Ionic liquid functionalized graphene/Au nanocomposites and its application for electrochemical immunosensor.

In this work, a new nanocomposite, which was composed of ionic liquid functionalized graphene sheet (IL-GS) loaded gold nanoparticles (AuNPs), was prepared. The IL-GS was directly synthesized by the electrochemical exfoliation of graphite in ionic liquid (IL). Due to the modification of the IL, IL-GS can not only be dispersed easily in aqueous solution to form a homogeneous colloidal suspension of individual sheet, but also exhibits an improved conductivity. Meanwhile, the loaded AuNPs on the nanocomposites can increase the specific surface area to capture a large amount of antibodies as well as improve the capability of electron transfer. The IL-GS-Au nanocomposites were successfully employed for the fabrication of a facile and sensitive electrochemical immunosensor. Carcinoembryonic antigen (CEA) was used as a model protein. The proposed immunosensor exhibits a wide linear detection range (LDR) from 1 fg mL⁻¹ to 100 ng mL⁻¹, and an ultralow limit of detection (LOD) of 0.1 fg mL⁻¹ (S/N=3). In addition, for the detection of clinical serum samples, it is well consistent with the data determined by the developed immunoassay and ELISA, indicating that the immunosensor provides a possible application for the detection of CEA in clinical diagnostics.