Cu2O-CNF heterojunction for exhaled H2S sensing

Developing a gas sensor for the expedient, rapid, and accurate detection of hydrogen sulfide (H2S) in human exhaled breath at room temperature would offer an opportunity for home-style self-monitoring of some chronic diseases. In this work, Cu2O-carbon nanofiber (CNF) heterojunctions were prepared by a two-dimensional (2D) electrodeposition in-situ assembly method to detect low-concentration H2S gas at room temperature. The heterojunction had a distinct interface, which was confirmed by scanning electron microscopy, transmission electron microscopy and voltammetry tests. The detection limit of the sensor was as low as 5 ppb, and the sensors could directly distinguish the exhaled breath of healthy individuals and simulated patients. We attributed the excellent performances to synergistic effects of the modulation of the heterointerface barrier and the sulfide reaction of Cu2O. Furthermore, the adsorption behaviors of H2S on the surfaces of pure Cu2O and the Cu2O-CNF heterojunction were evaluated using the density functional theory (DFT) based on first principles. The results further confirmed that the formation of the heterostructure enhances the H2S adsorption capacity and electron transfer of the sensitive material. This study is of great significance for the diagnosis and monitoring of diseases with the exhaled H2S biomarker.