Tunable Room-Temperature Synthesis of Coinage Metal Chalcogenide Nanocrystals from N-Heterocyclic Carbene Synthons

We present a new toolset of precursors for semiconductor nanocrystal synthesis, N-heterocyclic carbene (NHC)-metal halide complexes, which enables a tunable molecular platform for the preparation of coinage metal chalcogenide quantum dots (QDs). Phase-pure and highly monodisperse coinage metal chalcogenide (Ag2E, Cu2-xE; E = S, Se) QDs are readily synthesized from the direct reaction of an NHC-MBr synthon (where M = Ag, Cu) with alkylsilyl chalcogenide reagents at room temperature. We demonstrate that the size of the resulting QDs is well-tailored by the electron-donating ability of the L-type NHC ligands, which are further confirmed to be the only organic capping ligands on the QD surface, imparting excellent colloidal stability. Local superstructures of the NHC-capped Ag2S QDs are observed by TEM, further demonstrating their potential for synthesizing monodisperse ensembles and mediating self-assembly.