High performance H₂S gas sensor with UV-activated CuO nanosheets

Detecting H₂S at room temperature is crucial due to its high toxicity and flammability which poses significant explosion hazards, especially when conventional thermally activated chemiresistive gas sensors are used. To mitigate these hazards, we developed a UV-activated chemiresistive gas sensor using CuO nanosheets, designed for room-temperature H₂S detection on a low-power, miniaturized platform. The CuO nanosheets were synthesized using hydrothermal methods, and their plate-like morphology was confirmed with scanning electron microscopy (SEM) analysis. UV activation of CuO coupled with the nanosheet morphology promoted sensitivity, range of detection, stability, and complete sensor recovery at room temperature due to the generation of photoinduced oxygen ions, and increased surface area and porosity with reduced sulfur mass content after H₂S exposure. When activated under a 275 nm UV-LED, the CuO nanosheets demonstrated sensitive measurement of H₂S in the 1-100 ppm range, with response and recovery times of 80 s and 600 s, respectively, for concentrations above 50 ppm. The sensor exhibited excellent selectivity for H₂S, displaying significantly higher sensitivity to 1 ppm of H₂S compared to 10 and 50 ppm of common interfering gases such as N₂O, NO₂, CH₄, CO, and NH₃. However, the sensor's response decreased with increasing humidity, as H₂S competes with water vapor for chemisorbed oxygen ions. This study highlights the development of a highly sensitive and selective H₂S gas sensor with relatively fast response and recovery times at room temperature, achieved through UV activation of CuO nanosheets.