Aggregation-Induced Electrochemiluminescence of Silica-Confined\nTetraphenylethylene with Pd Nanocube-Loaded Co<sub>3</sub>O<sub>4</sub> Nanosheets as a Coreaction Accelerator for Sensitive Bioanalysis

Aggregation-induced\nelectrochemiluminescence (AIECL) provides a\nnew approach for the development of novel electrochemiluminescence\n(ECL) strategies. Herein, a biosensor was constructed by incorporating\n1,1,2,2-tetra(4-carboxylphenyl)ethylene (H<sub>4</sub>TCPE) into a\nmesoporous silica nanosphere (MSN) to obtain a highly organized AIECL\nluminophore of (MSN-H<sub>4</sub>TCPE) for signal antibody (Ab<sub>2</sub>) labeling and using Pd nanocube (NC)-loaded Co<sub>3</sub>O<sub>4</sub> nanosheets (NSs) (PdNCs/Co<sub>3</sub>O<sub>4</sub>NSs) as a novel coreaction accelerator. The confinement of H<sub>4</sub>TCPE molecules in the MSN restricted the intramolecular rotation\nand thus enhanced the radiation transition of H<sub>4</sub>TCPE. In\naddition, the PdNCs/Co<sub>3</sub>O<sub>4</sub>NSs exhibited efficient\nmutual conversion of the Co<sup>2+</sup>/Co<sup>3+</sup> redox couple\nwith the perfect catalytic performance of PdNCs and facilitated the\ndecomposition of the coreactant, leading to a substantial enhancement\nin ECL signal. Subsequently, the localization and fixation strategy\nwith HWRGWVC (HWR) heptapeptides as a specific antibody immobilization\nagent was introduced, which further maintained the biological activity\nof the antibody on the PdNCs/Co<sub>3</sub>O<sub>4</sub>NSs and MSN-H<sub>4</sub>TCPE surface and significantly improved the incubation performance.\nBenefiting from the perfect sensing strategy, the obtained ECL immunosensor\nrevealed an admirable manifestation for the precise detection of neuron-specific\nenolase (NSE) with a broad concentration range of 1 fg/mL to 5 ng/mL\nand a detection limit of 0.33 fg/mL.