The rational design of europium complex based electrochemiluminescence sensor for highly efficient carbaryl detection

To address the issue that most of the reported electrochemiluminescence (ECL) sensors are usually subjected to various complicated chemical modifications, we proposed a sensitive ECL sensor by using a neutral mononuclear lanthanide metal europium complex Eu(L)₃ (L = 2-pyrazol-1-yl-6-(1H-tetrazol-5-yl)-pyridine) as luminophore with simple chemical composition for the accurate detection of carbaryl pesticide residues. The three conjugated tridentate pyrazo-pyridine- tetrazol ligands could put significant effect on the physical and chemical behavior of the central Eu³⁺ ion, leading to the excellent luminescent performance of the Eu(L)₃ complex enhanced by "antenna effect" of the auxiliary anionic organic ligands. The naphthol obtained from the hydrolysis reaction of carbaryl in an alkaline working solution could effectively and quantitatively quench the luminescence intensity of the Eu(L)₃ complex, which has been theoretically confirmed by the detailed density functional theory (DFT) and time-dependent DFT (TDDFT) calculations, thus obviously strengthening the target detection capability on carbaryl. Based-on such the idea, the skillfully constructed ECL sensor showed superior carbaryl detection performance with good linearity in the range of 1 pg/mL to 1000 ng/mL, and a satisfied detection limit of 8.8 pg/mL (S/N = 3) under the optimized conditions. The current simple ECL carbaryl detection platform exhibited the conspicuous superiority to those existed commercial ones and thus, more importantly, provided a very promising practical value in the field of environmental detection (oil, soil, water, etc.) of organic phenol pollutants.