An interferometric optical fiber sensor based on ion-imprinted sodium alginate for Pb(II) detection

• The sensor is prepared by combining alginate-based hydrogel with optical fiber for lead ion measurement. • The sensor has high sensitivity, good linearity, excellent repeatability and significant selectivity to lead ion. • The sensor has simple structure and low production cost. • Good application prospects in the field of environmental pollution detection and control. A kind of Pb 2+ optical fiber sensor is demonstrated with high sensitivity, good linear responding, and simple fabrication. The Fabry-Perot interference structure is composed of single-mode optical fiber, glass capillary and hydrogel. Sodium alginate crosslinks with PbCl 2 to form lead alginate hydrogel by ion-imprinted method. The typical sensor is tested in solutions with different concentrations by Pb 2+ responding experimental system. The sensitivity of sensor to Pb 2+ detection within the concentration range of 0 to 2.5 mg/L is 1.78475 nm/(mg/L), with a linearity of 0.983. The effect of sodium alginate concentration on sensor response were investigated. With increased sodium alginate mass fraction, the sensor sensitivity decreased. The sensor temperature sensitivity was also investigated. Compared with Pb 2+ responding, low temperature sensitivity cannot cause significant cross-responding impact. The repeatability of sensor was tested by six repeated measurements after deionized water desorption. The experiment results showed good repeatability for Pb 2+ responding. The responding selectivity is tested by responding experiments of different other icons, such as Cu 2+ , Cr 3+ , Mn 2+ , Fe 3+ , and Zn 2+ . The experiments results showed that the Pb 2+ responding sensitivity is much higher.