- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Exploiting Evanescent Field Polarization for Giant Chiroptical Modulation from Achiral Gold Half-Rings
摘要： For applications seeking to realize on-chip polarization discriminating nanoantennas, efficient energy conversion from surface waves to far-field radiation is desirable. However, the response of individual nanoantennas to the particular polarization states achievable in surface waves, such as evanescent fields, has not yet been thoroughly investigated. Here, we report giant modulation of visible light scattering from achiral gold half-rings when switching between evanescent surface wave excitation produced from total internal reflection of left-handed and right-handed circularly polarized light. The effect is driven by a differing relative phase between the in-plane transverse and longitudinal field oscillations of the evanescent wave depending on the incident light handedness. As longitudinal field oscillations are not found in free-space excitation, this presents a fundamentally different mechanism for chiroptical responses as traditional mechanisms for circular dichroism only account for purely transversal field oscillations. Although the half-ring scattering modulation is dependent on the wave vector orientation, an orientation invariant response is also realized in planar chiral nanoantennas composed of eight half-rings in a rotationally symmetric arrangement, with up to 50% scattering modulation observed at 725 nm. Though both structures are found to produce scattering modulation when switching the handedness of free-space light, the distinct polarization properties of evanescent fields are shown to be strictly required to observe giant scattering modulation. These results ultimately deepen our understanding of the range of possible chiroptical effects in light-matter interactions.
关键词： nanoantenna,extrinsic chirality,evanescent fields,planar chirality,polarization discrimination,longitudinal field oscillations
更新于2025-09-23 15:21:21
-
Control on Dimensions and Supramolecular Chirality of Self-Assemblies through Light and Metal Ions
摘要： Precise control over helical chirality and dimensions of molecular self-assemblies, a remaining challenge for both chemists and materials scientists, is the key to manipulate the property and performance of supramolecular materials. Herein, we report that a cholesterol-azopyridine conjugate could self-assemble into organogels with photo-controllable dimensional transition from 2D microbelts to 1D nanotubes and finally to 0D nanoparticles. The E/Z-Photoisomerization of the 4-azopyridine unit is the major driving force for the dimensional transformation. Furthermore, the self-assembled structures were observed to exhibit metal ion-mediated helicity inversion through the metal coordination. These observations were collectively confirmed by several techniques including scanning electron microscopy, atomic force microscope, circular dichroism, and X-ray crystallography. The rational design of building blocks for the construction of dimension and chirality controllable self-assembly systems may lead to versatile applications in smart display, advanced optoelectronic device, and supramolecular asymmetric catalysis.
关键词： photoisomerization,dimensional transition,supramolecular chirality,metal coordination,self-assembly
更新于2025-09-23 15:21:21
-
Chiral Carbazoles
摘要： Asymmetric Synthesis of Axially Chiral Benzocarbazole Derivatives Based on Catalytic Enantioselective Hydroarylation of Alkynes
关键词： cyclization,axial chirality,benzocarbazoles
更新于2025-09-23 15:21:21
-
Non-classically Controlled Sign in a 1.6 Tesla Magnetic Circularly Polarized Luminescence of Three Pyrenes in a Chloroform and a PMMA Film
摘要： Molecular pyrene, 1-hydroxylpyrene, and 2-hydroxypyrene in chloroform and embedded in poly(methyl methacrylate) film reveal mirror-image magnetic circularly polarized luminescence (MCPL) when south (S)-up or north (N)-up direction of the longitudinal external magnetic field of 1.6 T to unpolarized incident light (Faraday geometry) is employed. The |gMCPL| magnitude is on the order of 10–3 T–1 in 374–416 nm. The sign of MCPL is controlled by the S-up and N-up geometry and by the position (1- or 2-) of the hydroxy group.
关键词： magnetic circularly polarized luminescence,pyrene,chirality,fluorescence
更新于2025-09-23 15:21:01
-
Passively Q-switched laser with specific chiral SWCNTs selected by N-CS as saturable absorber at
摘要： The single-wall carbon nanotubes (SWCNTs) with the specific chirality (6, 5) and (7, 5) were sorted out by the density gradient ultracentrifugation (DGU) method. 2D photoluminescence excitation–emission map and the Raman spectrum confirmed the successful chirality-selection. The nonlinear optical performance of the chirality-selected SWCNTs was investigated by an open-aperture Z-scan setup. By employing the prepared SWCNTs saturable absorber (SWCNTs-SA), the minimum pulse duration of 115 ns with a pulse repetition rate of 550 kHz was obtained in the passively Q-switched (PQS) laser operation.
关键词： Q-switching,Chirality selection,Nonlinear optical properties,SWCNTs
更新于2025-09-23 15:21:01
-
[Institution of Engineering and Technology 20th Italian National Conference on Photonic Technologies (Fotonica 2018) - Lecce, Italy (23-25 May 2018)] 20th Italian National Conference on Photonic Technologies (Fotonica 2018) - Second Harmonic Generation Circul Dichroism in Au Coated Gaas-based Nanowires
摘要： Nanostructures with broken symmetry can interact with circularly polarized light to mimic chiroptical (chiral-optical) effects, usually observable in chiral media. This phenomenon is known as extrinsic chirality. Second harmonic generation (SHG) is extremely sensitive to symmetry breaking, down to a single atomic monolayer and it has been extensively used as a probe of extrinsic chirality. Here we present SHG measurements of GaAs nanowires partially covered with Au, fabricated by a self-catalysed technique. The Au coated GaAs nanowires give rise to a dramatic circular dichroism in the generated second harmonic signal, compared to nanowires without coating.
关键词： plasmonic coating,extrinsic chirality,second harmonic generation,GaAs nanowires
更新于2025-09-23 15:21:01
-
The role of plasmonic excitations in the optical activity of periodic structures with configurational chirality
摘要： Broken mirror symmetry of chiral structures imposes a lack of mirror symmetry in the scattering pro?le. When an energy dissipation channel is introduced in the system, an overall optical activity arises. Plasmonic nanostructures, therefore, are an ideal platform to induce optical activity by means of constitutional or con?gurational chirality. We experimentally investigate the mechanism of plasmonically induced con?gurational chirality in a periodic monoclinic hole array with a broken mirror symmetry. The resulting optical activity of the structure is studied by using k-space leakage radiation measurements.
关键词： k-space leakage radiation measurements,plasmonic excitations,periodic structures,optical activity,configurational chirality
更新于2025-09-23 15:21:01
-
Giant circular dichroism of chiral L-shaped nanostructure coupled with achiral nanorod: Anomalous behavior of multipolar and dipolar resonant modes
摘要： Chirality, which has long been known as an intrinsic property of living organisms, has caught the interest of researchers due to the rapid emergence of chiral metamaterials. The chiroptical response of noble metal nanostructures in visible and near-infrared regions has been widely investigated. Herein, we propose a bilayer Ag metastructure, in which a chiral L-shaped nanostructure at the bottom is coupled with an achiral nanorod acquiring different positions in the top layer with respect to the long and/or short arm of the chiral L-shaped nanostructure at the bottom layer. The metastructure generates a giant circular dichroism (CD) signal resulting from the strong coupling of the multipolar and dipolar resonant modes on the two layers, in the visible and near-infrared regions. With changing the position of the achiral nanorod, an unusual reversal of the CD spectra is observed, along with a fourfold increase in CD intensity in the short wavelength range due to the multipolar resonant modes. The position of the achiral nanorod is tailored by the azimuthal angle of the substrate during the fabrication of the metastructure using the oblique angle deposition method. This study provides insights into the variation of the coupling strength between a chiral L-shaped nanostructure and an achiral nanorod. The results can be useful in designing chiral–achiral composite nanoantennas for sensing devices.
关键词： Metamaterials,Circular dichroism,Oblique angle deposition,Plasmonics,Chirality
更新于2025-09-23 15:21:01
-
Guanosine Assembly Enabled Gold Nanorods with Dual Thermo- and Photoswitchable Plasmonic Chiroptical Activity
摘要： Noble metal nanostructures with plasmonic circular dichroism (PCD) have attracted interest and a modulation of PCD is of great importance for their potential applications. Herein, we propose a supramolecular strategy for achieving dual thermal and photo-switchable PCD. When guanosine (G), deoxyguanosine (dG) and boric acid modified achiral gold nanorods (GNRs) were co-assembled into hydrogel, hybrid nanofibers with PCD were produced. When the hydrogel was heated, the nanofiber was disassembled and the PCD disappeared. Since the hydrogel was thermally reversible, a thermo-controlled PCD could be realized. The hybrid hydrogel also showed photo-switchable PCD. When the gel was irradiated with IR laser, the PCD disappeared. It can be restored by placing at room temperature. Moreover, the hybrid gel was selectively response to the circularly polarized light (CPL). For (G/dG)-GNRs hybrid assemblies, the R-CPL irradiation showed higher photothermal efficiency than that of L-CPL, which made it useful for an IR-irradiation controlled release of drug molecules.
关键词： plasmonic chirality,gold nanorods,guanosine,circular polarized light,selective response
更新于2025-09-23 15:21:01
-
Chirality Inversion on the Carbon Dot Surface via Covalent Surface Conjugation of Cyclic α-Amino Acid Capping Agents
摘要： Manipulating the chiroptical properties at the nanoscale is of great importance in stereoselective reactions, enantioseparation, self-assembly, and biological phenomena. In recent years, carbon dots have garnered great attention because of their favorable properties such as tunable fluorescence, high biocompatibility, and facile, scalable synthetic procedures. Herein, we report for the first time the unusual behavior of cyclic amino acids on the surface of carbon dots prepared via microwave-based carbonization. Various amino acids were introduced on the surface of carbon dots via EDC/NHS conjugation at room temperature. Circular dichroism results revealed that although most of the surface conjugated amino acids can preserve their chirality on negatively charged, “bare” carbon dots, the “handedness” of cyclic α-amino acids can be flipped when covalently attached on carbon dots. Moreover, these chiroptical carbon dots were found to interact with the cellular membrane or its mimic in a highly selective manner due to their acquired asymmetric selectivity. A comprehensive inhibitor study was conducted to investigate the pathway of cellular trafficking of these carbon dots. Overall, it was concluded that the chirality of the amino acid on the surface of carbon dots could regulate many of the cellular processes.
关键词： cyclic amino acids,chiroptical properties,chirality inversion,carbon dots,cellular interaction
更新于2025-09-23 15:21:01