Fluorescent fiber optic sensors find their popularity in online and in-situ detection of metal ions. To be more precise, this type of sensor is different from refractometer-based. Recently, novel fluorescent probes based on biomaterials and luminescent nanomaterials for metal ions attract tremendous attentions, owing to their advantages of simple operation, high sensitivity and rapid response for metals detection. The. A fluid metal ion detection device is designed to solve the issue of heavy metal water quality detection in real life, which is used by a fusion of a side-throw fiber-assisted fluid structure and a long-period fiber grating coated with a metal chelator film. The sensor is capable of sensing RI variations in.