Room-Temperature Optoelectronic NO₂ Sensing Using Two-Dimensional Gallium Oxyselenides

Detecting trace-level nitrogen dioxide (NO 2 ) in real time is critical due to its adverse impact on human health and the environment. However, achieving a fast response, high sensitivity and selectivity, and excellent stability in NO 2 detection remains a challenge. Two-dimensional (2D) metal chalcogenides are promising for gas sensing, but their practical use is thwarted by issues like insufficient recovery and poor stability. As an alternative, it is anticipated that 2D metal oxychalcogenides, an emerging class of gas-sensing semiconductor materials, offer favorable characteristics. In this work, 2D p-type gallium oxyselenide nanosheets tailored with various oxygen concentrations are synthesized by regulating the annealing temperature of gallium selenide. We find that the gas sensor based on GaSe 0.31 O 0.69 exhibits the highest response of 58.28% for 10 ppm of NO 2 at room temperature. In addition, the sensor has high selectivity, with a response more than 10 times higher than interfering gases. More importantly, this material exhibited outstanding long-term stability (up to 4 months) and demonstrated a reversible response to NO 2 at room temperature. This work paves a cost-effective way for the development of room-temperature NO 2 gas sensors, exhibiting an exceptional gas response and long-term stability.