A Superstable Luminescent Lanthanide Metal Organic Gel Utilized in an Electrochemiluminescence Sensor for Epinephrine Detection with a Narrow Potential Sweep Range

Metal organic gels (MOGs) as a new type of porous soft-hybrid supramolecular material have attracted widespread interest in various aspects due to their unique optical properties. In this work, we report a novel electrochemiluminescence (ECL) emission (679 nm) lanthanide MOG, which has been synthesized by a simple and rapid method at room temperature. This MOG (Tb-Ru-MOG) consists of a central metal ion, terbium (III), and two different ligands, tris­(4,4′-dicarboxylicacid-2,2′-bipyridyl) ruthenium (II) dichloride (Ru­(dcbpy)₃²⁺) and 4′-(4-carboxyphenyl)-2,2′:6′,2″-terpyridine (Hcptpy). Compared with the classic system of tris­(2,2′-bipyridyl) ruthenium (II) dichloride (Ru­(bpy)₃²⁺)/S₂O₈^2–, Tb-Ru-MOG/S₂O₈^2– owns a narrower potential sweep range (0.00 to −0.85 V) and a more stable and stronger ECL signal. Interestingly, the ECL intensity only decreased 2.0 and 0.1% after continuous scanning for 8000 s and storing at room temperature for 3 months. The possible ECL mechanism has been discussed in detail, which is mainly attributed to the internal synergies (antenna effect and energy transfer) and external co-reactant. Inspired by the unique luminescence characteristics of Tb-Ru-MOG, the application in electroanalytical chemistry was identified by the ECL on–off response for epinephrine with a linear range from 1.0 × 10^–10 to 1.0 × 10^–3 mol·L^–1 and a detection limit of 5.2 × 10^–11 mol·L^–1. The results suggest that the as-proposed Tb-Ru-MOG will provide a robust pathway for new ECL luminophores in analysis.