Rational synthesis and tailored optical and magnetic characteristics of Fe3O4–Au composite nanoparticles

To minimize saturation magnetization (Ms) degradation and simultaneously maintain the optical and magnetic responsiveness characteristics of Fe3O4/Au nanocomposites, we successfully prepared Fe3O4–Au seeds composite nanoparticles (NPs) by a novel seed deposition process. The effects of gold seeds coating amounts and the concentration of Fe3O4 NPs on the morphologies of final products are extensively characterized. The results of energy-dispersive spectrometry mapping show that the gold seeds are uniformly adhered onto the Fe3O4 NPs surfaces in precisely controlled amount. Importantly, with the electronic redistribution between Fe3O4 and Au NPs interfaces, the obvious position shifting of Fe 2p and Au 4f electronic binding energy peaks is observed. Upon increasing surface coatings of gold seeds, the electron deficiency on the gold NPs leads to the redshift of the absorption peak. Though Ms declines slightly due to the diamagnetic contribution from decorated gold seeds, the developed Fe3O4–Au seeds composite NPs possess the robust magnetic responsiveness and they are amenable to be separated and recycled by the external magnet, which facilitates great potential applications in biological, medical and photocatalytic fields.