A multi-responsive chemosensor for selective recognition of Pb2+, Cr3+ and Fe3+ in aqueous media with cellular imaging applications.

We present TAP, a novel multi-ion chemosensor capable of selectively detecting Pb2+, Cr3+, and Fe3+ in fully aqueous solutions. Designed to be cost-effective and facile to synthesize, TAP provides distinct spectroscopic responses: colorimetric detection for Pb2+ and fluorescence "turn-on" signals for Cr3+ and Fe3+. The sensor exhibits strong binding affinities (Cr3+: Kb ≈ 2.0 × 104 M-1; Fe3+: Kb ≈ 1.7 × 104 M-1; Pb2+: Kb ≈ 1.3 × 104 M-1) and remarkably low detection limits (LOD: Cr3+ 23.8 nM, Fe3+ 15.3 nM, Pb2+ 0.56 μM) with corresponding quantification limits (LOQ: Cr3+ 72.1 nM, Fe3+ 46.3 nM, Pb2+ 1.70 μM). These values are significantly lower than those reported for existing systems, underscoring TAP's superior sensitivity. Importantly, TAP's fluorescence-based sensing was successfully applied for intracellular detection of Cr3+ in HepG2 liver cells, confirming its biological applicability. Overall, TAP represents a versatile and practical chemosensor with promising applications in environmental monitoring and biomedical research.