Highly selective and sensitive WO3 nanoflakes based ammonia sensor

Tungsten oxide (WO3) nanoflakes were grown directly on a seed layer-free Al2O3 substrate by a simple hydrothermal method. Process temperature and time were optimized for nanoflake formation on Al2O3 substrate. Samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) techniques for structural, morphological and chemical composition analysis, respectively. Sensor measurements toward some volatile organics (VOCs) such as acetone, ethanol; and inorganic molecules such as ammonia (NH3), hydrogen cyanide (HCN) and nitrogen dioxide (NO2) were performed by varying gas concentrations at different temperatures. WO3 nanoflakes exhibited superior sensor response toward ammonia gas at a concentration as low as 1 ppm. The superior cross sensitivity and very high response to ammonia allow the developed sensor to be used as a potential platform for low level ammonia detection applications.