Circular dichroism from single plasmonic nanostructures with extrinsic chirality

Lu, Xuxing; Wu, Jian; Zhu, Qiannan; Zhao, Junwei; Wang, Qiangbin; Zhan, Li; Ni, Weihai

doi:10.1039/c4nr04433a

Cited by 96 publications

(89 citation statements)

References 36 publications

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“…By inducing an extra oblique CPL excitation, the planar gold www.advopticalmat.de nanorod dimer yielded chiroptical response. [75] The self assembly Vshape gold nanorod dimer was an achiral structure with planar mirror symmetry along the direction of the angle bisector of Vshape. However, the nanorod cannot geometrically coincide with its mirror image because the mirror symmetry is broken by the external oblique excitation.…”

Section: Plasmonic Chiral Metamoleculesmentioning

confidence: 99%

Plasmonic Chiral Nanostructures: Chiroptical Effects and Applications

Luo

Chi

Jiang

et al. 2017

Advanced Optical Materials

170

122

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(circular birefringence) and absorption losses (circular dichroism) with the circu larly polarized light (CPL) illumination. [10] CB arises from the difference in the real part of refractive index, leading to a dif ferent velocity for LCP and RCP compo nents, and thus results in the polarization rotation of the linearly polarized incident light. CD corresponds to the difference in the imaginary part of refractive index, resulting in a distinct absorption loss for LCP and RCP excitations. Besides the con ventional CD and CB, asymmetric trans mission (circular conversion dichroism) is another fundamental chiroptical pheno menon, which exists in the nondiffracting array, referring to different LCPtoRCP and RCPtoLCP conversion efficiencies. [11] All of these chiroptical phenomena have been successfully applied in the spectros copy for identifying special arrangements of chiral matters in biology, chemistry and physics as efficient diagnostic tools. [12][13][14][15][16] However, the chirop tical response in natural chiral materials is relatively weak due to the small electromagnetic (EM) interaction volume, [17] hence limits its further applications.Recent progress in plasmonics paves the way for the enhancement of chiroptical response. [18][19][20] Surface plasmons (SPs), as the collective electrons oscillation at the dielectric and metal interface, [21][22][23] present the capacity of light confine ment and field enhancement, which significantly improve the strength of lightmatter interactions. [24][25][26][27][28] With the uptodate nanofabrication technology, the study field of chirality has been extended from traditional chiral molecules to 3D metallic nanostructures. [29][30][31][32] Chiroptical responses of metallic meta molecules have been widely investigated, [33][34][35] and applied in various fields, such as biosensing, [36] chiral catalysis, [37] polari zation tuning, [38] and chiral photo detection.[39] The 3D metallic structure exhibited giant optical activity response because of the strong interaction between electric and magnetic resonant modes. [40,41] Different from 3D chiral ensembles, planar chiral structures show none chiral effect, as they can always coincide with their mirror images. However, 2D chirality was successfully found in the quasitwodimensional (quasi2D) chiral structure. [42] Moreover, recent reports show that even achiral nanomaterials have the ability to generate strong CD under an oblique CPL illumination. [43] This kind of extrinsic chirality arises from sym metry breaking of the incident light and the quasi2D material, which is quite different from the intrinsic chirality of 3D chiral The plasmonic chiroptical effect has been used to manipulate chiral states of light, where the strong field enhancement and light localization in metallic nanostructures can amplify the chiroptical response. Moreover, in metamaterials, the chiroptical effect leads to circular dichroism (CD), circular birefringence (CB), and asymmetric transmission. Potential applications enabled by chiral plasmonics...

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Section: Plasmonic Chiral Metamoleculesmentioning

confidence: 99%

Plasmonic Chiral Nanostructures: Chiroptical Effects and Applications

Luo

Chi

Jiang

et al. 2017

Advanced Optical Materials

170

122

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“…This excitation geometry avoided contributions from an extrinsic CDS signal of achiral nanoparticles as reported recently. 48 These in-plane averaged measurements are not directly comparable to ensemble measurements which necessarily average over all possible incident directions in three dimensions, but simulations for this particular AuNR dimer system suggest that the difference between in-plane averaged and 3D excitation does not change the lineshape of the CDS spectrum ( Figure S4). We first considered the departure from perfect circular polarized excitation, which is experimentally unfeasible to achieve with a dark-field condenser over a broad wavelength range.…”

mentioning

confidence: 99%

“…47 However, despite the otherwise successful use of single-particle spectroscopy very few studies exist on the CD response of chiral plasmonic nanostructures. 16,17,24,34,48 Among these few reports, elegant CD spectroscopy using non-linear spectroscopy 17,23,49 and near-field microscopy 24 did not yield either pure absorption or scattering, while CD spectra measured in a dark-field scattering microscope 48 resulted from achiral nanostructures due to the geometry created by oblique angle excitation.…”

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confidence: 99%

Circular Differential Scattering of Single Chiral Self-Assembled Gold Nanorod Dimers

Wang¹,

Smith²,

et al. 2015

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Circular dichroism spectroscopy is essential for structural characterization of proteins and chiral nanomaterials. Chiral structures from plasmonic materials have extraordinary strong circular dichroism effects compared to their molecular counterparts. While being extensively investigated, the comprehensive account of circular dichroism effects consistent with other plasmonic phenomena is still missing. Here we investigated the circular differential scattering of a simple chiral plasmonic system, a twisted side-by-side Au nanorod dimer, using single-particle circular dichroism spectroscopy complimented with electromagnetic simulations. This approach enabled us to quantify the effects of structural symmetry breaking, namely, size-mismatch between the constituent Au nanorods and large twist angles on the resulting circular differential scattering spectrum. Our results demonstrate that, if only scattering is considered as measured by dark-field spectroscopy, a homodimer of Au nanorods with similar sizes produces a circular differential scattering line shape that is different from the bisignate response of the corresponding conventional CD spectrum, which measures extinction, that is, the sum of scattering and absorption. On the other hand, symmetry breaking in a heterodimer with Au nanorods with different sizes yields a bisignate circular differential scattering line shape. In addition, we provide a general method for correcting linear dichroism artifacts arising from slightly elliptically polarized light in a typical dark-field microscope, as is necessary especially when measuring highly anisotropic nanostructures, such as side-by-side nanorods. This work lays the foundation for understanding absorption and scattering contributions to the CD line shape of single chiroplasmonic nanostructures free from ensemble-averaging, especially important for self-assembled chiral nanostructures that usually exist as both enantiomers.

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“…Strong optical activity and high tunability make such structures favorable candidates for a number of applications, including polarization detection and imaging [15]. So far, extrinsic chirality has been demonstrated for a number of plasmonic structures, including split-rings [16][17][18], nanorod dimers [19], nanorice heterodimers [20], etc.…”

Section: Introductionmentioning

confidence: 99%

Extrinsic chirality of non-concentric plasmonic nanorings

Bochenkov

Klös

Sutherland

2017

Opt. Mater. Express

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Abstract:We show how extrinsic chirality, i.e. the optical activity of achiral media exhibited at oblique light incidence, can be achieved in plasmonic nanorings by symmetry breaking. We demonstrate that even a small, 5% offset of an inner hole of a 190 nm gold ring results in a measurable circular dichroism signal in the near-infrared region. By using computer simulations, we show that optical activity arises upon excitation of a symmetric dipolar localized surface plasmon resonance mode due to the appearance of co-aligned electric and magnetic dipole moments.

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Circular dichroism from single plasmonic nanostructures with extrinsic chirality

Cited by 96 publications

References 36 publications

Plasmonic Chiral Nanostructures: Chiroptical Effects and Applications

Plasmonic Chiral Nanostructures: Chiroptical Effects and Applications

Circular Differential Scattering of Single Chiral Self-Assembled Gold Nanorod Dimers

Extrinsic chirality of non-concentric plasmonic nanorings

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