Microwave-assisted hydrothermal synthesis of ZnO powders with different reagents

C.S. Xavier, A.P. de Moura, M.S. Li, E. Longo, J.A. Varela, S. Cava
Universidade Federal de Pelotas, BR

Keywords: zinc oxide, microwave-hydrothermal, hexagonal structure, photoluminescence

Summary:

Zinc oxide (ZnO) is an exceptionally important semiconductor with a direct wide band gap (3.37 eV) and large excitation binding energy (60 meV) at room temperature [1]. In this work, zinc oxide powders were synthesized by microwave-assisted hydrothermal method in basic medium. The zinc oxide crystalline structure characterized using X-ray diffraction (XRD) where all diffraction peaks can be indexed as ZnO hexagonal structure that are consistent with the respective JCPDS card Nº 36-1451 This result could be also confirmed by micro-Raman scattering (MRS) analysis. In the field-emission scanning electron microscopy (FEG-SEM) image, Figure 3, can be observed flower-like ZnO nanostructures synthesized with zinc nitrate, acetate, sulphate and KOH at 130ºC for 1 h. The high-magnification FEG-SEM image reveals that these nanostructures are made up of ZnO plates. The powder was analyzed by ultraviolet visible absorption spectroscopy (UV-vis) which was employed to determine the optical band gap of this material. An orange PL emission when excited by 350 nm wavelength at room temperature was observed in the different powders.