Individual gas sensor detecting dual exhaled biomarkers via a temperature modulated n/p semiconducting transition

The newly-emerged breath sensing detection of disease biomarkers (e.g., H2S and acetone) offers rapid and noninvasive early diagnosis of diseases (e.g., halitosis and diabetes). Utilizing a single sensor to monitor dual biomarkers may contribute to both miniaturized size and multi-detection if implemented, but remains challenging. Here, interconnected BiFeO3/Bi25FeO40 nanoparticles (NPs, ∼22.5 nm in diameter) synthesized via combined microwave hydrothermal and annealing methods have been developed to selectively detect dual biomarkers of halitosis and diabetes. The selective detection has been modulated by an n/p semiconducting transformation, and has been experimentally observed and theoretically interpreted, in which electron–hole pairs are modulated due to the synergistic effect of temperature-dependent adsorbed oxygen molecules and semiconducting band bending. Remarkably, the sensor prototypes enable the selective detection of both H2S (n-type mode) and acetone (p-type mode) biomarkers with superior stability and a ppb-level detection limit. Furthermore, practical human breath has been experimentally simulated. Critically, the sensors with a waterproof membrane have been tested by immersing them into water. Our strategy of the detection of dual exhaled biomarkers by a single gas sensor may contribute to the integration and miniaturization of sensors, for upcoming intelligent medical treatment.