A novel lable-free electrochemical immunosensor for carcinoembryonic antigen based on gold nanoparticles-thionine-reduced graphene oxide nanocomposite film modified glassy carbon electrode

► Gold nanoparticles-thionine-reduced graphene oxide (GNP-THi-GR) nanocomposites synthesized using THi molecules as interlinkers. ► GR has unique electrical conductivity, enlarged active surface area. ► THi has excellent redox activity. ► GNPs has large specific surface area, excellent biocompatibility, extraordinarily catalytic activity, good conductivity. ► The nanocomposites combined with the advantages of the three species suitable for a label-free immunosensor.