Chiral Nanoporous Structures Fabricated via Plasmon-Induced Dealloying of Au-Ag Alloy Thin Films

Abstract

Chiral plasmonic nanostructures are of significant interest because of their strong chirality compared to typical chiral molecules and their potential for various applications such as enantioselective sensors and metamaterials. Although chemical or photochemical fabrication methods for chiral nanostructures have attracted attention because of their cost-effectiveness and large-area applicability, most of the chemically synthesized chiral nanostructures are two-dimensional ensembles or arrays of individual chiral nanoparticles. In the present study, more three-dimensional, densely interconnected chiral plasmonic nanoporous structures are fabricated via plasmon-induced dealloying of Au-Ag alloy under circularly polarized light (CPL). CPL is used as a sole chiral source and irradiated to a chemically treated Au-Ag alloy film showing absorption due to localized surface plasmon resonance (LSPR). The resulting nanoporous structures exhibit chiroptical responses depending on the handedness CPL illuminated. The mechanism of chirality introduction is discussed on the basis of an electromagnetic simulation.