ZnO nanoswords and nanopills: Hydrothermal synthesis, characterization and optical properties

Nanostructured hexagonal zinc oxide pills and swords-like were hydrothermally synthesized using zinc sulfate heptahydrate (ZnSO4·7H2O) as an inorganic precursor and adipic acid (HOOC(CH2)4COOH) as a structure-directing agent. The structure, the crystallinity, the morphology and the composition of the materials were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). XRD study demonstrated the existence of wrutzite ZnO of high degree of crystallinity with crystallite size in the range of 70–80 nm. The optical properties of the as-synthesized ZnO were investigated by UV–visible absorption and room temperature photoluminescence (RTPL). The band gap for ZnO nanswords and nanopills was found to be 3.25 and 3.27 eV, respectively.