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Ion-Imprinted Chitosan-Based Interferometric Sensor for Selective Detection of Heavy Metal Ions

Year: 2019

Journal: J. Lightwave Technol., Volume 37, 1-Jun, page 2778–2783

Authors: Ravikumar, Raghunandhan; Chen, Li Han; Hui, Melissa Meow Xin; Chan, Chi Chiu

Keywords: Chitosan; fiber-optic interferometric sensor; heavy metal ion sensor; ion imprinting; photonic crystal fiber (PCF)

A photonic crystal fiber (PCF)-based Mach-Zehnder interferometric sensor using ion-imprinted chitosan for the detection of Ni2+ ions is proposed and experimentally demonstrated. The sensor was fabricated by splicing a small section of the PCF between single-mode fibers. Nickel-adsorbed chitosan was crosslinked with epichlorohydrin (ECH) to increase its mechanical strength, and thereby, to improve the sensor stability and was subsequently imprinted with Ni2+ ions. The sensor was coated with nickel ion imprinted chitosan and was examined with test solutions of various Ni2+ concentrations. The sensor exhibits a Ni2+ detection sensitivity of 0.0632 nm/mu M (nanometer per micromolar) in the linear range and a limit of detection of 0.57 mu M. The cross sensitivity of the sensor was evaluated to other metal ions like Cu2+, Ca2+, and Na+ and also by comparing its performance to a sensor using nonimprinted chitosan. Results have shown better sensor response to Ni2+ ions over other metal ions and an improvement in performance over a nonimprinted chitosan sensor. Investigation was also carried out to examine the effect of crosslinking on the sensor performance by varying the ECH to the chitosan molar ratio (5:1, 10:1, and 15:1) and the sensor achieved its best performance when the molar ratio was 10:1.