Revisited Wurtzite CdSe Synthesis: A Gateway for the Versatile Flash Synthesis of Multishell Quantum Dots and Rods

Quantum dot core shell structures are essential to superior optical properties. However, Cd-based quantum dots grown from wurtzite CdSe cares still suffer from irreproducibility due to gel formation during the core synthesis. Moreover, state-of-the-art shelling procedures often remain time-consuming. We report here (1) a new procedure of the wurtzite CdSe quantum dot synthesis which eliminates the phosphonic anhydride contamination and (2) the improvement and generalization of the flash synthesis for the growth of highly luminescent multishell heterostructures. The high versatility of the flash procedure enables the epitaxial shelling of wurtzite CdSe by CdS, ZnS and even CdZnS alloys, resulting in a significant enhancement of their photoluminescence efficiency. Thanks to a modification of the CdSe/CdS dot-in-rods synthesis to prevent tip-to-tip connections, the flash procedure could also be extended to these anisotropic structures for the growth of multishell nanorods as well. The high quality optical properties of these multishell flash heterostructures are of great interest for applications ranging from lighting and displays to long-term cell labeling.