Growth of Ga-doped ZnS nanowires constructed by self-assembled hexagonal platelets with excellent photocatalytic properties

A new process for making single crystalline undoped and Ga-doped ZnS nanowires with simple evaporation and condensation procedures on Si and GaN is introduced. The process does not need additional catalysts or precursors. The growth mechanism is studied using transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. TEM images show that the undoped ZnS nanowires exhibit an ordinary straight morphology, whereas the Ga-doped nanowires are composed of aligned hexagonal platelets, connected in the center into nanowires to maximize surface area. The Ga 2p3 and S 2p peaks in the XPS results confirm the presence of Ga doping in the form of Ga-S bonding. Raman spectra show that the ZnS LO peak is red-shifted from 349 to 347 cm(-1), indicative of a tensile stress caused by the Ga dopants. The growth mechanism and photocatalytic activity of the Ga-doped ZnS nanowires are discussed. We also demonstrate the excellent photocatalytic activity of Ga-doped ZnS nanowires as compared to those of undoped ZnS nanowires and Ga-doped ZnS nanosheets.