Engineering a self-sufficient ECL system: Oxygen-vacancy-driven O2 generation and nanozyme confinement for bioanalysis.

Oxygen vacancies in nonnoble metal nanocatalysts, while extensively explored for oxygen evolution reactions (OER), have rarely been harnessed for electrochemiluminescence (ECL) immunosensing. In this work, we report the rational construction of a novel Fe-Co-CeO2@Ti3C2(OH)2 heterostructure, incorporating Fe-Co dual active sites and abundant oxygen vacancies, through an energy-free co-deposition strategy for efficient OER under near-neutral conditions. Notably, Fe-Co-CeO2@Ti3C2(OH)2 heterostructure not only enhances OER activity but also the oxygen vacancy enriched CeO2 nanoparticles of the heterostructure facilitate superoxide radical (O2•-) generation within the luminol system in the absence of conventional co-reactants (e.g., H2O2 or dissolved O2). In addition, FeCo-NH2-BDC was employed as a signaling probe, whose intrinsic oxidase mimetic activity catalyzes O2 to O2•-, further amplifying the ECL response. By integrating these multiple amplification pathways, we developed a novel biosensing platform for the highly sensitive detection of carcinoembryonic antigen (CEA). The ECL signals were quantified using both a photomultiplier tube (PMT) and a smartphone based visual readout, achieving linear response ranges of 10 pg mL-1-25 ng mL-1 (LOD: 6.35 pg mL-1) and 35 pg mL-1-50 ng mL-1 (LOD: 12.42 pg mL-1), respectively. This work provides a powerful approach for high performance bioanalysis and offers a promising avenue toward the development of ultrasensitive, user friendly diagnostic devices.