Competitive reactivity drives size- and composition-focusing in multimetallic nanocrystals

Multimetallic nanocrystals (NCs) offer distinctive properties driven by synergistic interactions among their constituent metals. Although colloidal chemistry enables control over size and composition, competing reactivities among metal precursors often complicate the synthesis of complex NCs. In this study, we systematically elucidate how the competitive reactivity of different metals in solution can be exploited to synthesize uniform pentametallic NCs despite numerous competing pathways. Mechanistic studies reveal heterodimers as key intermediates that mediate further metal incorporation through selective nucleation. Notably, the addition of more metals suppresses homogeneous nucleation, resulting in size- and composition-focusing to produce complex NCs with distinct multimetallic domains. When supported, these NCs show excellent thermal stability and catalytic activity for ammonia decomposition, offering a promising strategy for designing complex nanomaterials for energy-related applications.