Conductometric sensor of hierarchical Bi2MoXW1−XO6 microcages in sensing three gases NH3, isopropanol and ethanol

Abstract

Selective detection of multiple reducing gases on one resistive-type gas sensor is desired for highly integrated devices. In this work, we successfully synthesized porous Mo-doped Bi2WO6 microcages via one-step hydrothermal method with triple selectivity in sensing ammonia, isopropanol and ethanol. 1 at% Mo-doped Bi2WO6 microcages increase in resistance once exposed to reducing gases including isopropanol, acetone, CH4, CO and ethanol at room temperature (RT), revealing its p-type sensing nature. On the contrary, an opposite trend of resistance variation is observed in ammonia detection due to the unique sensing mechanism, leading to simultaneous ammonia and isopropanol selective sensing at RT. Ulteriorly, excellent selectivity to ethanol is achieved by modulating the operating temperature to 350 ℃. Interestingly, 1 at% Mo-doped Bi2WO6 microcages exhibit n-type sensing behavior at high temperatures. The corresponding p-to-n conductivity transition resulted from raising the operating temperature is clarified in detail.