Molecular-Induced Chirality Transfer to Plasmonic Lattice Modes

Abstract

Molecular chirality plays fundamental roles in biology. The chiral response of a molecule occurs at a specific spectral position, determined by its molecular structure. This fingerprint can be transferred to other spectral regions via the interaction with localized surface plasmon resonances of gold nanoparticles. Here, we demonstrate that molecular chirality transfer occurs also for plasmonic lattice modes, providing a very effective and tunable means to control chirality. We use colloidal self-assembly to fabricate non-close packed, periodic arrays of achiral gold nanoparticles, which are embedded in a polymer film containing chiral molecules. In the presence of the chiral molecules, the surface lattice resonances (SLRs) become optically active, i.e., showing handedness-dependent excitation. Numerical simulations with varying lattice parameters show circular dichroism peaks shifting along with the spectral positions of the lattice modes, corroborating the chirality transfer to these collective modes. A semi-analytical model based on the coupling of singlemolecular and plasmonic resonances rationalizes this chirality transfer.

Nanocrystal Assemblies: Current Advances and Open Problems

“…Another direction is superstructures that provide chiral SLRs. Chiral SLRs can be realized by fabricating superlattices with chiral plasmonic nanostructures , or by inducting optical chirality into otherwise achiral superstructures using chiral molecules …”

“…Chiral SLRs can be realized by fabricating superlattices with chiral plasmonic nanostructures 612,613 or by inducting optical chirality into otherwise achiral superstructures using chiral molecules. 614 Challenges regarding SLRs comprise (i) the fabrication of non-close-packed superstructures that are periodic in all directions, (ii) understanding the role of defects and structural imperfections on the quality factor of coupled, collective resonances, (iii) improving quality factors of SLRs from selfassembled periodic plasmonic arrays, (iv) use of chiral SLRs in advanced biodetection, (v) manipulating SLRs by external parameters such as mechanic deformation of the lattice and (reversible) changes of the refractive index in the dielectric environment (substrate or superstrate), and (vi) coupling of SLRs to gain media (emitter) to produce plasmonic nanolasers or sources of chiral light in the case of chiral SLRs. 7.5.…”

The Mechanism of Manipulating Chirality and Chiral Sensing Based on Chiral Plexcitons in a Strong-Coupling Regime

“…Notably, there is a systematic overlap between SECD systems and CPM systems [ 22 , 23 , 24 ]. However, previous studies of SECD systems did not generate chiral plexcitons due to the resonance mismatch between the chiral molecules and the achiral plasmonic nanoparticles, resulting in no novel CD spectral splitting being observed [ 7 , 25 , 26 ]. If chiral properties are introduced into a CPM system, for instance, an excitonic material with a chiroptical response or colloidal plasmonic nanoparticles with a chiral geometry, then due to the half-light–half-matter hybrid-state nature of the plexcitons, the entire CPM system will also have a chiroptical response, and be termed a chiral plexcitonic system [ 27 , 28 , 29 ].…”