A parametric study on CoFe-based ferrite and alloy nanoparticle synthesis

Magnetic nanoparticles (MNPs) have received great attention over the last two decades thanks to their potential uses in various application fields such as high-density recording media, magnetic separation and biomedicine. In this work we focus on the exploratory synthesis of cobalt ferrite and iron-cobalt NPs through thermal decomposition wet-chemical pathways. Several parameters were examined in order to elucidate their impact on the composition, morphology and magnetic behaviour of the produced nanomaterials. A range of metallic precursor types is first investigated, with a subsequent focus on the case of acetylacetonate salts. In addition, the reduction of CoFe₂O₄ to FeCo by employing a salt-matrix annealing stage is explored. Polyol and H₂-mediated methods are utilized to prepare FeCo alloy NPs in a direct manner. Multi-core nanostructures were also synthesized, and they are very promising for magnetic resonance imaging (MRI) and magnetic hyperthermia (MH) applications. The post-synthesis thermal treatment helped to convert ferrites to an iron-cobalt alloy, with the expense of significant particle size increase and aggregation. Alloy particles formed in a one-pot synthesis by polyol routes had a >100 nm size and hexagonal shape, while hydrogen-assisted reduction led to monodisperse ∼30 nm NPs with remarkable MH properties.