RESUMEN
ZnO nanosheets are polycrystalline nanostructures that are used in devices including solar cells and gas sensors. However, for efficient and reproducible device operation and contact behaviour the conductivity characteristics must be controlled and surface contaminants removed. Here we use low doses of argon bombardment to remove surface contamination and make reproducible lower resistance contacts. Higher doses strip the surface of the nanosheets altering the contact type from near-ohmic to rectifying by removing the donor-type defects, which photoluminescence shows to be concentrated in the near-surface. Controlled doses of argon treatments allow nanosheets to be customised for device formation.
RESUMEN
Affinity biosensors based on graphene field-effect transistor (GFET) or resistor designs require the utilization of graphene's exceptional electrical properties. Therefore, it is critical when designing these sensors, that the electrical properties of graphene are maintained throughout the functionalization process. To that end, non-covalent functionalization may be preferred over covalent modification. Drop-cast 1,5-diaminonaphthalene (DAN) was investigated as a quick and simple method for the non-covalent amine functionalization of carbon-based surfaces such as graphene, for use in biosensor development. In this work, multiple graphene surfaces were functionalized with DAN via a drop-cast method, leading to amine moieties, available for subsequent attachment to receptor molecules. Successful modification of graphene with DAN via a drop-cast method was confirmed using X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and real-time resistance measurements. Successful attachment of receptor molecules also confirmed using the aforementioned techniques. Furthermore, an investigation into the effect of sequential wash steps which are required in biosensor manufacture, on the presence of the DAN layer, confirmed that the functional layer was not removed, even after multiple solvent exposures. Drop-cast DAN is thus, a viable fast and robust method for the amine functionalization of graphene surfaces for use in biosensor development.