Colloidal semiconductor binary II-VI metal (M) chalcogenide (E) quantum dots (QDs) and magic-size clusters (MSCs) have been produced together, sometimes. For the past 35 years, the QD synthesis has been carried out largely as an empirical art, with limited knowledge about the pre-nucleation stage known as the induction period (IP). Recently, we proposed a two-pathway model to explain the co-production. One pathway involves the formation of monomers (Mo) and fragments (Fr), which lead to the nucleation and growth of QDs. This pathway can be addressed by the LaMer model of the one-step based classical nucleation theory (CNT). The other pathway, which we identified a couple of years ago, involves the self-assembly of M and E precursors, followed by the formation of the very MSC precursor compound (PC) from each assembly. The non-classical nucleation theory accounts for this multi-step-based pathway. In this presentation, our latest advances will be discussed on the transformation of the PC to ultra-small QDs with enhanced particle yield as well as to alloy MSCs. The transformation pathways will be explained. Our recent advances bring an in-depth understanding of the coproduction of QDs and MSCs, narrow the knowledge gap on the induction period of QDs, and contribute to the promotion of the nanomaterial synthesis from an empirical art to science.

Evolution of colloidal semiconductor compound magic-size clusters and quantum dots

ACS Fall 2021

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