Au@ZnO functionalized three-dimensional macroporous WO3: A application of selective H2S gas sensor for exhaled breath biomarker detection

Sensitive and selective determination of H2S in human exhalation is essential for understanding some physiological and pathological processes. However, effective detection of H2S at ppb level remains a challenge. In this work, three-dimensional inverse opal (3DIO) WO3 structure modified with metal-organic framework (MOF) derived ZnO@Au nanoparticles (NPs) were designed and fabricated for trace H2S detection. The ordered macroporous structure of 3DIO, n-n heterojunctions between WO3 and ZnO, and effective encapsulated of small-sized Au NPs benefited to the sensing performance. Compared to pristine 3DIO WO3 sensor, the response of MOF derived 3DIO WO3/ZnO@Au sensor enhanced 6.5-folds (175 to 10 ppm H2S), the optimal working temperature dramatically decreased to 170 degrees C, and the actual detection limit extended to 50 ppb with a response of 8.5. The good selectivity and long-term stability of the sensor were also identified. The theoretical simulation indicated that improved conductivity, higher negative charge of O, and increased adsorption energies contributed to the excellent selectivity. Furthermore, the proposed sensor could distinguish the trace H2S concentration change in the exhaled breath environment. This work demonstrates an example of a simple and versatile method for high performance H2S gas sensor design, which is promising for exhaled breath biomarker determination.