Fe3O4 nanoparticles; radius 5.6 nm (AFM based)

Magnetite nanoparticles were fabricated by the coprecipitation of Fe2+ and Fe3+ by NH4OH at 60 °C. Afterwards, an magnetic fluid (MF) was obtained by dispersion of the freshly prepared magnetite nanoparticles in water and electrostatically stabilized by the addition of HClO4. The final concentration of MNPs in the MF was 28 mg/mL. The hydrodynamic diameter of the MNPs, determined by dynamic light scattering (DLS) (Zetasizer), has a nominal size of 26 nm alongside polydispersity of 0.26, and the radius of MNPs estimated from AFM was 5.6 nm.