Confined ZrO₂ possessing triple catalytic functionality boosts luminol-dissolved oxygen electrochemiluminescence for immunoassay

Developing high-performance electrochemiluminescence (ECL) is of great importance for trace cytokine analysis. Herein, zirconium dioxide (ZrO₂) encapsulated within the silica nanochannel films (SNF) were first employed to amplify the ECL response of the luminol-dissolved oxygen (DO) system. ZrO₂ nanoparticles were in-situ synthesized and confined within the SNF channels via a one-step electrodeposition strategy. Benefiting from its unique triple catalytic functionality, SNF-confined ZrO₂ acts as an efficient co-reactant accelerator, resulting in markedly enhanced ECL performance. During the initial cathodic scan, the confined ZrO₂ promotes the oxygen reduction reaction (ORR), generating superoxide anion radicals (O₂^•-) and H₂O₂. In the subsequent anodic scan, the confined ZrO₂ not only catalyzes the conversion of in-situ generated H₂O₂ into O₂^•-, but also facilitates the conversion of luminol anion (LH^-) to its radical anion (L^•-). These synergistic processes ensure efficient generation of abundant O₂^•- and L^•-, ultimately boosting the ECL emission. Furthermore, an ECL immunosensor was fabricated for interleukin-6 (IL-6) detection through the oriented immobilization of antibodies on the external surface of SNF. The constructed immunosensor displays a wide linear range (1 fg mL^-1 to 10 ng mL^-1) and a low detection limit of 0.24 fg mL^-1. This work demonstrates that SNF-confined ZrO₂ holds promise as a versatile co-reactant accelerator for the construction of highly efficient ECL systems.