Chiral assembly of gold nanorods with collective plasmonic circular dichroism response

In this work, a chiral hybrid superstructure has been achieved through a hierarchical, cooperative self-assembly/self-organization process in a multiple-component system comprising of gold nanorods, surfactants, and phospholipids film. This chiral hybrid superstructure presented a signate signal in plasmonic circular dichroism with negative collective plasmonic modes on one side of the plasmon resonance and positive modes on the other side. The origin of such an unusual optical activity is fundamentally different from that of chiral metal nanoparticles/nanoclusters in previous studies. We highlight here a possibility that helical alignment of gold nanorods in the hybrid superstructure would resemble mesogenic molecules in a cholesteric liquid crystalline mesophase, and the Coulomb dipole-dipole interactions between gold nanorods in such a chiral liquid crystalline-like mesophase would give rise to the plasmonic circular dichroism effect. This study also demonstrated a facile approach for fabricating chiral superstructures from preformed metal nanoparticles with defined shapes, sizes, and compositions, which may have values in exploiting novel plasmonic nanostructures with tunable optical activity responses in the visible/NIR region for a variety of bioscience and biomedicine applications.