Temperature-Controlled Chemoselective Editing of Heterostructured Nanorods Using a Broad-Scope Reverse Cation Exchange Reaction

Forward and reverse cation exchange reactions transform simple and synthetically accessible nanoparticles of copper sulfide, Cu_1.8S, into a large library of compositionally and morphologically complex products by converting them to or from other metal sulfides, respectively. However, the scope of reverse, or "back-exchange", reactions is limited, which restricts the diversity of nanoparticle precursors and products. Here, we introduce a Cu⁺ back-exchange reaction that drives the extraction of traditionally unreactive and hard <i>M</i>²⁺ and <i>M</i>³⁺ cations in metal sulfides by coordinating them with oleylamine, a hard base. ZnS, CuInS₂, Co₉S₈, and CuGaS₂ nanorods react with CuBr in oleylamine to form Cu_1.8S, but at different threshold temperatures that allow distinct regions of heterostructured nanorods containing them to be selectively converted. Additionally, tapered hexagonal prism CuInS₂ nanoparticles were back-exchanged to a previously unreported morphology of Cu_1.8S, which was subsequently converted into a library of derivative metal sulfide nanoparticles. These chemoselective reactions edit the compositions in targeted regions of multicomponent nanoparticles, providing a powerful design tool for the retrosynthesis of complex nanoparticles.