Chiral plasmonic superlattices from template-assisted assembly of achiral nanoparticles

The creation of chiral plasmonic architectures combining templates with achiral plasmonic particles leads to strong chiroptical responses that can be finely tuned via the characteristics of the colloidal building blocks. Here we show how elastomeric molds, pre-patterned with a hexagonal array of triskelia motifs, can guide the assembly of ordinary noble metal colloids into chiral plasmonic architectures with strong dichroism values. Under normal incidence, the chiral arrays made with gold and silver colloids showed g-factors of 0.18 and 0.4, respectively. In all cases, increasing the size of the colloid allows tuning the optical properties of the structure in the VIS-NIR range. When a superstrate layer is deposited onto the structures, the extrinsic chirality response of the 2D superlattice is revealed and strongly amplified by the chiral motifs under oblique inspection, leading to g-factors of ± 1.2 at ± 14°. Finally, these chiral plasmonic resonances sustained by the triskelion array are used to produce circularly polarized photoluminescence from achiral organic dyes placed on top with up to 20% of dissymmetry.