Chiral Noble Metal Nanoparticles and Nanostructures

Abstract

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.

Enantioseparation and chiral induction in Ag29 nanoclusters with intrinsic chirality

“…Chiral metal nanoclusters (NCs) with atomically precise structures have garnered great interest over the recent two decades because of their fascinating structural, electronic and optical properties. 1 Chirality can be introduced into the electronic properties of NCs either by intrinsically chiral atomic arrangements 2–18 or by employing chiral organic ligands such as chiral thiols. 19–25 While intrinsically chiral NCs possess a chiral atomic arrangement in the NC-core including the surface metal-thiolate networks as a stable structure, the use of achiral ligands leads to the formation of a racemic mixture.…”

“…3 b ,13 However, there has been no report on the enantioseparation of atomically precise chiral silver NCs, possibly because of reactive and less stable properties of silver NCs compared to gold NCs. 1,26 …”

Encoding Chiral Molecular Information in Metal Structures

“…There are reports describing the chiroptical behavior and circular dichroism (CD) signals generated by chiral ligand‐protected metal nanoparticles. This not only reveals the existence of novel optically active materials, but also provides information about chirality effects at the nanoscale …”

“…Therefore, the resulting metal nanoclusters are stabilized by organic ligands. To introduce chiral information on the metal nanoparticles, three main organic ligands/macromolecules types have been used, including phosphine ligands, thiolate ligands, and DNA …”

Effect of the Metal–Ligand Interface on the Chiroptical Activity of Cysteine‐Protected Nanoparticles

“…[ 3,4 ] Since these pioneer referential works, further experimental confirmation studies and theoretical approaches toward understanding the origin of chirality in metal NCs have been broadly published, reviewed, and discussed. [ 5–16 ]…”