Hydrothermal Synthesis of Monodisperse Magnetite Nanoparticles

Abstract

Magnetite particles with an average size of 39 nm and good monodispersity have been synthesized by coprecipitation at 70 °C from ferrous Fe 2+ and ferric Fe 3+ ions by a (N(CH 3 ) 4 OH) solution, followed by hydrothermal treatment at 250 °C. The magnetite nanoparticles before the hydrothermal step display an average size of 12 nm and are highly oxidized when they are in contact with air. Complementary microstructural and magnetic characterizations of nanoparticles after hydrothermal treatment show unambiguously that they consist of magnetite with only a slight deviation from stoichiometry (δ ≈ 0.05), leading to Fe 2.95 O 4 .