Visualized accurate determination of ultra-trace Hg²⁺ using aptamer-conjugated electrochemiluminescence device

Mercury ion (Hg²⁺) is a ubiquitous and highly toxic contaminant that poses severe threats to ecological integrity and human health, yet conventional detection techniques often struggle to reconcile ultra-trace sensitivity, on-site visualization, and adaptability to complex matrices. Herein, we developed a novel aptamer-conjugated electrochemiluminescence (ECL) device for accurate, visual detection of ultra-trace Hg²⁺, constructed by modifying Hg²⁺-specific double-stranded DNA (dsDNA) onto poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(1,4-benzo-{2,1,3}-thiadiazole)] (PFBT)-based polymer dots (Pdots) as high-efficiency ECL emitters, and loading Rhodamine B (RhB) as a quencher via resonance energy transfer (RET). Hg²⁺ binding induces stable T-Hg²⁺-T pair formation, selectively releasing RhB and restoring the quenched ECL signal of Pdots for detection. This device exhibits a broad linear response to Hg²⁺ over 1 ng/L-10 μg/L, ultra-low limit of detection (LOD) of 1.6 pg/L in aqueous samples and as low as 0.3 fg/g in solid samples. The device also shows robust selectivity against various interfering ions (K⁺, Na⁺, Cd²⁺, Pb²⁺, CH₃Hg⁺, etc.), and long-term stability for up to 3 months under ambient storage. Practical validation confirms accurate Hg²⁺ detection in diverse real matrices, including natural waters (Gan River, Qinling spring, Dushu Lake, etc.), aquatic products (Culter alburnus, Mytilus edulis, Macrobrachium nipponense, etc.), and food/medicinal materials (Glycyrrhizae Radix, Talcum, etc.). Bridging ultra-trace sensitivity and on-site visualization, this tool enables reliable environmental monitoring and food/medicinal supervision, with a modular design offering broad potential for detecting other trace contaminants to advance public health and ecological risk management.