High Structural Symmetry Research Articles

Harnessing the Unconventional Cubic Phase in 2D LaNiO3 Perovskite for Highly Efficient Urea Oxidation

AbstractPhase engineering is a critical strategy in electrocatalysis, as it allows for the modulation of electronic, geometric, and chemical properties to directly influence the catalytic performance. Despite its potential, phase engineering remains particularly challenging in thermodynamically stable perovskites, especially in a 2D structure constraint. Herein, we report phase engineering in 2D LaNiO3 perovskite using the strongly non‐equilibrium microwave shock method. This approach enables the synthesis of conventional hexagonal and unconventional trigonal and cubic phases in LaNiO3 by inducing selective phase transitions at designed temperatures, followed by rapid quenching to allow precise phase control while preserving the 2D porous structure. These phase transitions induce structural distortions in the [LaO]+ layers and the hybridization between Ni 3d and O 2p states, modifying local charge distribution and enhancing electron transport during the six‐electron urea oxidation process (UOR). The cubic LaNiO3 offers optimal electron transport and active site accessibility due to its high structural symmetry and open interlayer spacing, resulting in a low onset potential of 1.27 V and a Tafel slope of 33.1 mV dec−1 for UOR, outperforming most current catalysts. Our strategy features high designability in phase engineering, enabling various electrocatalysts to harness the power of unconventional phases.

Harnessing the Unconventional Cubic Phase in 2D LaNiO3 Perovskite for Highly Efficient Urea Oxidation

AbstractPhase engineering is a critical strategy in electrocatalysis, as it allows for the modulation of electronic, geometric, and chemical properties to directly influence the catalytic performance. Despite its potential, phase engineering remains particularly challenging in thermodynamically stable perovskites, especially in a 2D structure constraint. Herein, we report phase engineering in 2D LaNiO3 perovskite using the strongly non‐equilibrium microwave shock method. This approach enables the synthesis of conventional hexagonal and unconventional trigonal and cubic phases in LaNiO3 by inducing selective phase transitions at designed temperatures, followed by rapid quenching to allow precise phase control while preserving the 2D porous structure. These phase transitions induce structural distortions in the [LaO]+ layers and the hybridization between Ni 3d and O 2p states, modifying local charge distribution and enhancing electron transport during the six‐electron urea oxidation process (UOR). The cubic LaNiO3 offers optimal electron transport and active site accessibility due to its high structural symmetry and open interlayer spacing, resulting in a low onset potential of 1.27 V and a Tafel slope of 33.1 mV dec−1 for UOR, outperforming most current catalysts. Our strategy features high designability in phase engineering, enabling various electrocatalysts to harness the power of unconventional phases.

High color purity aluminate phosphor SryCa1-x-yAl12O19: xEu2+ for lighting and backlight display applications

In the context of the rapid advances in electronic information technology, the advancement of novel high-efficiency narrow-band blue phosphors represents a pivotal step in the advancement of high-quality liquid crystal displays (LCDs), as well as the development of white light-emitting diodes (WLEDs) with a reduced correlated color temperature (CCT). In this study, based on the sensitivity of Eu2+ emission to local environment, the alkaline earth aluminate material CaAl12O19 with high structural symmetry was selected as the matrix, and the symmetry of crystal structure was improved by replacing Ca2+ with Sr2+, the narrow-band emission of the phosphor is realized. The Sr0.9Ca0.09Al12O19: 0.01Eu2+ (SCAO: Eu2+) phosphor exhibited narrow-band emission with the full width at half maximum (FWHM) of 45.76 nm, and the colour purity of up to 95.46 %. Moreover, the internal quantum efficiency (IQE) of SCAO: Eu2+ has been demonstrated to reach 81.70 %. In addition, SCAO: Eu2+ phosphor, (Ba, Sr)2SiO4: Eu2+ phosphor, CaAlSiN3: Eu2+ phosphor, and 275 nm UVLED chips were combined to prepare white LED devices exhibiting a low color temperature (3733 K). The three-band LEDs of SCAO: Eu2+, β-Sialon: Eu2+ and K2SiF6: Mn4+ exhibited a colour gamut covering 84.75 % of the National Television Standards Committee (NTSC) standard. This indicates that the phosphor possesses the characteristics of a highly effective narrow-band blue-light-emitting substance with considerable potential for utilization in lighting and backlighting displays.

Internal-locking relativistic magnetron in transversely opposed driven scheme

A cascaded relativistic magnetron array with symmetric feeder structure was first proposed as a multi-port phase-coherent high-power microwave source, which is intrinsically equipped with high structural symmetry. Two symmetrically positioned slow-wave structures surround the feeder structure, which reduces axial electron drifting in each resonant system and ensures the phase-locking process. In this paper, a theory of structure-provided coupling coefficient and oscillator-required coupling coefficient is proposed as the phase-locking prerequisites. The method is evaluated by adopting two A6-type resonant systems. The symmetrically driven cascaded relativistic magnetron array employs a typical π-mode with an anode voltage of 450 kV and an axial magnetic field of 0.47 T. The phase-locked state was achieved in 17 ns with a jitter less than 5 deg. The total output power exceeds 2.3 GW at a frequency of 2.15 GHz, and the power flow in each output port exceeds 350 MW. The transversely opposed driven scheme can be combined with other phase-locking patterns for additional uses, and further optimization of resonant system could be applied for enhancing device performance. The theory of coupling prerequisites is also sufficient for analyzing other cascaded relativistic magnetrons.

Organic radical ferroelectric crystals with martensitic phase transition

Organic martensitic compounds are an emerging type of smart material with intriguing physical properties including thermosalient effect, ferroelasticity, and shape memory effect. However, due to the high structural symmetry and limited design theories for these materials, the combination of ferroelectricity and martensitic transformation has rarely been found in organic systems. Here, based on the chemical design strategies for molecular ferroelectrics, we show a series of asymmetric 1,4,5,8-naphthalenediimide derivatives with the homochiral amine and 2,2,6,6-tetramethylpiperidine-N-oxyl components, which adopt the low-symmetric polar structure and so allow ferroelectricity. Upon H/F substitution, the fluorinated compounds exhibit reversible ferroelectric and martensitic transitions at 399 K accompanied by a large thermal hysteresis of 132 K. This large thermal hysteresis with two competing (meta)-stable phases is further confirmed by density functional theory calculations. The rare combination of martensitic phase transition and ferroelectricity realizes the bistability with two different ferroelectric phases at room temperature. Our finding provides insight into the exploration of martensitic ferroelectric compounds with potential applications in switchable memory devices, soft robotics, and smart actuators.

Gigantic Anisotropy of Self-Induced Spin-Orbit Torque in Weyl Ferromagnet Co2MnGa.

Spin-orbit torque (SOT) is receiving tremendous attention from both fundamental and application-oriented aspects. Co2MnGa, a Weyl ferromagnet that is in a class of topological quantum materials, possesses cubic-based high structural symmetry, the L21 crystal ordering, which should be incapable of hosting anisotropic SOT in conventional understanding. Here we show the discovery of a gigantic anisotropy of self-induced SOT in Co2MnGa. The magnitude of the SOT is comparable to that of heavy metal/ferromagnet bilayer systems, despite the high inversion symmetry of the Co2MnGa structure. More surprisingly, a sign inversion of the self-induced SOT is observed for different crystal axes. This finding stems from the interplay of the topological nature of the electronic states and their strong modulation by external strain. Our research enriches the understanding of the physics of self-induced SOT and demonstrates a versatile method for tuning SOT efficiencies in a wide range of materials for topological and spintronic devices.

Attachment of Virus to Host Cell Surface upon Specific Binding to Membrane Receptors and Attachment Factors

Viruses are spherical particles of size 50–500 nm. The genome (DNA or RNA) of viruses is typically encapsulated by a protein shell, known as, capsid which is further coated by a protein-rich lipid bilayer for enveloped viruses. Most non-enveloped viruses have a rigid capsid with a high structural symmetry such as icosahedral, helical, and complex. The capsid and envelope proteins are part of the structural proteins of viruses and provide distinct structural features. A major function of these structural proteins is determining the binding of viruses to host cells and these structural proteins are the most exposed on the viral surface. While viruses are simple biological nanoparticles devoid of genetic machinery, they can replicate once they enter a host cell. This is a multistep process starting with the interaction of the viral surface proteins with specific molecules of a cell surface. It is well established that virus particles must evade or cross through the 1.5-μm-thick proteoglycan shield surrounding a cell to reach the plasma membrane of the cell. Viruses have evolved to interact with the proteoglycans and receptors of the plasma membrane to trigger signals for endocytosis or membrane fusion, processes essential for cellular entry (Figure 1). Despite the fact that viruses can intrude multiple tissues and organs of a host, the infection predominates in specific organs and cell types. This is determined by the specific interaction of the viral surface proteins with the proteoglycans and plasma membrane receptors.

Physics guided deep learning for generative design of crystal materials with symmetry constraints

Discovering new materials is a challenging task in materials science crucial to the progress of human society. Conventional approaches based on experiments and simulations are labor-intensive or costly with success heavily depending on experts’ heuristic knowledge. Here, we propose a deep learning based Physics Guided Crystal Generative Model (PGCGM) for efficient crystal material design with high structural diversity and symmetry. Our model increases the generation validity by more than 700% compared to FTCP, one of the latest structure generators and by more than 45% compared to our previous CubicGAN model. Density Functional Theory (DFT) calculations are used to validate the generated structures with 1869 materials out of 2000 are successfully optimized and deposited into the Carolina Materials Database www.carolinamatdb.org, of which 39.6% have negative formation energy and 5.3% have energy-above-hull less than 0.25 eV/atom, indicating their thermodynamic stability and potential synthesizability.

Unconventional short-range structural fluctuations in cuprate superconductors

The interplay between structural and electronic degrees of freedom in complex materials is the subject of extensive debate in physics and materials science. Particularly interesting questions pertain to the nature and extent of pre-transitional short-range order in diverse systems ranging from shape-memory alloys to unconventional superconductors, and how this microstructure affects macroscopic properties. Here we use neutron and X-ray diffuse scattering to uncover universal structural fluctuations in La2-xSrxCuO4 and Tl2Ba2CuO6+δ, two cuprate superconductors with distinct point disorder effects and with optimal superconducting transition temperatures that differ by more than a factor of two. The fluctuations are present in wide doping and temperature ranges, including compositions that maintain high average structural symmetry, and they exhibit unusual, yet simple scaling behaviour. The scaling regime is robust and universal, similar to the well-known critical fluctuations close to second-order phase transitions, but with a distinctly different physical origin. We relate this behaviour to pre-transitional phenomena in a broad class of systems with structural and magnetic transitions, and propose an explanation based on rare structural fluctuations caused by intrinsic nanoscale inhomogeneity. We also uncover parallels with superconducting fluctuations, which indicates that the underlying inhomogeneity plays an important role in cuprate physics.

Electronic and Optical Properties of BP, InSe Monolayer and BP/InSe Heterojunction with Promising Photoelectronic Performance.

Two-dimensional (2D) materials provide a new strategy for developing photodetectors at the nanoscale. The electronic and optical properties of black phosphorus (BP), indium selenide (InSe) monolayer and BP/InSe heterojunction were investigated via first-principles calculations. The geometric characteristic shows that the BP, InSe monolayer and BP/InSe heterojunction have high structural symmetry, and the band gap values are 1.592, 2.139, and 1.136 eV, respectively. The results of band offset, band decomposed charge and electrostatic potential imply that the heterojunction structure can effectively inhibit the recombination of electron–-hole pairs, which is beneficial for carrier mobility of photoelectric devices. Moreover, the optical properties, including refractive index, reflectivity, electron energy loss, extinction coefficient, absorption coefficient and photon optical conductivity, show excellent performance. These findings reveal the optimistic application potential for future photoelectric devices. The results of the present study provide new insight into challenges related to the peculiar behavior of the aforementioned materials with applications.

Toward Nanomolar Multi-Component Analysis by 19F NMR.

The widespread application of nuclear magnetic resonance (NMR) spectroscopy in detection is currently hampered by its inherently low sensitivity and complications resulting from the undesired signal overlap. Here, we report a detection scheme to address these challenges, where analytes are recognized by 19F-labeled probes to induce characteristic shifts of 19F resonances that can be used as "chromatographic" signatures to pin down each low-concentration analyte in complex mixtures. This unique signal transduction mechanism allows detection sensitivity to be enhanced by using massive chemically equivalent 19F atoms, which was achieved through the proper installation of nonafluoro-tert-butoxy groups on probes of high structural symmetry. It is revealed that the binding of an analyte to the probe can be sensed by as many as 72 chemically equivalent 19F atoms, allowing the quantification of analytes at nanomolar concentrations to be routinely performed by NMR. Applications on the detection of trace amounts of prohibited drug molecules and water contaminants were demonstrated. The high sensitivity and robust resolving ability of this approach represent a first step toward extending the application of NMR to scenarios that are now governed by chromatographic and mass spectrometry techniques. The detection scheme also makes possible the highly sensitive non-invasive multi-component analysis that is difficult to achieve by other analytical methods.

Femtosecond laser inscribed helical sapphire fiber Bragg gratings.

This Letter reports a novel helical sapphire fiber Bragg grating (HSFBG) in a single crystal sapphire fiber with diameter of 60 µm fabricated by a 515 nm femtosecond laser. Due to the large refractive index modulation region and high structural symmetry of the HSFBGs, high-reflectivity and high-quality spectra can be prepared and additionally have good bending resistance. The spectral properties of HSFBGs with different helical diameters are studied. When the helical diameter is 30 µm, the reflectivity of HSFBG is 40%, the full width at half-maximum is 1.56 nm, and the signal-to-noise ratio is 16 dB. For the HSFBG bending test, the minimum bending radius is 5 mm, which can still maintain relatively good spectral quality. In addition, the HSFBG array with different periods has been successfully cascaded in a sapphire fiber. The experimental results of the HSFBG high-temperature test show that this HSFBG can work reliably at 1600°C, and the temperature sensitivity in the high-temperature range can reach 35.55 pm/°C. This HSFBG can be used in high-temperature and harsh environments, such as metal smelting and aeroengine structural health monitoring.

Highly Sensitive and Reliable NIR Luminescent Sensing Toward Nitro‐Aromatic Antibiotics in Water

AbstractNear‐infrared (NIR) light features less photon scatter and deeper penetration, thereby providing a sensitive and reliable platform for qualifying and quantifying trace organic contaminants in water medium. Herein, a lanthanide/β‐diketone complex, Yb(dmh)3(phen) (dmh = 2,6‐dimethyl‐3,5‐heptanedione, phen = 1,10‐phenanthroline), is synthesized and performs characteristic NIR luminescence of Yb3+ ions. The outstanding photophysical properties result from the combination effects of excited‐state inter‐ligand charge transfer, ligand‐to‐metal energy transfer, and high structural symmetry. Noteworthily, this NIR luminophore exhibits state‐of‐the‐art sensitivity toward nitro‐aromatic antibiotics in water. The limits of detection are lower to sub‐nanomolar level for nitroimidazoles (metronidazole 0.18 nM; dimetridazole 0.23 nM; ornidazole 0.28 nM) and even picomolar level for nitrofurans (nitrofurantoin 43 pM; nitrofurazone 46 pM). This exciting sensitivity attributes to photo‐induced electron transfer and inner filter effect between sensor and adsorbed analytes. The sensor is also capable of distinguished stability, selectivity, competitiveness, and anti‐interference, which makes it far better suited to the commercial application. The successfully developed technique of NIR luminescence sensing extends the platform of optical devices and sensing materials, being of practical value in monitoring water quality.

Three‐Dimensional Graphene Network Decorated with Highly Symmetrical Cuboid Na3V2(PO4)2F3 Particles: High Rate Capability and Cycling Stability for Sodium‐Ion Batteries

AbstractNa3V2(PO4)2F3 (NVPF) has captured significant heed for cathode materials of sodium‐ion battery (SIB), owing to its stable three‐dimensional (3D) structure channel that can accommodate Na+ diffusion. However, NVPF is still facing with a major challenge in terms of the electrochemical performance, owing to its uncontrollable morphology. Hence, it was fabricated by using a two‐step hydrothermal method, whereby NVPF cuboid particles of homogenous morphology and highly structural symmetry could anchor on the three‐dimensional graphene network (GN) structure to form NVPF@GN. The affiliation between the morphology and performance of the NVPF@GN was further probed by manipulating the morphology of the NVPF under diverse heat treatment temperatures. When the temperature reaches 480 °C, NVPF@GN manifests prolonged cyclability (the capacity fading rate of 0.01 % cycle−1 at 0.5 C during 300 cycles) and it shows outstanding rate performance (when the rate is reset to 0.5 C, the capacity is 107 mAh g−1 and capacity retention is 99 %), which can be ascribed to the high structural symmetry of NVPF@GN. These results indicate that NVPF@GN cuboids can be used as a prospective cathode material for SIBs.

Gap-enhanced toroidal dipole and magnetic Fano resonances with polarization independence in all-dielectric metamaterials for sensing

We have designed and numerically analyzed gap-enhanced toroidal dipole (TD) and magnetic Fano resonances with high Q-factors and large modulation depths simultaneously in an all-dielectric metamaterial for sensing. By introducing a gap in the cylinder, we achieved a significant enhancement in Q-factor and electromagnetic field compared to the cylinder with no gap in near-IR regime. In addition, TD and magnetic Fano resonances can be tailored through varying width and position of gap and can be achieved without symmetry breaking, showing polarization-independent characteristics. Further, we theoretically demonstrated a multichannel refractive index (RI) sensor with bulk RI sensitivity exceeding 100 nm / RIU and figure of merit reaching 260. With high structural symmetry of the proposed metamaterial, it may find applications in lasing, nonlinear devices, and multiwavelength biomedical sensing.

Computational discovery of molecular C60 encapsulants with an evolutionary algorithm

Computation is playing an increasing role in the discovery of materials, including supramolecular materials such as encapsulants. In this work, a function-led computational discovery using an evolutionary algorithm is used to find potential fullerene (C60) encapsulants within the chemical space of porous organic cages. We find that the promising host cages for C60 evolve over the simulations towards systems that share features such as the correct cavity size to host C60, planar tri-topic aldehyde building blocks with a small number of rotational bonds, di-topic amine linkers with functionality on adjacent carbon atoms, high structural symmetry, and strong complex binding affinity towards C60. The proposed cages are chemically feasible and similar to cages already present in the literature, helping to increase the likelihood of the future synthetic realisation of these predictions. The presented approach is generalisable and can be tailored to target a wide range of properties in molecular material systems.

High‐Performance Manganese Hexacyanoferrate with Cubic Structure as Superior Cathode Material for Sodium‐Ion Batteries

AbstractSodium manganese hexacyanoferrate (NaxMnFe(CN)6) is one of the most promising cathode materials for sodium‐ion batteries (SIBs) due to the high voltage and low cost. However, its cycling performance is limited by the multiple phase transitions during Na+ insertion/extraction. In this work, a facile strategy is developed to synthesize cubic and monoclinic structured NaxMnFe(CN)6, and their structure evolutions are investigated through in situ X‐ray diffraction (XRD), ex situ Raman, and X‐ray photoelectron spectroscopy (XPS) characterizations. It is revealed that the monoclinic phase undergoes undesirable multiple two‐phase reactions (monoclinic ↔ cubic ↔ tetragonal) due to the large lattice distortions caused by the Jahn–Teller effects of Mn3+, resulting in poor cycling performances with 38% capacity retention. The cubic NaxMnFe(CN)6 with high structural symmetry maintains the structural stability during the repeated Na+ insertion/extraction process, demonstrating impressive electrochemical performances with specific capacity of ≈120 mAh g−1 at 3.5 V (vs Na/Na+), capacity retention of ≈70% over 500 cycles at 200 mA g−1. In addition, the TiO2//C‐MnHCF full battery is fabricated with an energy density of 111 Wh kg−1, suggesting the great potential of cubic NaxMnFe(CN)6 for practical energy storage applications.

Three-dimensional fractal structure with double negative and density-near-zero properties on a subwavelength scale

We constructed a three-dimensional fractal acoustic metamaterial using the combination of zigzag channels and Menger fractal structures that had high structural symmetry and could extend into 3D space easily. Reflection and transmission coefficients were numerically calculated and experimentally measured, and the results matched well with each other. Using the finite element method and the S-parameter retrieval method, the band structures, the equivalent frequency surface and the effective parameters of the acoustic metamaterial were calculated. The results showed that the 3D acoustic metamaterial had double negative property in the normalized frequency range of 0.205–0.269 and density-near-zero property in the normalized frequency vicinity of 0.356. A plate lens model and a quarter-bending model were constructed to demonstrate the double negative property and the density-near-zero property of the acoustic metamaterial, respectively. These results showed that the 3D acoustic metamaterial could achieve excellent acoustic properties and would be promising to construct the 3D double negative structure and control acoustic waves on a subwavelength scale within a single unit.

Polarization and angle independent magneto-electric Fano resonance in multilayer hetero-nanoshells

In this work, we have demonstrated that the Si–SiO2 –Au multilayer hetero-nanoshells can support the polarization and angle independent magneto-electric Fano resonance. Such Fano resonance arises from the direct destructive interference between the orthogonal electric dipole mode of Au core and magnetic dipole mode of the Si shell and is independent of the angle due to the high structural symmetry. In contrast to metal particle arrays, here is a possibility to generate controllable interaction between the electric and magnetic dipole resonances of individual nanoshell with the structural features. The discrete magnetic responses provided directly by the Si shell pave the groundwork for designing the magnetic responses at optical frequencies and enable many fascinating applications in nanophotonics.

Symmetry-Controlled Structural Phase Transition Temperature in Chromium-Doped Vanadium Dioxide

Understanding the key factor controlling phase transitions of correlated oxides by chemical doping is becoming of fundamental and technological interest. Here, we report vanadium chain symmetry as an effective means of mediating the structural phase transition (SPT) temperature in hydrothermal Cr-doped VO2. In-situ X-ray absorption fine structure spectroscopy unveils that high structural symmetry with equidistant 2.93 A V–V zigzag chains, along with the dimerized V–V straight chain induced by Cr-doping, can stabilize VO2 at elevated temperature, thus raising the critical temperature of the VO2 phase transition. The Cr-doped VO2 system exhibited a SPT process involving lattice expansion, accompanied by V–V chain reconstruction into the rutile phase. These findings provide novel insights and guidance in chemically tailoring the phase transition of VO2.