Search Results (434)

Mechanical properties of lead-free hybrid perovskites have attracted growing interest because of their significance in future eco-friendly optoelectronic applications. However, there are very limited studies about the intrinsic elastic properties and high-pressure structural evolution of hybrid perovskites, and the fundamental structure–mechanical property relationships are insufficiently understood. Here, we report the elastic behavior of a three-dimensional (3D) hybrid organic–inorganic perovskite, (DABCO)RbBr₃ (DABCO = triethylenediammonium), and confirm the processability through processing with chiral metasurfaces and the generation of circular dichroism. Our in situ high-pressure synchrotron X-ray diffraction experiments demonstrate that this crystal does not start to amorphize until 2.3 GPa. Density functional theory calculations reveal that its E, G and v range between 20.73 and 27.93 GPa, 8.21 and 11.62 GPa and 0.18–0.39, respectively. Additionally, due to the low elastic moduli and polar crystal structure, we fabricate a device of (DABCO)RbBr₃ composite film, which shows favorable performance for piezoelectric energy harvesting. This work utilizes (DABCO)RbBr₃ to open up new avenues for applications in manufacturing and energy harvesting. Full article

Interest in non-centrosymmetric crystalline materials exhibiting second harmonic generation (SHG) has increased due to their potential applications in optical sensing and biosensing. Saccharide-based metal complexes are particularly attractive systems, as chiral sugars can promote non-centrosymmetric crystal packing. In this work, a new lanthanum–β-d-fructose compound, [La(C₆H₁₂O₆)(H₂O)₅]Cl₃ (LaFRUCl), was synthesized using a simple and low-cost method and characterized by single-crystal X-ray diffraction. The compound crystallizes in the orthorhombic space group P2₁2₁2₁ and consists of infinite (La³⁺–fructose)_n chains extending along the [001] direction, forming a one-dimensional Metal–Organic Framework. The nonlinear optical response was evaluated using the Kurtz–Perry powder technique with a Nd:YAG laser (1064 nm) and compared to a sucrose reference. The measured SHG efficiency is comparable to that of previously reported alkaline earth metal–sugar analogs. While the compound’s SHG emission is significant, evaluation of its structural stability under aqueous or physiological conditions is be required before considering biological applications. Full article

Chiral and racemic forms of a pyridyl ligand (R-L and rac-L, respectively), containing urea groups at their core and synthesised by the condensation of 3-aminopyridine and α-methylbenzylisocyante, were incorporated into silver complexes. The resulting species depend on the enantiopurity of the ligand alongside an influence from the counter-anion. The enantiopure ligand generated isomorphous, one-dimensional polymeric compounds [Ag(R-L)X] (where X = NO₃, CF₃SO₃) or [Ag(R-L)]X (where X = BF₄, PF₆). The polymeric chains, connected by N and O coordination of the ligands, have outwards facing urea groups that form hydrogen bonds to the counter-anions, which play little role in determining the overall structure. Despite all syntheses containing an excess of Ag(I) salt, the racemic ligand formed only discrete complexes of [Ag(rac-L)₂]⁺ in the presence of each of the above anions. Three of these complexes contain ligands of the same chirality (i.e., complexes with R,R and S,S ligand pairs within the centrosymmetric structures) with only the PF₆-containing compound being different. The anions play a role in dictating the structure of hydrogen-bonded chains, although PF₆⁻ is unique with urea···urea interactions present between complexes. Overall, this system highlights the nuances associated with predicting the structure, and even speciation, of related chiral/achiral systems in addition to influences of counter-anions on structural motifs. Full article

Recent advances in chiral analytical chemistry have revealed that fermented and natural foods contain substantial amounts of D-amino acids (D-AAs), the mirror-image counterparts of L-amino acids, leading to their recognition as nutraceutical components with potential health relevance. Although clinical evidence provides only limited support for their therapeutic efficacy, commercial expectations have outpaced scientific validation, and recent safety concerns emphasize the need for critical evaluation. In this review, we integrate findings from food chemistry, microbiology, biochemistry, physiology, and clinical research to provide a critical overview of dietary D-AAs. We examine how dietary exposure, microbial metabolism, host clearance capacity, and redox status collectively shape their context-dependent biological effects. We highlight the mechanistic linkage between D-amino acid oxidase (DAAO)-mediated hydrogen peroxide (H₂O₂) generation and organ-specific vulnerability, thereby clarifying the molecular basis of their “double-edged sword” actions. Within this interdisciplinary framework, we propose that D-AAs function as context-dependent “contronymic” molecules in cellular communication. By distinguishing physiological regulation, experimental modulation, and clinical application, this review aims to support evidence-based nutraceutical strategies and safety assessments that harness the potential benefits of D-AAs while minimizing associated risks. Full article

Aldolases are powerful biocatalysts for the stereoselective formation of carbon–carbon bonds and are widely used in the synthesis of chiral intermediates for pharmaceutical applications. Among them, 2-deoxyribose-5-phosphate aldolase (DERA) has been extensively exploited for the preparation of the conserved side chain of statins. In this work, we report a novel chemoenzymatic approach for the synthesis of nucleobase-substituted lactol products as potential precursors of new statin analogues. A C49M variant of DERA from Pectobacterium atrosepticum (PaDERA C49M) was employed to catalyze sequential aldol additions using aldehyde-functionalized nucleobases as non-natural electrophilic substrates. The formation of nucleobase-containing lactols was confirmed, demonstrating for the first time the acceptance of nucleobase-derived aldehydes in DERA-catalyzed aldol reactions. This strategy provides access to structurally novel statin side-chain precursors and expands the synthetic potential of DERA toward the generation of new classes of bioactive compounds. Full article

Many organic fungicides are chiral and are used in diverse application areas, including pharmaceuticals, personal care products, agrochemicals, and industry. Fungicides have valuable effects such as preventing fungal infestations and the treatment of diseases, but their generalized use resulted in their occurrence in diverse environmental compartments which is an increasing environmental concern with negative impact on non-target organisms and human health risks. Besides, enantiomers of chiral fungicides may exhibit distinct bioactivity including toxicity and degradation profiles. Therefore, monitoring their enantioselective occurrence in the environment is essential to accurately assess enantioselective (eco)toxicity and establish environmental quality standard levels. This review provides the first comprehensive and critically interpretative assessment of enantioselective chromatographic methods for the determination of fungicides, with a primary focus on azole compounds, in complex environmental matrices (e.g., soil, sediment, plants, earthworms, sewage sludge, water, wastewater) due to their regulatory relevance in the EU Watch Lists, frequent occurrence in environmental matrices, and specific analytical challenges associated with their chiral nature. Other fungicide classes are also included, since other fungicides (either chiral or achiral) reported in the articles retrieved by the literature search, were also evaluated, integrating methodological, analytical and regulatory dimensions. Liquid chromatography was identified as the predominant analytical technique, with polysaccharide-based chiral stationary phases being the most frequently used, while sample preparation was mainly based on solid-phase extraction and QuEChERS-based approaches for complex environmental matrices. Analytical performance parameters were compared to highlight strengths and limitations of reported methods, while environmental monitoring data were reviewed, identifying soil and water as matrices with the highest reported chiral fungicide levels. The urgent need to develop robust enantioselective analytical methods to recognize the distinctive biological and toxicological properties of individual enantiomers are critically discussed. By revealing persistent gaps in enantioselective workflows and regulatory differentiation between enantiomers, it highlights the need for robust analytical approaches and reliable monitoring strategies to contribute for future enantiomer-specific environmental risk assessment frameworks. Full article

The induction of chirality to obtain enantiopure products of high synthetic value is of great importance across various scientific fields, particularly in the medical area, as it has been demonstrated that the different enantiomers of drugs interact differently with biological receptors. In this context, asymmetric catalysis focuses on the design of catalysts that are easy to synthesize, capable of efficiently and enantioselectively forming C–C bonds, and suitable for reuse in multiple catalytic processes. This work describes the application of a Pd(II) complex coordinated with the R and S forms of proline in direct Aldol, Morita–Baylis–Hillman, and Heck coupling reactions. The catalytic system efficiently promoted the aldol reaction, achieving yields of 80–95%, excellent diastereoselectivities (1:69 syn/anti), and enantiomeric excesses greater than 99%. From a mechanistic perspective, the formation of a transition state is proposed in which a proline molecule generates an enamine that, upon coordination with the metal center, is stabilized through interaction with the intermediate’s double bond. Moreover, the study of the Morita–Baylis–Hillman and Heck coupling reactions highlights the versatility of this type of catalyst. Full article

The synthesis of enantiomerically pure chiral β-nitroalcohols is a crucial objective in asymmetric catalysis. In order to efficiently obtain such chiral products, we developed a series of thermoresponsive, oxazoline–copper catalysts (Cu^II-PN_xFe_yO_z) via sequential reversible addition–fragmentation chain transfer (RAFT) polymerization. These catalysts can self-assemble in water into single-chain nanoparticles (SCNPs) with biomimetic behavior, in which intramolecular hydrophobic and metal-coordination interactions generate a confined hydrophobic cavity. Comprehensive characterization by FT-IR, TEM, DLS, CD, CA, and ICP analysis confirmed the nanostructure and composition. When applied to the aqueous-phase asymmetric Henry reaction between nitromethane and 4-nitrobenzaldehyde, the optimal catalyst (2.0 mol%) achieved a quantitative yield (96%) with excellent enantioselectivity (up to 99%) within 12 h. Furthermore, the thermosensitive poly(N-isopropylacrylamide, NIPAAm) block enabled facile catalyst recovery through temperature-induced precipitation above its lower critical solution temperature (LCST). This work presents an efficient and recyclable biomimetic catalytic system, offering a novel strategy for designing sustainable chiral catalysts for green organic synthesis. Full article

Vertical cavity surface emitting lasers (VCSELs) have shown great potential in high-speed communication, quantum information processing, and 3D sensing due to their excellent beam quality and low power consumption. However, generating high-purity and controllable circularly polarized light usually requires external optical components such as quarter-wave plates, which undoubtedly increases system complexity and volume, hindering chip-level integration. To address this issue, we propose a monolithic integration scheme that directly integrates a custom-designed double-layer asymmetric metasurface onto the upper distributed Bragg reflector of a chiral VCSEL. This metasurface consists of a rotated GaAs elliptical nanocolumn array and an anisotropic grating above it. By precisely controlling the relative orientation between the two, the in-plane symmetry of the structure is effectively broken, introducing a significant optical chirality response at a wavelength of 1550 nm. Numerical simulations show that this structure can achieve a near 100% high reflectivity for the left circularly polarized light (LCP), while suppressing the reflectivity of the right circularly polarized light (RCP) to approximately 33%, thereby obtaining an efficient in-cavity circular polarization selection function. Based on this, the proposed VCSEL can directly emit high-purity RCP without any external polarization control components. This compact circularly polarized laser source provides a key solution for achieving the next generation of highly integrated photonic chips and will have a profound impact on frontier fields such as spin optics, secure communication, and chip-level quantum light sources. Full article

The development of nanoscale chiral materials with enhanced optical properties holds significant promise for advancing technologies in light-emitting devices and enantioselective sensing. Here, we report the self-assembly of chiral metal–organic cages from an axially chiral, AIE-active binaphthyl dicarboxylate ligand. This supramolecular architecture functions as a multifunctional platform, demonstrating a high affinity for anionic guests through synergistic electrostatic and hydrogen-bonding interactions. The rigid cage framework not only enhances the ligand’s intrinsic aggregation-induced emission (AIE) but also serves as a highly effective chiral amplifier. Notably, MOCs significantly boost the circularly polarized luminescence (CPL), achieving a luminescence dissymmetry factor (|g_lum|) of 1.2 × 10⁻³. This value represents an approximately five-fold enhancement over that of the unassembled ligand. The photophysical properties of this chiral supramolecular system provide a strategic blueprint for designing next-generation optical nanomaterials. Full article

Two-dimensional ferromagnets are promising for compact spintronic devices. However, their centrosymmetric structure inherently suppresses the Dzyaloshinskii–Moriya interaction (DMI), hindering the stabilization of chiral spin texture. Here, a tunable DMI induced by interface symmetry breaking in Fe₃GeTe₂/MoS₂ vdW heterostructures is reported. We find that the interfacial DMI stabilizes Néel-type skyrmions in Fe₃GeTe₂/MoS₂ heterostructures under zero magnetic field, with nucleation observed at 64 Oe and annihilation at 800 Oe via Lorentz transmission electron microscopy (LTEM). Skyrmion density peaks (~0.57 skyrmions/μm²) at a Fe₃GeTe₂ thickness of ~30 nm and decays beyond ~60 nm, indicating a finite penetration depth of the proximity effect. Such modulated DMI enables a stabilized nucleation of Néel type skyrmions, allowing for precise control over their density, revealed by Lorentz transmission electron microscopy. Thickness-dependent measurements confirm the interfacial origin of this stabilization. Skyrmion density reaches peak in thin Fe₃GeTe₂ layers and decays beyond ~60 nm, defining the finite penetration depth of the proximity effect. Micromagnetic simulations reproduce the field-dependent evolution of skyrmions, showing a strong correlation to interfacial DMI. First-principles calculations attribute this DMI to asymmetric charge redistribution and spin–orbit coupling at the heterointerface. This work establishes interface engineering as a universal strategy for stabilizing skyrmions in centrosymmetric vdW ferromagnets, offering a thickness-tunable platform for next-generation two-dimensional spintronic devices. Full article

Homogeneous Kolbe-Schmitt carboxylation of phenoxides offers a mild and effective alternative to the classical high-temperature solid-phase Kolbe-Schmitt reaction. To develop this into a practical synthetic approach, we investigated several fundamental dependencies, particularly the impact of cations (Na, K, Li, Cs, and Rb), phenoxide concentration, and solvents (DMSO or DMF) on the yield and regioisomeric ratio of hydroxyaromatic carboxylic acids (HACAs). We identified optimal conditions for the effective carboxylation of different phenoxides, including a chiral Ellman’s sulfinamide derived from ortho-vanillin. Both solvents and cations were found to be crucial in the carboxylation of phenoxides. Due to solvation effects, DMSO directs CO₂ attack to the para-position of phenoxide, while DMF, although less selective, generally affords higher HACA yields. The addition of equiv. amounts of mesitolate salt to phenoxide in either DMSO or DMF solution often drives the reaction to completion, resulting in yields of up to 98%. Phenoxides containing several EWG groups, such as halogens or alkyl groups, adjacent to the reaction center show considerably lower reactivity in carboxylation; however, by carefully adjusting parameters, acceptable conversions (>70%) can be achieved. Using the gasometry, we assessed the stability of phenoxide and mesitolate carbonate complexes in DMSO. These experiments revealed distinct stages for the onset of decomposition and carboxylation at atmospheric pressure, indicating a lower energy barrier in the homogeneous process. Further insight into carbonate complex behavior was obtained through DOSY and ¹³C NMR experiments, which support increased molecular association in solution and correlate with enhanced reactivity. Full article

The mechanism of generation of products with opposite handedness in the reactions of heterocyclic aldehydes with diallylboronates was studied by NMR experiments and DFT computations. The origin of this unusual phenomenon is a competition between monomeric and dimeric autoinductors that promote the formation of opposite enantiomers. Thus, NMR data suggest that racemic alcohol 3a, upon dimerization, provides almost exclusively the heterochiral dimeric boronate 5a(RS). This corresponds to the computed results predicting strongly exergonic dimerization with ΔΔG²⁹⁸ −6.5 kcal/mol. Dimerization of the chiral boronate 3a (R) with 82% ee yields 5a (RS) in which all available 3a(S) is bound. As a result, 3 species remain in the solution: (1) 5a(RS), producing a newly formed racemic product in the reaction with 1a, (2) 3a(R), reacting with 1a and yielding an R-configured newly formed product, and (3) 5a(RR), yielding selectively S-configured newly formed product according to computations. Taking into account the equilibria existing between monomers and dimers, the system is capable of demonstrating the experimentally observed random handedness of the newly formed product. Full article

We theoretically investigate multiple-Q instabilities in centrosymmetric hexagonal magnets, formulated as superpositions of independent six ordering wave vectors related by sixfold rotational and mirror symmetries. By employing a spin model that incorporates biquadratic interactions and an external magnetic field, we establish a comprehensive low-temperature phase diagram hosting single-Q, double-Q, triple-Q, and sextuple-Q states, as well as skyrmion crystals with topological charges of one and two. The field evolution of the magnetization, scalar spin chirality, and finite wave-vector magnetic amplitudes reveals a hierarchical buildup of multiple-Q order, accompanied by first-order transitions between topologically distinct and trivial phases. At large biquadratic coupling, all six symmetry-related ordering wave vectors coherently participate, giving rise to two sextuple-Q states under magnetic fields and to another spontaneous sextuple-Q state even at zero field. The latter zero-field sextuple-Q state represents a fully developed sixfold interference pattern stabilized solely by the biquadratic interaction, characterized by alternating skyrmion- and antiskyrmion-like cores with vanishing uniform scalar spin chirality. These findings establish a unified framework for understanding hierarchical multiple-Q ordering and demonstrate that the interplay between bilinear and biquadratic interactions under hexagonal symmetry provides a generic route to complex noncoplanar magnetism in centrosymmetric itinerant systems. Full article

We review recent applications of nonlocal effective field theory, particularly focusing on nonlocal chiral effective theory and nonlocal quantum electrodynamics (QED), as well as an extension of nonlocal effective theory to curved spacetime. For the chiral effective theory, we discuss the calculation of generalized parton distributions (GPDs) of the nucleon at nonzero skewness, along with the corresponding gravitational (or mechanical) form factors, within the convolution framework. In the QED application, we extend the nonlocal formulation to construct the most general nonlocal QED interaction, in which both the propagator and fundamental QED vertex are modified due to the nonlocal Lagrangian, while preserving the Ward–Green–Takahashi identities. For consistency with the modified propagator, a solid quantization is proposed, and the nonlocal QED is applied to explain the lepton $g-2$ anomalies without the introduction of new particles beyond the standard model. Finally, with an extension of the chiral effective action to curved spacetime, we investigate the nonlocal energy–momentum tensor and gravitational form factors of the nucleon with a nonlocal pion–nucleon interaction. Full article