Helical Metal Nanoparticle Assemblies with Defects: Plasmonic Chirality and Circular Dichroism

Metal nanoparticle structures with a helical arrangement are able to create strong optical chirality and associated circular dichroism (CD). The CD effect in these chiral structures comes from the electromagnetic dipole–dipole interaction between nonchiral nanoparticles. In general, the calculated CD spectra are sensitive to the parameters. The shape of the CD spectrum depends on the helix pitch and radius and, sometimes, on the number of particles in a helix. Simulating several geometries, we were able to identify the sets of parameters for which the CD spectrum is very stable against defects or disorder. These results are important for designing novel nanocomposite materials with strong optical chirality in the visible wavelength region.