Quenched electrochemiluminescence of Ag nanoparticles functionalized g-C3N4 by ferrocene for highly sensitive immunosensing

• ECL behavior of Ag@g-C3N4 was investigated.
• Ferrocene for quenching Ag@g-C3N4 emission was investigated.
• The linearly range of the immunosensor for CEA was 1 pg mL−1–100 ng mL−1.

In this paper, a novel sandwich electrochemiluminescence (ECL) immunosensor was constructed by ferrocene for quenching Ag nanoparticles functionalized g-C3N4 (Ag@g-C3N4) emission. The prepared Ag@g-C3N4 had strong and stable ECL signals compared to pure g-C3N4 and primary antibody (Ab1) can be immobilized on Ag@g-C3N4 by adsorption of Ag nanoparticles. Ferrocene carboxylic acid (Fc-COOH) labeled secondary antibody was immobilized on Au doped mesoporous Al2O3 nanorods (Au@Al2O3–Fc-COOH@Ab2) as labels through adsorption ability of Au toward proteins. After a sandwich-type immunoreaction, a remarkable decrease of ECL signal was observed due to the ECL quenching of Ag@g-C3N4 by Au@Al2O3–Fc-COOH@Ab2. As a result, the change of ECL intensity has a direct relationship with the logarithm of CEA concentrations in the range of 1 pg mL−1–100 ng mL−1 with a detection limit of 0.35 pg mL−1 (S/N = 3). Additionally, the proposed immunosensor shows high specificity, good reproducibility, and long-term stability.

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