Synthesis of butterfly-like ZnO nanostructures and study of their self-reducing ability toward Au3+ ions for enhanced photocatalytic efficiency

Abstract

Zinc oxide (ZnO) nanostructures with diverse morphologies were successfully fabricated via a simple one-step hydrothermal synthesis and subsequent calcination. The formation of butterfly-like ZnO was mainly ascribed to a typical nucleation–growth–assembly process as a result of electrostatic interactions between the nanoparticles and the reconstructed sheets. Au nanoparticles (NPs) created from Au³⁺ ions were deposited on the butterfly-like ZnO without the use of any reducing agents by simply stirring the solution at room temperature. Tartaric acid was present in the ZnO calcined at a low temperature (300 °C), which resulted in the self-reducing ability of ZnO toward the Au³⁺ ions. The Au NPs were closely connected with the ZnO matrix. This close connection resulted in hierarchical ZnO–Au composites with efficient photocatalytic activity for use in environmental remediation. Compared with the pure ZnO sample calcined at 300 °C, the hierarchical ZnO–Au composites showed an enhanced photocatalytic performance toward rhodamine B. The results of photodegradation indicated that the incorporation of the Au NPs drastically increased the photocatalytic efficiency by promoting the separation of the electron–hole pairs created by the absorption of photons.