A Simple Route to the Synthesis of Core/Shell Nanoparticles of Chalcogenides

In this work, we report the synthesis of CdSe/CdS, CdSe/ZnS, and CdSe/ZnSe core/shell and CdSe/CdS alloy nanoparticles using bis(hexyl(methyl)dithio-/-diselenocarbamato)cadmium(II)/zinc(II) compounds as single-source precursors. We compare the optical properties of the core/shell nanoparticles in relation to those of the parent organically capped binary nanoparticles. We also compare the properties of CdSe alloys to those of the CdSe particles and core/shell structures. The absorption spectra of CdSe/CdS, CdSe/ZnS, and CdSe/ZnSe show red shifts of 0.020, 0.038, and 0.046 eV, respectively, with respect to the parent CdSe nanoparticles. Photoluminescence spectra (λexc = 400 nm) CdSe/CdS (622 nm), CdSe/ZnS (620 nm), and CdSe/ZnSe (617 nm) show emissions close to the absorption band edge. The emission maximum of the core/shell materials shows red shifts in relation to the emission maximum of CdSe consistent with the red shifts in the absorption spectra. The intensity of the emission maximum is considerably increased in the core/shell structure as compared to the parent materials. The X-ray diffraction pattern of the CdSe−CdS composite are broad and poorly defined. The HRTEM micrographs of the core/shell nanoparticles show well-defined, spherical particles with larger diameters than the particles of the parent material.