Optical fiber sensors for heavy metal ion sensing

The ecological environment suffers from multiple pollution from many aspects, and the heavy metal ions (HMI) pose a significant threat to human health. Detecting these ions is challenging due to their trace amounts and diverse types. Optical fiber sensors offer numerous advantages over conventional techniques in HMI sensing, including small size, quick response, resistance to electromagnetic interference, and long-range monitoring capabilities. In this paper, several optical methods for HMI detection have been described, namely fluorescence, fiber grating, fiber modal interference, surface plasmon resonance, and optical absorbance. The principles, structures, and sensitive materials of these methods are discussed in detail. The advantages and disadvantages of each approach are illustrated to facilitate a better comparison. Furthermore, the current status and future directions for the development of HMI optical fiber sensors are also discussed, which could enlighten the future HMI sensor design.