Facile synthesis of hollow urchin-like gold nanoparticles and their catalytic activity

The galvanic replacement reaction between Ag nanoparticles (NPs) and HAuCl 4 followed by addition of ascorbic acid led to the formation of AuNPs sharing both urchin-like and hollow structures. The AgNPs took as sacrificial templates to guide the hollow structure and the intermediates provided rough surface and active sites for the further deposition of AuNPs, which originated from the reduction of excess HAuCl 4 by ascorbic acid. These unique structured AuNPs presented excellent optical properties and great advantages in catalysis applications.