One‐Pot Fabrication of Noble‐Metal Nanoparticles That Are Encapsulated in Hollow Silica Nanospheres: Dual Roles of Poly(acrylic acid)

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.