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.