Chemical transformation of Pt-Fe₃O₄ colloidal hybrid nanoparticles into PtPb-Fe₃O₄ and Pt₃Sn-Fe ₃O₄ heterodimers and (PtPb-Fe₃O ₄)_n nanoflowers

Colloidal hybrid nanoparticles contain multiple domains that are directly fused together through a solid-solid interface, which facilitates synergistic interactions between the components that can lead to enhanced properties, as well as multifunctionality in a single particle. By nucleating one nanoparticle on the surface of another, a growing number of these hybrid nanoparticles can be synthesized. However, to rapidly expand the materials diversity of such systems, alternative routes to heterogeneous seeded nucleation are needed. Here, we show that solution-mediated chemical transformation reactions, which are well established for pseudomorphically transforming colloidal metal nanoparticles into derivative metal-containing phases, can also be applied to colloidal hybrid nanoparticles. Specifically, we show that Pt-Fe ₃O₄ heterodimers react with Pb(acac)₂ and Sn(acac)₂ at 180-200 C in a mixture of benzyl ether, oleylamine, oleic acid, and tert-butylamine borane to form PtPb-Fe₃O₄ and Pt₃Sn-Fe₃O₄ heterodimers, respectively. This chemical transformation reaction introduces intermetallic and alloy components into the heterodimers, proceeds with morphological retention, and preserves the solid-solid interface that characterizes these hybrid nanoparticle systems. In addition, the PtPb-Fe₃O₄ heterodimers spontaneously aggregate to form colloidally stable (PtPb-Fe₃O ₄)_n nanoflowers via a process that is conceptually analogous to a molecular condensation reaction. These reactions add to the growing toolbox of predictable manipulations of colloidal hybrid nanoparticles, ultimately expanding their materials diversity and range of potential applications.