Chiral nanocrystals: plasmonic spectra and circular dichroism.

The life is inherently chiral. Consequently, chirality plays a pivotal role in biochemistry and the evolution of life itself. Optical manifestation of chirality of biomolecules, so-called circular dichroism, is a remarkable but relatively weak effect appearing typically in the UV. In contrast to the biomolecules, plasmonic nanocrystals offer an interesting opportunity to create strong circular dichroism (CD) in the visible spectral range. Here we describe plasmonic properties of single chiral nanocrystals and focus on a new mechanism of optical chirality originating from a chiral shape of a nanocrystal. After careful examination, we found that this CD mechanism is induced by the mixing between different plasmon harmonics and is qualitatively different from the previously described dipolar CD effect in chiral assemblies of spherical nanoparticles. Chiral plasmonic nanocrystals studied here offer a new approach for the creation of nanomaterials with strong chiroptical responses in the visible spectral interval.