• catalyst;
  • core/shell particles;
  • SPIO;
  • yolk-like microparticles


Yolk-like nano/microparticles with superparamagnetic iron oxide (SPIO) cores and hierarchical nickel silicate (NS) shells, designated yolk SPIO@NS, are fabricated by combining the versatile sol–gel process and the hydrothermal reaction, involving the coating of SPIO particles with SiO2 and transformation of the SiO2 shells into NS hollow spheres with hierarchical nanostructures. Various yolk/shell nanostructures with tunable NS shell thicknesses and SPIO core sizes are successfully prepared by controlling the experimental para­meters. Au nanoparticles can be impregnated into the yolk-like microspheres in situ to form SPIO@NS/Au composite particles and the as-prepared magnetic nanocatalysts show good catalytic activity, using the catalytic reduction of RhB as a model reaction. This facile method can be extended to the synthesis of other encapsulated particles with yolk-like nanostructure.