Cysteine-Mediated Etching of Gold Nanorods by Ferric Ions: Probing Cys Spatial Distribution Features on a Rod Surface

Modulating the interaction of chiral molecules with achiral plasmonic nanostructures/superstructures is an important means to realize the transfer of molecular chirality to plasmonic chirality. Especially, adsorption features of chiral molecules, such as chiral cysteine (Cys), have been found to affect chiroptical responses greatly. Herein, we found that Cys modification on gold nanorods (AuNRs) had a remarkable impact on rod etching by ferric ions and gave rise to unique etching patterns encoded with the information on Cys adsorption characteristics. Cys modification significantly accelerated rod etching by bringing Fe3+ to the rod surface via Fe3+-COO– coordination. In combination with transmission electron microscopy (TEM) characterization, we were able to decipher Cys-mediated etching patterns and reconstruct Cys adsorption features on the rod surface. Our findings provide an etch-based strategy to probe the adsorption and spatial distribution of Cys on the rod surface, which will deepen our understanding of chirality transfer mechanisms and provide rational design rules for enhancing plasmonic chirality.