Simple solvothermal synthesis of hydrophobic magnetic monodispersed Fe3O4 nanoparticles

A new solvothermal method is proposed for the preparation of Fe 3 O 4 nanoparticles (NPs) from iron acetylacetonate in the presence of oleylamine and n- hexane. The products are characterized by X-ray powder diffraction, infrared (IR) spectroscopy, transmission electron microscopy, thermogravimetry/differential thermogravimetry (TG/DTG) analysis, and vibrating sample magnetometery. The new procedure yields superparamagnetic monodispersed Fe 3 O 4 particles with sizes ranging from 7   nm to 12   nm. The nanocrystal sizes are controlled by adjusting the volume ratio of oleylamine to n- hexane. IR and TG/DTG analyses indicate that the oleylamine molecules, as stabilizers, are adsorbed on the surface of Fe 3 O 4 NPs as bilayer adsorption models. The surface adsorption quantities of oleylamine on 7.5 and 10.4 nm-diameter Fe 3 O 4 NPs are 18% and 11%, respectively. The hydrophobic surface of the obtained nanocrystals is passivated by adsorbed organic solvent molecules. These molecules provide stability against agglomeration, enable solubility in nonpolar solvents, and allow the formation of magnetic polymer micelles.