Structural Evolution and Photoluminescence of Zinc-Blende CdSe-Based CdSe/ZnS Nanocrystals

Abstract

Anisotropic heterostructures are of significant importance in creating novel nanomaterials and realizing their application potentials. Here we report a study on structural evolution and photoluminescence of zinc-blende CdSe-based CdSe/ZnS core/shell nanocrystals with variations of the ZnS shell growth. When raising the shell growth temperature, the structure of CdSe/ZnS can be tuned from sphere to near triangle, and to branched ones, including a tetrapod-like structure. But fast interface diffusion and alloying at high growth temperature will corrupt the branched structure and induce a blue shift in the luminescence spectrum. For tetrapod-like CdSe/ZnS nanocrystals, the growth of ZnS exhibits a pattern of first elongating and then branching, which is accompanied by rising, steady, and descending phases of the photoluminescence quantum yield. This study shows the shape tuning and interface alloying of CdSe/ZnS nanocrystals, and reveals that a moderate growth temperature is necessary for obtaining tetrapod-like CdSe/ZnS nanocrystals.