Gold nanorings synthesized via a stress-driven collapse and etching mechanism

Toroidal Au or Ag nanostructures are of particular interest due to their unique optical responses and superior catalytic applications. However, the fabrication of ring-like Au or Ag nanostructures is limited to either electron beam lithography or template techniques, thus hampering their applications. Here, we present a new stress-driven structure collapse and etching mechanism to synthesize Au nanorings via a direct one-pot solution-based chemical reaction. The nanoparticle-mediated recrystallization process contributes to the formation of Au nanoframes, which contain unusual stress, thus promoting the breakup of the nanoframes and finally converting them into Au nanorings. The Au nanorings with tunable hole sizes exhibit interesting localized surface plasmon features owing to the coupling of bonding and antibonding modes on the inner and outer surfaces of the nanorings. This facile approach may open the door for the preparation of toroidal nanostructures in other compositions for numerous applications.