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.

Experimental study on polarized surface enhanced resonance Raman scattering of rhodamine 6G adsorbed on porous Al2O3 substrates

“…Large-area self-organizing hexagonally ordered Au nanostructures can be fabricated by sputter-coating the embossed Al template after removing the porous oxide layer created by hard anodization (HA) in oxalic acid. 1,18 The hexagonally ordered porous Al 2 O 3 used in the present study was prepared using annealed (500 • C) and electropolished high purity (99.999%) Al foils. The 7.5 min of pre-anodization at 40 V in 0.30 M oxalic acid (step 1, Figure 1) was carried out in order to form a protective oxide layer (200-400 nm) on the Al surface.…”

Porous Aluminum Oxide Formed by Anodizing in Various Electrolyte Species

“…The hard anodizing allows the fabrication of a self-ordered porous oxide with various cell diameters under high voltage conditions: sulfuric acid at 27-80 V to 72-145 nm [104], oxalic acid at 120-150 V to 220-300 nm [105], and phosphoric acid at 195 V to 320-380 nm [106]. In addition, several research groups have reported using the advanced hard anodizing technique to further extend the self-ordering voltage and the corresponding cell diameters [107][108][109][110][111]. Noh et al have reported the fabrication of highly ordered nanotubular aluminum oxide by hard anodizing [112].…”

Morphology Dependence on Surface-Enhanced Raman Scattering Using Gold Nanorod Arrays Consisting of Agglomerated Nanoparticles

“…2f) [21]. This phenomenon is present between pores and is related to the finite wall thickness [22]. The top and oblique view SEM observations (Fig.…”