NANOSTRUCTURED MOLYBDENUM TRIOXIDE (MoO3) FOR THE DETECTION OF AMMONIA GAS (NH3) AT ROOM TEMPERATURE

Abstract

The effect of synthesis method and condition on the gas sensing properties of that α-MoO3 was studied, with the hydrothermally synthesized α-MoO3 capable of NH3 detection at room temperature. Growth mechanism was discussed and analysed. Subsequently, the effects of annealing in air and vacuum was examined, with the vacuum annealed gas sensor achieving a much lower detection limit compared to as-synthesized and air annealed samples. A sensing mechanism was proposed to explain the initial and subsequent improvement of NH3 detection at room temperature. In addition, NH3 treatment was performed to modify the surface chemistry of α-MoO3. The resultant sensor was able to detect NH3 concentrations down to 470 ppb at room temperature and relative humidity of 70%, which is viable to detect breath levels of NH3. A modified sensing mechanism was presented to explain the improved performance, paving the way for the realization of portable breath analysis.