Cysteine-encoded chirality evolution in plasmonic rhombic dodecahedral gold nanoparticles.

Chiral plasmonic nanostructures have opened up unprecedented opportunities in optical applications. We present chirality evolution in nanoparticles focusing on the crystallographic aspects and elucidate key parameters for chiral structure formation. From a detailed understanding of chirality formation, we achieved a morphology (432 Helicoid IV) of three-dimensionally controlled chiral plasmonic nanoparticles based on the rhombic dodecahedral shape. The role of the synthesis parameters, seed, cysteine, cetyltrimethylammonium bromide and ascorbic acid on chiral formation are studied, and based on this understanding, the systematic control of the chiral structure is presented. The relation between the modulated chiral structure factors and optical response is further elucidated by electromagnetic simulation. Importantly, a new optical response is achieved by assembling chiral nanoparticles into a film. This comprehensive study of chiral nanoparticles will provide valuable insight for the further development of diverse chiral plasmonic nanostructures with fascinating properties.