Highly Sensitive, Selective, Stable, and Flexible NO₂ Sensor Based on GaSe

Air pollution is a global problem, which poses serious environmental concerns and health risks. In light of this, a key aspect of the challenge of managing air pollution is effective monitoring, which requires reliable high-sensitivity sensors with strong selectivity and long-term stability. Layered materials represent an emergent class of materials with extraordinary electronic properties and physicochemical properties, and, therefore, are a highly attractive prospect for this field. Here, such a sensor for NO₂ based on GaSe is presented. An ultrahigh sensitivity of 0.5 part per billion (p.p.b.) is achieved at room temperature, and the NO₂ selectivity ratios with respect to other likely interfering environmental gases are larger than 100. Moreover, no great degradation is observed after 10 days of air exposure. As a practical demonstration, the GaSe-based sensors are also used to detect vehicle exhaust emission, and wearable GaSe-based NO₂ sensors are presented and tested. Based on the results obtained in this work, it is believed that GaSe-based sensors can be used for the detection of NO₂ in real-world applications.