LAUSR

A high-performance NO2 sensor based on the 3D MoS2 aerogel is presented. Compared to single- or few-layer MoS2, 3D assemblies of 2D MoS2 provide more surface area per footprint with a simple and scalable synthesis. Integration of the 3D MoS2 aerogel on a low-power microheater platform is demonstrated, and the sensing behavior of the 3D MoS2 aerogel is investigated. A two-step sulfurization treatment is developed to obtain a high-quality MoS2 aerogel with strong sensing performance. The aerogel exhibits low detection limit (50 ppb) toward NO2 at room temperature, while after the two-step sulfurization treatment, it also exhibits fast response and recovery at low heater temperature of 200 °C, with no decrease in sensitivity. The observed p-type sensing behavior of MoS2 aerogel is investigated and identified as being controlled by the defect state (as probed by the S:Mo ratio). It is demonstrated that annealing in a hydrogen environment changes the defect state of the MoS2 aerogel by creating more sulfur vacancies; concomitantly, a transition from p-type sensing behavior to n-type sensing is observed.