Post-functionalized MOF-based optical fiber SPR sensor for high-sensitivity and broad-range Hg²⁺ detection

We develop a metal-organic framework (MOF)-functionalized fiber sensor for the detection of mercury ions (Hg²⁺) featuring high sensitivity, strong specificity, and a wide detection range. The sensing platform is constructed based on optical fiber surface plasmon resonance (SPR), where UiO-66-NH₂ is anchored on the gold film of an optical fiber to initially enhance sensitivity, leveraging its large specific surface area. Subsequently, 4-Amino-6-hydroxy-2-mercaptopyrimidine (AHMP) is grafted onto the UiO-66-NH₂ via post-functionalization, introducing thiol-containing recognition sites with strong affinity for Hg²⁺. Additionally, the hydroxyl groups of AHMP and the bidentate nitrogen on the pyrimidine ring provide additional binding sites, thereby enabling a broader detection range. The proposed sensor achieves real-time online monitoring over a broad range of 0.1-400 μg/mL, with a limit of detection as low as 0.058 μg/mL. Furthermore, the sensor exhibits much higher recognition ability toward Hg²⁺ than other heavy metal ions, successfully realizing the specific selectivity and detection of Hg²⁺. These excellent performances highlight its potential for practical aqueous Hg²⁺ sensing.