Theoretical Characterization Research Articles

Finite-size topological phases from semimetals

Topological semimetals are some of the topological phases of matter most intensely studied experimentally. The Weyl semimetal phase, in particular, has garnered tremendous, sustained interest given fascinating signatures such as the Fermi arc surface states and the chiral anomaly, as well as the minimal requirements to protect this three-dimensional (3D) topological phase. Here, we show that thin films of Weyl semimetals [which we call quasi-(3−1)-dimensional, or q(3−1)D] generically realize finite-size topological phases distinct from 3D and 2D topological phases of established classification schemes: response signatures of the 3D bulk topology coexist with topologically protected, quasi-(3−2)D Fermi arc states or chiral boundary modes due to a second, previously unidentified bulk-boundary correspondence. We show these finite-size topological semimetal phases are realized by Hamiltonians capturing the Fermiology of few-layer van der Waals material MoTe2 in experiment. Given the broad experimental interest in few-layer van der Waals materials and topological semimetals, our work paves the way for extensive future theoretical and experimental characterization of finite-size topological phases. Published by the American Physical Society 2025

Spin Magnetic Effect Activate Dual Site Intramolecular O─O Bridging for Nickel-Iron Hydroxide Enhanced Oxygen Evolution Catalysis.

The oxygen evolution reaction (OER) involves the recombination of diamagnetic hydroxyl (OH) or water (H2O) into the paramagnetic triplet state of oxygen (O2). The spin conservation of oxygen intermediates plays a crucial role in OER, however, research on spin dynamics during the catalytic process remains in its early stages. Herein, β-Ni(OH)2 and Fe-doped β-Ni(OH)2 (Ni5Fe1(OH)2) are utilized as model catalysts to understand the mechanism of spin magnetic effects at iron (III) sites during OER. Combined with magnetic characterization, it is founded that the introduction of Fe transforms the antiferromagnetic Ni(OH)2 into a ferromagnetic material. Testing the magnetic response of the catalyst under an external magnetic field, the OER activity of Ni5Fe1(OH)2 is significantly enhanced in comparison to Ni(OH)2. This improvement is likely due to the introduction of iron sites, which promote spin magnetic effects and enhance reaction kinetics, thereby increasing catalytic efficiency. Combining experimental and theoretical characterization, it is discovered that the iron sites accelerate the formation of heterogeneous dual-site O─O bridging, represented as ─Ni─O─O─Fe─, thereby effectively enhancing the kinetics of the OER reaction. This study provides a magnetic perspective on the structure-function relationship of magnetic iron-based catalysts and has significant implications for the design of new catalysts.

Recovering manifold representations via unsupervised meta-learning

Manifold representation learning holds great promise for theoretical understanding and characterization of deep neural networks' behaviors through the lens of geometries. However, data scarcity remains a major challenge in manifold analysis especially for data and applications with real-world complexity. To address this issue, we propose manifold representation meta-learning (MRML) based on autoencoders to recover the underlying manifold structures without uniformly or densely sampled data. Specifically, we adopt episodic training, following model agnostic meta-learning, to meta-learn autoencoders that are generalizable to unseen samples specifically corresponding to regions with low-sampling density. We demonstrate the effectiveness of MRML via empirical experiments on LineMOD, a dataset curated for 6-D object pose estimation. We also apply topological metrics based on persistent homology and neighborhood graphs for quantitative assessment of manifolds reconstructed by MRML. In comparison to state-of-the-art baselines, our proposed approach demonstrates improved manifold reconstruction better matching the data manifold by preserving prominent topological features and relative proximity of samples.

Superior Multimodal Luminescence in a Stable Single-Host Nanomaterial with Large-Scale Synthesis for High-Level Anti-Counterfeiting and Encryption.

Multimode luminescent materials exhibit tunable photon emissions under different excitation or stimuli channels, endowing them high encoding capacity and confidentiality for anti-counterfeiting and encryption. Achieving multimode luminescence into a stable single material presents a promising but remains a challenge. Here, the downshifting/upconversion emissions, color-tuning persistent luminescence (PersL), temperature-dependent multi-color emissions, and hydrochromism are integrated into Er3+ ions doped Cs2NaYbCl6 nanocrystals (NCs) by leveraging shallow defect levels and directed energy migration. The resulting NCs display strong static and dynamic colorful luminescence in response to ultraviolet, 980-nm laser, and X-ray. Additionally, the NCs exhibit distinct luminescent colors as the temperature increases from 330 to 430 K. Surprisingly, it also demonstrates the ability of the reversible emission modal and color in response to water. Theoretical calculations and experimental characterizations reveal that self-trapped exciton state (STEs), chlorine vacancy defects, and ladderlike 4f energy levels of Er3+ ions contribute to multimodal luminescence. More importantly, it has extremely remarkable environmental stability, which can be stored in the air for more than 18 months, showing promising commercial prospects. This work not only gives new insights into lanthanide-based metal halide NCs but also provides a new route for developing multimodal luminescent nanomaterials for anti-counterfeiting and encryption.

Phytochemical and Antioxidant Analysis of Bioactive Compound Extract from Nelumbo nucifera against Cancer Proteins: In Silico Spectroscopic Approach.

Nelumbo nucifera, an aquatic crop cultivated throughout Asian countries, belongs to the Nelumbonaceae family and has been widely used in traditional medicines with key pharmacological activities such as anti-viral, antipyretic, antioxidant, anti-steroid, anti-inflammatory, anti-arrhythmia, anti-obesity, and anti-aging properties. The present study aims to explore and assess the phytochemical composition, GC-MS profiling, antioxidant efficacy, and the major phytoconstituent phytol subjected to theoretical spectroscopic characterization using the DFT method. The phytochemical profiling of N. nucifera reveals the presence of alkaloids, carbohydrates, saponin, phenol, and flavonoids. The antioxidant efficacy of N. nucifera extract against DPPH and ABTS radicals increased in a concentration-dependent manner, with an IC50 value of 222.84µg and 52.67µg, respectively. The simulated structural parameters of phytol exhibited strong concordance with experimental values. The simulated wavenumbers identified characteristic peaks corresponding to hydroxyl (OH), methylene (CH2), and methyl (CH3) groups. The simulated electronic spectrum of phytol exhibits a prominent absorption peak at 174nm, predominantly attributed to the transitions H-1 → L (58%) and H → L (36%). NBO analysis reveals significant stabilization energy (7.09kJ/mol) due to the donation of electrons from the C20-H58 bonding orbital to the anti-bonding orbital of C18-C19 via a σ → σ* transition. In Mulliken charge distribution, compared to other hydrogen, hydrogen H61 in the hydroxyl (O-H) group exhibits a higher positive potential due to the influence of the oxygen atom. In addition, molecular docking was performed against breast cancer SMAD proteins to confirm its antagonist property, with binding energies of - 3.64kcal/mol (6OM2), - 5.49kcal/mol (1U7F), - 5.05kcal/mol (1U7V), and - 3.73kcal/mol (6FX4).

Aqueous Alkaline Zinc-Iodine Battery with Two-Electron Transfer.

While many cathode materials have been developed for mild electrolyte-based Zn batteries, the lack of cathode materials hinders the progress of alkaline zinc batteries. Halide iodine, with its copious valence nature and redox possibilities, is considered a promising candidate. However, energetic alkaline iodine redox chemistry is impeded by an alkali-unadapted I2 element cathode and thermodynamically unstable reaction products. Here, we formulated and evaluated an aqueous alkaline Zn-iodine battery with a two-electron transfer employing an organic iodized salt cathode and a Cl--manipulated electrolyte. The single-step redox reaction of the I-/I+ couple resulted in a high discharge plateau of 1.68 V and a capacity of 385 mA h g-1. Our battery reached an energy density of 577 W h kg-1, superior to that of reported counterparts. Theoretical and experimental characterizations determined the redox chemistry between alkaline and iodine. We believe the developed iodine chemistry in alkaline environments can enrich cathode materials for alkaline batteries.

Hydroxylated magnetic microporous organic network for efficient magnetic solid phase extraction of trace triazine herbicides.

Here we covalently constructed abundant long-chain hydroxyl groups-functionalized magnetic microporous organic networks (MMON-2OH) for detection of eight Triazine herbicides (THs) in honey and water samples. MMON-2OH owned a high surface area (287.86 m²/g), enhanced water compatibility, and increased exposure of long-chain hydroxyl groups, which significantly improved enrichment capacity for THs. Theoretical analyses and characterization data revealed interaction mechanisms, including hydrogen bonds (N-H···O and O-H···N), halogen bond (Cl···N) and π stackings (NH-π, CH-π and π-π). This approach was developed for the detection of THs, achieving a low detection limit 0.03∼0.6 ng⋅L-1 for water, and 0.006∼0.134 μg·kg-1 for honey. Trace concentrations of THs, ranging from 1.0∼21.2 ng⋅L-1 in surface water and 0.1∼0.9 μg·kg-1 in honey, were successfully detected. Sample spiked recovery experiments demonstrated recoveries between 72.1-116.2 %, validating accuracy and applicability of method. This study realizes a speedy and sensitive determination of THs, showcasing potential of MMON-2OH in pollutant removal and food safety maintenance.

Catalytic cleavage of C O bonds in benzyl phenyl ether by MoS2-confined Fe Co dual-metal-site catalyst: A theoretical characterization of dual-metal-site synergy

Catalytic cleavage of C O bonds in benzyl phenyl ether by MoS2-confined Fe Co dual-metal-site catalyst: A theoretical characterization of dual-metal-site synergy

Modeling WO3 beyond the Harmonic Approximation: Theoretical Characterization and Thermal Expansion

Modeling WO₃ beyond the Harmonic Approximation: Theoretical Characterization and Thermal Expansion

Structural, dielectric, optical and photocatalytic properties of (Na0.5Bi0.5)ZrO3 lead-free perovskite: insights from experimental and ab initio theoretical studies

Abstract In this work, we present structural, dielectric, optical and photocatalytic properties of the room temperature phase of the lead-free perovskite (Na0.5Bi0.5)ZrO3 (NBZ) system. The structural and optical properties are analyzed by combining a first-principles density functional theoretical approach and experimental characterizations. A conventional solid-state method is used for the synthesis process. X-ray powder diffraction and Rietveld refinement of the powder patterns at room temperature showed the NBZ material to be orthorhombic perovskite belonging to the space group Pnma. The calculated lattice constants of NBZ are found to be in good agreement with the experimental results. The dielectric study revealed a diffuse phase transition (DPT) in the vicinity of 290 °C. Based on the microscopic composition fluctuation model and phenomenological theory, a reasonable and effective characterizing parameter, the diffuseness degree, of the DPT is defined. The bandgap energy is estimated using UV–Vis spectroscopy and the optical absorption spectrum. The photocatalytic performance evaluation is performed by investigating the photodegradation kinetics of different pollutants by NBZ under visible light irradiation. The highest degradation efficiency is achieved for methylene blue (MB) dye (99% within 180 min), followed by rhodamine B (RhB), Congo red (CR) and methyl orange (MO) dyes. Overall, our results suggest good efficiency for NBZ as a photocatalytic agent with implications for large-scale photocatalytic applications in environmental and energy concerns. Furthermore, our study also provides several important benchmarking results on NBZ that have not been reported so far.

Cation‐Vacancy Engineering Modulated Perovskite Oxide for Boosting Electrocatalytic Conversion of Polysulfides

AbstractLithium‐sulfur batteries face challenges like polysulfide shuttle and slow conversion kinetics, hindering their practical applications in renewable energy storage and electric vehicles. Herein, a solution to solve this issue is reported by using a cation vacancy engineering strategy with rational synthesis of La‐deficient LaCoO3 (LCO‐VLa). The introduction of cation vacancies in LCO‐VLa modifies the geometric structure of coordinating atoms, exposing Co‐rich surface with more catalytically active surfaces. Meanwhile, the d‐band center of LCO‐VLa shifts toward the Fermi level, enhancing polysulfide adsorption. Furthermore, multivalent cobalt ions (Co3+/Co4+) induced by charge compensation enhance the electrical conductivity of LCO‐VLa, accelerating electron transfer processes and improving catalytic performance. Theoretical calculations and experimental characterizations demonstrate that La‐deficient LCO‐VLa effectively suppresses the polysulfide shuttle, reduces the energy barrier for polysulfide conversion, and accelerates redox reaction kinetics. LCO‐VLa‐based batteries demonstrate exceptional rate performance and cycling stability, retaining 70% capacity after nearly 500 cycles at 1.0 C, with a minimal decay rate of 0.055% per cycle. These findings highlight the significance of cation vacancy engineering for exploring precise structure‐activity relationships during polysulfides conversion, facilitating the rational design of catalysts at the atomic level for lithium‐sulfur batteries.

Crystal facet regulation enhances the photocatalytic performance for gaseous toluene degradation in BiOCl by promoting the activation of the methyl C(sp3)-H bond

In the field of heterogeneous photocatalysis, the exposure and arrangement of surface atoms exert a profound impact on the reactivity of photocatalysts, dictating the formation of various active sites and reaction pathways. Utilizing crystal facet engineering and surface modification under standard temperature and pressure conditions, we have synthesized BiOCl photocatalysts with an increased exposure of (110) facets, denoted as oxygen vacancy (Ov). The coordination of Bi3+ with thiourea and acetic acid governed the growth direction of BiOCl, inducing lattice distortion andin synergy with ethylene glycol (EG), promoting the preferential formation of Ov. This innovative strategy not only fine-tuned the bandgap of BiOCl by adjusting the conduction band (CB) position but also significantly augmented the migration velocity and separation efficiency of surface charge carriers. In the photocatalytic interaction with toluene, BiOCl demonstrated an enhanced adsorption capacity and a more potent activation of methyl C (sp3)-H bonds, concomitant with the production of substantial superoxide anion radicals (·O2–), which expedited the degradation of toluene. Theoretical computations and detailed characterizations have unveiled the corresponding mechanism and the degradation pathways of toluene at the photocatalytic interface.

Organic-inorganic hybrid cathode enabled by in-situ interface polymerization engineering boosts Zn2+ desolvation in aqueous zinc-ion batteries

Rechargeable aqueous zinc-ion batteries (RAZIBs) have attracted considerable attention for application in large-scale energy storage systems. However, the progress of RAZIBs has been hindered by the sluggish reaction kinetics and poor structural stability, which are closely associated with the desolvation process of hydrated Zn2+. To overcome these issues, an in situ interfacial polymerization strategy is proposed to uniformly germinate a polyaniline (PANI) layer on α-MnO2 and form an organic–inorganic hybrid cathode (MnO2@PANI). Theoretical calculations and experimental characterizations disclose that the polyaniline layer equipped with hydrophilic functional groups can effectively trap the active water molecules to break the strong attraction between H2O and Zn2+, thereby facilitating the desolvation process of hydrated Zn2+, and regulating the Zn2+ diffusion kinetics and electrode reaction kinetics on the cathode/electrolyte surface. Meanwhile, the irreversible phase evolution and dissolution of active species are largely suppressed due to the PANI shell protecting the α-MnO2 from the attack of active water molecules. As a consequence, the organic–inorganic hybrid cathode exhibits 401.9 mAh/g after 200 cycles at a current density of 0.5 A/g and long-term durability over 1000 cycles at a current density of 2.0 A/g without irreversible phase transformation. This work provides insight into the regulation of the desolvation process for high performance aqueous energy storage systems.

Low Dimensional vanadium pentoxide nanomaterial: Experimental and theoretical characterization on enhancing LED performance

Comprehensive understanding about the novel approach of sysnthesis of hierarchically structured pure and doped vanadium oxides using hydrothermal route. Delocalization electron transition appears the strong absorption band at 361.31 nm in the Photoluminescence (PL) signals. In dual doped samples this absorption increases the optical absorption in visible region (blue-green). Cyclic Voltammetry (CV) results obtained for pure and doped materials shows the expanded anodic and cathodic peaks of pure substance. The quantum chemical calculations analysis gives prominent molecular geometry. The confirmation analysis, Molecular Electrostatic Potential (MEP) reveals that cation doped substance has minimum energy. The biological activities of selected samples are characterized.

On the directionality of membrane coupled Helmholtz resonators under open air conditions

Controlling the absorption and diffusion of sound in the audible range constitutes an exciting field of research. Acoustic absorbers and diffusers perform extraordinarily well at high frequencies with sizes comparable to the wavelength of the working frequency. Conversely, efficient low-frequency attenuators demand large volumes leading to unpractical sizes, and there is now interest in determining whether the size of the resonator can be reduced while not compromising – or perhaps even decreasing – the working frequency. One viable approach is through the use of metamaterials to enable the control of device dynamics such that heavy sub-wavelength attenuation can be efficiently realised. To achieve this goal, the theoretical (including a mathematical model and the use of finite element analysis) and experimental characterisation of 3D-printed membrane-coupled Helmholtz resonator (HR) acoustic metamaterials (AMMs) is explored. The results reveal good agreement between theory and experiments, and show that membrane-coupled HR AMMs feature heavy sub-wavelength acoustic attenuation (λ/55) while also showcasing directional responses under open air conditions. These features are explained by the interplay between resonator size, membrane characteristics, and the presence of two acoustic ports. It is anticipated that, together with recent advances on smart AMMs, these systems will foster new progress in the development of dynamic AMMs for wideband attenuation.

An Ultrafast and Ultralow‐Temperature 3D‐Printed All‐Organic Proton Pseudocapacitor

AbstractA critical challenge for pseudocapacitors applications is the rapid capacitance fading under extreme environments, which originates from sluggish diffusion kinetics of inorganic materials and tortuous ionic channels in conventional bulk electrodes. Herein, a novel 3D‐printed all‐organic proton pseudocapacitor (composed of 2,6‐diaminoanthraquinone (DQ)‐based anode and polyaniline‐based cathode) with chemical and structural stability is developed, which exhibits an extraordinary rate performance and cycle stability under ultralow temperature. The DQ molecules are anchored on reduced graphene oxide, which enhances the electronic conductivity and structural stability. Theoretical calculation and spectroscopic characterization reveal that the two‐electron transfer process involves quinone/hydroquinone transition. Exploiting the synergy of fast reaction kinetics of organic and the efficient ion diffusion paths of the 3D architecture, the 3D‐printed anode achieves an impressive areal capacitance of 10.14 F cm−2 at high mass loading (28.73 mg cm−2). The 3D‐printed all‐organic proton pseudocapacitor shows stable cycling performance at −80 °C and releases a high energy density of 0.76 mWh cm−2 at −60 °C. This work is instructive for the development of competitive ultra‐low temperature energy storage devices via integrating organic materials and 3D architectural electrode designs.

Secondary Sphere Lewis Acid Activated Heme Superoxo Adducts Mimic Crucial Non-Covalent Interactions in IDO/TDO Heme Dioxygenases.

Heme enzymes play a central role in a medley of reactivities within a wide variety of crucial biological systems. Their active sites are highly decorated with pivotal evolutionarily optimized non-covalent interactions that precisely choreograph their biological functionalities with specific regio-, stereo-, and chemo-selectivities. Gaining a clear comprehension of how such weak interactions within the active sites control reactivity offers powerful information to be implemented into the design of future therapeutic agents that target these heme enzymes. To shed light on such critical details pertaining to tryptophan dioxygenating heme enzymes, this study investigates the indole dioxygenation reactivities of Lewis acid-activated heme superoxo model systems, wherein an unprecedented kinetic behavior is revealed. In that, the activated heme superoxo adduct is observed to undergo indole dioxygenation with the intermediacy of a non-covalently organized precursor complex, which forms prior to the rate-limiting step of the overall reaction landscape. Spectroscopic and theoretical characterization of this precursor complex draws close parallels to the ternary complex of heme dioxygenases, which has been postulated to be of crucial importance for successful 2,3-dioxygenative cleavage of indole moieties.

Legal nature of social protection of civil servants in modern conditions of information communications and European integration of Ukraine

The article is devoted to a detailed analysis of the legal nature of social protection of civil servants in the conditions of modern information communications and European integration processes of Ukraine. In the course of the study, theoretical approaches to determining the essence of social protection were considered, as well as the positions of various scientists who studied this issue were given. The advantages and disadvantages of the main concepts proposed in the scientific literature are analyzed, with an emphasis on their compliance with modern challenges and conditions of development of public administration in Ukraine. The article pays attention to the justification of one’s own position regarding the improvement of the system of social protection of civil servants, taking into account modern European integration trends and the influence of information technologies. The essence of the legal nature of social protection is revealed, the concept is characterized, and a general theoretical characterization of this legal phenomenon is carried out. It was determined that the social protection of civil servants is an important component of ensuring the stability and efficiency of the civil service, which provides social guarantees necessary for the performance of official duties at a high professional level. Actual problems of ensuring social guarantees of civil servants are studied in the context of strengthening European integration and introduction of information technologies in public administration. The key legal mechanisms aimed at ensuring fair access to social services are identified, and the need to reform the existing social protection system to eliminate inequalities between civil servants of different job categories is substantiated. On the basis of the analysis of the provisions of various scientists, the advantages and disadvantages of the existing mechanisms of social protection are highlighted, as well as ways of their optimization are considered. The article also emphasizes the importance of a comprehensive approach to the development and implementation of legal norms that ensure social protection of civil servants, in order to increase the efficiency of the civil service and maintain a high level of professionalism of personnel.

Navigating highly reversible Zn metal anodes via a multifunctional corrosion inhibitor-inspired electrolyte additive

Uncontrolled dendrites growth and irreversible side reactions on the Zn anode have greatly shorten the lifespan of aqueous zinc-ion batteries (ZIBs), thereby hindering their application as promising energy storage devices. Herein, inspired by the use of corrosion and scale inhibitors in metal industry, sodium gluconate (SG) is proposed as a multifunctional electrolyte additive to improve the reversible plating/stripping behavior on Zn metal anodes by simultaneously modulating Zn anode-electrolyte interface and the Zn deposition behaviors. Combining theoretical calculations and experimental characterizations, it shows that SG can protect the Zn anode against the corrosion side reactions and suppress the random growth of dendritic Zn by absorbing on the Zn anode surface to form an artificial interface layer. Concomitantly, the gluconate anion reshapes the solvation shell of Zn2+, influencing the desolvation process of Zn2+ and disrupting the formation of active water. Furthermore, Na+ originating from SG suppresses the dendritic Zn development in the light of electrostatic shielding mechanism. Benefiting from these synergetic effects of SG additive, Zn metal anodes achieve exceptional reversibility with prolonged running lifetime and increased coulombic efficiency and the Zn||V2O5 full cell demonstrates outstanding cycle stability. This strategy is scalable and low-cost, developing a promising approach to advance high-performance ZIBs.

Evaluation of 14-(p-tolyl)-14H-dibenzo[a,j]xanthene as a highly efficient organic corrosion inhibitor for mild steel in 1 M HCl: Electrochemical, theoretical, and surface characterization

Corrosion of mild steel, particularly in acidic environments such as hydrochloric acid (HCl), remains a critical issue due to its impact on material durability, economic costs, and safety concerns. This study introduces 14-(p-tolyl)-14H-dibenzo[a,j]xanthene (ZM5), a novel and highly effective organic corrosion inhibitor, to mitigate this challenge. Employing advanced electrochemical techniques: electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP), we evaluated ZM5’s performance in a 1 M HCl solution, revealing an impressive inhibition efficiency of 94.7 %. Surface characterization using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) further confirmed the formation of a robust protective film on the steel surface, shedding light on ZM5’s adsorption mechanisms. Complementing the experimental findings, Density Functional Theory (DFT) simulations provided theoretical insights into the anti-corrosion mechanism of ZM5, aligning well with observed results. These findings underscore ZM5's potential as a highly promising corrosion inhibitor for industrial applications, effectively enhancing the corrosion resistance of mild steel in aggressive environments.