Nitrogen Dioxide Gas Sensor Based on Liquid-Phase-Exfoliated Black Phosphorus Nanosheets

Black phosphorus (BP) nanosheets represent a promising class of two-dimensional (2D) materials for nitrogen dioxide (NO2) sensing, but its practical application is limited by complex preparation processes. In this paper, we present an ultrasensitive and selective chemiresistive NO2 sensor based on liquid-phase-exfoliated BP nanosheets. The unique combination of probe sonication and ice-water bath sonication is capable of producing BP nanosheets of various controllable sizes. Sensing characterization shows that the BP nanosheet-based sensor exhibits a large sensing response of 88%, a high selectivity, and a full recovery toward 100 ppb NO2 gas at room temperature, which represents a substantial improvement over recently reported designs. The proposed preparation method for nanosheets with tunable gas-sensing properties is instrumental to the practical applications of BP toward high-performance, portable, and ubiquitous NO2-sensing applications.