The 'flash' synthesis: advances towards multi-shell quantum dots and nanorods

Colloidal nanomaterials such as semiconductor quantum dots offer unique optical properties, including tunable emission and high photoluminescent quantum yield. However, surface defects and poor surface passivation lead to non-radiative recombination and the on-off blinking of their emission. Core-shell structures, such as CdSe/CdS quantum dots, have therefore attracted a lot of attention, and especially “giant” ones lately, as a better confinement of the excited charge carriers with appropriate larger band gap materials gives higher photoluminescent quantum yield and nonblinking nano-emitters. In this contribution, we present our progress on the “flash” synthesis, initially developed for the fast growth of such giant shells, and highlight its great versatility for the preparation of multi-shell quantum dots and nanorods. Firstly, we report the improved quality and purity of the wurtzite CdSe nanocrystal cores which is the indispensable first step in development of high quality multi-shell nanocrystals. Secondly, we report the advances made on the growth of multi-shells, including CdS, ZnS and even alloyed CdZnS layers, both on isotropic (quantum dots) and anisotropic (nanorods) heterostructures. Thanks to their excellent optical characteristics, these ”flash” grown colloidal nanomaterials have already been employed in a broad range of applications, from lighting and display to lasing and bioimaging applications, which will be showcased in this contribution