Synthesis of hierarchical 3D porous ZnO microspheres decorated by ultra-small Au nanoparticles and its highly enhanced acetylene gas sensing ability

Abstract

In this paper, ultra-small Au nanoparticles (1–2 nm) were successfully decorated on the surface of three-dimensional porous wool like ZnO microspheres through a facile, surfactant-free and green precipitation manner. The ZnO microspheres were synthesized via a hydrothermal method. The crystal structure and morphology of the samples as-synthesized were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The results showed that quantities of Au nanoparticles of which the diameter ranged about 1–2 nm were distributed evenly on the surface of ZnO microspheres. Gas sensing measurements revealed that the ZnO microspheres decorated with ultra-small Au nanoparticles (Au-ZnO microspheres) showed ultrasensitive and selective detection to acetylene. The Au-ZnO microspheres exhibited ultra-higher response to acetylene (311.3–100 ppm acetylene) at a lower optimal working temperature (183.5 °C) compared with pure ZnO microspheres. Meanwhile, The Au-ZnO microspheres displayed a fast response/recovery speed (about 1 s and 20 s, respectively). Besides, the Au-ZnO microspheres also showed good stability and repeatability over a two-month testing period. Furthermore, the formation of schottky junction, the catalytic effect of Au nanoparticles and the physical advantages of the nanomaterial in size and structure could be three dominant factors to the superior acetylene sensing performance.