A label-free and enzyme-free signal-on biosensor for Hg(II) ions was constructed based on T-Hg(II)-T nanoladders and fluorescent DNA-templated silver nanoclusters/graphene oxide nanocomposites (DNA-AgNCs/GO). The T-rich sequences (P1 and P2) were used to capture Hg(II) and form the T-Hg(II)-T nanoladders. C₆G₅C₆ was extended at the 5′ end of P1, used as a template for synthesizing fluorescent DNA-AgNCs. In the presence of mercury ions, the T-Hg(II)-T nanoladders significantly enhanced the emission of AgNCs. GO can attract free P1-C₆G₅C₆ and P2 that were not involved in the formation of T-Hg(II)-T nanoladders, thus employed as the energy acceptor to quench the background fluorescence of AgNCs. The fluorescence enhancement induced by mercury ions can be used for quantitative detection of Hg(II) over the range 0.1–30 nM with a detection limit as low as 7.35 pM. This method was used to detect Hg(II) in the spiked samples of Songhua River water and grass carp, with the recoveries of 97.61%− 103.79% and 96.52%− 105.58% respectively, consistent with the results from atomic fluorescence spectrometry. Obviously, in this assay, enzyme-free signal amplification and signal identification are integrated in the ingenious design of nucleic acid sequences, thus achieving the label-free fluorescence detection of mercury ions.

基于 T-Hg(II)-T 纳米梯和荧光 DNA 模板化银纳米团簇/氧化石墨烯纳米复合材料 (DNA-AgNCs/GO)，构建了一种无标记、无酶的 Hg(II) 离子信号生物传感器。富含 T 的序列（P1 和 P2）用于捕获 Hg(II) 并形成 T-Hg(II)-T 纳米梯。C ₆ G ₅ C ₆在P1 的5'末端延伸，用作合成荧光DNA-AgNCs 的模板。在汞离子存在下，T-Hg(II)-T 纳米梯级显着增强了 AgNCs 的发射。GO 可以吸引免费 P1-C ₆ G ₅ C ₆和 P2 不参与 T-Hg(II)-T 纳米梯的形成，因此用作能量受体来淬灭 AgNCs 的背景荧光。汞离子诱导的荧光增强可用于定量检测 0.1-30 nM 范围内的 Hg(II)，检测限低至 7.35 pM。该方法用于检测松花江水和草鱼加标样品中的Hg(II)，回收率分别为97.61%- 103.79%和96.52%- 105.58%，与原子荧光光谱法结果一致。显然，该检测将无酶信号放大和信号识别整合到核酸序列的巧妙设计中，从而实现了汞离子的无标记荧光检测。