Oral Exhalation H₂S Sensor Based on Cu₂O/ZnO Heterostructures

Developing a portable and compact sensor for room temperature detection of H₂S in exhaled breath for health assessment presents considerable technical challenges. This work successfully synthesized Cu₂O/ZnO heterostructures with excellent gas sensitivity to H₂S at room and lower temperatures using a two-dimensional (2D) electrodeposition in situ assembly method with the application of a semisine wave voltage as well as CuZnO nanoarrays deposited under direct current voltage. The Cu₂O/ZnO heterostructure sensors, with high response of 8.53 × 10⁴ to 1 ppm of H₂S and a minimum detection limit of 10 ppb at room temperature, exhibit a response of 42 for 10 ppm of H₂S even at -20 °C, and its response to 50 ppm of H₂S is approximately 3774 times greater than that of the CuZnO sensor, which is a significant challenge to achieve with sensors based on oxygen adsorption/desorption mechanisms. These outstanding gas-sensing properties are attributed to the formation of p-n heterojunctions in the Cu₂O/ZnO heterostructures and the occurrence of the sulfuration reaction. In addition, we successfully employed the Cu₂O/ZnO sensor to detect H₂S in human exhaled breath, offering valuable insights for the monitoring of various chronic diseases and new directions for the development of portable room-temperature breath sensors.