Chiral Optical Force Generated by a Superchiral Near-Field of a Plasmonic Triangle Trimer as Origin of Giant Bias in Chiral Nucleation: A Simulation Study

Abstract

We previously reported that giant crystal enantiomeric excess (CEE) can be obtained when sodium chlorate (NaClO3) chiral crystallization from a solution is induced by the excitation of localized surface plasmon resonance (LSPR) of a Au triangle trimer nanostructure by a circularly polarized laser. However, the role of the LSPR excitation in the giant CEE remains unclear. In this work, we showed, by finite-difference time-domain analysis of plasmonic near-field, that the magnitude of a chiral optical gradient force originating from the strong superchiral near-field at the Au trimer nanogap on a virtual NaClO3 chiral crystalline cluster is comparable to that of the electric-field gradient force in previous laser-trapping-induced crystallization from unsaturated solution. We revealed that the giant CEE resulted from a difference in the frequency of attachment of chiral crystalline clusters to crystal nuclei or in the local concentration due to chirally biased diffusion rather than enantioselective optical trapping.

Chiral plasmonic nanostructures: recent advances in their synthesis and applications

“…270 In a follow-up paper, the same group explained this result by modeling the plasmonic near-field during illumination and showing that the large enantiomeric excess previously observed arose from a difference in the frequency of attachment of chiral crystalline clusters to crystal nuclei, or in the local concentration of NaClO 3 due to chirally biased diffusion, rather than from enantioselective optical trapping. 271 A similar light polarization-dependent chiral synthesis was documented using chiral metallic particles, which exhibited a different photocatalytic activity depending on the helicity of the illuminating light. 272 These observations may be explained by considering the different emission rates of hot electrons in chiral plasmonic particles upon illumination with circularly polarized light, [273][274][275] as experimentally measured by Fang et al in split ring resonators deposited on a semiconductor.…”

Recent developments in the chiroptical properties of chiral plasmonic gold nanostructures: bioanalytical applications

“…The nanoassembly was able to produce chiroplasmonic waves via chirality transfer for helicene to plasmonic bands. The helicene used were rac-9-(3-pyridylethylnyl) [7]helicene, rac-9-(4-pyridylethynyl) [7]helicene and racemic 2-(3-thienyl) [6]helicene. The complete information of a molecule in the solution was analysed with "cross" functionalization of the helicene enantiomers.…”

“…Life on earth manifests a priority for L-amino acids and D-sugars, in spite of a thermodynamic stability equilibrium of the L-and D-enantiomers of these molecules. The bioactivities of a chiral molecule depend on its handedness; for example, one enantiomer might act as a drug while the other might be toxic [7]. Accordingly, chirality of molecules has a vital role in functionality and interaction with other molecules.…”

Key Role of Asymmetric Photothermal Effect in Selectively Chiral Switching of Plasmonic Dimer Driven by Circularly Polarized Light

“…In a recent study, such a photothermal CD effect has been used to achieve selectively melting biomolecules located at the gap region of the chiral gold nanorod dimers (GNR-dimers). Besides, strong interaction of CPL with chiral plasmonic nanostructures can also generate remarkable chirality-dependent optical forces/torques. − Early studies , have found that those chirality-dependent optical forces/torques can give rise to asymmetric optomechanical effects, such as polarization-dependent pushing/pulling of a chiral nanoparticle. In a previous experimental study, we have proposed and demonstrated that CPL-induced asymmetrical optomechanical perturbations can be used to enable dynamic chiral configurations of the GNR-dimers in solution phase.…”