An electrochemiluminescence sensor based on lanthanide bimetallic MOFs with a "cascade sensitization mechanism" for...

Lanthanide metal-organic frameworks (Ln-MOFs) broaden the optical sensing applications of lanthanide ions due to the antenna effect between organic ligands and metals. However, the sensitization ability of the ligand to metal ions is limited, and maximizing the sensitization of the electrochemiluminescence behavior of Eu³⁺ is still a challenge for the application of Ln-MOFs. Therefore, under the guidance of the "cascade sensitization mechanism" based on the antenna effect sensitizing the electrochemiluminescence of bimetallic Ln-MOFs, we proposed Eu/Tb-MOFs with high luminescence intensity as a signal probe. According to the antenna effect, the conjugated structure and high extinction coefficient of the benzene ring of 2-amino terephthalic acid (NH₂-BDC) can enhance the ECL luminescence intensity of Eu/Tb-MOFs. Tb³⁺ can act as an energy bridge between NH₂-BDC and Eu³⁺, buffering the energy gap. The bimetallic sensitization is formed between Tb³⁺ and Eu³⁺, which can inhibit the reverse internal flow of energy and ensure the high luminous efficiency of Eu³⁺. In addition, the nanosphere mixed valence Fe₃O₄ as a co-reactant accelerator promotes the formation of transient free radical SO₄^•- through the valence change of Fe²⁺/Fe³⁺. The ECL immunosensor constructed by luminophores Eu/Tb-MOFs and nanosphere Fe₃O₄ provided a new explanation for the ECL self-luminous of Eu/Tb-MOFs.