A "signal-off" electrochemiluminescence immunosensor based on electron transfer between core-shell emitter Ag@SiO2 and quencher CeO2

Silver nanoparticles (Ag·NPs) show promising advantages in electrochemiluminescence (ECL) owing to their favorable optical properties and biocompatibility. However, their susceptibility to oxidation and degradation in the presence of air adversely affects ECL intensity. In this study, we employed a sandwich sensing platform using silica-coated silver nanoparticles (Ag@SiO2) as a novel luminescent material and cerium dioxide (CeO2) as an ECL signal quencher for sensitive neuro-specific enolase (NSE) detection. The core-shell structure protected Ag NPs within the silica (SiO2) layer, enhancing their ECL luminescence properties by reducing external environmental influence and preventing Ag NPs aggregation. Amino-functionalized CeO2 efficiently diminished Ag@SiO2 ECL emission through electron transfer, resulting in a "signal-off" detection mode with high sensitivity and accuracy. The detection limit reached 1.66 fg/mL, and the detection range spanned from 100 fg/mL to 500 ng/mL, showcasing a powerful biomolecule detection strategy.