Implantation of Fe3O4 Nanoparticles in Shells of Au@m-SiO2 Yolk@Shell Nanocatalysts with Both Improved Recyclability and Catalytic Activity.

Multifunctional nanocatalysts of Au@Fe3O4/m-SiO2 yolk@shell hybrids had been developed through a template-assisted synthesis, where Fe3O4 nanoparticles (∼12 nm) and m-SiO2 shells were sequentially assembled on surfaces of Au/SiO2 core/shell templates, followed by selective etching of the inner SiO2 cores, leading to the formation of Au@Fe3O4/m-SiO2 yolk@shell hybrids. The Fe3O4 nanoparticles were implanted in the inner surfaces of m-SiO2 shells with partially exposed surfaces to the inner cavity. The novel design not only ensures a high surface area (540.0 m2/g) and saturation magnetization (48.6 emu/g) of the hybrids but also enables interaction between Au and Fe3O4 nanoparticles. Catalytic tests toward the reduction of 4-nitrophenol in the presence of NaBH4 indicated that Au@Fe3O4/m-SiO2 yolk@shell nanocatalysts not only showed high stability and recyclability but also maintained improved catalytic activity as a result of the synergetic effect resulting from Au and Fe3O4 interactions.