High-Sensitivity CO₂ Sensor Based on a Graphene Oxide Coated Long-Period Fiber Grating

This study presents the development and characterization of a novel carbon dioxide (CO₂) sensor based on graphene oxide (GO)-coated long-period fiber grating (LPFG). The structural and chemical properties of GO were analyzed using Raman spectroscopy and scanning electron microscopy (SEM), revealing a defective structure with a high degree of oxidation and significant surface roughness, which enhances gas adsorption capabilities, making it highly suitable for CO₂ detection. The sensor's performance was evaluated across CO₂ concentrations ranging from 5 to 65%. The operational principle of the sensor is based on changes in the resonance wavelength induced by variations in the refractive index of the GO coating as it interacts with CO₂ molecules. Results indicate a notable sensitivity of 0.0643 nm/% and low hysteresis during adsorption and desorption processes, affirming its stability and reliability. Additionally, the sensor demonstrated a strong linear fit of approximately 96% in adsorption and desorption cycles (5-65 and 65-5%). These findings underscore the significant potential of the GO-coated LPFG sensor for practical CO₂ sensing applications, offering advantages such as immunity to electromagnetic interference and ease of integration into remote sensing technologies.