Overcoming the Interfacial Lattice Mismatch: Geometry Control of Gold–Nickel Bimetallic Heteronanostructures

Seed‐mediated heteroepitaxial growth provides a versatile synthetic approach to a diverse set of geometrically distinct bimetallic heteronanostructures. In bimetallic nanocrystal systems, interfacial heteroepitaxial growth typically occurs between structurally similar metals with lattice mismatch below 5%, whereas controlled epitaxial growth of bimetallic nanocrystals comprising metals with larger lattice mismatches or even dissimilar crystalline structures has long been challenging. Here, the epitaxial growth of both face‐centered cubic (fcc) and hexagonal close‐packed (hcp) Ni on fcc Au nanocrystal seeds in polyol solvents is systematically investigated, to shed light on the complex mechanisms underpinning the intriguing geometric evolution of lattice‐mismatched bimetallic nanocrystals during seed‐mediated heteroepitaxial overgrowth. The success in geometry‐controlled syntheses of a series of Au–Ni bimetallic heteronanostructures, such as conformal core–shell nanoparticles, asymmetric heterodimers, and multibranched core–satellite nanocrystals, represents a significant step toward the extension of nanoscale interfacial heteroepitaxy from lattice‐matched bimetallic systems to the ones exhibiting large lattice mismatches and even dissimilar crystalline structures. The insights gained from this work serve as a central design principle that guides the development of new synthetic approaches to architecturally sophisticated and compositionally diverse multimetallic heteronanostructures.