Enhancing antibody capture with edge-carboxyl-enriched, low-defect monolayer graphene oxide via controlled graphite oxidation

Herein, a controlled oxidation method for producing large-scale graphene oxide (GO) with enhanced carboxyl-edge functionality and controlled oxygen-containing groups on the basal plane is reported using commercially available, low-cost graphite flakes. The synthesized carboxyl-rich GO flake was confirmed to be a monolayer, with a thickness of approximately 1.1 nm, indicating successful exfoliation into a 2D form. Hydriodic acid (HI) vapor was used for reduction, which largely restores the sp² graphitic structure in the basal plane while preserving the edge carboxyl groups. The average flake size of the synthesized GO was around 1 μm, suitable for providing a high density of carboxyl-edge functionalities in the resulting reduced graphene oxide (rGO) films with a thickness of 6–10 nm. Due to the enhanced carboxyl-edge functionality, the presence of carboxyl-edge-related defects, and uniform flake size distribution, antibodies were effectively immobilized on the rGO sensing layer through covalent bonding by activating the carboxyl groups, resulting in excellent antibody density and high resistance changes with outstanding uniformity in the electrical sensing devices. These results pave the way for the development of low-cost, rGO-based electrical sensors utilizing this tailor-made carboxyl-rich graphene oxide for the detection of various biomarkers in disease monitoring.