▎ 摘　　要

Here we report a one-step approach to synthesize graphene oxide-thionine-Au (GO-Thi-Au) nanocomposites using the synergistic effect of Thi and GO. Thi molecules adsorbed on the nanocomposites still kept the property of electroactive redox. Meanwhile, the resulting Au nanoparticles (AuNPs) of the nanocomposites offer active sites for the immobilization of biomolecules. The GO-Thi-Au nanocomposites are successfully employed for the fabrication of a simple, label-free, and ultrasensitive electro-chemical immunosensor. Using carcinoembryonic antibody (anti-CEA) and carcinoembryonic antigen as model systems, the immunosensor showed an ultralow detection limit of 0.05 fg mL(-1), and a linear calibration plot was obtained in a wide concentration range from 0.1 fg mL(-1) to 1 x 10(9) fg mL(-1). (C) 2013 Elsevier B.V. All rights reserved.