Inkjet-printed Pt/WO3 thin film sensor for ppb-level ammonia detection

The development of high-performance ammonia sensors is crucial for environmental monitoring and human health protection. However, traditional conductive metal oxide gas sensors encounter significant challenges such as poor selectivity and high detection limit, mainly raising from their inherent cross-sensitivity and thick gas-sensing layer caused by uncontrollable preparation. Herein, a noble metal platinum-modified tungsten oxide (Pt/WO3) gas sensor is controllably fabricated via inkjet printing technology and magnetron sputtering. In addition to a detection limit toward ammonia as low as 40 ppb, the Pt/WO3 gas sensor demonstrates a good selectivity for ammonia compared to other interfering gases, including acetone, sulfur dioxide, formaldehyde, methane, sulfur hexafluoride, and toluene, with corresponding selectivity coefficients not less than 4.7. The high sensitivity of the gas sensor is mainly attributed to the fact that more electrons can be directly controlled by the adsorbed gas benefiting from the micro-nano thickness of the sensing layer, as well as additional adsorption sites are provided by the Pt modification. Moreover, the catalytic effect of Pt on the reaction between ammonia and oxygen ions further enhances its sensitivity while also improving its selectivity. Our work establishes an important theoretical and experimental foundation for the design of high-performance ammonia sensors.