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 fiber-optic 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.