Efficient detection of Picric acid by pyranone based Schiff base as a chemosensor

Abstract

Keeping in mind the necessity to prepare a budget friendly chemosensor for the effortless and convenient sensing of one of the explosives i.e., Picric acid, a Schiff base 3-[-1-(4-fluoro-phenylimino)-ethyl]-4‑hydroxy-6-methyl-pyran-2-one (DFA) was synthesized by the condensation reaction between dehydroacetic and 4-fluoroaniline in ethanol solvent and characterized through analytical spectral techniques. The sensing capability of Schiff base for Picric acid as compared to other nitro explosives was examined by means of UV–Vis absorbance studies. A considerable band shift in Schiff base DFA′s absorbance band for Picric acid while irrelevant changes for the rest of explosives showed DFA′s selectivity towards Picric acid. The binding stoichiometric ratio was found to be 1:1 for DFA: Picric acid adducts which was deliberated from the job′s plot and confirmed by 1H NMR titration. The Association constant and Limit of detection were acquired to be 1.3 × 105 M−1 and 6.92 × 10−7 M respectively using Benesi-Hildebrand (B-H) equation. The sensing power of Schiff base DFA showed high selectivity and sensitivity as addition of competitive explosives showed no alteration in its detection towards Picric acid also the applicability at almost every pH and stability over an extensive time period showed DFA supremacy for Picric acid detection. DFT calculations were carried for the confirmation of theoretical structural relationships and actual absorption data. Aggregation study were too conducted in THF /water Schiff base solution and a maximum in THF /70% water solution showed aggregation at its utmost in Schiff base at 70% water solution and this was further confirmed using FESEM images.