Optical properties of ZnS–CdS alloy quantum dots prepared by a colloidal method

We have investigated optical properties of ZnS–CdS alloy (Zn1−xCdxS) quantum dots (QDs) prepared by a colloidal method. We succeeded in the preparation of Zn1−xCdxS QDs for all alloy compositions of x between 0 and 1. Furthermore, the reduction of the size-distribution width was achieved by using a size-selective photoetching treatment. The intensity of the band-edge luminescence was remarkably increased by modifying the surface with a Cd(OH)2 layer. The surface modification also causes drastic changes of decay profiles of the band-edge luminescence, reflecting considerable suppression of nonradiative decay processes. These results clearly demonstrate the success in the preparation of the size- and surface-controlled Zn1−xCdxS QDs.