Heterojunctions of ZnO-Nanorod-Decorated WO₃ Nanosheets Coated with ZIF-71 for Humidity-Independent NO₂ Sensing

Abstract

NO2 is a very dangerous and toxic gas and is prone to cause acid rain in high humidity environments, so it is essential to prepare a real-time monitoring and humidity immunity NO2 sensor. WO3 nanomaterials are commonly applied to detect NO2, but their poor immunity to humidity is still a critical limitation for the application. ZnO-nanorod-decorated WO3 nanosheets coated with ZIF-71 (ZnO@ZIF-71/WO3) composites prepared by an in situ growth method displayed excellent gas sensing performance and good humidity immunity to detect NO2. Compared to WO3 nanosheets and ZnO-nanorod-decorated WO3 nanosheets (ZnO/WO3) heterojunction composites grown on ceramic substrates in situ, ZnO@ZIF-71/WO3 presented excellent selectivity, good long-term stability, and a remarkably high response of about 947.96 to 100 ppm NO2 at 180 °C, which is 3.07 times higher than that of the ZnO/WO3 sensor and 4.59 times higher than that of the pure WO3 sensor. Even at a relative humidity of 85%, the response of ZnO@ZIF-71/WO3 to NO2 remained essentially constant. The functional ZIF-71 layer not only improved the humidity immunity of ZnO@ZIF-71/WO3 but also enhanced the sensitivity and selectivity performance to NO2 at low operating temperatures. The ZnO@ZIF-71/WO3 sensor still provided a response of 88.41 to 100 ppm NO2 at room temperature.

Delafossite CuGaO2-Based Chemiresistive Sensor for Sensitive and Selective Detection of Dimethyl Disulfide

“…Due to the inherent hydrophilicity of general n-type MOSs (SnO 2 , WO 3 , ZnO, etc. ), preferential adsorption on the MOS surface easily occurs, which easily causes the response deterioration (or even poison) under the (high) humid air background. − , We have examined the humidity (0–90% RH) influence on the (10 ppm) DMDS responses at 140 °C. Strikingly, the CuGaO 2 sensor shows a satisfactory humidity resistance performance toward DMDS (∼13.4% decay from dry to 90% RH air; Figure a,b), and the good selectivity could be maintained under humidity conditions (Figures S8 and S9).…”

“…Third, due to inherent hydrophilicity of general MOS sensing materials (i.e., SnO 2 , ZnO, WO 3 , etc. ), humidity interference or even poison under high RH poses a challenge for real applications. − Exploring a high-performance DMDS sensor (combing the advantages of high response, low limit of detection (LoD), exceptional selectivity, good moisture resistance, etc.) is highly required for the practical application, but it still remains a challenge.…”