Tilted Fiber Grating Functionalized by In-Situ Grown HKUST-1 Nanolayer for Fast Ethanol Gas Detection

Recent increased attention to environmental and health monitoring demands faster response and reliable gas concentration measurement technology. Herein, we propose an optical fiber-based strategy for fast ethanol gas concentration sensing using a tilted fiber grating (TFG) assisted with a nanolayer of HKUST-1. The TFG excites unique cladding mode resonances and strong evanescent field that interact with the in-situ grown HKUST-1 nanolayer that provides a path for the penetration and absorption of ethanol gas. The TFG, functionalized with 281 nm thick HKUST-1 nanolayer, exhibits a sensitivity of 7.7 nm/% over an ethanol gas concentration range of 0∼0.14% and a limit of detection of 35 ppm at room temperature, by tracking the resonance wavelength shift of a cladding mode. Time-domain experiments reveal the response and recovery times of 26.7 s and 10.3 s, respectively, attributed to the high surface area and porosity of the HKUST-1 nanolayer. The proposed fiberoptic ethanol gas sensor offers ease of integration, rapid response, and high repeatability and reliability, making it suitable for applications such as chemical plant leakage monitoring and medical breath analysis.