Synthesis and Optical and Electrical Properties of CdS/ZnS Core/Shell Nanorods

The synthesis of CdS/ZnS core/shell nanorods was achieved via a three-step method involving solvothermal preparation of CdS nanorods and then a soft chemical process for functionalization of the CdS surface and subsequent ZnS shell growth. Citric acid was used as the surface functionalizing agent, which ensured the growth of a uniform ZnS shell covering the nanorod surface. The carboxyl groups of citric acid trapped on the surfaces of CdS nanorods with an outward orientation of the -OH functional groups made the surfaces of the nanorods negatively charged, directed the Zn2+ ions to attach to the -OH ions, and helped the formation of a uniform ZnS shell following the addition of a sulfur source. The core/shell nanostructure was confirmed by X-ray study, transmission electron microscopy, and energy dispersive X-ray analysis. The photoluminescence efficiencies and electrical response of the CdS/ZnS core/shell nanorods were significantly enhanced as compared to those of the uncoated CdS nanorods, owing to the effective passivation of the surface electronic states of the CdS cores by the ZnS shell. The present synthesis provides a rational approach to the design of novel core/shell nanomaterials with appealing applications in optoelectronic devices.