High-Performance Nitric Oxide Sensor Using a MoS ₂ /WO ₃ Heterojunction Enhanced by the Surface Plasmon Resonance of Gold Nanoparticles

In the field of gas-sensing technology, there is increasing focus on the advancement of sensors for detecting nitric oxide (NO) gas, driven by its critical roles in industrial, environmental, and biomedical contexts. This research explores two innovative device configurations for NO gas detection: the MoS 2 /WO 3 heterojunction and the MoS 2 /WO 3 heterojunction functionalized with gold nanoparticles (Au-NPs). The Au–MoS 2 /WO 3 thin film sensor exhibited exceptional NO detection performance at 50 °C, with a high response of approximately 120 and response/recovery times of 29 s/102 s for 1 ppm of NO. For 5 ppm of NO concentration, the sensor exhibited a response of approximately 170, with response/recovery times of 22 s and 117 s, marking a notable 70% improvement over the nonfunctionalized MoS 2 /WO 3 device. Additionally, the sensor demonstrated sensitivity to detect ultralow NO concentrations, with a response of approximately 21 for 100 ppb and a detection limit of approximately ∼1000 ppt. These results highlight the potential of Au–MoS 2 /WO 3 -based sensors for environmental monitoring and medical diagnostic applications with the possibility of future integration into flexible and wearable devices.