Highly sensitive room-temperture NO₂ gas sensor based on Bi₂S₃ nanorods

Bismuth sulfide (Bi₂S₃) is known for its remarkable sensitivity and stability, making it as an ideal material for gas sensor. Here, we present a highly sensitive room-temperature NO₂ gas sensor by controlling the Bi₂S₃ nanorods morphology through hot injection method with varying Bi/S ratios (Bi/S = 1, Bi/S = 2, Bi/S = 4). The as-synthesized samples were subsequently spin-coated onto ceramic substrates to fabricate chemo-resistive gas sensors. TEM and XPS analyses revealed that with the increasing Bi/S ratio in the precursors leading to the nanorods aspect ratios enhancing and the generation of S vacancies facilitating. As a result, Bi₂S₃ nanorods with a Bi/S ratio of 4 exhibited higher carrier mobility and provided more accessible sites for gas molecules. The optimal sensor (Bi/S = 4) showed an impressive response of 12.2 for 10 ppm NO₂, which is 4 times higher than the device of Bi/S = 1. It also demonstrated a fast response/recovery time of 39 s/696 s and a lower detection limit down to 120 ppb. These findings highlight the excellent gas sensitivity performance of Bi₂S₃ nanorods at room temperature and their potential for the development of energy-efficient and cost-effective gas sensors.