UV/Ozone-Assisted Covalent Bioconjugation on Graphene Tapes

Compared to pristine graphene, graphene oxide (GO) has intriguing advantages for biological applications, such as high compatibility and much improved solubility in an aqueous environment. In particular, the oxygen-containing functional groups on GO enable the highly stable covalent conjugation of biomolecules, which promotes its application for developing versatile functional devices. In this work, we explored an ultraviolet/ozone (UV/O₃) treatment strategy to activate graphene-tape substrates (prepared by drop-casting graphene nanoplatelets on double-sided conductive carbon tapes) to achieve excellent bioconjugation capabilities. Our Fourier transform infrared spectroscopy (FTIR), wetting, and X-ray photoelectron spectroscopy (XPS) measurements confirmed the generation of high-density oxygen-containing functional groups on graphene-carbon tape, while the conductivity and electrochemical activity are merely influenced. Upon immobilizing amino-ferrocene (Fc-NH₂) onto the UV/O₃-activated graphene tape via carbodiimide cross-linking, a strong pair of redox peaks (corresponding to an Fc surface density over 8.0 × 10^-9 mol/cm²) was observed, indicative of its "elevated" covalent conjugation capability. More remarkably, highly efficient conjugation of glucose oxidase on UV/O₃-treated graphene tape was achieved, which demonstrated excellent catalytic activity, as confirmed by chronoamperometry. These results augment the great potential of UV/O₃-activated graphene tape substrates for convenient fabrication of electroactive biofunctional devices with high performance.