A green method to produce nanoporous aluminum oxide templates and the direct application in the synthesis of nanowires

Abstract

As technology improves and the desire increases to produce smaller devices and manipulate smaller objects, the ability to synthesize nanoscopic materials reliably and reproducibly becomes increasingly important. Nanowires are likely to be used in these devices in the future, but production of these nanowires remains challenging. Currently, anodized aluminum oxide templates can be used to produce large amounts of high aspect ratio nanowires, but producing these templates in an environmentally-friendly manner has proved to be a challenge. In this research, the production of anodized aluminum oxide templates was sought to be improved for both ease of production and environmental friendliness. Using a DES for electropolishing, phosphoric acid for dissolution, as well as more concentrated oxalic acid for anodization, anodic aluminum oxide templates were synthesized in a simple, more environmentally-friendly way. These templates exhibit good ordering of 70 nm (with a standard deviation of 5 nm), diameter pores with 31% porosity, and were able to produce nickel nanowires using AC, pulse, and DC deposition (of diameters of 71 nm, 66 nm, and 65 nm, respectively) without any other metals deposited in the pores due to the barrier layer thinning and cathodic barrier removal steps used in the production. Most notably, the simple apparatus uses only a beaker with suspended electrodes, leading to a repeatable, inexpensive, and green route to producing immediately usable nanoporous anodized aluminum oxide templates.