Figure 1.

Schematic illustration of the conversion of (A) GO into (B) carboxyl-GO sheets via a facile one-step chloroacetic acid modification route at low temperature. (C) Carboxylic acid-terminated groups were formed and then activated with EDC/NHS to form an NHS ester-terminated group at the carboxyl-GO surface. (D) The attachment of peptides via amine coupling, and the deactivation of the unreacted surface sites with ethanolamine (EA) blocking. (E) Immobilization of the peptide on the carboxyl-GO-based SPR chip using non-immunological to detect hCG protein. (F) Schematic instrumental set-up of the Kretschmann configuration, the carboxyl-GO-peptide film was immobilized on the chip and injected into the hCG protein interaction of the SPR flow cell. The flow rate was 30 µL/minute, and the running buffer was phosphate-buffered saline (PBS) solution.

Abbreviations: GO, graphene oxide; hCG, human chorionic gonadotropin; SPR, surface plasmon resonance.