Highly sensitive optical fiber SPR sensor based on chitosan for the detection of trace Cu2+ ion in aqueous solution

In this paper, a highly sensitive fiber-optic sensor was proposed for the detection of Cu2+ traces in aqueous solution which has a nonnegligible impact on human health. Based on the principle of SPR, a uniform chitosan (CS) material was coated on a multimode fiber-single mode fiber-multimode fiber (MSM) structure with silver layer by glutaraldehyde (GLA) and graphene oxide modification. The amino and hydroxyl groups in the material have a recognition function for Cu2+, which can chelate with Cu2+ and change the ambient layer refractive index of the sensor leading to a shift in the SPR spectrum. Trace Cu2+ can be detected by monitoring the shift in the resonance wavelength of the SPR spectrum. The results illustrate that within the range of 0.1 similar to 1 mg/L Cu2+ concentration, as the Cu2+ concentration increasing, the SPR spectrum undergoes a red shift and the maximum detection sensitivity of Cu2+ ions achieves 49.466 nm/(mg/L), with a good linearity of 0.996. The temperature experimental results indicate that the sensor has good stability at room temperature (25 similar to 35 degrees C). The stability and repeatability characteristics of the system are also investigated. The good performance provides a new method in trace Cu2+ in-situ detection.