A label-free amperometric immunosensor for detection of zearalenone based on trimetallic Au-core/AgPt-shell nanorattles and mesoporous carbon

• Au@AgPt nanorattles have special structure of Au-core and imperfect AgPt-shell.
• Au@AgPt are proposed for the first time applied in electrochemical immunosensor.
• Substrate materials MC/Au@AgPt possess excellent conductivity and high surface area.
• The proposed immunosensor exhibits a low detection limit of 1.7 pg mL−1.

A novel label-free amperometric immunosensor is proposed for the ultrasensitive detection of zearalenone (ZEN) based on mesoporous carbon (MC) and trimetallic nanorattles (core/shell particles with movable cores encapsulated in the shells). The nanorattles are composed of special Au-core and imperfect AgPt-shell structure (Au@AgPt). The Au@AgPt nanorattles are loaded onto the MC by physical adsorption. The structure of the Au@AgPt nanorattles was characterized by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Energy dispersive X-ray spectroscopy (EDS) confirmed the composition of the synthesized nanorattles. Compared with monometallic and bimetallic nanoparticles (NPs), Au@AgPt nanorattles show a higher electron transfer rate due to the synergistic effect of the Au, Ag and Pt NPs. MC further improves the sensitivity of the immunosensor because of its extraordinarily large specific surface area, suitable pore arrangement and outstanding conductivity. The large specific surface area of MC and MC@Au@AgPt were characterized by the BET method. ZEN antibodies are immobilized onto the nanorattles via Ag–NH2 bonds and Pt–NH2 bonds. Cyclic voltammetry and square wave voltammetry were used to characterize the recognizability of ZEN. Under optimum experimental conditions, the proposed immunosensor exhibited a low detection limit (1.7 pg mL−1), a wide linear range (from 0.005 to 15 ng mL−1) as well as good stability, reproducibility and selectivity. The sensor can be used in clinical analysis.

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