A green and facile approach for synthesis of magnetite nanoparticles with tunable sizes and morphologies

Magnetite nanoparticles with tunable sizes and morphologies were synthesized by heating an aqueous solution of Fe2+/Fe3+ (1/2, molar ratio) and urea without or with additives at 85 °C. Polyhedral magnetite nanocrystals with an average size of ~ 300 nm were prepared without any additive. When poly(vinyl alcohol) (PVA) was used as an additive, microspherical magnetite particles composed of clustered nanocrystals were got. The diameters of the microspheres can be tuned from ~ 100 to ~ 280 nm by changing the concentration of PVA. Larger and looser (porous) microspheres were obtained with acetic acid as the secondary additive in addition to PVA. Magnetite nanorods or flowerlike particles were got with poly(acrylic acid) as the additive. The as-synthesized products showed high saturation magnetization and low coercivity or remanence.

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► Magnetite nanoparticles with tunable sizes and morphologies.
► Heating Fe2+/Fe3+/urea/H2O (85 °C) gets polyhedral magnetite nanocrystals.
► Heating Fe2+/Fe3+/urea/HAc/poly(vinyl alcohol)/H2O (85 °C) gets porous microspheres.
► Heating Fe2+/Fe3+/urea/poly(acrylic acid)/H2O (85 °C) gets rods or flowers.