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Crystals, Volume 9, Issue 10 (October 2019) – 60 articles

Cover Story (view full-size image): A new crystalline phase of betaxolol (BE_IV), an API belonging to the class of β1-adrenergic blocking agents, is reported on and compared with the already known BE_I form. In both polymorphs, the most significant interaction is the H-bonds involving the OH group as a donor and the NH as an acceptor, while the interaction where OH works as the acceptor (NH acts as the donor) is definitely less important. The resulting H-bond patterns are, however, different: alternate R2,2(10) a > a (OH donors) and R2,2(10) b > b (OH acceptors) in BE_I vs. alternate R4,4 (8) a > b > a > b (OH donors) and R2,2 (10) b > b (OH acceptor) in BE_IV. View this paper
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Article
A Study on the Effect of Ceramic Polishing Powder on the Nucleation and Growth of Hydrates in Cement Paste
Crystals 2019, 9(10), 545; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9100545 - 22 Oct 2019
Cited by 2 | Viewed by 908
Abstract
The production of cement leads to a large amount of CO2 emission. Using industrial waste slag, such as ceramic polishing powder (PP), to replace part of Portland cement can reduce the pollution caused by the cement industry and solid waste disposal. In [...] Read more.
The production of cement leads to a large amount of CO2 emission. Using industrial waste slag, such as ceramic polishing powder (PP), to replace part of Portland cement can reduce the pollution caused by the cement industry and solid waste disposal. In order to use PP as a replacement for cement, its effects on the properties of cement paste need to be clarified. In this study, the effect of PP on the nucleation and growth of hydrates in cement paste at very early ages was investigated. Quartz was used as a reference. The interactions of their surface with various ions in cement paste solution, which has an important effect on the nucleation and growth of hydrates, were studied by using the zeta potential test. The morphology of the nucleus and crystal of hydrates was investigated by using SEM. The zeta potential measurements showed that the affinity of the surface of PP and quartz to ions in the pore solution of cement paste is similar. The image of SEM indicated that there is also not much difference in the crystallization of hydrates on the surfaces of PP and quartz. These evidences suggested that PP has similar surface charge properties as quartz, and its effects on the properties of cement paste are the same as that of quartz. From the viewpoint of the effect on very early hydration, PP can be used in cement paste, similar to quartz power. Full article
(This article belongs to the Special Issue Crystal Nucleation Kinetics)
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Article
Internalization of Phospholipid-Coated Gold Nanoparticles
Crystals 2019, 9(10), 544; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9100544 - 21 Oct 2019
Viewed by 1125
Abstract
Gold nanoparticles are used in health-related research; however, their effectiveness appears to depend on how well they are internalized and where they are destined to travel. Internalization in cells is efficient if the gold nanoparticles are biocompatible, where one possible pathway of cell [...] Read more.
Gold nanoparticles are used in health-related research; however, their effectiveness appears to depend on how well they are internalized and where they are destined to travel. Internalization in cells is efficient if the gold nanoparticles are biocompatible, where one possible pathway of cell entry and processing is clathrin-mediated endocytosis. In this work we studied the co-localization of phospholipid-coated gold nanoparticles (PCAuNPs) with markers of the endocytic pathway (Rab and LAMP-1 proteins) in C2C12 and A549 cells and found that the internalization was consistent with clathrin-mediated endocytosis and was cell type dependent. We further found that the time evolution of uptake and disposal of these PCAuNPs was similar for both cell types, but aggregation was more significant in A549 cells. Our results support the use of these PCAuNPs as models for potential drug delivery platforms. Full article
(This article belongs to the Special Issue Synthesis and Investigation of Gold Nanoparticles)
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Article
In-plane Switching Deformed Helix Ferroelectric Liquid Crystal Display Cells
Crystals 2019, 9(10), 543; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9100543 - 21 Oct 2019
Cited by 2 | Viewed by 1885
Abstract
In-plane electro-optical switching (IPS) is a natural feature of a conventional planar-aligned display cell based on the deformed helix ferroelectric liquid crystal effect (DHFLC-effect) with a sub-wavelength helix pitch, if the tilt angle is close to 40 degrees. Full article
(This article belongs to the Special Issue Ferroelectric and Ferromagnetic Liquid Crystals)
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Article
Localized Conical Edge Modes of Higher Orders in Photonic Liquid Crystals
Crystals 2019, 9(10), 542; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9100542 - 20 Oct 2019
Cited by 4 | Viewed by 801
Abstract
Most studies of the localized edge (EM) and defect (DM) modes in cholesteric liquid crystals (CLC) are related to the localized modes in a collinear geometry, i.e., for the case of light propagation along the spiral axis. It is due to the fact [...] Read more.
Most studies of the localized edge (EM) and defect (DM) modes in cholesteric liquid crystals (CLC) are related to the localized modes in a collinear geometry, i.e., for the case of light propagation along the spiral axis. It is due to the fact that all photonic effects in CLC are most pronounced just for a collinear geometry, and also partially due to the fact that a simple exact analytic solution of the Maxwell equations is known for a collinear geometry, whereas for a non-collinear geometry, there is no exact analytic solution of the Maxwell equations and a theoretical description of the experimental data becomes more complicated. It is why in papers related to the localized modes in CLC for a non-collinear geometry and observing phenomena similar to the case of a collinear geometry, their interpretation is not so clear. Recently, an analytical theory of the conical modes (CEM) related to a first order of light diffraction was developed in the framework of the two-wave dynamic diffraction theory approximation ensuring the results accuracy of order of δ, the CLC dielectric anisotropy. The corresponding experimental results are reasonably well described by this theory, however, some numerical problems related to the CEM polarization properties remain. In the present paper, an analytical theory of a second order diffraction CEM is presented with results that are qualitatively similar to the results for a first order diffraction order CEM and have the accuracy of order of δ2, i.e., practically exact. In particular, second order diffraction CEM polarization properties are related to the linear σ and π polarizations. The known experimental results on the CEM are discussed and optimal conditions for the second order diffraction CEM observations are formulated. Full article
(This article belongs to the Special Issue Localized Optical Modes in Liquid Crystals)
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Article
Crystal-Chemical Properties of Synthetic Almandine-Pyrope Solid Solution by X-Ray Single-Crystal Diffraction and Raman Spectroscopy
Crystals 2019, 9(10), 541; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9100541 - 19 Oct 2019
Cited by 2 | Viewed by 1207
Abstract
Crystal-chemical properties of synthetic Almandine-Pyrope (Alm-Pyr) solid solutions were investigated by X-ray single-crystal diffraction and Raman spectroscopy. Garnet solid solution with different compositions were synthesized from powder at 4.0 GPa and annealed at 1200 °C for 48 h by a multi-anvil pressure apparatus. [...] Read more.
Crystal-chemical properties of synthetic Almandine-Pyrope (Alm-Pyr) solid solutions were investigated by X-ray single-crystal diffraction and Raman spectroscopy. Garnet solid solution with different compositions were synthesized from powder at 4.0 GPa and annealed at 1200 °C for 48 h by a multi-anvil pressure apparatus. Garnet crystals with different sizes (about 60–1000 μm) were obtained from synthesis. The results of X-ray single-crystal diffraction show that the unit cell constants decrease with increasing Pyr contents in the synthetic Alm-Pyr crystals due to the smaller ionic radius of Mg2+ in eightfold coordination than that of Fe2+. The data exhibit obviously positive deviations from ideal mixing volumes across the Alm-Pyr join which may be caused by the distortion of the SiO4 tetrahedron. Moreover, the significant decrease in the average M-O bond length and volume of the [MgO8]/[FeO8] dodecahedron with increasing Pyr contents are the most important factors to the decrease in the Alm-Pyr crystal unit cell constant and volume. On the other hand, selected bond distances (average <M-O>, <Al-O>, and <D-O> distances) have a linear correlation with the unit-cell parameter, but the <Si-O> distance has nonlinear correlation. With increasing the unit-cell parameter, the average <M-O> distance increases significantly, followed by the average <D-O> and <Al-O> distances. While the <Si-O> distance changes negligibly further confirming the conclusion that the significant decrease of the average M-O bond length of the [MgO8]/[FeO8] dodecahedron with increasing Pyr contents are the most important factors to the decrease in the Alm-Pyr crystal unit cell volume. In the Raman spectra collected for the Alm-Pyr solid solutions, Raman vibration mode assignments indicate that the Raman vibrational spectra change along the Alm-Pyr binary solution. The mode frequencies of Si-O stretching, Si-O bending, and the rotation of the SiO4-tetrahedron (R(SiO4)) decrease linearly, while the translational modes of the SiO4-tetrahedron (T(SiO4)) increase with increasing Alm contents. Full article
(This article belongs to the Special Issue High Pressure Synthesis in Crystalline Materials)
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Editorial
Ice Crystals
Crystals 2019, 9(10), 540; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9100540 - 19 Oct 2019
Viewed by 889
Abstract
The special issue on “Ice Crystals” includes seven contributed papers, which give the wide varieties of topics related to ice crystals. They focus on the interface structure of ice, the physical properties of hydrate crystals and the freezing properties of water controlled by [...] Read more.
The special issue on “Ice Crystals” includes seven contributed papers, which give the wide varieties of topics related to ice crystals. They focus on the interface structure of ice, the physical properties of hydrate crystals and the freezing properties of water controlled by antifreeze proteins. The present issue can be considered as a status report reviewing the research that has been made recently on ice crystals. These papers provide research information about the recent development of ice crystal research to readers. Full article
(This article belongs to the Special Issue Ice Crystals)
Article
Ambipolar Transport in Methylammonium Lead Iodide Thin Film Transistors
Crystals 2019, 9(10), 539; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9100539 - 19 Oct 2019
Cited by 11 | Viewed by 1511
Abstract
We report clear room temperature ambipolar transport in ambient-air processed methylammonium lead iodide (MAPbI3) thin-film transistors (TFTs) with aluminum oxide gate-insulators and indium-zinc-oxide source/drain electrodes. The high ionicity of the MAPbI3 leads to p-type and n-type self-doping, and depending on [...] Read more.
We report clear room temperature ambipolar transport in ambient-air processed methylammonium lead iodide (MAPbI3) thin-film transistors (TFTs) with aluminum oxide gate-insulators and indium-zinc-oxide source/drain electrodes. The high ionicity of the MAPbI3 leads to p-type and n-type self-doping, and depending on the applied bias we show that simultaneous or selective transport of electrons and/or holes is possible in a single MAPbI3 TFT. The electron transport (n-type), however, is slightly more pronounced than the hole transport (p-type), and the respective channel resistances range from 5–11 and 44–55 MΩ/μm. Both p-type and n-type TFTs show good on-state characteristics for low driving voltages. It is also shown here that the on-state current of the n-type and p-type TFTs is highest in the slightly PbI2-rich and MAI-rich films, respectively, suggesting controllable n-type or p-type transport by varying precursor ratio. Full article
(This article belongs to the Special Issue Advances in Thin Film Materials and Devices)
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Article
A Note for Probabilistic Model of Polymer Crystallization in Temperature Gradients
Crystals 2019, 9(10), 538; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9100538 - 19 Oct 2019
Viewed by 886
Abstract
A polymer crystallization kinetics model is the most important way to characterize the crystallization rate of polymers. Because polymers are poor heat conductors, the cooling of thick-walled shapes results in temperature gradients. Piorkowska (Piorkowska, E. J. Appl. Polym. Sci., 2002, 86: 1351–1362.) derived [...] Read more.
A polymer crystallization kinetics model is the most important way to characterize the crystallization rate of polymers. Because polymers are poor heat conductors, the cooling of thick-walled shapes results in temperature gradients. Piorkowska (Piorkowska, E. J. Appl. Polym. Sci., 2002, 86: 1351–1362.) derived the probabilistic analytical model of polymer crystallization in temperature gradients based on the Avrami equation. However, there are some misunderstandings when using this model. Here, isotactic polypropylene (iPP) is chosen as a model polymer and its crystallization is studied in a temperature gradient field. Based on the results of the Monte Carlo method, the probabilistic model methodology is discussed. The results show that when the product has a large temperature gradient and a large temperature difference, the probabilistic model cannot be used directly; instead, it is necessary to use the average probabilistic model. This means that the sample should be divided into several smaller parts and the probabilistic model used separately for each small part. The values are then averaged to obtain the mean conversion degree of the melt into spherulites for the whole product. The effects of the division number are also discussed. The goal of the present paper is to better understand the polymer crystallization kinetics model in terms of temperature gradients. Full article
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Article
Characterization and Structural Determination of Cold-Adapted Monodehydroascorbate Reductase, MDHAR, from the Antarctic Hairgrass Deschampsia Antarctica
Crystals 2019, 9(10), 537; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9100537 - 18 Oct 2019
Cited by 3 | Viewed by 1120
Abstract
Ascorbic acid (AsA) is an abundant component of plants and acts as a strong and active antioxidant. In order to maintain the antioxidative capacity of AsA, the rapid regeneration of AsA is regulated by dehydroascorbate reductase (DHAR) and monodehydroascorbate reductase (MDHAR). To understand [...] Read more.
Ascorbic acid (AsA) is an abundant component of plants and acts as a strong and active antioxidant. In order to maintain the antioxidative capacity of AsA, the rapid regeneration of AsA is regulated by dehydroascorbate reductase (DHAR) and monodehydroascorbate reductase (MDHAR). To understand how MDHAR functions under extreme temperature conditions, this study characterized its biochemical properties and determined the crystal structure of MDHAR from the Antarctic hairgrass Deschampsia antarctica (DaMDHAR) at 2.2 Å resolution. This allowed for a structural comparison with the mesophilic MDHAR from Oryza sativa L. japonica (OsMDHAR). In the functional analysis, yeast cells expressing DaMDHAR were tolerant to freezing and thawing cycles. It is possible that the expression of DaMDHAR in yeast enhanced the tolerance for ROS-induced abiotic stress. Full article
(This article belongs to the Special Issue Crystallographic Studies of Enzymes)
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Article
Investigations on the Solubility of Vortioxetine Based on X-ray Structural Data and Crystal Contacts
Crystals 2019, 9(10), 536; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9100536 - 18 Oct 2019
Cited by 1 | Viewed by 872
Abstract
Investigation on the solid-state pharmaceutical chemistry has been known as an intriguing strategy to not only modify the physicochemical properties of drugs but also expand the solid form landscape. Vortioxetine (VOT) is an effective but poorly soluble antidepressant. To improve the solubility of [...] Read more.
Investigation on the solid-state pharmaceutical chemistry has been known as an intriguing strategy to not only modify the physicochemical properties of drugs but also expand the solid form landscape. Vortioxetine (VOT) is an effective but poorly soluble antidepressant. To improve the solubility of vortioxetine and expand possible solid forms, in this paper, four novel solid forms of vortioxetine with dihydroxybenzoic acids (VOT-23BA, VOT-24BA-TOL, VOT-25BA, and VOT-26BA, 23BA = 2,3-dihydroxybenzoic acid, 24BA = 2,4-dihydroxybenzoic acid, 25BA = 2,5-dihydroxybenzoic acid, 26BA = 2,6-dihydroxybenzoic acid, and TOL = toluene) were synthesized first by a solvent evaporation method and then characterized by single-crystal X-ray diffraction (SCXRD), thermal, and XRD techniques. VOT-24BA-TOL, VOT-25BA, and VOT-26BA, showed similar [2+2] tetrameric R 4 4 (12) hydrogen bonds by acid-piperazine heterosynthon. In the VOT-23BA-H2O salt, the VOT cation and 23BA anion interacted through protonated piperazine-hydroxyl N-H···O hydrogen bonds, not protonated piperazine-deprotonated carboxylic acid N-H···O hydrogen bonds. Solubility studies were carried out in purified water and it was found that the VOT-23BA-H2O, VOT-25BA, and VOT-26BA salts exhibited an increase in water compared to pure VOT. The solubility of the stabilized salt formations followed the order of VOT-25BA > VOT-26BA > VOT-23BA-H2O in purified water. Full article
(This article belongs to the Section Crystal Engineering)
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Review
Raman Scattering in Non-Stoichiometric Lithium Niobate Crystals with a Low Photorefractive Effect
Crystals 2019, 9(10), 535; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9100535 - 17 Oct 2019
Cited by 6 | Viewed by 1291
Abstract
Raman spectra of lithium niobate single crystals strongly doped by zinc and magnesium, it has been established, contain low-intense bands with frequencies 209, 230, 298, 694, and 880 cm−1. Ab ignition calculations fail to attribute these bands to fundamental vibrations of [...] Read more.
Raman spectra of lithium niobate single crystals strongly doped by zinc and magnesium, it has been established, contain low-intense bands with frequencies 209, 230, 298, 694, and 880 cm−1. Ab ignition calculations fail to attribute these bands to fundamental vibrations of A2 symmetry type unambiguously. Such vibrations are prohibited by the selection rules in the space group C3V6 (R3c). Ab initio calculations also proved that low-intense “extra” bands with frequencies 104 and 119 cm−1 definitely do not correspond to vibrations of A2 symmetry type. We have paid special attention to these extra bands that appear in LiNbO3 single crystals Raman spectra despite the fact that they are prohibited by the selection rules. In order to do so, we have studied a number of lithium niobate single crystals, both nominally pure and doped, by Raman spectroscopy. We have assumed that some “extra” bands correspond to two-particle states of acoustic phonons with a total wave vector equal to zero. We have also detected a Zn concentration area (0.05–0.94 mol.% ZnO in a crystal) where doped crystal structure is more ordered: The order of alternation of the main, doping cations, and vacancies along the polar axis is increased, and oxygen octahedra are less distorted. Full article
(This article belongs to the Special Issue Raman Spectroscopy of Crystals)
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Brief Report
The Crystal Structure of the Plasmodium falciparum PdxK Provides an Experimental Model for Pro-Drug Activation
Crystals 2019, 9(10), 534; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9100534 - 17 Oct 2019
Viewed by 981
Abstract
Pyridoxine/pyridoxal kinase (PdxK), belongs to the ribokinase family and is involved in the vitamin B6 salvage pathway by phosphorylating 5-pyridoxal (PL) into an active form. In the human malaria parasite, Plasmodium falciparum, PfPdxK functions to salvage vitamin B6 from both itself [...] Read more.
Pyridoxine/pyridoxal kinase (PdxK), belongs to the ribokinase family and is involved in the vitamin B6 salvage pathway by phosphorylating 5-pyridoxal (PL) into an active form. In the human malaria parasite, Plasmodium falciparum, PfPdxK functions to salvage vitamin B6 from both itself and its host. Here, we report the crystal structure of PfPdxK from P. falciparum in complex with a non-hydrolyzable ATP analog (AMP-PNP) and PL. As expected, the fold is retained and both AMP-PNP and PL occupy the same binding sites when compared to the human ortholog. However, our model allows us to identify a FIxxIIxL motif at the C terminus of the disordered repeat motif (XNXH)m that is implicated in binding the WD40 domain and may provide temporal control of PfPdxK through an interaction with a E3 ligase complex. Furthermore, molecular docking approaches based on our model allow us to explain differential PfPdxK phosphorylation and activation of a novel class of potent antimalarials (PT3, PT5 and PHME), providing a basis for further development of these compounds. Finally, the structure of PfPdxK provides a high-quality model for a better understanding of vitamin B6 synthesis and salvage in the parasite. Full article
(This article belongs to the Special Issue Protein Crystallography)
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Article
Trial Direct Phasing Calculation of A Thyroid Hormone Receptor Alpha Structure (4LNW)
Crystals 2019, 9(10), 533; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9100533 - 16 Oct 2019
Viewed by 821
Abstract
A thyroid receptor alpha structure (PDB ID: 4LNW) was studied for ab initio phasing. With the diffraction intensity data, protein sequence, and ligand structure as the only input, a high-resolution structure was successfully reconstructed by using an iterative projective method based on the [...] Read more.
A thyroid receptor alpha structure (PDB ID: 4LNW) was studied for ab initio phasing. With the diffraction intensity data, protein sequence, and ligand structure as the only input, a high-resolution structure was successfully reconstructed by using an iterative projective method based on the hybrid input–output (HIO) algorithm. Full article
(This article belongs to the Special Issue Protein Crystallography)
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Article
Molecular Dynamics Simulation of Homo-DNA: The Role of Crystal Packing in Duplex Conformation
Crystals 2019, 9(10), 532; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9100532 - 16 Oct 2019
Cited by 3 | Viewed by 1357
Abstract
The (4′→6′)-linked DNA homolog 2′,3′-dideoxy-β-D-glucopyranosyl nucleic acid (dideoxy-glucose nucleic acid or homo-DNA) exhibits stable self-pairing of the Watson–Crick and reverse-Hoogsteen types, but does not cross-pair with DNA. Molecular modeling and NMR solution studies of homo-DNA duplexes pointed [...] Read more.
The (4′→6′)-linked DNA homolog 2′,3′-dideoxy-β-D-glucopyranosyl nucleic acid (dideoxy-glucose nucleic acid or homo-DNA) exhibits stable self-pairing of the Watson–Crick and reverse-Hoogsteen types, but does not cross-pair with DNA. Molecular modeling and NMR solution studies of homo-DNA duplexes pointed to a conformation that was nearly devoid of a twist and a stacking distance in excess of 4.5 Å. By contrast, the crystal structure of the homo-DNA octamer dd(CGAATTCG) revealed a right-handed duplex with average values for helical twist and rise of ca. 15° and 3.8 Å, respectively. Other key features of the structure were strongly inclined base-pair and backbone axes in the duplex with concomitant base-pair slide and cross-strand stacking, and the formation of a dimer across a crystallographic dyad with inter-duplex base swapping. To investigate the conformational flexibility of the homo-DNA duplex and a potential influence of lattice interactions on its geometry, we used molecular dynamics (MD) simulations of the crystallographically observed dimer of duplexes and an isolated duplex in the solution state. The dimer of duplexes showed limited conformational flexibility, and key parameters such as helical rise, twist, and base-pair slide exhibited only minor fluctuations. The single duplex was clearly more flexible by comparison and underwent partial unwinding, albeit without significant lengthening. Thus, base stacking was preserved in the isolated duplex and two adenosines extruded from the stack in the dimer of duplexes were reinserted into the duplex and pair with Ts in a Hoogsteen mode. Our results confirmed that efficient stacking in homo-DNA seen in the crystal structure of a dimer of duplexes was maintained in the separate duplex. Therefore, lattice interactions did not account for the different geometries of the homo-DNA duplex in the crystal and earlier models that resembled inclined ladders with large base-pair separations that precluded efficient stacking. Full article
(This article belongs to the Special Issue Nucleic Acid Crystallography)
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Article
LED as Transmitter and Receiver of Light: A Simple Tool to Demonstration Photoelectric Effect
Crystals 2019, 9(10), 531; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9100531 - 15 Oct 2019
Cited by 9 | Viewed by 2458
Abstract
The experimental observations of the photoelectric effect show the properties of quantum mechanics of the electromagnetic field. For this reason, this important effect is commonly used as an introductory topic for the study of quantum physics. The “classical” demonstration of the photoelectric effect [...] Read more.
The experimental observations of the photoelectric effect show the properties of quantum mechanics of the electromagnetic field. For this reason, this important effect is commonly used as an introductory topic for the study of quantum physics. The “classical” demonstration of the photoelectric effect is very incisive; unfortunately, the experimental apparatus is not cheap and easy to realize. The typical use of LEDs is as light emitters, but they can be used even as photosensors and, in this case, they are sensitive to wavelengths equal to or shorter than the predominant wavelength it emits. Furthermore, a LED used as detector is sensitive to wavelengths equal to or shorter than the predominant wavelength it emits. This ability of LEDs offers the possibility of developing a simple tool able to demonstrate the photoelectric effect. This paper describes the realization of an economic, simple, easy and safe system to use for the experimental demonstration of the photoelectric effect, based on the LED to LED structure. The paper has educational purposes, oriented towards laboratory teaching activities. Full article
(This article belongs to the Special Issue Recent Advances in Light-Emitting Diodes (LEDs))
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Article
Size and Shape Evolution of GaAsSb-Capped InAs/GaAs Quantum Dots: Dependence on the Sb Content
Crystals 2019, 9(10), 530; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9100530 - 15 Oct 2019
Viewed by 862
Abstract
Capping InAs/GaAs quantum dots (QDs) with a thin GaAsSb layer alters the QDs structural properties, leading to considerable changes in their optical properties. The increase of the Sb content induces a redshift of the emission energies, indicating a change in the buried QDs [...] Read more.
Capping InAs/GaAs quantum dots (QDs) with a thin GaAsSb layer alters the QDs structural properties, leading to considerable changes in their optical properties. The increase of the Sb content induces a redshift of the emission energies, indicating a change in the buried QDs shape and size. The presence of well-defined ground- and excited-state emission bands in all the photoluminescence spectra allow an accurate estimation of the buried QDs size and shape by numerical evaluation and tuning of the theoretical emission energies. For an Sb content below 14%, the QDs are found to have a type I band alignment with a truncated height pyramidal form. However, for higher Sb content (22%), the QDs are present in a full pyramidal shape. The observed behavior is interpreted in terms of increasing prevention of InAs QDs decomposition with increasing the Sb content in the cap layer. Full article
(This article belongs to the Special Issue Nanowires and Quantum Dots for IoT Applications)
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Article
Trinodal Self-Penetrating Nets from Reactions of 1,4-Bis(alkoxy)-2,5-bis(3,2’:6’,3’’-terpyridin-4’-yl)benzene Ligands with Cobalt(II) Thiocyanate
Crystals 2019, 9(10), 529; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9100529 - 15 Oct 2019
Cited by 1 | Viewed by 968
Abstract
The tetratopic ligands 1,4-bis(2-ethylbutoxy)-2,5-bis(3,2’:6’,3’’-terpyridin-4’-yl)benzene (1) and 1,4-bis(3-methylbutoxy)-2,5-bis(3,2’:6’,3’’-terpyridin-4’-yl)benzene (2) have been prepared and characterized by 1H and 13C{1H} NMR, IR, and absorption spectroscopies and mass spectrometry. Reactions of 1 and 2 with cobalt(II) thiocyanate under conditions [...] Read more.
The tetratopic ligands 1,4-bis(2-ethylbutoxy)-2,5-bis(3,2’:6’,3’’-terpyridin-4’-yl)benzene (1) and 1,4-bis(3-methylbutoxy)-2,5-bis(3,2’:6’,3’’-terpyridin-4’-yl)benzene (2) have been prepared and characterized by 1H and 13C{1H} NMR, IR, and absorption spectroscopies and mass spectrometry. Reactions of 1 and 2 with cobalt(II) thiocyanate under conditions of crystal growth at room temperature result in the formation of [{Co(1)(NCS)2}·MeOH·3CHCl3]n and [{Co(2)(NCS)2}·0.8MeOH·1.8CHCl3]n. Single-crystal X-ray diffraction reveals that each crystal lattice consists of a trinodal self-penetrating (62.84)(64.82)(65.8)2 net. The nodes are defined by two independent cobalt centres and the centroids of two crystallographically independent ligands which are topologically equivalent. Full article
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Article
Effect of Pressure Treatment on the Specific Surface Area in Kaolin Group Minerals
Crystals 2019, 9(10), 528; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9100528 - 14 Oct 2019
Cited by 5 | Viewed by 1172
Abstract
Pressure can tailor the properties of a material by changing its atomistic arrangements and/or crystal morphology. We have investigated the changes in the adsorption properties of kaolin group minerals as a function of pressure treatment in the gigapascal range. External pressures have been [...] Read more.
Pressure can tailor the properties of a material by changing its atomistic arrangements and/or crystal morphology. We have investigated the changes in the adsorption properties of kaolin group minerals as a function of pressure treatment in the gigapascal range. External pressures have been applied using a large volume press (LVP) to kaolinite (Al2Si2O5(OH)4) and halloysite (H4Al2O9Si2·2H2O), which represent natural 2D layered and 1D nanowire structures, respectively. Powdered samples have been compressed up to 3 GPa in 1 GPa steps at room temperature and recovered by up to ca. 0.35 g from each pressure step. Brunauer–Emmett–Teller (BET) measurements were conducted using N2 gas to measure the specific surface area, pore size distribution, and pore volume of the pressure-treated samples. As the treatment pressure increased, kaolinite showed an increase in the adsorption behavior from nonpores to mesopores, whereas halloysite responded in an opposite manner to show a decrease in its adsorption capability. We discuss the contrasting effects of pressure-treatment on the two morphologically distinct kaolin group minerals based on field-emission scanning electron microscope (FE-SEM) images measured on each recovered material. We observed that the layers in kaolinite separate into smaller units upon increasing pressure treatment, whereas the tubes in halloysite become flattened, which led to the contrasting changes in surface area. Further study is in progress to compare this effect to when water is used as the pressure-transmitting medium. Full article
(This article belongs to the Special Issue High Pressure Synthesis in Crystalline Materials)
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Article
New Tetragonal ReGa5(M) (M = Sn, Pb, Bi) Single Crystals Grown from Delicate Electrons Changing
Crystals 2019, 9(10), 527; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9100527 - 14 Oct 2019
Viewed by 1212
Abstract
Single crystals of the new Ga-rich phases ReGa~5(Sn), ReGa~5(Pb) and ReGa~5(Bi) were successfully obtained from the flux method. The new tetragonal phases crystallize in the space group P4/mnc (No. 128) with vertex-sharing capped Re2@Ga14 [...] Read more.
Single crystals of the new Ga-rich phases ReGa~5(Sn), ReGa~5(Pb) and ReGa~5(Bi) were successfully obtained from the flux method. The new tetragonal phases crystallize in the space group P4/mnc (No. 128) with vertex-sharing capped Re2@Ga14 oblong chains. Vacancies were discovered on the Ga4 and Ga5 sites, which can be understood as the direct inclusion of elemental Sn, Pb and Bi into the structure. Heat capacity measurements were performed on all three compounds resulting in a small anomaly which resembles the superconductivity transition temperature from the impurity ReGa5 phase. The three compounds were not superconducting above 1.85 K. Subsequently, electronic structure calculations revealed a high density of states around the Fermi level, as well as non-bonding interactions that likely indicate the stability of these new phases. Full article
(This article belongs to the Special Issue High Pressure Synthesis in Crystalline Materials)
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Article
Structure of Cubic Al73.8Pd13.6Fe12.6 Phase with High Al Content
Crystals 2019, 9(10), 526; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9100526 - 13 Oct 2019
Cited by 1 | Viewed by 1062
Abstract
A cubic ternary phase Al73.8Pd13.6Fe12.6 (designated C′ phase), with very high Al content (Al/TM = 2.82, TM denotes transition metal) was prepared by spark plasma sintering (SPS). Its crystal structure was determined by combing single-crystal X-ray diffraction (SXRD) [...] Read more.
A cubic ternary phase Al73.8Pd13.6Fe12.6 (designated C′ phase), with very high Al content (Al/TM = 2.82, TM denotes transition metal) was prepared by spark plasma sintering (SPS). Its crystal structure was determined by combing single-crystal X-ray diffraction (SXRD) and scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDS) measurements. The crystal structure of the new phase can be described with a small unit cell (a = 7.6403(2) Å; space group Pm 3 ¯ , No. 200) as that of Al2.63Rh (a = 7.6692(1) Å; space group P23, No. 195) while different from those of the reported Al39Pd21Fe2 (a = 15.515(1) Å; space group Fm 3 ¯ , No. 202) and Al69Pd17Fe14 (a = 15.3982(2) Å; space group Im 3 ¯ , No. 204) compounds, which both adopt a double length unit cell in the Al–Pd–Fe system. The mechanism of distributing more Al atoms in the new phase was compared with that of the Al2.63Rh phase by analyzing their site symmetry and the corresponding site of occupancies (SOF). Furthermore, relations of the C′ phase to the reported Al69Pd17Fe14 (designated C1 phase) and Al39Pd21Fe2 (designated C2 phase) phases were investigated by analyzing their building units with the “nanocluster” method in the ToposPro package. Full article
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Article
Revisit the Role of Steps/Disconnections on Misfit Cancellation at Semi-Coherent Interface—Bridging the O-Line Model and the Topological Model
Crystals 2019, 9(10), 525; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9100525 - 13 Oct 2019
Cited by 3 | Viewed by 1262
Abstract
It has been a long-standing topic how the lattice misfit is cancelled at a semi-coherent interphase boundary consisting of terraces and steps. Apart from a set of misfit dislocations separating the coherent patches, the role of steps (which is frequently called ‘disconnections’) on [...] Read more.
It has been a long-standing topic how the lattice misfit is cancelled at a semi-coherent interphase boundary consisting of terraces and steps. Apart from a set of misfit dislocations separating the coherent patches, the role of steps (which is frequently called ‘disconnections’) on misfit cancellation remains ambiguous because these steps do not destroy the continuity of lattice planes across the interface. This paper aims to clarify such ambiguity through identification of a set of secondary dislocations through a rigorous constrained coincidence site lattice (CCSL)/constrained displacive shift complete lattice (CDSCL) analysis. A semi-coherent interface between body-centred cubic (BCC) Cr-rich precipitate and face-centred cubic (FCC) Cu-rich matrix that holds a near N-W orientation relationship (OR) is used as an example to demonstrate the procedure to determine the secondary dislocations that are coincident with steps along the interface. The current approach does not only redefine the disconnections in the topological model, but also extends the description of interface structure from the O-line model. As a result, the ‘discrepancy’ between these two popular crystallographic models can be completely eliminated when the interface is required to contain a pair of parallel close-packed directions. Full article
(This article belongs to the Special Issue Crystallography of Structural Phase Transformations)
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Article
Design of an LED Spot Light System with a Projection Distance of 10 km
Crystals 2019, 9(10), 524; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9100524 - 13 Oct 2019
Cited by 5 | Viewed by 1324
Abstract
We designed a spot light system with an illumination range of 10 km. In the designed system, an appropriate white light-emitting diode (LED) was selected according to the exitance and injection power required. Subsequently, through a first-order optical design, the geometry of the [...] Read more.
We designed a spot light system with an illumination range of 10 km. In the designed system, an appropriate white light-emitting diode (LED) was selected according to the exitance and injection power required. Subsequently, through a first-order optical design, the geometry of the lens and reflector was determined using geometrical calculation. Because the central illuminance of the projection spot of the reflector was 2.5 times that of the cover lens, we first considered the fabrication error of the reflector. According to the adjustment of the optimized distance between the white LED and reflector, we modified the design of the cover lens to fit the new location of the white LED. An LED spot light module containing 16 spot light units was used. The module’s power injection was only 68.2 W. Because of the excellent performance of the designed system in terms of the divergence angle of the projection beam and maximum luminous intensity, which were 1.6° and 2,840,000 cd, respectively, the projection distance of the LED spot light module was 3.37 Km, according to the ANSI regulation. Finally, a spot light system with nine modules and capable of achieving a projection distance of 10 km was successfully fabricated. Full article
(This article belongs to the Special Issue Advanced LED Solid-state Lighting Optics)
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Editorial
Liquid Crystal Optical Devices
Crystals 2019, 9(10), 523; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9100523 - 12 Oct 2019
Viewed by 829
Abstract
It has been approximately 125 years since the Austrian scientist Friedrich Reinitzer in 1888 observed the curious behavior of the double melting points of cholesterol benzoate, a discovery that today is widely recognized as liquid crystal science [...] Full article
(This article belongs to the Special Issue Liquid Crystal Optical Device)
Article
Anion Influence on the Packing of 1,3-Bis(4-Ethynyl-3-Iodopyridinium)-Benzene Halogen Bond Receptors
Crystals 2019, 9(10), 522; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9100522 - 11 Oct 2019
Cited by 4 | Viewed by 1173
Abstract
Rigid and directional arylethynyl scaffolds have been widely successful across diverse areas of chemistry. Utilizing this platform, we present three new structures of a dicationic 1,3-bis(4-ethynyl-3-iodopyridinium)-benzene halogen bonding receptor with tetrafluoroborate, nitrate, and hydrogen sulfate. Structural analysis focused on the receptor conformation, anion [...] Read more.
Rigid and directional arylethynyl scaffolds have been widely successful across diverse areas of chemistry. Utilizing this platform, we present three new structures of a dicationic 1,3-bis(4-ethynyl-3-iodopyridinium)-benzene halogen bonding receptor with tetrafluoroborate, nitrate, and hydrogen sulfate. Structural analysis focused on the receptor conformation, anion shape, solvation, and long range packing of these systems. Coupled with our previously reported structures, we concluded that anions can be classified as building units within this family of halogen bonding receptors. Two kinds of antiparallel dimers were observed for these dicationic receptors. An off-centered species was most frequent, present among geometrically diverse anions and assorted receptor conformations. In contrast, the centered antiparallel dimers were observed with receptors adopting a bidentate conformation in the solid-state. While anions support the solid-state formation of dimers, the molecular geometry and characteristics (planarity, rigidity, and directionality) of arylethynyl systems increase the likelihood of dimer formation by limiting efficient packing arrangements. The significantly larger cation may have considerable influence on the solid-state packing, as similar cationic arylethynyl systems also display these dimers. Full article
(This article belongs to the Special Issue Halogen-Bonded Cocrystals)
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Article
A New High-Pressure Phase Transition in Natural Gedrite
Crystals 2019, 9(10), 521; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9100521 - 11 Oct 2019
Viewed by 1805
Abstract
High-pressure diamond-anvil cell synchrotron X-ray diffraction experiments were conducted on single-crystal samples of natural orthoamphibole; gedrite; with composition; (K0.002Na0.394)(Mg2)(Mg1.637Fe2.245Mn0.004Ca0.022Cr0.003Na0.037Al1.052)(Si6.517Al1.483)O [...] Read more.
High-pressure diamond-anvil cell synchrotron X-ray diffraction experiments were conducted on single-crystal samples of natural orthoamphibole; gedrite; with composition; (K0.002Na0.394)(Mg2)(Mg1.637Fe2.245Mn0.004Ca0.022Cr0.003Na0.037Al1.052)(Si6.517Al1.483)O22(OH)2. The samples were compressed at 298 K up to a maximum pressure of 27(1) GPa. In this pressure regime, we observed a displacive phase transition between 15.1(7) and 21(1) GPa from the orthorhombic Pnma phase to a new structure with space group P21/m; which is different from the familiar P21/m structure of cummingtonite and retains the (+, +, −, −) I-beam stacking sequence of the orthorhombic structure. The unit cell parameters for the new phase at 21(1) GPa are a = 17.514(3), b = 17.077(1), c = 4.9907(2) Å and β = 92.882(6)°. The high-pressure P21/m phase is the first amphibole structure to show the existence of four crystallographically distinct silicate double chains. The orthorhombic to monoclinic phase transition is characterized by an increase in the degree of kinking of the double silicate chains and is analogous to displacive phase changes recently reported in orthopyroxenes, highlighting the parallel structural relations and phase transformation behavior of orthorhombic single- and double-chain silicates. Full article
(This article belongs to the Special Issue High Pressure Synthesis in Crystalline Materials)
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Article
Co-Crystal with Unusual High Z′ and Z′′ Values Derived from Hexamethylenetetramine and 4-fluorophenol (1/1)
Crystals 2019, 9(10), 520; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9100520 - 10 Oct 2019
Cited by 3 | Viewed by 1036
Abstract
The title co-crystal, 1,3,5,7-tetraazatricyclo[3.3.1.13,7]decane (HMTA, 1)–4-fluorophenol (4-FP) (1/1), C6H12N4·C6H5FO, shows an unusual asymmetric unit that comprises eight independent molecules (Z′′ = 8), four for each component, with four formula units per [...] Read more.
The title co-crystal, 1,3,5,7-tetraazatricyclo[3.3.1.13,7]decane (HMTA, 1)–4-fluorophenol (4-FP) (1/1), C6H12N4·C6H5FO, shows an unusual asymmetric unit that comprises eight independent molecules (Z′′ = 8), four for each component, with four formula units per asymmetric unit (Z′ = 4). In the molecular packing, each HMTA molecule bridges one 4-FP molecule via an O−H···N hydrogen bond to form a two-molecule aggregate. Differences can be observed between the bond lengths and angles of the independent HMTA and 4-FP molecules and those of the molecules in the aggregate. The C−N bonds exhibit different bond lengths in the tetrahedral cage-like structure of the HMTA molecules, but the largest differences between the molecular aggregates are in the bond lengths in the 4-fluorophenol ring. In the crystal, the HMTA and 4-FP molecules form two hydrogen-bonded (O−H···N, C−H···F and C−H···O) dimers of HMTA and 4-FP molecules, A···D and B···C inversion dimers, which generate enlarged R88(34) ring motifs in both supramolecular structures. In both structures, the crystal packing also features additional C−H···F and C−H···O interactions. The A···D and B···C dimers are linked by additional C−H···F and C−H···O hydrogen bonds, forming columns along the a and b axes, respectively. The importance of the C−H···F interaction to the structure and crystal packing has been demonstrated. Full article
(This article belongs to the Section Crystal Engineering)
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Article
Twisted Graphene Bilayers and Quasicrystals: A Cut and Projection Approach
Crystals 2019, 9(10), 519; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9100519 - 10 Oct 2019
Cited by 2 | Viewed by 1599
Abstract
In this work, a modified version of the cut and projection approach is proposed to describe the structure of graphene bilayers with twist angles. With this method, the rotation between two graphene layers is viewed as a rotation of the projection space and [...] Read more.
In this work, a modified version of the cut and projection approach is proposed to describe the structure of graphene bilayers with twist angles. With this method, the rotation between two graphene layers is viewed as a rotation of the projection space and the resulting projected structure is interpreted as the set of points of best fit between the two rotated structures. Additionally, focus is given to the pertinence of the many algebraic and geometric tools used in grain boundaries and in quasicrystals to graphene bilayer system (or any other bilayer system, for that matter) case. Full article
(This article belongs to the Special Issue Structure and Properties of Quasicrystals)
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Article
Dissimilar Infrared Brazing of CoCrFe(Mn)Ni Equiatomic High Entropy Alloys and 316 Stainless Steel
Crystals 2019, 9(10), 518; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9100518 - 09 Oct 2019
Cited by 8 | Viewed by 1386
Abstract
Dissimilar infrared brazing of CoCrFeMnNi/CoCrFeNi equiatomic high entropy alloys and 316 stainless steel using MBF601 and BNi-2 foils was evaluated. The wetting angles of the two fillers at 50 °C above their liquidus temperatures on the three substrates were below 40 degrees. The [...] Read more.
Dissimilar infrared brazing of CoCrFeMnNi/CoCrFeNi equiatomic high entropy alloys and 316 stainless steel using MBF601 and BNi-2 foils was evaluated. The wetting angles of the two fillers at 50 °C above their liquidus temperatures on the three substrates were below 40 degrees. The CoCrFeMnNi/316 SS joint had the highest shear strength of 361 MPa with BNi-2 filler brazing at 1020 °C for 180 s, and fractured at the CrB compound in the joint. The CoCrFeMnNi/MBF601/316 SS joint contained a CoCrFeMnNi-based matrix, phosphides and B-containing compounds. The CoCrFeNi/316 SS joint had the highest shear strength of 374 MPa when brazed with BNi-2 filler at 1020 °C for 600 s, and fractured at the CrB in the joint. The CoCrFeNi/MBF601/316 SS joint consisted of a (Fe,Ni)-rich matrix, phosphides and B/Cr/Fe/P compounds, and the highest shear strength of 324 MPa was achieved when it was brazed at 1080 °C for 600 s. Full article
(This article belongs to the Special Issue Mechanical and Microstructural Characterization of Metals and Alloys)
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Article
The Behavior of NH3+ Torsional Vibration in Amino Acids: A Raman Spectroscopic Study
Crystals 2019, 9(10), 517; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9100517 - 09 Oct 2019
Cited by 1 | Viewed by 922
Abstract
In this work we present the continuation of studies carried out on the changes of geometric parameters of the hydrogen bonds in amino acid crystals subjected to temperature or pressure variations. Changes in geometric parameters of the hydrogen bonds are correlated with the [...] Read more.
In this work we present the continuation of studies carried out on the changes of geometric parameters of the hydrogen bonds in amino acid crystals subjected to temperature or pressure variations. Changes in geometric parameters of the hydrogen bonds are correlated with the temperature behavior of the Raman wavenumber of NH3+ torsional band. Now four monocrystals, L-valine, L-isoleucine, taurine, and L-arginine hydrochloride monohydrate, are studied. Temperature evolution of the Raman wavenumber of NH3+ torsional band, with positive slope (dν/dT = 0.023 cm−1/K) of L-isoleucine, can be related to the stability of the crystal structure and the hydrogen bonds strengths on heating due to different temperature lattice parameters variation. Full article
(This article belongs to the Special Issue Raman Spectroscopy of Crystals)
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Article
Numerical Investigation of Thermal Buoyancy, the Electromagnetic Force and Forced Convection in Conventional RF Systems for 4-Inch Sic by TSSG
Crystals 2019, 9(10), 516; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9100516 - 08 Oct 2019
Viewed by 883
Abstract
In this paper, we study thermal buoyancy, the electromagnetic force and forced convection in a conventional radio frequency (RF) furnace for growing large-sized (4-inch) silicon carbide ingots using the top-seeded solution method. The thermal buoyancy and electromagnetic force are analyzed qualitatively and quantitatively [...] Read more.
In this paper, we study thermal buoyancy, the electromagnetic force and forced convection in a conventional radio frequency (RF) furnace for growing large-sized (4-inch) silicon carbide ingots using the top-seeded solution method. The thermal buoyancy and electromagnetic force are analyzed qualitatively and quantitatively under real working conditions, and a method to increase the growth stability of large-sized (4-inch) SiC is proposed through the study of forced convection. Full article
(This article belongs to the Section Crystalline Materials)
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