Basic principles and current trends in colloidal synthesis of highly luminescent semiconductor nanocrystals

The principal methods for the synthesis of highly luminescent core-shell colloidal quantum dots (QDs) of the most widely used CdSe, CdS, ZnSe, and other A(II) B(VI) nanocrystals are reviewed. One-pot versus multistage core synthesis approaches are discussed. The noninjection one-pot method ensures slow, controllable growth of core nanocrystals starting from magic-size seed recrystallization, which yields defect-free cores with strictly specified sizes and shapes and a high monodispersity. Subsequent injection of shell precursors allows the formation of gradient core-shell QDs with a smooth potential barrier for electrons and holes, without strains or interfacial defects, and, as a consequence, a luminescence quantum yield (QY) approaching 100%. These general approaches can also be applied to semiconductor core-shell QDs other than A(II) B(VI) ones to cover the broad spectral range from the near-UV to IR regions of the optical spectrum, thus displacing fluorescent organic dyes from their application areas.