Chiral Properties Research Articles

A New Benzyl Phenethanolamine-β-Cyclodextrin Bonded Phase: Chiral Chromatography Performance and Application for LC-MS/MS Analysis of Pesticide Enantiomers in Fruits and Vegetables.

At present, the research on achiral drug and pesticide residue detection methods is still the mainstay at home and abroad, and there is still a lack of systematic research on the enantiomeric analysis of chiral drugs and pesticides. In order to prepare a novel chiral stationary phase, whose "multi-mode" chiral separation chromatographic performance and its utility was verified. An S-(-)-2-benzylamino-1-phenylethanol mono-derivative β-cyclodextrin bonded stationary phase (BzCSP) was prepared based on the "thiol-ene" addition reaction. The chiral compounds including four types of chiral compounds were used as "probes," and their chiral chromatographic properties were evaluated. Furthermore, a new LC-MS/MS method for the determination of the enantiomeric residues of three chiral pesticides in five kinds of fruits and vegetables was established. The study found that the novel stationary phase was suitable for a variety of chromatographic modes (normal phase mode, reversed-phase mode, polar organic mode). The resolutions of hexaconazole (Hex), tebuconazole (Teb), and triticonazole (Trit) enantiomers could be up to 2.31, 1.68, and 1.48, respectively, within 30 min under reversed-phase chromatography. Based on the optimal chromatographic and mass spectrum conditions, a new LC-MS/MS quantitative method for the Hex, Teb, and Trit enantiomers was established by multi-reaction positive ion monitoring (MRM). The detection limits (LODs) of enantiomers were less than 0.89 µg/kg for Hex, 0.93 µg/kg for Teb, and 0.93 µg/kg for Trit, and the averaged recoveries of enantiomers were in the range of 75.8-106.3% for Hex, 77.4-116.3% for Teb, and 78.7-113.4% for Trit. The method had good reproducibility with the RSDs (<5%) for intraday and (<7%) for interday. The established method had the characteristics of good selectivity, high sensitivity, strong resistance to matrix interference, and good reproducibility. It is indicated that the stationary phase prepared by the "thiol-ene" addition reaction is a new type of multi-mode stationary phase, which has a good development value. The study reported a new method for the rapid preparation of a rare "multi-mode" chiral stationary phase BzCSP based on the "thiol-ene" addition reaction and verified the practicability of BzCSP including good selectivity, high sensitivity, strong resistance to matrix interference, and good reproducibility.

Chirally factorised truncated conformal space approach

Truncated Conformal Space Approach (TCSA) is a highly efficient method to compute spectra, operator matrix elements and time evolution in quantum field theories defined as relevant perturbations of 1+1-dimensional conformal field theories. However, similarly to other exact diagonalisation methods, TCSA is ridden with the “curse of dimensionality”: the dimension of the Hilbert space increases exponentially with the (square root of the) truncation level, limiting its precision by the available memory resources. Here we describe an algorithm which exploits the chiral factorisation property of conformal field theory with periodic boundary conditions to achieve a substantial improvement in the truncation level. The Chirally Factorised TCSA (CFTCSA) algorithm presented here works with inputs describing the necessary CFT data in a specified format. It makes possible much more precise calculations with given computing resources and extends the reach of the method to problems requiring large Hilbert space dimensions. In fact, it has already been used in a number of recent works ranging from determination of form factors, through studying confinement of topological excitations to non-equilibrium dynamics. Besides the description of the algorithm, a MATLAB implementation of the algorithm is also provided as an ancillary file package, supplemented with example codes computing spectra, matrix elements and time evolution, and with CFT data for three different quantum field theories. We also give a detailed how-to guide for constructing the required CFT data for Virasoro minimal models with central charge c<1, and for the massless free boson with c=1.

A metamaterial based on planar spirals as a electromagnetic waves polarization converter

The design and modeling of a metasurface is carried out, which makes it possible to transform an incident linearly polarized electromagnetic wave into a transmitted wave with elliptical polarization close to circular. At the same time, the reflection coefficient of the wave is close to zero at the resonant frequency, since the metasurface is similar to the free space in its wave resistance. The resonant elements of the meta-surface (meta-atoms) are two-turn planar spirals with balanced dielectric and magnetic properties. Such spirals exhibit radically different properties with respect to waves with right and left circular polarization. The metasurface as a polarization converter has strong chiral properties, since it contains planar spirals of only one direction of twisting, and can be manufactured within the framework of printed circuit board technologies.

Raman Optical Activity of 1T-TaS2.

Measurements of optical activity can be readily performed in transparent matter by means of a rotation of transmitted light polarization. In the case of opaque bulk materials, such measurements cannot be performed, making it difficult to assess possible chiral properties. In this work, we present full angular polarization dependencies of the Raman modes of bulk 1T-TaS2, which has recently been suggested to have chiral properties after pulsed laser excitation. We found that a mechanical rotation of the sample does not alter polarization-resolved Raman spectra, which can only be explained by introducing an antisymmetric Raman tensor, frequently used to describe Raman optical activity (ROA). Raman spectra obtained under circularly polarized excitation demonstrate that 1T-TaS2 indeed shows ROA, providing strong evidence that 1T-TaS2 is chiral under the used conditions of laser excitation. Our results suggest that ROA may be used as a universal tool to study chiral properties of quantum materials.

Chiral-Induced Ultrathin Covalent Organic Frameworks Nanosheets with Tunable Circularly Polarized Luminescence.

Development of covalent organic frameworks (COFs) with circularly polarized luminescence (CPL) is still challenging. Here we first reported ultrathin COFs nanosheets (NS) based CPL materials using a chiral induced-synthesis strategy. Chiral amines served as chiral inducers to give COF TpBpy with chirality and participated in the modification of TpBpy, inhibiting the fluorescence quenching caused by π-π stacking to form ultrathin luminescent chiral COFs (chirCOFs) NS. The obtained chirCOFs R-/S-TpBpy NS had strong chirality and intense red CPL property with a |glum| of ∼0.02. Afterward, the carboxyl containing green and blue fluorescent dye molecules were postmodified onto the chirCOFs NS (chirCOFs/Dyes) to achieve color-adjustable CPL. Due to the chirality and energy transfer between chirCOFs and dye groups, the obtained chirCOFs/Dyes showed strong chirality and increased and tunable photoluminescence, exhibiting excellent, tunable, and amplified CPL performance with a maximum |glum| of ∼0.1, which was ∼5 times stronger than that of as-prepared chirCOFs NS. Moreover, the corresponding chirCOFs NS were dispersed into a polydimethylsiloxane (PDMS) matrix to form wafer size, highly transparent, and flexible COFs/PDMS films for practical CPL application. This study opens a new strategy to prepare ultrathin chirCOFs NS with strong and tunable CPL by chiral induction and provides a new approach for the preparation of transparent, large size, and flexible COFs composite films in chiral optical applications.

A Chirality-Based Quantum Leap.

There is increasing interest in the study of chiral degrees of freedom occurring in matter and in electromagnetic fields. Opportunities in quantum sciences will likely exploit two main areas that are the focus of this Review: (1) recent observations of the chiral-induced spin selectivity (CISS) effect in chiral molecules and engineered nanomaterials and (2) rapidly evolving nanophotonic strategies designed to amplify chiral light–matter interactions. On the one hand, the CISS effect underpins the observation that charge transport through nanoscopic chiral structures favors a particular electronic spin orientation, resulting in large room-temperature spin polarizations. Observations of the CISS effect suggest opportunities for spin control and for the design and fabrication of room-temperature quantum devices from the bottom up, with atomic-scale precision and molecular modularity. On the other hand, chiral–optical effects that depend on both spin- and orbital-angular momentum of photons could offer key advantages in all-optical and quantum information technologies. In particular, amplification of these chiral light–matter interactions using rationally designed plasmonic and dielectric nanomaterials provide approaches to manipulate light intensity, polarization, and phase in confined nanoscale geometries. Any technology that relies on optimal charge transport, or optical control and readout, including quantum devices for logic, sensing, and storage, may benefit from chiral quantum properties. These properties can be theoretically and experimentally investigated from a quantum information perspective, which has not yet been fully developed. There are uncharted implications for the quantum sciences once chiral couplings can be engineered to control the storage, transduction, and manipulation of quantum information. This forward-looking Review provides a survey of the experimental and theoretical fundamentals of chiral-influenced quantum effects and presents a vision for their possible future roles in enabling room-temperature quantum technologies.

Electrospinning of polymer nanofibers based on chiral polymeric nanoparticles

AbstractChiral polymeric nanoparticles (NPs) have emerged as a new and exciting field of research and in the last years due to their possible use for many applications in chiral chemistry however the efficiency of separating enantiomerically pure compounds has been always challenging. In this article, we focus on electrospun nanofibers formed by chiral functional NPs based on leucine or phenylalanine amino acids with polysulfone (PSF). Combining chiral functional NPs with PSF in electrospinning method provides us to get intertwined electrospun membranes with chiral property and used them for separation of racemic mixtures. We have also studied chiral functional conventional membranes formed by PSF and NPs. The NPs were prepared by miniemulsion polymerization and were characterized by DLS, SEM, MS, and NMR and display spherical structure with a narrow size distribution in the range of 200 to 250 nm. The characteristics of the membranes in terms of their morphology were analyzed. The permselective properties of the all membranes in the separation of racemic mixture were studied using aqueous solutions of leucine. Time‐resolved circular dichroism and chiral column high‐performance liquid chromatography (HPLC) were used to provide evidence for enantioselective separation. Our results show the membrane which is based on PSF and leucine NPs and formed by conventional method gives the best results for enantioselective separation by showing 18% enantiomeric excess (EE).

Quasinormal Mode Theory of Chiral Power Flow from Linearly Polarized Dipole Emitters Coupled to Index-Modulated Microring Resonators Close to an Exceptional Point

Chiral emission can be achieved from a circularly polarized dipole emitter in a nanophotonic structure that possess special polarization properties such as a polarization singularity, namely with right or left circularly polarization (C-points). Recently, Chen et al. [Nature Physics 16, 571 (2020)] demonstrated the surprising result of chiral radiation from a linearly-polarized (LP) dipole emitter, and argued that this effect is caused by a decoupling with the underlying eigenmodes of a non-Hermitian system, working at an exceptional point (EP). Here we present a quasinormal mode (QNM) approach to model a similar index-modulated ring resonator working near an EP and show the same unusual chiral power flow properties from LP emitters, in direct agreement with the experimental results. We explain these results quantitatively without invoking the interpretation of a missing dimension (the Jordan vector) and a decoupling from the cavity eigenmodes, since the correct eigenmodes are the QNMs which explain the chiral emission using only two cavity modes. By coupling a LP emitter with the dominant two QNMs of the ring resonator, we show how the chiral emission depend on the position and orientation of the emitter, which is also verified by the excellent agreement with respect to the power flow between the QNM theory and full numerical dipole solutions. We also show how a normal mode solution will fail to capture the correct chirality since it does not take into account the essential QNM phase. Moreover, we demonstrate how one can achieve frequency-dependent chiral emission, and replace lossy materials with gain materials in the index modulation to reverse the chirality.

Optical Properties and Dynamic Extrinsic Chirality of Structured Monolayer Black Phosphorus

Chiral metamaterials have drawn increasing attention due to their strong chiral responses. Monolayer black phosphorus is a tunable two-dimensional material with anisotropy that plays an important role in a variety of fields such as chirality and polarization control. In this work, we propose a metamaterial with structured monolayer black phosphorus to manipulate the transmission properties of circularly polarized waves. The metamaterial exhibits strong circular dichroism and circular birefringence effects depending on oblique incidence of the circularly polarized wave and has a weaker circular conversion dichroism effect as well. Moreover, this work also investigates effects of different chiral phenomena of the metamaterial on various structural parameters as well as incident angles and the electron concentration. It has been proved that the electron concentration of monolayer black phosphorus can dynamically tune the chirality properties. Remarkably, the non-zero pure optical activity always occurs at one certain frequency regardless of the elevation angle and the azimuthal angle. The proposed framework provides opportunities for designing meta-devices with monolayer black phosphorus and practical potentials for novel and high-performance infrared metamaterials.

Phase space crystal vibrations: Chiral edge states with preserved time-reversal symmetry

Phase-space crystal is a solidlike crystalline state in phase space formed by atoms, subject to a time-periodic drive. The authors show that interactions between these atoms can give rise to vibrational band structures with nontrivial Chern numbers and chiral edge states in phase space. Remarkably, these arise even in the presence of time-reversal symmetry in contrast to all topological transport scenarios in real space. Phase-space crystal vibrations offer a new platform for phononic topological transport whereby chiral properties arise naturally.

Nuclear Magnetic Resonance Reveals Molecular Species in Carbon Nanodot Samples Disclosing Flaws.

Carbon nanodots are currently one of the hot topics in the nanomaterials world, due to their accessible synthesis and promising features. However, the purification of these materials is still a critical aspect, especially for syntheses involving molecular precursors. Indeed, the presence of unreacted species or small organic molecules formed during solvothermal treatments can affect the properties of the synthesized nanomaterials. To illustrate the extreme importance of this issue, we present two case studies in which insufficient purification results in misleading conclusions regarding the chiral and fluorescent properties of the investigated materials. Key to identify molecular species is the use of nuclear magnetic resonance, which proves to be an effective tool. Our work highlights the need to include nuclear magnetic resonance as a standard characterization technique for carbon‐based nanomaterials, to minimize the risk of observing properties that arise from molecular species, rather than the target carbon nanodots.

Nuclear Magnetic Resonance Reveals Molecular Species in Carbon Nanodot Samples Disclosing Flaws

AbstractCarbon nanodots are currently one of the hot topics in the nanomaterials world, due to their accessible synthesis and promising features. However, the purification of these materials is still a critical aspect, especially for syntheses involving molecular precursors. Indeed, the presence of unreacted species or small organic molecules formed during solvothermal treatments can affect the properties of the synthesized nanomaterials. To illustrate the extreme importance of this issue, we present two case studies in which insufficient purification results in misleading conclusions regarding the chiral and fluorescent properties of the investigated materials. Key to identify molecular species is the use of nuclear magnetic resonance, which proves to be an effective tool. Our work highlights the need to include nuclear magnetic resonance as a standard characterization technique for carbon‐based nanomaterials, to minimize the risk of observing properties that arise from molecular species, rather than the target carbon nanodots.

Triazine- and Binaphthol-Based Chiral Macrocycles and Cages: Synthesis, Structure, and Solid-State Assembly.

A series of triazine- and binaphthol-based homochiral and heterochiral macrocycles and cages were easily synthesized. Either fragment coupling or a one-pot approach afforded the desired products in 52-91% yields on a multigram scale as enantiopure forms. As disclosed by the crystal structures, these macrocycles and cages possess intriguing chiral cavities and assembly properties. In particular, (S,S,S)-Cage features a D3-symmetric double-faced propeller-like structure with three chiral pockets at the side. It forms a highly ordered hexagonal column-like assembly and multiple distinct helical channels in its crystal.

Tuning the (Chir)Optical Properties and Squeezing out the Inherent Chirality in Polyphenylene-Locked Helical Carbon Nanorings.

Distorting linear polyaromatic hydrocarbons (PAHs) out of planarity affects their physical properties and breaks their symmetry to induce inherent chirality. However, the chirality cannot be achieved in large distorted PAHs-based macrocycles due to a low racemization barrier for isomerization. Herein, we report the precise synthesis and tuning size-dependent (chir)optical properties of a new class of chiral PAHs-containing conjugated macrocycles (cyclo[n]paraphenylene-2,6-anthrylene, [n]CPPAn2,6 ; n=6-8). Their inherent chiralities were squeezed out in small anthrylene-based macrocycles. Efficient resolutions for chiral enantiomers with (P)/(M)-helicity of small [6-7]CPPAns were achieved by HPLC. Interestingly, these macrocycles showed enriched size-dependent physical, chiral, and (chir)optical properties. Theoretical calculations indicate that these macrocycles have high strain energy (Estrain =60.8 to 73.4 kcal/mol) and very small Egap (∼3.0 eV). Notably, these enantiomers showed strong chiroptical properties and dissymmetry factors (|gabs | and |glum |∼0.01 for an enantiomer of [6]CPPAn2,6 ), which can give them potential applications in optically active materials.

Properties of the QCD thermal transition with Nf=2+1 flavors of Wilson quark

We study properties of the thermal transition in QCD, using anisotropic, fixed-scale lattice simulations with ${N}_{f}=2+1$ flavors of Wilson fermion. Observables are compared for two values of the pion mass, focusing on chiral properties. Results are presented for the Polyakov loop, various susceptibilities, the chiral condensate and its susceptibility, and the onset of parity doubling in the light and strange baryonic sector.

Monte Carlo simulations of the self-assembly of hierarchically organized metal-organic networks on solid surfaces

The coordination-driven self-assembly of two-dimensional (2D) supramolecular architectures is a convenient method of rational construction of one-atom-thick nanomaterials with desired topology, intriguing physicochemical properties and high cognitive value. In this work, we use coarse-grained Monte Carlo (MC) computer simulations to study the self-assembly of functional bridging ligands with mononuclear metal centers on a triangular lattice. Particularly, we focus on the role of anisotropic, reversible ligand → metal coordinate bonds in the bottom-up formation of hierarchically organized metal-organic networks composed of star-shaped and rod-like linkers (representing real organic molecules) and trivalent metal atoms. In our model π aromatic ligands were modeled in a simplified way as a collection of flat, rigid, and interconnected segments with properly encoded short-ranged interactions. Depending on the composition of the investigated overlayers, we observed the spontaneous formation a cascade of openwork (co)crystals with a hierarchical structure, controllable chirality and scalable morphological properties like porosity, connectivity, density, etc. Our theoretical findings can pave the way for the experimental fabrication of the novel surface-confined metal-organic networks (SMONs) in which anisotropic coordinate bonds play a decisive role.

Induction of chiral polymers from metal-organic framework for stereoselective recognition

So far, the fabrication of chiral metal-organic framework (CMOF) is difficult to predict and the chiral functionality mainly comes from the building blocks that is a part of the frameworks. The induction effect in the chiral nanochannels of the metal-organic framework (MOF) makes achiral polymers have chiral properties, which has not been well explored. Therefore, CMOFs with chiral nanochannels or chiral pores appear to have special functions. Herein, CMOFs (D-his-ZIF-8) with chiral micropores or chiral nanochannels are prepared through a simple 2-methyl imidazolate in-situ substitution by d-histidine. The unmodified polyaniline with chirality (c-PANI) was synthesized in chiral nanochannels and pores of CMOF, which brought about chiral induction from the chiral nanochannels and pores of CMOF to c-PANI chains. The circular dichroism shows that the c-PANI chains released from the chiral nanochannel still maintains the chiral properties even leaves the chiral nanochannel. It can be seen from the electrochemical results that c-PANI has excellent conductivity, and the conductivity of CMOF is very poor. Electrochemical recognition showed that both CMOF and c-PANI have certain chiral recognition effects for L-Trp and D-Trp, from which the optimal recognition effect was obtained from c-PANI chains. This shows that the excellent conductivity of c-PANI not only expands the electrochemical signal, but also the helical structure of the c-PANI chains accelerates the distinction of chiral molecules. This study provides a novel perspective to induce chiral polymer chains with better conductivity in the nanochannels of CMOF.

Inorganic Chiral Hybrid Nanostructures for Tailored Chiroptics and Chirality‐Dependent Photocatalysis

AbstractInorganic chiral hybrid nanostructures that embed chirality within distinct material compositions can create novel chiral properties and functionalities absent from achiral nanostructures; however, they remain largely unexplored. We report, for the first time, a class of chiral plasmonic metal‐semiconductor core‐shell nanostructures that employ structurally chiral nanoparticles as chirality inducing templates to grow functional shell materials, which allowed us to independently control material parameters such as core geometry and shell thickness, as well as handedness of the system. We experimentally and theoretically achieved enhanced and tunable chiroptical activity of the heterostructures as a result of the core‐shell strong coupling effect. As a proof‐of‐concept demonstration, we demonstrate that the chiral hybrid nanostructures can drive chirality‐dependent photocatalytic hydrogen generation under circularly polarized light. This study enables rational design and functionalization of chiral hybrid nanomaterials towards enhanced chiral light–matter interactions and chiral device applications.

Inorganic Chiral Hybrid Nanostructures for Tailored Chiroptics and Chirality-Dependent Photocatalysis.

Inorganic chiral hybrid nanostructures that embed chirality within distinct material compositions can create novel chiral properties and functionalities absent from achiral nanostructures; however, they remain largely unexplored. We report, for the first time, a class of chiral plasmonic metal-semiconductor core-shell nanostructures that employ structurally chiral nanoparticles as chirality inducing templates to grow functional shell materials, which allowed us to independently control material parameters such as core geometry and shell thickness, as well as handedness of the system. We experimentally and theoretically achieved enhanced and tunable chiroptical activity of the heterostructures as a result of the core-shell strong coupling effect. As a proof-of-concept demonstration, we demonstrate that the chiral hybrid nanostructures can drive chirality-dependent photocatalytic hydrogen generation under circularly polarized light. This study enables rational design and functionalization of chiral hybrid nanomaterials towards enhanced chiral light-matter interactions and chiral device applications.

Synthesis, crystal structures and photoelectric properties of copper(I) alkynyl nanoclusters

<p indent="0mm">Metal nanoclusters (NCs) are composed of several to thousands of metal atoms with a diameter of &lt; <sc>3 nm.</sc> Such metal NCs exhibit dramatically unique electronic/geometric structures and physical/chemical properties which differ from those of bulk metal materials. Among metal NCs, coinage metal (Au, Ag, and Cu) NCs have received extensive attention because of their chirality, optical and catalytic properties. Cu is more abundant than Au and Ag, yet copper(0)/copper(I) is more reactive and easier to oxidize than silver or gold, which makes it more difficult to prepare Cu NCs and investigate their properties. By taking guidelines from Au and Ag NC research, thiolate, phosphine, and alkynyl ligand-protected Cu NCs have recently received increasing attention. Alkynyl ligands have more abundant coordination modes compared to thiolate and phosphine ligands. Some copper(I) alkynyl NCs with unique crystal structures, good stability and rich properties have been recently reported. Herein, firstly, this paper introduces recent advances in developing efficient synthetic methods for copper(I) alkynyl NCs, highlighting the underlying physical and chemical properties that make the delicate control of their sizes and surfaces possible. The synthesis of copper(I) alkynyl NCs can be roughly classified into four categories: Solvothermal, reduction, template, and ligand exchange. Generally, the steric effect of the introduced protective ligand breaks their polymeric structures and improves solubility. Some copper(I) alkynyl NCs can also be produced by adjusting the auxiliary ligands and anionic templating agents. In addition, the concentration of ligands and precursors, pH and temperature of the reaction system can be used to adjust the reaction kinetics, and this leads to the formation of the monodisperse copper(I) alkynyl NCs. Secondly, we discuss recent advances in the structural determination of copper(I) alkynyl NCs, of which the size and shape can be controlled to a certain extent by the judicious choice of templating anions and auxiliary ligands. The atomically precise nature of their structures enables the investigation of the structure-property relationship, which may further optimize their performance. One of the most important properties of copper(I) alkynyl NCs is the luminescence, which offers potential applications as photoelectric detectors and in sensing and bio-imaging. We highlight some examples of copper(I) alkynyl NCs to demonstrate their photoelectric properties. Finally, the brief conclusion and outlook on the research and challenges of copper(I) alkynyl NCs are presented. We expect this review will serve as an introduction and reference for researchers who are interested in exploring metal NCs.