Comparison of schemes for preparing magnetic Fe3O4 nanoparticles

Magnetic Fe₃O₄ nanoparticles were prepared by means of coprecipitation using NH₃·H₂O in water and in alcohol, and using NaOH in water. A series of instruments such as SEM, TEM, HRTEM, FT-IR, XRD and VSM were used to characterize the properties of the magnetic nanoparticles. The results indicated that the magnetism of Fe₃O₄ nanoparticles synthesized using NH₃·H₂O in water was the highest, although the reaction time was the longest. The process using NaOH in water was the simplest and the reaction time was the shortest, but the particle characteristics were inferior to those of the other two methods. The mean size of magnetic Fe₃O₄ nanoparticles prepared by coprecipitation in alcohol was the smallest among the three, but the nanoparticles aggregated severely. The magnetic Fe₃O₄ nanoparticles were coated with oleic acid using saturated sodium oleate, and the polarity of the surface-modified nanoparticles was measured. Fe₃O₄ nanoparticles prepared using NH₃·H₂O, not NaOH, could be coated successfully and thoroughly.