High-Density Quintuple Single-Atom Promoters for Enhanced Dual-Polarity Electrochemiluminescence via Efficient Oxygen Activation.

Electrochemiluminescence (ECL) is a light emission process mediated by electrochemically produced radical intermediates, yet conventional luminol-based systems are limited by sluggish oxygen activation, causing unbalanced anodic and cathodic reactions and inefficient luminescence. In this study, we report a cascade anchoring strategy for scalable synthesis of a high-density quintuple-metal single-atom catalyst (HDQ-SAC) as an ECL promoter, featuring atomically dispersed Co, Fe, Mn, Ni, and Cu stabilized by nitrogen coordination (13.79 wt% total metal loading). Comprehensive x-ray absorption near-edge structure, extended x-ray absorption fine structure, and annular dark-field scanning transmission electron microscope analyses, along with spin-polarized density functional theory simulations, identify the delocalized network of electron transfer in HDQ-SACs through the tailored electronegativity gradient and intermetallic synergy. This unique electronic structure of HDQ-SACs collectively optimizes the adsorption energies of O2 and key reaction intermediates and facilitates reactive oxygen species generation across both anodic and cathodic pathways, thereby achieving dual-polarity ECL enhancement in the luminol-O2 ECL system. This multi-atomic HDQ-SAC promoter with cooperative oxygen activation significantly mitigates the intrinsic anodic/cathodic intensity asymmetry and establishes a mechanistic paradigm for ECL enhancement, providing a versatile framework for ultrasensitive biomarker detection.