Nanorods Assembled Hierarchical Bi2S3 for Highly Sensitive Detection of Trace NO2 at Room Temperature

The bismuth sulfide nanostructure has become a promising gas sensing material thanks to its exceptional intrinsic properties. However, pristine Bi2S3 as a room-temperature sensing material cannot achieve the highly sensitive detection of ppb-level NO2 gas. Herein, 1D nanorods with self-assembled hierarchical Bi2S3 nanostructures were obtained via a simple hydrothermal process. The as-prepared hierarchical Bi2S3 nanostructures exhibited outstanding NO2 sensing behaviors, such as a high response value (R-g/R-a = 5.8) and a short response/recovery time (tau(90) = 28/116 s) upon exposure to 1 ppm NO2. The limit of detection of hierarchical Bi2S3 was down to 50 ppb. Meanwhile, the sensor exhibited excellent selectivity and humidity tolerance. The improved NO2 sensing properties were associated with the self-assembled hierarchical nanostructures, which provided a rich sensing active surface and accelerated the diffusion and adsorption/desorption processes between NO2 molecules and Bi2S3 materials. Additionally, the sensing response of hierarchical Bi2S3 nanostructures is much higher at 100% N-2 atmosphere, which is different from the chemisorption oxygen model.