Micelle-Confined Co–N Coordination Enables Size-Tailored Nanoemitters for High-Performance ECL Biosensing

Electrochemiluminescence (ECL) is particularly suited for ultrasensitive biomarker detection due to its low background signal and tunable electrochemical control. Herein, we report a micelle-confined coordination engineering strategy for the construction of size-tailored Co-N nanoemitters with an enhanced ECL performance. By precisely tuning the hydrophobic chain lengths of quaternary ammonium surfactants (C12-C16), benzimidazole (BIM)-dominated micelles with tailored dimensions (9-23 nm) are formed as nanoconfined coordination templates. Among them, CoBIM/TTAB (∼10-20 nm) exhibits optimal spatial confinement for the activation of integrated Co-N catalytic and luminogenic centers, thereby promoting the efficient redox-induced generation of reactive oxygen species and excitons. This spatially coupled architecture substantially improves the mass and electron transfer dynamics, resulting in significantly amplified ECL emission. Leveraging the cationic surface of CoBIM/TTAB, a "signal-on" biosensor is further developed via electrostatic DNA assembly, enabling highly selective detection of N-terminal pro-B-type natriuretic peptide (NT-proBNP) with a broad dynamic range (0.1 pg mL^-1 to 10 ng mL^-1) and a low detection limit of 0.03 pg mL^-1. This platform holds significant promise for the early diagnosis of heart failure and may inspire the rational construction of next-generation electroactive nanomaterials.