Polar Crystals Research Articles

Zipper‐Like Dynamic Switching of Coordination Bonds Gives a Polar Bimetallic Halide toward Self‐Driven X‐ray Detection

Polar molecular crystals hold a promise for controlling bulk physical properties originated in their unique switchable polarity via structural transformation. However, the mechanisms for switching polarization are mainly limited to displacive and disorder‐order phase transitions, which rarely involve the reconstruction of chemical bonds. Here, we have switched and tuned electric polarization in a bimetallic halide, (Neopentylammonium)4AgBiBr8 (1), as verified by light‐excited pyroelectric effect. Most notably, its Ag‐Br coordination bonds show a zipper‐like dynamic switching behavior from the ‘locked’ to ‘unlocked’ state, namely, reconstruction of chemical bonds. Coupling with the dynamic ordering of organic cations, this bond‐switching transition makes a contribution to switchable polarization of 1. As expected, its polarity creates pyroelectric effect for self‐driven X‐ray detection with high sensitivity (3.8×103 μC Gy‐1 cm‐2) and low limit of detection (4.8 nGy s‐1). This work on the bond‐switching mechanism provides an avenue to design polar molecular candidate for smart optoelectronic devices.

Zipper-Like Dynamic Switching ofCoordinationBonds GivesaPolar Bimetallic Halidetoward Self-Driven X-ray Detection.

Polar molecular crystals hold a promise for controlling bulk physical properties originated intheir unique switchable polarity viastructural transformation.However, the mechanisms for switching polarization are mainly limited to displacive and disorder-order phase transitions, which rarelyinvolve thereconstruction of chemical bonds. Here, we have switchedand tuned electric polarizationina bimetallic halide, (Neopentylammonium)4AgBiBr8(1), as verified by light-excited pyroelectric effect. Most notably, its Ag-Br coordination bonds show a zipper-like dynamic switching behavior from the 'locked'to 'unlocked'state, namely, reconstruction of chemical bonds.Coupling with the dynamic ordering of organic cations,this bond-switching transitionmakes a contribution to switchable polarization of 1. As expected, its polaritycreates pyroelectric effectfor self-driven X-ray detectionwithhighsensitivity (3.8×103μC Gy-1cm-2) and low limitof detection(4.8 nGy s-1). This work onthe bond-switching mechanism provides an avenue to designpolar molecularcandidatefor smart optoelectronic devices.

Tunable spatial shifts of reflected beam from a polar crystal film sandwiched by dual-twisted black phosphorus gratings

Tunable spatial shifts of reflected beam from a polar crystal film sandwiched by dual-twisted black phosphorus gratings

Breakdown of Volterra's Elasticity Theory of Dislocations in Polar Skyrmion Lattices.

Emerging polar skyrmion crystals (SkX) have raised much interest for technological applications owing to their nontrivial topologies of electric dipoles, quasiparticle-like behaviors, and unique electrical responses. Understanding SkX defects, especially dislocations, is crucial for their unique lattice dynamics and responses; however, it still remains elusive. Here, we have not only demonstrated that a SkX dislocation exhibits an anomalously deformed core structure with over 50% elongation of skyrmions but also discovered that Volterra's elasticity theory of dislocation is broken down in SkX. Our phase-field simulation reveals that these distinct features of SkX dislocation arise from a rigid to soft quasiparticle transition of skyrmions depending on the electric field and temperature. In SkX, there exist inherent mechanics that mitigate the mismatch by both migration and deformation of skyrmions. This work provides novel insights into a new class of lattice mechanics and related functionality arising from the unique properties of quasi-particle SkX.

Oriented Crystal Polarization Tuning Bulk Charge and Single-Site Chemical State for Exceptional Hydrogen Photo-Production.

Rapid bulk charge recombination and mediocre surface catalytic sites harshly restrict the photocatalytic activities. Herein, the aforementioned concerns are well addressed by coupling macroscopic spontaneous polarization and atomic-site engineering of CdS single-crystal nanorods for superb H2 photo-production. The oriented growth of CdS nanorods along the polar axis, vectorially superimposing substantial polar units with orderly arrangement, renders a strong polarization electric field (20.1 times enhancement), which boosts bulk charge separation with an efficiency up to 72.4% (80.4-fold). Remarkably, polarization electric field alters the chemical state of Pt single sites by orderly reducing the binding energy of Pt atom with stepwise polarization enhancement of CdS substrate, which increases the onsite electron density of Pt from 10.232 to 10.261e- and *H key intermediates, providing preponderant Volmer-Tafel/Volmer-Heyrovsky reaction pathways with significantly decreased energy barriers for H2 production. Thus, highly polarized CdS nanorods with atomically dispersed Pt sites perform an outstanding H2 space-time yield of 118.5mmol g-1 h-1 and apparent quantum efficiency of 57.7% at λ = 420nm, and a record-high H2 turnover frequency of 57798.4 h-1, being one of the best catalysts for photocatalytic H2 evolution. This work highlights the function of polarization in manipulating charge separation and catalytic reaction.

Ultra-compact and high-precision differential detection method based on liquid crystal polarization grating for miniature atomic magnetometer

Ultra-compact and high-precision differential detection method based on liquid crystal polarization grating for miniature atomic magnetometer

Synthesis, characterization and evaluation of optically active polar semi-organic glycine-cobalt chloride crystals

Synthesis, characterization and evaluation of optically active polar semi-organic glycine-cobalt chloride crystals

Fabrication of hydrothermal PPKTP and its spontaneous parametric down-conversion characteristics

High-voltage electric field polarization, selective corrosion, current monitoring, and other methods are used to develop hydrothermal PPKTP. It is found that the reversal domain nucleation of hydrothermal-grown KTP crystals has four kinds of microscopic morphology, namely, strip shape, spindle shape, bullet shape and irregular shape, in the process of high voltage electric field polarization. Compared with the leakage current in the process of polarization of flux-grown KTP crystals, the hydrothermal-grown KTP crystals only exist when the applied electric field is much larger than the coercive field. The leakage current can be suppressed by multiple loading of short pulses, and the PPKTP with a poled period of 10 μm and 46 μm were fabricated, respectively. Subsequently, based on the fabricated PPKTP, the SPDC characteristics are studied. To the PPKTP with a poled period of 10 μm, the quantum entanglement source whose brightness exceeds 2.1 kHz @ 810 nm is prepared by the SPDC technique. Otherwise, the PPKTP with a poled period of 46 μm is used for SPDC, and the brightness of entangled photon pairs in channel 1 and channel 2 are 3.21 kHz @ 1560 nm and 5.31 kHz @ 1560 nm, respectively.

Robust optical singularity detection enabled by spin-synchronized shearing interference

Singular beams carrying phase and polarization singularities have been extensively studied for applications in optical communication, quantum information processing, optical imaging, and other fields. However, developing a robust method to detect optical singularity that is insensitive to wavelength, polarization, and illumination position remains a significant challenge. In this study, we propose and demonstrate a robust optical singularity detection scheme based on spin-synchronized shearing interference (SSSI) using spin-dependent gradient phase modulation of a quarter-wave liquid–crystal polarization grating. Since the spin-dependent gradient phase modulation of the polarization grating is wavelength-independent, and the two circular bases of the incident field can be measured simultaneously, the proposed method is robust to wavelength and polarization. Additionally, we have verified that SSSI performs well in detecting multi-singularity cylindrical vector beam. This work provides a practical and straightforward scheme for robust optical singularity detection.

Design and fabrication of an achromatic liquid crystal polarization grating with large deflection angle for visible wavelength

Design and fabrication of an achromatic liquid crystal polarization grating with large deflection angle for visible wavelength

Nonsymmetrical thermal conductivity along the director field in ferroelectric nematic liquid crystals.

The synthesis of ferroelectric nematic liquid crystals (FNLCs) concludes the long wait for their existence and potential usage in multiple liquid crystal based applications. In FNLCs, electric polarization in the nematic phase significantly decreases the switching time of in-on display pixels. In this article, we report the occurrence of translation symmetry breaking for heat propagation along the director field n[over ̂] in the ferroelectric nematic phase. Due to the C_{∞V} symmetry of such a phase and close similarity to the bent-core polar liquid crystal phase, a rank-3 tensor describes its scalar order parameter and algebraic deductions. The finite element simulations show the occurrence of the nonsymmetrical thermal conductivity along n[over ̂]. The preferential heat transport in FNLCs can allow them to work as an all-thermal monophase non-nanostructured single-material thermal rectifier. We expect that this study will contribute towards the FNLCs application as functional layers and inks.

Compact binocular holographic near-eye 3D display system based on a liquid crystal polarization grating

Holographic technology is considered as one of the most ideal 3D display technologies and has significant potential in near-eye display. However, binocular holographic near-eye 3D display still faces challenges such as serious visual fatigue and complex system. Here, we propose a compact binocular holographic near-eye 3D display system based on a liquid crystal polarization grating (LCPG). Based on the LCPG, the reconstructed light can be deflected respectively to left and right viewing areas. The proposed system achieves binocular display with only one phase-only spatial light modulator used to load computer-generated hologram, which makes the binocular display system more compact. Simultaneously, the proposed system reduces mismatches in the images perceived by two eyes, thus achieving a better binocular display effect. Experimental results demonstrate the feasibility of the proposed binocular holographic near-eye 3D display system with dual viewing areas. Additionally, based on the time-division multiplexing method, dynamic binocular holographic near-eye display can be achieved. The proposed system has potential applications in holographic virtual reality and augmented reality display.

Triggering Overall Crystal Polarization by Octahedron Elongation Distortion for Highly Boosted and Selective Aerobic Photo‐Oxidation

Triggering Overall Crystal Polarization by Octahedron Elongation Distortion for Highly Boosted and Selective Aerobic Photo‐Oxidation

Exo-6b2-Methyl-Substituted Pentabenzocorannulene: Synthesis, Structural Analysis, and Properties.

exo-6b2-Methyl-substituted pentabenzocorannulene (exo-PBC-Me) was synthesized by the palladium-catalyzed cyclization of 1,2,3-triaryl-1H-cyclopenta[l]phenanthrene. Its bowl-shaped geometry with an sp3 carbon atom in the backbone and a methyl group located at the convex (exo) face was verified by X-ray crystallography. According to DFT calculations, the observed conformer is energetically more favorable than the endo one by 39.9 kcal/mol. Compared to the nitrogen-doped analogs with intact π-conjugated backbones (see the main text), exo-PBC-Me displayed a deeper bowl depth (avg. 1.93 Å), redshifted and broader absorption (250-620 nm) and emission (from 585 to more than 850 nm) bands and a smaller optical HOMO-LUMO gap (2.01 eV). exo-PBC-Me formed polar crystals where all bowl-in-bowl stacking with close π ⋅ ⋅ ⋅ π contacts is arranged unidirectionally, providing the potential for applications as organic semiconductors and pyroelectric materials. This unusual structural feature, molecular packing, and properties are most likely associated with the assistance of the methyl group and the sp3 carbon atom in the backbone.

Exo‐6b2‐Methyl‐Substituted Pentabenzocorannulene: Synthesis, Structural Analysis, and Properties

Abstractexo‐6b2‐Methyl‐substituted pentabenzocorannulene (exo‐PBC‐Me) was synthesized by the palladium‐catalyzed cyclization of 1,2,3‐triaryl‐1H‐cyclopenta[l]phenanthrene. Its bowl‐shaped geometry with an sp3 carbon atom in the backbone and a methyl group located at the convex (exo) face was verified by X‐ray crystallography. According to DFT calculations, the observed conformer is energetically more favorable than the endo one by 39.9 kcal/mol. Compared to the nitrogen‐doped analogs with intact π‐conjugated backbones (see the main text), exo‐PBC‐Me displayed a deeper bowl depth (avg. 1.93 Å), redshifted and broader absorption (250–620 nm) and emission (from 585 to more than 850 nm) bands and a smaller optical HOMO–LUMO gap (2.01 eV). exo‐PBC‐Me formed polar crystals where all bowl‐in‐bowl stacking with close π ⋅ ⋅ ⋅ π contacts is arranged unidirectionally, providing the potential for applications as organic semiconductors and pyroelectric materials. This unusual structural feature, molecular packing, and properties are most likely associated with the assistance of the methyl group and the sp3 carbon atom in the backbone.

Electrically Switchable Transmissive and Reflective Liquid Crystal Polarization Gratings Based on Cholesteric Liquid Crystals

Electrically Switchable Transmissive and Reflective Liquid Crystal Polarization Gratings Based on Cholesteric Liquid Crystals

Supramolecular Assembly of Nitrogen-Containing Curved π-Conjugated Molecules to Polar Crystal

The chemistry of curved π-conjugated molecules has been extensively studied because of the development of their synthetic approach. Among the numerous studies, we have been engaged in nitrogen-containing curved π-conjugated molecules. These molecules have extended optical properties, redox-active behaviors, and electron-donating ability due to the electron-rich nature of nitrogen atoms. Recently, we have focused on the supramolecular assembling behavior of these compounds. For example, we have reported buckycatcher consisted of two azabuckybowls, providing two-photon absorbing host-guest complexes with fullerenes. In this presentation, we would like to show the packing behavior using π-extended azahelicenes and azabuckybowls. Our group has developed π-extended aza[5]helicene derivatives, showing brilliant emissive features. Recently, we succeeded in the synthesis of unsymmetrically substituted azahelicenes. We found that their stackings in the crystal were dependent on the substituent. X-ray diffraction analysis for all products showed π-stacked conformation with each other in the crystal (Figure 1b). In particular, azahelicenes with triisopropylsilyl groupswere found to align their dipole moments to form a one-dimensional columnar structure in the crystal. Polar crystals are expected to have applications in ferroelectric, piezoelectric, and nonlinear optical response materials. This is the first example of a polar crystal with helicenes, paving the way for novel piezoelectric organic materials.The second topic is related to azabuckybowl. In the crystal, azabuckybowl forms a face-to-face dimer by concave-convex interaction. In this study, we prepared two types of azabuckybowl perylene bisimide (PBI) dyads connected with alkyne linkages. PBIs have also been reported to show columnar stacking in solution. We anticipated that the segregate stacking should be achieved by recognizing the difference in structures between the bowl and planar geometry. The UV/vis absorption spectra revealed the presence of intramolecular charge-transfer interaction. In addition, the concentration-dependent absorption spectra and 1H NMR spectra indicated PBI and azabuckybowl units stacked with each other independently in solution (Figure 1a). Here, we would like to discuss about the effect of the effect of molecular shape on the supramolecular assembly with the data obtained using these compounds. Figure 1

Manipulating Ferroelectric Polarization and Spin Polarization of 2D CuInP2S6 Crystals for Photocatalytic CO2 Reduction.

Manipulating electronic polarizations such as ferroelectric or spin polarizations has recently emerged as an effective strategy for enhancing the efficiency of photocatalytic reactions. This study demonstrates the control of electronic polarizations modulated by ferroelectric and magnetic approaches within a two-dimensional (2D) layered crystal of copper indium thiophosphate (CuInP2S6) to boost the photocatalytic reduction of CO2. We investigate the substantial influence of ferroelectric polarization on the photocatalytic CO2 reduction efficiency, utilizing the ferroelectric-paraelectric phase transition and polarization alignment through electrical poling. Additionally, we explore enhancing the CO2 reduction efficiency by harnessing spin electrons through the synergistic introduction of sulfur vacancies and applying a magnetic field. Several advanced characterization techniques, including piezoresponse force microscopy, ultrafast pump-probe spectroscopy, in situ X-ray absorption spectroscopy, and in situ diffuse reflectance infrared Fourier transformed spectroscopy, are performed to unveil the underlying mechanism of the enhanced photocatalytic CO2 reduction. These findings pave the way for manipulating electronic polarizations regulated through ferroelectric or magnetic modulations in 2D layered materials to advance the efficiency of photocatalytic CO2 reduction.

Quarter-wave Pancharatnam-Berry phase gradient liquid crystal-enabled dual-polarization optical edge detection.

Here, we present a novel, to the best of our knowledge, optical edge detection scheme that can be operated in both linear and circular polarization modes, leveraging an optical spatial differentiator constructed by quarter-wave Pancharatnam-Berry (P-B) phase gradient element. After explaining the theoretical mechanism, we utilize a quarter-wave P-B phase liquid crystal polarization grating to validate the dual-polarization optical edge detection capability. We demonstrate that the orientation of linear polarization and the spin of circular polarization dictate the transition between edge and bright-field images. Besides, the linear and circular polarization modes exhibit broadband and monochromatic responsive properties, respectively. This mechanism, dependent on wavelength and polarization, holds promise for applications in color image processing, chiral sensing imaging, and polarization-entangled quantum imaging.

Configuration Determination for Chiral and Polar Crystals by Anisotropic NMR Shift

Configuration Determination for Chiral and Polar Crystals by Anisotropic NMR Shift