Mechanistic Study of Galvanic Replacement of Chemically Heterogeneous Templates

Galvanic replacement is a useful method for synthesizing architecturally complex multimetallic nanostructures from monometallic templates. The oxidation of monometallic templates by ions of a more noble metal is well-studied; however, chemically heterogeneous templates offer more than one type of reaction site and potentially structurally more complex materials. Yet, mechanistic studies with such templates are limited. Here, the reactivities of Ag and Pd in Janus-style AgPd dimers are compared when ions capable of oxidizing both metals are introduced. This study reveals (1) the selectivity of galvanic replacement with dimer templates, (2) cooperativity between galvanic replacement in one dimer domain and solid-state diffusion in another domain, and (3) similar replacement mechanisms for different redox pairs. Specifically, Au ions almost exclusively replace Ag before exchange with Pd is evident, and Ag oxidation facilitates diffusion of the remaining Ag into the Pd domain. These results provide mechanistic insight into the kinetically linked processes involved in the galvanic replacement of complex multimetallic templates and demonstrate the importance of understanding these interactions to achieve structural and compositional control over the resulting nanostructures.