Design of size-controlled Au nanoparticles loaded on the surface of ZnO for ethanol detection

Abstract

A series of sensing hybrid-materials of Au nanoparticle loaded ZnO nanowires (ZnO NWs) was successfully synthesized by electrostatic spinning and solution processing. Firstly, ZnO NWs were prepared by electrostatic spinning with polyvinylpyrrolidone (PVP) as a solvent. Afterwards, the prepared ZnO NWs were added to HAuCl₄ aqueous solution with adjusted pH to load the Au nanoparticles onto them. Finally, the ZnO NWs were obtained with different sizes of Au nanoparticle loaded via annealing at different annealing temperatures. The X-ray diffraction (XRD) characterization indicates the good crystallinity and purity of the material, while transmission electron microscopy (TEM) images show the different sizes of Au nanoparticles on the ZnO NWs. The gas sensitivity test results show that all the Au-loaded ZnO NW samples show excellent gas sensitivity performance at a low operating temperature, and the loaded Au particles have an obvious influence on the sensing performance. A sensor loaded with large Au particles has a maximum response of 151.86 to 50 ppm ethanol at 200 °C, while a sensor loaded with small Au particles can respond to 50 ppm ethanol at 125 °C up to 108.22. Most importantly, the sensor shows high selectivity and long-term stability against a low concentration of ethanol. To interpret the gas-sensitivity mechanism of different responses under loadings of different Au particle sizes, the spillover effect of noble metal loads and the increase in the Schottky barrier due to the interaction of the noble metal with metal oxide semiconductor electrons are considered to explain the different sensor responses.