Highly Sensitive Optical Fiber Pb2+ Concentration Sensor Based on HEMA/AM/SA Interpenetrating Polymer Network (IPN) Hydrogel

An optical fiber sensor based on a HEMA/AM/SA interpenetrating polymer network (IPN) hydrogel is proposed for monitoring the concentration of Pb²⁺. The Fabry-Perot interference cavity is constructed from a single-mode fiber, a ceramic ferrule, and an IPN hydrogel layer. P (HEMA co AM)/SA IPN hydrogel films were prepared by a step-by-step crosslinking method, which had good mechanical properties, swelling properties, and Pb²⁺ adsorption capacity. The Pb²⁺ concentration changes cause the interference spectrum shift of the sensor. By monitoring the wavelength shift under different Pb²⁺ concentrations, the sensor sensitivity in the range of 0~1 ppm Pb²⁺ concentration in solution is 5.0743 nm/ppm with 0.994 linearity. The influence of different proportions of IPN hydrogel on the performance of the sensor was studied. In the range of 10-90% HEMA, higher sensitivity is obtained by a small weight ratio of HEMA/AM. The sensor stability, repeatability, selectivity, dynamic response, and temperature response are also investigated in experiments. Experimental results demonstrate that the proposed sensor exhibits good stability, sensitivity, repeatability, and selectivity. Owing to its compact structure, straightforward fabrication, low cost, and good sensing performance, this sensor shows strong potential for application in monitoring Pb²⁺ concentrations.