Au-Ge and Ag-Ge heterodimers with tunable domain sizes: A supersaturation-precipitation route to colloidal hybrid nanoparticles

Colloidal hybrid nanoparticles, which contain multiple inorganic domains that are joined together through solid-solid interfaces, exhibit particle multifunctionality as well as new and enhanced properties that can emerge from the particle-particle interactions. These hybrid nanoparticles are typically synthesized using heterogeneous seeded nucleation of one nanoparticle on the surface of another as well as using phase segregation, surface dewetting of core-shell nanoparticles, and the fusion of premade nanoparticles. However, to expand the materials diversity and the potential range of applications of such systems, alternative routes to heterogeneous seeded nucleation are needed. Here, we show that solution-liquid-solid and related supersaturation-precipitation strategies, traditionally used in the synthesis of 1D structures such as nanowires and nanorods, can also be applied to the synthesis of colloidal hybrid nanoparticles. Specifically, we show that colloidal Au and Ag nanoparticles can serve as seeds for the growth of colloidal Au-Ge and Ag-Ge heterodimers upon reaction with Ge(HMDS)₂ (Ge(II)bis(hexamethyldisilylamide)) at ∼290 and ∼320 C, respectively. By modifying the size of the seed nanoparticles and the amount of Ge(HMDS)₂, the widths and lengths of the Ge domains can be systematically tuned. Additionally, the Ge domains can serve as site-selective templates for the galvanic deposition of metal nanoparticles, forming trimeric Au-Ge-(Ag)_n nanostructures. This alternate route to colloidal hybrid nanoparticles facilitates the integration of previously inaccessible group IV elements, and it could open the door to the design and synthesis of a wide range of new functional colloidal nanostructures.