First-principles insights into the C6N7 monolayer as a highly efficient sensor and scavenger for the detection of selective volatile organic compounds.

The design of new gas sensors and scavengers of volatile organic compounds (VOCs) is desirable for VOC enriching, separation and utilization. Herein, first-principles methods were performed to investigate the potential of C6N7 monolayers as highly efficient sensors and scavengers for selective VOCs (toluene, benzene, vinyl chloride, ethane, methanal, acetone, ethanol, and acetaldehyde). The physisorption of toluene, benzene, acetone, ethanol, acetaldehyde, and methanal has relatively high adsorption strength and can significantly tune the electronic properties and work function (Φ) of the C6N7, indicating that the C6N7 monolayer is highly sensitive and selective to these VOC gases. In addition, the desorption time of benzene, acetone, ethanol, acetaldehyde, and methanal is about 3, 0.4, 2.0 × 10-2, 3.0 × 10-2, and 3.6 × 10-5 s at 300 K, respectively, indicating that the C6N7-based sensor has high reusability at room temperature. The recovery time of toluene was about 7.8 × 102 s at 300 K, showing disposable toluene gas sensing of the monolayer. Our work confirms that the C6N7 monolayer as a resistance-type and Φ-type gas sensor and scavenger is highly sensitive, selective and reusable for VOCs (benzene, acetone, ethanol, acetaldehyde, and methanol), but is a disposable toluene gas sensor and scavenger at room temperature.

First-Principles Investigation of Adsorption Behaviors and Electronic, Optical, and Gas-Sensing Properties of Pure and Pd-Decorated GeS2 Monolayers.

The extensive applications of two-dimensional (2D) transition metal disulfides in gas sensing prompt us to explore the adsorption, electronic, optical, and gas-sensing properties of the pure and Pd-decorated GeS2 monolayers interacting with NO2, NO, CO2, CO, SO2, NH3, H2S, HCN, HF, CH4, N2, and H2 gases by using first-principles methods. Our results showed that the pure GeS2 monolayer is not appropriate to develop gas sensors. The stability of the Pd-decorated GeS2 (Pd-GeS2) monolayer was determined by binding energy, transition state theory, and molecular dynamics simulations, and the Pd decoration has a significant effect on adsorption strength and the change in electronic properties (especially electrical conductivity). The Pd-GeS2 monolayer-based sensor has relatively high sensitivity toward NO and NO2 gases with moderate recovery time. In addition, the adsorption of NO and NO2 can conspicuously change the optical properties of the Pd-GeS2 monolayer. Therefore, the Pd-GeS2 monolayer is predicted to be reusable and a highly sensitive (optical) gas sensing material for the detection of NO and NO2.