Visible self-luminous indium-based metal–organic framework for electrochemiluminescence detection of Hg2+

Herein, we report a self-luminous metal–organic framework (MOF) with a three-dimensional (3D) cubic structure (i.e., RuIn-MOF) prepared by coordinating tris(4,4′-dicarboxylicacid-2,2′-bipyridyl)ruthenium(II) dichloride (i.e. Ru(dcbpy)32+) with InCl3. RuIn-MOF exhibits excellent electrochemiluminescence (ECL) performance and emits red light that is visible to the naked eye. The 3D self-luminous RuIn-MOF not only exists stably in the aqueous environment, but also uses Ru(dcbpy)32+ as its organic ligand to effectively increase the loading of chromophores, which effectively improves the luminescence efficiency. RuIn-MOF possesses a large specific surface area and abundant pore, and its porous structure can enrich the co-reactants, which further improves the luminescence efficiency. Notably, the UV–vis absorption spectra of NiFe-based nanocube and the AuNPs overlap with the ECL emission spectrum of RuIn-MOF; the ECL signal is doubly quenched through resonance energy transfer (RET), which significantly improves sensitivity. Accordingly, we prepared a double-quenching ECL sensor based on the RET strategy with RuIn-MOF as the ECL signal probe, which captures Hg2+ through specific thymine-Hg2+-thymine-type (T-Hg2+-T) interactions and relies on NiFe-based nanocube@Au as the quenching agent. The developed sensing strategy rapidly and efficiently detects Hg2+ in the 10−14 to 10−5 mol L−1 range, with a limit of detection of 2.19 × 10−16 mol L−1.