Morphology control and characteristics of ZnO/ZnS nanorod arrays synthesised by microwave-assisted heating

The morphology control investigations on ZnO/ZnS core/shell nanorod fabricated by microwave-assisted in-situ surface sulphidation of ZnO nanorod arrays is presented. First, the ZnO nanorod arrays are grown on ZnO/Si substrate by microwave heating of a mixed zinc nitrate hexahydrate and hexamethylenetetramine precursors in deionised water. Then, the grown ZnO nanorod arrays on ZnO/Si substrate are immersed in thioacetamide (TAA) aqueous solution to undergo sulphidation process to form ZnS shell on ZnO core. The morphological, structural, and optical characteristics of the as-prepared ZnO nanorods and ZnO/ZnS core/shell nanorods are investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL) measurements, respectively. The SEM images and XRD patterns show that the ZnS shell becomes thicker due to more and more ZnS nanoparticles formed with increasing the concentration of TAA solution. The PL spectra demonstrate that the thicker ZnS shell results in more oxygen vacancies occupied by S atom, and would decrease the intensity ratio of the deep-level emission to the ultra-violet emission for the ZnO/ZnS core/shell nanorods synthesised with the higher concentration of TAA solution.