Size-controlled synthesis of magnetite nanoparticles

Monodisperse magnetite nanoparticles have been synthesized by high-temperature solution-phase reaction of Fe(acac)₃ in phenyl ether with alcohol, oleic acid, and oleylamine. Seed-mediated growth is used to control Fe₃O₄ nanoparticle size, and variously sized nanoparticles from 3 to 20 nm have been produced. The as-synthesized Fe₃O₄ nanoparticles have inverse spinel structure, and their assemblies canbe transformed into γ-Fe₂O₃ or α-Fe nanoparticle assemblies, depending on the annealing conditions. The reported procedure can be used as a general approach to various ferrite nanoparticles and nanoparticle superlattices.