• host–guest systems;
  • nanoparticles;
  • noble metals;
  • poly(acrylic acid);
  • sol–gel processes


An efficient and facile one-pot method was developed to fabricate noble-metal nanoparticles (NMNs; Au, Pt, PdO and Ag) that were encapsulated within hollow silica nanospheres (HSNs; NMNs@HSNs) with a size of about 100 nm. NMNs@HSNs were afforded in very high yields between 85–95 %. Poly(acrylic acid) (PAA) polyelectrolyte played a dual role in the fabrication process, both as a core template of the HSNs and as a captor of the NMNs through coordination interactions between the COO groups on the ammonium polyacrylate (APA) polyanionic chains and the empty orbital of the Au atom. The amount of Au loading in Au@HSNs was easily regulated by varying the volume of the HAuCl4 solution added. In addition, these rattle-type particles were successfully applied in the catalytic reduction of 2-nitroaniline (2-NA) as a model reaction, thus indicating that the micropores in the silica shell could achieve the transport of small species—with a size smaller than that of the micropores—into the cavity. Thus, these fabricated NMNs@HSNs have promising applications in catalysis.