Control of Surface Potential in WO3 Gas Sensors Using UV Light

We introduce the first control of surface potential (SP) in MOX gas sensors using UV light (367 nm). The control is based on sigma-delta modulation implementing a sliding mode control on the surface potential of the sensor. Measurements are presented using a sensor made of WO
₃
nanowires under mild heating at 125 °C. Without control, the sensor shows no response to ethanol. Under control, the detection limit is beyond 2 ppm with a response time below 5 minutes. For NO
₂
, the response time is reduced by a factor of 10. By operating the sensor at constant SP it is possible to improve both dynamics and sensitivity. This new methodology applies generally to a wide range of gas sensitive materials and transducing elements.