Ultrasensitive Bio-H₂S Gas Sensor Based on Cu₂O-MWCNT Heterostructures

Developing a respiratory analysis disease diagnosis platform for the H₂S biomarker has great significance for the real-time detection of various diseases. However, achieving highly sensitive and rapid detection of H₂S gas at the parts per billion level at low temperatures is one of the most critical challenges for developing portable exhaled gas sensors. Herein, Cu₂O-multiwalled carbon nanotube (MWCNT) heterostructures with excellent gas sensitivity to H₂S at room temperature and a lower temperature were successfully synthesized by a facile two-dimensional (2D) electrodeposition in situ assembly method. The combination of Cu₂O and MWCNTs via the principle of optimal conductance growth not only reduced the initial resistance of the material but also provided an ideal interfacial barrier structure. Compared to the response of the pure Cu₂O sensor, that of the Cu₂O-MWCNT sensor to 1 ppm of H₂S increased nearly 800 times at room temperature, and the response time decreased by more than 500 s. In addition to the excellent sensitivity with detection limits as low as 1 ppb, the Cu₂O-MWCNT sensor was extremely selective with low-temperature adaptability. The sensor had a response value of 80.6 to 0.1 ppm of H₂S at -10 °C, which is difficult to achieve with sensors based on oxygen adsorption/desorption mechanisms. The sensor was used for the detection of real oral exhaled breath, confirming its feasibility as a real-time disease monitoring sensor. The Cu₂O-MWCNT heterostructures maximized the advantages of the individual components and laid the experimental foundation for future applications of highly sensitive portable breath analysis platforms for monitoring H₂S.