Morphological evolution of ZnO microspheres from Zn5(OH)8Ac2·2H2O by ultrasonic irradiation method

Abstract

Monodispersed ZnO microspheres were synthesized through ultrasonic irradiation using zinc acetate as a Zn source and triethanolamine as the structure-directing and alkalinity control agent. X-ray diffraction, scanning electron microscopy, transmission electron microscopy and thermo-gravimetric analyses were used to describe the as-prepared products and understand the formation mechanism. The results indicate that the morphology of the products is strongly dependent on the precursor Zn5(OH)8Ac2·2H2O. As the reaction time increased, the precursor, Zn5(OH)8Ac2·2H2O, decomposed into ZnO nanoparticles and simultaneously, ZnO nanoparticles assembled into a spherical structure under ultrasonic irradiation until the precursor, Zn5(OH)8Ac2·2H2O, completely disappeared. UV-vis absorption measurements of the as-prepared products at different stages show that the absorption peaks became sharper and blue-shifted from 422 to 364 nm with the change of composition and morphology. Photoluminescence (PL) measurements show that the intensity of the UV emission increased and that the wavelength first red-shifted and then blue-shifted with the increase of the reaction time, which may be related to the size and crystallinity of the ZnO particles.