Fiber optic surface plasmon resonance technology for detection mercury ion

In this paper, a method of detecting mercury ion (Hg²⁺) concentration in water samples by using Thymine-1-aceticAcid (T-COOH) functionalized Au nanoparticles enhanced fiber optic SPR sensor is proposed. Firstly, we coat the surface of the optical fiber with Au film, then assemble a layer of mercaptoethymine on the surface of the Au film, and formed the Au-S bond by chemical reaction between the sulfhydryl group and the Au, and exposed the amine group on the surface of the fiber sensing region. Then we use T-COOH to modify the thymine on the fiber optic by the chemical reaction between amine and carboxyl. Similarly, mercaptoethymine and T-COOH were used to modify thymine on the surface of Au nanoparticles, and the optimal ratio of T-COOH : Au nanoparticles = 3:50 was obtained through modification optimization. Then the sandwich structure of Au-T—Hg²⁺—T-Au NPs was formed when mercury ion was detected, which effectively improved the accuracy and sensitivity of mercury ion detection. Then the concentration of ions is measured. By analyzing the influence of other metal ions and mercury ions in the same concentration of water samples, it is concluded that the fiber optic SPR sensor designed in this paper has high selectivity for mercury ions, so this method has high feasibility.