Crystals

9 pages, 4348 KB

Open AccessEditor’s ChoiceArticle

Surface Electronic Structure of Cr Doped Bi₂Se₃ Single Crystals

by Turgut Yilmaz, Xiao Tong, Zhongwei Dai, Jerzy T. Sadowski, Genda Gu, Kenya Shimada, Sooyeon Hwang, Kim Kisslinger, Elio Vescovo and Boris Sinkovic

Crystals 2024, 14(9), 812; https://doi.org/10.3390/cryst14090812 - 14 Sep 2024

Viewed by 1950

Abstract

Here, by using angle-resolved photoemission spectroscopy, we showed that Bi_2−xCr_xSe₃ single crystals have a distinctly well-defined band structure with a large bulk band gap and undistorted topological surface states. These spectral features are unlike their thin film forms [...] Read more.

Here, by using angle-resolved photoemission spectroscopy, we showed that Bi_2−xCr_xSe₃ single crystals have a distinctly well-defined band structure with a large bulk band gap and undistorted topological surface states. These spectral features are unlike their thin film forms in which a large nonmagnetic gap with a distorted band structure was reported. We further provide laser-based high resolution photoemission data which reveal a Dirac point gap even in the pristine sample. The gap becomes more pronounced with Cr doping into the bulk of Bi₂Se₃. These observations show that the Dirac point can be modified by the magnetic impurities as well as the light source. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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48 pages, 7039 KB

Open AccessEditor’s ChoiceReview

A Review of Nanocarbon-Based Anode Materials for Lithium-Ion Batteries

by Nagaraj Nandihalli

Crystals 2024, 14(9), 800; https://doi.org/10.3390/cryst14090800 - 10 Sep 2024

Cited by 8 | Viewed by 5988

Abstract

Renewable and non-renewable energy harvesting and its storage are important components of our everyday economic processes. Lithium-ion batteries (LIBs), with their rechargeable features, high open-circuit voltage, and potential large energy capacities, are one of the ideal alternatives for addressing that endeavor. Despite their [...] Read more.

Renewable and non-renewable energy harvesting and its storage are important components of our everyday economic processes. Lithium-ion batteries (LIBs), with their rechargeable features, high open-circuit voltage, and potential large energy capacities, are one of the ideal alternatives for addressing that endeavor. Despite their widespread use, improving LIBs’ performance, such as increasing energy density demand, stability, and safety, remains a significant problem. The anode is an important component in LIBs and determines battery performance. To achieve high-performance batteries, anode subsystems must have a high capacity for ion intercalation/adsorption, high efficiency during charging and discharging operations, minimal reactivity to the electrolyte, excellent cyclability, and non-toxic operation. Group IV elements (Si, Ge, and Sn), transition-metal oxides, nitrides, sulfides, and transition-metal carbonates have all been tested as LIB anode materials. However, these materials have low rate capability due to weak conductivity, dismal cyclability, and fast capacity fading owing to large volume expansion and severe electrode collapse during the cycle operations. Contrarily, carbon nanostructures (1D, 2D, and 3D) have the potential to be employed as anode materials for LIBs due to their large buffer space and Li-ion conductivity. However, their capacity is limited. Blending these two material types to create a conductive and flexible carbon supporting nanocomposite framework as an anode material for LIBs is regarded as one of the most beneficial techniques for improving stability, conductivity, and capacity. This review begins with a quick overview of LIB operations and performance measurement indexes. It then examines the recently reported synthesis methods of carbon-based nanostructured materials and the effects of their properties on high-performance anode materials for LIBs. These include composites made of 1D, 2D, and 3D nanocarbon structures and much higher Li storage-capacity nanostructured compounds (metals, transitional metal oxides, transition-metal sulfides, and other inorganic materials). The strategies employed to improve anode performance by leveraging the intrinsic features of individual constituents and their structural designs are examined. The review concludes with a summary and an outlook for future advancements in this research field. Full article

(This article belongs to the Special Issue The Development of Advanced Materials for Electrochemical Energy Conversion and Storage)

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22 pages, 25791 KB

Open AccessEditor’s ChoiceArticle

In Situ Synthesis and Characterization of Graphitic Carbon Nitride/Metakaolin Composite Photocatalysts Using a Commercial Kaolin

by Balázs Zsirka, Orsolya Fónagy, Veronika Vágvölgyi, Tatjána Juzsakova, Lajos Fodor and Csilla Őze

Crystals 2024, 14(9), 793; https://doi.org/10.3390/cryst14090793 - 7 Sep 2024

Viewed by 1691

Abstract

Kaolin-based graphitic carbon nitride (g-CNx) composite photocatalysts were synthesized from a urea precursor using a commercial kaolin. Structural characterization by X-ray diffraction and infrared spectroscopy (FTIR) verified the successful thermal polycondensation of g-CNx along the thermal dehydroxylation of kaolinite to metakaolin at 550 [...] Read more.

Kaolin-based graphitic carbon nitride (g-CNx) composite photocatalysts were synthesized from a urea precursor using a commercial kaolin. Structural characterization by X-ray diffraction and infrared spectroscopy (FTIR) verified the successful thermal polycondensation of g-CNx along the thermal dehydroxylation of kaolinite to metakaolin at 550 °C. The g-CNx content of the composites were estimated by thermogravimetry and CHN analysis, ranging from ca. 87 m/m% to ca. 2 m/m% of dry mass. The addition of kaolin during the composite synthesis was found to have a significant effect: the yield of in situ formed g-CNx drastically decreased (from ca. 4.9 m/m% to 3.8–0.1 m/m%) with increasing kaolin content. CHN and FTIR indicated the presence of nitrogen-rich g-CNx, having a specific surface area of 50 m²/g, which synergistically increased after composite synthesis to 67–82 m²/g. Estimated optical band gaps indicated the affinity to absorb in the visible light spectrum (λ < 413 nm). Photocatalytic activity upon both UV and artificial sunlight irradiation was observed by hydroxyl radical evolution, however, without the synergistic effect expected from the favorable porosity. Full article

(This article belongs to the Section Hybrid and Composite Crystalline Materials)

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13 pages, 5828 KB

Open AccessEditor’s ChoiceArticle

Influence of the Acetylene Flow Rate and Process Pressure on the Carbon Deposition Behavior by Thermal Chemical Vapor Deposition Process

by Gi-Hoon Kwon, Byoungho Choi, Young-Kook Lee and Kyoungil Moon

Crystals 2024, 14(9), 782; https://doi.org/10.3390/cryst14090782 - 31 Aug 2024

Cited by 1 | Viewed by 2103

Abstract

We used the chemical vapor deposition process to deposit carbon film at a high temperature (900 °C). The carbon films were deposited on AISI 1006 foils using an acetylene gas. We analyzed the carbon film deposited on the surface using Raman spectroscopy, scanning [...] Read more.

We used the chemical vapor deposition process to deposit carbon film at a high temperature (900 °C). The carbon films were deposited on AISI 1006 foils using an acetylene gas. We analyzed the carbon film deposited on the surface using Raman spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy to define changes in the bonding structure of the carbon film. The results of Raman spectroscopy and high-resolution transmission electron microscopy revealed that as the acetylene flow rate increased, the shape of the deposited carbon film changed from graphene to graphite. In addition, in order to compare the quality of the carbon film in terms of mechanical and electrical properties, carbon films treated under various conditions were closely analyzed using nano-indenter and a sheet resistance meter. Therefore, the optimal condition (1 Torr-50 sccm) was selected in which graphene was uniformly deposited and had the lowest electrical resistance (500 Ω/sq) and highest hardness (12 GPa). Full article

(This article belongs to the Section Crystal Engineering)

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13 pages, 6423 KB

Open AccessEditor’s ChoiceArticle

A Cost-Effective Strategy to Modify the Electrical Properties of PEDOT:PSS via Femtosecond Laser Irradiation

by Chi Zhang, Jiayue Zhou, Rui Han, Cheng Chen, Han Jiang, Xiaopeng Li, Yong Peng, Dasen Wang and Kehong Wang

Crystals 2024, 14(9), 775; https://doi.org/10.3390/cryst14090775 - 30 Aug 2024

Cited by 1 | Viewed by 1562

Abstract

Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) is a commonly used conductive polymer in organic optoelectronic devices. The conductivity and work function of the PEDOT:PSS are two important parameters that significantly determine the performance of the associated optoelectronic device. Traditionally, some solvents were doped in PEDOT:PSS solution or [...] Read more.

Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) is a commonly used conductive polymer in organic optoelectronic devices. The conductivity and work function of the PEDOT:PSS are two important parameters that significantly determine the performance of the associated optoelectronic device. Traditionally, some solvents were doped in PEDOT:PSS solution or soaked in PEDOT:PSS film to improve its electrical conductivity, but they damaged the integrity of PEDOT:PSS and reduce the film’s work function. Herein, for the first time, we use femtosecond laser irradiation to modify the electrical conductivity and work function of PEDOT:PSS film. We proposed that the femtosecond laser irradiation could selectively remove the superficial insulative PSS, thereby improving the electrical conductivity of the film. The femtosecond laser-irradiated PEDOT:PSS film was further employed as a hole injection layer within cutting-edge perovskite light-emitting diodes (PeLEDs). A maximum luminosity of 950 cd/m² was obtained in PeLEDs irradiated by femtosecond laser light in thin films, which is five times higher than that of the controlled device. Moreover, the external quantum efficiency of the devices was also increased from 4.6% to 6.3%. This work paved a cost-effective way to regulate the electrical properties of the PEDOT:PSS film. Full article

(This article belongs to the Section Organic Crystalline Materials)

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15 pages, 9936 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Effect of Methylxanthines on Urate Crystallization: In Vitro Models of Gout and Renal Calculi

by Jaume Dietrich, Felix Grases and Antonia Costa-Bauza

Crystals 2024, 14(9), 768; https://doi.org/10.3390/cryst14090768 - 29 Aug 2024

Cited by 2 | Viewed by 2023

Abstract

Background: Common forms of pathological crystals are uric acid or urates, which are responsible for gout, urolithiasis, and other conditions. Methods: We used a kinetic–turbidimetric crystallization assay to evaluate the effect of ten specific methylxanthines on the crystallization of monosodium urate, potassium urate, [...] Read more.

Background: Common forms of pathological crystals are uric acid or urates, which are responsible for gout, urolithiasis, and other conditions. Methods: We used a kinetic–turbidimetric crystallization assay to evaluate the effect of ten specific methylxanthines on the crystallization of monosodium urate, potassium urate, and ammonium urate in conditions that mimicked urine. We also studied the effect of different levels of 7-methylxanthine in the presence of other biological compounds (albumin and hyaluronic acid) on the solubility of monosodium urate in conditions that mimicked synovial fluid. Results: The results showed that 7-methylxanthine in the range of 16.61–49.84 mg/L inhibited the crystallization of each urate when the initial urate concentration was 3 × 10⁻³ M (500 mg/L) and the conditions mimicked urine, and that the greatest inhibitory effect was for monosodium urate. In addition, 7-methylxanthine at a concentration of 25 mg/L totally prevented the crystallization of monosodium urate at an initial urate concentration of 2.38 × 10⁻³ M (400 mg/L) in conditions that mimicked synovial fluid. Moreover, at a low concentration of 7-methylxanthine, albumin and hyaluronic acid increased this inhibitory effect. Conclusions: Our in vitro results demonstrate that 7-methylxanthine inhibits the crystallization of urates in conditions that mimic synovial fluid and urine. Full article

(This article belongs to the Special Issue Pathological Biomineralization: Recent Advances and Perspectives)

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13 pages, 5500 KB

Open AccessEditor’s ChoiceArticle

Predicting X-ray Diffraction Quality of Protein Crystals Using a Deep-Learning Method

by Yujian Shen, Zhongjie Zhu, Qingjie Xiao, Kanglei Ye, Qisheng Wang, Yue Wang and Bo Sun

Crystals 2024, 14(9), 771; https://doi.org/10.3390/cryst14090771 - 29 Aug 2024

Viewed by 2086

Abstract

Over the past few decades, significant advancements in protein crystallography have led to a steady increase in the number of determined protein structures. The X-ray diffraction experiment remains one of the primary methods for investigating protein crystal structures. To obtain information about crystal [...] Read more.

Over the past few decades, significant advancements in protein crystallography have led to a steady increase in the number of determined protein structures. The X-ray diffraction experiment remains one of the primary methods for investigating protein crystal structures. To obtain information about crystal structures, a sufficient number of high-quality crystals are typically required. At present, X-ray diffraction experiments on protein crystals primarily rely on manual selection by experimenters. However, each experiment is not only costly but also time-consuming. To address the urgent need for automatic selection of the proper protein crystal candidates for X-ray diffraction experiments, a protein-crystal-quality classification network, leveraging the ConvNeXt network architecture, is proposed. Subsequently, a new database is created, which includes protein crystal images and their corresponding X-ray diffraction images. Additionally, a novel method for categorizing protein quality based on the number of diffraction spots and the resolution is introduced. To further enhance the network’s focus on essential features of protein crystal images, a CBAM (Convolutional Block Attention Module) attention mechanism is incorporated between convolution layers. The experimental results demonstrate that the network achieves significant improvement in performing the prediction task, thereby effectively enhancing the probability of high-quality crystals being selected by experimenters. Full article

(This article belongs to the Special Issue Protein Crystallography: The State of the Art)

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30 pages, 33889 KB

Open AccessEditor’s ChoiceReview

A Review of Additively Manufactured Iron-Based Shape Memory Alloys

by Qian Sun, Xiaojun Tan, Mingjun Ding, Bo Cao and Takeshi Iwamoto

Crystals 2024, 14(9), 773; https://doi.org/10.3390/cryst14090773 - 29 Aug 2024

Cited by 6 | Viewed by 3737

Abstract

Iron-based shape memory alloys (Fe-SMAs), traditionally manufactured, are favored in engineering applications owing to their cost-effectiveness and ease of fabrication. However, the conventional manufacturing process of Fe-SMAs is time-consuming and raw-material-wasting. In contrast, additive manufacturing (AM) technology offers a streamlined approach to the [...] Read more.

Iron-based shape memory alloys (Fe-SMAs), traditionally manufactured, are favored in engineering applications owing to their cost-effectiveness and ease of fabrication. However, the conventional manufacturing process of Fe-SMAs is time-consuming and raw-material-wasting. In contrast, additive manufacturing (AM) technology offers a streamlined approach to the integral molding of materials, significantly reducing raw material usage and fabrication time. Despite its potential, research on AMed Fe-SMAs remains in its early stages. This review provides updated information on current AM technologies utilized for Fe-SMAs and their applications. It provides an in-depth discussion on how printing parameters, defects, and post-printing microstructure control affect the mechanical properties and shape memory effect (SME) of AMed Fe-SMAs. Furthermore, this review identifies existing challenges in the AMed Fe-SMA approach and proposes future research directions, highlighting potential areas for development. The insights presented aim to guide improvements in the material properties of AMed Fe-SMAs by optimizing printing parameters and enhancing the SME through microstructure adjustment. Full article

(This article belongs to the Special Issue Shape Memory Alloys: Recent Advances and Future Perspectives)

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13 pages, 3083 KB

Open AccessEditor’s ChoiceArticle

Effect of Lattice Misfit on the Stability of the Misfit Layer Compound (SnS)_1+xNbS₂

by Changming Fang

Crystals 2024, 14(9), 756; https://doi.org/10.3390/cryst14090756 - 26 Aug 2024

Cited by 1 | Viewed by 1408

Abstract

The prototype misfit layer compound (SnS)_1.17NbS₂ consists alternatingly of a metallic triatomic NbS₂ layer, in which Nb atoms are sandwiched by S atoms, and an insulating SnS double layer featuring a NaCl-type structure. Here we investigate the effect of [...] Read more.

The prototype misfit layer compound (SnS)_1.17NbS₂ consists alternatingly of a metallic triatomic NbS₂ layer, in which Nb atoms are sandwiched by S atoms, and an insulating SnS double layer featuring a NaCl-type structure. Here we investigate the effect of lattice misfit on the stability and chemical bonding in the misfit layer compound using a first-principles density functional theory approach. The calculations show that for the (SnS)_1+xNbS₂ approximants, the most stable one has x = 0.167, close to the experimental observations. Charge analysis finds a moderate charge transfer from SnS to NbS₂. Sn or S vacancies in the SnS part affect the electronic properties and interlayer interactions. The obtained information here helps in understanding the mechanism of formation and stability of misfit layer compounds and ferecrystals and further contributes to the design of novel multilayer compounds and emerging van der Waals heterostructures. Full article

(This article belongs to the Special Issue Microstructure and Properties of Intermetallic Compounds)

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18 pages, 4999 KB

Open AccessEditor’s ChoiceArticle

Screening, Growing, and Validation by Catalog: Using Synthetic Intermediates from Natural Product Libraries to Discover Fragments for an Aspartic Protease Through Crystallography

by Franziska U. Huschmann, Janis Mueller, Alexander Metz, Moritz Ruf, Johanna Senst, Serghei Glinca, Johannes Schiebel, Andreas Heine and Gerhard Klebe

Crystals 2024, 14(9), 755; https://doi.org/10.3390/cryst14090755 - 25 Aug 2024

Viewed by 1594

Abstract

Fragment screening directly on protein crystals has been applied using AnalytiCon’s collection of intermediates that have been utilized to generate libraries of larger synthetic natural product-like molecules. The fragments with well-balanced physicochemical properties show an impressively high hit rate for a screen using [...] Read more.

Fragment screening directly on protein crystals has been applied using AnalytiCon’s collection of intermediates that have been utilized to generate libraries of larger synthetic natural product-like molecules. The fragments with well-balanced physicochemical properties show an impressively high hit rate for a screen using the aspartic protease endothiapepsin. The subsequent validation and expansion of the discovered fragment hits benefits from AnalytiCon’s comprehensive library design. Since the screened fragments are intermediates that share a common core with larger and closely related analogs with modulated substitution patterns, they allow for the retrieval of off-the-shelf follow-up compounds, which enable the development of design strategies for fragment optimization. A promising bicyclic core scaffold found in several fragment hits could be validated by selecting a set of enlarged follow-up compounds. Due to unexpected changes in binding mode and no significant improvement in ligand efficiency, this series was quickly deemed unsuitable and therefore discontinued. The structures of follow-up compounds of two other fragments helped to evaluate a putative fusion of two overlapping fragment hits. A design concept on how to fuse the two fragments could be proposed and helps to plan a suitable substitution pattern and promising central bridging element. Full article

(This article belongs to the Special Issue Structural Studies in Drug Discovery and Development: From the Lead to the Pharmaceutical Form)

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14 pages, 2477 KB

Open AccessEditor’s ChoiceArticle

Technology and Dielectric Properties of BLT4 Ceramics Modified with Special Glass

by Beata Wodecka-Dus, Jolanta Makowska, Tomasz Pikula, Rafał Panek, Małgorzata Adamczyk-Habrajska and Katarzyna Osińska

Crystals 2024, 14(8), 739; https://doi.org/10.3390/cryst14080739 - 20 Aug 2024

Cited by 1 | Viewed by 1112

Abstract

Lead-boron special glass was doped into Ba_0.996La_0.004Ti_0.999O₃ (BLT4) ceramics in order to control the sintering process and grain growth, consequently obtaining materials with a well-developed microstructure. Changes in the microstructure resulted in a significant decrease in [...] Read more.

Lead-boron special glass was doped into Ba_0.996La_0.004Ti_0.999O₃ (BLT4) ceramics in order to control the sintering process and grain growth, consequently obtaining materials with a well-developed microstructure. Changes in the microstructure resulted in a significant decrease in electrical permittivity along with a substantial increase in its frequency dispersion. Glass-doped ceramics, similar to pure BLT4, are characterized by a first-order phase transition from the ferroelectric phase to the paraelectric phase. The temperature of this transition shifts slightly towards higher values with the increase in glass dopant concentration. Full article

(This article belongs to the Section Polycrystalline Ceramics)

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14 pages, 4227 KB

Open AccessEditor’s ChoiceArticle

Boosted Electrochemical Activity with SnO₂ Nanostructures Anchored on α-Fe₂O₃ for Improved Charge Transfer and Current Density

by Itheereddi Neelakanta Reddy, Bhargav Akkinepally, Jaesool Shim and Cheolho Bai

Crystals 2024, 14(8), 734; https://doi.org/10.3390/cryst14080734 - 18 Aug 2024

Cited by 1 | Viewed by 1368

Abstract

This study presents a straightforward and cost-effective method to enhance the photoelectrochemical (PEC) water-splitting performance of α-Fe₂O₃ (F), SnO₂ (S), and α-Fe₂O₃ decorated with SnO₂ quantum dots (FS) photoanodes in a NaOH electrolyte. The FS [...] Read more.

This study presents a straightforward and cost-effective method to enhance the photoelectrochemical (PEC) water-splitting performance of α-Fe₂O₃ (F), SnO₂ (S), and α-Fe₂O₃ decorated with SnO₂ quantum dots (FS) photoanodes in a NaOH electrolyte. The FS electrode demonstrated a notable improvement in PEC efficiency within the electrolyte. In particular, the generated charges of the FS anode in the NaOH electrolyte reached approximately 12.01 mA cm⁻² under illumination, indicating that the developed heterostructures effectively enhanced kinetics, leading to improved separation of induced carrier pairs. This active carrier-pair separation mechanism contributed considerably to the increased PEC activity in the 0.1 M NaOH electrolyte. The reduction in the bandgap of FS increased its absorption capability in visible light, which further enhanced the current density. Furthermore, the reduction in electrolyte resistance (9.71 Ω), internal resistance (20.19 Ω), charge transfer resistance (3.21 kΩ), Tafel slope (45.5 mV dec-1), limiting current density (−2.09 mA cm⁻²), and exchange current density (−3.68 mA cm⁻²) under illumination at the interface enhanced the charge density of FS. Further, a strong interaction among photoanode nanostructures significantly enhances PEC activity by improving efficient charge separation and transport, reducing recombination rates, and enabling quicker movement of charge carriers to the electrode/electrolyte interface. Thus, this study provides an effective approach to increasing the PEC activity of heterostructures. Full article

(This article belongs to the Special Issue Hybrid Materials for Energy Storage and Conversion)

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12 pages, 5019 KB

Open AccessEditor’s ChoiceArticle

High-Quality Single-Step Growth of GaAs on C-Plane Sapphire by Molecular Beam

by Emmanuel Wangila, Calbi Gunder, Mohammad Zamani-Alavijeh, Fernando Maia de Oliveira, Serhii Kryvyi, Aida Sheibani, Yuriy I. Mazur, Shui-Qing Yu and Gregory J. Salamo

Crystals 2024, 14(8), 724; https://doi.org/10.3390/cryst14080724 - 14 Aug 2024

Cited by 1 | Viewed by 1979

Abstract

We report on the growth of high-quality GaAs semiconductor materials on an AlAs/sapphire substrate by molecular beam epitaxy. The growth of GaAs on sapphire centers on a new single-step growth technique that produces higher-quality material than a previously reported multi-step growth method. Omega-2theta [...] Read more.

We report on the growth of high-quality GaAs semiconductor materials on an AlAs/sapphire substrate by molecular beam epitaxy. The growth of GaAs on sapphire centers on a new single-step growth technique that produces higher-quality material than a previously reported multi-step growth method. Omega-2theta scans confirmed the GaAs (111) orientation. Samples grown at 700 °C displayed the highest crystal quality with minimal defects and strain, evidenced by narrow FWHM values of the rocking curve. By varying the As/Ga flux ratio and the growth temperature, we significantly improved the quality of the GaAs layer on sapphire, as compared to that obtained in multi-step studies. Photoluminescence measurements at room temperature and 77 K further support these findings. This study underscores the critical role of the As/Ga flux ratio and growth temperature in optimizing GaAs epitaxial growth on sapphire. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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21 pages, 6986 KB

Open AccessEditor’s ChoiceArticle

Twin Peaks: Interrogating Otolith Pairs to See Whether They Keep Their Stories Straight

by Clara Lord, Sophie Berland, Vincent Haÿ, Kadda Medjoubi and Philippe Keith

Crystals 2024, 14(8), 705; https://doi.org/10.3390/cryst14080705 - 4 Aug 2024

Cited by 1 | Viewed by 1388

Abstract

To tackle the question of the reliability of otoliths as recorders of individual life events, we compared the information enclosed in otolith pairs: the sagittae pair and the sagitta/lapillus pair. We used the synchrotron XRF scanning imaging method, which enabled the comparison of [...] Read more.

To tackle the question of the reliability of otoliths as recorders of individual life events, we compared the information enclosed in otolith pairs: the sagittae pair and the sagitta/lapillus pair. We used the synchrotron XRF scanning imaging method, which enabled the comparison of this information at both global and hyperfine scales. Using otoliths of diadromous pipefish, we compared element incorporation in each pair with a focus on (i) environment and transition between water bodies with strontium (Sr) and heavy metals, (ii) temporal information and age estimation based on sulphur (S) incorporation, and (iii) otolith growth and biomineralization processes with zinc (Zn). Results show that the global information in terms of Sr and heavy metals given by both otoliths of a pair is the same and that any otolith may be used to retrieve such global data. In terms of S-based growth increment counts, the numbers are the same between two otoliths of the same kind, but the sagitta/lapillus pairs show a significant difference. Hyperfine-scale analysis of element distribution reveals that a given otolith is under the control of specific growth mechanisms, which can lead to heterogeneous elemental incorporation. The present results lead us to consider otolith growth dynamics and biomineralization processes in the context of a fluid mosaic perspective. Full article

(This article belongs to the Section Mineralogical Crystallography and Biomineralization)

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17 pages, 3562 KB

Open AccessEditor’s ChoiceArticle

Electrosynthesis of Co-ZIF Using Bio-Derived Solvents: Electrochemical Evaluation of Synthesised MOFs as a Binder-Free Supercapacitor Electrode in Alkaline Electrolyte

by Vijayakumar Manavalan, Brad Coward, Vesna Najdanovic-Visak and Stephen D. Worrall

Crystals 2024, 14(8), 700; https://doi.org/10.3390/cryst14080700 - 1 Aug 2024

Cited by 1 | Viewed by 1810

Abstract

Supercapacitors hold promise for energy storage due to their exceptional power density and fast charge/discharge cycles. However, their performance hinges on the electrode material. Zeolitic imidazolate frameworks (ZIFs) are attractive options due to their tailorable structure and high surface area. But traditional ZIF [...] Read more.

Supercapacitors hold promise for energy storage due to their exceptional power density and fast charge/discharge cycles. However, their performance hinges on the electrode material. Zeolitic imidazolate frameworks (ZIFs) are attractive options due to their tailorable structure and high surface area. But traditional ZIF synthesis relies on toxic solvents derived from fossil fuels, hindering their envisioned environmental benefit. This study explores using bio-derived solvents for a greener and potentially superior approach. The researchers employed anodic electrodeposition to synthesise cobalt-based ZIFs (Co-ZIFs) as supercapacitor electrode materials. Two linkers (2-methylimidazole and benzimidazole) and two bio-derived solvents (Cyrene^TM and γ-valerolactone (GVL)) were investigated. X-ray diffraction analysis revealed that bio-derived solvents enhanced the crystallinity of Co-ZIFs compared to traditional solvents. Notably, Cyrene^TM promoted better crystallinity for Co-bIM/Co-mIM structures. The Full Width at Half Maximum (FWHM) analysis suggests Cyrene^TM promotes Co-bIM/Co-mIM crystallinity (lower FWHM). Co-mIM in Cyrene^TM exhibits the best crystallinity (FWHM = 0.233) compared to other ZIF samples. Scanning electron microscopy confirmed these findings, showing larger and well-defined crystals for bio-derived solvent-synthesised ZIFs. The choice of solvent significantly impacted the final ZIF structure. While 2-methylimidazole consistently formed ZIF-67 regardless of the solvent, benzimidazole exhibited solvent-dependent behaviour. GVL yielded the highly porous Co-ZIF-12 structure, whereas DMF (N,N-dimethylformamide) and Cyrene^TM produced the less porous ZIF-9. This work reports the first-ever instance of ZIF-12 synthesis via an electrochemical method, highlighting the crucial interplay between solvent and precursor molecule in determining the final ZIF product. The synthesised binder-free Co-ZIF electrodes were evaluated for supercapacitor performance. The capacitance data revealed GVL as the most effective solvent, followed by DMF and then Cyrene^TM. This suggests GVL is the preferred choice for this reaction due to its superior performance. The ZIF-12-based electrode exhibits an impressive specific capacitance (C_sp) of 44 F g⁻¹, significantly higher than those achieved by ZIF-9-Cyrene (1.2 F g⁻¹), ZIF-9-DMF (2.5 F g⁻¹), ZIF-67-GVL (35 F g⁻¹), ZIF-67-Cyrene (6 F g⁻¹), and ZIF-67-DMF (16 F g⁻¹) at 1 A g⁻¹. This surpasses the C_sp of all other ZIFs studied, including high-performing ZIF-67(GVL). ZIF-12(GVL) maintained superior C_sp even at higher current densities, demonstrating exceptional rate capability. Among the bio-derived solvents, GVL outperformed Cyrene^TM. Notably, the Co-bIM in the GVL sample exhibited a ZIF-12-like structure, offering potential advantages due to its larger pores and potentially higher surface area compared to traditional ZIF-67 and ZIF-9 structures. This work presents a significant advancement in Co-ZIF synthesis. By utilising bio-derived solvents, it offers a more sustainable and potentially superior alternative. This paves the way for the eco-friendly production of Co-ZIFs with improved properties for supercapacitors, gas separation, catalysis, and other applications. Full article

(This article belongs to the Special Issue New Materials for Electrochemical Energy Storage Systems and Catalysis)

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15 pages, 5755 KB

Open AccessEditor’s ChoiceArticle

Synthesis and Investigation of ReSe₂ Thin Films Obtained from Magnetron Sputtered Re and ReO_x

by Kevon Kadiwala, Luize Dipane, Eriks Dipans, Arturs Bundulis, Martins Zubkins, Andrejs Ogurcovs, Jevgenijs Gabrusenoks, Dmitry Bocharov, Edgars Butanovs and Boris Polyakov

Crystals 2024, 14(8), 690; https://doi.org/10.3390/cryst14080690 - 28 Jul 2024

Cited by 2 | Viewed by 1589

Abstract

The promise of two-dimensional (2D) rhenium diselenide (ReSe₂) in electronics and optoelectronics has sparked considerable interest in this material. However, achieving the growth of high-quality ReSe₂ thin films on a wafer scale remains a significant challenge. In this study, we [...] Read more.

The promise of two-dimensional (2D) rhenium diselenide (ReSe₂) in electronics and optoelectronics has sparked considerable interest in this material. However, achieving the growth of high-quality ReSe₂ thin films on a wafer scale remains a significant challenge. In this study, we adopted a two-step method to produce ReSe₂ thin films by combining magnetron sputtering of Re and ReO_x onto flat substrates with subsequent selenization via atmospheric pressure chemical vapor transport (CVT). After analyzing the produced films using X-ray diffraction to identify the crystalline phase in formed thin film and scanning electron microscopy (SEM) to examine surface morphology, it was determined that the suitable temperature range for the 15 min selenization process with CVT is 650 °C–750 °C. Further investigation of these optimally produced ReSe₂ thin films included atomic force microscopy (AFM), X-ray photoelectron spectroscopy, and Raman spectroscopy. The bulk electrical analysis of these films and AFM and SEM surface morphology revealed a strong reliance on the type of precursor material used for their synthesis, whereas optical measurements indicated a potential for the films in non-linear optics applications, irrespective of the precursor or temperature used. This study not only provides a new pathway for the growth of ReSe₂ films but also sheds light on the synthesis approaches of other 2D transition metal dichalcogenide materials. Full article

(This article belongs to the Special Issue Two-Dimensional Materials: Synthesis, Characterization and Device Applications)

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15 pages, 6194 KB

Open AccessEditor’s ChoiceArticle

Analysis of the Anisotropic Cyclic Material Behavior of EN AW-1050A H24 Derived from Strain-Controlled Testing Using a Clip-On Extensometer and an Optical System

by Tim Korschinsky, Benjamin Möller, Marvin Kiel and Matthias Hecht

Crystals 2024, 14(8), 686; https://doi.org/10.3390/cryst14080686 - 27 Jul 2024

Cited by 2 | Viewed by 2400

Abstract

Due to its good conductive properties, unalloyed (pure) aluminum, such as EN AW-1050A H24, finds new fields of application in electromobility. To optimize components, the cyclic material behavior must be understood and described precisely as a foundation of a proper fatigue life estimation. [...] Read more.

Due to its good conductive properties, unalloyed (pure) aluminum, such as EN AW-1050A H24, finds new fields of application in electromobility. To optimize components, the cyclic material behavior must be understood and described precisely as a foundation of a proper fatigue life estimation. Various cyclic tests were performed to not only derive the cyclic parameters to describe the material but also to find the most suitable procedure to deal with the challenges faced during the experiments. The main point of interest is the comparison between a surface-mounted clip-on extensometer and an optical system both used for strain control in cyclic tests. For the analysis of the anisotropic behavior of EN AW-1050A H24, un-notched flat specimens were extracted from sheet metal lengthways and crossways in respect to the rolling direction. While the cyclic material behavior for specimens of both directions of extraction is characterized by cyclic softening in general, the specimens extracted crossways show a strain-amplitude-dependent cyclic softening with strong strain localization especially at the contact points of the knives of the clip-on extensometer leading to an increased quantity of invalid experiments as well as sudden fractures. In the study, it was possible to show the benefits of a contactless optical strain control system when dealing with very soft metallic materials such as EN AW-1050A H24. Full article

(This article belongs to the Special Issue Fatigue and Fracture of Anisotropic Materials)

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15 pages, 8549 KB

Open AccessEditor’s ChoiceArticle

Advances in the Parameter Space Concept towards Picometer Precise Crystal Structure Refinement—A Resolution Study

by Matthias Zschornak, Christian Wagner, Melanie Nentwich, Muthu Vallinayagam and Karl F. Fischer

Crystals 2024, 14(8), 684; https://doi.org/10.3390/cryst14080684 - 26 Jul 2024

Cited by 1 | Viewed by 1475

Abstract

The Parameter Space Concept (PSC) is an alternative approach to solving and refining (partial) crystal structures from very few pre-chosen X-ray or neutron diffraction amplitudes without the use of Fourier inversion. PSC interprets those amplitudes as piecewise analytic hyper-surfaces, so-called isosurfaces, in the [...] Read more.

The Parameter Space Concept (PSC) is an alternative approach to solving and refining (partial) crystal structures from very few pre-chosen X-ray or neutron diffraction amplitudes without the use of Fourier inversion. PSC interprets those amplitudes as piecewise analytic hyper-surfaces, so-called isosurfaces, in the Parameter Space, which is spanned by the spatial coordinates of all atoms of interest. The intersections of all isosurfaces constitute the (possibly degenerate) structure solution. The present feasibility study investigates the La and Sr split position of the potential high-temperature super-conductor (La_0.5Sr_1.5)MnO₄,

I 4

/mmm, with a postulated total displacement between La and Sr of a few

p

m

by theoretical amplitudes of pre-selected

0 0 l

reflections (

l = 2, 4, \dots, 20

). The revision of 15-year-old results with state-of-the-art computing equipment enhances the former simplified model by varying the scattering power ratio

f_{\begin{matrix} La \end{matrix}} / f_{\begin{matrix} Sr \end{matrix}}

, as exploitable by means of resonant scattering contrast at synchrotron facilities, and irrevocably reveals one of the two originally proposed solutions as being a “blurred” pseudo-solution. Finally, studying the resolution limits of PSC as a function of intensity errors by means of Monte-Carlo simulations shows both that the split can only be resolved for sufficiently low errors and, particularly for the resonant scattering contrast, a theoretical precision down to

\pm 0.19

p

m

can be achieved for this specific structural problem. Full article

(This article belongs to the Section Crystal Engineering)

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29 pages, 18161 KB

Open AccessEditor’s ChoiceReview

Liquid-Crystalline Supermolecules Inducing Layer Fluctuations: From Hierarchical to Dissipative Structures

by Atsushi Yoshizawa

Crystals 2024, 14(8), 681; https://doi.org/10.3390/cryst14080681 - 26 Jul 2024

Cited by 3 | Viewed by 2438

Abstract

Liquid crystals, which have both liquid and solid properties, inevitably exhibit fluctuations. Some frustrated liquid-crystalline phases with a hierarchical structure, such as cybotactic nematic, modulated smectic, and bicontinuous cubic phases, are fascinating fluctuation-induced phases. In addition to these equilibrium phases, a pattern formation [...] Read more.

Liquid crystals, which have both liquid and solid properties, inevitably exhibit fluctuations. Some frustrated liquid-crystalline phases with a hierarchical structure, such as cybotactic nematic, modulated smectic, and bicontinuous cubic phases, are fascinating fluctuation-induced phases. In addition to these equilibrium phases, a pattern formation that is a nonequilibrium order through fluctuation is one of the most attractive research areas in soft matter. In this review, the studies on producing these fluctuation-induced orders in liquid crystals are described. Liquid-crystalline supermolecules in which several mesogens are connected via a flexible spacer have been designed. They have not only a characteristic shape but also an intra-molecular dynamic order. The supermolecules induce the fluctuations in layer structures at a molecular level, producing from the frustrated hierarchical to dynamic dissipative structures. In addition to reviewing molecular design for the hierarchical structures, the pattern propagation in a smectic phase is discussed based on the rotation of smectic blocks through Rayleigh–Bénard convection. Full article

(This article belongs to the Special Issue Advances in Liquid Crystal Dimers and Oligomers)

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15 pages, 530 KB

Open AccessEditor’s ChoiceArticle

Directional Acoustic Bulk Waves in a 2D Phononic Crystal

by Pierre A. Deymier, Jérôme O. Vasseur, Keith Runge, Krishna Muralidharan, Alexander Khanikaev and Andrea Alù

Crystals 2024, 14(8), 674; https://doi.org/10.3390/cryst14080674 - 24 Jul 2024

Cited by 1 | Viewed by 1542

Abstract

We used the transfer matrix method to investigate the conditions supporting the existence of directional bulk waves in a two-dimensional (2D) phononic crystal. The 2D crystal was a square lattice of unit cells composed of rectangular subunits constituted of two different isotropic continuous [...] Read more.

We used the transfer matrix method to investigate the conditions supporting the existence of directional bulk waves in a two-dimensional (2D) phononic crystal. The 2D crystal was a square lattice of unit cells composed of rectangular subunits constituted of two different isotropic continuous media. We established the conditions on the geometry of the phononic crystal and its constitutive media for the emergence of waves, which, for the same handedness, exhibited a non-zero amplitude in one direction within the crystal’s 2D Brillouin zone and zero amplitude in the opposite direction. Due to time-reversal symmetry, the crystal supported propagation in the reverse direction for the opposite handedness. These features may enable robust directional propagation of bulk acoustic waves and topological acoustic technology. Full article

(This article belongs to the Special Issue Metamaterials and Their Devices)

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12 pages, 3853 KB

Open AccessEditor’s ChoiceArticle

An Analysis of Protein Crystals Grown under Microgravity Conditions

by Keegan Jackson, Rebecca Hoff, Hannah Wright, Ashley Wilkinson, Frances Brewer, Amari Williams, Ben Whiteside, Mark R. Macbeth and Anne M. Wilson

Crystals 2024, 14(7), 652; https://doi.org/10.3390/cryst14070652 - 16 Jul 2024

Cited by 2 | Viewed by 3018

Abstract

Microgravity has been shown to be an excellent tool for protein crystal formation. A retrospective analysis of all publicly available crystallization data, including many that have not yet been published, clearly demonstrates the value of the microgravity environment for producing superior protein crystals. [...] Read more.

Microgravity has been shown to be an excellent tool for protein crystal formation. A retrospective analysis of all publicly available crystallization data, including many that have not yet been published, clearly demonstrates the value of the microgravity environment for producing superior protein crystals. The parameters in the database (the Butler Microgravity Protein Crystal Database, BμCDB) that were evaluated pertain to both crystal morphology and diffraction quality. Success metrics were determined as improvements in size, definition, uniformity, mosaicity, diffraction quality, resolution limits, and B factor. The proteins in the databases were evaluated by molecular weight, protein type, the number of subunits, space group, and Mattew’s Coefficient. Compared to ground experiments, crystals grown in a microgravity environment continue to show improvement across all metrics evaluated. General trends as well as numerical differences are included in the assessment of the BμCDB. The microgravity environment improves crystal formation across a spectrum of metrics and the datasets utilized for this investigation are excellent tools for this evaluation. Full article

(This article belongs to the Section Biomolecular Crystals)

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11 pages, 3629 KB

Open AccessEditor’s ChoiceArticle

Thermal Behavior of Clinoptilolite

by Magdalena Król, Jakub Dechnik, Patryk Szymczak, Bartosz Handke, Magdalena Szumera and Paweł Stoch

Crystals 2024, 14(7), 646; https://doi.org/10.3390/cryst14070646 - 14 Jul 2024

Cited by 5 | Viewed by 2302

Abstract

Understanding the thermal properties of zeolites is crucial for their industrial applications. This study explores the thermal stability and dehydration process of clinoptilolite using high-temperature X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Clinoptilolite’s thermal decomposition was monitored from 25 °C to [...] Read more.

Understanding the thermal properties of zeolites is crucial for their industrial applications. This study explores the thermal stability and dehydration process of clinoptilolite using high-temperature X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Clinoptilolite’s thermal decomposition was monitored from 25 °C to 1200 °C, with results analyzed based on its crystal structure. Principal components analysis (PCA) of the DRIFT spectra indicated progressive water removal and dehydration upon heating, leading to the formation of hydrogen bonds. Thermogravimetric analysis (TGA) revealed a two-step endothermic weight loss: initially, physically adsorbed water was lost up to 100 °C, followed by the removal of tightly bound water and hydroxyl groups until 800 °C. Clinoptilolite remained the dominant phase up to 800 °C, after which albite and cristobalite took over. Rietveld refinement showed that the sample initially contained 70% clinoptilolite, 24% albite, and 6% cristobalite. Above 800 °C, clinoptilolite disappeared, leaving 93% albite and 7% cristobalite. FT-IR spectra changes due to water loss were evident: drying of adsorbed water occurred up to 75 °C and minimal changes were observed from 75 °C to 135 °C, followed by further dehydration until 240 °C. Complete dehydration was confirmed by the disappearance of OH stretching vibration bands by 395 °C, consistent with TGA findings. Full article

(This article belongs to the Section Hybrid and Composite Crystalline Materials)

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18 pages, 4122 KB

Open AccessEditor’s ChoiceArticle

Crystallization of Calcium Carbonate and Calcium Phosphate Phases in Silica Hydrogel: Morphological and Compositional Characterization

by Nuria Sánchez-Pastor, André Jorge Pinto, Pablo del Buey Fernández and José Manuel Astilleros

Crystals 2024, 14(7), 635; https://doi.org/10.3390/cryst14070635 - 10 Jul 2024

Cited by 1 | Viewed by 2226

Abstract

The present study showcases a series of crystallization experiments using a specially designed double diffusion system to grow crystals belonging to the calcium carbonate–phosphate system. The experimental U-shaped device comprised two vertical solution containers, separated by a horizontal column of silica hydrogel. Each [...] Read more.

The present study showcases a series of crystallization experiments using a specially designed double diffusion system to grow crystals belonging to the calcium carbonate–phosphate system. The experimental U-shaped device comprised two vertical solution containers, separated by a horizontal column of silica hydrogel. Each container was filled with 0.5 M CaCl₂ and 0.5 M Na₂CO₃ solutions, which diffused through the gel column over time. Na₃PO₄ solutions, with 50 and 500 ppm concentrations, were incorporated into the gel in different experiments, resulting in a homogeneous distribution of phosphate concentrations within the diffusion column. After 15- and 30-day incubation periods post-nucleation, the crystals formed in different sections of the gel were carefully extracted and studied with scanning electron microscopy and electron microprobe. Additionally, Raman spectra were collected from the samples using a confocal Raman microscope, providing further insights into their molecular composition and structural properties. The obtained results show that under the induced experimental conditions (i) phosphate incorporates into calcite’s structure, and (ii) the growth of calcium phosphates in the presence of carbonate ions involves the sequential, heterogeneous nucleation of CO₃-bearing OCP/HAP-like phases, with Raman spectral characteristics very similar to those of bioapatites. Full article

(This article belongs to the Collection Topic Collection: Mineralogical Crystallography)

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9 pages, 2998 KB

Open AccessEditor’s ChoiceArticle

Synthesis, Crystal Structure, and Electropolymerization of 1,4-Di([2,2′-bithiophen]-3-yl)buta-1,3-diyne

by Alessandro Pedrini, Chiara Massera, Enrico Dalcanale, Marco Giannetto and Roberta Pinalli

Crystals 2024, 14(7), 620; https://doi.org/10.3390/cryst14070620 - 5 Jul 2024

Viewed by 1607

Abstract

For their great structural versatility, thiophene-based π-conjugated systems have been widely exploited in the preparation of low band gap materials. Here, we report the synthesis of a highly conjugated tetrathiophene system, namely 1,4-di([2,2′-bithiophen]-3-yl)buta-1,3-diyne (1), that presents two bithiophene units connected at [...] Read more.

For their great structural versatility, thiophene-based π-conjugated systems have been widely exploited in the preparation of low band gap materials. Here, we report the synthesis of a highly conjugated tetrathiophene system, namely 1,4-di([2,2′-bithiophen]-3-yl)buta-1,3-diyne (1), that presents two bithiophene units connected at position 3 by a butadiynylene spacer. Single-crystal X-ray diffraction (SC-XRD) analysis elucidated the structure of 1, confirming the planarity of the molecule. The molecule was then electropolymerized onto the surface of a gold-coated piezoelectric quartz crystal, showing a high reactivity that is ascribable to the extended conjugation. The frontier molecular orbital energies of 1 were obtained via DFT optimization performed on the crystal structure-derived molecular geometry. Finally, DFT was also used to estimate the polymer band gap. Full article

(This article belongs to the Special Issue Synthesis, Characterization and Applications of Crystalline Electroconductive Polymers)

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13 pages, 8448 KB

Open AccessEditor’s ChoiceArticle

Effect of Silver Vanadate Nanowires Addition on Structural and Morphological Properties of Dental Porcelain Prepared from Economic Raw Materials

by Badr Eddine Sakhkhane, Marieta Mureșan-Pop, Lucian Barbu-Tudoran, Tamás Lovász and Liliana Bizo

Crystals 2024, 14(7), 616; https://doi.org/10.3390/cryst14070616 - 3 Jul 2024

Cited by 1 | Viewed by 1858

Abstract

In addition to many materials, silver vanadate (AgVO₃) has gained interest due to its antimicrobial properties, which opens up the potential for use as an antibacterial agent for biomedical applications. This work aimed to study the effect of AgVO₃ addition [...] Read more.

In addition to many materials, silver vanadate (AgVO₃) has gained interest due to its antimicrobial properties, which opens up the potential for use as an antibacterial agent for biomedical applications. This work aimed to study the effect of AgVO₃ addition on the structural and morphological properties of a developed dental porcelain (DP) prepared from natural raw materials. AgVO₃ nanowires, prepared by the coprecipitation method, were added in different amounts (1, 3, and 5 wt.%) to a DP mass with the initial composition of 80 wt.% feldspar, 15 wt.% quartz, and 5 wt.% kaolin, obtained by sintering the mixture at 1300 °C. The structural and morphological properties of AgVO₃ and DP were investigated by X-ray powder diffraction (XRPD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS), and transmission electron microscopy (TEM). The results showed the formation of α-AgVO₃ nanowires coated with semispherical metallic silver nanoparticles. Moreover, α-AgVO₃ additions do not influence the structural and morphological properties of DP, with the presence of Ag and V clearly identified in the DP with the α-AgVO₃ addition. Our findings highlight the potential of this novel material for use in various dental applications. Future studies need to establish the antibacterial properties of the prepared dental material. Full article

(This article belongs to the Special Issue Ceramics: Processes, Microstructures, and Properties)

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50 pages, 12170 KB

Open AccessEditor’s ChoiceReview

Advancements in ZnO-Based Photocatalysts for Water Treatment: A Comprehensive Review

by Souad Abou Zeid and Yamin Leprince-Wang

Crystals 2024, 14(7), 611; https://doi.org/10.3390/cryst14070611 - 30 Jun 2024

Cited by 57 | Viewed by 7226

Abstract

Water contamination remains a pressing global concern, necessitating the development of effective and sustainable water treatment solutions. Zinc oxide (ZnO) has garnered significant attention for its potential applications in photocatalysis due to its unique properties and versatile nature. This review synthesizes recent research [...] Read more.

Water contamination remains a pressing global concern, necessitating the development of effective and sustainable water treatment solutions. Zinc oxide (ZnO) has garnered significant attention for its potential applications in photocatalysis due to its unique properties and versatile nature. This review synthesizes recent research findings on the advancement in ZnO-based photocatalysts for water treatment, encompassing synthesis methods, structure modifications for photocatalytic efficiency enhancement, toxicity assessments, and applications in diverse water treatment processes. By critically analyzing the strategies to enhance the photocatalytic performance of ZnO and its role in addressing water pollution challenges, this review provides valuable insights into the evolving landscape of ZnO-based photocatalysts for achieving efficient and environmentally friendly water treatment systems. This review emphasizes the transformative potential of ZnO-based photocatalysts in revolutionizing water treatment methodologies and underscores the importance of continued research and innovation in harnessing ZnO’s capabilities for sustainable water purification. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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12 pages, 4097 KB

Open AccessEditor’s ChoiceArticle

The Effect of Template Reset Operation on the Number of Crystals Precipitated at the Air–Solution Template Interface

by Bolor-Uyanga Tumurbaatar, Shuntaro Amari and Hiroshi Takiyama

Crystals 2024, 14(7), 591; https://doi.org/10.3390/cryst14070591 - 27 Jun 2024

Viewed by 1691

Abstract

The application of template crystallization to developing novel crystalline materials has attracted attention. However, when the air–solution interface becomes the template interface and the target material crystallizes, new nucleation at the template interface is prevented, which is predicted to prevent the increase in [...] Read more.

The application of template crystallization to developing novel crystalline materials has attracted attention. However, when the air–solution interface becomes the template interface and the target material crystallizes, new nucleation at the template interface is prevented, which is predicted to prevent the increase in the total number of crystals. In this study, we investigated the effect of operations that change the driving force at the air–solution template interface on the number of crystals at the interface. The number of crystals precipitated by changing the local supersaturation was investigated by a novel “template reset” operation, in which the concentration driving force near the template interface is changed by dissolving the crystals at the interface, once precipitated. The results showed that the number of crystals increased significantly after the template reset operation, and the particle size distribution was also improved. The temperature of the solution near the interface after the template reset operation was higher than that of the solution at the bottom of the petri dish and the prepared saturated solution, suggesting that the driving force of crystallization was higher. Full article

(This article belongs to the Section Industrial Crystallization)

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25 pages, 4950 KB

Open AccessEditor’s ChoiceArticle

Double-Helical Tiled Chain Structure of the Twist-Bend Liquid Crystal Phase in CB7CB

by Michael R. Tuchband, Min Shuai, Keri A. Graber, Dong Chen, Chenhui Zhu, Leo Radzihovsky, Arthur Klittnick, Lee Foley, Alyssa Scarbrough, Jan H. Porada, Mark Moran, Joseph Yelk, Justin B. Hooper, Xiaoyu Wei, Dmitry Bedrov, Cheng Wang, Eva Korblova, David M. Walba, Alexander Hexemer, Joseph E. Maclennan, Matthew A. Glaser and Noel A. Clark Show full author list Hide full author list

Crystals 2024, 14(7), 583; https://doi.org/10.3390/cryst14070583 - 25 Jun 2024

Cited by 4 | Viewed by 2140

Abstract

The twist-bend nematic liquid crystal phase is a three-dimensional fluid in which achiral bent molecules spontaneously form an orientationally ordered, macroscopically chiral, heliconical winding of a ten nanometer-scale pitch in the absence of positional ordering. Here, the structure of the twist-bend phase of [...] Read more.

The twist-bend nematic liquid crystal phase is a three-dimensional fluid in which achiral bent molecules spontaneously form an orientationally ordered, macroscopically chiral, heliconical winding of a ten nanometer-scale pitch in the absence of positional ordering. Here, the structure of the twist-bend phase of the bent dimer CB7CB and its mixtures with 5CB is characterized, revealing a hidden invariance of the self-assembly of the twist-bend structure of CB7CB, such that over a wide range of concentrations and temperatures, the helix pitch and cone angle change as if the ground state for a pitch of the TB helix is an inextensible heliconical ribbon along the contour formed by following the local molecular long axis (the director). Remarkably, the distance along the length for a single turn of this helix is given by 2πR_mol, where R_mol is the radius of bend curvature of a single all-trans CB7CB molecule. This relationship emerges from frustrated steric packing due to the bent molecular shape: space in the fluid that is hard to fill attracts the most flexible molecular subcomponents, a theme of nanosegregation that generates self-assembled, oligomer-like correlations of interlocking bent molecules in the form of a brickwork-like tiling of pairs of molecular strands into duplex double-helical chains. At higher temperatures in the twist-bend phase, the cone angle is small, the director contour is nearly along the helix axis z, and the duplex chains are sequences of biaxial elements formed by overlapping half-molecule pairs, with an approximately 45° rotation of the biaxis between each such element along the chain. Full article

(This article belongs to the Section Liquid Crystals)

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15 pages, 3621 KB

Open AccessEditor’s ChoiceArticle

Completing the Ba–As Compositional Space: Synthesis and Characterization of Three New Binary Zintl Arsenides, Ba₃As₄, Ba₅As₄, and Ba₁₆As₁₁

by Spencer R. Watts, Lindsey M. Wingate, Svilen Bobev and Sviatoslav Baranets

Crystals 2024, 14(6), 570; https://doi.org/10.3390/cryst14060570 - 20 Jun 2024

Cited by 2 | Viewed by 2235

Abstract

Three novel binary barium arsenides, Ba₃As₄, Ba₅As₄, and Ba₁₆As₁₁, were synthesized and their crystal and electronic structures were investigated. Structural data collected via the single-crystal X-ray diffraction method indicate that the [...] Read more.

Three novel binary barium arsenides, Ba₃As₄, Ba₅As₄, and Ba₁₆As₁₁, were synthesized and their crystal and electronic structures were investigated. Structural data collected via the single-crystal X-ray diffraction method indicate that the anionic substructures of all three novel compounds are composed of structural motifs based on the homoatomic As–As contacts, with [As₂]⁴⁻ dimers found in Ba₅As₄ and Ba₁₆As₁₁, and an [As₄]⁶⁻ tetramer found in Ba₃As₄. Ba₃As₄ and Ba₅As₄ crystallize in the orthorhombic crystal system—with the non-centrosymmetric space group Fdd2 (a = 15.3680(20) Å, b = 18.7550(30) Å, c = 6.2816(10) Å) for the former, and the centrosymmetric space group Cmce (a = 16.8820(30) Å, b = 8.5391(16) Å, and c = 8.6127(16) Å) for the latter—adopting Eu₃As₄ and Eu₅As₄ structure types, respectively. The heavily disordered Ba₁₆As₁₁ structure was solved in the tetragonal crystal system with the space group

P \bar{4} 2_{1} m

(a = 12.8944(12) Å and c = 11.8141(17) Å). The Zintl concept can be applied to each of these materials as follows: Ba₃As₄ = (Ba²⁺)₃[As₄]⁶⁻, Ba₅As₄ = (Ba²⁺)₅(As³⁻)₂[As₂]⁴⁻, and 2 × Ba₁₆As₁₁ = (Ba²⁺)₃₂(As³⁻) ≈ ₂₀[As₂]⁴⁻ ≈ 1, pointing to the charge-balanced nature of these compounds. Electronic structure calculations indicate narrow bandgap semiconducting behavior, with calculated bandgaps of 0.47 eV for Ba₃As₄, 0.34 eV for Ba₅As₄, and 0.33 eV for Ba₁₆As₁₁. Full article

(This article belongs to the Special Issue Research on Thermoelectric Materials: Waste Heat into Renewable Energy)

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21 pages, 11142 KB

Open AccessEditor’s ChoiceReview

Recent Progress of Floating-Zone Techniques for Bulk Single-Crystal Growth

by Naoki Kikugawa

Crystals 2024, 14(6), 552; https://doi.org/10.3390/cryst14060552 - 14 Jun 2024

Cited by 4 | Viewed by 4077

Abstract

This review describes the recent progress of floating-zone techniques for bulk single-crystal growth. The most crucial point of the crucible-free technique is to keep the molten zone stable. It has been investigated and reported to yield a steeper temperature gradient at the liquid–solid [...] Read more.

This review describes the recent progress of floating-zone techniques for bulk single-crystal growth. The most crucial point of the crucible-free technique is to keep the molten zone stable. It has been investigated and reported to yield a steeper temperature gradient at the liquid–solid interface along the growth direction and a homogeneous molten liquid along the rotation axis. This article overviews several recent achievements starting from the conventional setup, particularly for lamps equipped in horizontal or vertical configurations, tilting mirrors, shielding the irradiation, and filament sizes for the optical-lamp floating-zone furnaces. Also, the recently advancing laser-heated floating-zone furnaces are described. Throughout the article, the author emphasizes that the floating-zone technique has been a powerful tool for crystal growth since the 1950s with its roots in the zone-melting method, and it has still been advancing for further materials’ growth such as quantum materials with modern scientific concepts. Full article

(This article belongs to the Special Issue Advances in Crystal Growth: Pioneering Materials for Tomorrow's Technologies)

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17 pages, 7761 KB

Open AccessEditor’s ChoiceArticle

Evaluating the Effect of Hydrogen on the Tensile Properties of Cold-Finished Mild Steel

by Emmanuel Sey and Zoheir N. Farhat

Crystals 2024, 14(6), 529; https://doi.org/10.3390/cryst14060529 - 31 May 2024

Cited by 3 | Viewed by 1737

Abstract

One of the major sources of catastrophic failures and deterioration of the mechanical properties of metals, such as ductility, toughness, and strength, in various engineering components during application is hydrogen embrittlement (HE). It occurs as a result of the adsorption, diffusion, and interaction [...] Read more.

One of the major sources of catastrophic failures and deterioration of the mechanical properties of metals, such as ductility, toughness, and strength, in various engineering components during application is hydrogen embrittlement (HE). It occurs as a result of the adsorption, diffusion, and interaction of hydrogen with various metal defects like dislocations, voids, grain boundaries, and oxide/matrix interfaces due to its small atomic size. Over the years, extensive effort has been dedicated to understanding hydrogen embrittlement sources, effects, and mechanisms. This study aimed at assessing the tensile properties, toughness, ductility, and susceptibility to hydrogen embrittlement of cold-finished mild steel. Steel coupons were subjected to electrochemical hydrogen charging in a carefully chosen alkaline solution over a particular time and at various charging current densities. Tensile property tests were conducted immediately after the charging process, and the results were compared with those of uncharged steel. The findings revealed a clear drop in toughness and ductility with increasing hydrogen content. Fracture surfaces were examined to determine the failure mechanisms. This evaluation has enabled the prediction of steel’s ability to withstand environments with elevated hydrogen concentrations during practical applications. Full article

(This article belongs to the Special Issue Hydrogen Embrittlement of Metals)

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11 pages, 5467 KB

Open AccessEditor’s ChoiceArticle

Tailoring the Magnetic and Hyperthermic Properties of Biphase Iron Oxide Nanocubes through Post-Annealing

by Supun B. Attanayake, Amit Chanda, Raja Das, Manh-Huong Phan and Hariharan Srikanth

Crystals 2024, 14(6), 519; https://doi.org/10.3390/cryst14060519 - 30 May 2024

Cited by 1 | Viewed by 1326

Abstract

Tailoring the magnetic properties of iron oxide nanosystems is essential to expanding their biomedical applications. In this study, 34 nm iron oxide nanocubes with two phases consisting of Fe₃O₄ and α-Fe₂O₃ were annealed for 2 h in [...] Read more.

Tailoring the magnetic properties of iron oxide nanosystems is essential to expanding their biomedical applications. In this study, 34 nm iron oxide nanocubes with two phases consisting of Fe₃O₄ and α-Fe₂O₃ were annealed for 2 h in the presence of O₂, N₂, He, and Ar to tune the respective phase volume fractions and control their magnetic properties. X-ray diffraction and magnetic measurements were carried out post-treatment to evaluate changes in the treated samples compared to the as-prepared samples, showing an enhancement of the α-Fe₂O₃ phase in the samples annealed with O₂ while the others indicated a Fe₃O₄ enhancement. Furthermore, the latter samples indicated enhancements in crystallinity and saturation magnetization, while coercivity enhancements were the most significant in samples annealed with O₂, resulting in the highest specific absorption rates (of up to 1000 W/g) in all the applied fields of 800, 600, and 400 Oe in agar during magnetic hyperthermia measurements. The general enhancement of the specific absorption rate post-annealing underscores the importance of the annealing atmosphere in the enhancement of the magnetic and structural properties of nanostructures. Full article

(This article belongs to the Section Hybrid and Composite Crystalline Materials)

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23 pages, 12447 KB

Open AccessEditor’s ChoiceArticle

Novel Salts of Heterocyclic Polyamines and 5-Sulfosalicylic Acid: Synthesis, Crystal Structure, and Hierarchical Supramolecular Interactions

by Joanna Bojarska, Krzysztof Łyczko and Adam Mieczkowski

Crystals 2024, 14(6), 497; https://doi.org/10.3390/cryst14060497 - 24 May 2024

Cited by 3 | Viewed by 1754

Abstract

A series of novel salts of heterocyclic polyamines with 5-sulfosalicylic acid (C₄H₇N₄⁺)(C₇H₅O₆S⁻)∙2(H₂O) (1), (C₄H₆ClN₄⁺)(C₇H₅ [...] Read more.

A series of novel salts of heterocyclic polyamines with 5-sulfosalicylic acid (C₄H₇N₄⁺)(C₇H₅O₆S⁻)∙2(H₂O) (1), (C₄H₆ClN₄⁺)(C₇H₅O₆S⁻)∙H₂O (2), (C₅H₈N₃⁺)(C₇H₅O₆S⁻)∙H₂O (3), (C₅H₇N₆⁺)(C₇H₅O₆S⁻)∙H₂O (4), (C₆H₁₄N₂²⁺)(C₇H₄O₆S²⁻)∙H₂O (5), and (C₁₄H₁₉N₂⁺)(C₇H₅O₆S⁻) (6) have been successfully synthesized. Their crystal structures have been determined by single-crystal X-ray diffraction. Overall, compounds adopt a layered structure with aminium cations and 5-sulfosalicylic anions linked via water molecules. The solid-state architectures of these compounds are dominated by O(N,H)-H⋯O and N-H⋯N hydrogen bonds and stabilized by weak interconnects. C-Cl⋯π and S-O⋯π interactions, apart from π⋯π and C-H(O)⋯π, were reported. Diverse approaches were used to study the effect of substituents in the polyamines in solid-state arrangement. A Hirshfeld surface analysis, with associated 3D Hirshfeld surface maps and 2D fingerprint plots, molecular electrostatic potential, and energy frameworks were used to comprehensively investigate the nature and hierarchy of non-covalent interactions and inspect supramolecular differences. The contact enrichment ratio calculations provided deeper insight into the propensity of interconnects to influence crystal packing. The evaluation of the effects of H-bonding synthons resulting from different substituents in the polyamines on self-assemblies is also presented. In the context of crystal engineering, a specific intramolecular synthon via O-H⋯O observed in nearly all crystals can be employed in the pseudo-cyclic replacement strategy in the design of new molecules. Full article

(This article belongs to the Special Issue Heterocyclic Organic Compounds: Crystal Structure and Their Properties)

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15 pages, 2466 KB

Open AccessEditor’s ChoiceArticle

Space Group Choice for an Octahedral Zn Complex with Nalidixic Acid and (R,R)-Diaminocyclohexane as Ligands: Get the Stereochemistry Right

by Martin Lutz and Tom W. Müller

Crystals 2024, 14(6), 498; https://doi.org/10.3390/cryst14060498 - 24 May 2024

Cited by 1 | Viewed by 1622

Abstract

With this report, the space group of

[Z n (N a l) {(D A C H)}_{2}] C l

is corrected (

N a l

: nalidixic acid mono-anion;

D A C H

: diaminocyclohexane) from its [...] Read more.

With this report, the space group of

[Z n (N a l) {(D A C H)}_{2}] C l

is corrected (

N a l

: nalidixic acid mono-anion;

D A C H

: diaminocyclohexane) from its wrong description in the literature. In the correct, non-centrosymmetric space group

P 1

, the crystal structure is well ordered and the stereochemistry is correct. Crystallographic tools to recognize the correct symmetry are described. This work encourages experienced and inexperienced scientists to remain critical about the output of automatic, black-box crystallographic software. Full article

(This article belongs to the Section Organic Crystalline Materials)

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13 pages, 752 KB

Open AccessEditor’s ChoiceReview

Machine Learning Methods to Improve Crystallization through the Prediction of Solute–Solvent Interactions

by Aatish Kandaswamy and Sebastian P. Schwaminger

Crystals 2024, 14(6), 501; https://doi.org/10.3390/cryst14060501 - 24 May 2024

Cited by 2 | Viewed by 2745

Abstract

Crystallization plays a crucial role in defining the quality and functionality of products across various industries, including pharmaceutical, food and beverage, and chemical manufacturing. The process’s efficiency and outcome are significantly influenced by solute–solvent interactions, which determine the crystalline product’s purity, size, and [...] Read more.

Crystallization plays a crucial role in defining the quality and functionality of products across various industries, including pharmaceutical, food and beverage, and chemical manufacturing. The process’s efficiency and outcome are significantly influenced by solute–solvent interactions, which determine the crystalline product’s purity, size, and morphology. These attributes, in turn, impact the product’s efficacy, safety, and consumer acceptance. Traditional methods of optimizing crystallization conditions are often empirical, time-consuming, and less adaptable to complex chemical systems. This research addresses these challenges by leveraging machine learning techniques to predict and optimize solute–solvent interactions, thereby enhancing crystallization outcomes. This review provides a novel approach to understanding and controlling crystallization processes by integrating supervised, unsupervised, and reinforcement learning models. Machine learning not only improves product the quality and manufacturing efficiency but also contributes to more sustainable industrial practices by minimizing waste and energy consumption. Full article

(This article belongs to the Section Biomolecular Crystals)

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12 pages, 3858 KB

Open AccessEditor’s ChoiceArticle

Wide Temperature Stability of BaTiO₃-NaNbO₃-Gd₂O₃ Dielectric Ceramics with Grain Core–Shell Structure

by Zicheng Zhao, Yaoning Bai, Mingwei Li and Huiming Ji

Crystals 2024, 14(6), 488; https://doi.org/10.3390/cryst14060488 - 23 May 2024

Cited by 2 | Viewed by 1606

Abstract

As consumer electronics and industrial control systems continue to evolve, the operating temperature range of capacitors is gradually increasing. Barium titanate-based ceramic capacitors are widely used in the field of high dielectrics, so temperature-stable barium titanate-based dielectric materials have been a hot research [...] Read more.

As consumer electronics and industrial control systems continue to evolve, the operating temperature range of capacitors is gradually increasing. Barium titanate-based ceramic capacitors are widely used in the field of high dielectrics, so temperature-stable barium titanate-based dielectric materials have been a hot research topic in the field of dielectric ceramics. The construction of a core–shell structure by unequal doping is an effective way to obtain temperature-stable dielectric materials. At the same time, this structure retains part of the highly dielectric tetragonal phase, and materials with overall high dielectric constants can be obtained. In this work, we prepared BaTiO₃-xNaNbO₃-0.002Gd₂O₃ (x = 1.0–6.0 mol%) as well as BaTiO₃-0.05NaNbO₃-yGd₂O₃ (y = 0–0.30 mol%) dielectric ceramics. On the basis of high-electronic-bandgap NaNbO₃-modified BaTiO₃ dielectric ceramics, a core–shell structure with a larger proportion of core phase was obtained by further doping the amphiphilic rare-earth oxide Gd₂O₃. By designing this core–shell structure, the temperature stability range of capacitors can be expanded. At a doping level of 5.0 mol% NaNbO₃ and 0.20 mol% Gd₂O₃, the room temperature dielectric constant ε_r = 4266 and dielectric loss tan δ = 0.95% conforms to the X8R standard (from −55 °C to 150 °C, TCC < ±15%); volume resistivity ρ_v = 10,200 GΩ·cm and breakdown strength E_b = 13.5 kV/mm is attained in BaTiO₃-based ceramics. The system has excellent dielectric and insulating properties; it provides a new solution for temperature-stable dielectric ceramics. Full article

(This article belongs to the Special Issue Advanced Ferroelectric, Piezoelectric and Dielectric Ceramics)

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19 pages, 3206 KB

Open AccessEditor’s ChoiceArticle

Novel Quaternary Ammonium Aldimine Derivatives Featuring 3,4,5-Trimethoxy Phenyl Fragment: Synthesis, Crystal Structure and Evaluation of Antioxidant and Antibacterial Activity

by Rusi Rusew, Mariya Georgieva, Vanya Kurteva and Boris Shivachev

Crystals 2024, 14(6), 486; https://doi.org/10.3390/cryst14060486 - 22 May 2024

Viewed by 1751

Abstract

This study demonstrates the synthesis of five novel quaternary ammonium aldimines through a two-step synthetic route involving a condensation reaction between 4-pyridincarboxyaldehyde and 3,4,5-trimethoxyaniline, followed by the quaternization of the pyridine N-atom with various aromatic α-bromo ketones. The newly obtained compounds underwent characterization [...] Read more.

This study demonstrates the synthesis of five novel quaternary ammonium aldimines through a two-step synthetic route involving a condensation reaction between 4-pyridincarboxyaldehyde and 3,4,5-trimethoxyaniline, followed by the quaternization of the pyridine N-atom with various aromatic α-bromo ketones. The newly obtained compounds underwent characterization for both purity and molecular structure, utilizing HR-MS, 1D, and 2D NMR spectroscopy in solution, as well as a comparison between single-crystal and powder X-ray analyses in a solid state. The thermal behavior of the studied compounds was evaluated using differential scanning calorimetry (DSC). The antioxidant properties of the compounds were assessed through DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging and ferric-reducing antioxidant power (FRAP) assays, employing Trolox as a standard. The performed in vitro antibacterial screening indicates a selective antibacterial activity against Gram-negative K. pneumoniae and P. aeruginosa, while no such activity is detected for Gram-negative E. coli and Gram-positive S. aureus. Full article

(This article belongs to the Special Issue Protein Crystallography: The State of the Art)

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28 pages, 12894 KB

Open AccessEditor’s ChoiceReview

Crystal Morphology Prediction Models and Regulating Methods

by Yuan Gao, Wenxi Song, Jinyue Yang, Xiongtao Ji, Na Wang, Xin Huang, Ting Wang and Hongxun Hao

Crystals 2024, 14(6), 484; https://doi.org/10.3390/cryst14060484 - 21 May 2024

Cited by 7 | Viewed by 4884

Abstract

Growing high-quality crystals with ideal properties is of great importance. The morphology of crystal is one key factor reflecting product quality, as it can affect the performance of products and downstream operations. In this work, the current state of crystal morphology modification is [...] Read more.

Growing high-quality crystals with ideal properties is of great importance. The morphology of crystal is one key factor reflecting product quality, as it can affect the performance of products and downstream operations. In this work, the current state of crystal morphology modification is reviewed from different perspectives. First, the most widely used crystal growth models are discussed. Then, a variety of crystal morphology control methods, which include adjustment of crystallization operation parameters, addition of foreign molecules, change of different solvents, membrane assistance, the addition of external physical fields and the use of ball milling are summarized. As for applications, the control of crystal morphology has application potential in pharmaceutical and material fields, for example, energetic materials and semiconductor materials. Finally, the future development direction of crystal morphology regulation is discussed. Full article

(This article belongs to the Section Industrial Crystallization)

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14 pages, 1612 KB

Open AccessEditor’s ChoiceReview

B-Factor Rescaling for Protein Crystal Structure Analyses

by Georg Mlynek, Kristina Djinović-Carugo and Oliviero Carugo

Crystals 2024, 14(5), 443; https://doi.org/10.3390/cryst14050443 - 7 May 2024

Cited by 10 | Viewed by 4257

Abstract

The B-factor, also known as the atomic displacement parameter, is a fundamental metric in crystallography for quantifying the positional flexibility of atoms within crystal lattices. In structural biology, various developments have expanded the use of B-factors beyond conventional crystallographic analysis, allowing for a [...] Read more.

The B-factor, also known as the atomic displacement parameter, is a fundamental metric in crystallography for quantifying the positional flexibility of atoms within crystal lattices. In structural biology, various developments have expanded the use of B-factors beyond conventional crystallographic analysis, allowing for a deeper understanding of protein flexibility, enzyme manipulation, and an improved understanding of molecular dynamics. However, the interpretation of B-factors is complicated by their sensitivity to various experimental and computational factors, necessitating rigorous rescaling methods to ensure meaningful comparisons across different structures. This article provides an in-depth description of rescaling approaches used for B-factors. It includes an examination of several methods for managing conformational disorder and selecting the atom types required for the analysis. Full article

(This article belongs to the Section Biomolecular Crystals)

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14 pages, 4456 KB

Open AccessEditor’s ChoiceArticle

The Epitaxial Growth of Ge and GeSn Semiconductor Thin Films on C-Plane Sapphire

by Emmanuel Wangila, Calbi Gunder, Petro M. Lytvyn, Mohammad Zamani-Alavijeh, Fernando Maia de Oliveira, Serhii Kryvyi, Hryhorii Stanchu, Aida Sheibani, Yuriy I. Mazur, Shui-Qing Yu and Gregory Salamo

Crystals 2024, 14(5), 414; https://doi.org/10.3390/cryst14050414 - 28 Apr 2024

Cited by 1 | Viewed by 2590

Abstract

Ge_1−xSn_x growth on a new sapphire platform has been demonstrated. This involved the growth of GeSn on Ge/GaAs layers using the algorithm developed. The resultant growths of Ge on GaAs/AlAs/sapphire and Ge_1−xSn_x on Ge/GaAs/AlAs/sapphire were investigated by [...] Read more.

Ge_1−xSn_x growth on a new sapphire platform has been demonstrated. This involved the growth of GeSn on Ge/GaAs layers using the algorithm developed. The resultant growths of Ge on GaAs/AlAs/sapphire and Ge_1−xSn_x on Ge/GaAs/AlAs/sapphire were investigated by in situ and ex situ characterization techniques to ascertain the surface morphology, crystal structure, and quality. The growth mode of Ge on GaAs was predominantly two-dimensional (2D), which signifies a layer-by-layer deposition, contributing to enhanced crystal quality in the Ge/GaAs system. The growth of Ge_1−xSn_x with 10% Sn on a graded profile for 30 min shows uniform composition and a strong peak on the reciprocal space map (RSM). On the other hand, the partially relaxed growth of the alloy on RSM was established. Full article

(This article belongs to the Special Issue Epitaxial Growth of Semiconductor Materials and Devices)

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13 pages, 834 KB

Open AccessEditor’s ChoiceReview

Possibility of Phase Transformation of Al₂O₃ by a Laser: A Review

by Tadas Matijošius, Juozas Padgurskas and Gedvidas Bikulčius

Crystals 2024, 14(5), 415; https://doi.org/10.3390/cryst14050415 - 28 Apr 2024

Cited by 2 | Viewed by 4539

Abstract

Aluminum (Al) components of high quality often require an optimal ratio of lightness and favorable mechanical properties. In order to improve the physical-mechanical properties of Al, an aluminum oxide (Al₂O₃) film is usually formed on the surface of Al, [...] Read more.

Aluminum (Al) components of high quality often require an optimal ratio of lightness and favorable mechanical properties. In order to improve the physical-mechanical properties of Al, an aluminum oxide (Al₂O₃) film is usually formed on the surface of Al, which itself is characterized by high strength, hardness, corrosion resistance, and other technical properties. Unfortunately, depending on the conditions, the oxide film may be formed from different crystal phases on the Al surface, which are not always of desirable quality, i.e., the α-Al₂O₃ phase. The present review demonstrates that the properties of the Al₂O₃ film may be improved by Al processing with a laser beam according to the scheme: Al (Al alloy) → electrochemical anodizing → treatment with laser irradiation → α-Al₂O₃. Both Al substrate and the anodizing electrolyte affect the phase transformation of anodic Al₂O₃. Laser irradiation of the Al₂O₃ surface leads to high heating and cooling rates, which may promote the formation of a highly crystalline α-Al₂O₃ phase on anodic Al₂O₃. Full article

(This article belongs to the Special Issue Progress in Light Alloys)

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15 pages, 3277 KB

Open AccessEditor’s ChoiceArticle

Influence of MACl on the Crystallization Kinetics of Perovskite via a Two-Step Method

by Chenyue Wang, Bingchen He, Meirong Fu, Zhenhuang Su, Liujiang Zhang, Junhan Zhang, Bingbao Mei and Xingyu Gao

Crystals 2024, 14(5), 399; https://doi.org/10.3390/cryst14050399 - 25 Apr 2024

Cited by 3 | Viewed by 3271

Abstract

The addition of methylammonium chloride (MACl) significantly improves the performance and stability of perovskite fabricated by two-step processes. However, its role in crystallization dynamics has not been thoroughly studied. In this work, a comparison study is carried out using different additions of MACl [...] Read more.

The addition of methylammonium chloride (MACl) significantly improves the performance and stability of perovskite fabricated by two-step processes. However, its role in crystallization dynamics has not been thoroughly studied. In this work, a comparison study is carried out using different additions of MACl to investigate the impact of the perovskite crystallization dynamics. In situ grazing incidence wide-angle X-ray scattering (GIWAXS) observations during the annealing process of perovskite revealed that the amount of MACl significantly influences the crystallinity and orientation of the perovskite. Increasing the MACl addition enhances the crystallinity of the perovskite in the wet film‘s intermediate phase and strengthens the out-of-plane orientation of the FAPbI₃ perovskite α-phase (001) planes during annealing. Moreover, it was found that both excessive and insufficient amounts of MACl introduce defects into the perovskite, which are detrimental to device performance. In contrast, an optimal ratio of MACl-9 mg leads to the formation of uniform and large-grained FAPbI₃ perovskite films, with the longest carrier lifetimes (163.7 ns) compared to MACl-5 mg (68.4 ns) and MACl- 13 mg (120.1 ns). As a result, the fabricated MACl-9 mg-based solar cell achieved the highest efficiency (22.63%), which is higher than those of MACl-5 mg (21.47%) and MACl-13 mg (20.07%). Full article

(This article belongs to the Special Issue Progress and Prospects of Perovskite Films)

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11 pages, 2670 KB

Open AccessEditor’s ChoiceArticle

A Comparison of the Mechanisms and Activation Barriers for Ammonia Synthesis on Metal Nitrides (Ta₃N₅, Mn₆N₅, Fe₃Mo₃N, Co₃Mo₃N)

by Constantinos D. Zeinalipour-Yazdi

Crystals 2024, 14(5), 392; https://doi.org/10.3390/cryst14050392 - 23 Apr 2024

Cited by 5 | Viewed by 2524

Abstract

In this study we perform a comparison of the reaction mechanism and the activation barrier for the rate-determining step in various metal nitrides (Ta₃N₅, Mn₆N₅, Fe₃Mo₃N, Co₃Mo₃N) [...] Read more.

In this study we perform a comparison of the reaction mechanism and the activation barrier for the rate-determining step in various metal nitrides (Ta₃N₅, Mn₆N₅, Fe₃Mo₃N, Co₃Mo₃N) for the ammonia synthesis reaction. The reactions are explained with simplified schematics and the energy profiles for the various reaction mechanisms are given in order to screen the catalytic activity of the catalysts for the ammonia synthesis reaction. We find that the catalytic activity ranks in the following order: Co₃Mo₃N > Fe₃Mo₃N > Ta₃N₅ > Mn₆N_5. We also find that the reaction mechanism proceeds either by a Langmuir–Hinshelwood and an Eley–Rideal/Mars–van Krevelen mechanism. This is an overview of about 10 years of computational research conducted to provide an overview of the progress established in this field of study. Full article

(This article belongs to the Special Issue Catalysts and Modeling of Ammonia Synthesis Catalytic Reactions)

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Graphical abstract

38 pages, 10149 KB

Open AccessEditor’s ChoiceReview

Crystallization of Polymers with a Reduced Density of Entanglements

by Andrzej Pawlak

Crystals 2024, 14(4), 385; https://doi.org/10.3390/cryst14040385 - 20 Apr 2024

Cited by 8 | Viewed by 3554

Abstract

Since methods for reducing macromolecule entanglements have been developed, it has become possible to better understand the impact of polymer chain entanglement on the crystallization process. The article presents basic information about the disentangling of macromolecules and the characterization of the degree of [...] Read more.

Since methods for reducing macromolecule entanglements have been developed, it has become possible to better understand the impact of polymer chain entanglement on the crystallization process. The article presents basic information about the disentangling of macromolecules and the characterization of the degree of entanglement. The basic knowledge of polymer crystallization was also presented. Then, it was discussed how polymers crystallize during their disentangling. Non-isothermal and isothermal crystallization experiments using disentangled polymers, and for comparison using entangled polymers, are described in more detail. The influence of disentangling on both nucleation and crystal growth is highlighted. It is also shown how the crystallization of polymers changes when macromolecules re-entangle. Full article

(This article belongs to the Section Macromolecular Crystals)

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14 pages, 18119 KB

Open AccessEditor’s ChoiceArticle

Novel Tetragonal Boron Pnictides BX (X = N, P, As, Sb, Bi) with Square B2X2 Motifs from Crystal Chemistry and First Principles

by Samir F. Matar and Vladimir L. Solozhenko

Crystals 2024, 14(4), 359; https://doi.org/10.3390/cryst14040359 - 11 Apr 2024

Viewed by 1635

Abstract

Novel tetragonal (P4₂/mnm) boron pnictides BX (X = N, P, As, Sb, Bi) with chromium boride (crb) topology exhibiting a square B2X2 motif with resulting edge- and corner-sharing tetrahedra were predicted from crystal chemistry and [...] Read more.

Novel tetragonal (P4₂/mnm) boron pnictides BX (X = N, P, As, Sb, Bi) with chromium boride (crb) topology exhibiting a square B2X2 motif with resulting edge- and corner-sharing tetrahedra were predicted from crystal chemistry and extensively characterized by density functional theory (DFT) calculations. All new BX phases were found to be cohesive with decreasing cohesive energy along the series. Mechanically stable with positive sets of elastic constants, all crb phases exhibit slightly lower hardness than other BX polymorphs due to increased openness of the crystal structures. All-positive phonon frequencies characterize the crb BX family except for X = Bi, which shows a slight acoustic instability; also, the shape of the phonon spectra changes from band-like for X = N, P, As to flat bands for the heavier elements. The electronic band structures reveal insulating to semiconducting properties for crb BX, depending on the pnictogen nature along the series. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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21 pages, 8810 KB

Open AccessEditor’s ChoiceArticle

Synthesis and Crystal Structures of Two Crystalline Silicic Acids: Hydrated H-Apophyllite, H₁₆Si₁₆O₄₀ • 8–10 H₂O and H-Carletonite, H₃₂Si₆₄O₁₄₄

by Bernd Marler and Isabel Grosskreuz

Crystals 2024, 14(4), 326; https://doi.org/10.3390/cryst14040326 - 30 Mar 2024

Viewed by 1570

Abstract

Hydrated H-Apophyllite (HH-Apo) and H-carletonite (H-Car) were synthesized at 0 °C by leaching an apophyllite and a carletonite single crystal in a large surplus of 1.2 molar hydrochloric acid. The XRD powder patterns of HH-Apo and H-Car were indexed with space group symmetries [...] Read more.

Hydrated H-Apophyllite (HH-Apo) and H-carletonite (H-Car) were synthesized at 0 °C by leaching an apophyllite and a carletonite single crystal in a large surplus of 1.2 molar hydrochloric acid. The XRD powder patterns of HH-Apo and H-Car were indexed with space group symmetries of P4/ncc and I4/mcm and lattice parameters of a = 8.4872(2) Å, c = 16.8684(8) Å and a = 13.8972(3) Å, c = 20.4677(21) Å, respectively. The crystal structures were solved based on model building of the structures of the precursors and a physico-chemical characterization. Rietveld structure refinements confirmed the structure models. HH-Apo and H-Car are among the very few crystalline silicic acids whose structures have been determined and confirmed based on a structure refinement. The structure of HH-Apo contains thin silicate monolayers that can be regarded as constructed by rings of interconnected [SiO₃OH] tetrahedra which form a puckered silicate layer. A sheet of water molecules is intercalated between the silicate layers. There are no direct hydrogen bonds between the silanol groups, but there are hydrogen bonds of different strengths between the terminal O atoms of the silicate layers and the intercalated water molecules. The ¹H MAS NMR spectrum presents a strong signal at 4.9 ppm related to the aforementioned bonds and interactions between the water molecules, as well as a small signal at 22.5 ppm corresponding to an extremely strong hydrogen bond with d(O...O) ≈ 2.2 Å. The structure of H-Car is free of structural water and consists exclusively of microporous silicate double-layers with 4-connected [SiO₄] and 3-connected [SiO₃OH] tetrahedra in a ratio of 1:1 and a thickness of 9.2 Å. Neighboring layers are connected to each other by medium–strong hydrogen bonds with O...O distances of 2.56 Å. The structure of HH-Apo decays within several hours while H-Car is stable. A topotactic condensation reaction applied to H-Car forms an irregularly condensed silicate which still contains the layers in a distorted form as building blocks. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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20 pages, 12081 KB

Open AccessEditor’s ChoiceArticle

Crystal Plasticity Modeling to Capture Microstructural Variations in Cold-Sprayed Materials

by Aulora Williams, YubRaj Paudel, Shiraz Mujahid, Marc Pepi, Peter Czech, Haitham El Kadiri and Hongjoo Rhee

Crystals 2024, 14(4), 329; https://doi.org/10.3390/cryst14040329 - 30 Mar 2024

Cited by 1 | Viewed by 1762

Abstract

The high-velocity impact of powder particles in cold-spray additively manufactured (CSAM) parts creates intersplat boundaries with regions of high dislocation densities and sub-grain structures. Upon microstructure and mechanical characterization, CSAM Aluminum 6061 showed non-uniformity with spatial variation in the microstructure and mechanical properties, [...] Read more.

The high-velocity impact of powder particles in cold-spray additively manufactured (CSAM) parts creates intersplat boundaries with regions of high dislocation densities and sub-grain structures. Upon microstructure and mechanical characterization, CSAM Aluminum 6061 showed non-uniformity with spatial variation in the microstructure and mechanical properties, affecting the overall response of the additively manufactured parts. Post-processing treatments are conducted in as-printed samples to improve particle bonding, relieve residual stresses, and improve mechanical properties. In this work, we attempt to implement the effects of grain size and distribution of smaller grains along the intersplat boundaries using the grain size distribution function and powder size information to accurately predict the deformation response of cold-sprayed material using a mean-field viscoplastic self-consistent (VPSC) model. The incorporation of an intersplat boundary term in the VPSC model resulted in a stress–strain response closely matching the experimental findings, preventing the superficially high stresses observed due to Hall–Petch effects from ultra-fine-grain structures. Likewise, the results from the grain analysis showed the combined effects of grain size, orientation, and intersplat mechanisms that captured the stresses experienced and strain accommodated by individual grains. Full article

(This article belongs to the Special Issue Processing-Microstructure-Properties Relationship of Advanced Alloys)

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15 pages, 11726 KB

Open AccessEditor’s ChoiceArticle

Two New Energetic Hexagonal Anti-Perovskites (N₂H₅)₃X[B₁₂H₁₂] · H₂O (X⁻ = [NO₃]⁻ and [ClO₄]⁻): Crystal Structure, Vibrational Spectra, and Thermal Decomposition

by Rouzbeh Aghaei Hakkak, Thomas M. Klapötke and Thomas Schleid

Crystals 2024, 14(4), 310; https://doi.org/10.3390/cryst14040310 - 27 Mar 2024

Cited by 1 | Viewed by 1754

Abstract

Two novel energetic anti-perovskite compounds with the chemical formula (N₂H₅)₃X[B₁₂H₁₂] · H₂O, where X⁻ is either [NO₃]⁻ or [ClO₄]⁻, were successfully [...] Read more.

Two novel energetic anti-perovskite compounds with the chemical formula (N₂H₅)₃X[B₁₂H₁₂] · H₂O, where X⁻ is either [NO₃]⁻ or [ClO₄]⁻, were successfully synthesized. Both dodecahydro-closo-dodecaborates crystallize orthorhombically in the space group Cmc2₁, exhibiting relatively similar lattice parameters ((N₂H₅)₃[NO₃][B₁₂H₁₂] · H₂O: a = 915.94(5), b = 1817.45(9), c = 952.67(5) pm, (N₂H₅)₃[ClO₄][B₁₂H₁₂] · H₂O: a = 1040.51(6), b = 1757.68(9), c = 942.34(5) pm both for Z = 4). Their synthesis involved a two-step process: first, Cs₂[B₁₂H₁₂] passed through a cation exchange column to yield the acidic form of the dodecahydro-closo-dodecaborate, (H₃O)₂[B₁₂H₁₂]. This aqueous solution was subsequently neutralized with hydrazinium hydroxide and mixed with the corresponding water-dissolved hydrazinium salt (nitrate or perchlorate). Characterization of the obtained crystals was performed by single-crystal X-ray diffraction and Raman spectroscopy as well as thermal analyses (TG-DTA and DSC). The crystal structure determinations revealed that both compounds adopt a hexagonal anti-perovskite structure, distorted by the presence of water molecules. These compounds containing oxidizing oxoanions demonstrate a remarkable ability to release large amounts of energy (almost 2100 J/g) upon thermal decomposition. Full article

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

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10 pages, 4921 KB

Open AccessEditor’s ChoiceArticle

The Effect of Sputtering Target Density on the Crystal and Electronic Structure of Epitaxial BaTiO₃ Thin Films

by Fugang Qi, Shaoqin Peng, Jiachang Bi, Shunda Zhang, Guanhua Su, Peiyi Li, Jiahui Zhang, Tengteng Zhang, Weisong Zhou, Ruyi Zhang and Yanwei Cao

Crystals 2024, 14(4), 304; https://doi.org/10.3390/cryst14040304 - 26 Mar 2024

Cited by 2 | Viewed by 2497

Abstract

Barium titanate (BaTiO₃) is a promising material for silicon-integrated photonics due to its large electro-optical coefficients, low loss, high refractive index, and fast response speed. Several deposition methods have been employed to synthesize BaTiO₃ films. Magnetron sputtering is one of [...] Read more.

Barium titanate (BaTiO₃) is a promising material for silicon-integrated photonics due to its large electro-optical coefficients, low loss, high refractive index, and fast response speed. Several deposition methods have been employed to synthesize BaTiO₃ films. Magnetron sputtering is one of these methods, which offers specific advantages for growing large-scale films. However, there is a scarcity of studies investigating the effect of sputtering target density on the quality of BaTiO₃ films. Therefore, this study aims to uncover the effect of sputtering targets on the crystal and electronic structures of epitaxial BaTiO₃ thin films. Two BaTiO₃ ceramic targets were sintered at different densities by altering the sintering temperatures. The crystal structure and chemical composition of the targets were then characterized using X-ray diffraction, Raman spectroscopy, and scanning electron microscopy with energy-dispersive X-ray spectroscopy. Subsequently, BaTiO₃ epitaxial films were grown by magnetron sputtering using these two targets. The crystal and electronic structures of the BaTiO₃ films were analyzed using high-resolution X-ray diffraction, X-ray photoemission spectroscopy, atomic force microscopy, and spectroscopic ellipsometry. Notably, the BaTiO₃ films grown with high-density targets show superior quality but contain oxygen vacancies, whereas those films synthesized with low-density targets display high surface roughness. These findings provide insights into the effect of sputtering target density on the crystal and electronic structures of epitaxial BaTiO₃ thin films. Full article

(This article belongs to the Special Issue Epitaxial Growth and Application of Metallic Oxide Thin Films)

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26 pages, 3846 KB

Open AccessEditor’s ChoiceReview

Nanostructured Materials for Enhanced Performance of Solid Oxide Fuel Cells: A Comprehensive Review

by Hicham Helal, Mohammadi Ahrouch, Abdelaziz Rabehi, Dario Zappa and Elisabetta Comini

Crystals 2024, 14(4), 306; https://doi.org/10.3390/cryst14040306 - 26 Mar 2024

Cited by 17 | Viewed by 3674

Abstract

Solid oxide fuel cells (SOFCs) have emerged as promising candidates for efficient and environmentally friendly energy conversion technologies. Their high energy conversion efficiency and fuel flexibility make them particularly attractive for various applications, ranging from stationary power generation to portable electronic devices. Recently, [...] Read more.

Solid oxide fuel cells (SOFCs) have emerged as promising candidates for efficient and environmentally friendly energy conversion technologies. Their high energy conversion efficiency and fuel flexibility make them particularly attractive for various applications, ranging from stationary power generation to portable electronic devices. Recently, research has focused on utilizing nanostructured materials to enhance the performance of SOFCs. This comprehensive review summarizes the latest advancements in the design, fabrication, and characterization of nanostructured materials integrated in SOFC. The review begins by elucidating the fundamental principles underlying SOFC operation, emphasizing the critical role of electrode materials, electrolytes, and interfacial interactions in overall cell performance, and the importance of nanostructured materials in addressing key challenges. It provides an in-depth analysis of various types of nanostructures, highlighting their roles in improving the electrochemical performance, stability, and durability of SOFCs. Furthermore, this review delves into the fabrication techniques that enable precise control over nanostructure morphology, composition, and architecture. The influence of nanoscale effects on ionic and electronic transport within the electrolyte and electrodes is thoroughly explored, shedding light on the mechanisms behind enhanced performance. By providing a comprehensive overview of the current state of research on nanostructured materials for SOFCs, this review aims to guide researchers, engineers, and policymakers toward the development of high-performance, cost-effective, and sustainable energy conversion systems. Full article

(This article belongs to the Special Issue Advances of Solid Oxide Fuel Cells)

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