Facile Synthesis of Monodisperse Maghemite and Ferrite Nanocrystals from Metal Powder and Octanoic Acid

Extremely small, monodisperse, and spheric maghemite (γ-Fe₂O₃, 2–3 nm) and manganese (4–7 nm), cobalt (3–5 nm), and zinc ferrite (5–7 nm) nanocrystals are directly accessible on a large scale starting from inexpensive metal powders and octanoic acid by thermolysis in a high-boiling solvent. Bigger particle size is obtainable by prolonged reaction time according to the Ostwald ripening principle. The superparamagnetic nanocrystals and their assembly have been characterized by transmission electron microscopy, powder X-ray diffraction, Mössbauer spectroscopy, magnetic measurements, and energy-dispersive X-ray spectroscopy.