Ethanol sensor based on cascaded tapered optical fiber with surface modification of ZIF-8

To detect trace amounts of ethanol in the air, a cascaded tapered optical fiber sensor with surface modified ZIF-8 was proposed. Using an in-situ growth method, ZIF-8 was immobilized on the surface of the sensing tapered optical fiber. Simultaneously, another reference tapered fiber with a similar Free Spectral Range (FSR) was connected in series, creating a Vernier effect that can amplify slight changes in the surface Refractive Index (RI) of the sensing tapered fiber. The RI sensitivity of the cascaded tapered fiber was 18,366.17 nm/RIU, which was 9.6 times that of a single tapered fiber. The sensitivity of the sensor to ethanol gas at room temperature was investigated. In the concentration range of 0–140 ppm, the sensitivity was 0.1411 nm/ppm. The sensor exhibits high sensitivity, good reversibility and the capability for online detection, making it a convenient tool for monitoring ethanol leaks in industrial production.