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.