Fabrication and characterization of DNA-functionalized GaN nanowires

Both planar GaN substrates and individual GaN nanowires have been functionalized with single-stranded DNA, an important process for use of GaN devices for label-free biosensing. A functional aminopropyltrimethoxysilane layer was deposited on hydroxylated GaN, as confirmed by XPS. A bifunctional glutaraldehyde layer was then coupled to the silane, presenting carbonyl groups for subsequent condensation reaction with amine-terminated, fluorescently labeled DNA. Atomic force and scanning electron microscopy studies indicated the functional layers are smooth, uniformly deposited, and at least 20 nm thick on both the planar surfaces and on individual nanowires. An oxygen plasma treatment was used in conjunction with a silicone mask to pattern the functionalized surfaces and nanowires. DNA remained immobilized on the nanowires following their release into suspension via sonication and dielectrophoretic alignment, demonstrating the potential of this functionalization chemistry for 'bottom-up' fabrication and self-assembly of nanowire sensor arrays.