The morphology of product is strongly dependent on the capping ligand. The Ag MTPs were made with oleylamine as the capping ligand. After ligand exchange, they were capped with (A) oleic acid and (E) TOPO, respectively. When reacted with 2.6 mL of 0.5 mM HAuCl4, few hollow particles were observed for (B) oleic acid-capped and (F) TOPO-capped Ag nanoparticles and the majority of the particles turned from spherical to irregular shapes. (C, D) HRTEM images of Ag nanoparticles capped with oleic acid before and after the replacement reaction. The oleic acid-capped Ag nanoparticles also had a MTP structure. After replacement reaction, the MTP pattern cannot be identified any more.