Controlling Interparticle Gaps in Self-Organizing Gold Nanostructures on Templates Made by a Modified Hard Anodization Technique

Abstract

In this article, we demonstrate how the formation of large-area self-organizing gold nanostructures formed on porous alumina templates can be grown with interparticle gaps that can be tuned both by appropriate choice of anodization technique and by the amount of deposited gold. The gold nanostructures reported in this work are formed by sputter-coating the porous alumina templates made with a hard anodization technique in oxalic acid, and the interparticle gap size is reproducibly controlled simply by adjusting the amount of sputter-coated gold. To make a change from mild and into hard anodization regimes in oxalic acid, several stages are used in the anodization procedure, including the use of a protective porous oxide layer initially created under mild anodization conditions. This simple stepwise anodization technique, which only uses electrolyte cooling, can facilitate burn-free anodization at even higher voltages during hard anodization processing in oxalic acid. The formation of the gold nanostructures is studied with scanning electron microscopy, and the influence of the morphology on the optical properties of the nanostructures is investigated by optical reflectance spectroscopy. Tunability of the localized surface plasmon resonances is demonstrated, and it can be optimized and exploited with a special view to surface enhanced molecular sensing techniques.