Highly sensitive few-layer MoS₂ nanosheets as a stable soil moisture and humidity sensor

In this work, an ultrasensitive humidity and soil moisture sensor has been developed using exfoliated MoS₂ nanosheets as a sensing film in combination with the interdigitated electrode configuration. The performance of the sensor was examined at room temperature with respect to different relative humidity levels (RH) and soil water content (θg). A variation from 35 pF to 15200 pF capacitance were obtained when relative humidity levels changes between 11% and 96% at room temperature. The response and recovery times of the sensor were approximately 30 s and 40 s, respectively. Soil sensing properties were investigated in a detection range from dry soil to saturation level for two different type of soil (black and red soil) samples. The capacitance of the MoS₂ based sensor increases monotonically when the soil moisture content increased from 3.6-53% and 2.3-45% for black and red soil, respectively. The observed variation in capacitance corresponding to 53% θg black soil and 45% θg red soil is approximately 250 and 200 times of that observed for respective dry soil samples. The soil sensing results shows unprecedented response, long-term stability and good reproducibility. The device features low cost, stable performance with high accuracy. (author)