Fabrication of High-Aspect-Ratio Alumina–Nickel Coaxial Nanorod Array by Electrodeposition

In this paper, we investigate the fabrication of high-aspect-ratio (~500) larger area alumina-metal coaxial nanorod arrays using electrodeposition with an anodic aluminum oxide template. An annealing process was implemented after electrodeposition to enhance the mechanical properties of the deposited metal nanorods. Phosphoric acid was then used to gradually etch off the alumina that enclosed each individual metal nanorod starting from the borders between the hexagonal cells. The transmission electron microscopy and selected area electron diffraction analyses were implemented to verify the alumina/nickel coaxial structure. The alumina shell wrapping each individual metal nanorod served as an insulator for the core metal. The high aspect ratio of the alumina-metal coaxial nanorods described herein makes them practicable for use as nanoprobes or electrodes that are capable of penetrating individual cell membranes to sense the biological functions of the cells.