Multifunctional Fluorescent Schiff Base Probe Derived From Chlorosalicylaldehyde for Selective Detection of Proteins, Nitroexplosives, Metal Ions and Antibiotics

Multifunctional fluorescent chemosensors capable of detecting chemically diverse analytes using a single molecular platform are increasingly valuable for environmental monitoring and biomedical analysis due to reducing analytical cost, time, and complexity. However, most Schiff base probes are limited to single‐analyte detection or operate through a single sensing mechanism. In this study, a new Schiff base probe, ClSNP , synthesized from 3,5‐dichlorosalicylaldehyde and N‐phenyl‐o‐phenylenediamine, exhibited a fluorescence “turn‐off” response toward Cu 2 + and Co 2 + ions in a CH 3 CN/H 2 O medium with high selectivity even in the presence of competing metal ions. Job's plot analysis confirmed a 1:1 binding stoichiometry, with detection limits of 1.79 and 3.40 µM for Cu 2 + and Co 2+ ions, respectively, both below WHO‐permitted levels. Additionally, it selectively detected picric acid (PA) in THF with a detection limit of 2.49 µM and responded to antibiotics, including nitrofurantoin and metronidazole. It showed a “turn‐on” fluorescence enhancement at 460 nm upon binding with bovine serum albumin (BSA) with a detection limit of 1.28 µM, attributed to restricted intramolecular rotation, supported by a molecular docking study. The probe demonstrated high sensitivity, good selectivity, and real‐sample applicability, offering a versatile, cost‐effective, and mechanism‐switchable sensing platform.