Enhanced electrochemiluminescence of Au–Ag bimetallic nanocluster@CNTs–TiO2 nanocomposite and its use in ultra-sensitive immunosensing for CEA

Abstract

Herein, highly efficient electrochemiluminescence (ECL) of novel Au–Ag bimetallic nanocluster @CNTs–TiO₂ nanocomposites (Au–Ag NCs@CNTs–TiO₂ NPs) with a unique “pearl necklace” structure was achieved. An ECL immunosensor was fabricated for simple, label-free and ultra-sensitive detection of cancer embryo antigen (CEA). The functionalized CNTs–TiO₂ was used as a light-emitting carrier of Au–Ag NCs, TiO₂ NPs were used as the co-reaction accelerator and dissolved O₂ as the intrinsic co-reactant for the in situ generation of the strong oxidizing intermediate radical OH˙. OH˙ significantly influenced the ECL properties of metal NCs. Carbon nanotubes (CNTs) acted as conductors, enabling faster electron transfer and more effective energy transmission in the Au–Ag NCs@CNTs–TiO₂ NP nanostructure. Compared with the ECL of pure Ag NCs, the ECL of Au–Ag NCs on the TiO₂ NP surface was significantly enhanced due to the synergistic effect of bimetallic NCs. The experimental results showed that Au–Ag NCs@CNTs–TiO₂ NPs achieved excellent ECL performance, and decreased the detection limit of the immunosensor for measuring CEA to 0.03 pg mL⁻¹ in the absence of any additional signal amplification assay. The proposed ECL immunosensor is expected to be promising for applications in diagnostics and bioanalysis using other biomolecules.