Gold nanoparticle-enhanced D-shaped optical fiber sensor for mercury ion detection

Mercury ions (Hg²⁺) are highly toxic heavy metal ions that pose serious health risks to humans when present at concentrations above the safety threshold. Therefore, the development of a rapid and effective Hg²⁺ detection method is of significant importance. In this study, based on surface plasmon resonance (SPR) technology integrated with COMSOL simulation analysis, a highly sensitive and selective Hg²⁺ sensing system is constructed. Initially, gold nanoparticles and the surface of a fiber-optic gold film are modified by sodium sulfide (Na₂S). In the presence of Hg²⁺, the sulfur ions on the modified gold film and gold nanoparticles specifically bind to Hg²⁺, forming the composite structure Au/S-Hg²⁺-S/AuNPS. Due to the strong electromagnetic coupling between the gold nanoparticles and the gold film, a significant SPR wavelength shift occurs. These results show that the Hg²⁺ sensor has high sensitivity and enhanced selectivity. The detection limit for mercury ions was 8.15 nM, and the recovery rate in real environmental samples was up to 90.1-97.3%. This sensing system provides an alternative method for rapid and accurate determination of mercury content.