Synthesis and Film Formation of Magnetic FeCo Nanoparticles with Graphitic Carbon Shells

FeCo nanoparticles (NPs) are promising soft magnetic nanomaterials for use in many applications; however, the present problem is how to prevent oxidation. The most powerful substance for protection of FeCo NPs is graphitic carbon (GC). Here, we present a novel and simple technique for the large-scale synthesis of GC-coated FeCo NPs with varied Fe/Co ratios based on the reductive thermal conversion of nanometric Prussian blue analogues (PBAs). The key point is that surfaces of PBA NP precursors are coordinately stabilized by an organic layer of oleylamine, which serves as a carbon source for the GC shells of FeCo NPs during the thermolysis of PBA NPs. We have also succeeded in the facile formation of a stable FeCo NP film with GC shells that displays magneto-optical properties. The technique could be adapted to other transition metals and would be used in versatile fields such as spintronics and biotechnology.