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Synthesis and Characterization of (3-Aminopropyl)Triethoxysilane-Modified Epitaxial Graphene

Electrochemical immunosensor devices comprise of an antibody immobilised onto a semiconducting or conducting substrate. The use of epitaxial graphene in immunosensors allows for the detection of an antigen specifically bound to the immobilised antibody by monitoring the current modulation of lithographically fabricated graphene channel devices. Multilayer epitaxial graphene (MEG) was produced on semi-insulating 4H-SiC(0001) substrates by annealing at 1700°C at 1x 10-5 mbar using a graphite cap. Thickness and morphology of the graphene was studied using Raman spectroscopy, XPS, AFM, and SEM. Selective areas of graphene were targeted for modification by adding a protective window of PMMA. In order to immobilise the antibody to the graphene substrate, an amine-terminated surface is required. (3-aminopropyl) triethoxysilane (APTES), is used to achieve amine termination, which is itself bound to a hydroxyliated graphene surface. Hydroxylation was achieved using Fenton chemistry and changes in surface hydrophobicity are confirmed using contact angle measurements. Attachment of APTES to the hydroxyl terminated graphene channel was confirmed using cyclic voltammetry (CV), XPS, and Raman spectroscopy. This functionalization method can be used to attach any antibody to the graphene substrate that can bind to an amine group. This platform is therefore easily adaptable for the fabrication of a range of immunosensor devices for the detection of different biomarkers.