Room temperature hydrogen sulfide gas detection using copper oxide nanotube/indium tin oxide nanoparticle heterojunctions

Various copper oxide nanotube/indium tin oxide (CuO/ITO) nanocomposite-based chemiresistive gas sensors were fabricated and tested toward hydrogen sulfide (H₂S) in the presence and absence of ultra-violet (UV) light excitation at room temperature. Among these different combinations, 60:40 wt.% of CuO:ITO showed the highest sensing performance toward H₂S gas (i.e., sensor response (S) = 5.7 toward 40 ppm_m (parts per million by mass) H₂S gas), which is ̴5.7 times higher than pristine CuO and ITO counterparts. The enhancement in the gas sensing performance by mixing ITO and CuO nanostructures might be due to the formation of p/n heterojunction between ITO nanoparticles and CuO nanotubes. The low limit of detection (LLOD) of 500 ppb_m (part per billion by mass) of S = 1.2 was experimentally achieved by photo exciting sensing materials using 400 nm UV light. This might be attributed to the faster adsorption of H₂S molecules and higher carrier concentration under light illumination. These sensors also maintained good H₂S sensing performance in the presence of water vapors which makes these sensors suitable for practical application. This work paves a way to fabricate low-power H₂S gas sensors by eliminating heaters.