Au-mediated growth of wurtzite ZnS nanobelts, nanosheets, and nanorods via thermal evaporation

In this study, we demonstrate the large-scale synthesis of wurtzite ZnS nanostructures by simple thermal evaporation of ZnS powder in the presence of Au catalysts at 970 degreesC. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) analyses demonstrated that the ZnS nanostructures consisted of nanobelts, nanosheets, and nanorods with a hexagonal wurtzite structure. The nanobelts have lengths ranging from tens to hundreds of micrometers, thicknesses of tens of nanometers, and widths ranging from hundreds of nanometers to the order of micrometers. The preferred growth axis of single crystalline nanobelts was found to be [01-11] or [0001]. Large single crystalline nanosheets also formed with flat surfaces. ZnS nanorods grew preferably in the [0001] direction with uniform diameters, with their ends attached to Au particles. Small amounts of bicrystal and tricrystal nanobelts were also observed. The formation of ZnS nanostructures with various morphologies was mainly due to the local concentration difference of ZnS vapor. The growth process was proposed on the basis of vapor-liquid-solid (VLS) and/or vapor-solid (VS) crystal growth mechanisms. Room-temperature photoluminescence measurements showed that the synthesized ZnS nanostructures had a strong green emission band at a wavelength of 522.5 nm, which may be ascribed to deep-level emissions induced by defects and/or Au impurity.