Synthesis and properties of Au－Fe₃O₄ and Ag－Fe₃O₄ heterodimeric nanoparticles

Monodisperse Au--Fe₃O₄ heterodimeric nanoparticles (NPs) were prepared by injecting precursors into a hot reaction solution. The size of Au and Fe₃O₄ particles can be controlled by changing the injection temperature. UV--Vis spectra show that the surface plasma resonance band of Au--Fe₃O₄ heterodimeric NPs was evidently red-shifted compared with the resonance band of Au NPs of similar size. The as-prepared heterodimeric Au--Fe₃O₄ NPs exhibited superparamagnetic properties at room temperature. The Ag--Fe₃O₄ heterodimeric NPs were also prepared by this synthetic method simply using AgNO₃ as precursor instead of HAuCl₄. It is indicated that the reported method can be readily extended to the synthesis of other noble metal conjugated heterodimeric NPs.