Air-stable Fe and Co crystalline nanocomposite particles prepared by a single-step swelling of metal precursors within polystyrene microspheres of narrow size distribution

Polystyrene template microspheres of narrow size distribution were prepared by dispersion polymerization of styrene in a mixture of ethanol and 2-methoxyethanol. These template particles, dispersed in an aqueous solution, have been used to entrap Fe₃(CO)₁₂ and Co ₂(CO)₈ complexes, using a single-step swelling process of methylene chloride and benzene emulsion droplets containing these complexes, within the particles. The effect of the swelling solvents (methylene chloride and benzene) on the size and size distribution of the swollen template particles was elucidated. Air-stable Fe and Co nanocomposite particles have been prepared by thermal decomposition of the Fe₃(CO)₁₂ and Co ₂(CO)₈ swollen template particles at 600°C in an inert atmosphere. These nanocomposite particles have a core-shell structure, where a thin coating of metal oxide and carbon protects the core crystalline metal (Fe and Co) from oxidation. The characterization of the various microspheres and the air-stable Fe and Co nanocomposite particles was accomplished by light microscopy, TEM, SEM, XRD, XPS, elemental analysis, and magnetic measurements.