Effects of Process Variables on Properties of CoFeO Nanoparticles Prepared by Solvothermal Process.

Controlling the morphology and magnetic properties of CoFeO nanoparticles is crucial for the synthesis of compatible materials for different applications. CoFeO nanoparticles were synthesized by a solvothermal method using cobalt nitrate, iron nitrate as precursors, and oleic acid as a surfactant. The formation of CoFeO nanoparticles was systematically observed by adjusting synthesis process conditions including reaction temperature, reaction time, and oleic acid concentration. Nearly spherical, monodispersed CoFeO nanoparticles were formed by changing the reaction time and reaction temperature. The oleic acid-coated CoFeO nanoparticles inhibited the growth of particle size after 1 h and, therefore, the particle size of CoFeO nanoparticles did not change significantly as the reaction time increased. Both without and with low oleic acid concentration, the large-sized cubic CoFeO nanoparticles showing ferromagnetic behavior were synthesized, while the small-sized CoFeO nanoparticles with superparamagnetic properties were obtained for the oleic acid concentration higher than 0.1 M. This study will become a basis for further research in the future to prepare the high-functional CoFeO magnetic nanoparticles by a solvothermal process, which can be applied to bio-separation, biosensors, drug delivery, magnetic hyperthermia, etc.