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Abstract In two-dimensional chiral metal-halide perovskites, chiral organic spacers endow structural and optical chirality to the metal-halide sublattice, enabling exquisite control of light, charge, and electron spin. The chiroptical properties of metal-halide perovskites have been measured by transmissive circular dichroism spectroscopy, which necessitates thin-film samples. Here, by developing a reflection-based approach, we characterize the intrinsic, circular polarization-dependent complex refractive index for a prototypical two-dimensional chiral lead-bromide perovskite and report large circular dichroism for single crystals. Comparison with ab initio theory reveals the large circular dichroism arises from the inorganic sublattice rather than the chiral ligand and is an excitonic phenomenon driven by electron-hole exchange interactions, which breaks the degeneracy of transitions between Rashba-Dresselhaus-split bands, resulting in a Cotton effect. Our study suggests that previous data for spin-coated films largely underestimate the optical chirality and provides quantitative insights into the intrinsic optical properties of chiral perovskites for chiroptical and spintronic applications.
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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.
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- Award ID(s):
- 1726332
- PAR ID:
- 10461404
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Particle & Particle Systems Characterization
- Volume:
- 36
- Issue:
- 5
- ISSN:
- 0934-0866
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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