Monosized core-shell Fe3O4(Fe)/Au multifunctional nanocrystals.

We have synthesized highly crystalline, monosized Fe3O4(Fe)/Au magnetic-optic multifunctional nanocrystals using a modified polyol process. The formation of the core-shell structure was achieved in two consecutive steps, seeding the Fe3O4(Fe) core followed by coating the gold shell. The characterization demonstrates the core-shell nanostructure and provides particle size and distribution of the nanocrystals. The spectroscopic analysis gives three Fe oxidation states (Fe0, Fe+2 and Fe+3) in the core and the surface plasmon characteristic of the Au nanoshell, while the magnetic measurements show excellent susceptibility of the nanocrystals.