Surface-Plasmon-Mediated Alloying for Monodisperse Au–Ag Alloy Nanoparticles in Liquid

Plasmonic noble-metal nanoparticles with broadly tunable optical properties and catalytically active surfaces offer a unique opportunity for photochemistry. Resonant optical excitation of surface-plasmon generates high-energy hot carriers, which can participate in photochemical reactions. Although the surface-plasmon-driven catalysis on molecules has been extensively studied, surface-plasmon-mediated synthesis of bimetallic nanomaterials is less reported. Herein, we perform a detailed investigation on the formation mechanism and colloidal stability of monodisperse Au–Ag alloy nanoparticles synthesized through irradiating the intermixture of Au nanochains and AgNO3 solution with a nanosecond pulsed laser. It is revealed that the Ag atoms can be extracted from AgNO3 solution by surface-plasmon-generated hot electrons and alloy with Au atoms. Particularly, the obtained Au–Ag alloy nanoparticles without any surfactants or ligands exhibit superior stability that is confirmed by experiments as well as DLVO-based theoretical simulation. Our work would provide novel insights into the synthesis of potentially useful bimetallic nanoparticles via surface-plasmon-medicated alloying.