Crystals

13 pages, 3314 KiB

Open AccessArticle

Preparation of N, Cl Co-Doped Lignin Carbon Quantum Dots and Detection of Microplastics in Water

by Hao Zhao, Zishuai Jiang, Chengyu Wang and Yudong Li

Crystals 2023, 13(6), 983; https://doi.org/10.3390/cryst13060983 - 20 Jun 2023

Cited by 2 | Viewed by 1638

The research on rapid and efficient detection of microplastics in water is still in its early stages. Fluorescence feature recognition represents an important and innovative approach to microplastic detection. While carbon quantum dots have been widely used in various environmental detection methods, their [...] Read more.

The research on rapid and efficient detection of microplastics in water is still in its early stages. Fluorescence feature recognition represents an important and innovative approach to microplastic detection. While carbon quantum dots have been widely used in various environmental detection methods, their use for detecting microplastics in water environments has been rarely reported. In this study, N and Cl co-doped carbon quantum dots were synthesized via a hydrothermal method. The heteroatom doping process endowed them with blue luminescence properties, and their adsorption for microplastics was improved through the introduction of positive and negative charges and intermolecular forces. By utilizing a combined mechanism of fluorescence and Rayleigh scattering, the detection of polystyrene microplastics with three different particle sizes was achieved. In the detection process, it exhibits excellent light stability. Notably, the nano-polystyrene exhibited a good nonlinear relationship within the range of 0.01 g/L to 0.001 g/L, with R² values of 0.923 and 0.980 and a detection limit of 0.4 mg/L. These findings provide a novel approach for the detection of nano microplastics. Full article

(This article belongs to the Special Issue Emerging Low-Dimensional Materials II)

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19 pages, 5560 KiB

Open AccessArticle

Experimental Study of the Evolution of Creep-Resistant Steel’s High-Temperature Oxidation Behavior

by Gabriela Baranová, Mária Hagarová, Miloš Matvija, Dávid Csík, Vladimír Girman, Jozef Bednarčík and Pavel Bekeč

Crystals 2023, 13(6), 982; https://doi.org/10.3390/cryst13060982 - 20 Jun 2023

Viewed by 919

Abstract

This study shows that in an atmosphere containing water vapor, the oxide layer on the surface of the 9CrNB steel MarBN (Martensitic 9Cr steel strengthened by Boron and MX Nitrides) was formed by an outer layer of hematite Fe₂O₃ and [...] Read more.

This study shows that in an atmosphere containing water vapor, the oxide layer on the surface of the 9CrNB steel MarBN (Martensitic 9Cr steel strengthened by Boron and MX Nitrides) was formed by an outer layer of hematite Fe₂O₃ and Cr₂O₃ and an inner two-phase layer of Fe₃O₄ and Fe₃O₄ + (Fe, Cr)₂O₄, which was confirmed by XRD analysis. Part of the layer consisted of nodules and pores that were formed during the increase in oxides when the present H₂O(g) acted on the steel surface. The diffusion mechanism at temperatures of 600 and 650 °C and at longer oxidation times supported the “healing process” with a growing layer of Fe oxides and the presence of Cr and minor alloying elements. The effects of alloying elements were quantified using a concentration profile of the oxide layer based on quantitative SEM analysis, as well as an explanation of the mechanism influencing the structure and chemical composition of the oxide layer and the steel-matrix–oxide interface. In addition to Cr, for which the content reached the requirement of exceeding 7.0 wt. % in the inner oxide layer, W, Co, Mn, and Si were also found in increased concentrations, whether in the form of the present Fe-Cr spinel oxide or as part of a continuously distributed layer of Mn₂O₃ and SiO₂ oxides at the steel-matrix–oxide interface. After long-term high-temperature oxidation, coarser carbides of the M₂₃C₆ type (M = Fe,W) significantly depleted in Cr were formed at the oxide-layer/matrix interface. In the zone under the oxide layer, very fine particles of MC (M = V, Nb, and to a lesser extent also Cr in the particle lattice of the given phase) were observed, with a higher number of particles per unit area compared to the state before oxidation. This fact was a consequence of Cr diffusion to the steel surface through the subsurface zone. Full article

(This article belongs to the Special Issue Hot Corrosion and Oxidation of Alloys)

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8 pages, 2911 KiB

Open AccessCommunication

First-Principle Study of Two-Dimensional SiP₂ for Photocatalytic Water Splitting with Ultrahigh Carrier Mobility

by Jianping Li, Hao Pan, Haiyang Sun, Ruxin Zheng and Kai Ren

Crystals 2023, 13(6), 981; https://doi.org/10.3390/cryst13060981 - 20 Jun 2023

Cited by 2 | Viewed by 1198

Abstract

Two-dimensional materials present abundant novel properties when used in advanced applications, which develops considerable focus. In this investigation, the first-principles calculations are explored to study the structural characteristic of the monolayered SiP₂, which is stable even at 1200 K. The SiP [...] Read more.

Two-dimensional materials present abundant novel properties when used in advanced applications, which develops considerable focus. In this investigation, the first-principles calculations are explored to study the structural characteristic of the monolayered SiP₂, which is stable even at 1200 K. The SiP₂ monolayer is a semiconductor with an indirect bandgap of 2.277 eV. The decent band alignment and light absorption capacity imply that the application is a suitable photocatalyst for water splitting. Furthermore, the SiP₂ monolayer possesses an ultrafast electron mobility at 33,153 cm²·V⁻¹·s⁻¹ in the transport direction. The excellent Gibbs free energy of the SiP₂ monolayer is also addressed in an examination of the hydrogen evolution reaction. Full article

(This article belongs to the Special Issue Semiconductor Photocatalysts)

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19 pages, 5872 KiB

Open AccessArticle

Crystal Structure Analysis and Characterization of NADP-Dependent Glutamate Dehydrogenase with Alcohols Activity from Geotrichum candidum

by Jing Zhu, Hai Hou, Kun Li, Xiaoguang Xu, Chunmei Jiang, Dongyan Shao, Junling Shi and Dachuan Yin

Crystals 2023, 13(6), 980; https://doi.org/10.3390/cryst13060980 - 20 Jun 2023

Viewed by 919

Abstract

To better understand its mechanism of activity towards higher alcohols, we overexpressed and purified new Geotrichum candidum GDH (GcGDH). The purified GcGDH (50.27 kDa) was then crystallized, and the crystal diffracted to a resolution of 2.3 Å using X-ray diffraction. [...] Read more.

To better understand its mechanism of activity towards higher alcohols, we overexpressed and purified new Geotrichum candidum GDH (GcGDH). The purified GcGDH (50.27 kDa) was then crystallized, and the crystal diffracted to a resolution of 2.3 Å using X-ray diffraction. We found that the GcGDH crystal structure belonged to space group P212121 and was comprised of two hexamers organized into an asymmetric unit, with each subunit consisting of 452 amino acid residues. The binding sites between higher alcohols or L-glutamic acid and GcGDH were consistent. The optimal reaction conditions for GcGDH and hexanol were a pH of 4.0 and temperature of 30 °C, and those for GcGDH and monosodium glutamate (MSG) were a pH of 8.0 and temperature of 20 °C. The Km values for hexanol and MSG were found to be 74.78 mM and 0.018 mM, respectively. Mutating GcGDH Lys 113 to either Ala or Gly caused a dramatic reduction in its catalytic efficiency towards both MSG and hexanol, suggesting that Lys 113 is essential to the active site of GcGDH. Full article

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17 pages, 6024 KiB

Open AccessArticle

Temperature Induced Monoclinic to Orthorhombic Phase Transition in Protonated ZSM-5 Zeolites with Different Si/Al Ratios: An In-Situ Synchrotron X-ray Powder Diffraction Study

by Nicola Precisvalle, Maura Mancinelli, Matteo Ardit, Giada Beltrami, Lara Gigli, Alfredo Aloise, Enrico Catizzone, Massimo Migliori, Girolamo Giordano, Vincenzo Guidi and Annalisa Martucci

Crystals 2023, 13(6), 979; https://doi.org/10.3390/cryst13060979 - 20 Jun 2023

Viewed by 1145

Abstract

ZSM-5 zeolite is the synthetic counterpart to mutinaite. After thermal activation of the as-synthesized form, the symmetry of the ZSM-5 zeolite is lowered to the monoclinic P2₁/n. ZSM-5 then undergoes a polymorphic displacive phase transition from the monoclinic [...] Read more.

ZSM-5 zeolite is the synthetic counterpart to mutinaite. After thermal activation of the as-synthesized form, the symmetry of the ZSM-5 zeolite is lowered to the monoclinic P2₁/n. ZSM-5 then undergoes a polymorphic displacive phase transition from the monoclinic P2₁/n to the orthorhombic Pnma, Pn2₁a or P2₁2₁2₁ space groups, which occurs upon heating. This phase transition can be influenced by factors such as the type and amount of sorbate molecules present in the zeolite channels. ZSM-5 has many applications, including as a catalyst or sorbent in various industries, where high thermal stability is required. In this study, four ZSM-5 zeolites with different Si/Al ratios were investigated by synchrotron X-ray powder diffraction at both room temperature and high temperature conditions to determine the effects of chemical composition on the structural response of the zeolite lattice. The results showed that the ZSM-5 zeolites retained their crystallinity and structural features throughout the thermal treatment, indicating that they could be used as effective acid catalysts. Distortions in the zeolite framework can occur after TPA+ decomposition and thermal activation, affecting thermal regeneration and efficiency. The charge balance in ZSM-5 is achieved by the formation of Brønsted acid sites, and variations in bonding geometries are influenced by the initial Si/Al ratio. Full article

(This article belongs to the Special Issue Young Crystallographers Across Europe)

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12 pages, 4574 KiB

Open AccessArticle

An Experimental Investigation of the Solid State Sintering of Cemented Carbides Aiming for Mechanical Constitutive Modelling

by Louise Rosenblad, Hjalmar Staf, Henrik Larsson and Per-Lennart Larsson

Crystals 2023, 13(6), 978; https://doi.org/10.3390/cryst13060978 - 20 Jun 2023

Viewed by 887

Abstract

The densification of cemented carbides during sintering was studied using an existing constitutive model based on powder particle size and material composition. In the present analysis, we study how well the constitutive model can capture the experimental results of a dilatometer test. Three [...] Read more.

The densification of cemented carbides during sintering was studied using an existing constitutive model based on powder particle size and material composition. In the present analysis, we study how well the constitutive model can capture the experimental results of a dilatometer test. Three experiments were performed, where the only difference was the transition between the debinding and sintering process. From magnetic measurements, it is concluded that the carbon level in the specimen is affected by changes to the experimental setup. It is shown, using parameter adjustments, that the constitutive model is more suited for a certain experimental setup and carbon level, which is a limitation of the model. In order to capture the mechanical behaviour under different experimental conditions, further constitutive modelling relevant to the carbon level is recommended. Full article

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

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11 pages, 35785 KiB

Open AccessArticle

A Comparative Study on Gemological Characteristics and Color Formation Mechanism of Moqi Agate, Inner Mongolia Province, China

by Sixue Zhang, Li Cui, Qingfeng Guo, Niu Li, Yang Liu, Yinghua Rao and Libing Liao

Crystals 2023, 13(6), 977; https://doi.org/10.3390/cryst13060977 - 20 Jun 2023

Viewed by 1072

Abstract

Agate attracts the attention of gem mineralogists because of its variable colors. The color of agate is closely related to its naming and classification, so it is necessary to study the color and mineral origin of agate. In this paper, the mineralogical characteristics [...] Read more.

Agate attracts the attention of gem mineralogists because of its variable colors. The color of agate is closely related to its naming and classification, so it is necessary to study the color and mineral origin of agate. In this paper, the mineralogical characteristics and color origin of red, yellow and green Moqi agates from Inner Mongolia were systematically studied by means of Fourier transform infrared spectrometer, Raman spectrometer, X-ray powder diffractometer, electron probe microanalyzer and ultraviolet–visible spectrophotometer. It is found that the color of Moqi agate is related to the minerals and trace elements contained in it, and is associated with the electron transition or charge transfer of Fe ions in the contained minerals. Green agate has the highest Fe content, and its color is caused by celadonite inclusions. The red and yellow color in Moqi agate is mainly caused by hematite and goethite, while red agate contains more Fe than yellow agate. Raman spectroscopy and X-ray diffraction analysis show that the content of moganite in Moqi agate is 0–30%. It is calculated that the crystallinity of Moqi agate is 1.5–3.5. This work provides a theoretical basis for future research on the identification of Moqi agate. Full article

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

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9 pages, 2315 KiB

Open AccessReview

Recent Advances in Polydopamine for Surface Modification and Enhancement of Energetic Materials: A Mini-Review

by Ziquan Qin, Dapeng Li, Yapeng Ou, Sijia Du, Qingjie Jiao, Jiwu Peng and Ping Liu

Crystals 2023, 13(6), 976; https://doi.org/10.3390/cryst13060976 - 19 Jun 2023

Cited by 1 | Viewed by 2162

Abstract

Polydopamine (PDA), inspired by the adhesive mussel foot proteins, is widely applied in chemical, biological, medical, and material science due to its unique surface coating capability and abundant active sites. Energetic materials (EMs) play an essential role in both military and civilian fields [...] Read more.

Polydopamine (PDA), inspired by the adhesive mussel foot proteins, is widely applied in chemical, biological, medical, and material science due to its unique surface coating capability and abundant active sites. Energetic materials (EMs) play an essential role in both military and civilian fields as a chemical energy source. Recently, PDA was introduced into EMs for the modification of crystal phase stability and the interfacial bonding effect, and, as a result, to enhance the mechanical, thermal, and safety performances. This mini-review summarizes the representative works in PDA modified EMs from three perspectives. Before that, the self-polymerization mechanisms of dopamine and the methods accelerating this process are briefly presented for consideration of researchers in this field. The future directions and remaining issues of PDA in this field are also discussed at last in this mini-review. Full article

(This article belongs to the Special Issue Co-Crystals and Polymorphic Transition in Energetic Materials)

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14 pages, 5163 KiB

Open AccessArticle

Developing CeO₂-CoAl₂O₄ Semiconductor Ionic Based Heterostructure Composite Electrolyte for Low-Temperature Solid Oxide Fuel Cells (SOFCs)

by Yiwang Dong, Muhammad Yousaf, Muhammad Ali Kamran Yousaf Shah, Muhammad Akbar, Yuzheng Lu, Lei Zhang, Qadeer Akbar Sial, Peng Cao and Changhong Deng

Crystals 2023, 13(6), 975; https://doi.org/10.3390/cryst13060975 - 19 Jun 2023

Viewed by 1059

Abstract

Semiconductor ionic electrolytes, especially heterostructure composites, have a significant role in enhancing oxide ion conductivity and peak power density (PPD) because of their interfacial contact. In this work, the fluorite structure CeO₂ and spinel-based CoAl₂O₄ samples, as a heterostructure [...] Read more.

Semiconductor ionic electrolytes, especially heterostructure composites, have a significant role in enhancing oxide ion conductivity and peak power density (PPD) because of their interfacial contact. In this work, the fluorite structure CeO₂ and spinel-based CoAl₂O₄ samples, as a heterostructure composite electrolyte, are successfully fabricated. The p-type CoAl₂O₄ and n-type CeO₂ heterostructure (CeO₂-CoAl₂O₄) used as an electrolyte exhibits a cell performance of 758 mW/cm² under fuel cell H₂/air conditions at 550 °C, which is quite higher than the pure CoAl₂O₄ and CeO₂ fuel cell devices. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) verified the heterostructure formation including the morphological analysis of the prepared heterostructure composite. The heterostructure-based CeO₂-CoAl₂O₄ composite achieved a higher ionic conductivity of 0.13 S/cm at 550 °C temperature, which means that the constructed device successfully works as an electrolyte by suppressing electronic conductivity. Meanwhile, the obtained results demonstrate the semiconductor ionic heterostructure effect by adjusting the appropriate composition to build heterostructure of the n-type (CeO₂) and p-type (CoAl₂O₄) components and built-in electric field. So, this work exhibits that the constructed device can be effective for energy conversion and storage devices. Full article

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16 pages, 5607 KiB

Open AccessArticle

Two Conformational Polymorphs of a Bioactive Pyrazolo[3,4-d]pyrimidine

by Sang Loon Tan, Yee Seng Tan, Jia Hui Ng, Anton V. Dolzhenko and Edward R. T. Tiekink

Crystals 2023, 13(6), 974; https://doi.org/10.3390/cryst13060974 - 19 Jun 2023

Viewed by 917

Abstract

Two monoclinic (P2₁/c; Z′ = 1) polymorphs, α (from methanol) and β (from ethanol, n-propanol and iso-propanol), of a bioactive pyrazolo[3,4-d]pyrimidine derivative have been isolated and characterised by X-ray crystallography as well as by [...] Read more.

Two monoclinic (P2₁/c; Z′ = 1) polymorphs, α (from methanol) and β (from ethanol, n-propanol and iso-propanol), of a bioactive pyrazolo[3,4-d]pyrimidine derivative have been isolated and characterised by X-ray crystallography as well as by a range of computational chemistry techniques. The different conformations observed for the molecules in the crystals are due to the dictates of molecular packing as revealed by geometry-optimisation calculations. The crucial difference in the molecular packing pertains to the formation of phenylamino-N–H···N(pyrazolyl) hydrogen bonding within supramolecular chains with either helical (α-form; 2₁-screw symmetry) or zigzag (β-form; glide symmetry). As a consequence, the molecular packing is quite distinct in the polymorphs. Lattice energy calculations indicate the β-form is more stable by 11 kJ/mol than the α-form. Full article

(This article belongs to the Special Issue Crystalline Materials: Polymorphism)

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14 pages, 5959 KiB

Open AccessReview

Atomic-Scale Imaging of Organic-Inorganic Hybrid Perovskite Using Transmission Electron Microscope

by Lixia Bao, Peifeng Gao, Tinglu Song, Fan Xu, Zikun Li and Gu Xu

Crystals 2023, 13(6), 973; https://doi.org/10.3390/cryst13060973 - 19 Jun 2023

Viewed by 1167

Abstract

Transmission electron microscope (TEM) is thought as one powerful tool to imaging the atomic-level structure of organic inorganic hybrid perovskite (OIHP) materials, which provides valuable and essential guidance toward high performance OIHP-related devices. However, these OIHPs exhibit poor electron beam stability, severely limiting [...] Read more.

Transmission electron microscope (TEM) is thought as one powerful tool to imaging the atomic-level structure of organic inorganic hybrid perovskite (OIHP) materials, which provides valuable and essential guidance toward high performance OIHP-related devices. However, these OIHPs exhibit poor electron beam stability, severely limiting their practical applications in TEM. Here in this article, the application of TEM to obtain atomic-scale image of OIHPs, main obstacles in identifying the degradation product and future prospects of TEM in the characterization of OIHP materials are reviewed and presented. Three potential strategies (sample protection, low temperature technology, and low-dose technologies) are also proposed to overcome the current drawback of TEM technology. Full article

(This article belongs to the Special Issue Recent Achievements and Progress in Perovskite Photovoltaics)

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21 pages, 2740 KiB

Open AccessArticle

A Dual-Core Surface Plasmon Resonance-Based Photonic Crystal Fiber Sensor for Simultaneously Measuring the Refractive Index and Temperature

by Wangyoyo Li, Yu Chen, Jianjie Xu, Menglin Jiang and Hui Zou

Crystals 2023, 13(6), 972; https://doi.org/10.3390/cryst13060972 - 19 Jun 2023

Cited by 1 | Viewed by 984

Abstract

In this correspondence, a new photonic crystal fiber biosensor structure on the basis of surface plasmon resonance is proposed for the measurement of the refractive index (RI) and TSM temperature simultaneously. In this design, the central and external surface of the biosensor structure [...] Read more.

In this correspondence, a new photonic crystal fiber biosensor structure on the basis of surface plasmon resonance is proposed for the measurement of the refractive index (RI) and TSM temperature simultaneously. In this design, the central and external surface of the biosensor structure are coated with thin gold film. A hole adjacent to the inner gold film is filled with temperature-sensitive material (TSM). With the implementation of internal and external gold coatings along with TSM, the biosensor achieves the measurement of the RI and temperature with two disjoint wavelength coverage. Numerical simulations and calculation results illustrate that the average wavelength sensitivity of the biosensor structure, respectively, achieves 7080 nm/RIU and 3.36 nm/°C with RI coverage from 1.36 to 1.41 and temperature coverage from 0 to 60 °C. Moreover, benefiting from realization of different wavelength regions in RI and temperature sensing, it is believed that the proposed biosensor structure for the measurement of the RI and temperature will have range applications in the fields of medical diagnostics and environmental assessments. Full article

(This article belongs to the Special Issue Recent Advances in Photonic Crystal and Optical Devices)

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8 pages, 2009 KiB

Open AccessArticle

Frustrated Magnetism and Ferroelectricity in a Dy³⁺-Based Triangular Lattice

by Xianghan Xu, Choongjae Won and Sang-Wook Cheong

Crystals 2023, 13(6), 971; https://doi.org/10.3390/cryst13060971 - 19 Jun 2023

Viewed by 1178

Abstract

Triangular lattice magnets have attracted extensive research interest because they are potential hosts for geometrically frustrated magnetism and strong quantum fluctuations. Here, utilizing a laser floating zone technique, we report the first-time successful growth of a DyInO₃ sizable crystal, which contains Dy [...] Read more.

Triangular lattice magnets have attracted extensive research interest because they are potential hosts for geometrically frustrated magnetism and strong quantum fluctuations. Here, utilizing a laser floating zone technique, we report the first-time successful growth of a DyInO₃ sizable crystal, which contains Dy³⁺-based triangular layers. The fine-tuning of Indium stoichiometry was found to be the key factor in the stabilization of the desired hexagonal phase. The X-ray diffraction study of the crystal structure reveals a non-centrosymmetric P6₃mc space group. Switchable polarization, i.e., ferroelectricity, and ferroelectric domain configuration are experimentally demonstrated at room temperature. Anisotropic magnetic and thermodynamic measurements unveil antiferromagnetic interactions, the absence of long-range ordering down to 0.1 K, and a possible doublet ground state, indicating a strongly frustrated magnetism. Our findings suggest that the DyInO₃ crystal is an excellent platform for studying emergent phenomena and their interplay with coherent topological defects in the quantum realm. Full article

(This article belongs to the Special Issue Ferroelectric Materials)

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10 pages, 3163 KiB

Open AccessArticle

Study on Growth Interface of Large Nd:YAG Crystals

by Jiliang Quan, Guanzhen Ke, Yali Zhang, Jian Liu and Jinqiang Huang

Crystals 2023, 13(6), 970; https://doi.org/10.3390/cryst13060970 - 19 Jun 2023

Cited by 1 | Viewed by 1072

Abstract

A study was performed on the growth interface of a large-diameter 1 at% neodymium-doped yttrium aluminum garnet (Nd:YAG) single crystal grown using the Czochralski method. Red parallel light and an orthogonal polarizing system were used to observe the distribution of the central and [...] Read more.

A study was performed on the growth interface of a large-diameter 1 at% neodymium-doped yttrium aluminum garnet (Nd:YAG) single crystal grown using the Czochralski method. Red parallel light and an orthogonal polarizing system were used to observe the distribution of the central and lateral cores of the crystal at different growth interfaces. The solid–liquid interface of large-diameter Nd:YAG crystal growth was mainly determined via the interaction between natural and forced convection. The shape of the solid–liquid interface was mainly controlled via maintaining the crystal rotation rate and the temperature field. Interface inversion generally occurred during the shoulder-expanding stage and late stages of the growth of the cylindrical portion of the crystal. The occurrence of interface inversion is directly related to the temperature field, process parameters, and diameter of the crystal. The growth shape of the crystal interface determined the size and distribution of the central and lateral cores of the crystal. The area of the central and lateral cores was reduced via adjusting the temperature gradient of the solid–liquid interface and crystal rotation speed. Full article

(This article belongs to the Special Issue Emerging Rare-Earth Doped Materials)

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21 pages, 14446 KiB

Open AccessArticle

Simulation of the Cyclic Stress–Strain Behavior of the Magnesium Alloy AZ31B-F under Multiaxial Loading

by Vitor Anes, Rogério Moreira, Luís Reis and Manuel Freitas

Crystals 2023, 13(6), 969; https://doi.org/10.3390/cryst13060969 - 19 Jun 2023

Cited by 2 | Viewed by 882

Abstract

Under strain control tests and cyclic loading, extruded magnesium alloys exhibit a special mechanism of plastic deformation (“twinning” and “de-twining”). As a result, magnesium alloys exhibit an asymmetric material behavior that cannot be fully characterized with the typical numerical tools used for steels [...] Read more.

Under strain control tests and cyclic loading, extruded magnesium alloys exhibit a special mechanism of plastic deformation (“twinning” and “de-twining”). As a result, magnesium alloys exhibit an asymmetric material behavior that cannot be fully characterized with the typical numerical tools used for steels or aluminum alloys. In this sense, a new phenomenological model, called hypo-strain, has been developed to correctly predict the cyclic stress–strain evolution of magnesium alloys. On this basis, this work aims to accurately describe the local cyclic elastic–plastic behavior of AZ31B-F magnesium alloy under multiaxial cyclic loading with Abaqus incremental plasticity. The phenomenological hypo-strain model was implemented in the UMAT subroutine of Abaqus/Standard to be used as a design tool for mechanical design. To evaluate this phenomenological approach, the results were correlated with the uniaxial and multiaxial proportional and non-proportional experimental tests. In addition, the estimates were also correlated with the Armstrong–Frederick nonlinear kinematic hardening model. The results show a good correlation between the experiments and the phenomenological hypo strain approach. The model and its implementation were validated in the strain range studied. Full article

(This article belongs to the Special Issue Crystal Plasticity (Volume III))

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16 pages, 2972 KiB

Open AccessReview

A Review of Corrosion Behavior of Structural Steel in Liquid Lead–Bismuth Eutectic

by Wentao Wang, Congxin Yang, Yuhang You and Huawei Yin

Crystals 2023, 13(6), 968; https://doi.org/10.3390/cryst13060968 - 19 Jun 2023

Cited by 1 | Viewed by 1832

Abstract

Liquid lead–bismuth eutectic alloy is one of the candidate coolants for fourth-generation nuclear power systems because of its good physical and chemical properties, neutron economic performance, and safety. However, the compatibility between the coolant and structural steel is still the main factor restricting [...] Read more.

Liquid lead–bismuth eutectic alloy is one of the candidate coolants for fourth-generation nuclear power systems because of its good physical and chemical properties, neutron economic performance, and safety. However, the compatibility between the coolant and structural steel is still the main factor restricting its large-scale industrial application in the nuclear energy field. Structural steel in a liquid lead–bismuth eutectic alloy for a long time would cause severe corrosion. The erosion of structural steel by high-flow-rate liquid lead–bismuth alloy will lead to a more complex corrosion process. This paper mainly reviews the corrosion characteristics of liquid lead–bismuth and the corrosion behavior of structural steel in liquid lead-bismuth eutectic. The main methods of inhibiting liquid lead–bismuth corrosion are summarized, and future research directions are suggested. Full article

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

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16 pages, 3685 KiB

Open AccessEditor’s ChoiceArticle

The Multi-Analytical Characterization of Calcium Oxalate Phytolith Crystals from Grapevine after Treatment with Calcination

by Gwenaëlle Trouvé, Laure Michelin, Damaris Kehrli, Ludovic Josien, Séverinne Rigolet, Bénédicte Lebeau and Reto Gieré

Crystals 2023, 13(6), 967; https://doi.org/10.3390/cryst13060967 - 18 Jun 2023

Cited by 1 | Viewed by 1497

Abstract

Calcium oxalate phytoliths are one of the most prominent types of Ca speciation in the plant kingdom, and they store extensive amounts of carbon in crystalline form. Ca phytoliths were investigated in the root, trunk, and bark of Vitis vinifera Chasselas from a [...] Read more.

Calcium oxalate phytoliths are one of the most prominent types of Ca speciation in the plant kingdom, and they store extensive amounts of carbon in crystalline form. Ca phytoliths were investigated in the root, trunk, and bark of Vitis vinifera Chasselas from a vineyard in Alsace, France. A multi-analytical approach was used, which included SEM coupled with EDX spectroscopy, XRD, XRF, TGA, and ¹³C-NMR spectroscopy. These techniques revealed that phytoliths are composed of crystalline calcium oxalate monohydrate (whewellite). The whewellite crystals exhibited mostly equant or short-prismatic habits in all of the three studied grapevine parts, but bipyramidal crystals also occurred. Raphide crystals were only observed in the root, where they were abundant. Instead of using wet chemical procedures to extract the mineral components from the organic parts of the biomass, a thermal treatment via calcination was chosen. The suitable temperature of calcination was determined through TGA experiments. The calcination of the biomass samples at 250 °C enhanced the amounts of Ca phytoliths in the residual chars. The thermal treatment, however, affected the appearance of the Ca oxalate crystals by producing surfaces that displayed macroporosity and by creating fractures. For calcination at both 300 °C and 350 °C, Ca oxalate lost a molecule of carbon monoxide to form Ca carbonate, and the modifications of the original crystal surfaces were more pronounced than those observed after thermal treatment at 250 °C. Full article

(This article belongs to the Topic Advanced Structural Crystals)

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11 pages, 4616 KiB

Open AccessArticle

Enhanced Performances of Quantum Dot Light-Emitting Diodes with an Organic–Inorganic Hybrid Hole Injection Layer

by Ling Chen, Donghuai Jiang, Wenjing Du, Jifang Shang, Dongdong Li and Shaohui Liu

Crystals 2023, 13(6), 966; https://doi.org/10.3390/cryst13060966 - 18 Jun 2023

Viewed by 1192

Abstract

PEDOT:PSS (polyethylene dioxythiophene:polystyrenesulfonate) is a commonly used hole injection layer (HIL) in optoelectronic devices due to its high conductive properties and work function. However, the acidic and hygroscopic nature of PEDOT:PSS can be problematic for device stability over time. To address this issue, [...] Read more.

PEDOT:PSS (polyethylene dioxythiophene:polystyrenesulfonate) is a commonly used hole injection layer (HIL) in optoelectronic devices due to its high conductive properties and work function. However, the acidic and hygroscopic nature of PEDOT:PSS can be problematic for device stability over time. To address this issue, in this study we demonstrated the potential of an organic–inorganic hybrid HIL by incorporating solution-processed WOx nanoparticles (WOx NPs) into the PEDOT:PSS mixture. This hybrid solution was found to have a superior hole transport ability and low Ohmic contact resistance contributing to higher brightness (~62,000 cd m⁻²) and current efficiency (13.1 cd A⁻¹) in the manufactured quantum-dot-based light-emitting diodes (QLEDs). In addition, the resulting devices achieved a relative operational lifetime of 7071 h, or approximately twice that of traditional QLEDs with PEDOT:PSS HILs. The proposed method is an uncomplicated, reliable, and low-cost way to achieve long operational lifetimes without sacrificing efficiency in optoelectronic devices. Full article

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

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13 pages, 3486 KiB

Open AccessReview

Photoaligned Liquid Crystalline Structures for Photonic Applications

by Aleksey Kudreyko, Vladimir Chigrinov, Gurumurthy Hegde and Denis Chausov

Crystals 2023, 13(6), 965; https://doi.org/10.3390/cryst13060965 - 17 Jun 2023

Cited by 2 | Viewed by 1518

Abstract

With the advancement of information display technologies, research on liquid crystals is undergoing a tremendous shift to photonic devices. For example, devices and configurations based on liquid crystal materials are being developed for various applications, such as spectroscopy, imaging, and fiber optics. One [...] Read more.

With the advancement of information display technologies, research on liquid crystals is undergoing a tremendous shift to photonic devices. For example, devices and configurations based on liquid crystal materials are being developed for various applications, such as spectroscopy, imaging, and fiber optics. One of the problems behind the development of photonic devices lies in the preparation of patterned surfaces that can provide high resolution. Among all liquid crystal alignment techniques, photoalignment represents a promising non-contact method for the fabrication of patterned surfaces. In this review, we discuss the original research findings on electro-optic effects, which were mainly achieved at the Department of Electronic and Computer Engineering of the Hong Kong University of Science and Technology and the collaborating research laboratories. Full article

(This article belongs to the Collection Reviews in Liquid Crystals)

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13 pages, 4553 KiB

Open AccessArticle

Effect of Aging Temperature on Precipitates Evolution and Mechanical Properties of GH4169 Superalloy

by Anqi Liu, Fei Zhao, Wensen Huang, Yuanbiao Tan, Yonghai Ren, Longxiang Wang and Fahong Xu

Crystals 2023, 13(6), 964; https://doi.org/10.3390/cryst13060964 - 17 Jun 2023

Cited by 1 | Viewed by 931

Abstract

GH4169 is primarily strengthened through precipitation, with heat treatment serving as a crucial method for regulating the precipitates of the alloy. However, the impact of aging temperature on the microstructure and properties of GH4169 has not been thoroughly studied, hindering effective regulation of [...] Read more.

GH4169 is primarily strengthened through precipitation, with heat treatment serving as a crucial method for regulating the precipitates of the alloy. However, the impact of aging temperature on the microstructure and properties of GH4169 has not been thoroughly studied, hindering effective regulation of its microstructure and properties. This study systematically investigated the effects of aging temperature on the evolution of precipitates and mechanical properties of GH4169 alloy using various techniques such as OM, SEM, XRD and TEM. The results indicate that raising the aging temperature leads to an increase in the sizes of both the γ″ and γ′ phases in the alloy, as well as promoting the precipitation of δ phase at grain boundaries. Notably, the increase in γ″ phase size enhances the strength of the alloy, while the presence of δ phase is detrimental to its strength but greatly enhances its elongation. The yield strength of the alloy aged at 750 ℃ exhibits the highest yield strength, with values of 1135 MPa and 1050 MPa at room temperature and elevated temperature, respectively. As the aging temperature increases, the Portevin-Le Châtelier (PLC) effect during elevated temperature tensile tests at 650 ℃ gradually weakens. The PLC effect disappears almost completely when the aging temperature reaches 780 ℃. Full article

(This article belongs to the Special Issue Advanced Crystalline Materials, Mechanical Properties and Innovative Production Systems)

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15 pages, 2342 KiB

Open AccessArticle

Atomic Arrangement, Hydrogen Bonding and Structural Complexity of Alunogen, Al₂(SO₄)₃·17H₂O, from Kamchatka Geothermal Field, Russia

by Elena S. Zhitova, Rezeda M. Sheveleva, Andrey A. Zolotarev and Anton A. Nuzhdaev

Crystals 2023, 13(6), 963; https://doi.org/10.3390/cryst13060963 - 16 Jun 2023

Cited by 1 | Viewed by 923

Abstract

Alunogen, Al₂(SO₄)₃·17H₂O, occurs as an efflorescent in acid mine drainage, low-temperature fumarolic or pseudofumarolic (such as with coal fires) terrestrial environments. It is considered to be one of the main Al-sulphates of Martian soils, demanding [...] Read more.

Alunogen, Al₂(SO₄)₃·17H₂O, occurs as an efflorescent in acid mine drainage, low-temperature fumarolic or pseudofumarolic (such as with coal fires) terrestrial environments. It is considered to be one of the main Al-sulphates of Martian soils, demanding comprehensive crystal-chemical data of natural terrestrial samples. Structural studies of natural alunogen were carried out in the 1970s without localization of H atoms and have not been previously performed for samples from geothermal fields, despite the fact that these environments are considered to be proxies of the Martian conditions. The studied alunogen sample comes from Verkhne–Koshelevsky geothermal field (Koshelev volcano, Kamchatka, Russia). Its chemical formula is somewhat dehydrated, Al₂(SO₄)₃·15.8H₂O. The crystal structure was solved and refined to R₁ = 0.068 based on 5112 unique observed reflections with I > 2σ(I). Alunogen crystalizes in the P-1 space group, a = 7.4194(3), b = 26.9763(9), c = 6.0549(2) Å, α = 90.043(3), β = 97.703(3), γ = 91.673(3) °, V = 1200.41(7) Å³, Z = 2. The crystal structure consists of isolated SO₄ tetrahedra, Al(H₂O)₆ octahedra and H₂O molecules connected by hydrogen bonds. The structure refinement includes Al, S and O positions that are similar to previous structure determinations and thirty-four H positions localized for the natural sample first. The study also shows the absence of isomorphic substitutions in the composition of alunogen despite the iron-enriched environment of mineral crystallization. The variability of the alunogen crystal structure is reflected in the number of the “zeolite” H₂O molecules and their splitting. The structural complexity of alunogen and its modifications ranges from 333–346 bits/cell for models with non-localized H atoms to 783–828 bits/cell for models with localized H atoms. The higher values correspond to the higher hydration state of alunogen. Full article

(This article belongs to the Special Issue Mineralogical Crystallography (3rd Edition))

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9 pages, 3636 KiB

Open AccessArticle

Collective Relaxation Processes in Nonchiral Nematics

by Neelam Yadav, Yuri P. Panarin, Wanhe Jiang, Georg H. Mehl and Jagdish K. Vij

Crystals 2023, 13(6), 962; https://doi.org/10.3390/cryst13060962 - 16 Jun 2023

Viewed by 877

Abstract

Nematic–nematic transitions in a highly polar nematic compound are studied, in thick cells in which the molecules are aligned parallel to the substrates but perpendicular to the applied electric field, using dielectric spectroscopy in the frequency range 1 Hz to 10 MHz over [...] Read more.

Nematic–nematic transitions in a highly polar nematic compound are studied, in thick cells in which the molecules are aligned parallel to the substrates but perpendicular to the applied electric field, using dielectric spectroscopy in the frequency range 1 Hz to 10 MHz over a wide temperature range. The studied compound displays three nematic phases under cooling from the isotropic phase: ubiquitous nematic N; high polarizability N_X; and ferroelectric nematic N_F. Two collective processes were observed. The dielectric strength and relaxation frequency of one of the processes P₂ showed a dependence on the thickness of the cell. The process P₁ is the amplitude mode, while the process P₂ is the phason mode. Full article

(This article belongs to the Special Issue Nematic Liquid Crystal)

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15 pages, 5089 KiB

Open AccessArticle

Nitrogen-Doped Graphene Quantum Dot–Tin Dioxide Nanocomposite Ultrathin Films as Efficient Electron Transport Layers for Planar Perovskite Solar Cells

by Ha Chi Le, Nam Thang Pham, Duc Chinh Vu, Duy Long Pham, Si Hieu Nguyen, Thi Tu Oanh Nguyen and Chung Dong Nguyen

Crystals 2023, 13(6), 961; https://doi.org/10.3390/cryst13060961 - 16 Jun 2023

Cited by 5 | Viewed by 1364

Abstract

Tin dioxide (SnO₂) has recently been recognized as an excellent electron transport layer (ETL) for perovskite solar cells (PSCs) due to its advantageous properties, such as its high electron mobility, suitable energy band alignment, simple low-temperature process, and good chemical stability. [...] Read more.

Tin dioxide (SnO₂) has recently been recognized as an excellent electron transport layer (ETL) for perovskite solar cells (PSCs) due to its advantageous properties, such as its high electron mobility, suitable energy band alignment, simple low-temperature process, and good chemical stability. In this work, nitrogen-doped graphene quantum dots (N-GQDs) were prepared using a hydrothermal method and then used to fabricate N-GQD:SnO₂ nanocomposite ultrathin films. N-GQD:SnO₂ nanocomposite ultrathin films were investigated and applied as electron transport layers in planar PSCs. The presence of N-GQDs with an average size of 6.2 nm in the nanocomposite improved its morphology and reduced surface defects. The excitation–emission contour map indicated that the N-GQDs exhibited a remarkably enhanced light-harvesting capability due to the possibility of absorbing UV light and producing emissions in the visible range. The quenching of photoluminescence spectra showed that the N-GQDs in nanocomposite ultrathin films improved electron extraction and reduced charge recombination. As a result, the power conversion efficiency (PCE) of our planar PSCs fabricated with the optimized N-GQD:SnO₂ nanocomposite electron transport layer was improved by 20.4% over pristine SnO₂-based devices. Full article

(This article belongs to the Special Issue Recent Advances and Applications of Nanomaterials)

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13 pages, 3681 KiB

Open AccessArticle

Structural, Morphological and Dielectric Characterization of BiFeO₃ Fibers Grown by the LFZ Technique

by Marina Vieira Peixoto, Florinda Mendes Costa, Susana Devesa and Manuel Pedro Fernandes Graça

Crystals 2023, 13(6), 960; https://doi.org/10.3390/cryst13060960 - 16 Jun 2023

Cited by 1 | Viewed by 897

Abstract

BiFeO₃ fibers were prepared by the Laser Floating Zone (LFZ) technique using different growth speeds. The structural characterization of the samples was undertaken using X-ray diffraction (XRD) and Raman spectroscopy, the morphological characterization by scanning electron microscopy (SEM), and the electrical characterization [...] Read more.

BiFeO₃ fibers were prepared by the Laser Floating Zone (LFZ) technique using different growth speeds. The structural characterization of the samples was undertaken using X-ray diffraction (XRD) and Raman spectroscopy, the morphological characterization by scanning electron microscopy (SEM), and the electrical characterization by impedance spectroscopy. The XRD patterns showed that BiFeO₃ was the major phase in all the samples. Fibers grown at 10 mm/h showed more promising structural and morphological properties. The dielectric characterization revealed that all samples have at least one dielectric relaxation phenomenon that is thermally activated. It was also verified that the dielectric constant is higher at a growth pull rate speed of 10 mm/h. Full article

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13 pages, 1270 KiB

Open AccessReview

A Survey on Zeolite Synthesis and the Crystallization Process: Mechanism of Nucleation and Growth Steps

by Zahra Asgar Pour, Yasser A. Alassmy and Khaled O. Sebakhy

Crystals 2023, 13(6), 959; https://doi.org/10.3390/cryst13060959 - 15 Jun 2023

Cited by 3 | Viewed by 2330

Abstract

Zeolites, as a class of crystalline minerals, find a wide range of applications in various fields, such as catalysis, separation, and adsorption. More recently, these materials have also been developed for advanced applications, such as gas storage, medical applications, magnetic adsorption, and zeolitic-polymeric [...] Read more.

Zeolites, as a class of crystalline minerals, find a wide range of applications in various fields, such as catalysis, separation, and adsorption. More recently, these materials have also been developed for advanced applications, such as gas storage, medical applications, magnetic adsorption, and zeolitic-polymeric membranes. To effectively design zeolites for such intriguing applications, it is crucial to intelligently adjust their crystal size, morphology, and defect population in relation to crystal perfection. Optimizing these fundamental parameters necessitates a deep understanding of zeolite formation mechanisms, encompassing the thermodynamics and kinetics of nucleation steps as well as crystallite growth. In this review, we discuss the formation of zeolites from this perspective, drawing on recent studies that highlight new achievements in remodeling and modifying zeolite synthesis routes. The ultimate aim is to provide better comprehension and optimize the functionality of zeolites for the aforementioned applications. Full article

(This article belongs to the Special Issue Crystallization Process and Simulation Calculation, Second Edition)

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Graphical abstract

18 pages, 66797 KiB

Open AccessArticle

Phase-Only Liquid-Crystal-on-Silicon Spatial-Light-Modulator Uniformity Measurement with Improved Classical Polarimetric Method

by Xinyue Zhang and Kun Li

Crystals 2023, 13(6), 958; https://doi.org/10.3390/cryst13060958 - 15 Jun 2023

Viewed by 1140

Abstract

The classical polarimetric method has been widely used in liquid crystal on silicon (LCoS) phase measurement with a simple optical setup. However, due to interference caused by LCoS cover glass reflections, the method lacks accuracy for phase uniformity measurements. This paper is aimed [...] Read more.

The classical polarimetric method has been widely used in liquid crystal on silicon (LCoS) phase measurement with a simple optical setup. However, due to interference caused by LCoS cover glass reflections, the method lacks accuracy for phase uniformity measurements. This paper is aimed at mathematically analyzing the errors caused by non-ideal glass reflections and proposing procedures to reduce or eliminate such errors. The measurement is discussed in three conditions, including the ideal condition with no reflections from the LCoS cover glass, the condition with only the front reflection from the cover glass, and the condition with only the back reflection from the cover glass. It is discovered that the backward reflection makes the largest contribution to the overall measurement error, and it is the main obstacle to high-quality measurements. Several procedures, including optical alignment, LC layer thickness measurement, and phase estimation method, are proposed, making the uniformity measurement more qualitative and consistent. Full article

(This article belongs to the Special Issue Advances in Liquid Crystal Optical Devices)

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21 pages, 7219 KiB

Open AccessEditor’s ChoiceArticle

TIC Reorientation under Electric and Magnetic Fields in Homeotropic Samples of Cholesteric LC with Negative Dielectric Anisotropy

by Patrick Oswald, Guilhem Poy and Jordi Ignés-Mullol

Crystals 2023, 13(6), 957; https://doi.org/10.3390/cryst13060957 - 15 Jun 2023

Viewed by 670

Abstract

In this paper, we numerically and experimentally show that the director field orientation degeneracy within the Translationally Invariant Configuration (TIC) of a cholesteric liquid crystal under an electric field can be lifted by imposing a magnetic field

\vec{B}

parallel to the electrodes. [...] Read more.

In this paper, we numerically and experimentally show that the director field orientation degeneracy within the Translationally Invariant Configuration (TIC) of a cholesteric liquid crystal under an electric field can be lifted by imposing a magnetic field

\vec{B}

parallel to the electrodes. The configuration can be either parallel or perpendicular to the magnetic field depending on the values of the sample thickness, pitch, and applied voltage, with two equiprobable orientations in each case. The transition between the parallel and perpendicular orientations has hysteresis, suggesting that it is first order. When

\vec{B}

is slightly tilted with respect to the electrode plane, the indeterminacy on the TIC orientation is removed when the TIC is directed along

\vec{B}

. Full article

(This article belongs to the Special Issue Feature Articles in Liquid Crystals from Our Editorial Board Members and Their Colleagues, 2022/2023)

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15 pages, 3199 KiB

Open AccessArticle

Novel Porous Organic Polymer for High-Performance Pb(II) Adsorption from Water: Synthesis, Characterization, Kinetic, and Isotherm Studies

by Saad Melhi, Eid H. Alosaimi, Belal El-Gammal, Wafa A. Alshahrani, Yasser F. El-Aryan, Hamdan A. Al-Shamiri and Habib Elhouichet

Crystals 2023, 13(6), 956; https://doi.org/10.3390/cryst13060956 - 15 Jun 2023

Cited by 1 | Viewed by 1024

Abstract

The aim of the current study was to develop a novel triphenylaniline-based porous organic polymer (TPABPOP-1) by the Friedel–Crafts reaction for the efficient elimination of Pb(II) from an aqueous environment. XPS, FTIR, SEM, TGA, and ¹³C CP/MAS NMR analyses were applied to [...] Read more.

The aim of the current study was to develop a novel triphenylaniline-based porous organic polymer (TPABPOP-1) by the Friedel–Crafts reaction for the efficient elimination of Pb(II) from an aqueous environment. XPS, FTIR, SEM, TGA, and ¹³C CP/MAS NMR analyses were applied to characterize the synthesized TPABPOP-1 polymer. The BET surface area of the TPABPOP-1 polymer was found to be 1290 m²/g. FTIR and XPS techniques proved the uptake of Pb(II) was successfully adsorbed onto TPABPOP-1. Using batch methods, Pb(II) ion adsorption on the TPABPOP-1 was studied at different equilibrium times, pH values, initial Pb(II) concentration, adsorption mass, and temperature. The outcomes exhibited that the optimum parameters were t: 180 min, m: 0.02 g, pH: 5, T: 308 K, and [Pb(II)]: 200 mg/L. Nonlinear isotherms and kinetics models were investigated. The Langmuir isotherm model suggested that the uptake of Pb(II) was favorable on the homogeneous surface of TPABPOP-1. Adsorption kinetics showed that the PFO model was followed. Pb(II) removal mechanisms of TPABPOP-1 may include surface adsorption and electrostatic attraction. The uptake capacity for Pb(II) was identified to be 472.20 mg/g. Thermodynamic factors exhibited that the uptake of Pb(II) was endothermic and spontaneous in standard conditions. Finally, this study provides effective triphenylaniline-based porous organic polymers (TPABPOP-1) as a promising adsorbent with high uptake capacity. Full article

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15 pages, 6688 KiB

Open AccessArticle

Phase Structures and Dielectric Properties of (n + 1)SrO − nCeO₂ (n = 2) Microwave Ceramic Systems with TiO₂ Addition

by Qi Su, Jingjing Qu, Fei Liu, Changlai Yuan, Xiao Liu, Mingwei Su, Liufang Meng and Guohua Chen

Crystals 2023, 13(6), 955; https://doi.org/10.3390/cryst13060955 - 15 Jun 2023

Viewed by 849

Abstract

Ti⁴⁺-ion-doped (n + 1)SrO − nCeO₂ (n = 2) ceramic systems were prepared with the conventional solid-state reaction method, and the effects of the phase structures and compositions, sintering behaviors, microstructures and microwave dielectric properties of these [...] Read more.

Ti⁴⁺-ion-doped (n + 1)SrO − nCeO₂ (n = 2) ceramic systems were prepared with the conventional solid-state reaction method, and the effects of the phase structures and compositions, sintering behaviors, microstructures and microwave dielectric properties of these ceramic systems were investigated in detail as a function of TiO₂ content. The analytical results of the XRD patterns show that the pure (n + 1)SrO − nCeO₂ (n = 2) system is a composite-phase ceramic system with coexisting SrCeO₃ and Sr₂CeO₄ phases (represented as a SrCeO₃ + Sr₂CeO₄ system), which belong to the orthogonal structures of the Pmcn (62) and Pbam (55) space groups, respectively. For the xTiO₂-(1 − x) (SrCeO₃ + Sr₂CeO₄) (x = 0.1–0.4) ceramic samples, the secondary phase Sr₂TiO₄ can also be detected within the range of the investigated components. Meanwhile, the Raman spectroscopy, SEM-EDS, and HRTEM (SAED) analysis results also verified the correctness and consistency of the phase structures and compositions for all the given specimens. In addition, complex impedance spectroscopy was used to detect the conductive behavior of these compound ceramic systems, and the calculation results show that the appropriate addition of Ti⁴⁺-ions can make the SrCeO₃ + Sr₂CeO₄ system have better thermal stability. The composition of x = 0.2 multiphase structural ceramic sample sintered at 1330 °C for 4 h has a near zero τ_f value of ~−4.6 ppm/°C, a moderate ε_r of ~40.3 and a higher Q × f~44,020 GHz (at 6.56 GHz). The relatively superior-performing ceramics developed in this work are expected to provide a promising microwave dielectric material for communication components. Full article

(This article belongs to the Special Issue Microwave Dielectric Ceramics)

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14 pages, 5284 KiB

Open AccessArticle

Cerium Niobate Hollow Sphere Engineered Graphitic Carbon Nitride for Synergistic Photothermal/Chemodynamic Cancer Therapy

by Kayalvizhi Samuvel Muthiah, Senthilkumar Thirumurugan, Yu-Chien Lin, Rajalakshmi Sakthivel, Udesh Dhawan, An-Ni Wang, Michael Hsiao and Ren-Jei Chung

Crystals 2023, 13(6), 954; https://doi.org/10.3390/cryst13060954 - 15 Jun 2023

Viewed by 1143

Abstract

Reactive oxygen species (ROS)-mediated chemodynamic therapy (CDT) and photothermal therapy (PTT) have potential for various cancer treatments. However, they are still bound by the demands of Fenton reaction conditions such as oxygen dependence, inherent defects in common standard photosensitizers (PSs), and the continuous [...] Read more.

Reactive oxygen species (ROS)-mediated chemodynamic therapy (CDT) and photothermal therapy (PTT) have potential for various cancer treatments. However, they are still bound by the demands of Fenton reaction conditions such as oxygen dependence, inherent defects in common standard photosensitizers (PSs), and the continuous availability of laser sources. Herein, we designed Ce₃NbO₇/g-C₃N₄ nanocomposites (NCs) and investigated their ability to evaluate the performance of PTT/CDT synergistically to enhance cancer treatment. The activation of Ce₃NbO₇/g-C₃N₄ NCs in the tumor microenvironment (TME) causes the generation of cytotoxic ROS via the Fenton reaction. Additionally, the g-C₃N₄ in NCs absorbs NIR, generating hyperthermia in the TME. The photothermal conversion efficiency (ƞ) of the Ce₃NbO₇/g-C₃N₄ NCs was found to be 49.5%. A photocatalytic reaction with PTT-enhanced Fenton reagents, without consuming additional photothermal agents (PTA) or Fenton reagents, generates the hydroxyl radical (OH•) primarily by direct electron transfer in the TME. Almost 68% of cells experienced programmed cell death due to the combinational effect (PTT/CDT), making it an efficient and biocompatible therapy. Furthermore, this work provides a basis for developing numerous innovative materials that can be used to treat cancer, overcome general limitations, and enhance ROS production under single-wavelength (808 nm) laser irradiation. Full article

(This article belongs to the Special Issue Pharmaceutical Crystals (Volume III))

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