Plasmonic Ratchet Wheels: Switching Circular Dichroism by Arranging Chiral Nanostructures

Valev, Ventsislav K.; Smisdom, Nick; Silhanek, Alejandro; Clercq, Ben De; Gillijns, Werner; Ameloot, Marcel; Мощалков, В.В.; Verbiest, Thierry

doi:10.1021/nl9021623

Cited by 223 publications

(193 citation statements)

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“…This molecular system has two quantum states and, under illumination, it acquires nonzero optical electric and magnetic moments ( Figure 1a). These transition moments will be given by the corresponding matrix elements for the molecular quantum states, denoted as μ 12 and m 21 . The electric dipole moment of a molecule (μ 12 ) can be either normal or parallel to the NC surface ( Figure 1a).…”

Section: Formalismmentioning

confidence: 99%

“…This is important for the formation of the plasmon-induced CD that originates from the interaction between the dipole and the plasmon component. The direction of the magnetic dipole moment (m 21 ) with respect to the vector μ 12 is also essential, since their relative orientation controls the magnitude and sign of the whole CD band. Optical responses of the crystalline NCs were computed using empirical local dielectric functions: ref.…”

Section: Formalismmentioning

confidence: 99%

“…where ℏω 0 and Γ = Γ 12 are the molecular resonance energy and its broadening, respectively; µ µ 12 and m m 21 are the matrix elements of the optical dipoles as defined above and n 0 is the density of randomly oriented chiral biomolecules. The product µ µ ⋅ m m 12 21 in Equation (18) is an imaginary number, that is, µ µ ⋅ = m m ia 12 21 , where a is real.…”

Section: Quantum Theory Of Molecular CDmentioning

confidence: 99%

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Aluminum Nanoparticles with Hot Spots for Plasmon‐Induced Circular Dichroism of Chiral Molecules in the UV Spectral Interval

Besteiro

Zhang

Plain

et al. 2017

Advanced Optical Materials

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absorb and scatter visible light and, furthermore, plasmonic NCs are known for their strong local enhancement of electromagnetic fields. When a chiral biomolecule is attached to a nonchiral metal NC, the chiral response of a biomolecule becomes transferred to the plasmonic NC via near-field dipolar and multipolar interactions. [4,5] Circular dichroism spectroscopy, which quantifies the difference between the assembly's responses to left and right circularly polarized light, is a well-established experimental method to measure the chiral properties of an assembly. In the biomolecule-NC assembly, CD spectra typically show modified molecular lines, in addition to including new lines coming from plasmon excitations in the NCs. It was demonstrated in a large number of experiments [3,6,7] that it is possible to observe plasmon-induced CD in the visible spectral interval using NCs made of gold and silver. It is a very interesting possibility, since the original CD signals of important biomolecules (such as proteins and DNA) are typically in the UV spectral region. In addition to the material composition of an assembly, its design also plays an important role. For example, the plasmoninduced CD can be strongly enhanced by using NC assemblies Plasmonic nanocrystals with hot spots are able to localize optical energy in small spaces. In such physical systems, near-field interactions between molecules and plasmons can become especially strong. This paper considers the case of a nanoparticle dimer and a chiral biomolecule. In this model, a chiral molecule is placed in the gap between two plasmonic nanoparticles, where the electromagnetic hot spot occurs. Since many important biomolecules have optical transitions in the UV spectral region, the case of aluminum nanoparticles is considered, as they offer strong electromagnetic enhancements in the blue and UV spectral intervals. The calculations in this study show that the complex composed of a chiral molecule and an Al dimer exhibits strong circular dichroism (CD) signals in the plasmonic spectral region. In contrast to the standard Au and Ag nanocrystals, the Al system may have a much better spectral overlap between the typical biomolecule's optical transitions and the nanocrystals' plasmonic band. Overall, it is found that Al nanocrystals used as CD antennas exhibit unique properties as compared to other commonly studied plasmonic and dielectric materials. The plasmonic systems investigated in this study can be potentially used for sensing chirality of biomolecules, which is of interest in applications such as drug development.

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Section: Formalismmentioning

confidence: 99%

Section: Formalismmentioning

confidence: 99%

Section: Quantum Theory Of Molecular CDmentioning

confidence: 99%

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Aluminum Nanoparticles with Hot Spots for Plasmon‐Induced Circular Dichroism of Chiral Molecules in the UV Spectral Interval

Besteiro

Zhang

Plain

et al. 2017

Advanced Optical Materials

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show abstract

“…A number of asymmetric plasmonic geometries have been used for harmonic generation, including L-and V-shaped nanoparticles, nanocups, and asymmetric trimers [3][4][5][6][7]. Larger plasmonic structures-such as the ratchet wheel-have also been shown to affect the polarization of harmonic emission [8][9][10][11][12].However, even though metallic nanostructures can generate significant second-order nonlinear response per volume, the nanostructure unit volume is incredibly small [13]. High efficiency is therefore also crucial in order to generate reasonable numbers of photons in nonlinear processes without melting or damaging the nanostructures.…”

mentioning

confidence: 99%

Efficient forward second-harmonic generation from planar archimedean nanospirals

et al. 2015

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Abstract:The enhanced electric field at plasmonic resonances in nanoscale antennas can lead to efficient harmonic generation, especially when the plasmonic geometry is asymmetric on either inter-particle or intra-particle levels. The planar Archimedean nanospiral offers a unique geometrical asymmetry for second-harmonic generation (SHG) because the SHG results neither from arranging centrosymmetric nanoparticles in asymmetric groupings, nor from non-centrosymmetric nanoparticles that retain a local axis of symmetry. Here, we report forward SHG from planar arrays of Archimedean nanospirals using 15 fs pulses from a Ti:sapphire oscillator tuned to 800 nm wavelength. The measured harmonic-generation efficiencies are 2.6·10 −9 , 8·10 −9 and 1.3·10 −8 for left-handed circular, linear, and right-handed circular polarizations, respectively. The uncoated nanospirals are stable under average power loading of as much as 300 µW per nanoparticle. The nanospirals also exhibit selective conversion between polarization states. These experiments show that the intrinsic asymmetry of the nanospirals results in a highly efficient, two-dimensional harmonic generator that can be incorporated into metasurface optics.Keywords: nonlinear plasmonics, asymmetric nanoparticles, polarization conversion, metasurfaces, near-field enhancement, Archimedean nanospirals The second-order susceptibility governs a host of important nonlinear optical phenomena, including frequency mixing, sum-frequency and harmonic generation, and optical rectification. In crystalline and molecular materials, second-order nonlinearities are nonvanishing only at surfaces or in materials with a noncentrosymmetric crystal structure; moreover, the efficient generation of a second-order nonlinear effect requires that the fundamental incident and the nonlinear outgoing waves be phase matched through a macroscopic volume of material, typically on the order of cubic millimeters [1].Plasmonic nanostructures and nanostructure arrays also exhibit second-order nonlinearities, and can generate forward second harmonics if their geometries are not centrosymmetric. Such structures are inherently planar, and therefore compatible with thin-film optical and optoelectronic technologies and with metasurface optics. With advances in nanofabrication, the symmetry of the structures can be exquisitely controlled at the level of a few nanometers [2]. Combining these effects with ultrafast, high-intensity laser pulses yields massive electricfield enhancements and correspondingly greater secondharmonic yield. The localized surface plasmon resonance enhances efficiency and can be designed by selecting the nanoparticle shape for a given wavelength; selective polarization response can also be designed into the nanoparticle. A number of asymmetric plasmonic geometries have been used for harmonic generation, including L-and V-shaped nanoparticles, nanocups, and asymmetric trimers [3][4][5][6][7]. Larger plasmonic structures-such as the ratchet wheel-have also been shown to affect the polarization o...

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“…The experimental study is performed with second harmonic generation (SHG) microscopy, a technique whose usefulness for visualizing fi eld enhancements in nanostructures has been demonstrated in several works already. [22][23][24][25][26][27] We use ultrafast pulsed lasers ( ∼ 100 fs, 82 MHz), which are capable of delivering very high electric fi eld intensities to the electron population in the nanostructures. When the intense electric fi eld of light becomes comparable with the electric near-fi elds, the oscillations of the electron density are driven in the nonlinear (anharmonic) regime.…”

mentioning

confidence: 99%

Distributing the Optical Near‐Field for Efficient Field‐Enhancements in Nanostructures

et al. 2012

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Circularly polarized light imparts a sense of rotation on the electron density in ring‐shaped gold nanostructures. As a consequence, the near‐field enhancement becomes homogeneous on the surface of the nanostructures, thereby increasing the opportunity for interaction with molecules. This type of nanostructured samples can find a broad range of applications in chemical processes where the interaction between molecules and local field enhancements play an important role.

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Plasmonic Ratchet Wheels: Switching Circular Dichroism by Arranging Chiral Nanostructures

Cited by 223 publications

References 29 publications

Aluminum Nanoparticles with Hot Spots for Plasmon‐Induced Circular Dichroism of Chiral Molecules in the UV Spectral Interval

Aluminum Nanoparticles with Hot Spots for Plasmon‐Induced Circular Dichroism of Chiral Molecules in the UV Spectral Interval

Efficient forward second-harmonic generation from planar archimedean nanospirals

Distributing the Optical Near‐Field for Efficient Field‐Enhancements in Nanostructures

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