Performance demonstration experiment and DFT mechanism for an optical fiber toluene gas sensor based on CQDs@SiO2(-OH) porous film

An optical fiber toluene gas sensor working at room temperature is proposed based on CQDs@SiO 2 (-OH) porous film. The CQDs@SiO 2 (-OH) porous film was elaborated on the surface of the hollow core fiber (HCF) using the templating method, where the evanescent field is excited by a misaligned structure. The precursor solution formed by mixing CQDs with SiO 2 (-OH) enhances CQDs dispersion within the film, preventing aggregation and preserving active sites. Experimental results indicate that the gas-sensitive layer doped with CQDs demonstrates a sensitivity of 5.1 pm/ppm to toluene gas at room temperature, which is approximately 3.13 times greater than that of the SiO 2 (-OH) porous film. Additionally, it demonstrates a response time of 12 s and a limit of detection (LOD) of 3.9 ppm. The gas sensing mechanism is thoroughly investigated using DFT, exploring the electronic distribution of the gas-sensitive layer before and after CQDs doping and analyzing the sensitization mechanism. This study presents a novel approach for toluene gas detection at room temperature using an optical fiber sensor.