Chiroptically Active 1D Ultrathin AuAg Nanostructures

Abstract

Chirality plays a major role in chemistry, biology, pharmacology, and medicine. Therefore, the development of chiral nanomaterials is critical for producing more selective and sensitive smart technology in the future. Here, we present, for the first time, the chiral modification of ultrathin AuAg nanowires (NWs) (with 9 and 3.6 nm average diameter) and ultrathin AuAg nanonecklace (NNL) structures through a ligand exchange method and show that both cysteine and l-glutathione can induce chiroptical activity in these ultrathin 1D nanomaterials. By monitoring the evolution of chiroptical activity with time via circular dichroism analysis, we found that the l-glutathione ligand exchange is a more gradual process for both NWs and NNLs, while cysteine binds instantly. Density functional theory calculations reveal that the thiol and other interacting moieties in cysteine and glutathione adsorb preferentially on the Ag atoms of the AuAg NW surface. Calculations also indicate that cysteine ligand binds more strongly compared to glutathione, which requires the rearrangement of the surrounding water molecules to promote hydrogen bonding, hindering the kinetics of the ligand exchange process. Overall, these results pave the way for developing new chiral ultrathin 1D metal nanostructures and understanding the nature of binding of chiral ligands in these nanomaterials.