Ultrasensitive Detection of Hydrogen Sulfide for Small Intestinal Bacterial Overgrowth Breath Analysis via SnO2 Quantum Dots Decorated CuO Sensor

Small intestinal bacterial overgrowth (SIBO) is a gastrointestinal disorder characterized by an abnormal increase in the bacterial population of the small intestine. Methane/hydrogen breath testing has been widely used for the diagnosis of SIBO; however, false-negative results remain a challenge. Hydrogen sulfide (H2S) could serve as a valuable complement to the current SIBO breath-testing system, thereby improving diagnostic accuracy. Herein, we report SnO2 quantum dot (QD)-modified CuO nanosheets as a high-performance sensing material for the room-temperature detection of H2S in exhaled breath. The SnO2 QD/CuO sensor exhibits a response of 9.26 to 30 ppb H2S and a reproducible detection of H2S down to 5 ppb. Moreover, the sensor shows minimal hysteresis and excellent long-term stability, retaining 90.2% of its initial response to 50 ppb H2S after four weeks of storage. The high sensitivity of SnO2 QD/CuO to H2S is mainly attributed to the synergistic effects of the strong interaction between CuO and H2S and the electronic modulation induced by SnO2 QDs. A breath-analysis device based on the SnO2 QD/CuO sensor was developed for H2S detection in exhaled breath. The device showed distinguishable responses between healthy individuals and patients with clinically diagnosed H2S-producing SIBO in a small preliminary cohort, although larger studies are needed for further validation. These preliminary results indicate that SnO2 QD/CuO is a promising material for exhaled-breath H2S detection and may provide complementary information for future breath-based SIBO assessment.