▎ 摘　　要

Herein, we develop an electrochemical immunosensor based on a zirconia-reduced graphene oxide-1-ethyl-3methylimidazolium tetrafluoroborate (EMIM.BF4) ionic liquid (ZrO2-rGO-IL) nanocomposite for the detection of a carcinoembryonic antigen (CEA) breast cancer biomarker. The characterization results of the synthesized ZrO2-rGO-IL nanocomposite show that it has high electroconductivity, oxygen functionalities, and a larger active surface area, which favors high loading of antiCEA antibodies. The fabricated BSA/anti-CEA/ZrO2-rGO-IL/ GCE immunosensor can detect CEA with high sensitivity and selectivity in a broad detection range between 25.0 fg mL-1 and 25.0 ng mL-1 with an ultralow limit of detection (LOD) of 1.23 fg mL-1 through differential pulse voltammetry (DPV). In addition, we tested the CEA in serum samples having linear detection ranges from 100.0 fg mL-1 to 5.0 ng mL-1 with an LOD of 2.25 fg mL-1. Subsequently, the incubation time and selectivity of the immunosensor show a great affinity for CEA. Therefore, the proposed immunosensor can be a promising candidate for CEA detection in clinical specimens. Prospectively, the synthesized nanocomposite will have the for the effective detection of other cancer biomarkers.