Theory of chiral plasmonic nanostructures comprising metal nanocrystals and chiral molecular media.

Plasmonic nanocrystals strongly interact with chiral molecular shells through electric and magnetic fields and in this way acquire new chiro-optical properties. Transfer of chirality from biomolecules to the plasmonic resonances is a collective phenomenon and strongly depends on the geometry of nanostructure. Collective effects in a molecular chiral shell may suppress or enhance plasmonic circular dichroism (CD) depending on the geometry of hybrid nanocrystal. In large chiral plasmonic structures, we identify a new electrodynamic mechanism of plasmonic CD that is qualitatively different to the near-field, dipolar mechanism of the plasmonic chirality described by us previously. Our models also show that anisotropic nanocrystals, such as nanorods or oriented molecular shells, have strongly enhanced CD at the plasmonic frequency. A family of chiral plasmonic nanostructures proposed and modeled here can be used for designing new optical media and chiral sensors.