Heterogeneous to homogeneous Cu–Ag nanoparticles by laser reduction in liquid

Controlling the compositional structure of Cu–Ag bimetallic nanoparticles (NPs) is challenging due to the immiscibility of copper and silver. We report synthesis of Cu–Ag NPs with tunable compositions and structures using femtosecond laser reduction in liquid (LRL) of solutions containing copper and silver complexes dispersed in a mixture of methanol and isopropyl alcohol. Either janus or homogeneous alloy structure of Cu–Ag NPs are produced, depending on the concentration of precursors in solution. The synthesized NPs also exhibit elemental compositions in line with Cu and Ag precursor ratios. The nonequilibrium reaction conditions of LRL produce a high density of randomly distributed Ag and Cu atoms that undergo rapid cooling as they coalesce into NPs, making LRL one of the few methods for the synthesis of homogeneous CuAg alloy NPs.