Controllable synthesis of W18O49 nanoneedles for high-performance NO2 gas sensors

Abstract

Controlling the morphology of W18O49 nanostructures is an effective way to achieve high NO2-sensing performance. Herein, we describe the synthesis of W18O49 nanostructures via a facile solvothermal process by reacting a WCl6 precursor with a reducing agent. Several well-designed experiments were performed to realize the morphology-controlled synthesis of W18O49 nanostructures by adjusting solvent types, WCl6 dosages, solvothermal temperatures and times. One-dimensional (1D) nanoneedles composed of monoclinic W18O49 with preferential growth along the (010) direction, which expose more surface oxygen vacancies and demonstrate a significant benefit for improved gas sensing performance, were obtained under optimized synthetic conditions. Subsequently, the W18O49 nanoneedles displayed a high response to NO2 with excellent dynamic response-recovery characteristics at the optimal operating temperature of 160 °C. Moreover, the W18O49 sensor detected NO2 in a wide range of concentrations (0.2–500 ppm) and showed good selectivity and long-term stability. The gas sensing ability of W18O49 nanoneedles toward NO2 is discussed, and rich oxygen vacancies, 1D needle-shaped nanostructures, and high BET surface area contributed to their outstanding gas sensing performance.