Low Molecular Weight Fluorescent probes for the detection of organophosphates

Rashid Mia, Peter Cragg, Karl J. Wallace

Research output: Contribution to journalArticlepeer-review


Three Low Molecular Weight Fluorescent probes (LMFPs) coumarin-enamine (3a-c) have been synthesized, and their photophysical properties have been studied in different solvent systems (DMSO, CH 3CN, DMF, MeOH, EtOH, Me 2CO, MeCO 2Et, CHCl 3, C 6H 5Me, and C 6H 6). Dimethyl sulfoxide was chosen as the optimum solvent to investigate 3a for organophosphate detection. On deprotonation of the oxime, a significant spectroscopic shift is observed in the UV–Vis spectrum (Δ ≈ 35 nm). The fluorescence spectrum shows a broad featureless band at 535 nm that shifts hypochromically. Both the UV–vis and fluorescence spectra undergo drastic optical responses when the OP-adduct is formed. Diisopropyl chlorophosphate was found to have the most extensive changes among the phosphorus (V) center OPs investigated (diisopropyl chlorophosphate, diisopropyl fluorophosphate (DFP), dimethoate, omethoate, chlorfenvinphos, and carbaryl). The fluorescence turn “off-on” response is a consequence of the PET mechanism, supported by the molecular modeling calculations. A limit of detection was calculated to be 1.1 ppm for DFP (a nerve agent simulant). Fluorescence lifetime studies were carried out, which showed significant decay times for 3a, its oximate, and its DCP-adduct of τ = 1.56, 3.23, and 1.55 ns, respectively, to aid in our understanding of selectivity.

Original languageEnglish
Article number118053
Pages (from-to)380-401
JournalJournal of Luminescence
Publication statusPublished - 13 Mar 2021


  • Fluorescence lifetime
  • Molecular sensors
  • Nerve agents
  • Organophosphates
  • Steady-state fluorescence


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