Several carbon materials have been extensively applied in the construction of biosensors as nanomaterials 148 or even standalone electrodes 149 . Among them, graphene and its derivatives are arguably one of the most popular nanostructures. Graphene is a single layer of carbon atoms organised in a sp 2 hybridised honeycomb lattice. Graphene oxide (GO) is often used instead to overcome obstacles presented by graphene, i.e. the poor production yield, requirement of surface support, and uncontrollable thickness. GO is rich in oxygen containing functional groups such as hydroxyl, epoxide, carbonyl, and carboxyl groups, which can facilitate antibody immobilisation.