Facile synthesis of Fe3O4/SiO2 composite nanoparticles from primary silica particles

Abstract A facile method was developed for preparation of Fe 3 O 4 /SiO 2 composite nanoparticles by direct introduction of Fe 3 O 4 nanoparticles into the Stober process upon formation of the primary silica particles. When the Fe 3 O 4 nanoparticles were added into the reaction mixture at appropriate time, the primary particles can quickly aggregate with the Fe 3 O 4 nanoparticles, thus suppressing the dipole–dipole interactions among the magnetic nanoparticles effectively and allowing the synthesis of Fe 3 O 4 /SiO 2 composite nanoparticles with defined structure by further deposition of silica layer. Such a method can also be applied for coating silica layer on other water soluble nanoparticles with surface affinity to silica, such as 3-mercaptopropionic acid (MPA) capping ZnS:Mn and citrate modified Au nanoparticles.