Gradient Optical Response of Au Ellipse Nanopillar Array via Anisotropic Pillar Heights: A Highly Tunable Plasmonic Material toward Biosensing Applications

An ordered multispectral array of Au coated ellipse nanopillars was successfully fabricated via laser interference and nanoimprint lithography. The fabricated plasmonic substrate features a gradient plasmonic response in both translational and rotational directions across the chip, relative to a polarized UV−vis light source. Structural characterization of the substrate suggests that the gradient response is induced by the anisotropic valleys connecting the ellipse nanopillars in a hexagonal arrangement, resulting in varying nanopillar relative heights in various cross sections of the array. These gradual geometrical changes in the nanostructure allow control of the plasmonic response through two degrees of freedom (e.g., spatial translation or source polarization) on a single nanoimprinted chip. We also show that the fabricated substrate is viable for biosensing applications.