Formation of amine groups on the surface of GaN: A method for direct biofunctionalization

Gallium nitride has attracted significant interest as a material for biosensors; however, techniques for biofunctionalizing GaN surfaces have received limited attention. Here, we present a method for producing amine groups directly on GaN surfaces through exposure to a glow discharge plasma fed with humidified air, thereby eliminating the need for complex organic functionalization chemistry. Amine formation is tracked via X-ray photoelectron spectroscopy (XPS) by labeling the plasma-formed surface groups with a fluorinated probe that binds specifically to primary amines. These amine groups can subsequently couple covalently to a wide range of biomolecules. The covalent immobilization of a NeutrAvidin layer is demonstrated using Fourier transform infrared spectroscopy (FT-IR) and fluorescent biotin-binding assays. Finally, we show that plasma exposure times sufficient for the formation of amine groups do not significantly alter the conductivity of the GaN substrate.