Facile methods for synthesis of core-shell structured and heterostructured Fe ₃ O ₄ @Au nanocomposites

Two different reaction strategies designed for core-shell structured and heterostructured Fe ₃ O ₄ @Au nanocomposites utilizing 50 nm polyethyleneimine coated magnetite as seeds are presented aiming at diverse applications. The polyethylenimine (PEI) coated Fe ₃ O ₄ nanoparticles were firstly used as seeds to carry out the synthesis of both core-shell structured and heterostructured Fe ₃ O ₄ @Au nanocomposites. Results show that these two structures combined the merits of both gold and Fe ₃ O ₄ nanoparticles. What is more, the distinct morphology offers diverse applications: the shell of dense gold nanoparticles coating in the core-shell structure dominates the further surface functionalization while the heterostructure offers the particles with two distinct surfaces and functionalities due to different surfactant molecules on the surface of Fe ₃ O ₄ and Au nanoparticles. Furthermore, the synthesis methods presented in this paper also suggested new ways to the synthesis of multifunctional nanostructures.