Fast synthesis of CdS/CdS host-shell quantum dots

The downconverting photoluminescence with heterogeneous core/shell nanocrystals has been largely investigated. While the homogeneous core/shell quantum dots have seldom been reported. For the small CdS (～2.2 nm) reference quantum dot, it exhibits serious trap emission. In most cases, wider-gap heterogeneous shells of ZnS1or ZnSe2 by slowly hot-injection method are employed to improve the surface passivation and thus improving its photoluminescence performance. The step by step hot-injection method is time-consuming. While the homogeneous CdS shell with fast and controllable epitaxial growth has never been reported. Herein, we demonstrate a flash fabrication method to synthesize the host-shell CdS capped CdS (CdS/CdS). The shell with different layers can be controlled by the amount of precursors added initially. The fluorescence results of the as synthesized host-shell CdS quantum dots, show that the growth of the CdS shell can efficiently remove the surface trap states, leading to high photoluminescence performance. Furthermore, this special core-host shell structure is used to increase the size of CdS, and to adjust the dopant positions inside nanocrystals.3 The fast synthetic procedure and the special host-shell structure present great potentials in preparing large-scale productions of core/shell quantum dots and site-dependent ions doped nanocrystals to avoid lattice mismatch caused by hetero-shell materials, respectively