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Universality of photoelectron circular dichroism in the photoionization of chiral molecules
摘要： Photoionization of chiral molecules by circularly polarized radiation gives rise to a strong forward/backward asymmetry in the photoelectron angular distribution, referred to as photoelectron circular dichroism (PECD). Here we show that PECD is a universal effect that reveals the inherent chirality of the target in all ionization regimes: single photon, multiphoton, above-threshold and tunnel ionization. These different regimes provide complementary spectroscopic information at electronic and vibrational levels. The universality of the PECD can be understood in terms of a classical picture of the ionizing process, in which electron scattering on the chiral potential under the influence of a circularly polarized electric field results in a strong forward/backward asymmetry.
关键词： strong fields,photoelectron circular dichroism,chirality,multiphoton ionization
更新于2025-09-09 09:28:46
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Chirality-Based Biosensors
摘要： The fabrication of chiral nanostructures gives rise to characteristic chiroptical activity, which can be used for chirality-based biosensors. Great progress is made in the use of nanoassemblies for the construction of chiral nanoparticle dimers, pyramids, helices, and twisted structures, and their chiroptical activities correlate with diverse structural geometries and enantiomeric configurations. In DNA-hybridization-based chiral nanoassemblies, the assembly parameters, such as the components, gaps, multicomponents, and the aftergrowth of metal, can result in multiple bands and enhanced chiroptical effects. Based on known chiral nanostructures, the existing chiral nanoassembly-based biosensors together with their targets and signal amplification strategies are reviewed. Chirality involves multiple signals, and multitarget biosensors are introduced with newly developed chiral architectures for the accurate and reliable monitoring of biomarkers in living cells. The interactions between chiral nanoarchitectures and biosystems are also highlighted, which are important not only in the chiral dynamic switching of nano-objects for biomonitoring, but also in manipulating cell growth, proliferation, and adhesion. The future perspectives on chiral fabrication and its use in biosensors are also comprehensively discussed.
关键词： chirality,biosensors
更新于2025-09-09 09:28:46
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External Reversal of Chirality Transfer in Photoswitches
摘要： The transfer of stereoinformation is at the heart of asymmetric reactions. By incorporating the natural monoterpene L-menthone into the backbone of a diarylethene, we could achieve efficient chirality transfer upon photocyclization resulting in the preferred formation of one major closed isomer in a diastereomeric ratio (dr) of 85 : 15. More significantly, we were able to completely reverse the diastereomeric outcome of the ring-closure, simply by altering the chemical environment or the irradiation conditions. As a result, we could selectively accumulate the less favored minor closed isomer, with remarkable dr values of > 99 : 1 and 74 : 26, respectively. Computations reveal that a stability inversion after photocyclization is the basis for the observed unprecedented control over diastereoselectivity.
关键词： diarylethenes,diastereoselectivity,electrocyclization,chirality,photochromism
更新于2025-09-09 09:28:46
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Imaging cellular ultrastructures using expansion microscopy (U-ExM)
摘要： Determining the structure and composition of macromolecular assemblies is a major challenge in biology. Here we describe ultrastructure expansion microscopy (U-ExM), an extension of expansion microscopy that allows the visualization of preserved ultrastructures by optical microscopy. This method allows for near-native expansion of diverse structures in vitro and in cells; when combined with super-resolution microscopy, it unveiled details of ultrastructural organization, such as centriolar chirality, that could otherwise be observed only by electron microscopy.
关键词： centriolar chirality,U-ExM,electron microscopy,super-resolution microscopy,ultrastructure expansion microscopy
更新于2025-09-09 09:28:46
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Charge‐Induced Shifts in Chiral Surface Plasmon Modes in Gold Nanorod Assemblies
摘要： A detailed investigation of the effect of electron injection on the chiral plasmon modes of helical nanorod assemblies is presented. An increased surface plasmon frequency of the electron gas due to the addition of electrons leads to a blue-shift in the corresponding chiral surface plasmon modes. The mechanism behind the shift in plasmonic chirality due to nanorod charging is investigated using theoretical simulations. Charging of the nanorods alters the surface electron density, thereby modifying the plasma frequency and causing a change in the dielectric function. The nature of the plasmon shift and the intensity of chiral surface plasmons are found to be largely dependent on the extent of electron addition. At extended periods of time, the blue shifted band slowly shifts back toward the red, due to transfer of electrons back to the medium, leading to discharging of the nanorods.
关键词： charging effects,plasmonic chirality,electromagnetic modeling,Au nanorods,amyloid fibers
更新于2025-09-04 15:30:14
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Synthesis, structural characterization and photophysical properties of 7-cyanohexahelicene
摘要： 7-Cyanoexahelicene has been prepared in racemic form through a short photochemical synthetic approach and its enantiomeric separation was studied and allowed to obtain (P)- and (M)-enantiomers in 100% ee and > 98.5% ee, respectively. The optical rotatory dispersion and electronic circular dichroism (ECD) spectra of the resolved ones were measured. Other optical properties such as UV and photoluminescence as well as the electrochemical behavior were also examined in solutions.
关键词： Optical resolution,Chirality,Couplings,Photophysical properties,gap energy,Helicenes,Photooxidation
更新于2025-09-04 15:30:14
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Chirality‐Assisted High‐Efficiency Metasurfaces with Independent Control of Phase, Amplitude, and Polarization
摘要： Simultaneously independent control of phase, amplitude, and polarization is pivotal yet challenging for manipulating electromagnetic waves by transmissive metasurfaces. Huygens’ metasurface affords a high-efficiency recipe primarily by engineering phase-only meta-atoms, restricting itself from realizing unprecedentedly complex functions of the transmission beam. Here, a 3D chirality-assisted metasurface concept relying on integrated magnetoelectric meta-atoms is proposed. It empowers the completely decoupled and arbitrary control of phase and amplitude at large incident angles and arbitrary polarizations. This strategy thus facilitates very sophisticated beam manipulations at close-to-unity cross-polarized efficiency via trilayer integrated resonators with mutual twist. The prescribed phase coverage can be determined by geometrical footprints of the unit cell, while the global azimuthal twist unlocks the capability of tuning amplitudes without affecting the phase. The concept and significance of it are validated to implement several proof-of-prototype demanding functionalities by thin metasurfaces of λo/12, which generate self-accelerating diffraction-free Airy beams, lateral and axial dual focusing, and even specific multiplexed beam shaping, respectively. This finding opens up an alternative way in very fine control of light with minimalist complexity and advanced performance. It can stimulate novel and high-performance versatile photonic metadevices, thanks to the fully independent control of phase, amplitude, and polarization.
关键词： decoupling,self-accelerating beams,wavefront control,chirality-assisted metasurface
更新于2025-09-04 15:30:14
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Organization of Twisting Lamellar Crystals in Birefringent Banded Polymer Spherulites: A Mini-Review
摘要： In this mini-review, we summarize the evidences of lamellar twisting in the birefringent banded polymer spherulites demonstrated by various characterization techniques, such as polarized optical microscopy, real-time atomic force microscopy, micro-focus wide angle X-ray diffraction, etc. The real-time observation of lamellar growth under atomic force microscopy unveiled the fine details of lamellar twisting and branching in the banded spherulites of poly(R-3-hydroxybutyrate-co-17 mol % R-3-hydroxyhexanoate). Organization of the twisting lamellar crystals in the banded spherulites was revealed as well. The lamellar crystals change the orientation via twisting rather than the macro screw dislocations. In fact, macro screw dislocation provides the mechanism of synchronous twisting of neighboring lamellar crystals. The driving force of lamellar twisting is attributed to the anisotropic and unbalanced surface stresses. Besides molecular chirality, variation of the growth axis and the chemical groups on lamellar surface can change the distribution of the surface stresses, and thus may invert the handedness of lamellar twisting. Thus, based on both experimental results and physical reasoning, the relation between crystal chirality and chemical molecular structures has been suggested, via the bridge of the distribution of surface stresses. The factors affecting band spacing are briefly discussed. Some remaining questions and the perspective of the topic are highlighted.
关键词： banded polymer spherulite,chirality,ringed spherulite,organization of lamellar crystals,surface stresses,lamellar twisting
更新于2025-09-04 15:30:14
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Chiroptical Protocol for the Absolute Configurational Assignment of Alkyl-Substituted Epoxides Using Bis(zinc porphyrin) as a CD-Sensitive Bidentate Host
摘要： The absolute configurations of simple alkyl-substituted chiral epoxides not bearing other ligating groups are readily determined via the exciton-coupled circular dichroism (ECCD) protocol using a bidentate bis(zinc porphyrin) host system BP1 as a CD-sensitive chirality probe. In this situation, chiral epoxides can successfully be incorporated into the cleft of the V-shaped host BP1 by double coordination of both oxygen lone pairs of the guest to the two central zinc ions of the host. We also propose a working model based on an MM2 optimized structure of the substrates that enables nonempirical prediction of the chirality of the bound epoxide.
关键词： chirality probe,alkyl-substituted epoxides,bis(zinc porphyrin),absolute configurations,exciton-coupled circular dichroism
更新于2025-09-04 15:30:14