Preparation of water-soluble magnetic nanoparticles with controllable silica coating

This work provides a general method for preparing monodisperse, water-soluble and paramagnetic magnetic nanoparticles which are easy to be modified. Firstly, magnetic silica with core-shell structure was prepared according to a previous work. Then, the magnetic silica was treated with alkali solution to afford magnetic nanoparticles. With the increase of calcination temperature for the preparation of magnetic silica, the crystallinity and the magnetic responsibility of magnetic silica strengthened, meanwhile, the corresponding magnetic nanoparticles kept monodisperse without any aggregation. The magnetic nanoparticles are comprised of cobalt ferrite and a silica coating. The silica coating on the cobalt ferrite facilitates the magnetic nanoparticles well-dissolved and monodisperse in water, and easily modified.