Highly responsive WO3/SnS2 sensor with humidity compensation: NO2 real-time detection system in soil surface layer

NO 2 concentration in soil surface is one of the important indicators affecting soil nitrogen cycle. Real-time detection of NO 2 is crucial to optimize the use of nitrogen fertilizer and improve efficiency, which is also a key means to prevent soil acidification and increase crop yield. However, the humidity conditions on the soil surface increase the challenge of real-time detection of NO 2 . Therefore, a composite material of tungsten oxide (WO 3 ) composite tin sulfide (SnS 2 ) with heterogeneous structure was synthesized by one-step hydrothermal method. The composite material is seen to exist in the form of nanosheets. At the optimal working temperature of 210℃, the response of the composite material (WO 3 /SnS 2 (3:10)) with a molar ratio of WO 3 to SnS 2 of 3:10–20 ppm NO 2 is 63.8. The excellent gas sensing performance is attributed to the composition of heterojunction and the increase of deficiency oxygen. In the relative humidity (RH) range of 20–98 %, the response of the WO 3 /SnS 2 (3:10) has a good linearity ( R 2 =0.995). Therefore, the humidity compensation is integrated into the convenient NO 2 detection equipment to ensure that the WO 3 /SnS 2 (3:10) sensor can detect NO 2 stably and accurately under different humidity conditions. The NO 2 real-time detection system uses the OLED to display the humidity value and NO 2 concentration value in real time on the soil surface, and the buzzer as an alarm device for exceeding the concentration threshold (2 ppm NO 2 ), which reminds staff of the need to take action to adjust crop management strategies to improve crop health.