Systematically controlled synthesis of shape-selective ZnO superstructures via sonochemical process

Abstract The controllable synthesis of shape-selective ZnO superstructures using a facile method is still great demand. Herein, ZnO nanostructures with different morphology were prepared via a simple sonochemical route with the help of ethylene glycol, such as sphere-like ZnO, twin-sphere-like ZnO, and bouquet-like ZnO. Control experiments were carried out to explore the growth mechanism of ZnO. The water content, ultrasound time, alkaline medium, and reaction pH were key factors for the morphology control of ZnO. Thereinto, the action of water content and ultrasound time could be regarded as the main factor. A formation mechanism of ZnO superstructures based on relocation, growth, and self-assembly of ZnO grains was proposed. Choosing the ammonia water as pH adjustment, the OH– ions were reacted with Zn2+ to form ZnO nuclei rapidly under the condition of pH = 8. Under the inducement of different water content and ultrasound time, the ZnO crystals were turned into irregular nanospheres, nanorods, or hexagonal prism. When the water content was 50%~70%, the ZnO units could be assembled into bouquet-like ZnO. Interestingly, ZnO superstructures with similar morphology could be obtained by the complementary of water content and ultrasound time, meaning that the morphology of ZnO prepared at high water content was the same as that prepared at long ultrasound time or vice versa.