Transformations of Magic-Size Clusters via Precursor Compound Cation Exchange at Room Temperature

The transformation of colloidal semiconductor magic-size clusters (MSCs) from zinc to cadmium chalcogenide (ZnE to CdE) at low temperatures has received scant attention. Here, we report the first room-temperature evolution of CdE MSCs from ZnE samples and our interpretation of the transformation pathway. We show that when prenucleation stage samples of ZnE are mixed with cadmium oleate (Cd(OA)2), CdE MSCs evolve; without this mixing, ZnE MSCs develop. When ZnE MSCs and Cd(OA)2 are mixed, CdE MSCs also form. We propose that Cd(OA)2 reacts with the precursor compounds (PCs) of the ZnE MSCs but not directly with the ZnE MSCs. The cation exchange reaction transforms the ZnE PCs into CdE PCs, from which CdE MSCs develop. Our findings suggest that in reactions that lead to the production of binary ME quantum dots, the E precursor dominates the formation of binary ME PCs (M = Zn or Cd) to have similar stoichiometry. The present study provides a much more profound view of the formation and transformation mechanisms of the ME PCs.

Automated summary

The present study reports the room-temperature evolution of cadmium chalcogenide magic-size clusters (MSCs) from zinc chalcogenide samples and proposes a transformation pathway. It is shown that the mixing of cadmium oleate with precursors of zinc chalcogenide MSCs results in the formation of cadmium chalcogenide MSCs. The findings suggest that in reactions leading to the production of binary metal chalcogenide quantum dots, the chalcogenide precursor dominates the formation of binary metal chalcogenide precursors with similar stoichiometry, providing a deeper understanding of the formation and transformation mechanisms of metal chalcogenide clusters.