Crystals

15 pages, 3262 KB

Open AccessArticle

Electrolyte-Dependent Electrochemical Exfoliation of MoS₂ Nanosheets and Its Impact on Nonlinear Optical Limiting

by Xuefeng Chu, Siming Qiao, Haiyang Zhao, Bingxue Li, Junjie Pan, Longyu Guo, Dingxuan Zhang, Chao Wang, Sa Lv, Faxin Peng, Haoran Niu, Xuan Fang and Xiaotian Yang

Crystals 2026, 16(5), 301; https://doi.org/10.3390/cryst16050301 (registering DOI) - 2 May 2026

Abstract

Electrochemical exfoliation is an efficient approach for producing MoS₂ nanosheets, yet the correlation between exfoliation conditions, structural evolution, and nonlinear optical (NLO) properties remains insufficiently understood. In this work, MoS₂ nanosheets were prepared using two representative electrolyte systems, acetonitrile/TPABr and aqueous [...] Read more.

Electrochemical exfoliation is an efficient approach for producing MoS₂ nanosheets, yet the correlation between exfoliation conditions, structural evolution, and nonlinear optical (NLO) properties remains insufficiently understood. In this work, MoS₂ nanosheets were prepared using two representative electrolyte systems, acetonitrile/TPABr and aqueous Na₂SO₄, under controlled voltages. The results reveal distinct exfoliation mechanisms, where ion intercalation dominates in the nonaqueous system, while bubble-assisted processes prevail in the aqueous system. Structural and chemical analyses (Raman, XRD, EDS, and XPS) demonstrate that the nonaqueous system yields MoS₂ with higher crystallinity and lower oxidation degree, whereas the aqueous system shows increased oxidation with the coexistence of Mo⁵⁺ and Mo⁶⁺ species. Correspondingly, enhanced nonlinear absorption and optical limiting performance are observed. A clear mechanism–structure–property relationship is established, highlighting the critical role of electrolyte environment and applied voltage in tailoring NLO responses. This work provides insights into the controlled preparation of MoS₂ nanosheets for photonic and optoelectronic applications. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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25 pages, 1939 KB

Open AccessArticle

Crystallographic Study, Biological Evaluation and Docking/MD/POM Analyses of Isoxazole-Linked Sulfonate Ester Conjugates

by Aziz Arzine, Khaoula Faiz, Amal Bouribab, Najoua Soulo, Pascal Retailleau, Mohammed Chalkha, Asmae Nakkabi, Samir Chtita, Bouchra Louasté, Taibi Ben Hadda, Karim Chkirate, Joel T. Mague, Adam Duong, Reem M. Aljowaiee, Mourad A. M. Aboul-Soud and Mohamed El Yazidi

Crystals 2026, 16(5), 300; https://doi.org/10.3390/cryst16050300 - 1 May 2026

Abstract

In the present study, a series of isoxazole derivatives were severally evaluated for their antifungal activity against the yeast Candida albicans and molds such as Aspergillus niger, Aspergillus flavus, and Fusarium oxysporum. The results demonstrate that the isoxazole derivatives exhibit [...] Read more.

In the present study, a series of isoxazole derivatives were severally evaluated for their antifungal activity against the yeast Candida albicans and molds such as Aspergillus niger, Aspergillus flavus, and Fusarium oxysporum. The results demonstrate that the isoxazole derivatives exhibit considerable antifungal potential, particularly isoxazole-sulfonate ester 4b (Ar= 4-(Cl)C₆H₄, Ar′= 4-(CH₃)C₆H₄), which was found to be active with significant inhibition zones; the diameters of the C. albicans and F. oxysporum samples were measured at 17.00 ± 0.00 mm and 14.00 ± 0.00 mm, respectively. Furthermore, compounds 4a (Ar= 4-(CH₃)C₆H₄, Ar′= 4-(CH₃)C₆H₄), 4c (Ar: 4-(Cl)C₆H₄, Ar′: 4-(NO₂)C₆H₄) and 4d (Ar: 4-(Cl)C₆H₄, Ar′: 3-(Cl)-2-(OCH₃)C₆H₃) demonstrated MIC and MFC values of 20 µg/mL against C. albicans. In addition, the anti-hemolytic activity of these derivatives was evaluated. Compounds 4a, 4e (Ar: 4-(Cl)C₆H₄, Ar′: 3,4-(OCH₃)₂C₆H₃) and aroylisoxazole 3a (Ar: 4-(CH₃)C₆H₄) demonstrated a high degree of anti-hemolytic activity (>99%) at all concentrations evaluated (10, 15, and 20 mg/mL). Molecular docking and molecular dynamics studies over 200 ns revealed protein–ligand complexes to have high affinity and stability, which agrees with the experimental results. The compounds 4d, 4e, and 3a have shown significant interaction with the target proteins of C. albicans, A. flavus, and F. oxysporum, respectively. The results have revealed that the major interaction sites are hydrogen bonding, hydrophobic interactions, and the presence of a water molecule, especially with key residues like TYR_84, ASP_120, SER_90, and THR_89. The crystal structure of compound 4a was also obtained. Full article

(This article belongs to the Special Issue Heterocyclic Compounds in Drug Discovery: Synthesis, X-Ray Crystal Structures, Applications and Computational Approaches)

12 pages, 4381 KB

Open AccessArticle

High-Field Measurements of CoP and Elemental Combinatorics in the MnP-Type Family

by Daniel J. Campbell, John Collini, Kefeng Wang, Limin Wang, Brandon Wilfong, David Graf, Efrain E. Rodriguez and Johnpierre Paglione

Crystals 2026, 16(5), 299; https://doi.org/10.3390/cryst16050299 - 1 May 2026

Abstract

The MnP family of binary compounds presents an intriguingly simple platform to mix-and-match elemental components. Replacement on the transition metal or pnictogen site can alter magnetism, electronic correlations, and electrical properties. Here we report low-temperature properties of CoP, including measurements at magnetic fields [...] Read more.

The MnP family of binary compounds presents an intriguingly simple platform to mix-and-match elemental components. Replacement on the transition metal or pnictogen site can alter magnetism, electronic correlations, and electrical properties. Here we report low-temperature properties of CoP, including measurements at magnetic fields exceeding 30 T, revealing de Haas–van Alphen oscillations and a nearly two orders of magnitude increase in resistance. When viewed together with prior work, it is possible to put together a global picture of the role of different atoms in variations in magnetic ordering, lattice coherence, and topological band structure features in this material family. Full article

(This article belongs to the Section Crystalline Metals and Alloys)

22 pages, 3065 KB

Open AccessArticle

Selective Co-Crystallization and Co-Amorphous Formation of Flavanones from Licorice Leaves

by Alessandra Crispini, Francesca Aiello and Francesca Scarpelli

Crystals 2026, 16(5), 298; https://doi.org/10.3390/cryst16050298 - 1 May 2026

Abstract

Flavanones retrieved in the leaves of Glycyrrhiza glabra (licorice), specifically glabranin (GLA), pinocembrin (PIN) and licoflavanone (LIC), represent a valuable source of bioactive natural products, although their isolation and handling are often complicated by their structural similarity and unfavorable physical properties. In this [...] Read more.

Flavanones retrieved in the leaves of Glycyrrhiza glabra (licorice), specifically glabranin (GLA), pinocembrin (PIN) and licoflavanone (LIC), represent a valuable source of bioactive natural products, although their isolation and handling are often complicated by their structural similarity and unfavorable physical properties. In this work, crystal engineering strategies were explored both to facilitate the selective separation of licorice flavanones and to improve their solid-state characteristics. Co-crystallization was investigated as a tool for the selective recognition of PIN from a GLA-rich chromatographic fraction. Guided by structural considerations and predictive analyses performed using the Co-Crystal Design and Hydrogen Bond Propensity (HBP) tools in CCDC Mercury (within CCDC-Materials), co-crystallization experiments were performed with pyridinic co-formers. 4,4′-Bipyridine (BPY) selectively formed a new co-crystal with PIN, enabling the capture of traces of this flavanone directly from the GLA-rich fraction. In contrast, nicotinic acid (NIC) did not form a co-crystal with PIN, consistently with the predicted preference for NIC self-association. In addition, a co-amorphous system between LIC and BPY was obtained by quench cooling, yielding a fully amorphous solid with improved handling properties compared to the waxy precursor. These results highlight the potential of crystal engineering approaches for the selective separation and solid-state modification of natural flavanones. Full article

(This article belongs to the Section Crystal Engineering)

14 pages, 1372 KB

Open AccessArticle

Mineralogical Characteristics and Fluorescent Properties of Yellow and Pink Calcite

by Qiuli Yan, Wenkai Liang and Qingfeng Guo

Crystals 2026, 16(5), 297; https://doi.org/10.3390/cryst16050297 - 30 Apr 2026

Abstract

Yellow and pink calcite samples from the Huanggangliang and Xilingol mining areas in Inner Mongolia were investigated to elucidate the relationships among chemical composition, unit-cell parameters, coloration, and luminescence. Electron probe micro-analysis, laser ablation inductively coupled plasma mass spectrometry, X-ray diffraction, infrared spectroscopy, [...] Read more.

Yellow and pink calcite samples from the Huanggangliang and Xilingol mining areas in Inner Mongolia were investigated to elucidate the relationships among chemical composition, unit-cell parameters, coloration, and luminescence. Electron probe micro-analysis, laser ablation inductively coupled plasma mass spectrometry, X-ray diffraction, infrared spectroscopy, Raman spectroscopy, UV-Vis absorption spectroscopy, and photoluminescence measurements show that samples of yellow and pink calcite differ significantly in impurity incorporation and optical behavior. Yellow calcite is relatively enriched in Mg and rare earth elements, especially Y and Ce, whereas pink calcite contains markedly higher Mn and Fe contents. The pink calcite has smaller lattice parameters and unit-cell volume, consistent with greater substitution of Ca²⁺ by smaller-radius cations. Spectra reveal that the pink coloration is mainly related to Mn-associated absorption bands at 402 and 527 nm, whereas the yellow color is attributed to weak impurity- and defect-related absorption. Under ultraviolet excitation, yellow calcite exhibits a broad blue–white emission centered at ~470 nm, whereas pink calcite shows an intense orange–red emission near 625 nm characteristic of Mn²⁺. Variable-temperature photoluminescence further demonstrates that the pink calcite has higher thermal stability, with a thermal-quenching activation energy of 0.218 eV, compared with 0.074 eV for the yellow calcite. These results demonstrate that trace element incorporation plays a key role in regulating the coloration and luminescence of calcite and provide useful insight into the optical behavior of carbonate minerals. Full article

(This article belongs to the Special Issue In Situ Study of Mineralogy, Gemology, and Geochemistry and Advances in Gem Resource Exploration)

19 pages, 7474 KB

Open AccessArticle

Effect of Picosecond Laser Diverse Scanning Strategies in Fabrication of Broadband AntiReflection Structures on Copper

by Jie Zhao, Zehao Cao, Yilongrui Chen and Zongtai He

Crystals 2026, 16(5), 296; https://doi.org/10.3390/cryst16050296 - 30 Apr 2026

Abstract

Broadband antireflective surface technology constitutes a crucial technique in optoelectronic devices, playing a key role in reducing optical losses. Ultrafast laser processing provides a flexible route for fabricating micro-nano structures on metallic surfaces because it enables efficient fabrication, high spatial resolution, and minimal [...] Read more.

Broadband antireflective surface technology constitutes a crucial technique in optoelectronic devices, playing a key role in reducing optical losses. Ultrafast laser processing provides a flexible route for fabricating micro-nano structures on metallic surfaces because it enables efficient fabrication, high spatial resolution, and minimal chemical consumption. This study uses a variable-angle scanning strategy to texture the copper surface, produce a series of antireflection arrayed micro-nano structures, and study the spectral reflectance characteristics of the copper surface. The results exhibit that 90° orthogonal scanning favors the formation of an arrayed microcone structure, which shows lower reflectance than the non-orthogonal scanning strategies in the 200–1300 nm band, with a minimum reflectance of 0.94%. The 60° and 45° cross-scanning based on the non-orthogonal strategy favors the formation of microcavity structures, and shows low reflectance in the 1300–2500 nm band, with the maximum reflectance remaining below 5%. Laser-induced periodic surface structures (LIPSS) are observed on the structures fabricated by all strategies. This work demonstrates that the scanning angle itself can be used to switch the dominant surface morphology and thereby tailor the spectral antireflection response, and lies in establishing a clear processing–structure–spectral response relationship for copper surfaces, which provides a designable route for wavelength-selective optical absorption in photothermal conversion, infrared detection, and sensing applications. Full article

(This article belongs to the Section Crystalline Metals and Alloys)

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24 pages, 8446 KB

Open AccessArticle

The Influence of Discontinuous Dynamic Recrystallization on the Microstructure and Distribution of Plastic Deformations in Pure Aluminum and Copper at High Strain Rates

by Evgenii Fomin and Ilya Bryukhanov

Crystals 2026, 16(5), 295; https://doi.org/10.3390/cryst16050295 - 30 Apr 2026

Abstract

Dynamic recrystallization processes are known to significantly affect both the mechanical properties and the microstructure of materials. In this paper, we investigate the influence of discontinuous dynamic recrystallization (dDRX) during deformation at high strain rates (from 10⁴ to 10⁵ s⁻¹ [...] Read more.

Dynamic recrystallization processes are known to significantly affect both the mechanical properties and the microstructure of materials. In this paper, we investigate the influence of discontinuous dynamic recrystallization (dDRX) during deformation at high strain rates (from 10⁴ to 10⁵ s⁻¹) and elevated temperatures in pure aluminum and copper (in the range of 700–800 K for aluminum and 800–1100 K for copper). For this purpose, we propose a theoretical model in which the material is described within the framework of continuum mechanics, plastic deformations are modeled using a dislocation plasticity approach, the equation of state is represented by a neural network, and the microstructure evolution is simulated using the cellular automata method. The model is applied to uniaxial compression and tension of copper and aluminum polycrystals with an initial average grain size of 14 μm. It is shown that grain refinement occurs in all systems. The average grain size decreases from 14 μm to 4–5 μm. The distribution of plastic and total strains in the polycrystals is presented. In all considered systems, deformation localization is observed, and the localization pattern changes due to the nucleation of new grains and grain boundary surfaces during dynamic recrystallization. Full article

(This article belongs to the Topic Microstructure and Properties in Metals and Alloys, 4th Edition)

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13 pages, 2318 KB

Open AccessArticle

Low-Temperature Sintering and Piezoelectric Properties of Pb(Fe₂/₃W₁/₃)O₃-Doped 0.7Pb(Zr_0.46Ti_0.54)O₃–0.1Pb(Zn_1/3Nb_2/3)O₃–0.2Pb(Ni_1/3Nb_2/3)O₃ Ceramics for Free-Standing Silver-Electrode Co-Fired Multilayer Piezoelectric Devices

by Naihe Yi, Hongwei Zhang, Jingnan Hong, Zhuo Zhang, Hongjie She, Sen Yang and Weibing Ma

Crystals 2026, 16(5), 294; https://doi.org/10.3390/cryst16050294 - 29 Apr 2026

Abstract

In this study, the sintering behavior and electrical properties of 0.7Pb(Zr_0.46Ti_0.54)O₃ (PZT)–0.1Pb(Zn₁/₃Nb₂/₃)O₃ (PZN)–0.2Pb(Ni₁/₃Nb₂/₃)O₃ (PNN) piezoelectric ceramics with different Pb(Fe₂ [...] Read more.

In this study, the sintering behavior and electrical properties of 0.7Pb(Zr_0.46Ti_0.54)O₃ (PZT)–0.1Pb(Zn₁/₃Nb₂/₃)O₃ (PZN)–0.2Pb(Ni₁/₃Nb₂/₃)O₃ (PNN) piezoelectric ceramics with different Pb(Fe₂/₃W₁/₃)O₃ (PFW) doping contents were investigated to obtain a formulation that can be co-fired with silver (Ag) electrodes below 900 °C for multilayer ceramics. PFW was introduced as a sintering aid, which effectively reduced the sintering temperature of the ceramics from 1200 °C to 850 °C. The sample with x = 0.12 exhibited the largest average grain size of 1.72 μm, achieving excellent comprehensive properties with piezoelectric constant (d₃₃) = 477 pC/N, planar electromechanical coupling factor (k_p) = 0.68, dielectric loss tangent (tanδ) = 0.0154, and relative density of 98.2%. Furthermore, the feasibility of fabricating piezoelectric actuators based on this optimized composition was verified. Multilayer piezoelectric devices were prepared via screen printing combined with a carbon-based sacrificial layer method. No obvious interdiffusion was observed at the interface between the Ag internal electrodes and the ceramic matrix. The 9-layer device attained a high d₃₃ = 1470 pC/N and produced a large displacement of 5.5 μm (corresponding to a strain = 1.83%) with a voltage of 500 V. The thickness of the multilayer piezoelectric film was approximately 0.3 mm. Through this, the feasibility of manufacturing a multilayered actuator with an Ag electrode was confirmed through the composition of 0.58PZT–0.1PZN–0.2PNN–0.12PFW. Full article

(This article belongs to the Section Polycrystalline Ceramics)

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21 pages, 14901 KB

Open AccessArticle

Crystal-Orientation-Dependent Material Removal and Subsurface Damage of AlN During Laser-Assisted Single-Grit Nanogrinding: An Atomistic Study

by Chenhao Wen, Fengwei Yuan, Haowei Fu, Yanqiang Lu, Rong Yi and Jian Guo

Crystals 2026, 16(5), 293; https://doi.org/10.3390/cryst16050293 - 29 Apr 2026

Abstract

Laser assistance offers a promising pathway for high-efficiency and low-damage ultraprecision grinding for difficult-to-machine hard-brittle semiconductors. This study employs atomistic simulation to investigate the surface removal and subsurface damage mechanisms of C-, M-, and A-plane AlN workpieces during single-grit laser-assisted nanogrinding (LAG). The [...] Read more.

Laser assistance offers a promising pathway for high-efficiency and low-damage ultraprecision grinding for difficult-to-machine hard-brittle semiconductors. This study employs atomistic simulation to investigate the surface removal and subsurface damage mechanisms of C-, M-, and A-plane AlN workpieces during single-grit laser-assisted nanogrinding (LAG). The results indicate that LAG reduces material pileup, thereby decreasing the grit–workpiece contact area and grinding resistance. By leveraging laser-induced thermal effects to enhance atomic plastic flow, LAG evidently achieves a higher material removal rate than conventional grinding (CG). Grinding the C-plane along a <11–20> orientation yields the lowest surface roughness, although this improvement is not useful for the M- and A-planes. Tangential force increases linearly with grinding depth in both methods, but LAG exhibits a lower rate of increase. LAG consistently produces lower grinding forces and friction coefficients and results in lower dislocation densities in C- and A-plane AlN workpieces at nearly all grinding depths. The C-plane exhibits the thinnest damage layer, followed by the M-plane, with the A-plane the thickest. Increasing the laser power density lowers the grinding force and enhances the removal efficiency. Optimal power density minimizes subsurface damage and improves surface quality; however, excessive power density exacerbates damage. This work provides valuable insights for developing high-efficiency, low-damage LAG techniques for hard-brittle semiconductors. Full article

(This article belongs to the Special Issue Nanocrystalline Materials Processing and Characterization)

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15 pages, 4129 KB

Open AccessArticle

The Oxidation Resistance of the B₄C-SiO₂-Albite Coating Influenced by the In Situ Formation and Self-Healing Ability of Borosilicate Glass at 1173 K

by Quanhao Luo, Jiaming Yang, Xueliang Zhang, Xuanchen Wei, Huan He, Aoping He, Tao Liu and Tianquan Liang

Crystals 2026, 16(5), 292; https://doi.org/10.3390/cryst16050292 - 29 Apr 2026

Abstract

The electrolytic aluminum industry is facing severe challenges, such as excessive carbon consumption, resulting in more cost and environmental pollution due to the oxidation of carbon anodes. The isothermal oxidation resistance of B₄C-SiO₂-Albite (BSA) composite coating influenced by the [...] Read more.

The electrolytic aluminum industry is facing severe challenges, such as excessive carbon consumption, resulting in more cost and environmental pollution due to the oxidation of carbon anodes. The isothermal oxidation resistance of B₄C-SiO₂-Albite (BSA) composite coating influenced by the in situ formation behavior and self-healing ability of the borosilicate glass at 1173 K was investigated through XRD, TG-DSC, Raman, FTIR spectroscopy, and SEM/EDS in this paper. The results show that the composite coating with 20 wt% B₄C has a relatively low mass gain rate of −0.082% after 24 h at 1173 K. It depends on the in situ formation of the amorphous borosilicate phase layer that can effectively protect the carbon anode from oxidation, which depends on the content of B₄C. The amorphous borosilicate glass forms from the reaction between the SiO₂ and the B₂O_3, from the oxidation of B₄C during exposure. More B₄C promotes the formation and volatilization of B₂O₃, which improves the viscosity and stability of the borosilicate glass by changing the glass network coupled with Na⁺ and Al³⁺ from Albite. It is a feasible strategy for designing durable coatings with appropriate B₄C addition for high-temperature applications. Full article

(This article belongs to the Special Issue Advances in Thin-Film Materials and Their Applications)

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25 pages, 19109 KB

Open AccessArticle

Structural Features, Defect-Related Photoluminescence, and Optical Constants of Mg-Doped ZnO Thin Films

by Lutfi Arda, Ersin Ozugurlu and Ilke Tascioglu

Crystals 2026, 16(5), 291; https://doi.org/10.3390/cryst16050291 - 28 Apr 2026

Abstract

Mg-doped ZnO (Zn_1−xMg_xO, x = 0.00–0.05) thin films were successfully grown on glass substrates with a c-axis orientation at 600 °C using the sol–gel dip-coating technique. The structural features, defect-related photoluminescence, and optical constants of the films were systematically [...] Read more.

Mg-doped ZnO (Zn_1−xMg_xO, x = 0.00–0.05) thin films were successfully grown on glass substrates with a c-axis orientation at 600 °C using the sol–gel dip-coating technique. The structural features, defect-related photoluminescence, and optical constants of the films were systematically investigated as a function of Mg concentration. X-ray diffraction (XRD) patterns confirmed a single-phase hexagonal wurtzite structure with a preferential (₀₀₂) orientation for all compositions, indicating the successful substitution of Mg²⁺ ions into the ZnO lattice. The crystallite size (D₀₀₂) was found to vary between 28.49 and 41.18 nm, while microstrain and stress exhibited non-monotonic behavior depending on Mg content. This behavior reveals a transition from compressive to tensile stress due to lattice distortion and defect formation. Photoluminescence (PL) spectra showed a dominant near-band-edge (NBE) ultraviolet emission, along with broad visible emissions extending from violet to red. Optical constants were accurately extracted using a double-facet-coated substrate (DFCS) model, combined with nonlinear curve fitting using the Nelder–Mead optimization algorithm. The films showed a strong absorption edge at about 370 nm and exceptional optical transparency (≈60–80%) in the visible spectrum. The systematic blue shift in the extinction coefficient with increasing Mg content confirms bandgap engineering in Zn_1−xMg_xO thin films. The refractive index dispersion was successfully modeled using the Cauchy relation, demonstrating composition-dependent tunable optical properties. Depending on the Mg content, the optical bandgap values ranged from approximately 3.265 to 3.315 eV. The band-edge states and optical constants are strongly affected by the combined effects of defect development, Mg-induced lattice distortion, and changes in optical dispersion. These results indicate that sol–gel-derived Mg-doped ZnO thin films with composition-dependent stress states, defect states, and tunable optical properties are promising candidates for UV photodetectors, optical coatings, and transparent optoelectronic devices. Full article

(This article belongs to the Special Issue Metal Oxide-Based Nanomaterials: Advances in Synthesis, Characterization, and Applications)

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12 pages, 2843 KB

Open AccessArticle

Coordination Flexibility of Zn(II) in Trimesate-Based Metal–Organic Frameworks: Formation of Distinct Secondary Building Units

by Giovanni Bella, Francesco Nicolò, Giuseppe Bruno, Amine Assel and Antonio Santoro

Crystals 2026, 16(5), 290; https://doi.org/10.3390/cryst16050290 - 28 Apr 2026

Abstract

Two zinc(II)-trimesate metal–organic frameworks were synthesized under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction. Although both compounds originate from the same Zn(II)-benzene-1,3,5-tricarboxylate (BTC) chemical system, they crystallize in different space groups and exhibit distinct coordination environments and secondary building units (SBUs). [...] Read more.

Two zinc(II)-trimesate metal–organic frameworks were synthesized under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction. Although both compounds originate from the same Zn(II)-benzene-1,3,5-tricarboxylate (BTC) chemical system, they crystallize in different space groups and exhibit distinct coordination environments and secondary building units (SBUs). One framework adopts a cubic structure and is built from a binuclear Zn paddlewheel type SBU, characterized by a short Zn–Zn internuclear distance and four μ₂-bridging carboxylate groups. In contrast, the second framework crystallizes in a tetragonal lattice and features mixed Zn(II) coordination environments, with the coexistence of tetrahedral and octahedral metal centers assembled into a fundamentally different SBU. The comparison between these two structures highlights the coordination flexibility of Zn(II) and the sensitivity of Zn–BTC frameworks to crystallization conditions, such as solvent composition. These results underline the importance of detailed crystallographic analysis in revealing SBU diversity and provide insight into how variations in local coordination chemistry can lead to distinct framework architectures from identical chemical building blocks. Full article

(This article belongs to the Special Issue Metal Coordination Complexes for Optical and Chiro-Optical Applications)

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46 pages, 9054 KB

Open AccessReview

Binary and Unfilled Skutterudites from 1957 to 2026

by Gerda Rogl and Peter Rogl

Crystals 2026, 16(5), 289; https://doi.org/10.3390/cryst16050289 - 27 Apr 2026

Abstract

Besides filled skutterudites with a high figure of merit, unfilled skutterudites also play an important role as thermoelectric materials; furthermore, they are easier to produce and do not need expensive rare earths as fillers. In the present review, thermoelectric properties (at 300 K [...] Read more.

Besides filled skutterudites with a high figure of merit, unfilled skutterudites also play an important role as thermoelectric materials; furthermore, they are easier to produce and do not need expensive rare earths as fillers. In the present review, thermoelectric properties (at 300 K and at the highest measured temperature) of more than 600 compositions from more than 230 publications between 1957 and 2025 were collected and evaluated. In various figures, the dependence of the peak ZT on the electrical resistivity, Seebeck coefficient, the power factor and the thermal conductivity is displayed for (i) binary CoSb₃, for (ii) CoSb₃ substituted at the Co-site, for (iii) substitution at the Sb-site or at both sites as well as for (iv) unfilled skutterudites without Co or Sb or Co and Sb. In most cases, the peak ZT equals the ZT at the highest measured temperature. Thermoelectric data are listed (i) to comply with the periodic chart and publishing year as well as (ii) in the form of a graphical overview of all discussed skutterudites. In this respect, this review will support the search for the ideal TE material for practical use. Full article

(This article belongs to the Section Materials for Energy Applications)

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33 pages, 15454 KB

Open AccessArticle

Physics-Guided Multitask Learning for Joint Prediction of Band Gap and Static Dielectric Response in Oxide ABO₃ Perovskites

by Yu Sun, Yihang Qin, Wenhao Chen, Wenhui Zhao and Haoran Sun

Crystals 2026, 16(5), 288; https://doi.org/10.3390/cryst16050288 - 27 Apr 2026

Abstract

Oxide perovskites with simultaneously large band gaps and high-static dielectric constants are of considerable interest for advanced microelectronics, dielectric devices, and energy storage applications, yet their discovery remains challenging because electronic insulation, lattice polarizability, and thermodynamic accessibility are strongly coupled and often mutually [...] Read more.

Oxide perovskites with simultaneously large band gaps and high-static dielectric constants are of considerable interest for advanced microelectronics, dielectric devices, and energy storage applications, yet their discovery remains challenging because electronic insulation, lattice polarizability, and thermodynamic accessibility are strongly coupled and often mutually competitive. Here, we develop a physics-guided multitask learning framework for the joint prediction of the band gap and static dielectric response in chemically constrained single-perovskite oxide ABO₃ compounds. To ensure data fidelity and physical comparability, the learning space is strictly restricted to simple oxide ABO₃ perovskites from the Materials Project, while mixed-fidelity band gaps, heterogeneous dielectric definitions, and chemically inconsistent samples are excluded. The model integrates role-aware A-/B-site descriptors, perovskite-specific geometric and structural features, multitask prediction of Eg, εtotal, εelectronic, and εionic, explicit physical consistency constraints, auxiliary candidate classification, ranking learning, and reliability-aware screening with uncertainty and out-of-distribution control. Under B-site-grouped cross-validation, the framework achieves 97.4% accuracy, Recall of 96.5%, and an F1 score of 96.1%, while maintaining robust transferability on the independent JARVIS validation set. The results show that high-gap/high-k candidates occupy a chemically non-random subspace governed by B-site-centered electronic–lattice coupling, and that physically consistent multitask learning substantially improves both predictive coherence and candidate enrichment. More broadly, this study establishes a data-consistent, physics-constrained, and transferable paradigm for the intelligent discovery of functional oxide dielectrics. Full article

(This article belongs to the Special Issue Perovskites: Crystal Structure, Properties and Applications)

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18 pages, 1940 KB

Open AccessArticle

Active Chitosan Films Incorporating a β-Cyclodextrin–Curcumin Inclusion Complex: Enhanced Film Performance and Refrigerated Preservation of Fish Fillets

by Anxing Wang, Hao Li, Qing Zhang, Yu Zhang, Yuhang Wu, Deshui Yu, Xing Fang and Guojun Yuan

Crystals 2026, 16(5), 287; https://doi.org/10.3390/cryst16050287 - 27 Apr 2026

Abstract

Achieving stable dispersion and sustained antibacterial activity of natural bioactive compounds in bio-based packaging remains challenging. In this study, chitosan (CS) films incorporating a β-cyclodextrin–curcumin inclusion complex (Cur/β-CD) were developed to improve film properties and the refrigerated preservation of sea bass. The CS/Cur/β-CD [...] Read more.

Achieving stable dispersion and sustained antibacterial activity of natural bioactive compounds in bio-based packaging remains challenging. In this study, chitosan (CS) films incorporating a β-cyclodextrin–curcumin inclusion complex (Cur/β-CD) were developed to improve film properties and the refrigerated preservation of sea bass. The CS/Cur/β-CD films were prepared by one-step solution casting without intermediate isolation or purification. The inclusion conditions were optimized, and the resulting films were evaluated in terms of tensile strength (TS), elongation at break (EAB), and water vapor permeability (WVP). Among the tested formulations, the film prepared at a Cur:β-CD ratio of 1:1, 40 °C, and 1 h (1:1 40 °C 1 h) showed the best overall performance in TS, EAB, and WVP. It was therefore selected for subsequent structural characterization, antibacterial evaluation, and preservation testing. The 1:1 40 °C 1 h film exhibited a 156% increase in tensile strength and a 28.5% decrease in water vapor permeability compared with the neat CS film. The composite film exhibited measurable diffusion-based antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). During the 8 d refrigerated storage period, the film suppressed total viable counts (TVC), slowed the increase in pH, and retarded total volatile basic nitrogen (TVB-N) accumulation, thereby maintaining acceptable microbiological quality throughout the observation period. Compared with the unwrapped, PE, and CS-film control groups, the treated samples showed better preservation performance over the tested storage period. Overall, the incorporation of Cur/β-CD provides a simple strategy for improving the mechanical strength, moisture barrier properties, antibacterial activity, and preservation performance of CS films during refrigerated storage, highlighting their potential for active packaging of chilled aquatic products. Full article

(This article belongs to the Section Macromolecular Crystals)

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15 pages, 2434 KB

Open AccessArticle

Linear and Nonlinear Dynamics of Crystals with B2 (CsCl) Structure

by Dina U. Abdullina, Sergey V. Dmitriev, Ilya S. Sugonyako, Arseny M. Kazakov and Elena A. Korznikova

Crystals 2026, 16(5), 286; https://doi.org/10.3390/cryst16050286 - 25 Apr 2026

Abstract

This study investigates the phenomenon of supratransmission in three-dimensional crystals with a B2 (CsCl) structure, employing classical molecular dynamics with β-Fermi–Pasta–Ulam–Tsingou potentials up to fourth-nearest neighbors. We analyze energy transfer from a harmonically driven surface into the crystal bulk across various frequency regimes [...] Read more.

This study investigates the phenomenon of supratransmission in three-dimensional crystals with a B2 (CsCl) structure, employing classical molecular dynamics with β-Fermi–Pasta–Ulam–Tsingou potentials up to fourth-nearest neighbors. We analyze energy transfer from a harmonically driven surface into the crystal bulk across various frequency regimes relative to the phonon spectrum. While low-amplitude excitation results in energy transmission only within the phononic bands, high-amplitude driving triggers supratransmission in the phononic gap and above the optical band. Our results demonstrate that in these nonlinear regimes, energy is transported not by linear phonon waves but by discrete breathers (DBs) emitted quasi-periodically from the surface. A key finding is the distinct sublattice selectivity of these excitations: gap DBs propagate primarily along the heavy atom sublattice, whereas above-spectrum DBs travel along the light atom sublattice. We quantify the velocities and oscillation periods of these localized modes, revealing their critical role in bypassing linear spectral restrictions. These findings provide new insights into nonlinear energy transport in binary alloys and suggest potential applications for controlling heat flow and signal processing in crystals. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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10 pages, 3288 KB

Open AccessArticle

Structure of Agmatinase from Klebsiella pneumoniae and the Active Site Comparison with Its Structural Homologues

by So Yeon Lee, Hyo Been Jin and Hyun Ho Park

Crystals 2026, 16(5), 285; https://doi.org/10.3390/cryst16050285 - 25 Apr 2026

Abstract

Agmatinase (SpeB) catalyzes the hydrolysis of agmatine to produce putrescine, a key step in bacterial polyamine biosynthesis. Here, we report the crystal structure of SpeB from Klebsiella pneumoniae (kpSpeB) and characterize its oligomeric and active-site architecture. SEC–MALS analysis demonstrates that kpSpeB forms a [...] Read more.

Agmatinase (SpeB) catalyzes the hydrolysis of agmatine to produce putrescine, a key step in bacterial polyamine biosynthesis. Here, we report the crystal structure of SpeB from Klebsiella pneumoniae (kpSpeB) and characterize its oligomeric and active-site architecture. SEC–MALS analysis demonstrates that kpSpeB forms a canonical hexamer in solution. Structural comparison reveals high similarity to Escherichia coli SpeB and other members of the arginase superfamily, including proclavaminic acid amidino hydrolase (PAH) and guanidine hydrolase (GdmH). Despite strong conservation of residues coordinating the binuclear Mn²⁺ center, subtle differences in metal positioning and cavity geometry were observed. Surface analysis indicates variations in active-site cavity volume among homologues, with partial occlusion in GdmH due to a bulky tryptophan residue. These findings suggest that minor adjustments in metal coordination and cavity architecture may fine-tune substrate selectivity while preserving the conserved catalytic framework of the arginase superfamily. Full article

(This article belongs to the Section Biomolecular Crystals)

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18 pages, 60393 KB

Open AccessArticle

Mineralogical Characteristics of White Nephrite from Dikou, Fujian Province, Southeastern China

by Shuo Ran and Yingxin Liu

Crystals 2026, 16(5), 284; https://doi.org/10.3390/cryst16050284 - 24 Apr 2026

Abstract

Nephrite is a significant jade resource, and systematic investigation of its deposits contributes to regional metallogenic synthesis and exploration targeting. The recently discovered white nephrite deposit in the Dikou area, Fujian Province, remains inadequately characterized. This study presents a comprehensive mineralogical investigation employing [...] Read more.

Nephrite is a significant jade resource, and systematic investigation of its deposits contributes to regional metallogenic synthesis and exploration targeting. The recently discovered white nephrite deposit in the Dikou area, Fujian Province, remains inadequately characterized. This study presents a comprehensive mineralogical investigation employing polarizing microscopy, scanning electron microscopy, electron probe microanalysis, X-ray powder diffraction and laser Raman spectroscopy to elucidate the mineralogical and petrochemical characteristics of Dikou nephrite and constrain its genesis. The results demonstrate that tremolite constitutes the predominant mineral phase, accompanied by abundant diopside and quartz, with minor dolomite, prehnite, and apatite. Based on subtle compositional variations, tremolite can be categorized into two generations: early metasomatic Tr-I and late-stage Tr-II. All tremolite samples exhibit Fe-depleted, Mg-enriched composition with Mg# > 0.99. The mineral assemblage and textural relationships record multiple episodes of hydrothermal metasomatism. Integrated with the regional geological constraints, the deposit formation is genetically linked to the Neoproterozoic–Early Paleozoic ocean–continent transition of the South China Plate and is classified as D-type nephrite. The Dikou nephrite exhibits the mineral assemblage typical of dolomite-related deposits, displaying a distinctive felt-like fibrous texture that yields a homogeneous structure and superior aesthetic quality. Its Fe-depleted composition imparts a notably lighter coloration relative to D-type nephrite from other deposits. This study advances understanding of Dikou nephrite genesis, highlights the diversity of metallogenic environments in Fujian Province, and provides a theoretical framework for exploration of analogous deposits. Full article

(This article belongs to the Special Issue Modern Gem Crystals: Synthesis, Characterization, Genesis and Intelligent Analysis)

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23 pages, 3826 KB

Open AccessArticle

Pt-Modified 3D NiCu Foam Catalysts for Enhanced Sodium Borohydride Electrooxidation

by Žana Mickevičienė, Aldona Balčiūnaitė, Dijana Šimkūnaitė, Jūratė Vaičiūnienė, Loreta Tamašauskaitė-Tamašiūnaitė and Eugenijus Norkus

Crystals 2026, 16(5), 283; https://doi.org/10.3390/cryst16050283 (registering DOI) - 24 Apr 2026

Abstract

We report a straightforward and scalable strategy for the fabrication of three-dimensional Ni-rich bimetallic NiCu foam coatings on Ti substrates ((NiCu)_foam/Ti) via dynamic hydrogen bubble templating (DHBT) electrodeposition, followed by modification with an ultralow amount of Pt to construct an efficient [...] Read more.

We report a straightforward and scalable strategy for the fabrication of three-dimensional Ni-rich bimetallic NiCu foam coatings on Ti substrates ((NiCu)_foam/Ti) via dynamic hydrogen bubble templating (DHBT) electrodeposition, followed by modification with an ultralow amount of Pt to construct an efficient ternary Ni–Cu–Pt catalytic system. The resulting foams exhibit highly porous dendritic architectures with interconnected channels, enabling a high density of electrochemically active sites and uniform metal distribution throughout the framework. Structural and compositional analyses (SEM–EDX) reveal a Ni-dominant composition (28.09–34.61 mg cm⁻²), with significantly lower Cu content (2.47–4.16 mg cm⁻²) and ultralow Pt loading (9.63–19.04 μg cm⁻²), maximizing catalytic efficiency while minimizing noble metal usage. Electrochemical studies in alkaline media demonstrate that the NiCu foam possesses intrinsic borohydride electrooxidation activity, which is substantially enhanced upon Pt incorporation, delivering a threefold increase in activity compared to the unmodified foam and outperforming bulk Pt. This improvement is attributed to the synergistic interplay within the Ni-rich ternary system, where trace Pt acts as a highly effective promoter. When implemented as anodes in NaBH₄–H₂O₂ fuel cells, Pt(NiCu)_foam/Ti achieves peak power densities of 239 and 301.6 mW cm⁻² at 25 °C and 55 °C, respectively. Overall, this study presents a cost-effective and scalable route to high-performance electrocatalysts for alkaline direct borohydride fuel cells, significantly reducing reliance on noble metals while maintaining superior activity. Full article

(This article belongs to the Special Issue Advances and Perspectives in Noble Metal Nanoparticles)

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