Superchiral hot-spots in “real” chiral plasmonic structures

Gilroy, Cameron; Koyroytsaltis-McQuire, D.; Gadegaard, Nikolaj; Karimullah, Affar S.; Kadodwala, Malcolm

doi:10.1039/d1ma00831e

Cited by 16 publications

(12 citation statements)

References 22 publications

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“…In addition, we observed that the local helicity of the NR surface often changes sign within the same particle. Local helicity could couple to strong local plasmonic fields at sharp corners and edges, leading to a possible dominance of local chiral features in the chiroptical response . Although the simulation results in Figure c question whether this is really the case, they cannot exclude that a local plasmonic effect occurs for highly asymmetric particles with sharp local features as the presented NRs.…”

Section: Resultsmentioning

confidence: 88%

“…These measurements revealed that anisotropies and asymmetries, for example, in surface facets distributions, can cause “accidental” geometrical chiral features and might be responsible for the unexpected chiroptical responses. In combination with possible electromagnetic enhancements of local chiral features, these geometrical features can result in strong, although not controllable, g -factors . We can conclude that there is still a lot to be learned about the origin of chiroptical activity in plasmonic systems and showed that single NP correlative measurements are an important tool to do so.…”

Section: Discussionmentioning

confidence: 94%

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Photothermal Circular Dichroism Measurements of Single Chiral Gold Nanoparticles Correlated with Electron Tomography

et al. 2022

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Chemically synthesized metal nanoparticles with morphological chiral features are known to exhibit strong circular dichroism. However, we still lack understanding of the correlation between morphological and chiroptical features of plasmonic nanoparticles. To shed light on that question, single nanoparticle experiments are required. We performed photothermal circular dichroism measurements of single chiral and achiral gold nanoparticles and correlated the chiroptical response to the 3D morphology of the same nanoparticles retrieved by electron tomography. In contrast to an ensemble measurement, we show that individual particles within the ensemble display a broad distribution of strength and handedness of circular dichroism signals.Whereas obvious structural chiral features, such as helical wrinkles, translate into chiroptical ones, nanoparticles with less obvious chiral morphological features can also display strong circular dichroism signals. Interestingly, we find that even seemingly achiral nanoparticles can display large g-factors. The origin of this circular dichroism signal is discussed in terms of plasmonics and other potentially relevant factors.

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Section: Resultsmentioning

confidence: 88%

Section: Discussionmentioning

confidence: 94%

Photothermal Circular Dichroism Measurements of Single Chiral Gold Nanoparticles Correlated with Electron Tomography

et al. 2022

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“…The CPL-active chiral nanostructures were fabricated via template-induced self-assembly of halide perovskite NC inks using three different pre-patterned poly(dimethylsiloxane) (PDMS) molds with 500 nm gammadion-like structures (9 mm 2 patterned areas) with left (L), right (R), and racemic (O) orientations in a square array with a periodicity of 600 nm (structure dimensions in Figure 1c). The gammadion geometry was chosen mainly due to the abundance of previous literature, [28][29][30]32,[41][42][43][44][45][46] which facilitates the comparison between the optical properties of the newly produced nanostructures by nanoimprinting lithography and previous results from structures produced by electronic lithography. Second, the C4 symmetry of the array helps minimizing the contribution to the PL from linearly polarized light which results in elliptical polarization.…”

Section: Resultsmentioning

confidence: 99%

Nanoimprinted 2D‐Chiral Perovskite Nanocrystal Metasurfaces for Circularly Polarized Photoluminescence

et al. 2023

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The versatile hybrid perovskite nanocrystals are one of the most promising materials for optoelectronics in virtue of their tunable bandgaps and high photoluminescence quantum yields. However, their inherent crystalline chemical structure limits the chiroptical properties achievable with the material. The production of chiral perovskites has become an active field of research for its promising applications in optics, chemistry or biology. Typically, chiral halide perovskites are obtained by the incorporation of different chiral moieties in the material. Unfortunately, these chemically modified perovskites have demonstrated moderate values of chiral photoluminescence so far. Here we introduce a general and scalable approach to produce chiral photoluminescence from arbitrary nano-emitters assembled into 2D-chiral metasurfaces. The fabrication via nanoimprinting lithography employs elastomeric molds engraved with chiral motifs covering millimeter areas that are used to pattern two types of unmodified colloidal perovskite nanocrystal inks: green-emissive CsPbBr3 and red-emissive CsPbBr1I2. The perovskite 2D-metasurfaces exhibit remarkable photoluminescence dissymmetry factors (glum) of 0.16 that can be further improved up to glum of 0.3 by adding a high refractive index coating on the metasurfaces. This scalable approach to produce chiral photoluminescent thin films paves

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“…Owing to the development of nanotechnology, we can nowadays artificially design novel materials, which exhibit high CD signals. Led by the exotic features of materials at the nanoscale, photonics community has, in fact, proposed plasmonic, − dielectric, − and hybrid − nanostructures with high intrinsic chirality in the visible range. Recent experimental studies prove that dielectric and plasmonic periodically arranged nanostructures can improve chiral sensing of specific enantiomers. , Moreover, even if the nanostructure is not intrinsically chiral, the symmetry of the light–matter interaction can be broken with an experimental setup .…”

Section: Introductionmentioning

confidence: 99%

Extrinsic Chirality and Circular Dichroism at Visible Frequencies Enabled by Birefringent α-MoO₃Nanoscale-Thick Films: Implications for Chiro-Optical Control

Petronijevic

Dereshgi

Larciprete

et al. 2022

ACS Appl. Nano Mater.

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Nanophotonics community has shown great interest in 2D materials because of their unique properties of electromagnetic field manipulation. Many of these materials exhibit strong natural anisotropy, which further opens possibilities of polarization manipulation. Here, we show that α-MoO 3 , an emerging natural hyperbolic 2D material, can be combined with plasmonic nanostructures to provide strong extrinsic chirality in the visible range. A combination of biaxial anisotropy in α-MoO 3 and Fabry−Perot cavities with nanoscale features leads to different absorption of left and right circularly polarized photons, hence exhibiting circular dichroism (CD). Our simulation results predict that multilayer nanoscale-thick films including α-MoO 3 are potential candidates for achieving extrinsic chirality across the visible range. Furthermore, we show a significant CD increase when the α-MoO 3 layer is coupled with plasmonic nanohole arrays or plasmonic nanocubes. Such designs are achiral in geometry and therefore easier to fabricate. Moreover, we optimize the CD dissymmetry factor g CD for the nanocube-based design at 780 nm, obtaining 84%. We believe that utilizing biaxially anisotropic α-MoO 3 films to control and engineer chiro-optical properties in the visible frequency range will open research directions and enable enhanced functionalities in chiro-optical control at the nanoscale, further leading to applications in chiral sensing and CD.

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Superchiral hot-spots in “real” chiral plasmonic structures

Abstract: Light scattering from chiral plasmonic structures can create near fields with an asymmetry greater than the equivalent circularly polarised light, a property sometimes referred to as superchirality.

Cited by 16 publications

References 22 publications

Photothermal Circular Dichroism Measurements of Single Chiral Gold Nanoparticles Correlated with Electron Tomography

Photothermal Circular Dichroism Measurements of Single Chiral Gold Nanoparticles Correlated with Electron Tomography

Nanoimprinted 2D‐Chiral Perovskite Nanocrystal Metasurfaces for Circularly Polarized Photoluminescence

Extrinsic Chirality and Circular Dichroism at Visible Frequencies Enabled by Birefringent α-MoO₃Nanoscale-Thick Films: Implications for Chiro-Optical Control

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Superchiral hot-spots in “real” chiral plasmonic structures

Abstract: Light scattering from chiral plasmonic structures can create near fields with an asymmetry greater than the equivalent circularly polarised light, a property sometimes referred to as superchirality.

Cited by 16 publications

References 22 publications

Photothermal Circular Dichroism Measurements of Single Chiral Gold Nanoparticles Correlated with Electron Tomography

Photothermal Circular Dichroism Measurements of Single Chiral Gold Nanoparticles Correlated with Electron Tomography

Nanoimprinted 2D‐Chiral Perovskite Nanocrystal Metasurfaces for Circularly Polarized Photoluminescence

Extrinsic Chirality and Circular Dichroism at Visible Frequencies Enabled by Birefringent α-MoO3Nanoscale-Thick Films: Implications for Chiro-Optical Control

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Extrinsic Chirality and Circular Dichroism at Visible Frequencies Enabled by Birefringent α-MoO₃Nanoscale-Thick Films: Implications for Chiro-Optical Control