Low-Potential Electrochemiluminescence Imaging Mediated by Oxygen Vacancy for Sensitive Analysis of Diazinon

With the prevalence of electrochemiluminescence (ECL) in bioanalysis and clinical diagnostics, the development of efficient low-potential ECL systems has emerged as a research focus. Herein, a novel coreactant acceleration approach was reported based on FeNi layered double hydroxide enriched with oxygen vacancies (FeNi-LDH-<i>V</i>_O). The system produced notably strong ECL signals at -0.8 V when integrated with a Zr-porphyrin metal-organic framework (Zr-MOF). Mechanistic investigations revealed that the <i>V</i>_O in the FeNi-LDH provided abundant active sites that facilitated peroxydisulfate (S₂O₈^2-) adsorption and activation, which triggers the generation of highly reactive sulfate (SO₄^•-) and hydroxyl (^•OH) radicals. Efficient radical production played a key role in enhancing ECL output. Based on this mechanism, an ECL imaging biosensor was designed for visually detecting diazinon (DZN). In the presence of Mg²⁺, the DNAzyme catalyzed the site-specific cleavage of the ferrocene (Fc)-labeled strand, resulting in the release of Fc quenchers from the electrode surface and an ECL signal that is enhanced in a concentration-dependent manner. The biosensor exhibited a wide linear range (0.1 to 5.0 × 10³ nM), a low detection limit (7.6 pM), and excellent specificity and repeatability, showing potential for food marker detection.