Structural evolution of highly porous/hollow ZnO nanoparticles in sonochemical process

The ZnO porous/hollow nanoparticles which consisted of numerous tiny grains were synthesized after few minutes of ultrasonic irradiation with excellent reproducibility. The fast nucleation and morphological evolution of ZnO nanoparticles could be attributed to high temperature and pressure at the interface between a collapsing bubble and the bulk solution. The water molecules played crucial roles for the formation of porous/hollow structure by facilitating hydrolysis of precursor and reducing system temperature which was favorable for the existence of bubbles as templates. The formation and growth of particles were analyzed systematically by observing the changes of morphology and crystal structure for different processing times. Plausible mechanisms for the morphological evolution were proposed based on a series of time-dependent experiments and characterizations. (C) 2015 Elsevier B.V. All rights reserved.