutively assembling magnetite (Fe3O4) nanoparticles and polyelectrolyte onto silica microspheres. The layers were deposited under conditions where Fe3O4 and poly(diallyldimethylammonium chloride) (PDADMAC) are oppositely charged, thereby utilizing electrostatic attractions for multiplayer buildup. The alternating ζ-potentials and transmission electron microscopy (TEM) measurements provided direct evidence of the stepwise multilayers growth, and the elemental Auger electron spectroscopy (AES) depth profile of core-shell magnetic silica microspheres indicate that the contents of Fe and C decrease but the contents of Si and O increase with sputtering. The fabrication of these magnetic silica microspheres is expected to produce novel particles with potential applications in various fields of materials science and biotechnology.