Ultraviolet Irradiation Stimulated NO₂ Sensing Using WS₂ Nanosheets Decorated with Au Nanoparticles

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have attracted considerable attention in the field of room-temperature gas detection due to their high surface area and intriguing electronic properties. However, due to the insufficient activation energy for gas molecules at room temperature and the increased number of adsorption sites caused by the 2D structure, gas molecule desorption becomes challenging. As a result, TMDs-based gas sensors often exhibit a poor recovery performance. In this study, we developed an efficient nitrogen dioxide (NO2) gas sensor based on gold (Au) nanoparticle-decorated tungsten disulfide (WS2) nanosheets. The sensor was prepared by using a straightforward liquid-phase exfoliation method combined with in situ reduction, enabling effective NO2 detection at room temperature under ultraviolet (UV) activation. Specifically, the Au/WS2 composite nanomaterial, with 5 mol % Au content, demonstrated a response of 32.1 when exposed to 10 ppm NO2 under UV activation. The response is 9.44 times higher than that of the bare WS2 based sensor, highlighting the remarkable enhancement achieved by incorporating Au nanoparticles and UV irradiation. Significantly, the UV-activated Au/WS2 sensor was able to fully recover to the baseline position within 508 s, demonstrating an excellent recovery performance. Moreover, the sensor achieved a theoretical detection limit of 331 parts per billion (ppb) for NO2 and exhibited good selectivity and long-term stability. The substantial improvement in sensing performance can be attributed to the synergistic effect of the electronic and chemical sensitization facilitated by the presence of Au nanoparticles, combined with the activation influence of UV irradiation. The energy introduced by UV irradiation further promotes the catalytic performance of Au nanoparticles at room temperature, while the photoinduced electron/hole pairs enhance the gas sensing performance of NO2. This study provides a feasible pathway for preparing WS2-based composite nanomaterials and enhancing the sensing performance of TMDs-based gas sensors at room temperature.