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.