X-ray circular dichroism, arising from the contrast in X-ray absorption between opposite photon helicities, serves as a spectroscopic tool to measure the magnetization of ferromagnetic materials and identify the handedness of chiral crystals. Antiferromagnets with crystallographic chirality typically lack X-ray magnetic circular dichroism because of time-reversal symmetry, yet exhibit weak X-ray natural circular dichroism. Here, the observation of giant natural circular dichroism in the Ni L3-edge X-ray absorption of Ni3TeO6 is reported, a polar and chiral antiferromagnet with effective time-reversal symmetry. To unravel this intriguing phenomenon, a phenomenological model is proposed that classifies the movement of photons in a chiral crystal within the same symmetry class as that of a magnetic field. The coupling of X-ray polarization with the induced magnetization yields giant X-ray natural circular dichroism, revealing typical ferromagnetic behaviors allowed by the symmetry in an antiferromagnet, i.e., the altermagnetism of Ni3TeO6. The findings provide evidence for the interplay between magnetism and crystal chirality in natural optical activity. Additionally, the first example of a new class of magnetic materials exhibiting circular dichroism is established with time-reversal symmetry. 相似文献
The direct synthesis of chiroptical organic–inorganic methylammonium lead bromide perovskite nanoplatelets that are passivated by R‐ or S‐phenylethylammonium ligands is reported. The circular dichroism spectra can be divided into two components: (1) a region associated with a charge transfer transition between the ligand and the nanoplatelet, 300–350 nm, and (2) a region corresponding to the excitonic absorption maximum of the perovskite, 400–450 nm. The temperature‐ and concentration‐dependent circular dichroism spectra indicate that the chiro‐optical response arises from chiral imprinting by the ligand on the electronic states of the quantum‐confined perovskite rather than chiral ligand‐induced stereoselective aggregation. 相似文献
Determining the structural chirality of biomolecules is of vital importance in bioscience and biomedicine. Conventional methods for characterizing molecular chirality, e.g., circular dichroism (CD) spectroscopy, require high-concentration specimens due to the weak electronic CD signals of biomolecules such as amino acids. Artificially designed chiral plasmonic metastructures exhibit strong intrinsic chirality. However, the significant size mismatch between metastructures and biomolecules makes the former unsuitable for chirality-recognition-based molecular discrimination. Fortunately, constructing metallic architectures through molecular self-assembly allows chirality transfer from sub-nanometer biomolecules to sub-micrometer, intrinsically achiral plasmonic metastructures by means of either near-field interaction or chirality inheritance, resulting in hybrid systems with CD signals orders of magnitude larger than that of pristine biomolecules. This exotic property provides a new means to determine molecular chirality at extremely low concentrations (ideally at the single-molecule level). Herein, three strategies of chirality transfer from sub-nanometer biomolecules to sub-micrometer metallic metastructures are analyzed. The physiochemical mechanisms responsible for chirality transfer are elaborated and new fascinating opportunities for employing plasmonic metastructures in chirality-based biosensing and bioimaging are outlined. 相似文献
Bulk metals lack chirality. Recently, metals have been sculptured with metastable chirality varying from the micro‐ to nano‐scale. The manipulation of molecular chirality could be novelly performed using metals composed of chiral lattices at atomic scales (i.e., chiral nanoparticles or CNPs) if one could fundamentally understand the interactions between molecules and the chiral metal lattices. The incorporation of chiral ligands has been generally adapted to form metal CNPs. However, post‐fabrication removal of chiral ligands usually causes relaxation of the metastable chiral lattices to thermodynamically stable achiral structures, and thus the coexisting chiral ligands will unavoidably disturb or screen the interactions of interest. Herein, a concept of metal CNPs that are free of chiral ligands and consist of atomically chiral lattices is introduced. Without chiral ligands, shear forces applied by substrate rotation along with the translation of incident atoms lead to imposing the metastable chiral lattices onto metals. Metal CNPs show not only the chiroptical effect but the enantiospecific interactions of chiral lattices and molecules. These two unique chiral effects have resulted in the applications of enantiodifferentiation and asymmetric synthesis. Prospectively, the extension in composition space and constituent engineering will apply alloy CNPs to enantiodiscrimination, enantioseperation, bio‐imaging, bio‐sensing, and asymmetric catalysis. 相似文献
In recent years, optical chirality of plasmonic nanostructures has aroused great interest because of innovative fundamental understanding as well as promising potential applications in optics, catalysis and sensing. Herein, state‐of‐the‐art studies on circular dichroism (CD) characteristics of plasmonic nanostructures are summarized. The hybrid of achiral plasmonic nanoparticles (NPs) and chiral molecules is explored to generate a new CD response at the plasmon resonance as well as the enhanced CD intensity of chiral molecules in the UV region, owing to the Coulomb static and dynamic dipole interactions between plasmonic NPs and chiral molecules. As for chiral assembly of plasmonic NPs, plasmon–plasmon interactions between the building blocks are found to induce generation of intense CD response at the plasmon resonance. Three‐dimensional periodical arrangement of plasmonic NPs into macroscale chiral metamaterials is further introduced from the perspective of negative refraction and photonic bandgap. A strong CD signal is also discerned in achiral planar plasmonic nanostructures under illumination of circular polarized plane wave at oblique incidence or input vortex beam at normal incidence. Finally perspectives, especially on future investigation of time‐resolved CD responses, are presented. 相似文献
Site-selective chiral growth of anisotropic nanoparticles is of great importance to realize the plasmonic nanostructures with delicate geometry and desired optical chirality; however, it remains largely unexplored. This work demonstrates a controlled site-selective chiral growth system based on the seed-mediated growth of anisotropic Au triangular nanoplates. The site-selective chiral growth involves two distinct underlying pathways, faceted growth and island growth, which are interswitchable upon maneuvering the interplay of chiral molecules, surfactants, and reducing agents. The pathway switch governs the geometric and chirality evolution of Au triangular nanoplates, giving rise to tailorable circular dichroism spectra. The ability to tune the optical chirality in a controlled manner by manipulating the site-selective chiral growth pathway opens up a promising strategy for exploiting chiral metamaterials with increasing architectural complexity in chiroptical applications. 相似文献
Generation of circular dichroism （CD） beyond the UV region is of great interest in developing chiral sensors and chiroptical devices. Herein, we demonstrate a simple and versatile method for fabrication of plasmonic oligomers with strong CD response in the visible and near IR spectral range. The oligomers were fabricated by triggering the side-by-side assembly of cysteine-modified gold nanorods. The modified nanorods themselves did not exhibit obvious plasmonic CD signals; however, the oligomers show strong CD bands around the plasmon resonance wavelength. The sign of the CD band was dictated by the chirality of the absorbed cysteine molecules. By adjusting the size of the oligomers, the concentration of chiral molecules, and/or the aspect ratio of the nanorods, the CD intensity and spectral range were readily tunable. Theoretical calculations suggested that CD of the oligomers originated from a slight twist of adjacent nanorods within the oligomer. Therefore, we propose that the adsorbed chiral molecules are able to manipulate the twist angles between the nanorods and thus modulate the CD response of the oligomers. 相似文献
Interest in chiral substances has mainly focused on the substances themselves, but not on the accompanying space, especially regarding the pore alignment. As a method to form both the chiral substance and the accompanying space, cylindrical self‐assembly of uniform polystyrene nanoparticles with fructose is carried out in the presence of both carbon and sodium alginate, which is followed by heat treatment in an inert atmosphere. The carbonization generates fructose‐derived honeycomb‐like carbon walls with helically aligned nanopores left after the polystyrene decomposition. The diffuse reflectance circular dichroism measurements give peaks with opposite signs for the d ‐ and l ‐fructose‐derived cylindrical carbons. Circularly polarized light sensitivity in transient photoconductivity is confirmed apparently in the carbon‐based helical structures. This sensitivity as well as straightforward formation of composites with another component to give helicity shows potential applications of the helically aligned pores. 相似文献
Chiral nano-assemblies with amplified optical activity have attracted particular interest for their potential application in photonics, sensing and catalysis. Yet it still remains a great challenge to realize their real applications because of the instability of these assembled nanostructures. Herein, we demonstrate a facile and efficient method to fabricate ultra-stable chiral nanostructures with strong chiroptical properties. In these novel chiral nanostructures, side-by-side assembly of chiral cysteine-modified gold nanorods serves as the core while mesoporous silica acts as the shell. The chiral core–shell nanostructures exhibit an evident plasmonic circular dichroism (CD) response originating from the chiral core. Impressively, such plasmonic CD signals can be easily manipulated by changing the number as well as the aspect ratio of Au nanorods in the assemblies located at the core. In addition, because of the stabilization effect of silica shells, the chiroptical performance of these core–shell nanostructures is significantly improved in different chemical environments.
In this paper, a gammadion stereo-structure (GSS) chiral metamaterial (CMM) is described and numerically analysed at optical frequencies. The influence of the geometry of the proposed CMM on the optical properties was studied systematically. The numerical simulations exhibit that the giant circular dichroism (CD) effect, optical activity and negative refraction can be obtained by properly selecting the geometric parameters, respectively. Given the pronounced optical effects and the negative refraction property of stereo-structure CMM, many applications in ultra-compact polarization components, integrated photonics, plasmonic-enhanced sensing of biochemical substances and CD spectroscopic analysis can be envisioned easily. 相似文献
Halide perovskites have emerged as a type of extremely promising material for their diverse chemical and electronic structures along with their brilliant optoelectronic properties. The introduction of chirality into perovskite scaffolds, generating a novel concept of chiral perovskite materials, offers an immense step forward toward the development of smart optoelectronic and spintronic materials and devices. The present Review summarizes recent advances in such an emerging field regarding the design and construction of chiral perovskite materials, along with their optoelectronic performances. In addition, an outlook of future challenges as well as the potential significance of the chiral perovskite family on the optical communication is proposed. 相似文献
