Exfoliated Molybdenum Disulfide Nanosheet Networks as Sensing Materials for Nitrogen Dioxide Detection

Nitrogen dioxide (NO₂) is a gaseous air pollutant linked to respiratory and cardiovascular diseases and environmental problems such as acid rain and tropospheric ozone formation. Reference instruments for measuring NO₂ are expensive, highlighting the need to develop low cost sensor technologies for wider scale monitoring of this critical pollutant. Here, we report the development of a scalable sensor using electrochemically exfoliated 2D molybdenum disulfide (MoS₂) networks. The sensor can detect a wide range of NO₂ concentrations at room temperature, with an experimental limit of detection (LOD) as low as 150 ppb and a theoretical LOD of 1.9 parts per quadrillion (ppq) in dry air. The sensor exhibited approximately 90% response to 1 ppm of NO₂ within 10 min of exposure. UV irradiation significantly enhanced the sensor's recovery time, reducing it from 20 min to less than 2 min. Evaluation of the sensor within a large (∼6.5 m³) atmospheric simulation chamber yielded a similar response and recovery time performance, opening the opportunity for further tests in the chamber under various conditions. Finally, using Density Functional Theory (DFT) calculations, we identified key atomic-scale structures and processes highlighting the importance of electrochemically exfoliated sulfur-deficient MoS₂ for sensitive room temperature NO₂ detection.