Fabrication and luminescent properties of c-axis oriented ZnO-ZnS core-shell and ZnS nanorod arrays by sulfidation of aligned ZnO nanorod arrays

In this paper, we report the preparation of vertically aligned ZnO-ZnS core-shell and ZnS nanorod arrays with crystallographic orientation along the c-axis by sulfidation of aligned ZnO nanorod arrays. The ZnO nanorod arrays were prepared by a surfactant assisted soft chemical method on a sol-gel derived ZnO thin film. Partial conversion of the ZnO nanorod surface to ZnS at 400 degrees C in an H2S and argon gas mixture produces ZnO-ZnS core-shell structures, whereas the complete conversion at 600 degrees C produces well-aligned ZnS nanorods. The influence of the sulfidation time and annealing temperature on the conversion of ZnO nanorods to ZnO-ZnS core-shell nanorods is investigated. TEM studies revealed that the sulfidation process begins at the surface of the ZnO nanorods, which gradually increase inward, retaining the morphology and following the crystal orientation of the ZnO core. The nanostructures showed enhanced UV emission properties. The described procedures open a way to convert a microstructured material into chemically more stable materials with the same morphology, thus leading to a diversification of possible applications.