Synthesis of Chiral Plasmonic Gold Nanoplates with Broad Chiroptical Activity

Plasmonic chiral nanostructure provides a novel route for extraordinary optical properties such as negative refractive index and light polarization control, and has drawn significant attention in various fields. The symmetry of chiral nanostructures such as helix, gyroid, and the irregular tetrahedron is deeply correlated to chiroptical responses and thus represents an important design parameter. Recently, we demonstrated a new pathway for facile synthesis of the chiral plasmonic nanoparticle by controlling the symmetry of gold nanoparticles utilizing enantioselective interactions on surface kink sites. Particularly, 432 symmetric helicoid nanoparticles were synthesized by breaking the mirror symmetry in single crystalline gold nanoparticles with 4/m 3 2/m symmetry. Here, we aimed to extend further the chiral symmetry of gold nanoparticles and their chiroptical properties. The symmetry of gold nanoparticles can be modulated from that of crystal lattice by inducing single or multiple twin planes in seed nanoparticles. We successfully synthesized chiral gold nanoplates with 3-fold symmetry by using triangular and hexagonal seed nanoplates with 3 2/m symmetry. Chiral gold nanoplates have great significance as they show optical activity in a wide range, from vis to NIR region. This approach provides insight into the changes in optical properties of the gold particles depending on symmetry and can be extended to a material platform for developing next-generation telecommunications and optical devices such as sensors and lidars.