DNA sensing using nanocrystalline surface-enhanced Al₂O ₃ nanopore sensors

A new solid-state, Al₂O₃ nanopore sensor with enhanced surface properties for the real-time detection and analysis of individual DNA molecules is reported. Nanopore formation using electron-beam-based decomposition transforms the local nanostructure and morphology of the pore from an amorphous, stoichiometric structure (O to Al ratio of 1.5) to a heterophase crystalline network, deficient in O (O to Al ratio of ≈0.6). Direct metallization of the pore region is observed during irradiation, thereby permitting the potential fabrication of nanoscale metallic contacts in the pore region with application to nanopore-based DNA sequencing. Dose-dependent phase transformations to purely γ and/or α-phase nanocrystallites are also observed during pore formation, allowing for surface-charge engineering at the nanopore/fiuid interface. DNA transport studies reveal an order-ofmagnitude reduction in translocation velocities relative to alternate solid-state architectures, accredited to high surface-charge density and the nucleation of charged nanocrystalline domains. The unique surface properties Of Al₂O₃ nanopore sensors make them ideal for the detection and analysis of singlestranded DNA, double-stranded DNA, RNA secondary structures, and small proteins. These nanoscale sensors may also serve as useful tools in studying the mechanisms driving biological processes including DNA-protein interactions and enzyme activity at the single-molecule level.