Conductometric room temperature ammonia sensors based on titanium dioxide nanoparticles decorated thin black phosphorus nanosheets

Abstract

Ammonia gas (NH3) as a harmful and toxic gas species severely threatens ecological harmony and human health, thus necessitating its sensitive detection at very low dose. In this regard, two-dimensional (2D) nanomaterials have been extensively harnessed as the sensing layers due to the unique merits of large surface area, intriguing layer-dependent electrical behaviors and versatile modifications. Of these 2D candidates, black phosphorus (BP) as a rising representative has attracted considerable attention, whereas undesirably hindered by sluggish response/recovery kinetics and fragile stability. To circumvent these obstacles, we employed titanium dioxide (TiO2) nanoparticles decorated BP nanosheets as the sensing layer to selectively discern 0.5–30 ppm NH3 at room temperature (18 ± 2 °C) for the first time. The constituent ratio-optimized BP-TiO2 sensors exhibited higher response, less baseline drift, shorter response/recovery times, and stronger long-term stability when compared with pure BP counterparts. Enlarged specific surface area, numerous p-n BP-TiO2 heterojunctions and TiO2 nanoparticles involved passivation were primarily responsible for these improvements. In summary, the proposed composite sensors have expanded BP-related gas sensing to NH3 gas for the first time in the experimental perspective simultaneously enriching feasible strategies to improve the operation stability of BP nanosheets.