Multiple-layered structure of obelisk-shaped crystalline nano-ZnO prepared by sol–gel route

Zinc oxide nanopowders were synthesized bythe simple sol–gel method from an ethanol solution of zincnitrate hexahydrate. Structural and surface morphologicalinvestigations were carried out using X-ray diffraction(XRD), high-resolution transmission electron microscopy(HRTEM), scanning electron microscopy, Fourier transforminfrared spectroscopy (FTIR) and ultraviolet–visible(UV–Vis) spectrophotometry analyses. XRD patternshowed that the zinc oxide nanoparticles exhibited hexagonalwurtzite structure. A multiple-layered structure ofobelisk-shaped ZnO nanoparticles was achieved after calcinations.The average particle size of ZnO was around20 nm as estimated by direct HRTEM observation. Thesize of sphere-like shaped ZnO nanoparticles was measuredin the range of 20–80 nm and the size of pyramid-likeshaped annealed samples was achieved in the range of40–100 nm with less agglomeration. The energy dispersivespectroscopy spectrum showed peaks of zinc and oxygen.The sharp peaks in FTIR spectrum determined the Zn–Ostretching and absorbance peak of UV–Vis spectrumshowed the wide bandgap energy of 3.35 eV.