Ion-Imprinted Chitosan-Based Localized Surface Plasmon Resonance Sensor for Ni(2+) Detection

Heavy metals are important sources of environmental pollution and cause disease in organisms throughout the food chain. A localized surface plasmon resonance sensor was proposed and demonstrated to realize Ni(2+) detection by using ion-imprinted chitosan. Au nanoparticles were coated on the multimode fiber to excite the local surface plasmon resonance, and Ni(2+)-imprinted chitosan was then functionalized by using the dip coating technique. Ethylene diamine tetra-acetic acid was used to release the Ni(2+) ions and hence form countless voids. Ni(2+) was refilled into the voids to increase the refractive index of the sensing material, thus realizing the measurement of Ni(2+) by monitoring the wavelength shift in the localized surface plasmon resonant peak. The coating thickness of the Ni(2+)–chitosan gel was optimized to obtain greater sensitivity. Experimental results show that the proposed Ni(2+) sensor has a sensitivity of 185 pm/μM, and the limit of detection is 0.512 μM. The comparison experiments indicated that the ion-imprinted chitosan has better selectivity than pure chitosan.