Nanomolar determination of nitrofurans in water via excited-state inter-ligand proton transfer

Qualification and quantification of trace organic contaminants necessitates development of highly efficient sensing system, where excited-state inter-ligand proton transfer (ESILPT) provides a feasible pathway to construct efficient chemo-sensors. Herein, a strategically synthesized lanthanide complex, Eu(DBM)₃(MeOH)₃ (briefly as Eu-DBM-MeOH; DBM = dibenzoylmethane), features two-step ESILPT processes, along with modification on molecular structure and energy band. As a result, Eu-DBM-MeOH exhibits excellent photophysical properties with characteristic luminescence of Eu³⁺ ion. Benefiting from these merits, the Eu-DBM-MeOH complex acts as ultra-sensitive chemo-sensor toward nanomolar-level nitrofuran antibiotics (nitrofurazone and nitrofurantoin) in water, by disrupting ESILPT processes. Combining the advantages on photophysical property and luminescent sensitivity, ESILPT-active compounds are expected to widen and deepen the research on complex-based luminophores, being potentially useful in trace detection and biological imaging.