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

Wang, Lin Yung; Smith, Kyle W.; Domínguez-Medina, Sergio; Moody, Nicole; Olson, Jana; Zhang, Huanan; Kotov, Nicholas A.; Link, Stephan

doi:10.1021/acsphotonics.5b00395

Cited by 110 publications

(132 citation statements)

References 65 publications

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“…In all the mentioned cases, it is of large interest to study single structures and unravel the influence of even minute conformational differences or to track changes in time on a single structure level. Dark‐field scattering spectroscopy has been widely used to measure the (chiral) optical response of single plasmonic molecules or particles, such as extrinsically chiral systems, self‐assembled 3D structures, or lithographically prepared planar chiral nanostructures . Here, we show that this concept is also applicable for the characterization of single chiral plasmonic molecules by analyzing the influence of structural defects on the chiral optical response.…”

Section: Introductionmentioning

confidence: 89%

Single Plasmonic Oligomer Chiral Spectroscopy

Karst

Strohfeldt

Schäferling

et al. 2018

Advanced Optical Materials

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dispersion. In general, these two quantities are Kramers-Kronig related. [3] Both effects can be utilized to study chiral molecules, with circular dichroism spectroscopy being the most commonly used. Chirality is a powerful method to analyze the 3D conformation of molecules as it is an intrinsically 3D property. CD spectra can help to unravel the secondary structure of proteins, which is ultimately responsible for the interaction of proteins and for the biologically and physiologically relevant processes. [4] That said, it is obvious that the exact conformation of a molecule and the differences between the molecules of an ensemble are of paramount interest. However, in chemistry and biology the CD of many molecules is measured in a solution with a CD spectrometer, as the CD response of a single molecule appears to be too small to be determined. This measurement scheme obstructs the contribution of the individual molecule and thus does not allow for single molecule based secondary structure investigations. In recent years, researchers have been intensely studying chiral plasmonic systems. [5][6][7][8][9][10][11][12] A plasmon is the collective oscillation of the quasi-free conduction electrons in a metallic nanoparticle. Such plasmon resonances have large resonant light interaction cross sections which allow for the detection and measurement of single nanostructures. What is more, the locally enhanced near-fields associated with the plasmon resonance allow to couple adjacent nanoparticles and create plasmonic molecules of nearly arbitrary complexity. Due to advances in the top-down techniques related to micro-and nanofabrication, we are able to structure such systems in two and three dimensions nearly at will. [13][14][15] Additionally, bottomup techniques, such as DNA-mediated self-assembly, [16][17][18][19][20] even allow for switchable chiral structures. [21][22][23][24][25][26][27][28] Two aspects are of particular importance here: On the one hand, the tunability of these systems allows studying the properties of chirality in great detail while having full control over the chiral plasmonic structures, [29,30] which is in stark contrast to molecular systems whose structures cannot be manipulated easily. On the other hand, researchers are searching for interactions between chiral (bio)-molecules and chiral plasmonic molecules which could lead to decreased detection limits. [31][32][33][34][35][36] In all the mentioned cases, it is of large interest to study single structures and unravel the influence of even minute conformational differences or to track changes in time on a single structure level. Dark-field scattering spectroscopy has been widely used to measure the (chiral) optical response of single Chirality plays a crucial role in our everyday lives. Many biomolecules are handed and the associated biological processes rely on their handedness. Thus, chirality is investigated intensely, also because of the fundamental and inherent interest in the concept of chirality. However, virtually all studies are perfo...

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Section: Introductionmentioning

confidence: 89%

Single Plasmonic Oligomer Chiral Spectroscopy

Karst

Strohfeldt

Schäferling

et al. 2018

Advanced Optical Materials

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“…Auguié et al demonstrated that the plasmonic interaction in such nanorod dimers is analogous to energy level hybridization and leads to a bisignate response (see Section ). Wang et al also studied the effect experimentally and theoretically. The authors investigated circular differential scattering (CDS), which measures the difference in scattered light for LCP and RCP light, and CD using dark field microscopy.…”

Section: Design Of Chiral Materialsmentioning

confidence: 99%

Chirality and Chiroptical Effects in Metal Nanostructures: Fundamentals and Current Trends

Collins

Kuppe

Hooper

et al. 2017

Advanced Optical Materials

288

246

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Throughout the 19th and 20th century, chirality has mostly been associated with chemistry. However, while chirality can be very useful for understanding molecules, molecules are not well suited for understanding chirality. Indeed, the size of atoms, the length of molecular bonds and the orientations of orbitals cannot be varied at will. It is therefore difficult to study the emergence and evolution of chirality in molecules, as a function of geometrical parameters. By contrast, chiral metal nanostructures offer an unprecedented flexibility of design. Modern nanofabrication allows chiral metal nanoparticles to tune the geometric and optical chirality parameters, which are key for properties such as negative refractive index and superchiral light. Chiral meta/nano‐materials are promising for numerous technological applications, such as chiral molecular sensing, separation and synthesis, super‐resolution imaging, nanorobotics, and ultra‐thin broadband optical components for chiral light. This review covers some of the fundamentals and highlights recent trends. We begin by discussing linear chiroptical effects. We then survey the design of modern chiral materials. Next, the emergence and use of chirality parameters are summarized. In the following part, we cover the properties of nonlinear chiroptical materials. Finally, in the conclusion section, we point out current limitations and future directions of development.

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“…The interaction between chiral electromagnetic plane waves, such as circularly polarized light (CPL), and matter is inherently limited in sensitivity due to their bounded spatial distribution. Rapidly-evolving research efforts in the field of chiral nanophotonics aim to address this challenge by the tailored design of metallic [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] and dielectric [29][30][31][32][33][34][35][36][37][38] nanostructures, arranged periodically in sub-wavelength metamaterials and metasurfaces, or in colloidal dispersions, achieving highly concentrated electromagnetic chirality in their evanescent field (see also review articles [25,[39][40][41][42]). However, the rational design of enhanced electromagnetic chirality in the presence of matter requires the definition of physical observables by which to quantify the chirality of light.…”

Section: Introductionmentioning

confidence: 99%

Optical Helicity and Optical Chirality in Free Space and in the Presence of Matter

2019

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The inherently weak nature of chiral light–matter interactions can be enhanced by orders of magnitude utilizing artificially-engineered nanophotonic structures. These structures enable high spatial concentration of electromagnetic fields with controlled helicity and chirality. However, the effective design and optimization of nanostructures requires defining physical observables which quantify the degree of electromagnetic helicity and chirality. In this perspective, we discuss optical helicity, optical chirality, and their related conservation laws, describing situations in which each provides the most meaningful physical information in free space and in the context of chiral light–matter interactions. First, an instructive comparison is drawn to the concepts of momentum, force, and energy in classical mechanics. In free space, optical helicity closely parallels momentum, whereas optical chirality parallels force. In the presence of macroscopic matter, the optical helicity finds its optimal physical application in the case of lossless, dual-symmetric media, while, in contrast, the optical chirality provides physically observable information in the presence of lossy, dispersive media. Finally, based on numerical simulations of a gold and silicon nanosphere, we discuss how metallic and dielectric nanostructures can generate chiral electromagnetic fields upon interaction with chiral light, offering guidelines for the rational design of nanostructure-enhanced electromagnetic chirality.

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

Cited by 110 publications

References 65 publications

Single Plasmonic Oligomer Chiral Spectroscopy

Single Plasmonic Oligomer Chiral Spectroscopy

Chirality and Chiroptical Effects in Metal Nanostructures: Fundamentals and Current Trends

Optical Helicity and Optical Chirality in Free Space and in the Presence of Matter

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