Chiral-induced spin selectivity in biomolecules, hybrid organic-inorganic perovskites and inorganic materials: a comprehensive review on recent progress

Effects of Chiral Polypeptides on Skyrmion Stability and Dynamics

Magnetic skyrmions, topologically stabilized chiral spin textures in magnetic thin films, have garnered considerable interest due to their efficient manipulation and resulting potential as efficient nanoscale information carriers. One intriguing approach to address the challenge of tuning skyrmion properties involves using chiral molecules. Chiral molecules can locally manipulate magnetic properties by inducing magnetization through spin exchange interactions and by creating spin currents. Here, Magneto-Optical Kerr Effect (MOKE) microscopy is used to image the impact of chiral polypeptides on chiral magnetic structures. The chiral polypeptides shift the spin reorientation transition temperature, reduce thermal skyrmion motion, and alter the coercive field locally, enhancing skyrmion stability and thus enabling local control. These findings demonstrate the potential of chiral molecules to address challenges for skyrmion based devices, thus paving the way to applications such as the racetrack memory, reservoir computing and others.

Mechanisms for translating chiral enantiomers separation research into macroscopic visualization

Chirality is a common phenomenon in nature, including the dominance preference of small biomolecules, the special spatial conformation of biomolecules, and the biological and physiological processes triggered by chirality. The selective chiral recognition of molecules in nature from up-bottom or bottom-up is of great significance for living organisms. Such as the transcription of DNA, the recognition of membrane proteins, and the catalysis of enzymes all involve chiral recognition processes. The selective recognition between these macromolecules is mainly achieved through non covalent interactions such as hydrophobic interactions, ammonia bonding, electrostatic interactions, metal coordination, van der Waals forces, and π-π stacking. Researchers have been committed to studying how to convert this weak non covalent interaction into macroscopic visualization, which has further understood of the interactions between chiral molecules and is of great significance for simulating the interactions between molecules in living organisms. This article reviews several models of chiral recognition mechanisms, the interaction forces involved in the chiral recognition process, and the research progress of chiral recognition mechanisms. The outlook in this review points out that studying chiral recognition interactions provides an important bridge between chiral materials and the life sciences, providing an ideal platform for studying chiral phenomena in biological systems.

Surface Magnetic Stabilization and the Photoemission Chiral-Induced Spin-Selectivity Effect

The spinterface mechanism was suggested as a possible origin for the chirality-induced spin-selectivity (CISS) effect and was used to explain and reproduce, with remarkable accuracy, experimental data from transport experiments showing the CISS effect. Here, we apply the spinterface mechanism to explain the appearance of magnetization at the interface between nonmagnetic metals and chiral molecules, through the stabilization of otherwise fluctuating magnetic moments. We show that the stabilization of surface magnetic moments occurs for a wide range of realistic parameters and is robust against dephasing. Importantly, we show that the direction of the surface magnetic moments is determined by the chiral axis of the chiral molecules. Armed with the concept of stable surface magnetic moments, we then formulated a theory for the photoemission CISS effect. The theory, based on spin-dependent scattering, leads to direct predictions regarding the relation between the photoemission CISS effect, the chiral axis direction, the spinterface "size", and the tilt angle of the detector with respect to the surface. These predictions are within reach of current experimental capabilities and may shed new light on the origin of the CISS effect.

Chiral Inorganic Polar BaTiO3/BaCO3 Nanohybrids with Spin Selection for Asymmetric Photocatalysis

Chirality-dependent photocatalysis is an emerging domain that leverages unique chiral light-matter interactions for enabling asymmetric catalysis driven by spin polarization induced by circularly polarized light selection. Herein, we synthesize chiral inorganic polar BaTiO3/BaCO3 nanohybrids for asymmetric photocatalysis via a hydrothermal method employing chiral glucose as a structural inducer. When excited by opposite circularly polarized light, the same material exhibits significant asymmetric catalysis, while enantiomers present an opposite polarization preference. More importantly, the preferred circularly polarized light undergoes reversal with reversal of the CD signal. Systematic experimental results demonstrate that more photogenerated carriers are generated in chiral semiconductors under suitable circularly polarized light irradiation, including more spin-polarized electrons, which inhibits the recombination of electron-hole pairs and promotes the activation of oxygen molecules into reactive oxygen species, thus inducing this asymmetric photocatalytic feature. This study provides valuable insights for the development of highly efficient polarization-sensitive chiral perovskite nanostructures as promising candidates for next-generation, multifunctional chiral device applications.

Chiral Induced Spin Selectivity

Since the initial landmark study on the chiral induced spin selectivity (CISS) effect in 1999, considerable experimental and theoretical efforts have been made to understand the physical underpinnings and mechanistic features of this interesting phenomenon. As first formulated, the CISS effect refers to the innate ability of chiral materials to act as spin filters for electron transport; however, more recent experiments demonstrate that displacement currents arising from charge polarization of chiral molecules lead to spin polarization without the need for net charge flow. With its identification of a fundamental connection between chiral symmetry and electron spin in molecules and materials, CISS promises profound and ubiquitous implications for existing technologies and new approaches to answering age old questions, such as the homochiral nature of life. This review begins with a discussion of the different methods for measuring CISS and then provides a comprehensive overview of molecules and materials known to exhibit CISS-based phenomena before proceeding to identify structure-property relations and to delineate the leading theoretical models for the CISS effect. Next, it identifies some implications of CISS in physics, chemistry, and biology. The discussion ends with a critical assessment of the CISS field and some comments on its future outlook.

Quantum Biology and the Potential Role of Entanglement and Tunneling in Non-Targeted Effects of Ionizing Radiation: A Review and Proposed Model

It is well established that cells, tissues, and organisms exposed to low doses of ionizing radiation can induce effects in non-irradiated neighbors (non-targeted effects or NTE), but the mechanisms remain unclear. This is especially true of the initial steps leading to the release of signaling molecules contained in exosomes. Voltage-gated ion channels, photon emissions, and calcium fluxes are all involved but the precise sequence of events is not yet known. We identified what may be a quantum entanglement type of effect and this prompted us to consider whether aspects of quantum biology such as tunneling and entanglement may underlie the initial events leading to NTE. We review the field where it may be relevant to ionizing radiation processes. These include NTE, low-dose hyper-radiosensitivity, hormesis, and the adaptive response. Finally, we present a possible quantum biological-based model for NTE.

Chiral mesostructured NiFe2O4 films with chirality induced spin selectivity

Chiral mesostructured NiFe2O4 films (CMNFFs) were synthesized using L-/D-tyrosine as symmetry-breaking and structure-directing agents through a hydrothermal method. For the first time, chirality induced spin selectivity was directly observed in these ferrimagnetic materials using chirality-dependent magnetic-tip conducting atomic force microscopy (mc-AFM).

Enantioselective and Chemoselective Optical Detection of Chiral Organic Compounds without Resorting to Chromatography

Enantiorecognition and resolution are of essential importance in many diverse areas of science. Whenever there arises a need to analyze/investigate enantiomers in different situations chromatography stands up in our minds immediately. Nevertheless, chemoselective and enantioselective recognition/discrimination (without going for separation) constitutes a different perception and requirement. The techniques using chiroptical sensing cause detection based on molecular interactions induced in different manners. Enantioselective sensing of monosaccharides in γ-cyclodextrin assembly and by diboronic acid based fluorescent sensors, application of bi-naphthol and H8 BINOL based sensors and dendrimers, metal-to-ligand charge transfer transitions in CD, exciton-coupled circular dichroism, surface enhanced Raman spectroscopy, and enantioselective indicator displacement sensor arrays for enantioselective recognition/detection of chiral organic compounds, such as amines, amino acids/alcohols, and hydroxycarboxylic acids have been discussed in progressive manner with mechanistic explanations, wherever available. Besides, the chiroptical vs LC approach has been discussed. The present paper is focused on certain different non-chromatographic optical techniques and aims to extend an understanding and a view to consider such techniques which have been successful in selective detection, and determination of absolute configuration and enantiomeric excess, (without resorting to separation vis-à-vis LC) and that have potential use in high-throughput chiral assay and combinatorial search for asymmetric catalysts and reagents.

Chirality detection of biological molecule through spin selectivity effect

The ability to accurately monitor chiral biological molecules is of great significance for their potential applications in disease diagnosis and virus detection. As the existing chiral detection technologies are mainly relying on an optical method by using left/right circularly polarized light, the universality is low and the operation is complicated. Moreover, large quantity of chiral molecules is required, causing low detection efficiency. Here, a self-assembled monolayer of polypeptides has been fabricated to realize trace detection of chirality based on spin selectivity of photon-electron interaction. We have utilized Kerr technique to detect the rotation angle by the molecular monolayer, which indicates the chirality of polypeptides. The chiral structure of a biological molecule could result in spin-selectivity of electrons and thus influence the interaction between electron spin and light polarization. A Kerr rotation angle of ∼3° has been obviously observed, equivalent to the magneto-optic Kerr effect without magnetic material or magnetic field. Furthermore, we have provided a novel solution to achieve chirality discrimination and amplification simultaneously through an optical fiber. The proposed design is applicable for chiral detection via increasing their differential output signal, which clearly demonstrates a useful strategy toward chirality characterization of biological molecules.

Achiral dipoles on a ferromagnet can affect its magnetization direction

We demonstrate the possibility of a coupling between the magnetization direction of a ferromagnet and the tilting angle of adsorbed achiral molecules. To illustrate the mechanism of the coupling, we analyze a minimal Stoner model that includes Rashba spin-orbit coupling due to the electric field on the surface of the ferromagnet. The proposed mechanism allows us to study magnetic anisotropy of the system with an extended Stoner-Wohlfarth model and argue that adsorbed achiral molecules can change magnetocrystalline anisotropy of the substrate. Our research aims to motivate further experimental studies of the current-free chirality induced spin selectivity effect involving both enantiomers.

Spin-induced electron transmission through metal-organic chiral crystals

Metal-organic Co(II)-phenylalanine crystals were studied and were found to possess magnetic properties and long-range spin transport. Magnetic measurements confirmed that in the crystals there are antiferromagnetic interactions between Co(II) and the lattice. The metal-organic crystals (MOCs) also present the chirality-induced spin selectivity (CISS) effect at room temperature. A long-range spin polarization is observed using a magnetic conductive-probe atomic force microscope. The spin polarization is found to be in the range of 35-45%.