Dual-Mode "Turn-On/Off" Chemosensor for Trivalent Cations and Arsenate: Live Cell and Logic Gate Functionality.

This study introduces a novel chemosensor (RbT) for the selective and highly sensitive detection of Al³⁺, Fe³⁺, Cr³⁺ (M³⁺) ions and arsenate anion (AsO₄³−). The sensor was synthesized through the strategic integration of Rhodamine B, phosphorus oxychloride, and Tryptamine, and operates via a chelation-enhanced fluorescence (CHEF) mechanism in an H₂O/ACN (3:7, pH 7) system. Upon coordination with M³⁺ ions, RbT exhibits a strong fluorescence enhancement and a visible deep-pink color change, enabling dual spectroscopic and visual detection. The sensor exhibits remarkable sensitivity within the micromolar range, with detection limits of 3.2 nM for Al³⁺, 5.6 nM for Fe³⁺, and 15.4 nM for Cr³⁺. Job’s plot and mass spectrometry confirm a 1:1 metal-ligand binding stoichiometry. The RbT-Al³⁺ complex further detects AsO₄³⁻ via a fluorescence quenching mechanism, achieving a detection limit of 2.8 nM. The reversible “Off-On-Off” fluorescence response enabled the construction of an INHIBIT molecular logic gate. The interaction between RbT and M3+ was reversible upon the addition of EDTA. Cytotoxicity and cell imaging studies using SHSY5Y and HeLa cell lines demonstrate low toxicity and efficient intracellular sensing. These results highlight RbT as a promising candidate for environmental analysis and bioanalytical applications.