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Crystals, Volume 8, Issue 12 (December 2018)

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Cover Story (view full-size image) Bromo- and phosphonate-ester-functionalized bis(2,2′:6′,2″-terpyridine) zinc(II) complexes are [...] Read more.
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Open AccessArticle Variant Selection in Fe-20Ni-1.8C under Bending
Crystals 2018, 8(12), 474; https://doi.org/10.3390/cryst8120474
Received: 15 November 2018 / Revised: 12 December 2018 / Accepted: 13 December 2018 / Published: 18 December 2018
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Abstract
Variant selection is commonly observed in martensitic steels when a stress is applied to the material during transformation. Classically, the selection phenomenon is modelled considering the work of the shape strain in the applied stress field. This shape strain is generally calculated by
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Variant selection is commonly observed in martensitic steels when a stress is applied to the material during transformation. Classically, the selection phenomenon is modelled considering the work of the shape strain in the applied stress field. This shape strain is generally calculated by using the Phenomenological Theory of the Martensite Crystallography (PTMC). In the present study, we studied the martensitic transformation occurring in a Fe-20wt%Ni-1.8wt%C alloy transformed while loaded in four-point bending. A significant variant selection is observed, but surprisingly its nature cannot be explained by the classical approach. A crystallography-based empirical model which accounts for the experimental results is proposed instead. Full article
(This article belongs to the Special Issue Microstructures and Properties of Martensitic Materials)
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Open AccessArticle Structural, Mechanical, and Dynamical Properties of Amorphous Li2CO3 from Molecular Dynamics Simulations
Crystals 2018, 8(12), 473; https://doi.org/10.3390/cryst8120473
Received: 29 November 2018 / Revised: 15 December 2018 / Accepted: 15 December 2018 / Published: 18 December 2018
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Abstract
Structural, mechanical, and transport properties of amorphous Li2CO3 were studied using molecular dynamics (MD) simulations and a hybrid MD-Monte Carlo (MC) scheme. A many-body polarizable force field (APPLE&P) was employed in all simulations. Dynamic and mechanical properties of Dilithium carbonate,
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Structural, mechanical, and transport properties of amorphous Li2CO3 were studied using molecular dynamics (MD) simulations and a hybrid MD-Monte Carlo (MC) scheme. A many-body polarizable force field (APPLE&P) was employed in all simulations. Dynamic and mechanical properties of Dilithium carbonate, Li2CO3, in amorphous liquid and glassy phases were calculated over a wide temperature range. At higher temperatures, both anion and cation diffusion coefficients showed similar temperature dependence. However, below the glass transition temperature (T < 450 K) the anions formed a glassy matrix, while Li+ continued to be mobile, showing decoupling of cation and anion diffusion. The conductivity of Li+ at room temperature was estimated to be on the order of 10−6 S/cm. Mechanical analysis revealed that at room temperature the amorphous phase had a shear modulus of about 8 GPa, which was high enough to suppress Li metal dendrite growth on an electrode surface. Full article
(This article belongs to the Special Issue New Materials for Li-Ion Batteries)
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Open AccessArticle Square Column Structure of High Efficiency, Reliable, Uniformly Flexible LED Devices
Crystals 2018, 8(12), 472; https://doi.org/10.3390/cryst8120472
Received: 2 December 2018 / Accepted: 13 December 2018 / Published: 16 December 2018
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Abstract
This study demonstrates that flexible white LEDs, doped with diffusion particles and with a square column structure, have excellent luminosity, uniformity, and bending reliability. This large area (5 cm × 5 cm) square column flexible device had a smaller thickness (2 mm), and
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This study demonstrates that flexible white LEDs, doped with diffusion particles and with a square column structure, have excellent luminosity, uniformity, and bending reliability. This large area (5 cm × 5 cm) square column flexible device had a smaller thickness (2 mm), and enhancements in both luminous efficiency (29.5%) and uniformity (44.6%) compared to the characteristics of the 6 mm reference sample. Optimization of the reflective layer coating for the square column, flexible white LED was achieved with a higher luminous efficiency (171 lm/w) and uniformity (92%). We designed a novel lightning bolt electrode to improve reliability and bendability. After the bending test, the blue flexible LED had a lower bending diameter (10 mm) but more bending circles (increased to 2000 times. Full article
(This article belongs to the Special Issue GaN-Based Optoelectronic Materials and Light Emitting Devices)
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Open AccessArticle Experimental Study on the Oxidation and Diffusion Behavior of Inconel 625 and Tool Materials
Crystals 2018, 8(12), 471; https://doi.org/10.3390/cryst8120471
Received: 19 October 2018 / Revised: 12 December 2018 / Accepted: 13 December 2018 / Published: 15 December 2018
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Abstract
Oxidation and diffusion simulation experiments were conducted to choose the most suitable material for cutting the Inconel 625 superalloy. Three tool materials, WC/Co, coated carbide, and ceramic were used as tool materials in the oxidation simulation experiment. The three tool materials were heated
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Oxidation and diffusion simulation experiments were conducted to choose the most suitable material for cutting the Inconel 625 superalloy. Three tool materials, WC/Co, coated carbide, and ceramic were used as tool materials in the oxidation simulation experiment. The three tool materials were heated for 30 min in a high-temperature furnace, and the high-temperature oxidation products were examined with scanning electron microscopy and X-ray diffraction (XRD). Tools were heated for 90 min in a vacuum tube furnace. The element diffusion behaviors of Inconel 625 and the tool materials were analysed with energy-dispersive X-ray spectroscopy and XRD. Some of the WC and Co in the WC/Co and coated carbide tool materials was oxidized to WO3, Co3O4, and CoWO4, and the oxidation reaction became more intense as the temperature increased. For the ceramic tool, only TiC was oxidized to TiO2, which indicates good oxidation resistance. In the diffusion couple experiments, the diffusion levels of the three tool materials increased with temperature, but the degree of influence differed. Diffusion of elements was hindered by the (Al, Ti) N coating of the coated carbide and effectively inhibited by the Al2O3 in the ceramic tool. In terms of oxidation and diffusion, the most suitable tool material for cutting Inconel 625 was the ceramic, followed by the coated carbide and then WC/Co. Full article
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Open AccessArticle Two 1-D Coordination Polymers Containing Zinc(II) Hexaborates: [Zn(en){B6O7(OH)6}]·2H2O (en = 1,2-diaminoethane) and [Zn(pn){B6O7(OH)6}]·1.5H2O (pn = 1,2-diaminopropane)
Crystals 2018, 8(12), 470; https://doi.org/10.3390/cryst8120470
Received: 27 November 2018 / Revised: 7 December 2018 / Accepted: 9 December 2018 / Published: 14 December 2018
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Abstract
The synthesis and characterization by single-crystal X-ray diffraction (XRD) studies of two new zinc(II) hexaborate(2−) complexes, [Zn(en){B6O7(OH)6}]·2H2O (en = 1,2-diaminoethane) (1) and [Zn(pn){B6O7(OH)6}]·1.5H2O (pn =
[...] Read more.
The synthesis and characterization by single-crystal X-ray diffraction (XRD) studies of two new zinc(II) hexaborate(2−) complexes, [Zn(en){B6O7(OH)6}]·2H2O (en = 1,2-diaminoethane) (1) and [Zn(pn){B6O7(OH)6}]·1.5H2O (pn = 1,2-diaminopropane) (2), are reported. These complexes crystallize from aqueous solutions containing 10:1 ratios of B(OH)3 and the appropriate Zn(II) amine complexes ([Zn(en)3][OH]2 or [Zn(pn)3][OH]2) through self-assembly processes. The hexaborate(2−) anions in 1 and 2 are coordinated to two Zn(II) centers and form one-dimensional (1-D) polymeric coordination chains. R22(8) and R22(6) inter-chain H-bond interactions play an important role in these self-assembly processes and are discussed. Full article
(This article belongs to the Special Issue Self-Assembled Supramolecular Polymers via Strong H Bonding)
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Open AccessArticle Influence of the Crystal Surface on the Austenitic and Martensitic Phase Transition in Pure Iron
Crystals 2018, 8(12), 469; https://doi.org/10.3390/cryst8120469
Received: 22 November 2018 / Revised: 11 December 2018 / Accepted: 12 December 2018 / Published: 14 December 2018
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Abstract
Using classical molecular dynamics simulations, we studied the influence that free surfaces exert on the austenitic and martensitic phase transition in iron. For several single-indexed surfaces—such as (100)bcc and (110)bcc as well as (100)fcc
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Using classical molecular dynamics simulations, we studied the influence that free surfaces exert on the austenitic and martensitic phase transition in iron. For several single-indexed surfaces—such as ( 100 ) bcc and ( 110 ) bcc as well as ( 100 ) fcc and ( 110 ) fcc surfaces—appropriate pathways exist that allow for the transformation of the surface structure. These are the Bain, Mao, Pitsch, and Kurdjumov–Sachs pathways, respectively. Tilted surfaces follow the pathway of the neighboring single-indexed plane. The austenitic transformation temperature follows the dependence of the specific surface energy of the native bcc phase; here, the new phase nucleates at the surface. In contrast, the martensitic transformation temperature steadily decreases when tilting the surface from the (100) fcc to the (110) fcc orientation. This dependence is caused by the strong out-of-plane deformation that (110) fcc facets experience under the transformation; here, the new phase also nucleates in the bulk rather than at the surface. Full article
(This article belongs to the Section Crystalline Materials)
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Open AccessFeature PaperArticle Morphological and Crystallographic Characteristics of α Structure in a Low-Carbon Iron–Nickel Alloy
Crystals 2018, 8(12), 468; https://doi.org/10.3390/cryst8120468
Received: 29 November 2018 / Revised: 11 December 2018 / Accepted: 12 December 2018 / Published: 14 December 2018
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Abstract
The features of α (body-centered cubic) structures were investigated in a low-carbon multicomponent alloy from morphological and crystallographic perspectives. In addition to apparent features of granular bainite and lamellar martensite, a morphological similarity can be found between lath martensite and lath bainite. Therefore,
[...] Read more.
The features of α (body-centered cubic) structures were investigated in a low-carbon multicomponent alloy from morphological and crystallographic perspectives. In addition to apparent features of granular bainite and lamellar martensite, a morphological similarity can be found between lath martensite and lath bainite. Therefore, it is of interest to explore possible discrepancies between lath martensite and lath bainite from a crystallographic perspective. These microstructures were obtained by various cooling rates (i.e., water quenching, 5 °C/s, and 0.05 °C/s) and then were characterized by a combination of scanning electron microscopy and electron backscattered diffraction techniques. It is shown that: (1) Lath martensite (LM) formed in the samples that were water-quenched, and a mixture of LM and lath bainite (LB) and granular bainite (GB) formed in the samples cooled at rates of 5 °C/s and 0.05 °C/s, respectively; (2) A Kurdjumov-Sachs relationship was mostly found in as-quenched martensite, while a Greninger-Troiano relationship represented the orientation relationship of LB and GB; (3) As the cooling rate decreased, the dislocation densities in corresponding microstructures were reduced, while the tendency of variant grouping was enhanced. Full article
(This article belongs to the Special Issue Microstructures and Properties of Martensitic Materials)
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Open AccessArticle Crystal Structures and Optical Properties of Two Novel 1,3,5-Trisubstituted Pyrazoline Derivatives
Crystals 2018, 8(12), 467; https://doi.org/10.3390/cryst8120467
Received: 18 November 2018 / Revised: 8 December 2018 / Accepted: 11 December 2018 / Published: 13 December 2018
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Abstract
Two novel 1,3,5-trisubstituted pyrazoline derivatives—1-acetyl-3-(4-methoxyphenyl)-5-(6-methoxy-2-naphthyl)-pyrazoline (2a) and 1-(4-nitrophenyl)-3-(4-methoxyphenyl)-5-(6-methoxy-2-naphtyl)-pyrazoline (2b)—were synthesized and their structures were determined by single crystal X-ray crystallography. Both of the two crystals exhibit twisted structures due to the large dihedral angles between the pyrazolinyl ring and the aromatic ring at
[...] Read more.
Two novel 1,3,5-trisubstituted pyrazoline derivatives—1-acetyl-3-(4-methoxyphenyl)-5-(6-methoxy-2-naphthyl)-pyrazoline (2a) and 1-(4-nitrophenyl)-3-(4-methoxyphenyl)-5-(6-methoxy-2-naphtyl)-pyrazoline (2b)—were synthesized and their structures were determined by single crystal X-ray crystallography. Both of the two crystals exhibit twisted structures due to the large dihedral angles between the pyrazolinyl ring and the aromatic ring at the 5-position (88.09° for 2a and 71.26° for 2b). The optical–physical properties of the two compounds were investigated. The fluorescent emission of 2b arises from the 1,3-disubstituted pyrazoline chromophores and exhibits a red shift in polar solvents and solid-state, which could be attributed to photo-induced intramolecular charge transfer (ICT) from N1 to C3 in the pyrazoline moiety and the intermolecular interactions within the crystal. The fluorescent emissions of 2a (λmax 358–364 nm) in solvents and solid-state both come from 6-methoxy-2-naphthyl chromophores, which are fairly insensitive to the solvent polarity. Full article
(This article belongs to the Section Crystalline Materials)
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Open AccessArticle A Study of Controllable Synthesis and Formation Mechanism on Flower-Like TiO2 with Spherical Structure
Crystals 2018, 8(12), 466; https://doi.org/10.3390/cryst8120466
Received: 5 November 2018 / Revised: 5 December 2018 / Accepted: 10 December 2018 / Published: 12 December 2018
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Abstract
The development of photocatalytic materials with specific morphologies promises to be a good opportunity to discover geometrically relevant properties. Herein, this paper reported a facile hydrothermal method to directly synthesize TiO2 crystals with flower-like structures using tetrabutyl titanate (TBT) as a titanium
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The development of photocatalytic materials with specific morphologies promises to be a good opportunity to discover geometrically relevant properties. Herein, this paper reported a facile hydrothermal method to directly synthesize TiO2 crystals with flower-like structures using tetrabutyl titanate (TBT) as a titanium source and ethylene glycol as an additive. We also proposed a reasonable growth mechanism by controlling reaction time in detail. The as-prepared samples were analyzed by using X-ray diffraction, scanning electron microscopy and transmission electron microscopy for structure and morphology characterization. The N2 adsorption-desorption isotherm results showed that the surface area of flower-like TiO2 with 10 h reaction time can reach 297 m2/g. We evaluated the photocatalytic performance of samples by using the degradation rate of methylene blue (MB) solution under UV-vis light. The TiO2 with 10 h reaction time exhibited a superior photocatalytic property than other samples in degrading MB under UV-vis light irradiation. More importantly, the catalyst could be reused many times. These results could benefit from the special morphology, high crystallinity and large specific surface area of the samples. Full article
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Open AccessArticle The Mechanical Properties of Defective Graphyne
Crystals 2018, 8(12), 465; https://doi.org/10.3390/cryst8120465
Received: 24 November 2018 / Revised: 7 December 2018 / Accepted: 9 December 2018 / Published: 12 December 2018
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Abstract
Graphyne is a two-dimensional carbon allotrope with superior one-dimensional electronic properties to the “wonder material” graphene. In this study, via molecular dynamics simulations, we investigated the mechanical properties of α-, β-, δ-, and γ-graphynes with various type of point defects and cracks with
[...] Read more.
Graphyne is a two-dimensional carbon allotrope with superior one-dimensional electronic properties to the “wonder material” graphene. In this study, via molecular dynamics simulations, we investigated the mechanical properties of α-, β-, δ-, and γ-graphynes with various type of point defects and cracks with regard to their promising applications in carbon-based electronic devices. The Young’s modulus and the tensile strength of the four kinds of graphyne were remarkably high, though still lower than graphene. Their Young’s moduli were insensitive to various types of point defects, in contrast to the tensile strength. When a crack slit was present, both the Young’s modulus and tensile strength dropped significantly. Furthermore, the Young’s modulus was hardly affected by the strain rate, indicating potential applications in some contexts where the strain rate is unstable, such as the installation of membranes. Full article
(This article belongs to the Special Issue Graphene Mechanics)
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Open AccessArticle A Simple Technique to Improve Microcrystals Using Gel Exclusion of Nucleation Inducing Elements
Crystals 2018, 8(12), 464; https://doi.org/10.3390/cryst8120464
Received: 14 November 2018 / Revised: 7 December 2018 / Accepted: 10 December 2018 / Published: 12 December 2018
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Abstract
A technique is described for generating large well diffracting crystals from conditions that yield microcrystals. Crystallization using this technique is both rapid (crystals appear in <1 h) and robust (48 out of 48 co-crystallized with a fragment library, compared with 26 out of
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A technique is described for generating large well diffracting crystals from conditions that yield microcrystals. Crystallization using this technique is both rapid (crystals appear in <1 h) and robust (48 out of 48 co-crystallized with a fragment library, compared with 26 out of 48 using conventional hanging drop). Agarose gel is used to exclude nucleation inducing elements from the remaining crystallization cocktail. The chemicals in the crystallization cocktail are partitioned into high concentration components (presumed to induce aggregation by reducing water activity) and low concentration nucleation agents (presumed to induce nucleation through direct interaction). The nucleation agents are then combined with 2% agarose gel and deposited on the crystallization shelf of a conventional vapor diffusion plate. The remaining components are mixed with the protein and placed in contact with the agarose drop. This technique yielded well diffracting crystals of lysozyme, cubic insulin, proteinase k, and ferritin (ferritin crystals diffracted to 1.43 Å). The crystals grew rapidly, reaching large size in less than one hour (maximum size was achieved in 1–12 h). This technique is not suitable for poorly expressing proteins because small protein volumes diffuse out of the agarose gel too quickly. However, it is a useful technique for situations where crystals must grow rapidly (such as educational applications and preparation of beamline test specimens) and in situations where crystals must grow robustly (such as co-crystallization with a fragment library). Full article
(This article belongs to the Special Issue Biological Crystallization)
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Open AccessArticle Molecular Dynamics Simulation of Nanoscale Abrasive Wear of Polycrystalline Silicon
Crystals 2018, 8(12), 463; https://doi.org/10.3390/cryst8120463
Received: 11 August 2018 / Revised: 28 November 2018 / Accepted: 9 December 2018 / Published: 12 December 2018
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Abstract
In this work, molecular dynamics simulations of the nanoscratching of polycrystalline and singlecrystalline silicon substrates using a single-crystal diamond tool are conducted to investigate the grain size effect on the nanoscale wear process of polycrystalline silicon. We find that for a constant indentation
[...] Read more.
In this work, molecular dynamics simulations of the nanoscratching of polycrystalline and singlecrystalline silicon substrates using a single-crystal diamond tool are conducted to investigate the grain size effect on the nanoscale wear process of polycrystalline silicon. We find that for a constant indentation depth, both the average normal force and friction force are much larger for single-crystalline silicon compared to polycrystalline silicon. It is also found that, for the polycrystalline substrates, both the average normal force and friction force increase with increasing grain size. However, the friction coefficient decreases with increasing grain size, and is the smallest for single-crystalline silicon. We also find that the quantity of wear atoms increases nonlinearly with the average normal load, inconsistent with Archard’s law. The quantity of wear atoms is smaller for polycrystalline substrates with a larger average grain size. The grain size effect in the nanoscale wear can be attributed to the fact that grain boundaries contribute to the plastic deformation of polycrystalline silicon. Full article
(This article belongs to the Section Crystalline Materials)
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Open AccessArticle Complex Uranyl Dichromates Templated by Aza-Crowns
Crystals 2018, 8(12), 462; https://doi.org/10.3390/cryst8120462
Received: 3 November 2018 / Revised: 28 November 2018 / Accepted: 7 December 2018 / Published: 10 December 2018
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Abstract
Three new uranyl dichromate compounds templated by aza-crown templates were obtained at room temperature by evaporation from aqueous solutions: (H2diaza-18-crown-6)2[(UO2)2(Cr2O7)4(H2O)2](H2O)3 (1
[...] Read more.
Three new uranyl dichromate compounds templated by aza-crown templates were obtained at room temperature by evaporation from aqueous solutions: (H2diaza-18-crown-6)2[(UO2)2(Cr2O7)4(H2O)2](H2O)3 (1), (H4[15]aneN4)[(UO2)2(CrO4)2(Cr2O7)2(H2O)] (H2O)3.5 (2) and (H4Cyclam)(H4[15]aneN4)2[(UO2)6(CrO4)8(Cr2O7)4](H2O)4 (3). The use of aza-crown templates made it possible to isolate unprecedented and complex one-dimensional units in 2 and 3, whereas the structure of 1 is based on simple uranyl-dichromate chains. It is very likely that the presence of relatively large organic molecules of aza-crown ethers does not allow uranyl chromate chain complexes to condense into the units of higher dimensionality (layers or frameworks). In general, the formation of 1, 2, and 3 is in agreement with the general principles elaborated for organically templated uranyl compounds. The negative charge of the [(UO2)(Cr2O7)2(H2O)]2−, [(UO2)2(CrO4)2(Cr2O7)2(H2O)]4− and [(UO2)3(CrO4)4(Cr2O7)2]6− one-dimensional inorganic motifs is compensated by the protonation of all nitrogen atoms in the molecules of aza-crowns. Full article
(This article belongs to the Section Crystalline Materials)
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Open AccessArticle Where Are the tpy Embraces in [Zn{4′-(EtO)2OPC6H4tpy}2][CF3SO3]2?
Crystals 2018, 8(12), 461; https://doi.org/10.3390/cryst8120461
Received: 28 November 2018 / Revised: 7 December 2018 / Accepted: 7 December 2018 / Published: 10 December 2018
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Abstract
In this paper, the bromo- and phosphonate-ester-functionalized complexes [Zn(1)2][CF3SO3]2 and [Zn(2)2][CF3SO3]2 (1 = 4′-(4-bromophenyl)-2,2′:6′,2″-terpyridine, 2 = diethyl (4-([2,2′:6′,2″-terpyridin]-4′-yl)phenyl)phosphonate) are reported. The complexes have been
[...] Read more.
In this paper, the bromo- and phosphonate-ester-functionalized complexes [Zn(1)2][CF3SO3]2 and [Zn(2)2][CF3SO3]2 (1 = 4′-(4-bromophenyl)-2,2′:6′,2″-terpyridine, 2 = diethyl (4-([2,2′:6′,2″-terpyridin]-4′-yl)phenyl)phosphonate) are reported. The complexes have been characterized by electrospray mass spectrometry, IR and absorption spectroscopies, and multinuclear NMR spectroscopy. The single-crystal structures of [Zn(1)2][CF3SO3]2.MeCN.1/2Et2O and [Zn(2)2][CF3SO3]2 have been determined and they confirm {Zn(tpy)2}2+ cores (tpy = 2,2′:6′,2″-terpyridine). Ongoing from X = Br to P(O)(OEt)2, the {Zn(4′-XC6H4tpy)2}2+ unit exhibits significant “bowing” of the backbone, which is associated with changes in packing interactions. The [Zn(1)2]2+ cations engage in head-to-tail 4′-Phtpy...4′-Phtpy embraces with efficient pyridine...phenylene π-stacking interactions. The [Zn(2)2]2+ cations pack with one of the two ligands involved in pyridine...pyridine π-stacking; steric hindrance between one C6H4PO(OEt)2 group and an adjacent pair of π-stacked pyridine rings results in distortion of backbone of the ligand. This report is the first crystallographic determination of a salt of a homoleptic [M{4′-(RO)2OPC6H4tpy}2]n+ cation. Full article
(This article belongs to the Special Issue Metal Phosphonates and Phosphinates)
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Open AccessCommunication Crystal Structure of Bovine Alpha-Chymotrypsin in Space Group P65
Crystals 2018, 8(12), 460; https://doi.org/10.3390/cryst8120460
Received: 21 November 2018 / Revised: 4 December 2018 / Accepted: 7 December 2018 / Published: 10 December 2018
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Abstract
Chymotrypsin is a protease that is commonly used as a standard for protein crystallization and as a model system for studying serine proteases. Unliganded bovine α-chymotrypsin was crystallized at neutral pH using ammonium sulphate as the precipitant, resulting in crystals that conform to
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Chymotrypsin is a protease that is commonly used as a standard for protein crystallization and as a model system for studying serine proteases. Unliganded bovine α-chymotrypsin was crystallized at neutral pH using ammonium sulphate as the precipitant, resulting in crystals that conform to P65 symmetry with unit cell parameters that have not been reported previously. Inspection of crystallographic interfaces revealed that the major interface between any two molecules in the crystal lattice represents the interface of the biological dimer, as previously observed for crystals of unliganded α-chymotrypsin grown at low pH in space group P21. Full article
(This article belongs to the Section Biomolecular Crystals)
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Open AccessArticle Information Capacity of Positron Emission Tomography Scanners
Crystals 2018, 8(12), 459; https://doi.org/10.3390/cryst8120459
Received: 2 November 2018 / Revised: 27 November 2018 / Accepted: 7 December 2018 / Published: 9 December 2018
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Abstract
Background: The aim of the present study was to assess the upper information content bound of positron emission tomography (PET) images, by means of the information capacity (IC). Methods: The Geant4 Application for the Tomographic Emission (GATE) Monte Carlo (MC) package was used,
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Background: The aim of the present study was to assess the upper information content bound of positron emission tomography (PET) images, by means of the information capacity (IC). Methods: The Geant4 Application for the Tomographic Emission (GATE) Monte Carlo (MC) package was used, and reconstructed images were obtained by using the software for tomographic image reconstruction (STIR). The case study for the assessment of the information content was the General Electric (GE) Discovery-ST PET scanner. A thin-film plane source aluminum (Al) foil, coated with a thin layer of silica and with a 18F-fludeoxyglucose (FDG) bath distribution of 1 MBq was used. The influence of the (a) maximum likelihood estimation-ordered subsets-maximum a posteriori probability-one step late (MLE-OS-MAP-OSL) algorithm, using various subsets (1 to 21) and iterations (1 to 20) and (b) different scintillating crystals on PET scanner’s performance, was examined. The study was focused on the noise equivalent quanta (NEQ) and on the single index IC. Images of configurations by using different crystals were obtained after the commonly used 2-dimensional filtered back projection (FBP2D), 3-dimensional filtered back projection re-projection (FPB3DRP) and the (MLE)-OS-MAP-OSL algorithms. Results: Results shown that the images obtained with one subset and various iterations provided maximum NEQ values, however with a steep drop-off after 0.045 cycles/mm. The single index IC data were maximized for the range of 8–20 iterations and three subsets. The PET scanner configuration incorporating lutetium orthoaluminate perovskite (LuAP) crystals provided the highest NEQ values in 2D FBP for spatial frequencies higher than 0.028 cycles/mm. Bismuth germanium oxide (BGO) shows clear dominance against all other examined crystals across the spatial frequency range, in both 3D FBP and OS-MAP-OSL. The particular PET scanner provided optimum IC values using FBP3DRP and BGO crystals (2.4829 bits/mm2). Conclusions: The upper bound of the image information content of PET scanners can be fully characterized and further improved by investigating the imaging chain components through MC methods. Full article
(This article belongs to the Special Issue Single Crystals for Biomedical Applications)
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Open AccessArticle Synthesis and Characterization of a Monoclinic Crystalline Phase of Hydroxyapatite by Synchrotron X-ray Powder Diffraction and Piezoresponse Force Microscopy
Crystals 2018, 8(12), 458; https://doi.org/10.3390/cryst8120458
Received: 20 November 2018 / Revised: 5 December 2018 / Accepted: 6 December 2018 / Published: 8 December 2018
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Abstract
In this work, we report the synthesis of a monoclinic hydroxyapatite [Ca10(PO4)6(OH)2] (hereafter called HA) prepared by the sol-gel method assisted by ultrasound radiation at room temperature. The characterization of both the monoclinic and the
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In this work, we report the synthesis of a monoclinic hydroxyapatite [Ca10(PO4)6(OH)2] (hereafter called HA) prepared by the sol-gel method assisted by ultrasound radiation at room temperature. The characterization of both the monoclinic and the hexagonal phases were performed by powder X-ray diffraction (PXRD) and using synchrotron radiation (SR). The measurement of the piezoelectricity was performed by piezoresponse force microscopy (PFM). The synthesis produced a mixture of monoclinic and hexagonal hydroxyapatite (HA). We also discuss the importance of stabilizing the monoclinic phase at room temperature with ultrasound irradiation. The existence of the monoclinic phase has important advantages in terms of showing piezoelectric properties for applications in the new medical rehabilitation therapies. Rietveld refinement of the PXRD data from SR indicated the monoclinic phase to be of about 81%. Finally, piezoelectric force microscopy was used to distinguish the phases of hydroxyapatite by measuring the average piezoelectric coefficient deff = 10.8 pm/V. Full article
(This article belongs to the Special Issue Crystallization Under Special and Physical Environments)
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Open AccessFeature PaperArticle Cyclodextrin-Driven Formation of Double Six-Ring (D6R) Silicate Cage: NMR Spectroscopic Characterization from Solution to Crystals
Crystals 2018, 8(12), 457; https://doi.org/10.3390/cryst8120457
Received: 21 November 2018 / Revised: 4 December 2018 / Accepted: 5 December 2018 / Published: 7 December 2018
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Abstract
Identification and isolation of secondary building units (SBUs) from synthesis media of zeolites still represent a challenging task for chemists. The cage structure anion Si12O3012− known as the double six-ring (D6R) was synthesized from α-cyclodextrin (α-CD) mediated alkaline silicate
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Identification and isolation of secondary building units (SBUs) from synthesis media of zeolites still represent a challenging task for chemists. The cage structure anion Si12O3012− known as the double six-ring (D6R) was synthesized from α-cyclodextrin (α-CD) mediated alkaline silicate solutions and conditions of its stability and reactivity in aqueous solution were studied by using nuclear magnetic resonance (NMR) spectroscopy. A single crystal X-ray diffraction (XRD) analysis revealed a novel polymorph of the hybrid complex K12Si12O30·2α-CD·nD2O (n ≈ 30–40), which crystallizes in the orthorhombic C2221 space group symmetry with a = 14.841(4) Å, b = 25.855(6) Å, and c = 41.91(1) Å. The supramolecular adduct of the silicate anion sandwiched by two α-CDs forms a perfect symmetry matching the H-bonding donor-acceptor system between the organic macrocycle and the D6R unit. The driving force of such a hybrid assembly has found to be strongly dependent on the nature of the cation present as large alkali counter ions (K+, Rb+ and Cs+), which stabilize the D6R structure acting as templates. Lastly, we provided the first 29Si MAS NMR measurement of 3Q Si in an isolated D6R unit that allows the verification of the linear correlation between the chemical shift and <SiOSi> bond angle for 3Q Si species in DnR cages (n = 3, 4, 6). Full article
(This article belongs to the Special Issue NMR Crystallography)
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Open AccessCommunication Selective and Recyclable Sensing of Aqueous Phase 2,4,6-Trinitrophenol (TNP) Based on Cd(II) Coordination Polymer with Zwitterionic Ligand
Crystals 2018, 8(12), 456; https://doi.org/10.3390/cryst8120456
Received: 8 October 2018 / Revised: 26 November 2018 / Accepted: 27 November 2018 / Published: 7 December 2018
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Abstract
A novel coordination polymer, {[Cd4(Dccbp)4]·H2O} (1) (Dccbp = 3,5-dicarboxy-1-(3-carboxybenzyl)pyridin-1-ium) was synthesized under hydrothermal conditions by a zwitterionic organic ligand and characterized by single crystal X-ray diffraction, infrared spectrum (IR), thermogravimetric analysis (TG), powder X-ray diffraction
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A novel coordination polymer, {[Cd4(Dccbp)4]·H2O} (1) (Dccbp = 3,5-dicarboxy-1-(3-carboxybenzyl)pyridin-1-ium) was synthesized under hydrothermal conditions by a zwitterionic organic ligand and characterized by single crystal X-ray diffraction, infrared spectrum (IR), thermogravimetric analysis (TG), powder X-ray diffraction (PXRD) and luminescence. Complex 1 with a pyridine cation basic skeleton has the potential to serve as the first case of a luminescent material based on the zwitterionic type of organic ligand for selective, sensitive, and recyclable sensing of 2,4,6-trinitrophenol in the aqueous phase. Full article
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Open AccessArticle The Importance of CH···X (X = O, π) Interaction of a New Mixed Ligand Cu(II) Coordination Polymer: Structure, Hirshfeld Surface and Theoretical Studies
Crystals 2018, 8(12), 455; https://doi.org/10.3390/cryst8120455
Received: 22 October 2018 / Revised: 3 December 2018 / Accepted: 5 December 2018 / Published: 7 December 2018
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Abstract
In this study, a new equimolar (1:1:1) mixed ligand Cu(II) polymer, [Cu(IDA)(ImP)]n (1) with iminodiacetato (IDA) and imidazo[1,2-a]-pyridine (ImP) was synthesized and characterized by single crystal X-ray diffraction analysis. X-ray crystallography reveals that compound (1) consists of polymeric
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In this study, a new equimolar (1:1:1) mixed ligand Cu(II) polymer, [Cu(IDA)(ImP)]n (1) with iminodiacetato (IDA) and imidazo[1,2-a]-pyridine (ImP) was synthesized and characterized by single crystal X-ray diffraction analysis. X-ray crystallography reveals that compound (1) consists of polymeric zigzag chain along [010] the carboxylate carbonyl oxygen atom by two-fold symmetry screw axis. The solid-state structure is stabilized through C–H···O hydrogen bonds and C–H···π interactions that lead the molecules to generate two-dimensional supramolecular assemblies. The intricate combinations of hydrogen bonds and C–H···π interactions are fully described along with computational studies. A thorough analysis of Hirshfeld surface and fingerprint plots elegantly quantify the interactions involved within the structure. The binding energies associated with the noncovalent interactions observed in the crystal structure and the interplay between them were calculated using theoretical DFT calculations. Weak noncovalent interactions were analyzed and characterized using Bader’s theory of ‘‘atoms-in-molecules’’ (AIM). Finally, the solid-state supramolecular assembly was characterized by the “Noncovalent Interaction” (NCI) plot index. Full article
(This article belongs to the Special Issue Self-Assembled Supramolecular Polymers via Strong H Bonding)
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Open AccessArticle Thickness Study of Er-Doped Magnesium Zinc Oxide Diode by Spray Pyrolysis
Crystals 2018, 8(12), 454; https://doi.org/10.3390/cryst8120454
Received: 12 October 2018 / Revised: 27 November 2018 / Accepted: 4 December 2018 / Published: 6 December 2018
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Abstract
Erbium-doped magnesium zinc oxides were prepared through spray pyrolysis deposition at 450 °C with an aqueous solution containing magnesium nitrate, zinc acetate, erbium acetate, and indium nitrate precursors. Diodes with different erbium-doped magnesium zinc oxide thicknesses were fabricated. The effect of erbium-doped magnesium
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Erbium-doped magnesium zinc oxides were prepared through spray pyrolysis deposition at 450 °C with an aqueous solution containing magnesium nitrate, zinc acetate, erbium acetate, and indium nitrate precursors. Diodes with different erbium-doped magnesium zinc oxide thicknesses were fabricated. The effect of erbium-doped magnesium zinc oxide was investigated. The crystalline structure and surface morphology were analyzed using X-ray diffraction and scanning electron microscopy. The films exhibited a zinc oxide structure, with (002), (101), and (102) planes and tiny rods in a mixed hexagonal flakes surface morphology. With the photoluminescence analyses, defect states were identified. The diodes were fabricated via a metallization process in which the top contact was Au and the bottom contact was In. The current–voltage characteristics of these diodes were characterized. The structure resistance increased with the increase in erbium-doped magnesium zinc oxide thickness. With a reverse bias in excess of 8 V, the light spectrum, with two distinct green light emissions at wavelengths of 532 nm and 553 nm, was observed. The light intensity that resulted when using a different operation current of the diodes was investigated. The diode with an erbium-doped magnesium zinc oxide thickness of 230 nm shows high light intensity with an operational current of 80 mA. The emission spectrum with different injection currents for the diodes was characterized and the mechanism is discussed. Full article
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Open AccessArticle Effects of Microsphere Size on the Mechanical Properties of Photonic Crystals
Crystals 2018, 8(12), 453; https://doi.org/10.3390/cryst8120453
Received: 29 September 2018 / Revised: 2 December 2018 / Accepted: 3 December 2018 / Published: 6 December 2018
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Abstract
Photonic crystal (PC) thin films that are self-assembled from different-sized silica microspheres were prepared for studying mechanical properties via nanoindentation at the submicron scale. We found that the silica photonic crystals (PCs) possessed a face-centered cubic (FCC) microstructure and their elastic modulus and
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Photonic crystal (PC) thin films that are self-assembled from different-sized silica microspheres were prepared for studying mechanical properties via nanoindentation at the submicron scale. We found that the silica photonic crystals (PCs) possessed a face-centered cubic (FCC) microstructure and their elastic modulus and hardness were in the range of ~1.81–4.92 GPa and 0.008–0.033 GPa, respectively. The calculated results proved that there were size-dependent properties in the silica PCs, in that the elastic modulus and hardness increased as the diameter decreased from 538 nm to 326 nm. After studying the total work and plastic work in the progressive deformation of silica PCs during the nanoindentation tests, we developed a two-stage deformation model to explain how the microsphere size affects the mechanical properties of PC thin films. The phenomenon of “smaller is stronger” is mainly due to the energy consumption, which combines the effects of microstructure collapse, microsphere slide, and reduced porosity during the whole loading and unloading process. In addition, the results of numerical simulation matched the experimental data and reflected the energy change rules of PCs during the indentation process. Furthermore, the study affords useful guidance for constructing high-performance films with proper design and potential application in next-generation PC materials. Full article
(This article belongs to the Section Crystalline Materials)
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Open AccessArticle Thermal Properties and Non-Isothermal Crystallization Kinetics of Poly (δ-Valerolactone) and Poly (δ-Valerolactone)/Titanium Dioxide Nanocomposites
Crystals 2018, 8(12), 452; https://doi.org/10.3390/cryst8120452
Received: 4 November 2018 / Revised: 2 December 2018 / Accepted: 3 December 2018 / Published: 5 December 2018
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Abstract
New poly (δ-valerolactone)/titanium dioxide (PDVL/TiO2) nanocomposites with different TiO2 nanoparticle loadings were prepared by the solvent-casting method and characterized by Fourier transform infra-red, differential scanning calorimetry, X-ray diffraction and scanning electron microscopy, and thermogravimetry analyses. The results obtained reveal good
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New poly (δ-valerolactone)/titanium dioxide (PDVL/TiO2) nanocomposites with different TiO2 nanoparticle loadings were prepared by the solvent-casting method and characterized by Fourier transform infra-red, differential scanning calorimetry, X-ray diffraction and scanning electron microscopy, and thermogravimetry analyses. The results obtained reveal good dispersion of TiO2 nanoparticles in the polymer matrix and non-formation of new crystalline structures indicating the stability of the crystallinity of TiO2 in the composite. A significant increase in the degree of crystallinity was observed with increasing TiO2 content. The non-isothermal crystallization kinetics of the PDVL/TiO2 system indicate that the crystallization process involves the simultaneous occurrence of two- and three-dimensional spherulitic growths. The thermal degradation analysis of this nanocomposite reveals a significant improvement in the thermal stability with increasing TiO2 loading. Full article
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Open AccessArticle Mechanical Properties, Electronic Structures, and Debye Temperature of NixBy Compounds Obtained by the First Principles Calculations
Crystals 2018, 8(12), 451; https://doi.org/10.3390/cryst8120451
Received: 23 October 2018 / Revised: 26 November 2018 / Accepted: 27 November 2018 / Published: 30 November 2018
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Abstract
Mechanical properties, electronic properties, and Debye temperatures of NixBy (Ni3B, Ni2B, Ni4B3 and NiB) compounds were obtained by the first principles calculations based on the density functional theory (DFT). The results showed that
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Mechanical properties, electronic properties, and Debye temperatures of NixBy (Ni3B, Ni2B, Ni4B3 and NiB) compounds were obtained by the first principles calculations based on the density functional theory (DFT). The results showed that the formation enthalpy of the NixBy compounds were stable with negative formation enthalpy. NiB had the largest B, G, and E, and the smallest υ; it also had the highest hardness (10.8 GPa) and Debye temperature (681.8 K). Ni4B3 had the strongest anisotropy. It was found that the valence bonds of the NixBy compounds studied were composed of both metal bond and covalent bond, and the mechanical properties and Debye temperature of the NixBy compounds increased with the increase of the B atomic ratio. Full article
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Open AccessArticle Design of a Society of Automotive Engineers Regular Curved Retroreflector for Enhancing Optical Efficiency and Working Area
Crystals 2018, 8(12), 450; https://doi.org/10.3390/cryst8120450
Received: 28 September 2018 / Revised: 26 November 2018 / Accepted: 28 November 2018 / Published: 30 November 2018
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Abstract
A highly efficient regular curved retroreflector is proposed to meet the requirements of the US Society of Automotive Engineers (SAE) regulations. It is demonstrated that 28% higher retroreflection efficiency and 33% more working area can be accomplished with the new designed retroreflector when
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A highly efficient regular curved retroreflector is proposed to meet the requirements of the US Society of Automotive Engineers (SAE) regulations. It is demonstrated that 28% higher retroreflection efficiency and 33% more working area can be accomplished with the new designed retroreflector when compared with the commercial ones used in modern vehicles. Full article
(This article belongs to the Special Issue Advanced LED Solid-state Lighting Optics)
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Open AccessArticle Growth of Ordered Graphene Ribbons by Sublimation Epitaxy
Crystals 2018, 8(12), 449; https://doi.org/10.3390/cryst8120449
Received: 22 October 2018 / Revised: 28 November 2018 / Accepted: 28 November 2018 / Published: 30 November 2018
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Abstract
Ordered graphene ribbons were grown on the surface of 4° off-axis 4H-SiC wafers by sublimation epitaxy, and characterized by using scanning electron microscopy (SEM), atomic force microscopy (AFM) and micro-Raman spectroscopy (μ-Raman). SEM showed that there were gray and dark ribbons on the
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Ordered graphene ribbons were grown on the surface of 4° off-axis 4H-SiC wafers by sublimation epitaxy, and characterized by using scanning electron microscopy (SEM), atomic force microscopy (AFM) and micro-Raman spectroscopy (μ-Raman). SEM showed that there were gray and dark ribbons on the substrate surface, and AFM further revealed that these ordered graphene ribbons had clear stepped morphologies due to surface step-bunching. It was shown by μ-Raman that the numbers of graphene layers of these two types of regions were different. The gray region was composed of mono- or bilayer ordered graphene ribbon, while the dark region was of tri- or few-layer ribbon. Meanwhile, ribbons were all homogeneous and had a width up to 40 μm and a length up to 1000 μm, without micro defects such as grain boundaries, ridges, or mono- and few-layer graphene mixtures. The results of this study are useful for optimized growth of high-quality graphene film on silicon carbide crystal. Full article
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Open AccessArticle Synthesis of Star-Shaped Boron Carbide Micro-Crystallites under High Pressure and High Temperatures
Crystals 2018, 8(12), 448; https://doi.org/10.3390/cryst8120448
Received: 1 November 2018 / Revised: 21 November 2018 / Accepted: 28 November 2018 / Published: 30 November 2018
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We synthesized star-shaped pentagonal microcrystals of boron carbide with an extremely low carbon content (~5%), from m-carborane under high pressure (7 GPa) and high temperature (1370–1670 K). These crystals have five-fold symmetry and grow in the shape of stars. A 5-fold symmetry in
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We synthesized star-shaped pentagonal microcrystals of boron carbide with an extremely low carbon content (~5%), from m-carborane under high pressure (7 GPa) and high temperature (1370–1670 K). These crystals have five-fold symmetry and grow in the shape of stars. A 5-fold symmetry in large micron-sized crystals is extremely rare making this a striking observation. Full article
(This article belongs to the Section Crystal Engineering)
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Open AccessArticle Tetramer Compound of Manganese Ions with Mixed Valence [MnII MnIII MnIV] and Its Spatial, Electronic, Magnetic, and Theoretical Studies
Crystals 2018, 8(12), 447; https://doi.org/10.3390/cryst8120447
Received: 13 November 2018 / Revised: 23 November 2018 / Accepted: 23 November 2018 / Published: 28 November 2018
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Abstract
Using different spectroscopic techniques and computational calculations, we describe the structural and electromagnetic relationship that causes many interesting phenomena within a novel coordination compound with mixed valence manganese (II, III and IV) in its crystal and powder state. The novel compound [MnII
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Using different spectroscopic techniques and computational calculations, we describe the structural and electromagnetic relationship that causes many interesting phenomena within a novel coordination compound with mixed valence manganese (II, III and IV) in its crystal and powder state. The novel compound [MnII MnIII MnIV(HL)2(H2L)2(H2O)4](NO3)2(H2O) 1 was obtained with the Schiff base (E)-2-((2-hydroxybenzylidene)amine)-2-(hydroximethyl)propane-1,3-diol, (H4L), and Mn(NO3)2.4H2O. The coordination reaction was promoted by the deprotonation of the ligand by the soft base triethylamine. The paper’s main contribution is the integration of the experimental and computational studies to explain the interesting magnetic behavior that the mixed valence manganese multimetallic core shows. The results presented herein, which are rarely found for Mn(II), (III) and (IV) complexes, will contribute to the understanding of the magnetic communication generated by the valence electrons and its repercussion in the local geometry and in the overall crystalline structure. Full article
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Open AccessArticle Effect of Transition Metal Substitution on the Charge-Transfer Phase Transition and Ferromagnetism of Dithiooxalato-Bridged Hetero Metal Complexes, (n-C3H7)4N[FeII1−xMnIIxFeIII(dto)3]
Crystals 2018, 8(12), 446; https://doi.org/10.3390/cryst8120446
Received: 2 October 2018 / Revised: 19 November 2018 / Accepted: 21 November 2018 / Published: 28 November 2018
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Abstract
The dithiooxalato-bridged iron mixed-valence complex (n-C3H7)4N[FeIIFeIII(dto)3] (dto = dithiooxalato) undergoes a novel charge-transfer phase transition (CTPT) accompanied by electron transfer between adjacent FeII and FeIII sites. The
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The dithiooxalato-bridged iron mixed-valence complex (n-C3H7)4N[FeIIFeIII(dto)3] (dto = dithiooxalato) undergoes a novel charge-transfer phase transition (CTPT) accompanied by electron transfer between adjacent FeII and FeIII sites. The CTPT influences the ferromagnetic transition temperature according to the change of spin configuration on the iron sites. To reveal the mechanism of the CTPT, we have synthesized the series of metal-substituted complexes (n-C3H7)4N[FeII1-xMnIIxFeIII(dto)3] (x = 0–1) and investigated their physical properties by means of magnetic susceptibility and dielectric constant measurements. With increasing MnII concentration, x, MnII-substituted complexes show the disappearance of CTPT above x = 0.04, while the ferromagnetic phase remains in the whole range of x. These results are quite different from the physical properties of the ZnII-substituted complex, (n-C3H7)4N[FeII1-xZnIIxFeIII(dto)3], which is attributed to the difference of ion radius as well as the spin states of MnII and ZnII. Full article
(This article belongs to the Special Issue Synthesis and Applications of New Spin Crossover Compounds)
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Open AccessReview Tunnel Junctions for III-V Multijunction Solar Cells Review
Crystals 2018, 8(12), 445; https://doi.org/10.3390/cryst8120445
Received: 24 October 2018 / Revised: 15 November 2018 / Accepted: 20 November 2018 / Published: 28 November 2018
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Tunnel Junctions, as addressed in this review, are conductive, optically transparent semiconductor layers used to join different semiconductor materials in order to increase overall device efficiency. The first monolithic multi-junction solar cell was grown in 1980 at NCSU and utilized an AlGaAs/AlGaAs tunnel
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Tunnel Junctions, as addressed in this review, are conductive, optically transparent semiconductor layers used to join different semiconductor materials in order to increase overall device efficiency. The first monolithic multi-junction solar cell was grown in 1980 at NCSU and utilized an AlGaAs/AlGaAs tunnel junction. In the last 4 decades both the development and analysis of tunnel junction structures and their application to multi-junction solar cells has resulted in significant performance gains. In this review we will first make note of significant studies of III-V tunnel junction materials and performance, then discuss their incorporation into cells and modeling of their characteristics. A Recent study implicating thermally activated compensation of highly doped semiconductors by native defects rather than dopant diffusion in tunnel junction thermal degradation will be discussed. AlGaAs/InGaP tunnel junctions, showing both high current capability and high transparency (high bandgap), are the current standard for space applications. Of significant note is a variant of this structure containing a quantum well interface showing the best performance to date. This has been studied by several groups and will be discussed at length in order to show a path to future improvements. Full article
(This article belongs to the Special Issue III-V Heteroepitaxy for Solar Energy Conversion)
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