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• The paper discusses the significant challenge in analytical chemistry of determining chirality in solid materials using electron paramagnetic resonance (EPR) spectroscopy. • The paper introduces a novel approach using electron paramagnetic resonance (EPR) spectroscopy on chiral crystals doped with Cu2+ ions to determine chirality of crystals. • The method is demonstrated using l - and DL-Histidine crystals doped with Cu2+, showing promising results in accurately determining chirality and enantiomeric composition. • This work provides an initial example of this technique and envisions its potential application to various other chiral organic crystal systems in the future. One of the most challenging tasks in analytical chemistry is the determination of the chirality (identification of an enantiomeric composition) in solids mainly because of the strict requirements of the pharmaceutical industry for enantiomerically pure drugs. Although there are a few methods available to accomplish enantio‑differentiation in solids, for example: X-ray diffraction (XRD), Thermogravimetric analysis (TGA), CD spectroscopy, and low-frequency (LF) Raman spectroscopy, this is still very challenging. In this work, we have developed a new method to measure the chirality of crystals, based on electron paramagnetic resonance (EPR) spectroscopy of chiral crystals doped with Cu2+ as the EPR active ion. Here, we demonstrate our approach using a model system of l - and DL-Histidine crystals doped with Cu2+. We show that EPR measurements of the Cu2+-doped Histidine crystals can accurately determine the chirality and enantiomeric composition of the crystals. We present a very preliminary example of this technique, and we hope that in the future it will be possible to refine and develop this method for many other chiral organic crystal systems. [Display omitted] [ABSTRACT FROM AUTHOR]

This paper presents a continuum-molecular formulation for bi-dimensional micropolar media within the mathematical formalism of a revised peridynamic theory with oriented material points. A variational procedure is considered to derive the fundamental governing equations of the model, which postulates that material points interact through pair potentials allowing generalized pairwise actions to be derived as energy conjugates to properly defined pairwise deformation measures. While continuity of mass is assumed, constitutive laws are produced for long-range micro-interactions to reproduce the effective behavior of the material at the macro-scale. The definition of proper micromoduli functions respecting material symmetries and invariance properties allows then to obtain a non-local micropolar continuum based on pseudo-discrete kinematics, while providing a mechanism-based description of material anisotropy and coupling behaviors uncovered by classical elasticity. An analytic micro-macro moduli correspondence procedure is also established, based on the formal analogy with the constitutive tensor of centrosymmetric planar micropolar continua. As an important result of this research, we show that distinctive chiral effects of micropolar elasticity can be reproduced by introducing a directional independent pseudo-scalar pair potential, which turns out to be analytically vanishing when the rotationally invariant part of the corresponding continuum elastic tensor is invariant to mirror reflections as well. Moreover, the proposed formulation demonstrates sensitivity to elastic bending size-effect as specific property of structured materials homogenized as micropolar continua, and related to the characteristic length of their underlying microstructure. The resulting constitutive non-locality, which plays an important role in fracture problems, is conceptually separated with respect to the intrinsic non-local character of the model related to the integral nature of its governing equations, and then does not vanish when the horizon reduces to zero. The theoretical findings and the effectiveness of the model are successfully verified through illustrative examples referred to representative cases of structured materials homogenized as micropolar continua, including length-scale dependent quasi-static crack propagation as well as the mechanism-based description of the coupling between bulk strain and micro-rotation in elastic bi-dimensional homogenized chiral lattices. • Continuum-molecular formulation for bi-dimensional micropolar elasticity. • Mechanism-based description of material anisotropy and chiral properties. • All the symmetry classes of centrosymmetric 2D micropolar elasticity are covered. • Sensitivity to bending size-effect in microstructured solids is shown. • Analogies between continuum-molecular models and periodic lattice-like materials. [ABSTRACT FROM AUTHOR]

• Three pairs of chiral binaphthyl based macrocyclic tetraphenylethylenes (TPEs) with flexible macrocycle backbones and different linkage lengths were designed and synthesized. • The homochiral helical orientations of TPEs in the crystal structures demonstrate the successful chirality transfer from chiral binaphthyl to TPE via the soft macrocycle backbone. • Obvious aggregation-induced emission (AIE) and CPL properties can be detected owing to the chiral macrocyclic architectures. • The chiral macrocycle with the longest linkage length can produce the largest aggregation-induced circularly polarized luminescence (AI-CPL) signals in films with luminescence dissymmetry factor (g lum) up to 1.9 × 10−3. Developing chiral macrocycles with intense circularly polarized luminescence (CPL) has received considerable interest. The chirality transfer in the chiral macrocycles with separated chiral sources and luminophores is crucial but rarely explored. In this paper, we designed and synthesized three pairs of chiral binaphthyl based macrocyclic tetraphenylethylenes (TPEs) with flexible macrocycle backbones and different linkage lengths. The homochiral helical orientations of TPEs in the crystal structures demonstrate the successful chirality transfer from chiral binaphthyl to TPE via the soft macrocycle backbone. Obvious aggregation-induced emission (AIE) and CPL properties can be detected owing to the chiral macrocyclic architectures. Most importantly, the chiral macrocycle with the longest linkage length can produce the largest aggregation-induced circularly polarized luminescence (AI-CPL) signals in films with luminescence dissymmetry factor (g lum) up to 1.9 × 10−3. [Display omitted] [ABSTRACT FROM AUTHOR]

Plasmonic dimer metamaterials have been widely utilized in the study of chiral nanophotonics due to their special chiroptical properties. The chiroptical properties of simple rod-like dimer metamaterials can be intuitively described by the Born–Kuhn (BK) model, in which the coupling parameter between oscillators is commonly used as a constant. However, the BK model is limited for complex dimer metamaterials because the behavior of the oscillators is constrained by the geometry of the structure. In this paper, inspired by equivalent LC-coupled circuits, we develop the BK model to predict the chiroptical properties of the split-ring resonator (SRR) dimer metamaterials, where the coupling of oscillators depends on both the twist angle of the SRR dimers and the frequency of the incident light. Using the extended BK model, we predict that there exists a special twist angle, which will cause the chirality of the SRR dimer metamaterials to reverse. More importantly, in such specific spatial configurations, the SRR dimer metamaterials with rectangular slits not only retain the enhancement of the chiral near-field, but also limit the chiroptical far-field response because the interactions of electricity and magnetism cancel each other out. In addition, combined with simulation calculations, we find that the rectangular SRR dimer metamaterials have strong robustness within a certain range of structural regulation. Our work will be helpful for the design and optimization of optical logic elements, chiral sensor components, and coding devices. • Analytical expression describes the chirality of the split-ring dimers. • Specific twist angle of the dimers causes the chirality to reverse. • The designed dimers process robustness against geometric perturbations. [ABSTRACT FROM AUTHOR]

• Amino acid modified wood solves the disadvantage of high cost and difficult separation of chiral catalysis. • Wood natural tertiary channels are fully utilized to enhance mass flow and promote catalytic reactions. • The stable bonding of amino acids not only improves performance, but also prolongs the lifetime of the catalyst. Molecular sieve catalysts have been adopted in chiral catalytic reactions due to their high specific surface area, nano-scaled pores and effective separation, however, the problems like low utilization ratio of channels, difficult modification, long period and complex preparation, and no economic benefits reduce its widely application. In this paper, natural wood was employed as raw material to preserve the cellulose skeleton rich in poly‑hydroxyl and the multistage porous channels of nanometer, micron and millimeter by simple treatment. A low-cost, high-yield and high-selectivity chiral catalyst could be obtained from wood with chiral catalytic sites. The in situ grafting method retains the well-developed multistage pore structure of wood, enhances the mass transfer and possesses universal applicability to different aldol condensation reactions. The asymmetric reaction of cyclohexanone and p-nitrobenzaldehyde is catalyzed by grafting readily available amino acids such as threonine, with a yield of 82% and selectivity of 57%. Molecular sieve-like wood possesses the advantages of low economic cost and good catalytic performance, which provides a potential possibility to replace traditional molecular sieve catalyst. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • The optical properties of carbon nanobelts with zigzag and armchair edges, as well as interlocked carbon nanobelts for chirality. • TPA and ECD techniques can effectively differentiate carbon nanoribbons with different boundaries, revealing their relationship and distinguishing features. • The better comprehension of carbon nanoribbons, mechanically interlocked molecules, and chirality. This paper presents a theoretical study on the optical properties of carbon nanobelts with zigzag and armchair edges, as well as interlocked carbon nanobelts for chirality. The results demonstrate that two photon absorption (TPA) and electronic circular dichroism (ECD) techniques can effectively differentiate carbon nanoribbons with different boundaries, revealing their relationship and distinguishing features. The findings from this research contribute to a better comprehension of carbon nanoribbons, mechanically interlocked molecules, and chirality. [ABSTRACT FROM AUTHOR]