Nanoporous gold–alumina core–shell films with tunable optical properties

Abstract

Tuning of the localized surface plasmon resonance (LSPR) of nanoporous metals is at theheart of manipulating light within extremely small volumes for the implementation ofoptical devices at the nanoscale. In this work, nanoporous gold–alumina core–shellfilms with fixed gold skeletons and different thicknesses of alumina shells arefabricated using chemical corrosion and subsequent atomic layer deposition. Opticaltransmission of the nanoporous composite films can be tailored through LSPRexcitations of the three-dimensional gold skeleton and the alterable alumina shells asthe covering dielectric. A 92 nanometer red-shift of the LSPR band is attainedvia its dielectric medium dependence and the comparable decay length withpore size. The widely tunable optical transmission and significantly improvedstability thus suggest incorporating nanoporous gold–alumina into promisingnano-devices with reliable performance. Low temperature surface decoration (<100 °C) provides a universal route to tune the optical properties while retaining the spatialgeometry of the metallic nanostructures.