Chemically Driven Phase Segregation of Alloy Nanoparticles: A Versatile Route to Dual-Plasmonic Gold@Copper Chalcogenide Heteronanostructures

Multicomponent heteronanostructures have emerged as a class of structurally and compositionally tunable multifunctional nanomaterials whose electronic, optical, and catalytic properties can be fine-engineered for targeted applications. Heteronanostructures composed of Au and copper chalcogenide domains represent a unique hybrid material system that integrates two distinct types of plasmon resonances arising from the conduction electrons and valence holes, respectively, in a single nanoscale entity. Success in fine-tuning the optical properties of these dual-plasmonic heteronanostructures relies critically on our capabilities to precisely tailor not only the structural arrangements but also the crystalline phases of the constituent domains. Here, we report a robust and versatile colloidal synthetic approach that allows us to selectively access a series of Au@copper chalcogenide heteronanostructures with tailored intraparticle architectures, tunable domain sizes, and targeted crystalline phases through chemically triggered phase segregation of Au-Cu bimetallic alloy and intermetallic nanoparticles. Under our reaction conditions, the chalcogen precursor concentration and the reaction temperature serve as two fine-adjustable synthetic knobs that enable us to deliberately control the crystalline phases of the copper chalcogenide domains, while the relative domain dimensions in the heteronanostructures can be precisely preprogrammed by tuning the Cu/Au stoichiometries of the parental bimetallic nanoparticles. Both the Cu/Au stoichiometries and atomic ordering in the bimetallic nanoparticles are found to be key structural factors that kinetically maneuver the phase segregation process and thereby profoundly influence the structure-transforming behaviors of the nanoparticles.