Reactive AgAuS and Ag₃AuS₂ Synthons Enable the Sequential Transformation of Spherical Nanocrystals into Asymmetric Multicomponent Hybrid Nanoparticles

Nanoscale heterostructures that interface with multiple distinct materials provide opportunities to engineer functional complexity into single-particle constructs. However, existing synthetic pathways to such hybrid nanoparticles emphasize surface-seeded growth, which limits the scope of accessible systems. Here, we introduce an alternative approach that transforms isotropic nanocrystals into asymmetric, multicomponent Janus particles through sequential deposition, reactive phase segregation, and cation exchange processes that are mediated by an unusual class of reactive synthons. After Ag-Au seed particles had formed and had reacted with sulfur, a series of segregated Au_1-xAg_x-AgAuS and Au_1-xAg_x-Ag₃AuS₂ hybrid nanoparticles form. The AgAuS and Ag₃AuS₂ domains provide a synthetic entryway into solution-mediated cation exchange reactions, with the compositions of the Ag-Au-S synthons defining the components, morphologies, and interfaces of the hybrid nanoparticle products. Upon cation exchange with Pb²⁺, Au_1-xAg_x-AgAuS forms Ag_1-xAu_x-PbS heterodimers while Au_1-xAg_x-Ag₃AuS₂ forms Ag_1-xAu_x-Ag₂S-PbS heterotrimers. The process by which isotropic metal nanoparticles transform into asymmetric hybrid nanoparticles through reactive Ag-Au-S synthons provides important insights that will be applicable to the retrosynthetic design of complex nanoscale heterostructures having expanded multifunctionality and synergistic properties.