ZnS nanoparticle-assisted synthesis and optical properties of ZnS nanotowers

Tower-like ZnS nanostructures are facilely synthesized via a ZnS nanoparticle-assisted vapor deposition route. Scanning electron microscopy and transmission microscopy observations show that the tower-like structures are likely to be made up in a layer-by-layer fashion and consist of quasi-hexagonal plates. The growth of nanotowers is initiated by the preferred nucleation on the ZnS nanoparticles precoated on Si substrate, followed by alternate two-dimensional growth of hexagonal plates/layers inside nanotowers and one-dimensional stacking in the direction perpendicular to the plates/layers via vapor-solid growth processes. Such nanotowers, due to the existence of many interfacial defects, display distinct photoluminescence and Raman spectra from nanoplates prepared without the assistance of ZnS nanoparticles. The photoluminescence spectra of the nanotowers show two strong emission bands located at 394 and 592 nm. In Raman spectra, two anomalous modes at 233 and 488 cm(-1) are observed.