Facile Solution-Processed Deposition of Bi2S3 Nanostructures for a Highly Sensitive and Selective Room-Temperature NO2 Sensor

In this work, we present an approach for utilizing pristine Bi₂S₃ as a sensing material for the detection of NO₂ gas at room temperature. Spanish oyster-like hierarchical Bi₂S₃ nanostructures, with a diameter of 832 nm and a Brunauer–Emmett–Teller (BET) surface area of 20.56 m²/g, were grown using the [Bi{S₂P(O(Pr)₂)₃}] complex via an optimized, one-step, low-temperature, and in situ solvothermal process. In contrast, the spin-coating method resulted in impurities even after the annealing step. X-ray diffraction (XRD), Raman, selected area diffraction (SAED), and high-resolution transmission electron microscopy (HRTEM) analyses confirmed the orthorhombic bismuthinite phase of the Bi₂S₃ nanostructures, with a calculated band gap of 2.82 eV. The Bi₂S₃-based sensor exhibited exceptional sensitivity and selectivity toward NO₂, surpassing other gases such as CO₂, NH₃, H₂S, and C₂H₆O at room temperature. Specifically, the sensor demonstrated a high response of 39.4%, rapid response/recovery times (14/257 s), excellent repeatability, and stability (30 days) under 100 ppm of NO₂ exposure. The enhanced performance at room temperature is attributed to the competitive adsorption of NO₂ on the hierarchical structure of Bi₂S₃, facilitating increased gas adsorption and charge transfer.