Intertwining Roles of Silver Ions, Surfactants, and Reducing Agents in Gold Nanorod Overgrowth: Pathway Switch between Silver Underpotential Deposition and Gold–Silver Codeposition

Abstract

The past two decades have witnessed great success achieved in the geometry-controlled synthesis of metallic nanoparticles using the seed-mediated nanocrystal growth method. Detailed mechanistic understanding of the synergy among multiple key structure-directing agents in the nanocrystal growth solutions, however, has long been lagging behind the development and optimization of the synthetic protocols. Here we investigate the foreign ion- and surfactant-coguided overgrowth of single-crystalline Au nanorods as a model system to elucidate the intertwining roles of Ag+ foreign ions, surface-capping surfactants, and reducing agents that underpin the intriguing structural evolution of Au nanocrystals. The geometry-controlled nanorod overgrowth involves two distinct underlying pathways, Ag underpotential deposition and Au–Ag electroless codeposition, which are interswitchable upon maneuvering the interplay of the Ag+ ions, surfactants, and reducing agents. The pathway switch governs the geometric and composition...