H₂O₂-Treated ZnO Nanostructures for Humidity-Tolerant O₃ Chemiresistors Operated under Pulsed UV Light Modulation

Severe humidity interference or even poison, especially at room temperature (RT), poses a challenge for the practical application of metal oxide semiconductor (MOS)-based chemiresistors for the monitoring of hazardous O-3 vapor in a real humid air background, owing to the intrinsic hydrophilicity of general MOSs. Herein, we demonstrated that the humiditytolerance performance of an ultraviolet (UV)-activated ZnO chemiresistor (operated at RT) toward O-3 could be drastically improved by a facile H2O2 treatment. The onset of humidity poison starts around a relative humidity (RH) of 30% for a pristine ZnO chemiresistor, while the H2O2-treated ZnO (H2O2-ZnO) chemiresistor enables robust operation under a highly humid air background (90% RH). The response of ppb-level O-3 under humid air could be further enhanced by pulsed UV light modulation (PULM) operation, and a high response (25 for 350 ppb of O-3) could be achieved at RT and 90% RH, which is comparable or even higher than that of the state-of-the-art O3 chemiresistors (including the commercial MQ131 O-3 sensor operated at 200 degrees C). The passivation of surface oxygen vacancy (V-O) defects and reduction of grain size via H2O2 treatment probably enhance the humidity tolerance. Our work may shed light on the design of high-performance humidity-tolerant RT MOS chemiresistors for monitoring hazardous gases in ambient humid air.