Surface Functionalization of Layered Molybdenum Disulfide for the Selective Detection of Volatile Organic Compounds at Room Temperature

Semiconducting two-dimensional (2D) transition-metal dichalcogenides (TMDCs) are considered promising sensing materials due to the high surface-to-volume ratio and active sensing sites. However, the reported strategies for 2D TMDCs toward sensing of volatile organic compounds (VOCs) present with some drawbacks. These include high operation temperatures, low gas response, and complex fabrication, limiting the development of room-temperature gas sensors. In this study, 2D MoS2 nanoflakes were prepared by liquid-phase exfoliation, and their surface was functionalized with Au nanoparticles (NPs) through a facile solution mixing method. MoS2 decorated with Au NPs with an average size of 10 nm was used as a material platform for an electrochemical sensor to detect a wide variety of VOCs at room temperature. Through dynamic sensing tests, the enhancement of gas-sensing performance in terms of response and selectivity, especially in detecting oxygen-based VOCs (acetone, ethanol, and 2-propanol), was demonstrated. After Au functionalization, the response of the gas sensor to acetone improved by 131% (changing from 13.7% for pristine MoS2 to 31.6% for MoS2-Au(0.5)). Sensing tests under various relative humidity values (10–80%), bending or long-term conditions, indicated the sound robustness and flexibility of the sensor. Density functional theory simulations suggested that the adsorption energy of VOC molecules on MoS2-Au is significantly higher than that on pristine MoS2, contributing to the gas-sensing enhancement; a VOC-sensing mechanism for Au-decorated MoS2 nanoflakes was proposed for the first time for the highly sensitive and selective detection of oxygen-based VOCs.