Compared to the single emission intensity based sensors, the ratiometric fluorescence assay has achieved improved sensitivity and accuracy by providing built-in correction. However, the dual signals on and ratiometric methods have rarely been reported. Here, a novel strategy for constructing dual fluorescence signals on and ratiometric mercury sensing system is proposed using two kinds of fluorescence dyes (4′,6-diamidino-2-phenylindole (DAPI) and N-methylmesoporphyrin IX (NMM)) and two DNA sequences with both thymine (T)-rich and guanine (G)-rich at two ends. In the presence of Hg²⁺, T-rich segments cooperatively coordinate with Hg²⁺ due to the specific and strong affinity between T–T mismatched base pairs and Hg²⁺, which causes the formation of the split G-quadruplex by two G-rich segments at the other ends. So, both the fluorescent dyes of DAPI and NMM selectively intercalate into dsDNA and G-quadruplex DNA separately, and their fluorescence at 455 nm and 610 nm were enhanced accordingly. Under the experimental conditions employed here, the ratiometric signal was proportional to the Hg²⁺ concentrations from 0.05 to 3 μM. The limit of detection (LOD) was estimated to be 8 nM based on 3s/m rule. The Hg²⁺ concentration in FCS has been successfully determined, further demonstrating the potential utility of the novel system.

与基于单发射强度的传感器相比，比率荧光测定法通过提供内置校正功能，提高了灵敏度和准确性。但是，很少有关于双信号接通和比率测量方法的报道。在此，提出了一种使用两种荧光染料（4'，6-二mid基-2-苯基吲哚（DAPI）和N-甲基间卟啉IX（NMM））和两种DNA在比例汞感测系统上构建双荧光信号的新策略。在两个末端都富含胸腺嘧啶（T）和鸟嘌呤（G）的序列。在存在Hg ²⁺的情况下，由于T–T错配碱基对与Hg ²⁺之间的特异性和强亲和力，富T片段与Hg ²⁺协同配合，这会导致另一端的两个富含G的片段形成分裂的G四联体。因此，DAPI和NMM的荧光染料分别选择性地插入dsDNA和G-四链体DNA中，从而分别增强了它们在455 nm和610 nm处的荧光。在此处采用的实验条件下，比例信号与Hg ²⁺浓度成比例，为0.05至3μM。根据3 s / m规则，检测限（LOD）估计为8 nM 。已成功确定了FCS中Hg ^2+的浓度，进一步证明了该新型系统的潜在用途。