Prenucleation Clusters in Shell Formation of Photoluminescent Core/Shell Quantum Dots of Heavy‐Metal‐Free ZnTeSe/ZnSe

It remains largely unknown whether stable prenucleation clusters (PNCs) appear in the conventional shell synthesis for photoluminescent (PL) core/shell quantum dots (QDs) of ZnTeSe/ZnSe. The heavy‐metal‐free QDs have demonstrated great potential in various applications. For the first time, we utilize a prenucleation‐stage sample of ZnSe containing the PNC to grow a ZnSe shell on PL ZnTeSe QDs. The ZnSe sample was prepared with common chemicals of zinc oleate (Zn(OA) 2 ) and tri‐ n ‐octylphosphine selenide (SeTOP). In the conventional mixture of PL ZnTeSe QDs + Zn(OA) 2 + SeTOP, brighter ZnTeSe/ZnSe core/shell QDs develop too. We hypothesize that Zn(OA) 2 and SeTOP undergo chemical self‐assembly. The resulting ZnSe PNC transforms into monomers (Mos), and the shell evolves via one‐by‐one addition of ZnSe monomers. Our study not only introduces a new avenue to shell growth, but also brings compelling evidence that chemical self‐assembly occurs in mixtures of individual cation‐ and anion‐containing molecules; the conversion sequence is molecule–PNC–Mo–QD without QDs, while is molecule–PNC–Mo–shell with QDs.