Enhanced Circular Dichroism in 3D Helical-Shaped Chiral Plasmonic Metamaterials Assembled from Colloidal Nanocrystals

We report 3D helical-shaped plasmonic metamaterials assembled from colloidal Au nanocrystal/bulk Au bilayer heterostructures. Arrays of planar spiral patterns defined by nanoimprint lithography are transformed into 3D helical metamaterials through strain-driven, out-of-plane folding induced by ligand exchange and annealing.

Compared with multiple-short-arm (4C) references having the same total arm length, single-helical (1H) structures exhibit stronger differential transmittance between left- and right-handed circularly polarized light (Δ<i>T</i>). Adding a second helical arm to form double-helical (2H) structures further increases Δ<i>T</i> to nearly 70% in the mid-infrared range. Electromagnetic simulations reveal that intra-meta-atom coupling, antenna loading, and mode hybridization reshape the resonances and amplify CD beyond the response of isolated components.