Preparation of ordered array of nanoscopic gold rods by template method and its optical properties

Porous aluminum oxide membranes with pore diameters smaller than 20 nm were prepared by anodization of aluminum. Using these porous membranes as a template, we fabricated uniform gold cylinder arrays by electrodeposition of gold into the pores. All cylinders in the array were parallel, with their long axes perpendicular to the surface of the template. Electron microscopy, including transmission electron microscopy (TEM) and scanning electron microscopy (SEM), were employed to characterize the morphology of the templates and the fabricated nanometer scale of cylinder arrays. The extinction spectra of the arrays along the longer axes showed that the extinction maximal (λmax) shifted to a short wavelength and strengthened when the aspect ratio (l/d) of the cylinders increased. The dependence of the maximal (λmax) on the size was explained qualitatively by using the approximate dynamical Maxwell–Garnett model, and the calculated results were compared with the experimental ones.