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Crystals
Volume 13
Issue 6
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Crystals, Volume 13, Issue 6 (June 2023) – 129 articles

Cover Story (view full-size image): Surface chemistry and roughness influence surface energy and hence the wettability of the material’s surface. We have analysed the time dependence of the oxide layer growth and possible surface adsorbates on the surface topography of an Al59Cu25Fe13B3 quasicrystalline material in relation to changes in the surface energy. Under ambient conditions, the quasicrystal was naturally covered by an oxide layer; we refer to its surface energy as “surfenergy” to distinguish it from the conventional surface energy of a bare quasicrystal surface. The surfenergy depends on the polar component, which is the most sensitive to the material’s processing and may be tuned over more than an order of magnitude. The results indicate possible routes for the engineering and fine-tuning of quasicrystalline surfaces. View this paper
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13 pages, 3314 KiB  
Article
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 5 | Viewed by 2382
Abstract
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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Figure 1
<p>(<b>a</b>,<b>b</b>) the TEM of the CQDs; (<b>c</b>) the particle size distribution map; (<b>d</b>) the EDS of the CQDs; (<b>e</b>,<b>f</b>) the XRD of the CQDs.</p> Full article ">Figure 2
<p>(<b>a</b>) The UV-Vis and FL of CQDs; (<b>b</b>) the FTIR of CQDs.</p> Full article ">Figure 3
<p>Adsorption mechanism of CQDs for PS microplastics.</p> Full article ">Figure 4
<p>(<b>a</b>) Emission spectra of CQDs with different concentrations; (<b>b</b>) emission spectra of CQDS with different concentrations added to PS; (<b>c</b>) changes in fluorescence intensity of CQDs and PS-CQDs at 426 nm; (<b>d</b>) changes in fluorescence intensity of CQDS and PS-CQDs at 659 nm.</p> Full article ">Figure 5
<p>(<b>a</b>) Fluorescence spectra of PS-CQDs; (<b>b</b>) fluorescence spectra of PS-CQDs at 426 nm; (<b>c</b>) fitting curve of PS-CQDS at 426 nm; (<b>d</b>) fitting curve of PS-CQDs at 659 nm; (<b>e</b>) fluorescence spectra of different concentrations of PS; (<b>f</b>) fitting curve of PS at 659 nm.</p> Full article ">Figure 6
<p>(<b>a</b>) Fluorescence spectra of PS-CQDs under different pH conditions; (<b>b</b>) fluorescence intensity of PS-CQDs at 659 nm with pH; (<b>c</b>) fluorescence spectra at different illumination times; (<b>d</b>) 426 nm and 659 nm fluorescence intensities over time.</p> Full article ">
19 pages, 5560 KiB  
Article
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
Cited by 1 | Viewed by 1224
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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<p>MarBN steel microstructure: (<b>a</b>) after rolling and before standardization annealing and tempering, (<b>b</b>) after standardization annealing and tempering, LM, etch.</p> Full article ">Figure 2
<p>Particles morphology and distribution in the microstructure of initial steel state (<b>a</b>,<b>b</b>). Particles present in the area of prior austenite grain boundaries (<b>c</b>); particles present in the area of tempered martensite (<b>d</b>); particles present in the area of tempered bainite (<b>e</b>); and present particles in steel substructure (<b>f</b>), with SAED pattern and corresponding phase analysis. The red circles on the bright field images (<b>c</b>–<b>f</b>) mark the area corresponding to the SAED.</p> Full article ">Figure 3
<p>Cross-section of the oxidized steel with concentration profiles of analyzed elements across the oxide layer at temperature 600 °C after (<b>a</b>,<b>b</b>) 500 h, (<b>c</b>,<b>d</b>) 1000 h, (<b>e</b>,<b>f</b>) 3000 h oxidation, SEM.</p> Full article ">Figure 4
<p>EDS maps of analyzed elements distribution after 500 h of oxidation at 600 °C.</p> Full article ">Figure 5
<p>EDS maps of analyzed elements distribution after 3000 h of oxidation at 600 °C.</p> Full article ">Figure 6
<p>XRD phase analysis of the MarBN steel oxide layer after oxidation at 600 °C.</p> Full article ">Figure 7
<p>Cross-section of the oxidized steel with concentration profiles of analyzed elements across the oxide layer at temperature 650 °C after (<b>a</b>,<b>b</b>) 500 h, (<b>c</b>,<b>d</b>) 1000 h, (<b>e</b>,<b>f</b>) 3000 h oxidation, SEM.</p> Full article ">Figure 8
<p>EDS distribution maps of analyzed elements after 500 h of oxidation at 650 °C.</p> Full article ">Figure 9
<p>EDS distribution maps of analyzed elements after 3000 h of oxidation at 650 °C.</p> Full article ">Figure 10
<p>XRD phase analysis of the MarBN steel oxide layer after oxidation at 650 °C.</p> Full article ">Figure 11
<p>(<b>a</b>,<b>b</b>) Particles morphology and distribution in the microstructure of steel after exposure to the oxidizing furnace atmosphere (650 °C for 3000 h). (<b>c</b>) Coarse particles present in the zone under the oxide layer; (<b>d</b>) thin particles present in the zone under the oxide layer; (<b>e</b>) particles present in the area of prior austenite grain boundaries; (<b>f</b>) particles present in the area of tempered martensite; (<b>g</b>) particles present in the area of tempered bainite; and (<b>h</b>) present particles in steel substructure with SAED pattern and corresponding phase analysis. The red circles on the bright field images (<b>c</b>–<b>f</b>) mark the area corresponding to the SAED.</p> Full article ">Figure 11 Cont.
<p>(<b>a</b>,<b>b</b>) Particles morphology and distribution in the microstructure of steel after exposure to the oxidizing furnace atmosphere (650 °C for 3000 h). (<b>c</b>) Coarse particles present in the zone under the oxide layer; (<b>d</b>) thin particles present in the zone under the oxide layer; (<b>e</b>) particles present in the area of prior austenite grain boundaries; (<b>f</b>) particles present in the area of tempered martensite; (<b>g</b>) particles present in the area of tempered bainite; and (<b>h</b>) present particles in steel substructure with SAED pattern and corresponding phase analysis. The red circles on the bright field images (<b>c</b>–<b>f</b>) mark the area corresponding to the SAED.</p> Full article ">
8 pages, 2911 KiB  
Communication
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 3 | Viewed by 1543
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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<p>The research outline of this investigation.</p> Full article ">Figure 2
<p>(<b>a</b>) The atomic structure, (<b>b</b>) the simulated STM image and the DS-PAW calculated image (<b>c</b>). Phonon dispersions spectra of the SiP<sub>2</sub> monolayer; the red and blue balls are P and Si atom, respectively.</p> Full article ">Figure 3
<p>The calculated total energy and the temperature fluctuation in the AIMD simulation of the SiP<sub>2</sub> monolayer under different temperatures; the inset images present the atomic structure of the SiP<sub>2</sub> monolayer after 10 ps, the red and blue lines represent the temperature and energy, respectively.</p> Full article ">Figure 4
<p>(<b>a</b>) The DS-PAW calculated projected band structure; (<b>b</b>) the band edge energy of the SiP<sub>2</sub> monolayer compared with TMDs at pH 0, with the vacuum level set at 0 eV; (<b>c</b>) the optical absorption spectrum.</p> Full article ">Figure 5
<p>(<b>a</b>) The total energy and the (<b>b</b>) band edge positions of the SiP<sub>2</sub> monolayer under different external strains calculated by using DS-PAW.</p> Full article ">Figure 6
<p>(<b>a</b>) The favorable H-adsorbed site on the SiP<sub>2</sub> monolayer configuration and (<b>b</b>) the calculated Gibbs free energy of the SiP<sub>2</sub> system obtained by using DS-PAW.</p> Full article ">
19 pages, 5872 KiB  
Article
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 1273
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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Figure 1

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<p>Sequence analysis. (<b>a</b>) Amino acid sequence alignment for isolated <span class="html-italic">Gc</span>GDH and other reported GDHs. The sequences selected for alignment were similar to those of the GDH3 NADP(+)-dependent glutamate dehydrogenase from <span class="html-italic">Geotrichum candidum</span> (GenBank accession number CDO55948.1), YALI0F17820p from <span class="html-italic">Yarrowia lipolytica</span> CLIB122 (GenBank accession number XP_505553.1), glutamate dehydrogenase (NADP(+)) GDH1 from <span class="html-italic">Sugiyamaella lignohabitans</span> (GenBank accession number ANB13598.1), unnamed protein product from <span class="html-italic">Kuraishia capsulata</span> CBS 1993 (GenBank accession number CDK26318.1), glutamate dehydrogenase (NADP+) from <span class="html-italic">Talaromyces islandicus</span> (GenBank accession number CRG85500.1), and NADP(+)-dependent glutamate dehydrogenase from <span class="html-italic">Komagataellapastoris</span> GS115 (GenBank accession number XP_002489750.1). Identical residues are shaded in black and conserved residues are shaded in gray. (<b>b</b>) Phylogenetic tree of the glutamate dehydrogenase amino acid sequences from different organisms. Bootstrap values (%) are indicated at the nodes, and the scale bars represent 0.1 substitutions per site.</p> Full article ">Figure 2
<p>Molecular properties of purified GcGDH. (<b>a</b>) SDS-PAGE of purified GcGDH. M: protein molecular weight markers; 1: null vector transfection (control); 2: crude GcGDH; 3: penetrating crude GcGDH from Ni column; 4: purified pET-28as-GcGDH (with elution buffer containing 120 imidazole). Arrow indicates target protein. (<b>b</b>) Results of Western blot analysis. M: protein molecular weight markers; 1: null vector transfection (control); 2: crude GcGDH; 3: penetrating crude GcGDH from Ni column; 4: purified pET-28as-GcGDH (with elution buffer containing 120 imidazole). Arrow indicates target protein. (<b>c</b>) Removal of GcGDH SUMO tag by SUMO protease. aI: crude GcGDH containing the SUMO tag. M: protein molecular weight markers; 1: null vector transfection (control); a2: total expressed protein; a3: supernatant protein; a4: supernatant protein containing SUMO tag after removal by SUMO protease. bII: purified protein after passing through His-binding column. b1: purified protein containing SUMO tag cut by SUMO protease. The arrows (about 66 kDA) in Figure C a3 and Figure C b1 represent the GCGDH containing the SUMO tag; The arrows (about 50 kDA) in Figure C a4 and Figure C b1 represent the GCGDH (removal of GCGDH SUMO tag by SUMO protease); The arrows (about 16 kDA) in Figure C a4 and Figure C b1 represent the SUMO tag.3.3. Crystallization of GcGDH.</p> Full article ">Figure 3
<p><span class="html-italic">Gc</span>GDH crystals were grown using the sitting drop vapor diffusion method at 20 °C. (<b>A</b>) Crystals were initially obtained, but they were small and irregular. (<b>B</b>) After optimizing the crystallization conditions, the best quality protein crystal with a diffraction resolution of 2.3 Å was isolated from the crystallization reservoir solution.</p> Full article ">Figure 4
<p>Representative portion of electron density in <span class="html-italic">Gc</span>GDH after refinement. The map (2<span class="html-italic">Fo–Fc</span>) was contoured at 1σ levels and calculated using the final model at 2.3 Å. Initially, our model was built using the amino acid sequence, corresponding parameters, and data. Then, the model was rebuilt using ARP/wARP. Atomic model fitting and refinement were performed with Phenix and Coot. The blue, white, and pale red colored bonds represent carbon, nitrogen, and oxygen atoms, respectively.</p> Full article ">Figure 5
<p>(<b>A</b>) <span class="html-italic">Gc</span>GDH structure comprised of 12 subunits organized into an asymmetric unit. (<b>B</b>) Each subunit consists of 452 amino acids (including 15 α-helices, 7 β-sheets, and a coil), which can be also divided into 2 domains: an N-terminal substrate-binding domain, which includes residues 1–189 and 429–452, (red; α1–α7, α13, α15, and β1-β5), and a C-terminal cofactor-binding domain, which consists of residues 190–428 (cyan; α8-α12, α14, β6, and β7).</p> Full article ">Figure 6
<p>(<b>A</b>) T-coffee was used to perform multiple sequence alignment (MSA) between the target protein <span class="html-italic">Gc</span>GDH and its homologous proteins. The results indicated that differences between GDHs were more notable when the proteins were from different species. The proteins are abbreviated as follows: <span class="html-italic">Gc</span>GDH (GDH from <span class="html-italic">Geotrichum candidum</span> AHX58293.1), HsGDH (GDH from <span class="html-italic">Homo sapiens</span> NP_001305830.1), BtGDH (GDH from <span class="html-italic">Bos taurus</span> NP_872593.2), AnGDH (GDH from <span class="html-italic">Aspergillus niger</span> 5XVI-apo), ScGDH (GDH from <span class="html-italic">Saccharomyces cerevisiae</span> AAA34642.1), CgGDH (GDH from <span class="html-italic">Corynebacterium glutamicum</span> 5IJZ_A), EcGDH (GDH from <span class="html-italic">Escherichia coli</span> 4FCC_A), CrGDH (GDH from <span class="html-italic">Chlamydomonas reinhardtii</span> XP_001694545.1), PfGDH (GDH from <span class="html-italic">Plasmodium Falciparum</span> 2MBA_A), HaGDH (GDH from <span class="html-italic">Halophilic archaeon</span> AEN06106.1), and EpGDH (GDH from <span class="html-italic">Escherichia phage</span> YP_007348518.1). The MSA results also revealed that there were many conserved domains among the GDHs, which are important to forming the secondary structure in many species. However, some residues in these areas do differ among the different species, and especially in highly variable regions. Red boxes represent the high sequence homology between the target protein <span class="html-italic">Gc</span>GDH and its homologous proteins. (<b>B</b>) A phylogenetic tree of GDHs was constructed using Mega7 with the maximum likelihood method and the bootstrap value set to 500. The final distance results were displayed using the online tool iTOL. These results indicated that GDH is an ancient enzyme with strict evolutionary conservation. The enzyme commonly exists across many species, from plants to animals and protozoa to Chordata, which reveals the importance of GDH to life. Colors in the figure are coded as follows. Blue: Chordata; orange: Arthropoda; dark green: Nematoda; pale green: Annelida; white: Platyhelminthes; purple: protozoa; light purple: Fungi; and green: Plantae. All sequence data were extracted from the NCBI database.</p> Full article ">Figure 7
<p>(<b>A</b>–<b>C</b>) Comparison of the tertiary structures of <span class="html-italic">Gc</span>GDH and AnGDH (glutamate dehydrogenase from <span class="html-italic">Aspergillus niger</span>) using PyMol. Although <span class="html-italic">Gc</span>GDH and AnGDH are highly homologous, their tertiary structures are not exactly the same. Importantly, Lys 113 (yellow) is known to be associated with substrate combination.</p> Full article ">Figure 8
<p>Effects of metal ions, chemical regents, and cofactors on enzymatic activity towards (<b>a</b>) MSG and (<b>b</b>) hexanol.</p> Full article ">Figure 9
<p>Effects of temperature and pH on the activity and stability of <span class="html-italic">Gc</span>GDH. (<b>a</b>) MSG and (<b>c</b>) hexanol temperature profiles. (<b>b</b>) MSG and (<b>d</b>) hexanol pH profiles. Each of the following buffers were used at 100 mM: Na<sub>2</sub>HPO<sub>4</sub>/citric acid (pH = 2.2–8.0), Tis-HCl (pH = 8.0–9.0), and Na2CO3/NaOH (pH = 9.0–10.5). (<b>e</b>) Glutamate and (<b>g</b>) hexanol thermal stabilities. (<b>f</b>) MSG and (<b>h</b>) hexanol pH stabilities. Each of the following buffers were used at 100 mM: Na<sub>2</sub>HPO<sub>4</sub>/citric acid (pH = 2.2–8.0), Tis-HCl (pH = 8–10), and Na<sub>2</sub>CO<sub>3</sub>/NaOH (pH = 10–11). To minimize experimental error, both the substrate solution and cuvette were heated to the corresponding temperature, and the activity measured immediately.</p> Full article ">Figure 10
<p><span class="html-italic">Gc</span>GDH activity towards various substrates. Substrate-dependent plots for the oxidation or reduction of (<b>a</b>) MSG, (<b>b</b>) hexanol, (<b>c</b>) NADP<sup>+</sup> with MSG as substrate, and (<b>d</b>) NADP<sup>+</sup> with hexanol as substrate using purified <span class="html-italic">Gc</span>GDH (2 mg/mL). The reaction incubation time was 50 s for MSG and 1 h for hexanol. The wavelength for the substrates (MSG and NADP<sup>+</sup>) was 340 nm. The substrates (hexanol and NADP<sup>+</sup>) were analyzed using GC. Each point represents the mean of two experiments carried out in triplicates.</p> Full article ">Figure 11
<p>Activity of the wild-type and mutant <span class="html-italic">Gc</span>GDHs. (<b>a</b>) Activity of wild type <span class="html-italic">Gc</span>GDH and Lys 113 mutant enzymes towards MSG. (<b>b</b>) Activity of wild-type <span class="html-italic">Gc</span>GDH and Lys 113 mutant enzymes towards hexanol.</p> Full article ">
17 pages, 6024 KiB  
Article
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 1631
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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Figure 1
<p>Comparison of the powder diffraction patterns of all ZSM-5 samples in the entire angle range investigated (<b>left</b>) and in the angle range 8.0–14.0° 2θ (<b>right</b>). The characteristic doublet of monoclinic phase peaks at room temperature becomes a broad single peak for the sample ZSM-5c_15, characteristic of the orthorhombic polymorph.</p> Full article ">Figure 2
<p>Lattice parameters (<b>a</b>), β angle (<b>b</b>) and unit-cell volume (<b>c</b>) of the four investigated ZSM-5c zeolite samples as a function of the Si/Al ratio at room temperature. Dashed lines are a reader’s guide. Error bars are within the symbol size.</p> Full article ">Figure 3
<p>Example of peak merging (the characteristic doublet of monoclinic phase peaks at room temperature becomes a single peak at high temperature, characteristic of the orthorhombic polymorph) for the samples 20 (<b>a</b>), 37 (<b>b</b>) and 69 (<b>c</b>) in the 12.90–13.25° 2θ regions, while the sample ZSM-5c_15 (<b>d</b>) retains the orthorhombic symmetry throughout the investigated thermal range.</p> Full article ">Figure 3 Cont.
<p>Example of peak merging (the characteristic doublet of monoclinic phase peaks at room temperature becomes a single peak at high temperature, characteristic of the orthorhombic polymorph) for the samples 20 (<b>a</b>), 37 (<b>b</b>) and 69 (<b>c</b>) in the 12.90–13.25° 2θ regions, while the sample ZSM-5c_15 (<b>d</b>) retains the orthorhombic symmetry throughout the investigated thermal range.</p> Full article ">Figure 4
<p>X-ray powder diffraction patterns collected at high temperature (details of low and high 2θ angles) for samples ZSM-5c_15 (<b>a</b>,<b>b</b>), ZSM-5c_20 (<b>c</b>,<b>d</b>), ZSM-5c_37 (<b>e</b>,<b>f</b>) and ZSM-5c_69 (<b>g</b>,<b>h</b>).</p> Full article ">Figure 4 Cont.
<p>X-ray powder diffraction patterns collected at high temperature (details of low and high 2θ angles) for samples ZSM-5c_15 (<b>a</b>,<b>b</b>), ZSM-5c_20 (<b>c</b>,<b>d</b>), ZSM-5c_37 (<b>e</b>,<b>f</b>) and ZSM-5c_69 (<b>g</b>,<b>h</b>).</p> Full article ">Figure 5
<p>Temperature dependence evolution of the normalized lattice parameters ((<b>a</b>) a/a0, (<b>b</b>) b/b0 and (<b>c</b>) c/c0) for the investigated ZSM-5c samples.</p> Full article ">Figure 5 Cont.
<p>Temperature dependence evolution of the normalized lattice parameters ((<b>a</b>) a/a0, (<b>b</b>) b/b0 and (<b>c</b>) c/c0) for the investigated ZSM-5c samples.</p> Full article ">Figure 6
<p>Evolution of the unit cell volume upon heating of the investigated ZSM-5c samples.</p> Full article ">Figure 7
<p>Evolution of ADPs parameters during heating.</p> Full article ">Figure 8
<p>Evolution of the ellipticity parameter with temperature for the four ZSM-5c samples. (<b>a</b>) ZSM5C_15; (<b>b</b>) ZSM5C_20, (<b>c</b>) ZSM5C_37 and (<b>d</b>) ZSM5C_69.</p> Full article ">Figure 9
<p>Evolution of the density parameter with temperature for the four ZSM-5c samples.</p> Full article ">
12 pages, 4574 KiB  
Article
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 1216
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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<p>The dilatometer used to measure strain during the sintering process.</p> Full article ">Figure 2
<p>Schematics of the three different experimental setups. Observe that the time is not to scale.</p> Full article ">Figure 3
<p>The three experimental strain curves as a function of time after 450 °C was reached.</p> Full article ">Figure 4
<p>Strain rate curves corresponding to the strain curves in <a href="#crystals-13-00978-f003" class="html-fig">Figure 3</a>.</p> Full article ">Figure 5
<p>Experimental results and optimisation of the reference experiment.</p> Full article ">Figure 6
<p>Experimental results and optimisation of the separated debinding step—aired experiment.</p> Full article ">
11 pages, 35785 KiB  
Article
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
Cited by 1 | Viewed by 1552
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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<p>Appearance of the agate samples.</p> Full article ">Figure 2
<p>Microscopic characteristics of the agate samples in 15×: (<b>a</b>,<b>b</b>) are dark minerals in AG-1 and AG-2; (<b>c</b>) is a very fine equigranular structure in AR-1; (<b>d</b>) is granular structure in AR-2; (<b>e</b>) is the invasion of AR-3; (<b>f</b>) is the point inclusion in AY-1; (<b>g</b>) is vein-like intrusion in AY-2; (<b>h</b>) is red dip at the edge of AY-3.</p> Full article ">Figure 3
<p>FTIR spectra of the Moqi agate.</p> Full article ">Figure 4
<p>Raman spectra of the Moqi agate samples. The eight samples were divided into three groups according to color, and the corresponding positions were tested by Raman spectroscopy.</p> Full article ">Figure 5
<p>Raman spectra of red brown part of AR-3 (<b>a</b>,<b>b</b>) and Raman spectra of the yellow part of AY-1 (<b>c</b>).</p> Full article ">Figure 6
<p>X-ray diffraction patterns of agate with three colors.</p> Full article ">Figure 7
<p>X-ray diffraction pattern of natural white quartz with a crystallinity index of 10 in the 2θ range of 67–69°.</p> Full article ">Figure 8
<p>SEM (<b>a</b>) and EDS (<b>b</b>) of AG-1 plate edge.</p> Full article ">Figure 9
<p>UV–visible spectra of the agate.</p> Full article ">
9 pages, 2315 KiB  
Review
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 4 | Viewed by 3552
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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<p>The successful introduce of dopamine chemistry in an energetic system as reported firstly: compact core–shell structure for every single energetic crystal with highly enhanced thermal stability. Reprinted with permission from Ref. [<a href="#B26-crystals-13-00976" class="html-bibr">26</a>]. 2017, Elsevier.</p> Full article ">Figure 2
<p>(<b>A</b>) Preparation of core-shell structured pTATB and the supposed interaction between PDA, TATB, and the fluoropolymer. (<b>B</b>) Topographical AFM images of PDA films deposited on the TATB crystal for (<b>a</b>) 0 h, (<b>b</b>) 3 h, (<b>c</b>) 6 h, (<b>d</b>) 12 h, (<b>e</b>) 24 h, (<b>f</b>) 48 h. (<b>C</b>) Stress-strain curves of PBX composites prepared from the abovementioned TATB. Reprinted with permission from Ref. [<a href="#B32-crystals-13-00976" class="html-bibr">32</a>]. 2012, Royal Society of Chemistry.</p> Full article ">Figure 3
<p>(<b>a</b>) A picture of a mussel, showing the strong adhesive of the byssus. (<b>b</b>) The molecular structure of dopamine. (<b>c</b>) The structure of polydopamine film binding on the particle surface. (<b>d</b>) The polymerization of dopamine. (<b>e</b>) Schematic description of the fabrication of n-Al@PDA@CuO MICs constructed by dopamine-nucleated crystal growth. Reprinted with permission from Ref. [<a href="#B48-crystals-13-00976" class="html-bibr">48</a>]. 2019, Elsevier.</p> Full article ">
14 pages, 5163 KiB  
Article
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
Cited by 2 | Viewed by 1479
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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<p>XRD patterns: pure CoAl<sub>2</sub>O<sub>4</sub>, pure CeO<sub>2</sub>, and CeO<sub>2</sub>-CoAl<sub>2</sub>O<sub>4</sub> heterostructures.</p> Full article ">Figure 2
<p>(<b>a</b>,<b>b</b>) Scanning electron microscopy (SEM) images of CoAl<sub>2</sub>O<sub>4</sub> and CeO<sub>2</sub>-CoAl<sub>2</sub>O<sub>4</sub>, and (<b>c</b>,<b>d</b>) high-resolution transmission electron microscopy (HR-TEM) images, CeO<sub>2</sub>-CoAl<sub>2</sub>O<sub>4</sub> sample.</p> Full article ">Figure 3
<p>(<b>a</b>–<b>f</b>) The elemental mapping and EDS analysis of CeO<sub>2</sub>-CoAl<sub>2</sub>O<sub>4</sub> sample using HR-TEM.</p> Full article ">Figure 4
<p>(<b>a</b>–<b>d</b>) XPS survey spectra and O1s spectra of CoAl<sub>2</sub>O<sub>4</sub>, CeO<sub>2</sub>, CeO<sub>2</sub>-CoAl<sub>2</sub>O<sub>4</sub> samples.</p> Full article ">Figure 5
<p>(<b>a</b>) I-V and I-P characteristics of CeO<sub>2</sub>-CoAl<sub>2</sub>O<sub>4</sub> fuel cell devices, (<b>b</b>) I-V and I-P characteristics of CeO<sub>2</sub> and CoAl<sub>2</sub>O<sub>4</sub> fuel cell devices, (<b>c</b>) EIS analysis of CeO<sub>2</sub>-CoAl<sub>2</sub>O<sub>4</sub> fuel cell device, (<b>d</b>) Ionic conductivity analysis of CeO<sub>2</sub>-CoAl<sub>2</sub>O<sub>4</sub> fabricated device.</p> Full article ">Figure 6
<p>(<b>a</b>–<b>c</b>) EIS analysis of CeO<sub>2</sub>-CoAl<sub>2</sub>O<sub>4</sub> in configuration of Pt/CeO<sub>2</sub>-CoAl<sub>2</sub>O<sub>4</sub>/Pt in air and 5% H<sub>2</sub>/95%Ar at 450 °C–550 °C and (<b>d</b>) the cross-sectional SEM image of fuel cell with configurations of Ni<sub>0.80</sub>Co<sub>0.15</sub>Al<sub>0.05</sub>LiO<sub>2</sub>/CeO<sub>2</sub>-CoAl<sub>2</sub>O<sub>4</sub>/Ni<sub>0.80</sub>Co<sub>0.15</sub>Al<sub>0.05</sub>LiO<sub>2</sub> after fuel cell performance measurements.</p> Full article ">Figure 7
<p>(<b>a</b>,<b>b</b>) Optical bandgap of CeO<sub>2</sub> and CoAl<sub>2</sub>O<sub>4</sub>, (<b>c</b>,<b>d</b>) Vb maxima of synthesized CeO<sub>2</sub> and CoAl<sub>2</sub>O<sub>4</sub> samples.</p> Full article ">Figure 8
<p>(<b>a</b>,<b>b</b>) The schematic diagram of fuel cell based on CeO<sub>2</sub>-CoAl<sub>2</sub>O<sub>4</sub> electrolyte and illustration of p-n junction mechanism in CeO<sub>2</sub>-CoAl<sub>2</sub>O<sub>4</sub>. (<b>c</b>) Ag/CeO<sub>2</sub>-CoAl<sub>2</sub>O<sub>4</sub>/Ag layered structure under N<sub>2</sub> gas atmosphere at 550 °C.</p> Full article ">
16 pages, 5607 KiB  
Article
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 1211
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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<p>Chemical diagram for <span class="html-italic">N</span><sup>4</sup>-(4-methylphenyl)-<span class="html-italic">N</span><sup>3</sup>-phenyl-1<span class="html-italic">H</span>-pyrazolo[3,4-<span class="html-italic">d</span>]pyrimidine-3,4-diamine (<b>1</b>).</p> Full article ">Figure 2
<p>The molecular structures in the: (<b>a</b>) <b>α</b>-polymorph and (<b>b</b>) <b>β</b>-polymorph of <b>1</b> showing atom labelling schemes and anisotropic displacement parameters at the 70% probability level.</p> Full article ">Figure 3
<p>The potential energy profile upon the variation of the C4–N6–C12–C13 torsion angle for <b>opt-1</b>.</p> Full article ">Figure 4
<p>Structural overlay between the molecules in the <b>α</b>-polymorph (red image), <b>β</b>-polymorph (blue) and optimised (<b>opt-1</b>; green). The molecules are overlapped such that the pyrazolopyrimidine fragments are coincident.</p> Full article ">Figure 5
<p>A view of the unit-cell contents for the <b>α</b>-form in projection down the <span class="html-italic">b</span>-axis. The phenylamino-N–H···N(pyrazolyl), pyrazolyl-N–H···N(pyrimidyl) and C–H···π contacts are shown as orange, blue and purple dashed lines, respectively. Non-participating H atoms have been omitted.</p> Full article ">Figure 6
<p>Supramolecular association in the crystal of the <b>β</b>-form: (<b>a</b>) detail of the phenylamino-N–H···N(pyrazolyl) and pyrazolyl-N–H···N(pyrimidyl) hydrogen bonds, shown as orange and blue dashed lines, respectively, (<b>b</b>) detail of the H···π and π···π contacts shown as purple and pink dashed lines, respectively, and (<b>c</b>) a view of the unit-cell contents shown in projection down the <span class="html-italic">b</span>-axis. Non-participating H atoms have been omitted.</p> Full article ">Figure 7
<p>A comparison of the molecular packing between the <b>α</b>- (red image) and <b>β</b>- (blue) polymorphs, showing two pairs of molecules (highlighted as bold tubes) out of 15 fit within the 20% tolerance criterion.</p> Full article ">Figure 8
<p>The two views of the <span class="html-italic">d</span><sub>norm</sub>-surface mappings for <b>α</b>- (<b>top</b>) and <b>β</b>- (<b>bottom</b>) polymorphs within the range −0.0815 to 1.0665 arbitrary units, highlighting close contacts as red dots on the surfaces with their intensity relative to the contact distance.</p> Full article ">Figure 9
<p>The two views of electrostatic potential mapped onto the Hirshfeld surfaces for <b>α</b>- (<b>top</b>) and <b>β</b>- (<b>bottom</b>) polymorphs within the range −0.0312 to 0.0362 atomic units, highlighting the charge complementarity between the corresponding point-to-point interactions identified through the Hirshfeld surface analysis.</p> Full article ">Figure 10
<p>The Hirshfeld surface mapped with curvedness (property range: −4.0 to +0.4 arbitrary units) showing the shape complementarity between (<b>a</b>) two pyrazolopyrimidine fragments connected by C13–H13···π(C5) contact in the <b>α</b>-polymorph and (<b>b</b>) the pyrazolopyrimidine and <span class="html-italic">p</span>-toluidine fragments connected by C7–H7···π(C16) in the <b>β</b>-polymorph.</p> Full article ">Figure 11
<p>The overall two-dimensional fingerprint and decomposed plots delineated into the major contacts for <b>α</b>- (<b>top</b>) and <b>β</b>- (<b>bottom</b>) polymorphs.</p> Full article ">Figure 12
<p>Perspective views of the electrostatic energy (red), dispersion force (green) and overall energy frameworks (blue) for the <b>α</b>- (<b>top</b>) and <b>β</b>- (<b>bottom</b>) polymorphs. The cylindrical radius is proportional to the relative strength of the corresponding energies and they were adjusted to the same scale factor of 150 with a cut-off value of 8 kJ/mol within a 2 × 2 × 2 unit-cells.</p> Full article ">Scheme 1
<p>Synthesis of <span class="html-italic">N</span><sup>4</sup>-(4-methylphenyl)-<span class="html-italic">N</span><sup>3</sup>-phenyl-1<span class="html-italic">H</span>-pyrazolo[3,4-<span class="html-italic">d</span>]pyrimidine-3,4-diamine (<b>1</b>).</p> Full article ">
14 pages, 5959 KiB  
Review
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
Cited by 1 | Viewed by 1819
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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<p>Schematic structural model of typical ABX<sub>3</sub> [<a href="#B13-crystals-13-00973" class="html-bibr">13</a>]. Reprinted with permission from Ref. [<a href="#B13-crystals-13-00973" class="html-bibr">13</a>]. Copyright 2020, John Wiley and Sons.</p> Full article ">Figure 2
<p>Schematic illustrations of two typical imaging modes of electron microscopy (<b>a</b>) TEM (<b>b</b>) STEM [<a href="#B13-crystals-13-00973" class="html-bibr">13</a>]. Reprinted with permission from Ref. [<a href="#B13-crystals-13-00973" class="html-bibr">13</a>]. Copyright 2020, John Wiley and Sons.</p> Full article ">Figure 3
<p>(<b>a</b>) Electron beam irradiation damage observed in free-standing MAPbI<sub>3</sub> films [<a href="#B25-crystals-13-00973" class="html-bibr">25</a>]. Reprinted with permission from Ref. [<a href="#B25-crystals-13-00973" class="html-bibr">25</a>]. Copyright 2018, Elsevier. (<b>b</b>) Time-series of TEM images on MAPbI<sub>3</sub> single crystal showing the electron beam damage from 0 to 50 s, where bubble-like morphology (colored arrows) emerged and grew [<a href="#B26-crystals-13-00973" class="html-bibr">26</a>]. Reprinted with permission from Ref. [<a href="#B26-crystals-13-00973" class="html-bibr">26</a>]. Copyright 2020, IOP Publishing on behalf of the Japan Society of Applied Physics (JSAP).</p> Full article ">Figure 4
<p>Generality of decomposition pathway for MAPbI<sub>3</sub> and MAPbBr<sub>3</sub> [<a href="#B30-crystals-13-00973" class="html-bibr">30</a>]. Reprinted with permission from Ref. [<a href="#B30-crystals-13-00973" class="html-bibr">30</a>]. Copyright 2020, John Wiley and Sons. (<b>a</b>–<b>d</b>) Consecutive SAED patterns during the decomposition of MAPbI<sub>3</sub>; (<b>e</b>) The intensity line profiles extracted along the white arrow in (<b>a</b>); (<b>f</b>) The HAADF−STEM image of the decomposed product PbI<sub>2</sub> along the [<math display="inline"><semantics> <mover accent="true"> <mn>4</mn> <mo>¯</mo> </mover> </semantics></math>41] zone axis; (<b>g</b>–<b>j</b>) Time−series SAED patterns during the decomposition of MAPbBr<sub>3</sub>; (<b>k</b>) The structure line profiles obtained from time−series SAED patterns along the white arrow in (<b>g</b>); (<b>l</b>) HRTEM image of the decomposed product PbBr<sub>2</sub>; (<b>m</b>–<b>p</b>) The structure illustrations for decomposition from MAPbI<sub>3</sub> to PbI<sub>2</sub> and MAPbBr<sub>3</sub> to PbBr<sub>2</sub>. All figures have been permitted to be reprinted by original journals.</p> Full article ">Figure 5
<p>Phases characterization of MAPbI<sub>3</sub> under different temperature. Atomistic structures of (<b>a</b>) orthorhombic (below −111 °C), (<b>b</b>) tetragonal (−111 to 54 °C) and (<b>c</b>) cubic (over 54 °C) MAPbI<sub>3</sub>. (<b>d</b>–<b>f</b>) SAED patterns of MAPbI<sub>3</sub> at −180, 25, 90 °C. (<b>g</b>–<b>i</b>) The corresponding simulated SAED patterns along the [100] direction of orthorhombic and tetragonal MAPbI<sub>3</sub> and [110] direction of cubic MAPbI<sub>3</sub> [<a href="#B31-crystals-13-00973" class="html-bibr">31</a>]. The inside frames are selected area to compare whether the SAED patterns match to the simulated diffraction patterns. Reprinted with permission from Ref. [<a href="#B31-crystals-13-00973" class="html-bibr">31</a>]. Copyright 2020, Elsevier.</p> Full article ">Figure 6
<p>Simulated electron diffraction (ED) patterns of tetragonal MAPbI<sub>3</sub> and hexagonal PbI<sub>2</sub>. (<b>a</b>) MAPbI<sub>3</sub> along [110] axis zone. (<b>b</b>) PbI<sub>2</sub> along [44<math display="inline"><semantics> <mover accent="true"> <mn>1</mn> <mo>¯</mo> </mover> </semantics></math>] zone axis. (<b>c</b>) MAPbI<sub>3</sub> along [101] axis zone. (<b>d</b>) PbI<sub>2</sub> along [8101] zone axis. (<b>e</b>) MAPbI<sub>3</sub> along [2<math display="inline"><semantics> <mover accent="true"> <mn>0</mn> <mo>¯</mo> </mover> </semantics></math>1] zone axis. (<b>f</b>) PbI<sub>2</sub> along [88<math display="inline"><semantics> <mover accent="true"> <mn>1</mn> <mo>¯</mo> </mover> </semantics></math>] zone axis. (<b>g</b>) MAPbI<sub>3</sub> along [1<math display="inline"><semantics> <mover accent="true"> <mn>2</mn> <mo>¯</mo> </mover> </semantics></math>0] zone axis. (<b>h</b>) PbI<sub>2</sub> along [4<math display="inline"><semantics> <mover accent="true"> <mn>1</mn> <mo>¯</mo> </mover> </semantics></math>1] zone axis. Reprinted with permission from Ref. [<a href="#B34-crystals-13-00973" class="html-bibr">34</a>]. Copyright 2020, MDPI.</p> Full article ">Figure 7
<p>Analysis of ignoring the absent crystal planes. (<b>a</b>) HRTEM image of pseudo MAPbI<sub>3</sub> along [001] zone axis, (11<math display="inline"><semantics> <mover accent="true"> <mn>0</mn> <mo>¯</mo> </mover> </semantics></math>), (110) planes are missing. (<b>b</b>) FFT of (<b>a</b>). (<b>c</b>) Simulated ED pattern of corrected PbI<sub>2</sub> phase along [44<math display="inline"><semantics> <mover accent="true"> <mn>1</mn> <mo>¯</mo> </mover> </semantics></math>] zone axis (<b>d</b>) HRTEM image of intrinsic MAPbI<sub>3</sub> along [001] axis zone. (<b>e</b>) Fast Fourier Transform (FFT) of (<b>d</b>). (<b>f</b>) Simulated ED pattern of intrinsic MAPbI<sub>3</sub> along [001] zone axis [<a href="#B44-crystals-13-00973" class="html-bibr">44</a>]. Reprinted with permission from Ref. [<a href="#B44-crystals-13-00973" class="html-bibr">44</a>]. Copyright 2021, John Wiley and Sons.</p> Full article ">Figure 8
<p>HRTEM image, FFT and simulated ED patterns of intrinsic (<b>d</b>–<b>f</b>), pseudo (<b>a</b>–<b>c</b>) MAPbI<sub>3</sub> along [<math display="inline"><semantics> <mover accent="true"> <mn>2</mn> <mo>¯</mo> </mover> </semantics></math>01] zone axis were also be analysed. The newly added annotations in reproduced HRTEM images were marked by yellow font [<a href="#B45-crystals-13-00973" class="html-bibr">45</a>]. Reprinted with permission from Ref. [<a href="#B45-crystals-13-00973" class="html-bibr">45</a>]. Copyright 2020, Elsevier.</p> Full article ">Figure 9
<p>Atomic-level STEM images of FAPbI<sub>3</sub>. (<b>a</b>) Partially FA-depleted perovskite; (<b>b</b>) Coherent PbI<sub>2</sub>: FAPbI<sub>3</sub> interface; (<b>c</b>) Sharp FAPbI<sub>3</sub> grain boundaries; (<b>d</b>) Stacking fault and dislocation [<a href="#B51-crystals-13-00973" class="html-bibr">51</a>]. Reprinted with permission from Ref. [<a href="#B51-crystals-13-00973" class="html-bibr">51</a>]. Copyright 2020, The American Association for the Advancement of Science.</p> Full article ">
21 pages, 2740 KiB  
Article
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 2 | Viewed by 1401
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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<p>(<b>a</b>) A 3D view of the proposed structure. (<b>b</b>) The 2D schematic of the proposed structure. Insert sub figures (<b>i</b>) and (<b>ii</b>), respectively, show the mode field distribution of area A and area B.</p> Full article ">Figure 2
<p>The 2D schematic of the biosensor structure in the fabrication process.</p> Full article ">Figure 3
<p>(<b>a</b>) The CL curve of the <math display="inline"><semantics> <mrow> <mi>x</mi> <mo>−</mo> </mrow> </semantics></math>polarized mode of area A, and the real part of the effective RI of the core mode and zero-order SPP mode when analyte RI is 1.38. (<b>b</b>–<b>d</b>) The mode field distributions of the proposed biosensor structure simulated with wavelengths, respectively, chosen as 670, 754, and 890 nm.</p> Full article ">Figure 4
<p>(<b>a</b>) The CL curve of the <math display="inline"><semantics> <mrow> <mi>x</mi> <mo>−</mo> </mrow> </semantics></math>polarized mode of area B, and a real part of the effective RI of the core mode and second-order SPP mode when the temperature is 40 °C. (<b>b</b>–<b>d</b>) The mode field distributions of the proposed biosensor structure simulated with wavelengths, respectively, chosen as 1120, 1250, and 1470 nm.</p> Full article ">Figure 5
<p>The CL curve of the <math display="inline"><semantics> <mrow> <mi>x</mi> <mo>−</mo> </mrow> </semantics></math>polarized mode of area A with <math display="inline"><semantics> <msub> <mi>τ</mi> <mn>2</mn> </msub> </semantics></math> respectively set as 50, 60, and 70 nm, and analyte RI is 1.36, 1.39, and 1.40.</p> Full article ">Figure 6
<p>The CL curve of the <math display="inline"><semantics> <mrow> <mi>x</mi> <mo>−</mo> </mrow> </semantics></math>polarized mode of area A with <span class="html-italic">a</span> respectively chosen as 1.4, 1.5, and 1.6 <math display="inline"><semantics> <mi mathvariant="sans-serif">μ</mi> </semantics></math>m, and analyte RI is set as 1.36, 1.39, and 1.40.</p> Full article ">Figure 7
<p>The CL curve of the <math display="inline"><semantics> <mrow> <mi>x</mi> <mo>−</mo> </mrow> </semantics></math>polarized mode of area A with <span class="html-italic">b</span> respectively set as 0.5, 0.6, and 0.7 <math display="inline"><semantics> <mi mathvariant="sans-serif">μ</mi> </semantics></math>m, and analyte RI is set as 1.36, 1.39, and 1.40.</p> Full article ">Figure 8
<p>(<b>a</b>) The CL curve of the <math display="inline"><semantics> <mrow> <mi>x</mi> <mo>−</mo> </mrow> </semantics></math>polarized mode of area A with the analyte RI set as 1.36 and the <math display="inline"><semantics> <msub> <mi>θ</mi> <mn>1</mn> </msub> </semantics></math>, respectively, chosen as <math display="inline"><semantics> <mrow> <mo>−</mo> <msup> <mn>10</mn> <mo>∘</mo> </msup> </mrow> </semantics></math>, <math display="inline"><semantics> <msup> <mn>0</mn> <mo>∘</mo> </msup> </semantics></math>, <math display="inline"><semantics> <msup> <mn>15</mn> <mo>∘</mo> </msup> </semantics></math>, and <math display="inline"><semantics> <msup> <mn>30</mn> <mo>∘</mo> </msup> </semantics></math>. (<b>b</b>) The CL curve of the <math display="inline"><semantics> <mrow> <mi>x</mi> <mo>−</mo> </mrow> </semantics></math>polarized mode of area A with the analyte RI set as 1.40 and the <math display="inline"><semantics> <msub> <mi>θ</mi> <mn>1</mn> </msub> </semantics></math>, respectively, chosen as <math display="inline"><semantics> <mrow> <mo>−</mo> <msup> <mn>10</mn> <mo>∘</mo> </msup> </mrow> </semantics></math>, <math display="inline"><semantics> <msup> <mn>0</mn> <mo>∘</mo> </msup> </semantics></math>, <math display="inline"><semantics> <msup> <mn>15</mn> <mo>∘</mo> </msup> </semantics></math>, and <math display="inline"><semantics> <msup> <mn>30</mn> <mo>∘</mo> </msup> </semantics></math>.</p> Full article ">Figure 9
<p>(<b>a</b>) The CL curve of the <math display="inline"><semantics> <mrow> <mi>x</mi> <mo>−</mo> </mrow> </semantics></math>polarized mode of area A with the analyte RI set as 1.36 and <math display="inline"><semantics> <msub> <mi>θ</mi> <mn>2</mn> </msub> </semantics></math>, respectively, set as <math display="inline"><semantics> <mrow> <mo>−</mo> <msup> <mn>10</mn> <mo>∘</mo> </msup> </mrow> </semantics></math>, <math display="inline"><semantics> <msup> <mn>0</mn> <mo>∘</mo> </msup> </semantics></math>, and <math display="inline"><semantics> <msup> <mn>10</mn> <mo>∘</mo> </msup> </semantics></math>. (<b>b</b>) The CL curve of the <math display="inline"><semantics> <mrow> <mi>x</mi> <mo>−</mo> </mrow> </semantics></math>polarized mode of area A with the analyte RI set as 1.40 and <math display="inline"><semantics> <msub> <mi>θ</mi> <mn>2</mn> </msub> </semantics></math>, respectively, set as <math display="inline"><semantics> <mrow> <mo>−</mo> <msup> <mn>10</mn> <mo>∘</mo> </msup> </mrow> </semantics></math>, <math display="inline"><semantics> <msup> <mn>0</mn> <mo>∘</mo> </msup> </semantics></math>, and <math display="inline"><semantics> <msup> <mn>10</mn> <mo>∘</mo> </msup> </semantics></math>.</p> Full article ">Figure 10
<p>The CL curve of the <math display="inline"><semantics> <mrow> <mi>x</mi> <mo>−</mo> </mrow> </semantics></math>polarized mode of area B with <math display="inline"><semantics> <msub> <mi>d</mi> <mn>3</mn> </msub> </semantics></math> respectively chosen as 2.0, 2.2, and 2.4 <math display="inline"><semantics> <mi mathvariant="sans-serif">μ</mi> </semantics></math>m, and with temperature <span class="html-italic">T</span> is 0 and 50 °C.</p> Full article ">Figure 11
<p>The CL curve of the <math display="inline"><semantics> <mrow> <mi>x</mi> <mo>−</mo> </mrow> </semantics></math>polarized mode of area B with <math display="inline"><semantics> <msub> <mi>d</mi> <mn>4</mn> </msub> </semantics></math> respectively chosen as 1.6, 1.8, and 2.0 <math display="inline"><semantics> <mi mathvariant="sans-serif">μ</mi> </semantics></math>m, and <span class="html-italic">T</span> is 0 and 50 °C.</p> Full article ">Figure 12
<p>The CL curve of the <math display="inline"><semantics> <mrow> <mi>x</mi> <mo>−</mo> </mrow> </semantics></math>polarized mode of area B with <math display="inline"><semantics> <msub> <mi>τ</mi> <mn>1</mn> </msub> </semantics></math> respectively chosen as 40, 50, 60, and 70 nm, and <span class="html-italic">T</span> is 0 and 50 °C.</p> Full article ">Figure 13
<p>The CL curve of the <math display="inline"><semantics> <mrow> <mi>x</mi> <mo>−</mo> </mrow> </semantics></math>polarized mode of area B with <math display="inline"><semantics> <msub> <mi>d</mi> <mn>1</mn> </msub> </semantics></math> respectively chosen as 1.4, 1.6, and 1.8 <math display="inline"><semantics> <mi mathvariant="sans-serif">μ</mi> </semantics></math>m, and <span class="html-italic">T</span> is 0 and 50 °C.</p> Full article ">Figure 14
<p>The CL curve of the <math display="inline"><semantics> <mrow> <mi>x</mi> <mo>−</mo> </mrow> </semantics></math>polarized mode of area B with <math display="inline"><semantics> <msub> <mi>d</mi> <mn>2</mn> </msub> </semantics></math> respectively chosen as 1.8, 2.0, and 2.2 <math display="inline"><semantics> <mi mathvariant="sans-serif">μ</mi> </semantics></math>m, and <span class="html-italic">T</span> is 0 and 50 °C.</p> Full article ">Figure 15
<p>The CL curve of the <math display="inline"><semantics> <mrow> <mi>x</mi> <mo>−</mo> </mrow> </semantics></math>polarized mode of area A with <span class="html-italic">b</span> respectively chosen as 0.75 and 0.78 <math display="inline"><semantics> <mi mathvariant="sans-serif">μ</mi> </semantics></math>m, <math display="inline"><semantics> <msub> <mi>τ</mi> <mn>2</mn> </msub> </semantics></math> and <span class="html-italic">a</span> set as 60 nm and 1.5 <math display="inline"><semantics> <mi mathvariant="sans-serif">μ</mi> </semantics></math>m, and analyte RI set as 1.36, 1.39, and 1.40.</p> Full article ">Figure 16
<p>(<b>a</b>) The CL curve of the <math display="inline"><semantics> <mrow> <mi>x</mi> <mo>−</mo> </mrow> </semantics></math>polarized mode of area A with a variation in the RI from 1.35 to 1.41. (<b>b</b>) Variation in the <math display="inline"><semantics> <msub> <mi>λ</mi> <mrow> <mi>S</mi> <mi>P</mi> <mi>R</mi> </mrow> </msub> </semantics></math> value of the <math display="inline"><semantics> <mrow> <mi>x</mi> <mo>−</mo> </mrow> </semantics></math>polarized mode of area A corresponding to the RI and a fitting result.</p> Full article ">Figure 17
<p>(<b>a</b>) The CL curve of the <math display="inline"><semantics> <mrow> <mi>x</mi> <mo>−</mo> </mrow> </semantics></math>polarized mode of area B with a variation in <span class="html-italic">T</span> from 0 to 60 °C. (<b>b</b>) Variation in <math display="inline"><semantics> <msub> <mi>λ</mi> <mrow> <mi>S</mi> <mi>P</mi> <mi>R</mi> </mrow> </msub> </semantics></math> value of the <math display="inline"><semantics> <mrow> <mi>x</mi> <mo>−</mo> </mrow> </semantics></math>polarized mode of area B with temperature and a fitting result.</p> Full article ">
8 pages, 2009 KiB  
Article
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 1634
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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<p>(<b>a</b>) A photograph of the floating zone crystal of hexagonal DyInO<sub>3</sub>. (<b>b</b>) Crystal structure from refinement. (<b>c</b>) Top view of one layer. (<b>d</b>) Room temperature XRD patterns taken on crushed crystals grown using different In<sub>2</sub>O<sub>3</sub> stoichiometry and the Rietveld fitting of the hexagonal phase.</p> Full article ">Figure 2
<p>(<b>a</b>,<b>b</b>) Ferroelectric domain configuration of a 2 °C/h cooled crystal (<b>a</b>) and a 50 °C/h cooled crystal (<b>b</b>) revealed by chemical etching. (<b>c</b>) The P versus E hysteresis loop at room temperature measured using the PUND method.</p> Full article ">Figure 3
<p>(<b>a</b>) DC magnetic susceptibility (solid lines with spheres) and inverse susceptibility versus temperature (solid lines) as low as 1.8 K. (<b>b</b>) AC magnetic susceptibility versus temperature as low as 0.1 K. (<b>c</b>) Magnetization versus field at 1.8 K. (<b>d</b>) Derivative magnetization versus field at 1.8 K. The vertical dashed line denotes the anomaly at around 1 T.</p> Full article ">Figure 4
<p>(<b>a</b>) Heat capacity and Debye fitting at 0 T. (<b>b</b>) Magnetic heat capacity over temperature as a function of temperature at 0 T, 3 T, 6 T, and 9 T. (<b>c</b>) Magnetic entropy as a function of temperature at 0 T. The horizontal dashed lines show theoretical magnetic entropy values of S = 1/2 (Rln2) and S = 1 (Rln3).</p> Full article ">
10 pages, 3163 KiB  
Article
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 1588
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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<p>Central and lateral cores distribution of neodymium-doped yttrium aluminum garnet (Nd:YAG) crystals grown at different rotation rates; (<b>a</b>) the rotation rates are 16–13 rpm and (<b>b</b>) 18–15 rpm.</p> Full article ">Figure 2
<p>Growth interface of Nd:YAG crystals prepared at the same crystal growth speeds and different temperatures; (<b>a</b>) the temperature gradients across the crucible mouth of ~1 °C/mm and (<b>b</b>) 15 °C/mm.</p> Full article ">Figure 3
<p>Interface inversion of the crystal during the late stage of the shoulder growth.</p> Full article ">Figure 4
<p>Interface inversion of the crystal growth during the late stage of the equal-diameter phase.</p> Full article ">Figure 5
<p>(<b>a</b>) Stress region generated by the central and lateral cores of the crystal observed using a stress meter. (<b>b</b>) Large petal-shaped central core of the crystal. (<b>c</b>) Large central and lateral cores of the crystal observed under red parallel light.</p> Full article ">Figure 6
<p>Distribution of the central core of the Nd:YAG crystal grown in the &lt;111&gt; direction after adjusting the temperature field, as observed by an orthogonal polarizing system.</p> Full article ">Figure 7
<p>Lateral core of an Nd:YAG crystal observed under red parallel light (<b>a</b>) before and (<b>b</b>) after improving the temperature gradient.</p> Full article ">
21 pages, 14446 KiB  
Article
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 3 | Viewed by 1231
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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<p>Third degree polynomial interpolation for two hysteresis loops (axial and shear).</p> Full article ">Figure 2
<p>(<b>a</b>) specimen used on the experiments; (<b>b</b>) specimen used on numerical simulations.</p> Full article ">Figure 3
<p>Loading paths performed in strain control: Case 1—PT, Case 2—PS, Case 3—PP30, Case 4—PP45, Case 5—PP60, and Case 6—OP45.</p> Full article ">Figure 4
<p>Mesh model representation of the specimen used on numerical simulations.</p> Full article ">Figure 5
<p>Triangular displacement amplitude.</p> Full article ">Figure 6
<p>Data flow of the hypo-strain phenomenological implementation on ABAQUS.</p> Full article ">Figure 7
<p>Armstrong–Frederick plasticity model calibration, correlation factor <span class="html-italic">R</span><sup>2</sup> = 0.92.</p> Full article ">Figure 8
<p>Correlation between estimations and experiments for pure axial loading with: (<b>a</b>) 0.5% of axial strain amplitude, and (<b>b</b>) 1.2% of axial strain amplitude.</p> Full article ">Figure 9
<p>Correlation between estimations and experiments for pure shear loading with: (<b>a</b>) 0.4% of shear strain amplitude, (<b>b</b>) 0.8% of shear strain amplitude.</p> Full article ">Figure 10
<p>Correlation between estimations and experiments for multiaxial proportional loadings with a strain amplitude ratio equal to 30° (<b>a</b>,<b>b</b>): strain magnitude of 0.4%; (<b>c</b>,<b>d</b>): strain magnitude of 0.6%; (<b>e</b>,<b>f</b>): strain magnitude of 1%.</p> Full article ">Figure 11
<p>Correlation between estimations and experiments for multiaxial proportional loadings with a strain amplitude ratio equal to 45° (<b>a</b>,<b>b</b>): strain magnitude of 0.4%; (<b>c</b>,<b>d</b>): strain magnitude of 0.6%; (<b>e</b>,<b>f</b>): strain magnitude of 1%.</p> Full article ">Figure 12
<p>Correlation between estimations and experiments for multiaxial proportional loadings with a strain amplitude ratio equal to 60° (<b>a</b>,<b>b</b>): strain magnitude of 0.4%; (<b>c</b>,<b>d</b>): strain magnitude of 0.6%; (<b>e</b>,<b>f</b>): strain magnitude of 1%.</p> Full article ">Figure 13
<p>Correlation between estimations and experiments for 90° out-of-phase loadings with a strain amplitude ratio equal to 45° (<b>a</b>,<b>b</b>): strain magnitude of 0.83% and (<b>c</b>,<b>d</b>): strain magnitude of 1.14%.</p> Full article ">Figure 14
<p>Stresses distributions of the phenomenological hypo-strain model implemented in Abaqus, for the tension–torsion loading—Case PP30 (<b>a</b>) cutting view image of the specimen; (<b>b</b>) and (<b>c</b>): axial stress distribution along the thickness of the specimen during tension; (<b>d</b>,<b>e</b>): shear stress distribution along the thickness of the specimen during torsion.</p> Full article ">
16 pages, 2972 KiB  
Review
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 4 | Viewed by 2835
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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<p>(<b>a</b>) Schematic diagram for corrosion of austenitic steel in LBE with low oxygen concentration. (1) Alloying elements begin to dissolve in the LBE. (2) LBE begins to penetrate and continues to dissolve. (3) Infiltration of Pb–Bi particles deeper into the substrate. (<b>b</b>) Diagram of corrosion in high-oxygen-concentration LBE. (1) A poorly protective oxide layer (Cr, Fe)Ox is formed. (2) The oxide layer is destroyed due to stress. (3) Oxidation continues on the new surface. Reprinted with permission from Ref. [<a href="#B46-crystals-13-00968" class="html-bibr">46</a>]. 2022, Serag, E.</p> Full article ">Figure 2
<p>Effect of time on the SEM morphology of T91 oxide film at (<b>a</b>) 200 h, (<b>b</b>) 2000 h, (<b>c</b>) 4000 h, and (<b>d</b>) 8000 h. Reprinted with permission from Ref. [<a href="#B5-crystals-13-00968" class="html-bibr">5</a>]. 2022, Zhu, Z.</p> Full article ">Figure 3
<p>(<b>a</b>–<b>c</b>) BSE images of LBE flowing vertically through T91 at a rate of 5 m/s for 1000 h and (<b>d</b>) BSE images of the enlarged region in (<b>b</b>), with EDS mapping and line scan analysis. Reprinted with permission from Ref. [<a href="#B28-crystals-13-00968" class="html-bibr">28</a>]. 2021, Li, C.</p> Full article ">Figure 4
<p>Several cracks in T91 after tensile testing in LBE media. Reprinted with permission from Ref. [<a href="#B81-crystals-13-00968" class="html-bibr">81</a>]. 2019, Patricie Halodová.</p> Full article ">Figure 5
<p>Schematic diagram of the CORRIDA device for testing steel in flowing oxygenated LBE. Reprinted with permission from Ref. [<a href="#B106-crystals-13-00968" class="html-bibr">106</a>]. 2011, L. Brissonneau.</p> Full article ">
16 pages, 3685 KiB  
Article
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 5 | Viewed by 2072
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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<p>TGA curves of reference Ca oxalate and root, trunk, and bark of <span class="html-italic">Vitis vinifera</span>.</p> Full article ">Figure 2
<p>XRD patterns of the washed and milled samples of grapevine trunk, root, and bark, and of the purchased Ca oxalate monohydrate (blue line). The black vertical lines correspond to the XRD peaks of Ca oxalate monohydrate (International Centre for Diffraction Data (ICDD) Ref.# 04-011-6806).</p> Full article ">Figure 3
<p>XRD patterns of the washed and milled grapevine bark and its calcination products generated at 250 °C, 300 °C, and 350 °C.</p> Full article ">Figure 4
<p>Washed grapevine root: (<b>a</b>) SEM image showing a typical overview with various mineral grains embedded in the organic plant structure; white rectangles outline the areas shown in (<b>c</b>,<b>e</b>); (<b>b</b>) X-ray distribution maps of Si, Ca, and Al superimposed onto the SEM image shown in (<b>a</b>) and visualizing different types of minerals: blue = quartz; magenta = Ca oxalate, and green = minerals containing both Si and Al; (<b>c</b>) detail of (<b>a</b>) showing a needle-shaped Ca oxalate crystal, consisting of several needles, and an isometric Si–Al-containing mineral, whose shape suggests that it represents a clay mineral from the soil; (<b>d</b>) EDX spectrum revealing the presence of the most abundant elements in the area mapped in (<b>b</b>); (<b>e</b>) detail of (<b>a</b>) showing two isometric Ca oxalate crystals and two quartz crystals; (<b>f</b>) SEM image of two acicular, twinned Ca oxalate crystals.</p> Full article ">Figure 5
<p>Washed grapevine bark: (<b>a</b>,<b>c</b>,<b>d</b>) SEM images of Ca oxalate crystals; (<b>b</b>) X-ray distribution map of Ca superimposed onto a corresponding SEM image and documenting the presence of Ca oxalate crystals, including those displayed in (<b>a</b>,<b>c</b>).</p> Full article ">Figure 6
<p>SEM images of grapevine bark calcined at different temperatures: (<b>a</b>,<b>b</b>) bark calcined at 250 °C; (<b>c</b>,<b>d</b>) bark calcined at 300 °C; (<b>e</b>,<b>f</b>) bark calcined at 350 °C.</p> Full article ">Figure 7
<p><sup>13</sup>C CPMAS NMR spectra of the purchased Ca oxalate monohydrate (COM) bark from the grapevine studied here, and of purchased lignocellulosic polymers.</p> Full article ">Figure 8
<p>Detail of the <sup>13</sup>C-NMR MAS + DEC spectra showing the oxalate region (between 160 and 180 ppm) for the original grapevine bark and the residual chars after calcination at various temperatures (entire spectra shown in <a href="#app1-crystals-13-00967" class="html-app">Figure S5</a>).</p> Full article ">
11 pages, 4616 KiB  
Article
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
Cited by 1 | Viewed by 1626
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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<p>(<b>a</b>) TEM micrographs of the as-prepared WOx NPs. (<b>b</b>) Ultraviolet–visible absorption spectrum of WOx film. The inset shows a plot of the absorption coefficient vs. the photon energy for the determination of the WOx optical band gap. (<b>c</b>) XRD patterns of WOx films (annealed at 120 °C and 300 °C, respectively).</p> Full article ">Figure 2
<p>(<b>a</b>) Wide-scan XPS spectrum of the WOx films; (<b>b</b>) W 4f XPS spectrum of the WOx and its peak fitting.</p> Full article ">Figure 3
<p>(<b>a</b>) TEM image of CdSe@ZnS QDs; (<b>b</b>) PL and absorption spectra of the QDs in methylbenzene (the inset shows the image of the QDs dispersed in methylbenzene).</p> Full article ">Figure 4
<p>(<b>a</b>) Schematic diagram of the preparation and formation process of WOx:PEDOT:PSS films; (<b>b</b>) structure of QLED and the functional layer materials used in this work; (<b>c</b>) schematic illustration of the energy level diagram.</p> Full article ">Figure 5
<p>(<b>a</b>) Current density−luminance−voltage (J−L−V); (<b>b</b>) current efficiency−power efficiency with luminance characteristics for the different volume ratios of PEDOT:PSS:WOx−based QLED; (<b>c</b>) quantity statistics of the maximum current efficiency of the device with optimal HIL; (<b>d</b>) EL spectra of the standard and optimal device (the inset shows a photographic image of the green QLED).</p> Full article ">Figure 6
<p>Operating lifetime characteristics of the PEDOT:PSS:WOx−based and PEDOT:PSS-based QLEDs.</p> Full article ">Figure 7
<p>SEM images of (<b>a</b>) the ITO glass and the (<b>b</b>) ITO/PEDOT:PSS and (<b>c</b>) ITO/PEDOT:PSS:WOx (10:1) films; AFM images of (<b>d</b>) the ITO glass and the (<b>e</b>) ITO/PEDOT:PSS and (<b>f</b>) ITO/PEDOT:PSS:WOx (10:1) films. The surface roughness RMS values for each condition were 2.20 nm, 1.25 nm, and 1.02 nm, respectively).</p> Full article ">Figure 8
<p>Transmittance of the PEDOT:PSS/glass and PEDOT:PSS:WOx/glass.</p> Full article ">Figure 9
<p>Current density−voltage characteristics of the hole-only devices with pure PEDOT:PSS and PEDOT:PSS:WOx (10:1) HILs.</p> Full article ">
13 pages, 3486 KiB  
Review
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 4 | Viewed by 2044
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 Special Issue Reviews in Liquid Crystals)
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<p>Color online. (<b>a</b>) A plot of the pretilt angle vs. the exposure energy (solid circles). Open legends represent experimental results repeated after several hours of photographing and thermal exposure. The top insertion shows a simplified fabrication procedure of the LC cell; the bottom insertion shows the photograph of the prepared LC cell under crossed polarizers for distinct areas with different irradiance and pretilt angles. (<b>b</b>) Exposure setup with spatially changing light intensity along the substrate plane.</p> Full article ">Figure 2
<p>Switchable lenses with non-uniform LC anchoring energy: (<b>a</b>) diverging lens and (<b>b</b>) converging lens.</p> Full article ">Figure 3
<p>Color online. (<b>a</b>) The stacked layer structure of the alignment film for lens applications and (<b>b</b>) dependence of the pretilt angle vs. stacked layer thickness for different coefficients <span class="html-italic">p</span>.</p> Full article ">Figure 4
<p>Color online. (<b>a</b>) A cross-section of photoaligned Fresnel zone plate lens. Microscopic image of Fresnel zone plate lens under crossed polarizers: (<b>b</b>) LC Fresnel zone plate lens (lens I) with the focal length of 3.2 mm, (<b>c</b>) zoomed-in image (<b>b</b>), and (<b>d</b>) LC Fresnel zone plate lens (lens II) with the focal length of 50 mm.</p> Full article ">Figure 5
<p>Color online. (<b>a</b>) Layered structure of sensor. Ferroelectric liquid crystal helix axis (FLC–576, helix pitch: 200 nm) is aligned along the x-axis. (<b>b</b>) Measured (symbols) and calculated (lines) dependencies of the normalized reflection on the voltage amplitude. Liquid crystal thickness: 5 μm. Measurements were carried out at the frequency of 500 Hz, β = 0°, 17°, and 45°.</p> Full article ">Figure 6
<p>The basic idea of the voltage sensor: (<b>a</b>) the surface transmits the incident wavelength (<span class="html-italic">E</span> = 0, no reflection) and (<b>b</b>) the surface plays the role of a mirror when external electric field is applied. The arrows show directions of principal refractive indices.</p> Full article ">Figure 7
<p>(<b>a</b>) A schematic representation of the LC cell and sensor head and (<b>b</b>) experimental power of optical signals from the two fibers vs. the applied voltage.</p> Full article ">Figure 8
<p>Color online. A schematic representation of polarization-dependent optical device: The formation of a refractive interface for s-polarized light by an NLC within the bulk of an LC cell.</p> Full article ">Figure 9
<p>(<b>a</b>) An experimental setup for ellipticity control and (<b>b</b>) dependence of the ellipticity angle and azimuthal angle vs. the applied electric field.</p> Full article ">
13 pages, 4553 KiB  
Article
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 3 | Viewed by 1332
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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<p>Microstructure of GH4169 alloy after solution treatment.</p> Full article ">Figure 2
<p>Schematic diagram with dimensions (in mm) of tensile samples: (<b>a</b>) room temperature tensile specimen; (<b>b</b>) elevated temperature tensile specimen.</p> Full article ">Figure 3
<p>Tensile test at room temperature of specimens at different aging temperatures: (<b>a</b>) stress–strain curves; (<b>b</b>) strength and ductility values.</p> Full article ">Figure 4
<p>Tensile test at elevated temperature of specimens at different aging temperatures: (<b>a</b>) stress–strain curves; (<b>b</b>) strength and ductility values.</p> Full article ">Figure 5
<p>Microstructure of GH4169 treated at different aging temperatures: (<b>a</b>) A720; (<b>b</b>) A750; (<b>c</b>) A780; (<b>d</b>) EDS analysis of bulk precipitates.</p> Full article ">Figure 6
<p>XRD patterns of three heat-treated samples.</p> Full article ">Figure 7
<p>TEM image of γ″ and γ′ phases: (<b>a</b>), (<b>d</b>) and (<b>g</b>) are the bright field images of samples A720, A750 and A780, respectively; (<b>b</b>), (<b>e</b>) and (<b>h</b>) are the selected electron diffraction patterns of γ″ and γ′ in A720, A750 and A780 samples, respectively; (<b>c</b>,<b>f</b>,<b>i</b>) are the dark field images of A720, A750 and A780 samples made by (002) γ″ diffraction spots.</p> Full article ">Figure 8
<p>Interface relationship between γ″ phase and the matrix: (<b>a</b>–<b>c</b>) are HRTEM images of γ″ in A720, A750 and A780 samples, respectively; (<b>d</b>–<b>f</b>) are the IFFT images in the yellow box.</p> Full article ">Figure 9
<p>SEM images of δ phase of samples at different aging temperatures: (<b>a</b>) A720; (<b>b</b>) A750; (<b>c</b>) A780; (<b>d</b>) Intragranular δ phase of A780; (<b>e</b>) EDS analysis of grain boundary precipitates.</p> Full article ">Figure 10
<p>Fracture surfaces of tensile samples at room temperature: (<b>a</b>) A720; (<b>b</b>) A750; (<b>c</b>) A780.</p> Full article ">Figure 11
<p>Fracture surfaces of tensile specimen at elevated temperature: (<b>a</b>) A720; (<b>b</b>) A750; (<b>c</b>) A780; (<b>d</b>) EDS analysis of inclusions at hole bottom.</p> Full article ">
15 pages, 2342 KiB  
Article
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 2 | Viewed by 1354
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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<p>The crystal structure of alunogen obtained by [<a href="#B6-crystals-13-00963" class="html-bibr">6</a>].</p> Full article ">Figure 2
<p>The place of the samples’ collection: (<b>a</b>) the position of the Verkhne–Koshelevsky geothermal field on the map of Kamchatka; (<b>b</b>) the position of the Verkhne–Koshelevsky geothermal field relative to Koshelev and Kambalny volcanoes (both actve); (<b>c</b>) the general view to Verkhne–Koshelevsky geothermal field, steaming jets are visible; (<b>d</b>) the efflorescent polymineral crust composed of hydrated sulphates on the Verkhne–Koshelevsky geothermal field surface.</p> Full article ">Figure 3
<p>The crystal structure of alunogen obtained therein: (<b>a</b>) the framework showing H sites and hydrogen bonding scheme; (<b>b</b>) enlarged part showing labelling of the “zeolite” H<sub>2</sub>O molecules and disordering of one of them producing two partially occupied sites: O28 and O29.</p> Full article ">Figure 4
<p>The average parameters of hydrogen bonding represented by H<sup>…</sup><b>A</b> bonds and <b>D</b>–H<sup>…</sup><b>A</b> angles of (<b>a</b>) Al(H<sub>2</sub>O)<sub>6</sub> octahedra linked to SO<sub>4</sub> tetrahedra or the “zeolite” H<sub>2</sub>O molecule and (<b>b</b>) the “zeolite” H<sub>2</sub>O molecules linked to SO<sub>4</sub> tetrahedra or the symmetrically independent “zeolite” H<sub>2</sub>O molecule.</p> Full article ">
9 pages, 3636 KiB  
Article
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 1232
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 NX; and ferroelectric nematic NF. 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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<p>The molecular structure, the phase sequence, and the transition temperatures of the DIO compound.</p> Full article ">Figure 2
<p>Three-dimensional (3D) plots of (<b>a</b>) permittivity and (<b>b</b>) dielectric loss spectra for a planar-aligned cell with a cell thickness of 25 μm.</p> Full article ">Figure 3
<p>Textures of the DIO compound with molecules aligned planarly for a 25 µm thick cell at (<b>a</b>) 160 °C, (<b>b</b>) 80 °C, and (<b>c</b>) 60 °C, respectively. The arrow in (<b>a</b>) indicates the rubbing direction which is the same in (<b>b</b>,<b>c</b>).</p> Full article ">Figure 4
<p>The variation of (<b>a</b>) dielectric permittivity and (<b>b</b>) the dielectric loss with temperature for a planar-aligned cell with a thickness of 25 µm.</p> Full article ">Figure 5
<p>Planar-aligned cells. The temperature dependence of the relaxation processes: dielectric strength (Δ<span class="html-italic">ε</span>) (filled symbols) and the relaxation frequency (<span class="html-italic">f</span>) (unfilled symbols) in planarly aligned cell of (<b>a</b>) 25 μmand (<b>b</b>) 4 μmthick cell. The experimental data points are shown in color: blue (P<sub>0</sub>), black (P<sub>1</sub>), and red (P<sub>2</sub>) ((<b>b</b>) [<a href="#B27-crystals-13-00962" class="html-bibr">27</a>]). Please note that especially the behavior in the thin and thick cells for process 1 are very different.</p> Full article ">Figure 6
<p>(<b>a</b>) Thick homeotropic cell: Three-dimensional dielectric loss spectra for a 28 µm−thick homeotropic cell and the corresponding (<b>b</b>) dielectric parameters.</p> Full article ">
15 pages, 5089 KiB  
Article
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 6 | Viewed by 1867
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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<p>HR-TEM images of synthesized nitrogen-doped graphene quantum dots at different magnifications. From left to right, the scale bars are 50 nm (<b>a</b>), 20 nm (<b>b</b>), and 5 nm (<b>c</b>).</p> Full article ">Figure 2
<p>Top-view and cross-sectional view (inset) FESEM images of N-GQD:SnO<sub>2</sub> nanocomposite ultrathin films coated on FTO substrates. (<b>S0</b>–<b>S3</b>) samples had N-GQD ratios of 0%, 1%, 2%, and 3%, respectively.</p> Full article ">Figure 3
<p>XRD patterns of N-GQDs and N-GQD:SnO<sub>2</sub> nanocomposite ultrathin films with N-GQD ratios of 0% (S0), 1% (S1), 2% (S2), and 3% (S3) coated on glass substrates. The lines at the bottom of the figure denote the standard diffraction patterns of SnO<sub>2</sub> (JCPDS card No.41-1445) and graphitic carbon (marked in black color) as references.</p> Full article ">Figure 4
<p>FTIR spectra of N-GQD:SnO<sub>2</sub> nanocomposite ultrathin films with N-GQD ratios of 0% (S0), 1% (S1), 2% (S2), and 3% (S3).</p> Full article ">Figure 5
<p>Transmittance spectra of N-GQD:SnO<sub>2</sub> nanocomposite ultrathin films with N-GQDs ratios of 0% (S0), 1% (S1), 2% (S2), and 3% (S3).</p> Full article ">Figure 6
<p>2D excitation and emission contour map of N-GQDs samples measured from 300 to 750 nm, corresponding to excitation wavelengths from 240 to 300 nm. The color indicates the intensity of the emission.</p> Full article ">Figure 7
<p>Photoluminescence (PL) spectra of perovskite films deposited on FTO/N-GQD:SnO<sub>2</sub> with N-GQD ratios of 0% (S0), 1% (S1), 2% (S2), and 3% (S3). The dashed arrow represents the photoluminescence quenching phenomenon.</p> Full article ">Figure 8
<p><span class="html-italic">J–V</span> curves of the FTO/N-GQD:SnO<sub>2</sub>/Au devices measured under dark conditions. The S0, S1, S2, and S3 samples had N-GQD ratios of 0%, 1%, 2%, and 3%, respectively.</p> Full article ">Figure 9
<p>(<b>a</b>) Schematic illustration of the planar PSC with a structure of glass/FTO/N-GQD:SnO<sub>2</sub>/perovskite/Spiro-OMeTAD/Au. (<b>b</b>) Cross-sectional view of an FESEM image of a PSC based on a N-GQD:SnO<sub>2</sub> nanocomposite ultrathin film. (<b>c</b>) Working principle and energy band diagram of the PSC.</p> Full article ">Figure 10
<p><span class="html-italic">J–V</span> curves of the planar PSCs based on N-GQD:SnO<sub>2</sub> electron transport layers with N-GQD ratios of 0% (D0), 1% (D1), 2% (D2), and 3% (D3) with AM1.5 G simulated solar illumination.</p> Full article ">Figure 11
<p>Dark <span class="html-italic">J–V</span> curves of the planar PSCs based on N-GQD:SnO<sub>2</sub> nanocomposite electron transport layers with different N-GQD ratios.</p> Full article ">Figure 12
<p>Electrochemical impedance spectra of the planar PSCs based on N-GQD:SnO<sub>2</sub> nanocomposite electron transport layers with different N-GQD ratios in dark condition at <span class="html-italic">V</span><sub>oc</sub> bias.</p> Full article ">Figure 13
<p>EQE spectra of the planar PSCs based on SnO<sub>2</sub> (D0) and N-GQD:SnO<sub>2</sub> nanocomposite champion device (D2).</p> Full article ">Figure 14
<p>The roles of N-GQDs in the nanocomposite N-GQD:SnO<sub>2</sub> ETLs in enhancing PSC efficiency.</p> Full article ">
13 pages, 3681 KiB  
Article
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 1174
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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<p>Diffractogram of the prepared fibers and respective indexing.</p> Full article ">Figure 2
<p>(<b>a</b>) Measured and calculated spectra of the fiber grown at 10 mm/h; (<b>b</b>) variation, in percentage, of the chemical composition of the prepared samples.</p> Full article ">Figure 3
<p>(<b>a</b>) Raman spectra of the transverse cross-section of the fibers grown at 5 mm/h, 10 mm/h, and 25 mm/h; (<b>b</b>) Raman spectrum of the longitudinal cross-section of the fiber grown at 5 mm/h (inset: Raman spectrum of Fe<sub>2</sub>O<sub>3</sub>, adapted from [<a href="#B24-crystals-13-00960" class="html-bibr">24</a>]).</p> Full article ">Figure 4
<p>SEM micrographs of the selected fibers: (<b>a</b>) longitudinal cross-section of the 25 mm/h fiber; (<b>b</b>) transverse cross-section of the 25 mm/h fiber; (<b>c</b>) enlarged image of the selected area in (<b>b</b>); (<b>d</b>) longitudinal cross-section of the 10 mm/h fiber; (<b>e</b>) transverse cross-section of the 10 mm/h fiber; (<b>f</b>) enlarged image of the selected area in (<b>e</b>); (<b>g</b>) longitudinal cross-section of the 5 mm/h fiber; (<b>h</b>) transverse cross-section of the 5 mm/h fiber; (<b>i</b>) enlarged image of the selected area in (<b>h</b>).</p> Full article ">Figure 5
<p>Frequency dependence of the dielectric constant, measured at (<b>a</b>) 150 K, (<b>b</b>) 300 K, and (<b>c</b>) 350 K, for the fibers grown at 5, 10, 25, and 200 mm/h.</p> Full article ">Figure 6
<p>Frequency dependence of the loss tangent, measured at (<b>a</b>) 150 K, (<b>b</b>) 300 K, and (<b>c</b>) 350 K, for the fibers grown at 5, 10, 25, and 200 mm/h.</p> Full article ">Figure 7
<p>Imaginary part of the modulus, <span class="html-italic">M</span>″, as a function of frequency, for temperatures between 100 and 370 K, in steps of 10 K, for the fibers grown at (<b>a</b>) 5 mm/h; (<b>b</b>) 10 mm/h; (<b>c</b>) 25 mm/h; (<b>d</b>) 200 mm/h.</p> Full article ">Figure 8
<p>Arrhenius plot of the peak frequencies obtained from the imaginary part of the electrical modulus.</p> Full article ">
13 pages, 1270 KiB  
Review
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 8 | Viewed by 4130
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

Graphical abstract
Full article ">Figure 1
<p>Schematic illustration of nucleation and growth mechanism. Discrete and ultramicroscopic colloidal nuclei are agglomerated after certain period of induction. The agglomeration rate constant is (Kij). The process further proceeds to produce dimer, trimer, and finally polymeric particles. If the reaction conditions, such as the temperature, polarity of solvents, or rate of stirring, are not selected properly, the agglomerates redissolve in the mixture with a dissolution rate constant equal to (K’ij). In such cases, precipitated particles, which are still in the meta-phase are not fully stabilized to be completely a solid phase, and thus can be gradually re-dispersed in the suspension.</p> Full article ">Figure 2
<p>The chart of different types of nucleation.</p> Full article ">Figure 3
<p>TEM image of (<b>A</b>) zeolite Beta and (<b>B</b>) zeolite Y crystalline particles. Two edges of crystallites with morphological dislocation are shown with red circles.</p> Full article ">
18 pages, 66797 KiB  
Article
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 1584
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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<p>Interferometry method setup for phase uniformity measurement (P, polarizer, NPBS, non-polarizing beam splitter, AP, aperture, M, reference flat mirror).</p> Full article ">Figure 2
<p>Basic optical setup for polarimetric method (P, polarizer, NPBS, non-polarizing beam splitter, AP, aperture, TS, translation stage, PD, photo detector).</p> Full article ">Figure 3
<p>Problematic phase measurement due to non-ideal factors: (<b>a</b>) phase measurement result; (<b>b</b>) interference pattern of extraordinary light on the LCoS device.</p> Full article ">Figure 4
<p>Principle of the polarimetric method (P, polarizer, WP, waveplate).</p> Full article ">Figure 5
<p>Different reflection paths in the LCoS device: (<b>a</b>) front reflection; (<b>b</b>) ideal condition; (<b>c</b>) back reflection. Glass thickness is shown in this figure but ignored in calculation.</p> Full article ">Figure 6
<p>Simulation of the effect from 5% back reflection on <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>I</mi> <mo>″</mo> </mrow> <mrow> <mi>o</mi> <mi>u</mi> <mi>t</mi> </mrow> </msub> </mrow> </semantics></math> and phase error: (<b>a</b>) <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>I</mi> <mo>″</mo> </mrow> <mrow> <mi>o</mi> <mi>u</mi> <mi>t</mi> </mrow> </msub> <mo>−</mo> <mi>G</mi> <mi>L</mi> </mrow> </semantics></math> relation; (<b>b</b>) peak and average phase error across the active area.</p> Full article ">Figure 7
<p>Basic principle of the LCoS uniformity extraction process: (<b>a</b>) locate the error-free point in the measured intensity curve of a specific region as <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>G</mi> <mi>L</mi> </mrow> <mrow> <mn>2</mn> <mi>π</mi> </mrow> </msub> </mrow> </semantics></math>; (<b>b</b>) calculate the average phase of the whole active area at <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>G</mi> <mi>L</mi> </mrow> <mrow> <mn>2</mn> <mi>π</mi> </mrow> </msub> </mrow> </semantics></math> and max <math display="inline"><semantics> <mrow> <mi>G</mi> <mi>L</mi> </mrow> </semantics></math>; (<b>c</b>) estimate the LC layer thickness in this region; (<b>d</b>) repeat for all regions and acquire the uniformity result.</p> Full article ">Figure 8
<p>Simulated result when the polarizers are misaligned by 10 degrees: (<b>a</b>) actual phase in <math display="inline"><semantics> <mrow> <mi>π</mi> </mrow> </semantics></math>; (<b>b</b>) measured phase in <math display="inline"><semantics> <mrow> <mi>π</mi> </mrow> </semantics></math>; (<b>c</b>) measurement error in <math display="inline"><semantics> <mrow> <mi>π</mi> </mrow> </semantics></math>.</p> Full article ">Figure 9
<p>Real-life LCoS phase measurement: (<b>a</b>) measured phase in <math display="inline"><semantics> <mrow> <mi>π</mi> </mrow> </semantics></math> with correct alignment; (<b>b</b>) measurement error in <math display="inline"><semantics> <mrow> <mi>π</mi> </mrow> </semantics></math>, with 8° of P2 misalignment.</p> Full article ">Figure 10
<p>Simulated result with 5% back reflection (maximum error point): (<b>a</b>) location of data point; (<b>b</b>) actual phase in <math display="inline"><semantics> <mrow> <mi>π</mi> </mrow> </semantics></math>; (<b>c</b>) measured phase in <math display="inline"><semantics> <mrow> <mi>π</mi> </mrow> </semantics></math>; (<b>d</b>) measurement error in <math display="inline"><semantics> <mrow> <mi>π</mi> </mrow> </semantics></math>.</p> Full article ">Figure 11
<p>Simulated result with 5% back reflection (minimum error point): (<b>a</b>) location of data point; (<b>b</b>) actual phase in <math display="inline"><semantics> <mrow> <mi>π</mi> </mrow> </semantics></math>; (<b>c</b>) measured phase in <math display="inline"><semantics> <mrow> <mi>π</mi> </mrow> </semantics></math>; (<b>d</b>) measurement error in <math display="inline"><semantics> <mrow> <mi>π</mi> </mrow> </semantics></math>.</p> Full article ">Figure 11 Cont.
<p>Simulated result with 5% back reflection (minimum error point): (<b>a</b>) location of data point; (<b>b</b>) actual phase in <math display="inline"><semantics> <mrow> <mi>π</mi> </mrow> </semantics></math>; (<b>c</b>) measured phase in <math display="inline"><semantics> <mrow> <mi>π</mi> </mrow> </semantics></math>; (<b>d</b>) measurement error in <math display="inline"><semantics> <mrow> <mi>π</mi> </mrow> </semantics></math>.</p> Full article ">Figure 12
<p>Phase measurement at near <math display="inline"><semantics> <mrow> <mfenced separators="|"> <mrow> <mn>2</mn> <mi>k</mi> <mo>+</mo> <mn>1</mn> </mrow> </mfenced> <mi>π</mi> </mrow> </semantics></math> phase: (<b>a</b>) intensity-GL curve and indication of the data point; (<b>b</b>) calculated phase distribution in <math display="inline"><semantics> <mrow> <mi>π</mi> </mrow> </semantics></math>.</p> Full article ">Figure 13
<p>Phase measurement at near <math display="inline"><semantics> <mrow> <mn>2</mn> <mi>k</mi> <mi>π</mi> </mrow> </semantics></math> phase: (<b>a</b>) intensity-GL curve and indication of the data point; (<b>b</b>) calculated phase distribution in <math display="inline"><semantics> <mrow> <mi>π</mi> </mrow> </semantics></math>.</p> Full article ">Figure 14
<p>Speculated LC layer thickness in simulation: (<b>a</b>) speculated thickness; (<b>b</b>) error of the speculation.</p> Full article ">Figure 15
<p>Result of the correction: (<b>a</b>) calculated LC layer thickness; (<b>b</b>) interference pattern.</p> Full article ">Figure 16
<p>Phase speculation based on the LC layer thickness uniformity result: (<b>a</b>) speculated phase at <math display="inline"><semantics> <mrow> <mi>G</mi> <mi>L</mi> <mo>=</mo> <mn>95</mn> </mrow> </semantics></math> where error reaches maximum; (<b>b</b>) error of the speculation at <math display="inline"><semantics> <mrow> <mi>G</mi> <mi>L</mi> <mo>=</mo> <mn>95</mn> </mrow> </semantics></math>.</p> Full article ">Figure 17
<p>Measured phase in <math display="inline"><semantics> <mrow> <mi>π</mi> </mrow> </semantics></math> with binary grating method.</p> Full article ">Figure A1
<p>Comparison of the light components before and after polarizer P2: (<b>a</b>) extraordinary reflections before P2; (<b>b</b>) ordinary reflections before P2; (<b>c</b>) combined reflections after P2.</p> Full article ">Figure A1 Cont.
<p>Comparison of the light components before and after polarizer P2: (<b>a</b>) extraordinary reflections before P2; (<b>b</b>) ordinary reflections before P2; (<b>c</b>) combined reflections after P2.</p> Full article ">Figure A2
<p>Non-ideal optical setup for polarimetric method (P, polarizer, NPBS, non-polarizing beam splitter, AP, aperture, TS, translation stage, PD, photo detector).</p> Full article ">Figure A3
<p>Improved optical setup for polarimetric method (P, polarizer, AP, aperture, TS, translation stage, PD, photo detector).</p> Full article ">
21 pages, 7219 KiB  
Article
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 948
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 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 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 B→ is slightly tilted with respect to the electrode plane, the indeterminacy on the TIC orientation is removed when the TIC is directed along 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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<p>(<b>a</b>) Cross section in a plane containing the <math display="inline"><semantics> <mover accent="true"> <mi>c</mi> <mo>→</mo> </mover> </semantics></math>-director of the cholesteric director field in the TIC configuration, as described in the text. In the nail diagram, the head of the nails illustrate the out-of-plane component of the director. (<b>b</b>) S2 sphere trajectory of the director field along the straight path indicated by the arrow in (<b>a</b>), which results in a closed path that begins and ends in the North pole. The different geometrical parameters defined in the text are depicted in the sketch.</p> Full article ">Figure 2
<p>Spinodal limit calculated with Equation (<a href="#FD18-crystals-13-00957" class="html-disp-formula">18</a>) when <math display="inline"><semantics> <mrow> <mi>B</mi> <mo>=</mo> <mn>0</mn> </mrow> </semantics></math> (green line), and spinodal limit calculated numerically (dashed red line) and with the approximate Formula (<a href="#FD20-crystals-13-00957" class="html-disp-formula">20</a>) (solid blue line) when <math display="inline"><semantics> <mrow> <mi>B</mi> <mo>=</mo> <mn>0.56</mn> </mrow> </semantics></math>.</p> Full article ">Figure 3
<p>(<b>a</b>) Angle <math display="inline"><semantics> <msub> <mi>β</mi> <mi>m</mi> </msub> </semantics></math> giving the orientation of the TIC as a function of time when <math display="inline"><semantics> <mrow> <mi>d</mi> <mo>=</mo> <mn>7.5</mn> <mtext> </mtext> <mi mathvariant="sans-serif">μ</mi> </mrow> </semantics></math>m and <math display="inline"><semantics> <mrow> <msub> <mi>β</mi> <mi>i</mi> </msub> <mo>=</mo> <mn>0.1</mn> </mrow> </semantics></math> (left column) or <math display="inline"><semantics> <mrow> <msub> <mi>β</mi> <mi>i</mi> </msub> <mo>=</mo> <mi>π</mi> <mo>/</mo> <mn>2</mn> <mo>−</mo> <mn>0.1</mn> </mrow> </semantics></math> (right column). In each case, a voltage below and above the spinodal limit is shown. The voltage (in Vrms) is indicated on each graph. (<b>b</b>) Angle <math display="inline"><semantics> <msub> <mi>β</mi> <mi>m</mi> </msub> </semantics></math> as a function of the applied voltage <span class="html-italic">V</span>; (<b>c</b>) Energy difference between the TIC1 and the TIC2 as a function of the applied voltage <span class="html-italic">V</span> calculated in the voltage interval where the two TIC are observed.</p> Full article ">Figure 4
<p>Phase diagram showing the two transition lines between the TIC1 and TIC2 solutions. The dashed and dotted lines are the spinodal limits. (<b>A</b>–<b>C</b>) Director trajectories on the sphere S2 calculated at points A (<math display="inline"><semantics> <mrow> <mi>d</mi> <mo>=</mo> <mn>7</mn> <mtext> </mtext> <mi mathvariant="sans-serif">μ</mi> </mrow> </semantics></math>m, <math display="inline"><semantics> <mrow> <mi>V</mi> <mo>=</mo> <mn>2.5</mn> <mtext> </mtext> </mrow> </semantics></math>Vrms), B (<math display="inline"><semantics> <mrow> <mi>d</mi> <mo>=</mo> <mn>10</mn> <mtext> </mtext> <mi mathvariant="sans-serif">μ</mi> </mrow> </semantics></math>m, <math display="inline"><semantics> <mrow> <mi>V</mi> <mo>=</mo> <mn>5</mn> <mtext> </mtext> </mrow> </semantics></math>Vrms) and C (<math display="inline"><semantics> <mrow> <mi>d</mi> <mo>=</mo> <mn>14</mn> <mtext> </mtext> <mi mathvariant="sans-serif">μ</mi> </mrow> </semantics></math>m, <math display="inline"><semantics> <mrow> <mi>V</mi> <mo>=</mo> <mn>8</mn> <mtext> </mtext> </mrow> </semantics></math>Vrms) of the phase diagram. The North pole N corresponds to the homeotropic nematic.</p> Full article ">Figure 5
<p>Angles <math display="inline"><semantics> <mi>α</mi> </semantics></math> and <math display="inline"><semantics> <mi>β</mi> </semantics></math> of a TIC1 (<b>a</b>–<b>d</b>) and a TIC2 (<b>e</b>–<b>h</b>) configuration in the middle of the sample <math display="inline"><semantics> <mrow> <mo>(</mo> <mi>z</mi> <mo>=</mo> <mi>d</mi> <mo>/</mo> <mn>2</mn> <mo>)</mo> </mrow> </semantics></math> as a function of time when the magnetic field is slightly tilted. (<b>a</b>,<b>b</b>,<b>e</b>,<b>f</b>) correspond to <math display="inline"><semantics> <mrow> <mi>θ</mi> <mo>=</mo> <mn>0.1</mn> </mrow> </semantics></math>; (<b>c</b>,<b>d</b>,<b>g</b>,<b>h</b>) correspond to <math display="inline"><semantics> <mrow> <mi>θ</mi> <mo>=</mo> <mo>−</mo> <mn>0.1</mn> </mrow> </semantics></math>.</p> Full article ">Figure 6
<p>Possible orientations of the <math display="inline"><semantics> <mrow> <mover accent="true"> <mi>c</mi> <mo>→</mo> </mover> <mo>−</mo> </mrow> </semantics></math>director of the TIC1 and TIC2 when the magnetic field is slightly tilted from the horizontal. Solid red arrows: <math display="inline"><semantics> <mrow> <mi>θ</mi> <mo>&gt;</mo> <mn>0</mn> </mrow> </semantics></math>; dotted blue arrows: <math display="inline"><semantics> <mrow> <mi>θ</mi> <mo>&lt;</mo> <mn>0</mn> </mrow> </semantics></math>.</p> Full article ">Figure 7
<p>(<b>a</b>) Voltages <math display="inline"><semantics> <msub> <mi>V</mi> <mn>1</mn> </msub> </semantics></math>, <math display="inline"><semantics> <msubsup> <mi>V</mi> <mn>1</mn> <mo>+</mo> </msubsup> </semantics></math> and <math display="inline"><semantics> <msubsup> <mi>V</mi> <mn>1</mn> <mo>−</mo> </msubsup> </semantics></math> as a function of the inclination angle <math display="inline"><semantics> <mi>θ</mi> </semantics></math> of the magnetic field. <math display="inline"><semantics> <mrow> <mi>d</mi> <mo>=</mo> <mn>7.5</mn> <mtext> </mtext> <mi mathvariant="sans-serif">μ</mi> </mrow> </semantics></math>m and <math display="inline"><semantics> <mrow> <mi>B</mi> <mo>=</mo> <mn>0.56</mn> <mtext> </mtext> </mrow> </semantics></math>T. (<b>b</b>) Angle <math display="inline"><semantics> <msubsup> <mi>β</mi> <mi>m</mi> <mo>+</mo> </msubsup> </semantics></math> (in degree) as a function of the applied voltage for different inclinations of the magnetic field. From bottom to top, <math display="inline"><semantics> <mi>θ</mi> </semantics></math> = 0, 0.1, 0.2 and <math display="inline"><semantics> <mrow> <mn>0.3</mn> </mrow> </semantics></math> rad. <math display="inline"><semantics> <mrow> <mi>d</mi> <mo>=</mo> <mn>7.5</mn> <mtext> </mtext> <mi mathvariant="sans-serif">μ</mi> </mrow> </semantics></math>m and <math display="inline"><semantics> <mrow> <mi>B</mi> <mo>=</mo> <mn>0.56</mn> <mtext> </mtext> </mrow> </semantics></math>T.</p> Full article ">Figure 8
<p>Schematic representation of the experimental setup. S: Halogen lamp; F: green filter (<math display="inline"><semantics> <mrow> <mi>λ</mi> <mo>=</mo> <mn>546</mn> <mspace width="3.33333pt"/> </mrow> </semantics></math>nm); P: polarizer parallel to <span class="html-italic">x</span>; QW: quarter-wave plate with its slow axis oriented at <math display="inline"><semantics> <msup> <mn>45</mn> <mo>∘</mo> </msup> </semantics></math> with respect to the <span class="html-italic">x</span>-axis; M: permanent magnet (Halbach ring). The dotted line gives the orientation of the magnetic field; S: homeotropic sample; O: objective (macrozoom lens); A: rotating analyzer motorized with a stepping motor. C: video camera.</p> Full article ">Figure 9
<p>(<b>a</b>–<b>e</b>) Pi-wall between two TIC1 oriented in opposite directions which forms spontaneously in the middle of the 6.05 <math display="inline"><semantics> <mi mathvariant="sans-serif">μ</mi> </semantics></math>m-thick sample when a voltage larger than <math display="inline"><semantics> <msub> <mi>V</mi> <mrow> <mi>t</mi> <mi>h</mi> </mrow> </msub> </semantics></math> is applied. From (<b>a</b>–<b>e</b>) <math display="inline"><semantics> <mrow> <mi>V</mi> <mo>=</mo> <mn>3.5</mn> <mo>,</mo> <mn>4</mn> <mo>,</mo> <mn>5</mn> <mo>,</mo> <mn>6</mn> <mo>,</mo> <mn>6.3</mn> <mspace width="3.33333pt"/> </mrow> </semantics></math>Vrms. The wall is perpendicular to the magnetic field <span class="html-italic">B</span>. (<b>f</b>) TIC2 observed at <math display="inline"><semantics> <mrow> <mi>V</mi> <mo>=</mo> <mn>6.8</mn> <mspace width="3.33333pt"/> </mrow> </semantics></math>Vrms. The arrows indicate how the <math display="inline"><semantics> <mover accent="true"> <mi>c</mi> <mo>→</mo> </mover> </semantics></math>-director rotates in the sample. Observation without the quarter-wave plate between crossed polarizers (analyzer parallel to <span class="html-italic">B</span>). The white bar is 50 <math display="inline"><semantics> <mi mathvariant="sans-serif">μ</mi> </semantics></math>m long. (<b>g</b>) Width <span class="html-italic">W</span> of the pi-wall as a function of the voltage measured at increasing and decreasing voltage.</p> Full article ">Figure 10
<p>Transmitted intensity as a function of angle <math display="inline"><semantics> <mi>φ</mi> </semantics></math> between the analyzer and the <span class="html-italic">x</span>-axis. The polarizer is along the <span class="html-italic">x</span>-axis and a quarter-wave plate has been inserted between the polarizer and the sample, with its slow axis at 45<math display="inline"><semantics> <msup> <mrow/> <mo>∘</mo> </msup> </semantics></math> from the <span class="html-italic">x</span>-axis. Sample of thickness <math display="inline"><semantics> <mrow> <mi>d</mi> <mo>=</mo> <mn>6.05</mn> <mspace width="3.33333pt"/> <mi mathvariant="sans-serif">μ</mi> </mrow> </semantics></math>m. The curves on the top row are experimental and those in the bottom row are theoretical. From (<b>a</b>–<b>c</b>) <span class="html-italic">V</span> = 5, 6, and 6.3 Vrms. The solid line curves correspond to a TIC1 and the dashed lines to a TIC2. In (<b>b</b>) the curves in full line have been obtained by increasing the voltage and those in dashed line by decreasing the voltage.</p> Full article ">Figure 11
<p>Cholesteric fingers of the first type (CF1) observed between crossed polarizer and analyzer in the <math display="inline"><semantics> <mrow> <mn>7.51</mn> <mspace width="3.33333pt"/> <mi mathvariant="sans-serif">μ</mi> </mrow> </semantics></math>m-thick sample by focusing on a dust particle inside the sample. From (<b>a</b>–<b>i</b>) <span class="html-italic">V</span> increases from 1.6 to 2.4 Vrms by increments of 0.1. The white bar is <math display="inline"><semantics> <mrow> <mn>50</mn> <mspace width="3.33333pt"/> <mi mathvariant="sans-serif">μ</mi> </mrow> </semantics></math>m long.</p> Full article ">Figure 12
<p>Transmitted intensity as a function of angle <math display="inline"><semantics> <mi>φ</mi> </semantics></math>. Same optical conditions as in <a href="#crystals-13-00957-f010" class="html-fig">Figure 10</a>. Sample of thickness <math display="inline"><semantics> <mrow> <mi>d</mi> <mo>=</mo> <mn>10.3</mn> <mspace width="3.33333pt"/> <mi mathvariant="sans-serif">μ</mi> </mrow> </semantics></math>m. From (<b>a</b>–<b>c</b>), <math display="inline"><semantics> <mrow> <mi>V</mi> <mspace width="3.33333pt"/> <mo>=</mo> <mspace width="3.33333pt"/> </mrow> </semantics></math>3, 8, and 20 Vrms. The curves on the top row are experimental and those in the bottom row are theoretical. At this thickness, only the TIC2 is observed.</p> Full article ">Figure 13
<p>Transmitted intensity as a function of angle <math display="inline"><semantics> <mi>φ</mi> </semantics></math>. Same conditions as in <a href="#crystals-13-00957-f010" class="html-fig">Figure 10</a>. Sample of thickness <math display="inline"><semantics> <mrow> <mi>d</mi> <mo>=</mo> <mn>12.65</mn> <mspace width="3.33333pt"/> <mi mathvariant="sans-serif">μ</mi> </mrow> </semantics></math>m. From (<b>a</b>–<b>c</b>), <math display="inline"><semantics> <mrow> <mi>V</mi> <mspace width="3.33333pt"/> <mo>=</mo> <mspace width="3.33333pt"/> </mrow> </semantics></math>3, 4, and 5 Vrms. The curves on the top row are experimental and those in the bottom row are theoretical. The solid line curves correspond to a TIC1 and the dashed lines to a TIC2. In (<b>b</b>), the curves in dashed line (TIC2) have been obtained by increasing the voltage and those in solid line (TIC1) by decreasing the voltage.</p> Full article ">Figure A1
<p>Comparison between the exact profile <math display="inline"><semantics> <mrow> <mi>β</mi> <mo>(</mo> <mi>z</mi> <mo>)</mo> </mrow> </semantics></math> (solid line) obtained by solving Equation (<a href="#FD27-crystals-13-00957" class="html-disp-formula">A6</a>) with <math display="inline"><semantics> <mrow> <mi>B</mi> <mo>=</mo> <mn>0.56</mn> <mspace width="3.33333pt"/> </mrow> </semantics></math>T and the analytical profile (dashed line) found at <math display="inline"><semantics> <mrow> <mi>B</mi> <mo>=</mo> <mn>0</mn> </mrow> </semantics></math> when <math display="inline"><semantics> <mrow> <msub> <mi>β</mi> <mi>m</mi> </msub> <mo>=</mo> <mn>0</mn> </mrow> </semantics></math> [Equation (<a href="#FD17-crystals-13-00957" class="html-disp-formula">17</a>)]. The sample thickness is <math display="inline"><semantics> <mrow> <mi>d</mi> <mo>=</mo> <mn>9</mn> <mtext> </mtext> <mi mathvariant="sans-serif">μ</mi> </mrow> </semantics></math>m and the cholesteric pitch is <math display="inline"><semantics> <mrow> <mi>P</mi> <mo>=</mo> <mn>10</mn> <mtext> </mtext> <mi mathvariant="sans-serif">μ</mi> </mrow> </semantics></math>m.</p> Full article ">Figure A2
<p>Numerical solutions of Equations (<a href="#FD8-crystals-13-00957" class="html-disp-formula">8</a>)–(<a href="#FD10-crystals-13-00957" class="html-disp-formula">10</a>) at <math display="inline"><semantics> <mrow> <mi>d</mi> <mo>=</mo> <mn>9</mn> <mtext> </mtext> <mi mathvariant="sans-serif">μ</mi> </mrow> </semantics></math>m and <math display="inline"><semantics> <mrow> <mo>Δ</mo> <mi>V</mi> <mo>=</mo> <mn>0.1</mn> <mtext> </mtext> </mrow> </semantics></math>Vrms calculated by taking <math display="inline"><semantics> <mrow> <msub> <mi>V</mi> <mi>i</mi> </msub> <mo>=</mo> <mn>0</mn> </mrow> </semantics></math> (blue curves) and <math display="inline"><semantics> <mrow> <mo>Δ</mo> <msub> <mi>V</mi> <mi>i</mi> </msub> <mo>=</mo> <mn>0.5</mn> <mtext> </mtext> </mrow> </semantics></math>Vrms (red curves). (<b>a</b>–<b>c</b>) Time evolution of the angles <math display="inline"><semantics> <mi>α</mi> </semantics></math> and <math display="inline"><semantics> <mi>β</mi> </semantics></math> and of the electric field <span class="html-italic">E</span> in the middle of the sample; (<b>d</b>–<b>f</b>) <span class="html-italic">z</span>-profiles of angles <math display="inline"><semantics> <mi>α</mi> </semantics></math> and <math display="inline"><semantics> <mi>β</mi> </semantics></math> and of the electric field <span class="html-italic">E</span> in steady state. In graphs (<b>d</b>–<b>f</b>), the red curves have been shifted slightly upwards to become visible. In (<b>f</b>) the green line shows the average electric field <math display="inline"><semantics> <mrow> <mi>V</mi> <mo>/</mo> <mi>d</mi> </mrow> </semantics></math>.</p> Full article ">Figure A3
<p>Numerical solutions at <math display="inline"><semantics> <mrow> <mi>d</mi> <mo>=</mo> <mn>9.5</mn> <mtext> </mtext> <mi mathvariant="sans-serif">μ</mi> </mrow> </semantics></math>m and <math display="inline"><semantics> <mrow> <mo>Δ</mo> <mi>V</mi> <mo>=</mo> <mn>0.01</mn> <mtext> </mtext> </mrow> </semantics></math>Vrms calculated by taking <math display="inline"><semantics> <mrow> <msub> <mi>V</mi> <mi>i</mi> </msub> <mo>=</mo> <mn>0</mn> </mrow> </semantics></math> (blue curves) and <math display="inline"><semantics> <mrow> <mo>Δ</mo> <msub> <mi>V</mi> <mi>i</mi> </msub> <mo>=</mo> <mn>0.5</mn> </mrow> </semantics></math> (red curves). (<b>a</b>–<b>c</b>) Time evolution of the angles <math display="inline"><semantics> <mi>α</mi> </semantics></math> and <math display="inline"><semantics> <mi>β</mi> </semantics></math> and of the electric field <span class="html-italic">E</span> in the middle of the sample; (<b>d</b>–<b>f</b>) <span class="html-italic">z</span>-profiles of angles <math display="inline"><semantics> <mi>α</mi> </semantics></math> and <math display="inline"><semantics> <mi>β</mi> </semantics></math> and of the electric field <span class="html-italic">E</span> in steady state. In (<b>f</b>) the green line shows the average electric field <math display="inline"><semantics> <mrow> <mi>V</mi> <mo>/</mo> <mi>d</mi> </mrow> </semantics></math>. In this example, two different stationary solution are found. The blue one is stable, and the red one metastable.</p> Full article ">Figure A4
<p>Amplitude <math display="inline"><semantics> <msub> <mi>α</mi> <mi>m</mi> </msub> </semantics></math> of the TIC as a function of the voltage difference <math display="inline"><semantics> <mrow> <mo>Δ</mo> <mi>V</mi> <mo>=</mo> <mi>V</mi> <mo>−</mo> <msub> <mi>V</mi> <mrow> <mi>t</mi> <mi>h</mi> </mrow> </msub> </mrow> </semantics></math> calculated at different thicknesses: <math display="inline"><semantics> <mrow> <mi>d</mi> <mo>=</mo> <mn>9</mn> <mtext> </mtext> <mi mathvariant="sans-serif">μ</mi> </mrow> </semantics></math>m (<b>a</b>); <math display="inline"><semantics> <mrow> <mi>d</mi> <mo>=</mo> <mn>9.3</mn> <mtext> </mtext> <mi mathvariant="sans-serif">μ</mi> </mrow> </semantics></math>m (<b>b</b>); <math display="inline"><semantics> <mrow> <mi>d</mi> <mo>=</mo> <mn>9.39</mn> <mtext> </mtext> <mi mathvariant="sans-serif">μ</mi> </mrow> </semantics></math>m (<b>c</b>); <math display="inline"><semantics> <mrow> <mi>d</mi> <mo>=</mo> <mn>9.5</mn> <mtext> </mtext> <mi mathvariant="sans-serif">μ</mi> </mrow> </semantics></math>m (<b>d</b>); <math display="inline"><semantics> <mrow> <mi>d</mi> <mo>=</mo> <mn>9.7</mn> <mtext> </mtext> <mi mathvariant="sans-serif">μ</mi> </mrow> </semantics></math>m (<b>e</b>) and <math display="inline"><semantics> <mrow> <mi>d</mi> <mo>=</mo> <mn>10</mn> <mtext> </mtext> <mi mathvariant="sans-serif">μ</mi> </mrow> </semantics></math>m (<b>f</b>). In (<b>d</b>–<b>f</b>), the dotted-dashed line indicates the value of <math display="inline"><semantics> <mrow> <mo>Δ</mo> <mi>V</mi> </mrow> </semantics></math> at which the two solutions have the same energy. On the left (resp., right) of this line, the most stable solution is that of low (resp., large) amplitude.</p> Full article ">Figure A5
<p>Phase diagram in the vicinity of the tricritical point (TCP). On the left of TCP, two transitions are observed as a function of the voltage: a second order transition between the HN and a TIC of small amplitude and a first order transition between two TIC of non-zero amplitudes. This transition ends at the critical point CP (cusp point). On the right of the tricritical point, a first order transition between the HN and a TIC of large amplitude is observed.</p> Full article ">Figure A6
<p>Maximal tilt angle (<b>a</b>) and energy (<b>b</b>) of TIC1 and TIC2 solutions as a function of the thickness calculated on the spinodal line of the HN when <math display="inline"><semantics> <mrow> <mi>V</mi> <mo>=</mo> <msub> <mi>V</mi> <mrow> <mi>t</mi> <mi>h</mi> </mrow> </msub> </mrow> </semantics></math>. The two solutions coexist between <math display="inline"><semantics> <msubsup> <mi>d</mi> <mn>1</mn> <mo>−</mo> </msubsup> </semantics></math> and <math display="inline"><semantics> <msubsup> <mi>d</mi> <mn>1</mn> <mo>+</mo> </msubsup> </semantics></math> and have the same energy at <math display="inline"><semantics> <mrow> <mi>d</mi> <mo>=</mo> <msub> <mi>d</mi> <mn>1</mn> </msub> </mrow> </semantics></math>. When <math display="inline"><semantics> <mrow> <mi>d</mi> <mo>&lt;</mo> <msub> <mi>d</mi> <mn>1</mn> </msub> </mrow> </semantics></math>, TIC1 forms (TIC parallel to <span class="html-italic">B</span>), while TIC2 is preferred when <math display="inline"><semantics> <mrow> <mi>d</mi> <mo>&gt;</mo> <msub> <mi>d</mi> <mn>1</mn> </msub> </mrow> </semantics></math> (TIC perpendicular to <span class="html-italic">B</span>).</p> Full article ">
15 pages, 3199 KiB  
Article
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 3 | Viewed by 1364
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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Figure 1
<p>Synthesis of TPABPOP-1.</p> Full article ">Figure 2
<p>(<b>a</b>) FTIR spectra of TPABPOP−1 and TPABPOP−1/Pb(II), (<b>b</b>) <sup>13</sup>C CP/MAS NMR, (<b>c</b>) N<sub>2</sub> adsorption–desorption isotherm, and (<b>d</b>) pore size distribution of TPABPOP−1.</p> Full article ">Figure 3
<p>(<b>a</b>) TGA analysis and (<b>b</b>,<b>c</b>) SEM image of TPABPOP-1.</p> Full article ">Figure 4
<p>(<b>a</b>) XPS analysis for wide-scan spectrum of TPABPOP-1 and TPABPOP-1/Pb(II), (<b>b</b>) high-resolution C 1s, (<b>c</b>) N 1s, and (<b>d</b>) Pb 4f.</p> Full article ">Figure 5
<p>(<b>a</b>) Uptake capacity with respect to pH and (<b>b</b>) adsorbent dose.</p> Full article ">Figure 6
<p>(<b>a</b>) Uptake capacity with respect to contact time, (<b>b</b>) Pb(II) concentration, and (<b>c</b>) temperature.</p> Full article ">Figure 7
<p>(<b>a</b>) adsorption kinetic and (<b>b</b>) isotherm models for uptake of Pb(II) over TPABPOP-1.</p> Full article ">Figure 8
<p>Proposed mechanism of Pb(II) adsorption onto TPABPOP-1.</p> Full article ">
15 pages, 6688 KiB  
Article
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 1185
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 τf value of ~−4.6 ppm/°C, a moderate εr 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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Figure 1
<p>(<b>a</b>) Room-temperature XRD patterns of the (<span class="html-italic">n</span> + 1)SrO − <span class="html-italic">n</span>CeO<sub>2</sub> (<span class="html-italic">n</span> = 2) ceramics sintered at different temperatures for 4 h; (<b>b</b>) 2<span class="html-italic">θ</span> = 28–31° partially enlarged view.</p> Full article ">Figure 2
<p>(<b>a</b>) Room temperature XRD patterns of the <span class="html-italic">x</span>TiO<sub>2</sub>-(1 − x) (SrCeO<sub>3</sub> + Sr<sub>2</sub>CeO<sub>4</sub>) (<span class="html-italic">x</span> = 0.1–0.4) ceramics sintered at 1350 °C and (<b>b</b>) 2<span class="html-italic">θ</span> = 28.5–33° partially enlarged view.</p> Full article ">Figure 3
<p>Raman spectra of SrCeO<sub>3</sub>, Sr<sub>2</sub>CeO<sub>4</sub>, Sr<sub>2</sub>TiO<sub>4</sub> and <span class="html-italic">x</span>TiO<sub>2</sub>-(1 − x) (SrCeO<sub>3</sub> + Sr<sub>2</sub>CeO<sub>4</sub>) (<span class="html-italic">x</span> = 0.0–0.4) ceramics (<b>a</b>) in the range of 50–900 cm<sup>−1</sup> and (<b>b</b>) in the range of 250–450 cm<sup>−1</sup>, sintered at their optimal temperatures for 4 h.</p> Full article ">Figure 4
<p>SEM images of the (<b>a</b>), (<b>b</b>), (<b>c</b>), (<b>d</b>), (<b>e</b>), (<b>f</b>) and (<b>g</b>) correspond to the <span class="html-italic">x</span>TiO<sub>2</sub>-(1 − x) (SrCeO<sub>3</sub> + Sr<sub>2</sub>CeO<sub>4</sub>) (<span class="html-italic">x</span> = 0.0, 0.1, 0.15, 0.2, 0.25, 0.3, 0.4) ceramics sintered at their optimal temperatures for 4 h, respectively.</p> Full article ">Figure 5
<p>(<b>a</b>) SEM images (same as <a href="#crystals-13-00955-f004" class="html-fig">Figure 4</a>a), (<b>b</b>,<b>c</b>) EDS spectra and data of the SrCeO<sub>3</sub> + Sr<sub>2</sub>CeO<sub>4</sub> ceramic sample sintered at 1350 °C for 4 h.</p> Full article ">Figure 6
<p>HRTEM images of the (<b>a</b>,<b>b</b>) SrCeO<sub>3</sub> + Sr<sub>2</sub>CeO<sub>4</sub> ceramic sample; electron diffraction pictures of (<b>c</b>) SrCeO<sub>3</sub> and (<b>d</b>) Sr<sub>2</sub>CeO<sub>4</sub> phases in this sintered sample at 1350 °C.</p> Full article ">Figure 7
<p>(<b>a</b>) SEM images (same as <a href="#crystals-13-00955-f004" class="html-fig">Figure 4</a>d) and (<b>b</b>–<b>d</b>) EDS spectra and data of <span class="html-italic">x</span>TiO<sub>2</sub>-(1-<span class="html-italic">x</span>) (SrCeO<sub>3</sub> + Sr<sub>2</sub>CeO<sub>4</sub>) (<span class="html-italic">x</span> = 0.2) ceramic samples sintered at 1350 °C for 4 h.</p> Full article ">Figure 8
<p>(<b>a</b>) Bulk density and (<b>b</b>) <span class="html-italic">ε</span><sub>r</sub> of the <span class="html-italic">x</span>TiO<sub>2</sub>-(1 − x) (SrCeO<sub>3</sub> + Sr<sub>2</sub>CeO<sub>4</sub>) (<span class="html-italic">x</span> = 0.0–0.4) ceramics sintered at their optimal temperatures for 4 h.</p> Full article ">Figure 9
<p>Complex impedance diagrams, equivalent circuit diagrams and activation energy diagrams of (<b>a</b>,<b>b</b>) the SrCeO<sub>3</sub> + Sr<sub>2</sub>CeO<sub>4</sub> and (<b>c</b>,<b>d</b>) the <span class="html-italic">x</span>TiO<sub>2</sub>-(1 − x) (SrCeO<sub>3</sub> + Sr<sub>2</sub>CeO<sub>4</sub>) (<span class="html-italic">x</span> = 0.2) ceramics sintered at their optimal temperatures for 4 h.</p> Full article ">Figure 10
<p><span class="html-italic">Q</span> × <span class="html-italic">f</span> and τ<span class="html-italic"><sub>f</sub></span> values for the <span class="html-italic">x</span>TiO<sub>2</sub>-(1 − x) (SrCeO<sub>3</sub> + Sr<sub>2</sub>CeO<sub>4</sub>) (<span class="html-italic">x</span> = 0.0–0.4) ceramics sintered at their optimal temperatures for 4 h.</p> Full article ">
14 pages, 5284 KiB  
Article
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 1530
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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Figure 1

Figure 1
<p>Schematic representation of the synthesis and therapeutic application of the CeO<sub>2</sub>/Ce<sub>3</sub>NbO<sub>7</sub>/g-C<sub>3</sub>N<sub>4</sub> NCs. The modifications of g-C<sub>3</sub>N<sub>4</sub> to the Ce<sub>3</sub>NbO<sub>7</sub> hollow spheres synergistically accomplish PTT/CDT to treat LC.</p> Full article ">Figure 2
<p>Characterization of CeO<sub>2</sub>/Ce<sub>3</sub>NbO<sub>7</sub>/g-C<sub>3</sub>N<sub>4</sub> NCs, (<b>a</b>,<b>b</b>) show TEM images of CeO<sub>2</sub>/Ce<sub>3</sub>NbO<sub>7</sub> hollow spheres; (<b>c</b>,<b>d</b>) g-C<sub>3</sub>N<sub>4</sub>; (<b>e</b>,<b>f</b>) CeO<sub>2</sub>/Ce<sub>3</sub>NbO<sub>7</sub>/g-C<sub>3</sub>N<sub>4</sub> NCs; (<b>g</b>) elemental mapping images of CeO<sub>2</sub>/Ce<sub>3</sub>NbO<sub>7</sub>/g-C<sub>3</sub>N<sub>4</sub> NCs; (<b>h</b>) cerium (Ce); (<b>i</b>) niobium (Nb); (<b>j</b>) carbon (C); (<b>k</b>) nitrogen (N); (<b>l</b>) oxygen (O); (<b>m</b>) EDX mapping of CeO<sub>2</sub>/Ce<sub>3</sub>NbO<sub>7</sub>/g-C<sub>3</sub>N<sub>4</sub> NCs; (<b>n</b>) elemental composition and weight percentage.</p> Full article ">Figure 3
<p>XRD patterns of CeO<sub>2</sub>/Ce<sub>3</sub>NbO<sub>7</sub>, g-C<sub>3</sub>N<sub>4</sub>, and CeO<sub>2</sub>/Ce<sub>3</sub>NbO<sub>7</sub>/g-C<sub>3</sub>N<sub>4</sub> NCs (<b>a</b>); FT-IR spectra of CeO<sub>2</sub>/Ce<sub>3</sub>NbO<sub>7</sub>, g-C<sub>3</sub>N<sub>4</sub>, and CeO<sub>2</sub>/Ce<sub>3</sub>NbO<sub>7</sub>/g-C<sub>3</sub>N<sub>4</sub> NCs (<b>b</b>), and (<b>c</b>) UV-visible spectrum of CeO<sub>2</sub>/Ce<sub>3</sub>NbO<sub>7</sub>, g-C<sub>3</sub>N<sub>4</sub>, and CeO<sub>2</sub>/Ce<sub>3</sub>NbO<sub>7</sub>/g-C<sub>3</sub>N<sub>4</sub> NCs.</p> Full article ">Figure 4
<p>XPS spectra of the CeO<sub>2</sub>/Ce<sub>3</sub>NbO<sub>7</sub>/g-C<sub>3</sub>N<sub>4</sub> NCs. (<b>a</b>) The XPS survival spectrum. (<b>b</b>–<b>e</b>) The core level spectrum of Ce 3d, Nb 3d, C 1s, and O 1 s, respectively.</p> Full article ">Figure 5
<p>In vitro photothermal responses of the CeO<sub>2</sub>/Ce<sub>3</sub>NbO<sub>7</sub>/g-C<sub>3</sub>N<sub>4</sub> NCs (those Chinese characters in the figure represents the respective temperature range): (<b>a</b>) temperature changes of the CeO<sub>2</sub>/Ce<sub>3</sub>NbO<sub>7</sub>/g-C<sub>3</sub>N<sub>4</sub> NCs aqueous solutions at different concentrations in 1 W/cm<sup>2</sup>. (<b>b</b>) Thermal stability of the synthesized NCs under irradiation with a 1 W/cm<sup>2</sup> NIR laser source. (<b>c</b>) Infrared thermal images of the NCs at a power density of 1 W/cm<sup>2</sup>.</p> Full article ">Figure 6
<p>UV-Visible spectra of MB + H<sub>2</sub>O and MB + H<sub>2</sub>O<sub>2</sub> (<b>a</b>). Degradation plot of MB+ CeO<sub>2</sub>/Ce<sub>3</sub>NbO<sub>7</sub>/g-C<sub>3</sub>N<sub>4</sub> NCs at different time intervals (0 and 20 min) (<b>b</b>). The MB degradation of the NCs without laser for different time durations (<b>c</b>). The PTT/CDT of MB degradation efficiency of NCs in the presence of laser (<b>d</b>).</p> Full article ">Figure 7
<p>In vitro cytotoxicity analysis of L929 cells (<b>a</b>); synergistic therapeutic application of CeO<sub>2</sub>/Ce<sub>3</sub>NbO<sub>7</sub>/g-C<sub>3</sub>N<sub>4</sub> NCs towards HepG2 cells with the incorporation of 808 nm of NIR laser at pH = 7.4 (<b>b</b>); cytotoxicity analysis of the CeO<sub>2</sub>/Ce<sub>3</sub>NbO<sub>7</sub>/g-C<sub>3</sub>N<sub>4</sub> NCs + laser at pH = 6.5 (<b>c</b>). Statistical analysis (*, **) was performed by student’s <span class="html-italic">t</span>-test method.</p> Full article ">
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