Ultrasensitive Exhaled Breath Sensors Based on Anti-Resonant Hollow Core Fiber with In Situ Grown ZnO-Bi₂O₃ Nanosheets

Combination of anti-resonant hollow-core fiber (HCF) and semiconductor nanomaterial is an effective strategy to obtain high-performance gas sensors with exceptional sensitivity and low power consumption. However, controlling the semiconductor morphology onto HCF is a major challenge to achieve the desired gas sensor with the enhanced sensitivity. Here, a ZnO-Bi₂O₃ nanosheets (NSs) heterostructure is grown in situ on the surface of HCF by sol–gel and hydrothermal methods. ZnO-Bi₂O₃ NSs serving as electron acceptors trap electrons after acetone adsorption and then change the refractive index of the surface of HCF. Benefiting from the unique sheet structure and the synergetic effects for multi-component, the resulting ZnO-Bi₂O₃ NSs enabled HCF gas sensor exhibits high sensitivity, selectivity, and repeatability for detecting acetone at room temperature, particularly in the low concentration range, with the theoretical limit of detection down to 140 parts-per-billion. Meanwhile, the successful application of the ZnO-Bi₂O₃ NSs enabled HCF gas sensor to distinguish the exhaled breath from the healthy individuals and simulated diabetic cases is demonstrated, which paves the way to achieve non-invasive, ultra-sensitivity gas sensing at room temperature for the early diagnosis of diabetes.