Ag decoration-enabled sensitization enhancement of black phosphorus nanosheets for trace NO2 detection at room temperature

Black phosphorus (BP), one rising star of two-dimensional (2D) materials, has showcased a huge capability for ppb-level NO2 detection. However, sluggish reaction kinetics and fragile stability frustrate its further application. In this regard, for the first time we prepared Ag nanoparticles modified BP nanosheets as the sensing layer via one feasible method to recognize trace NO2 at room temperature. With respect to individual BP, the composition optimized BP-Ag nanocomposites (BP-Ag-1 sensor) achieved a favorable performance primarily in terms of boosted response (39.9% vs. 11.8%, 100 ppb NO2), accelerated response speed (190 s vs. 486 s, 100 ppb NO2) and strengthened operation stability, together with ultralow theoretical detection limit of 0.25 ppb. Furthermore, a protection layer comprised of polylactic acid (PLA) was anchored onto the surface of BP-Ag-1 sensor to keep the water molecules physically from the sensing layer and retain a distinguishable signal toward trace NO2 at high moisture environments. The introduction of Ag and PLA separately reduced the lone electron pairs from P atoms and suppressed the water penetration into the BP film, thereby offering an alternative way to passivate BP for its optoelectronic applications in the future.