Room Temperature Detection of NH₃ at ppb Level Using Pt-Decorated ZnO/MoS₂ Heterostructures

Molybdenum disulfide (MoS<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>) has attracted significant attention as a gas-sensing material due to its large surface area, air stability, and active sites for functionalization. Despite these advantages, MoS<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>-based sensors often exhibit low sensitivity, slow response, and weak recovery at room temperature. To overcome these limitations, heterostructures can be engineered to improve the electronic properties of MoS<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> nanosheets, enhancing their sensitivity and recovery. This study demonstrates a novel p–n hetero-structure using zinc oxide (ZnO) as an outer sensing layer on MoS<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>, significantly improving sensor performance. The performance of a ZnO/MoS<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> sensor was evaluated using COMSOL Multiphysics with an interdigitated electrode design. The optimized sensor demonstrates an outstanding response to NH3, fast response/recovery, and long-term stability. The sensitivity can be further enhanced by incorporating Pt onto the ZnO/MoS<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> heterostructure. The study revealed a sensitivity of 0.08654 ppb⁻¹, making it highly effective for detecting NH<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> at low concentrations additionally an LOD(limit of detection) of 5 ppb. Furthermore, it shows high selectivity to NH3 compared to several interfering gases. The enhanced performance of the sensor is due to the active sites on the ZnO/MoS<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> structure and efficient electron transport within the heterostructure. Additionally, the catalytic action of Pt lowers the activation energy for NH<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> adsorption, improving overall sensor efficiency. This approach offers the potential for expanding the sensor's capabilities.