Emergent chiroptical properties in supramolecular and plasmonic assemblies

This tutorial provides a comprehensive description of the origin of chiroptical properties of supramolecular and plasmonic assemblies in the UV-visible region of the electromagnetic spectrum. The photophysical concepts essential for understanding chiroptical signatures are presented in the first section. Just as the oscillator strength (a positive quantity) is related to absorption, the rotational strength (either a positive or a negative quantity) defines the emergence of chiroptical signatures in molecular/plasmonic systems. In supramolecular systems, induced circular dichroism (ICD) originates through the off-resonance coupling of transition dipoles in chiral inclusion complexes, while exciton coupled circular dichroism (ECD) originates through the on-resonance exciton coupling of transition dipoles in chiral assemblies resulting in the formation of a bisignated CD signal. In bisignated ECD spectra, the sign of the couplet is determined not only by the handedness of chiral supramolecular assemblies, but also by the sign of the interaction energy between transition dipoles. Plasmonic chirality is briefly addressed in the last section, focusing on inherent chirality, induced chirality, and surface plasmon-coupled circular dichroism (SP-CD). The oscillator strength is of the order of 1 in molecular systems, while it becomes very large (10(4)-10(5)) in plasmonic systems due to the collective plasmonic excitations, resulting in intense CD signals, which can be exploited for the design of plasmonic metamaterial platforms for chiral sensing applications.

Automated summary

This tutorial provides a comprehensive description of the origin of chiroptical properties in supramolecular and plasmonic assemblies in the UV-visible region, explaining the essential photophysical concepts for understanding chiroptical signatures. The tutorial also discusses the origins of induced circular dichroism (ICD) and exciton coupled circular dichroism (ECD) in molecular and plasmonic systems, as well as plasmonic chirality, focusing on inherent chirality, induced chirality, and surface plasmon-coupled circular dichroism (SP-CD). Additionally, it highlights the differences in oscillator strength between molecular and plasmonic systems, emphasizing the potential for intense CD signals in plasmonic systems for chiral sensing applications.