Aqueous Synthesis of Zinc Blende CdTe/CdS Magic-Core/Thick-Shell Tetrahedral-Shaped Nanocrystals with Emission Tunable to Near-Infrared

We demonstrate the synthesis of near-IR-emitting zinc blende CdTe/CdS tetrahedral-shaped nanocrystals with a magic-sized (similar to 0.8 nm radius) CdTe core and a thick CdS shell (up to 5 nm). These high-quality water-soluble nanocrystals were obtained by a simple but reliable aqueous method at low temperature. During the growth of the shell over the magic core, the core/shell nanocrystals change from type I to type II, as revealed by their enormous photoluminescence (PL) emission peak shift (from 480 to 820 nm) and significant increase in PL lifetime (from similar to 1 to similar to 245 ns). These thick-shell nanocrystals have a high PL quantum yield, high photostability, compact size (hydrodynamic diameter less than 11.0 nm), and reduced blinking behavior. The magic-core/thick-shell nanocrystals may represent an important step toward the synthesis and application of next-generation colloidal nanocrystals from solar cell conversion to intracellular imaging.