A Simple Benzo[d]thiazole-Based Schiff Base Probe for Selective Fluorometric Detection of Al3+ Ions: Validation Through DFT, Test Strips, Fish Pieces, Cellular Imaging, and Real Water Investigations

The use of one-step products and their applications in sensory applications has gained much importance. Herein, Schiff’s base fluorescent turn-on sensor, namely FBTS, was synthesised via a condensation reaction between 6-fluorobenzo[d]thiazol-2-amine and 2-hydroxybenzaldehyde. The probe FBTS exhibits an intense “turn-on” blue fluorescence upon binding to Al3+ ions in a dimethyl sulfoxide–water (DMSO–H2O (8:2, v/v)) medium. From photoluminescence (PL) titrations, the detection limit (LOD) for Al3+ is estimated to be 0.14 microM, and the Benesi–Hildebrand plot-based association constant (Ka) of 5.4 × 104 M−1 confirm a strong association between FBTS and Al3+. Negligible interference is observed in the presence of other metal ions. From the pH effect studies, the optimal pH range for Al3+ detection is 7–9. The recyclable reversibility of FBTS + Al3+ complex has been demonstrated via the sodium salt of ethylenediaminetetraacetic acid (Na2-EDTA) chelation. A Job’s plot and interrogations, such as high-resolution mass spectrometry (HR-MS), 1H-nuclear magnetic resonance (NMR) titration, and density functional theory (DFT), verified the 1:1 stoichiometry of binding between FBTS and Al3+. Based on multiple analyses, the binding mode and mechanism have been detailed. In addition, the practical application of FBTS for detecting Al3+ is demonstrated using the strip paper method, fish analysis, spiked real sample analysis, and cellular imaging.