A First-Principles Study of l‑Glutathione Adsorption on Chiral Gold Nanoparticles

The chiral 432 helicoids II and III gold (Au) nanoparticles have been successfully synthesized using l-glutathione (L-GSH) as the chiral shape modifier; however, how L-GSH interacts with Au surfaces to trigger and promote the formation of chiral shapes remains unknown. In this work, the selectivity of L-GSH on enantiomeric Au(321) ^R/S is investigated using first-principles density functional theory (DFT). To avoid a resource- and time-consuming brute-force geometric scan of a full L-GSH molecule adsorbed on Au(321) ^R/S , we first decomposed L-GSH into three amino acid analogues, namely, l-glutamic acid (l-Glu), l-cysteine (l-Cys), and glycine (Gly), and reduced the chiral Au(321) ^R/S facets into constituent microfacets, namely, Au(111), Au(100), and Au(110). By understanding how each molecular building block interacts with these three low-Miller-index facets, we rationally designed six sets of initial configurations of L-GSH adsorbed on Au(321) ^R/S and performed optimization to identify the most thermodynamically stable structures. We find that L-GSH enantioselectively binds more strongly to Au(321) ^R , but the enantiomeric shift in binding energy is small. Regardless of the facet chirality, all strong-binding configurations exhibit a "reach-and-stretch" mechanism to maximize contact between L-GSH and kinks, multiple steps, and terraces, where both thiol and amine groups play critical roles. The enantioselectivity reported herein supports experiments where L-GSH is observed to promote the expression of Au(321) ^R , and the laterally extended conformation of L-GSH on Au(321) can inspire future studies on the roles of L-GSH in inducing chiral shape formation.