Optical Fiber SPR Sensor With Surface Ion Imprinting for Highly Sensitive and Highly Selective Ni2+ Detection

A reflective optical fiber nickel ion (Ni²⁺) sensor based on surface plasmon resonance (SPR) and surface ion imprinting was proposed and demonstrated. The sensor is made of multimode optical fiber with a core diameter of 600 <inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> and coated with a gold film for an exciting SPR effect. To realize highly sensitive and highly selective detection of Ni²⁺, graphene oxide (GO) and Ni²⁺-imprinted Chitosan (IP-CS) are subsequently combined on the sensor surface. The GO can not only act as the intermediate binder between the Au film and the CS but also increase the sensitivity of the sensor. The Ni²⁺ holes on the IP-CS can realize the specific capture of Ni²⁺. The experimental results show that the sensitivity of the sensor to Ni²⁺ is 5.220 nm/[lg(mg/L)] with a limit of detection of <inline-formula> <tex-math notation="LaTeX">$2.393\times 10^{-3}$ </tex-math></inline-formula> mg/L, and the selectivity of the sensor is significantly improved after imprinting. Besides, the sensor has good stability and repeatability, and fast responsiveness.