Synergistic catalysis of MoC nanoclusters/Co single-atom sites for H₂O₂-free electrochemiluminescence detection of ascorbic acid.

Ascorbic acid (AA) detection is a prior analyte for food safety and clinical diagnostics, yet traditional electrochemiluminescence (ECL) sensors depend on hydrogen peroxide (H₂O₂) coreactant whose instability degrades operational stability. To address this, we built a dissolved-O₂-driven ECL platform based on MoC nanoclusters/Co single-atom sites co-anchored on N-doped porous carbon (MoC NCs/Co SAs). The MoC NCs in the heterostructure activate dissolved O₂ to generate reactive oxygen species (ROS), while the Co SAs oxidize luminol, thus separating the two half-reactions in time. XRD, XPS, and TEM characterizations confirmed the hierarchical porous architecture and the EPR analysis verified singlet oxygen (¹O₂) as the active ROS. The sensor achieved a wide linear range of 568.79 pM to 28.39 mM (R² = 0.999) with a detection limit of 505.3 pM. Spike-recovery tests in fruit juices showed recoveries of 97.94-102.12%, confirming reliability in complex food matrix. By replacing external H₂O₂ with a dual-site catalytic cascade, this design eliminated H₂O₂ instability effect, and showed the good balance between the sensitivity and dynamic range, providing a practical platform for AA monitoring in food quality control.