Mercapto‐Functionalized Black Phosphorene Sensitized Optical Sensing System: amol‐Level Ultra‐Trace Selective Detection of Mercury Ions

ABSTRACT The detection of ultra‐trace mercury ions (Hg 2 + ) is a critical step for environmental monitoring and risk assessment, yet conventional detection technologies suffer from weak interfacial refractive‐index perturbation and susceptibility to interference from non‐specific adsorption in multi‐ion matrices. To address these issues, this study fabricates a mercapto‐functionalized black phosphorene (BP‐SH) functional layer on the surface of the BK7–Au structure, which achieves enhanced interfacial electric field, amplified angular sensitivity, and sulfur‐site functionalization simultaneously. Experiments confirm that this novel sensor elevates the angular sensitivity from 135 deg/RIU to 265 deg/RIU, exhibits a stable response to Hg 2 + in the concentration range of 10 − 1 7 –10 − 1 3 M, and achieves an attomolar‐level LOD of 10 − 1 8 M. Comparative tests with other interfering heavy‐metal ions demonstrate that the designed sensor exhibits high selectivity toward Hg 2 + . Mixed‐ion and real‐water measurements further validate Hg 2 + discrimination in complex matrices. This research provides a novel sensing strategy for the ultra‐trace analysis of environmental mercury ions, effectively improving the sensitivity and selectivity of low ‐ concentration Hg 2+ detection.