Sulfur-Vacancy-Enriched MoS₂ Nanosheets Based Heterostructures for Near-Infrared Optoelectronic NO₂ Sensing

Transition metal dichalcogenide nanostructures especially MoS2 have emerged as novel gas sensing materials. Particularly, MoS2-based optoelectronic devices activated by UV or visible light have been demonstrated as promising candidates for room temperature NO2 sensors. Here, we propose a novel room-temperature optoelectronic NO2 sensor based on sulfur-vacancy-enriched MoS2 (SV-MoS2). SV-MoS2 nanosheets were efficiently fabricated by a microwave-hydrothermal method, and their enhanced optical absorption and optoelectronic properties in the near-infrared (NIR) light region were experimentally and theoretically investigated. The optoelectronic gas sensors based on SV-MoS2 exhibited enhanced performance to ppb level of NO2 under NIR light illumination at room temperature. In addition, through functionalization with ZnO quantum dots, the SV-MoS2/ZnO nanocomposites exhibited a further enhancement in responses with fast response/recovery rates, full reversibility, and sub-ppb detection limit to NO2 at room temperature. The significant NO2 sensing improvement was due to the improved charge generation and transfer induced by sulfur vacancy under NIR light illumination. In addition, the sensor shows satisfied stability, reliable selectivity, and humidity resistance at room temperature. Therefore, this work provides an alternative approach to high-performance, low-power-consumption optoelectronic NO2 gas sensors working at room temperature, which can also be applied to other transition metal dichalcogenides for optoelectronic devices.