Catalytic properties of nanosized zinc aluminates prepared by green process using Opuntia dilenii haw plant extract

Abstract

Various nanosized zinc aluminate (ZnAl2O4) samples were prepared by a conventional and a microwave method both with and without using Opuntia dilenii haw plant extract, and were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), high resolution scanning electron microscopy (HRSEM), energy dispersion scanning (EDX), temperature dependent conductance measurements, thermoelectric power measurements, ultraviolet-visible (UV-Vis) diffuse reflectance spectroscopy, and photoluminescence spectroscopy. The formation of a pure ZnAl2O4 phase was confirmed by XRD and FT-IR. A change in morphology from nanosized plates to nanosized sheets with, respectively, the conventional and microwave heating methods was clearly shown by HRSEM. UV-Vis diffusion reflectance spectroscopy measured the band gaps of ZnAl2O4 nanosized plates and nanosized sheets as 3.5 and 3.9 eV, respectively. The synthesized ZnAl2O4 was single crystalline and has three photoluminescence emissions at 482, 528, and 540 nm. ZnAl2O4 nanosized sheets prepared by the microwave method showed higher catalytic activity for the oxidation of benzyl alcohol (85% conversion) than ZnAl2O4 nanosized plates prepared by the conventional method (60% conversion). © 2013, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.