Ultrasound-Assisted Synthesis of Mesoporous ZnO Nanostructures of Different Porosities

Mesoporous ZnO nanoparticles with average pore sizes of 2.5 and 14.3 nm were prepared by ultrasonic hydrolysis of zinc acetate at different ultrasound powers. Morphology, crystallinity, and porosity of the materials have been studied using transmission electron microscopy (TEM), X-ray diffraction (XRD), and BET nitrogen adsorption. Whereas a moderate ultrasound power favored the synthesis of well-crystalline mesoporous ZnO nanoparticles of triangular and hexagonal morphologies with very low density of lattice defects and small pore size, high ultrasound power generated mesoporous ZnO nanoparticles of arbitrary morphology with higher density of lattice defects. Photoluminescence behaviors and the mechanisms of formation of the two types of porous nanostructures are discussed.