Single-particle insights into the optical activity of planar-layered chiral plasmonic superstructures

Planar assemblies of plasmonic nanoparticles have provided opportunities in various fields. This study exploits the self-assembly of gold nanorods (AuNRs) into planar, layered chiral superstructures (dodecamer) using DNA origami technology. Due to the collective plasmonic coupling modes, the dodecamers exhibit <em>g</em>-factors of up to +0.06, which is 4-5 times higher than those of the dextrodimers. The chiroptical property of the superstructures proved to be strongly size-dependent, exhibiting enhanced <em>g</em>-factors with increasing the size of AuNRs. Moreover, by excluding the averaging and close-to-racemic effects in the ensemble colloids, circular differential scattering (CDS) and circularly polarized luminescence (CPL) were studied at the single-particle level, revealing the essential role of the structural chirality of superstructure in correlating single-particle scattering with nearby dye emission. The observed correlated CDS and CPL show <em>g</em>-factors up to -0.17 and -0.6, respectively. These results highlight the potential of DNA origami-directed plasmonic assemblies for nanoscale chirality engineering, with applications in biosensing, chiral photonics, and metamaterials.