Inner filter effect mediated triple-signal response of a novel colorimetric, fluorescent, and phosphorescent sensing system for accurate detection of mercury(Ⅱ) ions under multiple scenarios

Colorimetric, fluorescent, or phosphorescent sensing methods are powerful tools for mercury ion detection and determination. However, single- or dual-signal readouts generated by one or two of these techniques cannot be applied in various practical scenarios due to the different requirements for mercury ion (Hg2+) detection. Herein, a novel colorimetric, fluorescent, and phosphorescent triple-signal readout method was developed for the rapid, sensitive, and accurate detection of Hg2+ with high anti-interference. Due to the inner filter effect (IFE), the fluorescence and phosphorescence of Mn2+-doped Zn2GeO4 nanorods (ZGO:Mn NRs) were first quenched by hemi-cyanine dye (HCD). However, after adding Hg2+ ions, the absorption peak of HCD shifted from 565 nm to 464 nm, and the color changed from purple to yellow. The quenched fluorescence and phosphorescence of ZGO:Mn NRs were restored by the elimination of IFE through HCD coordination with Hg2+. The resulting triple-signal response displayed linear detection ranges toward Hg2+ of 2–11, 8–35, and 57–134 μM with detection limits of 0.103, 0.032, and 2.346 μM, respectively. When the method was used for the detection of Hg2+ in spiked real water and traditional Chinese medicine samples, it showed remarkable color changes and satisfactory recoveries in the range of 91.48 % to 108.51 %. In the complex matrixes of whitening creams or emulsions, the phosphorescent signal readout mode was less susceptible to the interference of background luminescence. Overall, this proposed method will greatly broaden multi-signal readout modes’ applicability under multiple scenarios such as applications in medical diagnostics, food safety, and environmental monitoring.