Enhancing electrochemiluminescence by assembling ACQ ligands into Hf-based metal-organic framework nanosheet: A novel ECL emitter for fabricating ultrasensitive biosensor

Polycyclic aromatic hydrocarbons (PAHs) are classic electrochemiluminescence (ECL) materials. However, the ECL performance of PAHs aggregates in water phase is limited owing to the aggregation-induced quenching (ACQ) effect of PAHs. To surmount this shortcoming, we proposed an innovative strategy for enhancing the ECL performance by assembling PAH derivative ligands into metal-organic framework nanosheets (MONs), which can separate ACQphores to eliminate the ACQ effect. Gratifyingly, the ECL intensity of Hf-DEADB MON (DEADB = 4,4′-(diethylanthracene-9,10-diyl)dibenzoate) prepared according to the strategy was 5.71-fold higher than that of H2DEADB aggregates. This improvement occurred not only because the distance between the ACQphores in the Hf-DEADB MON was enlarged to surmount the ACQ effect but also because the ultrathin porous Hf-DEADB MON could shorten the diffusion pathways of ion/electron and co-reactant, which boosted electrochemical activation of DEADB luminophores. Given the prominent ECL performance of Hf-DEADB MON, it was used to fabricate a hypersensitive biosensor for detecting microRNA-21, displaying a broad response range (100 aM–10 nM) with an ultralow detection limit (24 aM). Overall, our work developed a promising strategy to eradicate the ACQ effect of PAHs for ECL enhancement, thus pointing out a new direction to design high-efficient ECL materials for constructing ultrasensitive ECL sensors.