Bimetallic-Doped Metal–Organic Gel for Efficient Electrochemiluminescence: Staircase-Mediated Energy Transfer and Applications in Epinephrine Detection

This study presents the development of a novel bimetallic-doped metal–organic gel (Tb–Eu-MOG) synthesized by codoping terbium (Tb(III)) and europium (Eu(III)) with the Hcptpy ligand and explores its application in electrochemiluminescence (ECL) for sensitive detection of epinephrine (EP). The Tb–Eu-MOG exhibits unique petal nanoflower-like morphology and remarkable ECL signals, attributed to the dual sensitization effects of Tb(III) and Eu(III) on the Hcptpy ligand. The Tb(III) doping facilitates energy transfer and enhances ECL efficiency through a staircase effect. The Tb–Eu-MOG/K2S2O8 system demonstrates a high ECL intensity, which is significantly quenched in the presence of EP due to its competitive consumption of SO4•– radicals. The ECL intensity shows a linear correlation with the logarithmic concentration of EP in the range of 1.0 × 10–10 to 1.0 × 10–3 M, with a detection limit as low as 48 pM. This work not only expands the potential applications of bimetallic MOGs in the ECL field but also provides insights into the relationship between the central metal ion and the ligand, which is crucial for ECL detection. The alignment of orbital energy levels between the central metal ion and the ligand is identified as a significant mechanism for enhancing ECL. This research offers a promising strategy for the design of highly efficient ECL luminophores and broadens the scope of sensing applications.