Water-Driven Cascade Specific Detection of Al(III)/Hg(II) and CN^–/GSH in Real Water Samples

This work presents novel rhodamine hybrids with <i>para</i>-quinone methide groups as ion-sensing probes. The probes, <b>P1</b> and <b>P2</b>, exist in both open and closed ring conformations, making them promising candidates for sensors due to their distinct absorption and fluorescence properties. Fluorescence studies demonstrated that <b>P1</b> acts as a "turn-on" sensor for Hg-(II) in water, while <b>P2</b> responds similarly to Al-(III) in water-methanol solutions. The detection limits (LODs) were determined to be 389 nM for Hg-(II) and 857 nM for Al-(III). In addition, the probes exhibit "turn-off" responses to cyanide and glutathione in the presence of Al-(III) and Hg-(II), with LODs of 680 nM and 1.21 μM, respectively. By visually inspecting colorimetric changes in filter paper and water samples, we also looked into the feasibility of these probes in real-world settings. Overall, this work demonstrates the suitability of probes for the detection of mercury and aluminum in water samples from natural environments.