Sculpting Chirality at the Nanoscale: Size-Dependent Enantioselectivity in Nanoparticles from MD and DFT

The morphology of metal nanoparticles has long since been known to significantly influence their physiochemical properties, with nanoscale chirality and nanoparticle size being identified as two areas of significant interest. Gold nanoparticles (AuNPs) in particular have been noted for their interactions with chiral molecules, and have since become an active area of research to better understand chirality transfer, enantiomeric selectivity, and molecular binding mechanisms at the nanoscale. Here, the effects of AuNP size on chiral interactions with amino acids, specifically cysteine, are explored by utilising both Density Functional Theory (DFT) calculations and Molecular Dynamics (MD) simulations, with a particular emphasis on size-dependent changes in enantioselective adsorption behaviour. Previous studies identify the Au-thiol bond as a root cause of chirality transfer, and have stated that nanoparticle size and surface structure heavily influence the binding orientation and subsequent stability of adsorbed cysteine enantiomers. The interactions of sub-10nm AuNPs with chiral cysteine molecules using reactive MD models are examined to determine how size-dependent structural changes influence enantioselective binding and adsorption modes, revealing significant differences in adsorption behaviour across the size range studied. Through this multiscale MD and DFT approach, we provide new insights into enantiomeric binding preferences and size-dependent chiral interactions and demonstrate how nanoparticle size can act as a tuneable parameter for enantioselective applications, including nanoscale catalysis and biosensing.