Research on lead ion sensing based on micro-nano fiber coupler cascade tilted fiber grating

Abstract

As water pollution becomes increasingly severe, human health is facing threats from heavy metal lead ions in water. Therefore, detecting trace amounts of Pb²⁺ in water has become crucial. Fiber optic sensors have garnered significant attention in the sensor research field due to their small size, high sensitivity, and ease of integration. However, developing a fiber optic sensor capable of detecting Pb²⁺ at the pmol/L level poses a challenge. The study proposes a novel micro-nano fiber coupler cascaded tilted fiber grating (MFC-TFG) sensor, which is modified with glutathione complexed titanium carbide MXene (GSH@Ti₂C) for the detection of Pb²⁺ concentrations in water environments. It exhibits a selective response to Pb²⁺ and achieves a limit of detection (LOD) of 0.624 pM (0.013 ng/dL). In the sensor structure, the cladding modes of the TFG can respond to changes in refractive index (RI) and temperature, while the core mode is only affected by temperature. Consequently, the MFC-TFG sensor can simultaneously detect environmental parameters of RI and temperature. By combining fiber optic designs and optimizing sensitive materials, the study addresses ultra-low Pb²⁺ detection, offering a robust fiber optic solution for heavy metal sensing.