Circular Dichroism of Gold Bipyramid Dimers

Chiral nanomaterials attract broad attention, as they offer new possibilities of modulation of optical properties and dissymmetry factors outperforming organic materials. Among various nanoparticles, plasmonic bipyramids present numerous advantages as building blocks of chiral nanomaterials (well-defined modulation of optical properties with the morphology of nanoparticles, narrow optical resonances, and high size and shape uniformity of synthesized particles). We study different possible orientations of gold bipyramids with respect to each other in dimers obtained by wet chemistry methods. For circularly polarized incident light we evaluate linear optical cross sections and plasmonic local field enhancement using COMSOL Multiphysics. We observe coupling of the nanoparticles' local fields and thus changes in extinction spectra, which modulate chiroptical properties of dimers. To assess the chirality of various arrangements, we note differences in cross sections for left- and right-handed polarized light which we further evaluate as the dissymmetry g-factor. Our results provide BPs configurations with dissymmetry factor as high as -0.3.

Automated summary

Chiral nanomaterials, especially plasmonic bipyramids, have attracted attention for their ability to modulate optical properties and dissymmetry factors. By studying the orientations of gold bipyramids in dimers, researchers observed changes in chiroptical properties through modulation of extinction spectra and local field enhancement. Assessing the chirality of different arrangements revealed configurations with dissymmetry factors as high as -0.3.