Synthesis of Schiff’s-based Chemosensor for Trace Aluminum ion Detection from Pharmaceutical waste water

Abstract

The probe, 1-(1-(Phenyl(pyridine-2-yl)methyl)-1H-benzo[d]imidazol-2-yl)naphthalene-2-ol has been synthesized by the reaction of 2-hydroxy-1-naphthaldehyde and N 1 -(Phenyl(pyridine-2-yl)methyl)benzene-1,2-diamine in 1:1 molar ratio. The probe has been characterized by spectroscopic techniques (FT-IR, UV-Vis, 1 H NMR) and is non-emissive. The sensing mechanism was based on Excited state intramolecular proton transfer and upon binding with the analyte restriction of intramolecular rotation has been happening. The probe selectively binds Al 3+ and upon irradiation at 400 nm in presence of a large number of cations shows high emission (em, 502 nm) in 4:1 H2O/MeOH (v/v) solution and serves as a “turn-on” fluorescence chemosensor. The limit of detection (LOD) for Al 3+ is 3.3 nM (3 method) which is more than 200 times sensitive than that is recommended by the World Health Organization (WHO), 7.4 mM. The probe is stable in the pH range, 2–12 and maximum turn-on response to Al 3+ is observed at pH, 6. Formation of the 1:1 metal-to-ligand complex has been ascertained by Mass spectra, Job’s plot and Benesi-Hildebrand plot (Binding or Association Constant Ka, 41 2.3 10 M −  ). The effluent collected from the pharmaceutical industry has 0.381 mM of Aluminum ion concentration which is trace quantity. A separate in vitro experiment shows that the probe can specifically perceive Al 3+ ion in (Human liver cancer) cell line. This work aims to find a fluorogenic sensor for Al 3+ ions, which has been decided by WHO (World Health Organization) as a potential food and drinking water pollutant and found to be detrimental for human health. We devised a sensor which is capable of detecting 3.3 nM of Al 3+ ion which is by far less than the limit stipulated by WHO