An easy prepared probe, BHMMP, was designed and synthesized, which displayed a significant fluorescence enhancement (over 38-fold) and obvious color change in the recognition of Al³⁺. The binding ratio of probe BHMMP to Al³⁺ was determined as 1:1, according to Job plot. The binding mechanism was fully clarified by the experiments, such as FT-IR spectrum, ESI–MS analysis, and ¹H NMR titration. A DFT study further confirmed the binding mode of BHMMP to Al³⁺. The limit of detection (LOD) for Al³⁺ was determined as low as 0.70 µM, based on the fluorescence titration of BHMMP. Moreover, the results from real sample experiments, including real water samples, test papers, and cell images, well-demonstrated that BHMMP was capable of sensing Al³⁺ in environmental and biological systems.

Heavy metal cadmium (II) residuals have inflicted severe damage to human health and ecosystems. It has become imperative to devise straightforward and highly selective sensing methods for the detection of Cd²⁺. In this work, a ratiometric benzothiazole-based fluorescence probe (BQFA) was effortlessly synthesized and characterized using standard optical techniques for the visual detection of Cd²⁺ with a change in color from blue to green, exhibiting a significant Stokes shift. Moreover, the binding ratio of BQFA to Cd²⁺ was established as 1:1 by the Job’s plot and was further confirmed by FT-IR and ¹HNMR titrations. The ratiometric fluorescence response via the ICT mechanism was confirmed by DFT calculations. Furthermore, the limit of detection for detecting Cd²⁺ was determined to be 68 nM. Furthermore, it is noteworthy that BQFA showed good performance in real water samples, paper strips, smartphone colorimetric identification, and cell imaging.