Construction of a luminescent sensor based on a lanthanide complex for the highly efficient detection of methyl...

A highly sensitive and selective luminescent sensor for the detection of methyl parathion (MP) pesticide was described in this study. The target molecule HL was synthesized by modifying the structure of 4-hydroxybenzlidene imidazolinone (HBI) with nitrogen-containing heterocyclic 1,10-phenanthroline. In the presence of Eu³⁺, a HL-Eu³⁺ complex was formed which could emit strong red fluorescence due to the removal of coordinated water molecules and an intramolecular energy transfer from HL to Eu³⁺. Addition of MP into the strongly fluorescent solution of HL-Eu³⁺ induced quenching of the complex's fluorescence, and this quenching behavior occurred because of the competition coordination of MP and HL for Eu³⁺. A calibration curve was developed that related the extent of fluorescence quenching to MP concentration, making the HL-Eu³⁺ system a sensitive and selective fluorescent sensor for MP. Under the experimental conditions, the detection limit for MP was down to 95 nM based on LOD = 3σ/S. Moreover, the fluorescence assay developed here allowed the detection of MP in two different types of real samples including pond water and pear juice, and satisfactory results demonstrate that this fluorescent sensor based on HL-Eu³⁺ has potential application in environment and food analysis.