Nanotip fabrication by Anodic Aluminum Oxide templating

We demonstrate a novel approach to fabricate a gold nanotip array using an Anodic Aluminum Oxide (AAO) template prepared by anodizing the aluminum in two acids with increasing anodization voltage, which results in the nanopore diameter being increased along the AAO channels. The thick barrier layer formed at the bottom of the AAO template can be removed without affecting the apex diameter by forming a thick apex region in the initial stage. Finally, gold is electrodeposited into the template and a gold nanotip array with apex and base diameter of 21 nm and 210 nm, respectively can be achieved. The structure of the nanotip array can be varied by manipulating the dimensions of the AAO channels by controlling the applied voltage together with the anodization time. Using this method, the material choice of nanotip array can be varied easily.