Tailoring the nickel nanoparticles anchored on the surface of Fe 3 O 4 @SiO 2 spheres for nanocatalysis.

Herein, we report an efficient and universal strategy for synthesizing a unique triple-shell structured Fe3 O4 @SiO2 @C-Ni hybrid composite. Firstly, the Fe3 O4 cores were synthesized by hydrothermal reaction, and sequentially coated with SiO2 and a thin layer of nickel-ion-doped resin-formaldehyde (RF-Ni2+ ) using an extended Stöber method. This was followed by carbonization to produce the Fe3 O4 @SiO2 @C-Ni nanocomposites with metallic nickel nanoparticles embedded in an RF-derived thin graphic carbon layer. Interestingly, the thin SiO2 spacer layer between RF-Ni2+ and Fe3 O4 plays a critical role on adjusting the size and density of the nickel nanoparticles on the surface of Fe3 O4 @SiO2 nanospheres. The detailed tailoring mechanism is explicitly discussed, and it is shown that the iron oxide core can react with the nickel nanoparticles without the SiO2 spacer layer, and the size and density of the nickel nanoparticles can be effectively controlled when the SiO2 layer exits. The multifunctional composites exhibit a significantly enhanced catalytic performance in the reduction of 4-nitrophenol (4-NP).