Pre-twisting for improved genome modification and miRNA targeting.

Two reports by Dhuri et al. and Oyaghire et al., respectively, show that, through installing chiral centers at the backbone of the artificial nucleic acid, peptide nucleic acid (PNA), enhanced miRNA targeting and genome modification can be achieved, with important implications in fighting cancers and ß-thalassemia.

Direct-write 3D printing of plasmonic nanohelicoids by circularly polarized light.

Chiral plasmonic surfaces with 3D "forests" from nanohelicoids should provide strong optical rotation due to alignment of helical axis with propagation vector of photons. However, such three-dimensional nanostructures also demand multi-step nanofabrication, which is incompatible with many substrates. Large-scale photonic patterns on polymeric and flexible substrates remain unattainable. Here, we demonstrate the substrate-tolerant direct-write printing and patterning of silver nanohelicoids with out-of-plane 3D orientation using circularly polarized light. Centimeter-scale chiral plasmonic surfaces can be produced within minutes using inexpensive medium-power lasers. The growth of nanohelicoids is driven by the symmetry-broken site-selective deposition and self-assembly of the silver nanoparticles (NPs). The ellipticity and wavelength of the incident photons control the local handedness and size of the printed nanohelicoids, which enables on-the-fly modulation of nanohelicoid chirality during direct writing and simple pathways to complex multifunctional metasurfaces. Processing simplicity, high polarization rotation, and fine spatial resolution of the light-driven printing of stand-up helicoids provide a rapid pathway to chiral plasmonic surfaces, accelerating the development of chiral photonics for health and information technologies.

Tapered chiral nanoparticles as broad-spectrum thermally stable antivirals for SARS-CoV-2 variants.

The incessant mutations of viruses, variable immune responses, and likely emergence of new viral threats necessitate multiple approaches to novel antiviral therapeutics. Furthermore, the new antiviral agents should have broad-spectrum activity and be environmentally stable. Here, we show that biocompatible tapered CuS nanoparticles (NPs) efficiently agglutinate coronaviruses with binding affinity dependent on the chirality of surface ligands and particle shape. L-penicillamine-stabilized NPs with left-handed curved apexes display half-maximal inhibitory concentrations (IC50) as low as 0.66 pM (1.4 ng/mL) and 0.57 pM (1.2 ng/mL) for pseudo-type SARS-CoV-2 viruses and wild-type Wuhan-1 SARS-CoV-2 viruses, respectively, which are about 1,100 times lower than those for antibodies (0.73 nM). Benefiting from strong NPs-protein interactions, the same particles are also effective against other strains of coronaviruses, such as HCoV-HKU1, HCoV-OC43, HCoV-NL63, and SARS-CoV-2 Omicron variants with IC50 values below 10 pM (21.8 ng/mL). Considering rapid response to outbreaks, exposure to elevated temperatures causes no change in the antiviral activity of NPs while antibodies are completely deactivated. Testing in mice indicates that the chirality-optimized NPs can serve as thermally stable analogs of antiviral biologics complementing the current spectrum of treatments.

Prebiotic access to enantioenriched amino acids via peptide-mediated transamination reactions.

The kinetic resolution of racemic amino acids mediated by dipeptides and pyridoxal provides a prebiotically plausible route to enantioenriched proteinogenic amino acids. The enzymatic transamination cycles that are key to modern biochemical formation of enantiopure amino acids may have evolved from this half of the reversible reaction couple. Kinetic resolution of racemic precursors emerges as a general route to enantioenrichment under prebiotic conditions.

Nonreciprocity and odd viscosity in chiral active fluids.

Odd viscosity couples stress to strain rate in a dissipationless way. It has been studied in plasmas under magnetic fields, superfluid [Formula: see text], quantum-Hall fluids, and recently in the context of chiral active matter. In most of these studies, odd terms in the viscosity obey Onsager reciprocal relations. Although this is expected in equilibrium systems, it is not obvious that Onsager relations hold in active materials. By directly coarse-graining the kinetic energy and independently using both the Poisson-bracket formalism and a kinetic theory derivation, we find that the appearance of a nonvanishing angular momentum density, which is a hallmark of chiral active materials, necessarily breaks Onsager reciprocal relations. This leads to a non-Hermitian dynamical matrix for the total hydrodynamic momentum and to the appearance of odd viscosity and other nondissipative contributions to the viscosity. Furthermore, by accounting for both the angular momentum density and interactions that lead to odd viscosity, we find regions in the parameter space in which 3D odd mechanical waves propagate and regions in which they are mechanically unstable. The lines separating these regions are continuous lines of exceptional points, suggesting a possible nonreciprocal phase transition.

Kink-Controlled Gold Nanoparticles for Electrochemical Glucose Oxidation.

Enzymes in nature efficiently catalyze chiral organic molecules by elaborately tuning the geometrical arrangement of atoms in the active site. However, enantioselective oxidation of organic molecules by heterogeneous electrocatalysts is challenging because of the difficulty in controlling the asymmetric structures of the active sites on the electrodes. Here, we show that the distribution of chiral kink atoms on high-index facets can be precisely manipulated even on single gold nanoparticles; and this enabled stereoselective oxidation of hydroxyl groups on various sugar molecules. We characterized the crystallographic orientation and the density of kink atoms and investigated their specific interactions with the glucose molecule due to the geometrical structure and surface electrostatic potential.

Dimensional and Doping Engineering of Chiral Perovskites with Enhanced Spin Selectivity for Green Emissive Spin Light-Emitting Diodes.

Chiral perovskites play a pivotal role in spintronics and optoelectronic systems attributed to their chiral-induced spin selectivity (CISS) effect. Specifically, they allow for spin-polarized charge transport in spin light-emitting diodes (LEDs), yielding circularly polarized electroluminescence at room temperature without external magnetic fields. However, chiral lead bromide-based perovskites have yet to achieve high-performance green emissive spin-LEDs, owing to limited CISS effects and charge transport. Herein, we employ dimensional regulation and Sn2+-doping to optimize chiral bromide-based perovskite architecture for green emissive spin-LEDs. The optimized (PEA)x(S/R-PRDA)2-xSn0.1Pb0.9Br4 chiral perovskite film exhibits an enhanced CISS effect, higher hole mobility, and better energy level alignment with the emissive layer. These improvements allow us to fabricate green emissive spin-LEDs with an external quantum efficiency (EQE) of 5.7% and an asymmetry factor |gCP-EL| of 1.1 × 10-3. This work highlights the importance of tailored perovskite architectures and doping strategies in advancing spintronics for optoelectronic applications.

Universal Chiral-Plasmon-Induced Upward and Downward Transfer of Circular Dichroism to Achiral Molecules.

Electromagnetic chirality transfer represents an effective means of the nanoscale manipulation of optical chirality. While most of the previous reports have exclusively focused on the circular dichroism (CD) transfer from UV-responsive chiral molecules toward visible-resonant achiral colloidal nanoparticles, here we demonstrate a reverse process in which plasmonic chirality can be transferred to achiral molecules, either upward from visible to UV or downward from visible to near infrared (NIR). By hybridizing achiral UV- or NIR-responsive dye molecules with chiral metal nanoparticles in solution, we observe a chiral-plasmon-induced CD (CPICD) signal at the intrinsically achiral molecular absorption bands. Full-wave electromagnetic modeling reveals that both near-field Coulomb interaction and far-field radiative coupling contribute to the observed CPICD, indicating that the mechanism considered here is universal for different material systems and types of optical resonances. Our study provides a set of design guidelines for broadband nanophotonic chiral sensing from the UV to NIR spectral regime.

Chiral Phonons: Prediction, Verification, and Application.

Chirality as an asymmetric property is prevalent in nature. In physics, the chirality of the elementary particles that make up matter has been widely studied and discussed, and nowadays, the concept has developed into the field of phonons. As an important fundamental excitation in condensed matter physics, phonons are traditionally considered to be linearly polarized and nonchiral. However, in recent years, the chirality of phonons has been revealed and further experimentally verified. The discovery has triggered a series of new explorations and developments in phonon-related physical processes. This Mini-Review provides an overview of the theoretical prediction of chiral phonons and multiple experimental detection methods and highlights the current key issues in the application of chiral phonons in different fields.

Tuning the Chiral Growth of Plasmonic Bipyramids via the Wavelength and Polarization of Light.

Circularly polarized light (CPL) is a versatile tool to prepare chiral nanostructures, but the mechanism for inducing enantioselectivity is not well understood. This work shows that the energy and polarization of visible photons can initiate photodeposition at different sites on plasmonic nanocrystals. Here, CPL on achiral gold bipyramids (AuBPs) creates hot holes that oxidatively deposit PbO2 asymmetrically. We show for the first time that the location of PbO2 photodeposition and hence optical dissymmetry depends on the CPL wavelength. Specifically, 488 and 532 nm CPL induce PbO2 growth in the middle of AuBPs, whereas 660 nm CPL induces PbO2 growth at the tips. Our observations show that wavelength-dependent plasmonic field distributions are more important than surface lightning rod effects in localizing plasmon-mediated photochemistry. The largest optical dissymmetry occurs at excitation wavelengths between the transverse and longitudinal resonances of the AuBPs because higher-order modes are required to induce chiral electric fields.

Nonlocal Metasurface with Chiral Exceptional Points in the Telecom-Band.

The exceptional point (EP) is the critical phase transition point in parity-time (PT) symmetry systems, offering many unique physical phenomena, such as a chiral response. Achieving chiral EP in practical applications has been challenging due to the delicate balance required between gain and loss and complicated fabrication, limiting both working band and device miniaturization. Here, we proposed a nonlocal metasurface featuring orthogonal gold nanorods, where loss modulation is achieved through rod size and lattice pitch. By tuning the coupling strength, we experimentally observed the PT symmetry phase transition and chiral EP in the telecom-band. The experimental and simulated circular conversion dichroism at EP reach 0.79 and 0.99, respectively. We also demonstrated an abrupt phase flip of a specific component near EP theoretically. This work provides a feasible scheme for exploring EP in polarized space within the telecom-band, which may find applications in polarization control, wavelength division multiplexing, ultrasensitive sensing, imaging, etc.

Structural Determinants of Chirally Selective Transport of Amino Acids through the α-Hemolysin Protein Nanopores of Free-Standing Planar Lipid Membranes.

Despite the importance of the enantioselective transport of amino acids through transmembrane protein nanopores from fundamental and practical perspectives, little has been explored to date. Here, we study the transport of amino acids through α-hemolysin (αHL) protein pores incorporated into a free-standing lipid membrane. By measuring the transport of 13 different amino acids through the αHL pores, we discover that the molecular size of the amino acids and their capability to form hydrogen bonds with the pore surface determine the chiral selectivity. Molecular dynamics simulations corroborate our findings by revealing the enantioselective molecular-level interactions between the amino acid enantiomers and the αHL pore. Our work is the first to present the determinants for chiral selectivity using αHL protein as a molecular filter.

Lead-Free Chiral Perovskite for High Degree of Circularly Polarized Light Emission and Spin Injection.

We report a zero-dimensional (0D) lead-free chiral perovskite (S-/R-MBA)4Bi2I10 with a high degree of circularly polarized light (CPL) emission. Our 0D lead-free chiral perovskite exhibits an average degree of circular polarization (DOCP) of 19.8% at 78 K under linearly polarized laser excitation, and the maximum DOCP can reach 25.8%, which is 40 times higher than the highest DOCP of 0.5% in all reported lead-free chiral perovskites to the best of our knowledge. The high DOCP of (S-/R-MBA)4Bi2I10 is attributed to the free exciton emission with a Huang-Rhys factor of 2.8. In contrast, all the lead-free chiral perovskites in prior reports are dominant by self-trapped exciton in which the spin relaxation reduces DOCP dramatically. Moreover, we realize the manipulation of the valley degree of freedom of monolayer WSe2 by using the spin injection of the 0D chiral lead-free perovskites. Our results provide a new perspective to develop lead-free chiral perovskite devices for CPL light source, spintronics, and valleytronics.

Uncovering Maximum Chirality in Resonant Nanostructures.

Chiral nanostructures allow engineering of chiroptical responses; however, their design usually relies on empirical approaches and extensive numerical simulations. It remains unclear if a general strategy exists to enhance and maximize the intrinsic chirality of subwavelength photonic structures. Here, we suggest a microscopic theory and uncover the origin of strong chiral responses of resonant nanostructures. We reveal that the reactive helicity density is critically important for achieving maximum chirality at resonances. We demonstrate our general concept on the examples of planar photonic crystal slabs and metasurfaces, where out-of-plane mirror symmetry is broken by a bilayer design. Our findings provide a general recipe for designing photonic structures with maximum chirality, paving the way toward many applications, including chiral sensing, chiral emitters and detectors, and chiral quantum optics.

Single-Particle Photothermal Circular Dichroism and Photothermal Magnetic Circular Dichroism Microscopy.

Recent advances in single-particle photothermal circular dichroism (PT CD) and photothermal magnetic circular dichroism (PT MCD) microscopy have shown strong promise for diverse applications in chirality and magnetism. Photothermal circular dichroism microscopy measures direct differential absorption of left- and right-circularly polarized light by a chiral nanoobject and thus can measure a pure circular dichroism signal, which is free from the contribution of circular birefringence and linear dichroism. Photothermal magnetic circular dichroism, which is based on the polar magneto-optical Kerr effect, can probe the magnetic properties of a single nanoparticle (of sizes down to 20 nm) optically. Single-particle measurements enable studies of the spatiotemporal heterogeneity of magnetism at the nanoscale. Both PT CD and PT MCD have already found applications in chiral plasmonics and magnetic nanomaterials. Most importantly, the advent of these microscopic techniques opens possibilities for many novel applications in biology and nanomaterial science.

Metal Clusters Confined in Chiral Zeolitic Imidazolate Framework for Circularly Polarized-Luminescence Inks.

Chiroptical activities arising in nanoclusters (NCs) are emerging as one of the most dynamic areas of modern science. However, devising an overarching strategy that is capable of concurrently enhancing the photoluminescence (PL) and circularly polarized luminescence (CPL) of metal NCs remains a formidable challenge. Herein, gold and silver nanoclusters (AuNCs, AgNCs) are endowed with CPL, for the first time, through a universal host-guest approach─centered around perturbing a chiral microenvironment within chiral hosts, simultaneously enhancing emissions. Remarkably, the photoluminescence quantum yield (PLQY) of AuNCs has undergone an increase of over 200 times upon confinement, escalating from 0.05% to 12%, and demonstrates a CPL response. Moreover, a three-dimensional (3D) model termed "NCs@CMOF" featuring CPL activity is created using metal cluster-based assembly inks through the process of 3D printing. This work introduces a potentially straightforward and versatile approach for achieving both PL enhancement and CPL activities in metal clusters.

Ultrafast Polarization-Resolved Phonon Dynamics in Monolayer Semiconductors.

Monolayer transition metal dichalcogenide semiconductors exhibit unique valleytronic properties interacting strongly with chiral phonons that break time-reversal symmetry. Here, we observed the ultrafast dynamics of linearly and circularly polarized E'(Γ) phonons at the Brillouin zone center in single-crystalline monolayer WS2, excited by intense, resonant, and polarization-tunable terahertz pulses and probed by time-resolved anti-Stokes Raman spectroscopy. We separated the coherent phonons producing directional sum-frequency generation from the incoherent phonon population emitting scattered photons. The longer incoherent population lifetime than what was expected from coherence lifetime indicates that inhomogeneous broadening and momentum scattering play important roles in phonon decoherence at room temperature. Meanwhile, the faster depolarization rate in circular bases than in linear bases suggests that the eigenstates are linearly polarized due to lattice anisotropy. Our results provide crucial information for improving the lifetime of chiral phonons in two-dimensional materials and potentially facilitate dynamic control of spin-orbital polarizations in quantum materials.

Dichroism of plasmonic chiral nanoalloys by rational design.

Time-dependent density functional theory (TDDFT) simulations are conducted on a series of chiral gold/silver alloy nanowires to explore whether silver doping can produce an enhancement of circular dichroism at the plasmon resonance in these systems, and to identify the quantum-mechanical origin of the observed effects. We find a strong plasmonic dichroism when one or two helixes of gold atoms are substituted by silver in a linear chiral nanotube, whose pure gold counterpart does not display any plasmonic dichroism, and we rationalize this finding in terms of "decoupling" the destructive interference of excitations in the pure gold nanotube via alloying. However, further attempts to increase the plasmonic dichroism by considering multi-shell gold nanowires in which one entire shell is doped with silver did not produce the desired effect, but rather a decrease in circular dichroism. We show that this latter result is due to a more severe destructive interference in the dipole excitation contributions, and suggest that further amplification should be possible in principle by properly tuning simultaneously the nanowire structure and chemical ordering.

Response of the mechanical and chiral character of ethane to ultra-fast laser pulses.

A pair of simulated left and right circularly polarized ultra-fast laser pulses of duration 20 femtoseconds that induce a mixture of excited states are applied to ethane. The response of the electron dynamics is investigated within the next generation quantum theory of atoms in molecules (NG-QTAIM) using third-generation eigenvector-trajectories which are introduced in this work. This enables an analysis of the mechanical and chiral properties of the electron dynamics of ethane without needing to subject the C-C bond to external torsions as was the case for second-generation eigenvector-trajectories. The mechanical properties, in particular, the bond-flexing and bond-torsion were found to increase depending on the plane of the applied laser pulses. The bond-flexing and bond-torsion, depending on the plane of polarization, increases or decreases after the laser pulses are switched off. This is explainable in terms of directionally-dependent effects of the long-lasting superpositions of excited states. The chiral properties correspond to the ethane molecule being classified as formally achiral consistent with previous NG-QTAIM investigations. Future planned investigations using ultra-fast circularly polarized lasers are briefly discussed.

Chiral CuxCoyS-CuzS Nanoflowers with Bioinspired Enantioselective Catalytic Performances.

Nanomaterials with biomimetic catalytic abilities have attracted significant attention. However, the stereoselectivity of natural enzymes determined by their unique configurations is difficult to imitate. In this work, a kind of chiral CuxCoyS-CuzS nanoflowers (L/D-Pen-NFs) is developed, using porous CuxCoyS nanoparticles (NPs) as stamens, CuzS sheets as petals, and chiral penicillamine as surface stabilizers. Compared to the natural laccase enzyme, L/D-Pen-NFs exhibit significant advantages in catalytic efficiency, stability against harsh environments, recyclability, and convenience in construction. Most importantly, they display high enantioselectivity toward chiral neurotransmitters, which is proved by L- and D-Pen-NFs' different catalytic efficiencies toward chiral enantiomers. L-Pen-NFs are more efficient in catalyzing the oxidation of L-epinephrine and L-dopamine compared with D-Pen-NFs. However, their catalytic efficiency in oxidizing L-norepinephrine and L-DOPA is lower than that of D-Pen-NFs. The reason for the difference in catalytic efficiency is the distinct binding affinities between CuxCoyS-CuzS nano-enantiomers and chiral molecules. This work can spur the development of chiral nanostructures with biomimetic functions.