Trisodium citrate as bridging and suppressing agent to control synthesis of ZnO hollow hierarchical microspheres and their photocatalytic properties

A facile and low-cost trisodium citrate-assisted hydrothermal method was used to fabricate ZnO hollow nanostructures with different morphologies, including ZnO hollow hierarchical microspheres with uniform nano-sheets, ZnO hollow hierarchical microspheres with small pieces particles and ZnO hollow hierarchical microspheres with thin mutual crisscross nano-sheets. The structures and morphologies of the as-obtained products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM). Trisodium citrate played an important role as a bridging and suppressing agent in the formation of ZnO hollow hierarchical microspheres. The growth mechanism of ZnO hollow hierarchical microspheres based on Ostwald ripening process and alkali etching process was proposed. The photocatalytic activities of as-prepared products were also evaluated with methyl orange (MO) as the probe molecules under UV light. The results revealed that ZnO hollow hierarchical microspheres with thin mutual crisscross nano-sheets after annealing at 300 °C exhibited the highest photocatalytic activity.