Facile synthesis by laser ablation in liquid of nonequilibrium cobalt-silver nanoparticles with magnetic and plasmonic properties

Abstract

Appealing physical and chemical properties are foreseen in nanoparticles containing immiscible elements, but their synthesis is a significant challenge due to the unfavorable thermodynamics. Here we show that silver nanoparticles homogeneously doped with Co can be achieved by a facile one-step route relying on laser ablation in liquid, despite the complete immiscibility of the two metals at any temperature in solid and liquid phase. Structural analysis evidenced that the non-equilibrium alloy nanoparticles consist of a cobalt-doped face centered cubic Ag crystalline lattice, stable over time even in aqueous solution due to inhibition of atomic diffusivity. The Co-Ag nanoalloys benefit of silver features such as the plasmonic response and the easy surface chemistry with thiolated ligands, combined with the magnetic properties of cobalt, thus potentially opening the way to several technologically relevant applications. As a proof of concept, we demonstrate magnetophoretic assembly of Co-Ag nanoalloys into arrays of plasmonic dots exploitable for surface enhanced Raman spectroscopy.