Aggregation-induced emission coupled with dual quenching factor induced "on-off-on" electrochemiluminescence sensor...

The multi-signal conversion "on-off-on" mode has attracted considerable attention due to its high sensitivity. We developed a novel "on-off-on" electrochemiluminescence (ECL) sensor, in which an Ag-MOF with coordination-triggered aggregation-induced emission (AIE) served as the emitter and polydopamine-modified Fe-MOF (PDA@Fe-MOF) as the quencher for the sensitive detection of malathion (MAL). The rigid Ag-MOF, assembled from 1,1,2,2-tetrakis(4-(pyridin-4-yl) phenyl) ethene (TPPE) ligands, not only increased the loading capacity of the luminescent TPPE molecules but also effectively restricted their intramolecular motions, thereby suppressing non-radiative relaxation and resulting in pronounced ECL enhancement. Meanwhile, the porous architecture of Ag-MOF facilitated the diffusion and excitation of TPPE by coreactants, further improving the emission efficiency. In addition, PDA@Fe-MOF exhibited a dual quenching effect: it not only enabled resonance energy transfer but also efficiently scavenged electrochemically generated co-reactive radicals, ultimately leading to highly effective signal suppression. By integrating a competitive aptamer strategy, the constructed Ag-MOF-based "on-off-on" ECL aptasensor achieved sensitive MAL detection across a wide dynamic range (1 ×10^-14 mg/mL to 1 ×10^-7 mg/mL) with a detection limit of 2.54 × 10^-15 mg/mL, and it was successfully applied to the determination of MAL in cabbage and white tea samples. This method provided a promising platform for MAL monitoring in food and demonstrated considerable potential for practical applications.