Hydrogen bond mediated turn-on sensor: Ultra-sensitive and label free barium-MOF for probing malathion an organophosphate pesticide

The recent trend in the agricultural field mainly focuses on the production of products with good yield by using potent and highly poisonous pesticides without considering their severe hazardous side effects. These materials are present in the soil, water, and air in trace amounts. Therefore, continuous monitoring of organophosphate (OPs) pesticides is essential from a human health perspective because of their unregulated use. In this study, we describe fluorescence enhancement sensing for the selective quantification of OPs in aqueous media. For this, single crystals of oxydiacetic acid functionalized barium metal; [Ba(C4H4O5)(H2O)]n was developed through gel diffusion technique at room temperature. The crystals grown were found to be an effective turn-on luminescent probe in an aqueous medium for the sensing of malathion; one of the widely used pesticide in the agriculture field. The techniques such as Single Crystal X-ray diffraction, FT-IR, UV-Visible Spectroscopy, TG/DTG, photoluminescent spectroscopy, etc. were used for the characterization of these crystals. The sensing experiments clearly showed that the synthesized material suspended in water can sense malathion in aqueous media with a detection limit of 10.6676 mu M/L. From the Benesi-Hildebrand plot, it is clear that there exists a binding interaction between the sensor and the pesticide which is in 1:1 stoichiometry. The PXRD pattern clearly suggests that the material is intact and there is no change in its peak position, as well as no new peaks, has emerged after the sensing experiments. The FT-IR spectra taken after the sensing experiments show peak broadening and peak shift thereby indicating the evidence of hydrogen bonding interactions between electron-withdrawing groups of OPs and electron-rich open metal sites or organic ligand molecules of MOFs. Interestingly, the material retained its sensing ability even after the third cycle of sensing experiments.