Ultrasensitive and Selective MEMS Xylene Gas Sensor Based on CuO/WO3 Hierarchical Structure

Abstract

A p-n heterostructure has been proved as a good strategy to enhance the gas sensing performance of metal oxide semiconductor (MOS). Here, we reported a xylene gas sensor based on CuO/WO3 p-n hierarchical structure. CuO/WO3 were prepared by a two-step route. First, WO3 was synthesized by a reaction between CaWO4 and HNO3 under reaction condition was at 25˚C for 18 h, and then CuO/WO3 were prepared by immersion pyrolysis method. The prepared hierarchical CuO/WO3 hollow microspheres features an ordered assembly of two dimensional (2D) nanosheets with the thickness about 20 nm. Gas sensing tests displayed CuO/WO3 sensor had a good linearity property between the sensing responses and xylene concentrations range from 0.3 ppm to 50 ppm, and CuO/WO3 -3 (the mass ratio of CuO to WO3 is 3) sensor exhibited the highest response of 304.8 toward 20 ppm xylene gas at the optimal working temperature of 260˚C. Furthermore, it is obvious that CuO/WO3 -3 not only possessed superior response and recovery properties of 3 s and 6 s under 20 ppm xylene gas, respectively, but also showed outstanding selectivity and stability. The advantages of high sensitivity, simple manufacturing and outstanding selectivity indicate the promising application of CuO/WO3 xylene sensors in the field of air-quality and environmental monitoring, and p-n heterostructure can significantly enhance the gas-sensing performance of metal oxide semiconductor. Figure 1