posted on 2021-08-10, 18:42authored byHebing Hu, Sribharani Sekar, Wenbing Wu, Yann Battie, Vincent Lemaire, Oriol Arteaga, Lisa V. Poulikakos, David J. Norris, Harald Giessen, Gero Decher, Matthias Pauly
Chirality
is found at all length scales in nature, and chiral metasurfaces
have recently attracted attention due to their exceptional optical
properties and their potential applications. Most of these metasurfaces
are fabricated by top-down methods or bottom-up approaches that cannot
be tuned in terms of structure and composition. By combining grazing
incidence spraying of plasmonic nanowires and nanorods and Layer-by-Layer
assembly, we show that nonchiral 1D nano-objects can be assembled
into scalable chiral Bouligand nanostructures whose mesoscale anisotropy
is controlled with simple macroscopic tools. Such multilayer helical
assemblies of linearly oriented nanowires and nanorods display very
high circular dichroism up to 13 000 mdeg and giant dissymmetry
factors up to g ≈ 0.30 over the entire visible
and near-infrared range. The chiroptical properties of the chiral
multilayer stack are successfully modeled using a transfer matrix
formalism based on the experimentally determined properties of each
individual layer. The proposed approach can be extended to much more
elaborate architectures and gives access to template-free and enantiomerically
pure nanocomposites whose structure can be finely tuned through simple
design principles.