Selective N,N-Dimethylformamide Vapor Sensing Using MoSe2/Multiwalled Carbon Nanotube Composites at Room Temperature

As a typical volatile organic compound (VOC), N,N-dimethylformamide (DMF) is a popular solvent and tracer for environmental air quality monitoring. Highly selective detection with low electrical noise, quick response/recovery times, and superior sensitivity at room temperature against VOCs, especially at the parts per billion (ppb) level, continues to be a significant challenge in gas-sensing applications. To address the issue, herein we demonstrate an MoSe2/multiwalled carbon nanotube composite based chemiresitor sensor for the detection of DMF. MoSe2 with a layered sheetlike structure supports MWCNTs to enhance the specific surface area, thereby increasing the sensitivity (down to 0.1 ppm for DMF) and selectivity and improving the response over a wider range of relative humidities (30-80%). The composite-based sensor shows good sensitivity (12.3% for 5 ppm of DMF), better selectivity, and faster response (65 s) and recovery (90 s) times in comparison to the MoSe2 sensor (192, 392 s), respectively, and a consistent response over 35 days. Density functional theory simulations were employed to understand the adsorption process and sensing mechanism. An analysis revealed a negative adsorption energy of -716 meV, implying that the adsorption process is spontaneous and exothermic. Further, charge transfer (0.013 e) using the Bader scheme confirms the process to be physisorption in nature. The results were further supported using an electrochemical impedance spectroscopy analysis. These results indicate the great potential of the composite for selective and stable sensing of DMF over a wider range of relative humidities. The present work suggests that a composite of MoSe2 with MWCNTs could be useful to design DMF sensors with improved sensitivity and selectivity under various environmental conditions.