A Prenucleation-Stage Sample of ZnSe Assisting Lower-Temperature Shell Growth on CdSe Magic-Size Clusters via Monomer...

Surface passivation of colloidal semiconductor nanocrystals is usually performed at elevated temperatures with undefined changes to core nanocrystals. Using a prenucleation-stage sample of ZnSe-containing clusters (prepared at 160 °C), the first surface passivation is reported at 25 °C, which transforms photoluminescent (PL)-inactive CdSe magic-size clusters (MSCs) to PL-active ones. The PL-inactive CdSe MSCs display an absorption doublet peaking at 421/450 nm. With a similar absorption doublet, the resulting PL-active CdSe/ZnSe MSCs exhibit a sharp PL signal at 460 nm. It is argued that the Zn-Se bond formation is decoupled from the growth of the ZnSe shell, which proceeds via the addition of ZnSe monomers. The chemical transformation at room temperature implements the principle of isodesmic reactions where M-Se bonds cleaved in the reactant are similar to those formed in the product. The present study paves an avenue for surface passivation under mild conditions, providing an in-depth understanding of the shell formation mechanism.