Post-treatment Method for the Synthesis of Monodisperse Binary FePt-Fe₃O₄ Nanoparticles

To obtain the optimal 1:1 composition of FePt alloy nanomaterials by polyol synthesis, the iron precursor (iron pentacarbonyl, Fe(CO)₅) must be used in excess, because the Fe(CO)₅ exists in the vapor phase at the typical temperatures used for FePt synthesis and cannot be consumed completely. Fabrication of Fe₃O₄ nanoparticles by consuming the excess iron precursor was an effective strategy to make full use of the iron precursor. In this paper, a facile post-treatment method was applied to consume the excess iron, which was oxidized to Fe₃O₄ after post-treatment at 150 and 200 °C, and a monodisperse binary FePt-Fe₃O₄ nanoparticle system was generated. The post-treatment method did not affect the crystal structure, grain size, or composition of the FePt nanoparticles. However, the content and grain size of the fcc-Fe₃O₄ nanoparticles can be increased simply by increasing the post-treatment temperature from 150 to 200 °C.