Chiral Noble Metal Nanoparticles and Nanostructures

The origins of chirality and chiroptical properties in ligand-protected gold and silver nanoparticles (NPs) are considered herein. Current conceptual models including the chiral core model, dissymmetric field model, and chiral footprint model are described as mechanisms that contribute to the understanding of chirality in these systems. Then, recent studies on thiolate-stabilized gold NPs, phosphine-stabilized gold NPs, multi-ligand-stabilized silver NPs, and DNA-stabilized silver NPs are discussed. Insights into the origin of chiroptical properties including reasons for large Cotton effects in circular dichroism spectra are considered using both experimental and theoretical data available. Theoretical calculations using density functional theory (DFT) and time-dependent DFT methods are found to be extremely useful for providing insights into the origin of chirality. The origin of chirality in ligand-protected gold and silver NPs can be considered to be a complex phenomenon, arising from a combination of the three conceptual models.