MoSe2 Nanoflakes Based Chemiresistive Sensors for ppb-level Hydrogen Sulfide gas Detection

Detection and quantification of hydrogen sulfide (H₂S) gas is important as it influences directly human health, our environment, and operations of several industries including food and beverages, oil, construction, and medicine. It also acts as biomarker in diagnosis of halitosis at early stage. We report herein liquid exfoliated MoSe₂ nanoflakes based stable chemiresistive H₂S gas sensor which operate at moderate temperature of 200℃. The response of p-type MoSe₂ gas sensor device (when operated in ambient environment) was found to be varying between 15.87%–53.04% when the concentration of H₂S was varied between 50 ppb – 5.45 ppm. The response of the device decreases when the measurements were done in synthetic air environment and it varies between 7.13%–19.87% for the concentration range of 500 ppb - 5.45 ppm. The response (%), recovery rate (%), hysteresis, experimental lowest detection limit etc. of the device suggest that the device performs better when operated in ambient than in synthetic air which suggest its real time device application. The response time and recovery time of the sensor are 15 s and 43 s respectively for 100 ppb of H₂S. The sensor performance was found to be highly repeatable with sensitivity of 5.57%/ppm of H₂S. The theoretical limit of detection and limit of quantization of the device were found to be 6.73 ppb and 22.44 ppb respectively. Based on chemical analysis, a plausible mechanism based on charge transfer phenomenon has been proposed for this sensor.