A self-assembly tb-DNA coordination polymer based on dual-functional aptamer: Enhanced stability and hg(II) sensing performance

Hg(II) is a widespread environmental contaminant with high toxicity and severe adverse effects on human health. Although aptamers are commonly used as recognition elements for Hg(II), their binding performance is highly susceptible to pH. In this study, we designed a dual-functional Hg(II)-specific aptamer and developed a biosensor based on Tb(III)-DNA self-assembled coordination polymers (Tb-DNA CPs) for the rapid detection of Hg(II). In the designed aptamer, the G-rich region functions as a luminescent antenna ligand to sensitize Tb(III) emission, while the T-rich region serves as the Hg(II) recognition unit. The resulting Tb-DNA CPs retained 90.2% of their original fluorescence intensity after 30 days in aqueous solution and demonstrated high stability over a broad pH range (pH 4–11). This improved stability is attributed to the role of Tb(III) as a structural crosslinker that promotes the assembly of coordination polymers. The sensor exhibited a limit of detection (LOD) of 3.89 nM for Hg(II), with a linear response range of 5 to 250 μg·L −1 . In vegetable samples, Hg(II) was rapidly quantified with recoveries of 96.49% to 113.40% and RSDs of 1.98%–4.83%. Mechanistic analysis indicated that the sensing response of the Tb-DNA CPs was mainly driven by photoinduced electron transfer (PET) and Hg(II)-induced conformational changes. This work overcomes the pH-dependent limitation of conventional aptamer-based sensors and provides a practical platform for on-site Hg(II) monitoring. The Tb-DNA CP strategy also offers a versatile foundation for the development of stable lanthanide-based biosensors.