LMR-Based Optical Sensor for Ethylene Detection at Visible and Mid-Infrared Regions

Ethylene monitoring has long been a method of controlling the ripening of climacteric fruits, but it turns out that this gas is an important biomarker in biomedical applications. This work presents an optical gas sensor based on the lossy mode resonance (LMR) effect for ethylene detection in planar waveguide configuration. Two different approaches have been explored: one in the visible (VIS) spectral region and the second one in the mid infrared (MIR) region. Optical resonances have been achieved, in all cases, by means of sputtered tin oxide thin films. Response and recovery times were 54 and 246 s, respectively, for the sensor with the resonance in the VIS region, while the device operating in the MIR obtained response and recovery times of 19 and 47 s, respectively. The sensitivity during ethylene detection varied from 93.8 to 187.5 pm/ppm with the devices working in the VIS and MIR regions, respectively. According to the calibration curve, devices show an ethylene limit of detection (LOD) of 4.0058 and 0.6532 ppm in the VIS and MIR spectral regions, respectively, which finds applications in climacteric fruit ripening assessment as well as hemodialysis control. Cross sensitivity with humidity was also characterized for both devices.