How to suppress the development of magic-size clusters (MSCs) in reactions of colloidal semiconductor quantum dots (QDs) remains an outstanding challenge. Using the reaction of Cd(OAc)2/OLA (made from cadmium acetate and oleylamine) and TeTOP (tri-n-octylphosphine telluride) as a model system, we show that when tri-n-octylamine (TOA) was used as a reaction medium, MSCs did not form, but QDs did. When OLA was used, MSCs and QDs evolved together. To explain the effect of reaction media, we suggest that prenucleation clusters (PNCs) form first via chemical self-assembly of Cd(OAc)2/OLA and TeTOP. Afterward, the PNC-QD and/or PNC-MSC transformation occurs. The former is favored by a less polar environment (TOA), while the latter by a more polar environment (OLA). Paving the avenue to the inhibition of MSCs in the QD synthesis, this work brings deeper insight into the two-step model, showing that the reaction medium affects the formation and transformation of the PNC.
Liu et al. (2026) studied this question.