HMS optical fiber gas sensor based on double-layer WO3@CQDs porous film modified cladding for detecting 2-butanone gas at room temperature

In this study, a hollow malposition structure (HMS) optical fiber 2-butanone gas sensor based on double-layer WO3@CQDs porous film is proposed, and realizes the ppb detection of 2-butanone gas at room temperature. The HMS can excite the evanescent field and sense the gas adsorption on the fiber surface. The experimental results show sensitivity of 3.09 pm/ppm for this HMS optical fiber gas sensor based on double-layered WO3@CQDs porous film, which is 6.05 times higher than that of the sensor coated with single-layer WO3@CQDs porous film. In addition, a limit of detection (LOD) reaches 500 ppb. The response time is 11.7 s and the recovery time is 5.72 s. Density functional theory (DFT) results show that the modification of CQDs improves the adsorption capacity of WO3@CQDs for 2-butanone gas molecules and changes the refractive index of the material. The sensor has the advantages of small volume, high sensitivity and a low LOD, which is of great significance for the detection of trace 2-butanone gas.