Luminescent Lanthanide Complexes as Sensors for Organophosphorus Nerve Agents

Luminescent europium complexes were synthesized and investigated as optical sensors for organophosphorus chemical warfare agents (nerve agents). The objective of this study is to develop a rapid “turn-off” detection method based on fluorescence quenching. Europium thenoyl-trifluoroacetonate complexes with and without co-dopants (Tb3+, Nd3+, Pr3+) were prepared and characterized by infrared spectroscopy, UV-vis absorption and photoluminescence emission. The Eu(III) tris(thenoyltrifluoroacetonate)-1,10-phenanthroline [Eu(TTA)3(phen)] complex exhibited intense red luminescence, which was selectively quenched in the presence of organophosphorus nerve agent simulants. In particular, dimethyl methylphosphonate (DMMP) and malathion (an organophosphate pesticide simulant) caused significant fluorescence quenching of Eu(TTA)3(phen). Photoluminescence (PL) spectra showed a progressive decrease in Eu3+ emission intensity (especially the peak at 612 nm) with increasing analyte concentration, with complete quenching at around 1.2 µM malathion. The lanthanide-based sensing mechanism is attributed to ligand displacement or energy transfer interactions between the nerve agent analogs and the Eu3+ complex. These findings demonstrate a simple and fast optical method for detecting phosphorous nerve agent compounds and the results are compared with existing sensor technologies. The Eu3+ complex sensor demonstrates potential for field-deployable detection of chemical warfare agents, with potential advantages in selectivity and real-time response.