Superior sensor performance from Ag@WO3 core–shell nanostructure

Abstract

WO3, Ag–WO3 mixture and Ag@WO3 core–shell nanostructure materials were prepared by a hydrothermal process. Material characterization included UV–Vis spectroscopy, XRD, XPS, and TEM imaging. Gas sensors fabricated using the samples were mainly characterized by the response to alcohol vapor. It was found that the Ag@WO3 core–shell nanostructure provides greatly enhanced chemical sensor performance. Specifically, the sensor response towards 500ppm alcohol vapor increases from 44 for pure WO3 and 52 for Ag–WO3 mixture to 154 for the Ag@WO3 core–shell structure; response and recovery time are shortened considerably from 3 and 15s for pure WO3, 12 and 7s for the Ag–WO3 mixture to 2 and 4s for the Ag@WO3 core–shell nanostructure. Moreover, optimum sensor working temperature lowered from 370°C to 340°C. It appears that the Ag@WO3 core–shell nanostructure results in an effective Schottky junction enhanced sensor while the Ag–WO3 mixture does not. The significant downshift in the Ag 3d XPS chemical shift for the Ag@WO3 core–shell nanostructure sample confirms that the sensor performance improvement is due to Schottky junction formation at the Ag/WO3 interface.