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Crystals
Volume 7
Issue 9
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Crystals, Volume 7, Issue 9 (September 2017) – 26 articles

Cover Story (view full-size image): The newly designed complex [Zn(L1)(EtOH)] (1) derived from coumarin-containing symmetric Salamo-type N2O2 bisoxime ligands, has been synthesized and characterized, and consists of one Zn(II) ion, one completely deprotonated unit and one coordinated ethanol molecule. The Zn(II) ion is penta-coordinated by two oxime nitrogen atoms and two phenoxo oxygen atoms; the four atoms are all from one deprotonated unit, and there is one oxygen atom from the coordinated ethanol molecule. The coordination environment around the Zn(II) ion is best described as a slightly distorted trigonal bipyramidal geometry. Six pairs of intermolecular hydrogen bonds are formed. In addition, the Cg3 of the pyrone rings as acceptors, forms a hydrogen bond with the protons of coordinated ethanol molecules. The space skeleton of complex 1 adopts a 3D supramolecular structure by the action of the O–H···O, C–H···O hydrogen [...] Read more.
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15 pages, 5735 KB  
Article
Size and Shape Controlled Crystallization of Hemoglobin for Advanced Crystallography
by Ayana Sato-Tomita and Naoya Shibayama
Crystals 2017, 7(9), 282; https://doi.org/10.3390/cryst7090282 - 20 Sep 2017
Cited by 10 | Viewed by 12195
Abstract
While high-throughput screening for protein crystallization conditions have rapidly evolved in the last few decades, it is also becoming increasingly necessary for the control of crystal size and shape as increasing diversity of protein crystallographic experiments. For example, X-ray crystallography (XRC) combined with [...] Read more.
While high-throughput screening for protein crystallization conditions have rapidly evolved in the last few decades, it is also becoming increasingly necessary for the control of crystal size and shape as increasing diversity of protein crystallographic experiments. For example, X-ray crystallography (XRC) combined with photoexcitation and/or spectrophotometry requires optically thin but well diffracting crystals. By contrast, large-volume crystals are needed for weak signal experiments, such as neutron crystallography (NC) or recently developed X-ray fluorescent holography (XFH). In this article, we present, using hemoglobin as an example protein, some techniques for obtaining the crystals of controlled size, shape, and adequate quality. Furthermore, we describe a few case studies of applications of the optimized hemoglobin crystals for implementing the above mentioned crystallographic experiments, providing some hints and tips for the further progress of advanced protein crystallography. Full article
(This article belongs to the Special Issue Biological and Biogenic Crystallization)
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15 pages, 2920 KB  
Article
Microstructure Evolution of Ag-Alloyed PbTe-Based Compounds and Implications for Thermoelectric Performance
by Tom Grossfeld, Ariel Sheskin, Yaniv Gelbstein and Yaron Amouyal
Crystals 2017, 7(9), 281; https://doi.org/10.3390/cryst7090281 - 18 Sep 2017
Cited by 13 | Viewed by 6151
Abstract
We investigate the microstructure evolution of Ag-alloyed PbTe compounds for thermoelectric (TE) applications with or without additions of 0.04 at. % Bi. We control the nucleation and temporal evolution of Ag2Te-precipitates in the PbTe-matrix applying designated aging heat treatments, aiming to [...] Read more.
We investigate the microstructure evolution of Ag-alloyed PbTe compounds for thermoelectric (TE) applications with or without additions of 0.04 at. % Bi. We control the nucleation and temporal evolution of Ag2Te-precipitates in the PbTe-matrix applying designated aging heat treatments, aiming to achieve homogeneous dispersion of precipitates with high number density values, hypothesizing that they act as phonon scattering centers, thereby reducing lattice thermal conductivity. We measure the temperature dependence of the Seebeck coefficient and electrical and thermal conductivities, and correlate them with the microstructure. It is found that lattice thermal conductivity of PbTe-based compounds is reduced by controlled nucleation of Ag2Te-precipitates, exhibiting a number density value as high as 2.7 × 1020 m−3 upon 6 h aging at 380 °C. This yields a TE figure of merit value of ca. 1.4 at 450 °C, which is one on the largest values reported for n-type PbTe compounds. Subsequent aging leads to precipitate coarsening and deterioration of TE performance. Interestingly, we find that Bi-alloying improves the alloys’ thermal stability by suppressing microstructure evolution, besides the role of Bi-atoms as electron donors, thereby maintaining high TE performance that is stable at elevated service temperatures. The latter has prime technological significance for TE energy conversion. Full article
(This article belongs to the Special Issue Materials Processing and Crystal Growth for Thermoelectrics)
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8 pages, 2217 KB  
Article
Structure of a Novel Spinel Li0.5Zn5/3Sb2.5/3O4 by Neutron and Synchrotron Diffraction Analysis
by José Alfredo Marín-Romero, Luis Edmundo Fuentes-Cobas, Juan Rodríguez-Carvajal, Carolina Tabasco-Novelo and Patricia Quintana
Crystals 2017, 7(9), 280; https://doi.org/10.3390/cryst7090280 - 15 Sep 2017
Cited by 8 | Viewed by 7827
Abstract
Zn7/3Sb2/3O4 is a secondary phase in ZnO-based varistors. Acceptor impurities, such as Li+, increase the resistivity. This effect is produced by a modification of the grain boundary barriers. The role of the cationic distribution in the [...] Read more.
Zn7/3Sb2/3O4 is a secondary phase in ZnO-based varistors. Acceptor impurities, such as Li+, increase the resistivity. This effect is produced by a modification of the grain boundary barriers. The role of the cationic distribution in the mentioned events is worth clarifying. The Li0.5Zn5/3Sb2.5/3O4 room-temperature structure was determined by means of a neutron diffraction and synchrotron X-ray diffraction investigation. The title compound was prepared by conventional ceramic process. The elemental composition of the investigated sample was verified by means of electron microscopy—energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The neutron experiment was performed at the high-intensity neutron diffractometer with position-sensitive detector at the D1B beamline of the Laue-Langevin Institute, Grenoble. The high resolution synchrotron measurement was carried out at MCX beamline of Elettra Sincrotrone Trieste. Rietveld analysis was performed with the FullProf program. Li0.5Zn5/3Sb2.5/3O4 belongs to the spinel family, space group F d 3 ¯ m (227). The measured lattice parameter is a = 8.5567(1) Å. The Li+1 and Zn+2 ions are randomly distributed among the tetrahedral and octahedral sites as opposed to Sb+5 ions which have preference for octahedral sites. Fractional coordinate of oxygen, u = 0.2596(1), indicates a slight deformation of the tetrahedral and octahedral sites. The data given in this paper provide structural support for further studies on measurements and microscopic explanations of the interesting properties of this family of compounds. Full article
(This article belongs to the Special Issue Advances in Synchrotron Radiation Applications for Crystal Structure Studies)
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6 pages, 197 KB  
Editorial
Crystallography of Functional Materials
by Winnie Wong-Ng and Claudia J. Rawn
Crystals 2017, 7(9), 279; https://doi.org/10.3390/cryst7090279 - 15 Sep 2017
Cited by 4 | Viewed by 3961
Abstract
The goal of this special issue is to obtain new insights into the roles of crystallography in functional materials. This special issue consists of eight papers illustrating the structure and property relationships, as well as applications of selected classes of materials that deal [...] Read more.
The goal of this special issue is to obtain new insights into the roles of crystallography in functional materials. This special issue consists of eight papers illustrating the structure and property relationships, as well as applications of selected classes of materials that deal with various aspects of functional materials, ranging from battery, magnetic, photocatalysis, and waveguide materials, to luminescent metal-organic frameworks and borates, semiconductors, and inorganic electrides. This issue provides further evidence of the importance of crystallography in understanding and improving various properties of functional materials, whether they are single crystals, bulk polycrystalline materials, or thin films. Full article
(This article belongs to the Special Issue Crystallography of Functional Materials)
20 pages, 1889 KB  
Article
Light-Induced Current Oscillations in the Charge-Ordered State of (TMTTF)2SbF6
by Tobias Peterseim and Martin Dressel
Crystals 2017, 7(9), 278; https://doi.org/10.3390/cryst7090278 - 15 Sep 2017
Cited by 3 | Viewed by 5637
Abstract
Below T CO = 157 K the quasi-one-dimensional charge-transfer salt (TMTTF) 2 SbF 6 undergoes a pronounced phase transition to a charge-ordered ground state. We have explored the non-linear and photoconductive behavior as a function of applied voltage, laser pulse energy and temperature. [...] Read more.
Below T CO = 157 K the quasi-one-dimensional charge-transfer salt (TMTTF) 2 SbF 6 undergoes a pronounced phase transition to a charge-ordered ground state. We have explored the non-linear and photoconductive behavior as a function of applied voltage, laser pulse energy and temperature. Besides a decay of the photoconductive signal in a double exponential fashion in the millisecond range, we discover current oscillations in the kHz range induced by the application of short laser pulses. While the resonance frequencies do not depend on voltage or laser intensity and vary only slightly with temperature, the amplitude changes linearly with the laser intensity and voltage. We suggest that photo-induced fluctuations of the charge-ordered state alter the current flow of the single particles and hence, the photocurrent. The findings are discussed and compared to comparable phenomena in other low-dimensional electron systems. Full article
(This article belongs to the Special Issue Advances in Organic Conductors and Superconductors)
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10 pages, 6791 KB  
Article
The Effects of a Mixed Precipitant on the Morphology and Electrochemical Performance of LiNi0.5Mn1.5O4 Cathode Materials
by Yang Shu, Wenchao Yan, Haisong Wang, Jicheng Jiang, Deye Sun, Xiaodi Ma and Yongcheng Jin
Crystals 2017, 7(9), 275; https://doi.org/10.3390/cryst7090275 - 14 Sep 2017
Cited by 4 | Viewed by 5965
Abstract
A series of LiNi0.5Mn1.5O4 (LNMO) samples were synthesized by adjusting the molar ratio of (NH4)2CO3 to Na2CO3 in a mixed precipitant for evaluating the effects of ammonia from (NH4 [...] Read more.
A series of LiNi0.5Mn1.5O4 (LNMO) samples were synthesized by adjusting the molar ratio of (NH4)2CO3 to Na2CO3 in a mixed precipitant for evaluating the effects of ammonia from (NH4)2CO3 as a complexing agent and Na2CO3 as a precipitant on the morphology and electrochemical performances of LNMO. In this research, a rapid precipitation method followed by hydrothermal treatment was used to prepare the precursors of LNMO, and different molar ratios (0:1, 1:2, 1:1, 2:1, 1:0) of (NH4)2CO3 to Na2CO3 were used for mixed precipitants. The test results revealed that the cathode material exhibits the best electrochemical performance when the molar ratio of (NH4)2CO3 to Na2CO3 is set at 1:2, displaying a specific discharge capacity of 129.4 mA h g−1 at 0.5 C and a capacity retention of 82.3% after 200 charge–discharge cycles. In addition, it still shows a high rate performance with a discharge capacity of 112.7 mA h g−1 at 10 C and 98.8 mA h g−1 at 20 C, which is attributed to an accurate Ni/Mn ratio, smaller primary particle sizes and a porous spherical morphology. Full article
(This article belongs to the Special Issue Solution-Processed Inorganic Functional Crystals)
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15 pages, 8786 KB  
Article
Synthesis, Crystal Structure, Luminescence, Electrochemical and Antimicrobial Properties of Bis(salamo)-Based Co(II) Complex
by Li Wang, Jing Hao, Li-Xiang Zhai, Yang Zhang and Wen-Kui Dong
Crystals 2017, 7(9), 277; https://doi.org/10.3390/cryst7090277 - 12 Sep 2017
Cited by 38 | Viewed by 6163
Abstract
A newly designed Co(II) complex, [Co3(L)(OAc)2(CH3OH)2]·CH3OH, by the reaction of a bis(salamo)-type tetraoxime ligand (H4L) with Co(II) acetate tetrahydrate was synthesized and characterized by elemental analyses, IR, UV-vis spectra and single-crystal [...] Read more.
A newly designed Co(II) complex, [Co3(L)(OAc)2(CH3OH)2]·CH3OH, by the reaction of a bis(salamo)-type tetraoxime ligand (H4L) with Co(II) acetate tetrahydrate was synthesized and characterized by elemental analyses, IR, UV-vis spectra and single-crystal X-ray crystallography. The UV-vis titration experiment manifested that a trinuclear (L:M = 1:3) complex was formed. It is worth noting that the two terminal Co(II) (Co1 and Co3) atoms of the Co(II) complex have different coordination modes and geometries unreported earlier. Furthermore, through intermolecular interactions (C–H···O, C–H···π and O–H···O), a 2D layer-like network is constructed. In addition, the fluorescence behaviors, antimicrobial activities and electrochemical properties of H4L and its Co(II) complex were investigated. Full article
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11 pages, 3742 KB  
Article
Crystal Structure and Phase Transition of the C–H···F–H-Bonded Supramolecular Compound with 4-Nitroanilinium Based on 18-Crown-6
by Chun-li Zhu, Yang Liu, Kun Wang, Yuan Chen and Zun-qi Liu
Crystals 2017, 7(9), 276; https://doi.org/10.3390/cryst7090276 - 12 Sep 2017
Cited by 11 | Viewed by 4436
Abstract
A novel inorganic-organic hybrid supramolecular macrocyclic compound, (4-nitroanilinium)(18-crown-6)(PF6)(1), was synthesized and characterized by infrared spectroscopy, thermogravimetric analysis, elemental analysis, differential scanning calorimetry (DSC), and single-crystal X-ray diffraction. Crystal 1 is found to comprise 1D C–H···F–P hydrogen-bonded chains of (4-nitroanilinium [...] Read more.
A novel inorganic-organic hybrid supramolecular macrocyclic compound, (4-nitroanilinium)(18-crown-6)(PF6)(1), was synthesized and characterized by infrared spectroscopy, thermogravimetric analysis, elemental analysis, differential scanning calorimetry (DSC), and single-crystal X-ray diffraction. Crystal 1 is found to comprise 1D C–H···F–P hydrogen-bonded chains of (4-nitroanilinium+)(18-crown-6) supramolecular cations and PF6− anions. DSC measurements confirm that 1 undergoes a reversible phase transition at 255 K with a hysteresis width of 6 K. A strong dielectric response is observed above 250 K at a low frequency (500 Hz), suggesting the occurrence of proton transfer in the C–H···F–P hydrogen bonds. A precise analysis on the main packing and structural differences, as well as the changes in the intermolecular interaction between the low- and high-temperature phases, reveals that C–H···F–P hydrogen bonds are the main factors affecting phase transition and dielectric behavior. Full article
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13 pages, 5790 KB  
Article
Atomic-Force Microscopy Analyses on Dislocation in Extinction Bands of Poly(dodecamethylene terephthalate) Spherulites Solely Packed of Single-Crystal-Like Lamellae
by Eamor M. Woo, Graecia Lugito, Cheng-En Yang and Shih-Ming Chang
Crystals 2017, 7(9), 274; https://doi.org/10.3390/cryst7090274 - 11 Sep 2017
Cited by 9 | Viewed by 6402
Abstract
This study, using atomic-force and polarized-optical light (AFM and POM) microscopies on the extinction banded spherulites of poly(dodecamethylene terephthalate) (P12T) at high Tc = 110 °C with a film thickness kept at 1–3 µm, has verified that banded spherulites can be composed [...] Read more.
This study, using atomic-force and polarized-optical light (AFM and POM) microscopies on the extinction banded spherulites of poly(dodecamethylene terephthalate) (P12T) at high Tc = 110 °C with a film thickness kept at 1–3 µm, has verified that banded spherulites can be composed of stacks of entirely single-crystal-like lamellae free of any twisting, flipping, or bending, and no branching of lamellae. Defects in the crystal packing of extinction bands are present in both intra-band and inter-band regions. The intra-band defects originate from the miss-match in spiral-circling into circular bands while the inter-band defects are in the interfaces between successive bands where single crystals in the ridge are jammed to deformation, then suddenly precipitate prior to initiating another cycle of banding. The fish-scale lamellae, at the initiation of a cycle, are orderly packed as terrace-like single crystals; conversely, near or on the defected regions, they are highly jammed or squeezed and deformed to beyond recognition of their original single-crystal nature. Full article
(This article belongs to the Special Issue Crystal Morphology and Assembly in Spherulites)
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11 pages, 26220 KB  
Article
Strength and Character of R–X···π Interactions Involving Aromatic Amino Acid Sidechains in Protein-Ligand Complexes Derived from Crystal Structures in the Protein Data Bank
by Kevin E. Riley and Khanh-An Tran
Crystals 2017, 7(9), 273; https://doi.org/10.3390/cryst7090273 - 8 Sep 2017
Cited by 18 | Viewed by 7731
Abstract
Here, we investigate the strengths of R–X···π interactions, involving both chlorine and bromine, in model systems derived from protein-ligand complexes found in the PDB. We find that the strengths of these interactions can vary significantly, with binding energies ranging from −2.01 to −3.60 [...] Read more.
Here, we investigate the strengths of R–X···π interactions, involving both chlorine and bromine, in model systems derived from protein-ligand complexes found in the PDB. We find that the strengths of these interactions can vary significantly, with binding energies ranging from −2.01 to −3.60 kcal/mol. Symmetry adapted perturbation theory (SAPT) analysis shows that, as would be expected, dispersion plays the largest role in stabilizing these R–X···π interactions, generally accounting for about 50% to 80% of attraction. R–Br···π interactions are, for the most part, found to be stronger than R–Cl···π interactions, although the relative geometries of the interacting pair and the halogen’s chemical environment can also have a strong impact. The two factors that have the strongest impact on the strength of these R–X···π interactions is the distance between the halogen and the phenyl plane as well as the size of the halogen σ-hole. Full article
(This article belongs to the Special Issue Analysis of Halogen and Other σ-Hole Bonds in Crystals)
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21 pages, 8678 KB  
Review
Graphene Coated Nanoprobes: A Review
by Fei Hui, Shaochuan Chen, Xianhu Liang, Bin Yuan, Xu Jing, Yuanyuan Shi and Mario Lanza
Crystals 2017, 7(9), 269; https://doi.org/10.3390/cryst7090269 - 8 Sep 2017
Cited by 19 | Viewed by 8624
Abstract
Nanoprobes are one of the most important components in several fields of nanoscience to study materials, molecules and particles. In scanning probe microscopes, the nanoprobes consist on silicon tips coated with thin metallic films to provide additional properties, such as conductivity. However, if [...] Read more.
Nanoprobes are one of the most important components in several fields of nanoscience to study materials, molecules and particles. In scanning probe microscopes, the nanoprobes consist on silicon tips coated with thin metallic films to provide additional properties, such as conductivity. However, if the experiments involve high currents or lateral frictions, the initial properties of the tips can wear out very fast. One possible solution is the use of hard coatings, such as diamond, or making the entire tip out of a precious material (platinum or diamond). However, this strategy is more expensive and the diamond coatings can damage the samples. In this context, the use of graphene as a protective coating for nanoprobes has attracted considerable interest. Here we review the main literature in this field, and discuss the fabrication, performance and scalability of nanoprobes. Full article
(This article belongs to the Special Issue Integration of 2D Materials for Electronics Applications)
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8 pages, 3993 KB  
Article
CH3NH3Cl Assisted Solvent Engineering for Highly Crystallized and Large Grain Size Mixed-Composition (FAPbI3)0.85(MAPbBr3)0.15 Perovskites
by Yihui Li, Taiyang Zhang, Feng Xu, Yong Wang, Ge Li, Yang Yang and Yixin Zhao
Crystals 2017, 7(9), 272; https://doi.org/10.3390/cryst7090272 - 5 Sep 2017
Cited by 31 | Viewed by 11020
Abstract
High-quality mixed-cation lead mixed-halide (FAPbI3)0.85(MAPbBr3)0.15 perovskite films have been prepared using CH3NH3Cl additives via the solvent engineering method. The UV/Vis result shows that the addition of additives leads to enhanced absorptions. XRD [...] Read more.
High-quality mixed-cation lead mixed-halide (FAPbI3)0.85(MAPbBr3)0.15 perovskite films have been prepared using CH3NH3Cl additives via the solvent engineering method. The UV/Vis result shows that the addition of additives leads to enhanced absorptions. XRD and SEM characterizations suggest that compact, pinhole-free and uniform films can be obtained. This is attributable to the crystallization improvement caused by the CH3NH3Cl additives. The power conversion efficiency (PCE) of the F-doped SnO2 (FTO)/compact-TiO2/perovskite/Spiro-OMeTAD/Ag device increases from 15.3% to 16.8% with the help of CH3NH3Cl additive. Full article
(This article belongs to the Special Issue Metal Halide Perovskite Crystals: Growth Techniques, Properties and Emerging Applications)
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14 pages, 7889 KB  
Article
Spark Plasma Sintering of Tungsten Oxides WOx (2.50 ≤ x ≤ 3): Phase Analysis and Thermoelectric Properties
by Felix Kaiser, Paul Simon, Ulrich Burkhardt, Bernd Kieback, Yuri Grin and Igor Veremchuk
Crystals 2017, 7(9), 271; https://doi.org/10.3390/cryst7090271 - 5 Sep 2017
Cited by 23 | Viewed by 9472
Abstract
The solid-state reaction of WO3 with W was studied in order to clarify the phase formation in the binary system W-O around the composition WOx (2.50 ≤ x ≤ 3) during spark plasma sintering (SPS). A new phase “WO2.82” [...] Read more.
The solid-state reaction of WO3 with W was studied in order to clarify the phase formation in the binary system W-O around the composition WOx (2.50 ≤ x ≤ 3) during spark plasma sintering (SPS). A new phase “WO2.82” is observed in the range 2.72 ≤ x ≤ 2.90 which might have the composition W12O34. The influence of the composition on the thermoelectric properties was investigated for 2.72 ≤ x ≤ 3. The Seebeck coefficient, electrical conductivity and electronic thermal conductivity are continuously tunable with the oxygen-to-tungsten ratio. The phase formation mainly affects the lattice thermal conductivity κlat which is significantly reduced until 700 K for the sample with the composition x = 2.84, which contains the phases W18O49 and “WO2.82”. In single-phase WO2.90 and multi-phase WOx materials (2.90 ≤ x ≤ 3), which contain crystallographic shear plane phases, a similar reduced κlat is observed only below 560 K and 550 K, respectively. Therefore, the composition range x < 2.90 in which the pentagonal column structural motif is formed might be more suitable for decreasing the lattice thermal conductivity at high temperatures. Full article
(This article belongs to the Special Issue Materials Processing and Crystal Growth for Thermoelectrics)
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20 pages, 7355 KB  
Article
Calcium Sulfate Hemihydrate Whiskers Obtained from Flue Gas Desulfurization Gypsum and Used for the Adsorption Removal of Lead
by Xiaoshu Wang, Lei Wang, Yan Wang, Ruiqi Tan, Xing Ke, Xian Zhou, Junjun Geng, Haobo Hou and Min Zhou
Crystals 2017, 7(9), 270; https://doi.org/10.3390/cryst7090270 - 4 Sep 2017
Cited by 54 | Viewed by 9519
Abstract
Abstract: As a recycled material, flue gas desulfurization gypsum has been used to prepare calcium sulfate hemihydrate whisker (CSHW) through hydrothermal synthesis for several decades. However, the subsequent utilization of this resultant material has not yet received considerable attention. In the [...] Read more.
Abstract: As a recycled material, flue gas desulfurization gypsum has been used to prepare calcium sulfate hemihydrate whisker (CSHW) through hydrothermal synthesis for several decades. However, the subsequent utilization of this resultant material has not yet received considerable attention. In the present research, CSHW was successfully synthesized at a certain region, and was used for the adsorption of lead ions from aqueous solutions, thereby broadening the research field for the practical application of CSHW. Its adsorption capacity was significantly influenced by various parameters, particularly, the pH level and initial lead concentration. The pH value highly affected the hydrolysis degree of lead ions and dominated the adsorption of lead. The equilibrium isotherms under two different temperatures were simulated using Langmuir, Freundlich, and Temkin models. Both Langmuir and Temkin models showed a good fit to the data. Combined with the well-fitted pseudo-second-order model, the adsorption mechanism was thought to be a chemisorption process that was enforced by the ion exchange reaction. In addition, the specific crystal structure of CSHW revealed that ion exchange reaction occurred on the (010) and (100) facets due to their preferential growth and negatively charged property. The residual solid phase after adsorption was collected and detected using X-ray diffraction and scanning electron microscopy with energy dispersive X-ray spectroscopy. Results revealed that PbSO4 was formed on the surface of CSHW. The alkaline condition introduced the tribasic lead sulfate, and thus reduced the stability of the adsorption system. Full article
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17 pages, 7512 KB  
Review
Recent Advances on p-Type III-Nitride Nanowires by Molecular Beam Epitaxy
by Songrui Zhao and Zetian Mi
Crystals 2017, 7(9), 268; https://doi.org/10.3390/cryst7090268 - 1 Sep 2017
Cited by 39 | Viewed by 9394
Abstract
p-Type doping represents a key step towards III-nitride (InN, GaN, AlN) optoelectronic devices. In the past, tremendous efforts have been devoted to obtaining high quality p-type III-nitrides, and extraordinary progress has been made in both materials and device aspects. In this [...] Read more.
p-Type doping represents a key step towards III-nitride (InN, GaN, AlN) optoelectronic devices. In the past, tremendous efforts have been devoted to obtaining high quality p-type III-nitrides, and extraordinary progress has been made in both materials and device aspects. In this article, we intend to discuss a small portion of these processes, focusing on the molecular beam epitaxy (MBE)-grown p-type InN and AlN—two bottleneck material systems that limit the development of III-nitride near-infrared and deep ultraviolet (UV) optoelectronic devices. We will show that by using MBE-grown nanowire structures, the long-lasting p-type doping challenges of InN and AlN can be largely addressed. New aspects of MBE growth of III-nitride nanostructures are also discussed. Full article
(This article belongs to the Special Issue Current and Future Directions in Crystal Growth by Molecular Beam Epitaxy (MBE))
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18 pages, 5107 KB  
Article
Tri- and Mono-Nuclear Zinc(II) Complexes Based on Half- and Mono-Salamo Chelating Ligands
by Xiu-Yan Dong, Lei Gao, Fei Wang, Yang Zhang and Wen-Kui Dong
Crystals 2017, 7(9), 267; https://doi.org/10.3390/cryst7090267 - 1 Sep 2017
Cited by 29 | Viewed by 5256
Abstract
Two newly designed complexes, [Zn(L1)(EtOH)] (1) and [{Zn(L2)(OAc)2}2Zn]·CHCl3 (2) derived from salamo and half-salamo chelating ligands (H2L1 and HL2) have been synthesized and characterized by [...] Read more.
Two newly designed complexes, [Zn(L1)(EtOH)] (1) and [{Zn(L2)(OAc)2}2Zn]·CHCl3 (2) derived from salamo and half-salamo chelating ligands (H2L1 and HL2) have been synthesized and characterized by elemental analyses, IR and UV-VIS spectra, fluorescence spectra, and X-ray crystallography. Complex 1 shows a slightly distorted tetragonal pyramid and forms an infinite 3D supramolecular structure. All of the Zn(II) ions in complex 2 are hexa-coordinated with slightly distorted octahedral geometries. Complex 2 possesses an infinite 2D space structure. The fluorescence titration experiments were used to characterize fluorescence properties of complexes 1 and 2. And the normalized fluorescent spectra exhibit that complexes 1 and 2 have favourable fluorescent emissions in different solvents. Full article
(This article belongs to the Section Crystal Engineering)
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16 pages, 23439 KB  
Article
Ultrathin g-C3N4 Nanosheet-Modified BiOCl Hierarchical Flower-Like Plate Heterostructure with Enhanced Photostability and Photocatalytic Performance
by Tiekun Jia, Jili Li, Fei Long, Fang Fu, Junwei Zhao, Zhao Deng, Xiaohui Wang and Ying Zhang
Crystals 2017, 7(9), 266; https://doi.org/10.3390/cryst7090266 - 31 Aug 2017
Cited by 44 | Viewed by 8498
Abstract
A novel ultrathin g-C3N4 nanosheet-modified BiOCl hierarchical flower-like plate heterostructure (abbreviated as BC/CN) was constructed via a thermal polymerization of urea precursor followed with hydrolysis route. The as-prepared samples were well characterized by various analytical techniques. The morphological observation showed [...] Read more.
A novel ultrathin g-C3N4 nanosheet-modified BiOCl hierarchical flower-like plate heterostructure (abbreviated as BC/CN) was constructed via a thermal polymerization of urea precursor followed with hydrolysis route. The as-prepared samples were well characterized by various analytical techniques. The morphological observation showed that hierarchical flower-like BiOCl nanoplates were discretely anchored on the surface of ultra-thin C3N4 nanosheets. The photocatalytic performance of the as-prepared photocatalysts was evaluated by degradation of methylene blue (MB) under visible-light irradiation. The results showed that BC/CN photocatalyst exhibited enhanced photostability and photocatalytic performance in the degradation process. On the basis of experimental results and the analysis of band energy structure, it could be inferred that the enhanced photocatalytic performance of BC/CN photocatalyst was intimately related with the hybridization of hierarchical flower-like BiOCl nanoplates with ultrathin g-C3N4 nanosheets, which provided good adsorptive capacity, extended light absorption, suppressed the recombination of photo-generated electron–hole pairs, and facilitated charge transfer efficiently. Full article
(This article belongs to the Special Issue Functional Multi-Scale Crystals)
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22 pages, 5853 KB  
Review
Interfacing 2D Semiconductors with Functional Oxides: Fundamentals, Properties, and Applications
by Zhiquan Yuan, Jiwei Hou and Kai Liu
Crystals 2017, 7(9), 265; https://doi.org/10.3390/cryst7090265 - 31 Aug 2017
Cited by 19 | Viewed by 10688
Abstract
Two-dimensional semiconductors, such as transition-metal dichalcogenides (TMDs) and black phosphorous (BP), have found various potential applications in electronic and opto-electronic devices. However, several problems including low carrier mobility and low photoluminescence efficiencies still limit the performance of these devices. Interfacing 2D semiconductors with [...] Read more.
Two-dimensional semiconductors, such as transition-metal dichalcogenides (TMDs) and black phosphorous (BP), have found various potential applications in electronic and opto-electronic devices. However, several problems including low carrier mobility and low photoluminescence efficiencies still limit the performance of these devices. Interfacing 2D semiconductors with functional oxides provides a way to address the problems by overcoming the intrinsic limitations of 2D semiconductors and offering them multiple functionalities with various mechanisms. In this review, we first focus on the physical effects of various types of functional oxides on 2D semiconductors, mostly on MoS2 and BP as they are the intensively studied 2D semiconductors. Insulating, semiconducting, conventional piezoelectric, strongly correlated, and magnetic oxides are discussed. Then we introduce the applications of these 2D semiconductors/functional oxides systems in field-effect devices, nonvolatile memory, and photosensing. Finally, we discuss the perspectives and challenges within this research field. Our review provides a comprehensive understanding of 2D semiconductors/functional oxide heterostructures, and could inspire novel ideas in interface engineering to improve the performance of 2D semiconductor devices. Full article
(This article belongs to the Special Issue Two-Dimensional Materials beyond Graphene and their Van der Waals Heterostructures)
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15 pages, 2112 KB  
Article
LPE Growth of Single Crystalline Film Scintillators Based on Ce3+ Doped Tb3−xGdxAl5−yGayO12 Mixed Garnets
by Vitalii Gorbenko, Tetiana Zorenko, Sandra Witkiewicz, Kazimierz Paprocki, Oleg Sidletskiy, Alexander Fedorov, Paweł Bilski, Anna Twardak and Yuriy Zorenko
Crystals 2017, 7(9), 262; https://doi.org/10.3390/cryst7090262 - 30 Aug 2017
Cited by 18 | Viewed by 7008
Abstract
The growth of single crystalline films (SCFs) with excellent scintillation properties based on the Tb1.5Gd1.5Al5−yGayO12:Ce mixed garnet at y = 2–3.85 by Liquid Phase Epitaxy (LPE) method onto Gd3Al2.5Ga [...] Read more.
The growth of single crystalline films (SCFs) with excellent scintillation properties based on the Tb1.5Gd1.5Al5−yGayO12:Ce mixed garnet at y = 2–3.85 by Liquid Phase Epitaxy (LPE) method onto Gd3Al2.5Ga2.5O12 (GAGG) substrates from BaO based flux is reported in this work. We have found that the best scintillation properties are shown by Tb1.5Gd1.5Al3Ga2O12:Ce SCFs. These SCFs possess the highest light yield (LY) ever obtained in our group for LPE grown garnet SCF scintillators exceeding by at least 10% the LY of previously reported Lu1.5Gd1.5Al2.75Ga2.25O12:Ce and Gd3Al2–2.75 Ga3–2.25O12:Ce SCF scintillators, grown from BaO based flux. Under α-particles excitation, the Tb1.5Gd1.5 Al3Ga2O12:Ce SCF show LY comparable with that of high-quality Gd3Al2.5Ga2.5O12:Ce single crystal (SC) scintillator with the LY above 10,000 photons/MeV but faster (at least by 2 times) scintillation decay times t1/e and t1/20 of 230 and 730 ns, respectively. The LY of Tb1.5Gd1.5Al2.5Ga2.5O12:Ce SCFs, grown from PbO flux, is comparable with the LY of their counterparts grown from BaO flux, but these SCFs possess slightly slower scintillation response with decay times t1/e and t1/20 of 330 and 990 ns, respectively. Taking into account that the SCFs of the Tb1.5Gd1.5Al3–2.25Ga2–2.75O12:Ce garnet can also be grown onto Ce3+ doped GAGG substrates, the LPE method can also be used for the creation of the hybrid film-substrate scintillators for simultaneous registration of the different components of ionization fluxes. Full article
(This article belongs to the Special Issue Luminescent Properties of Lanthanoid Doped Crystals)
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11 pages, 4313 KB  
Article
Stochastic and Deterministic Crystal Structure Solution Methods in GSAS-II: Monte Carlo/Simulated Annealing Versus Charge Flipping
by Robert Von Dreele
Crystals 2017, 7(9), 264; https://doi.org/10.3390/cryst7090264 - 29 Aug 2017
Cited by 5 | Viewed by 6574
Abstract
Crystallographic studies frequently involve the determination of a previously unknown crystal structure; General Structure Analysis System (GSAS)-II provides two methods for this purpose. The Monte Carlo/simulated annealing method is fundamentally stochastic in nature; random trials are tested for suitability by comparing calculated structure [...] Read more.
Crystallographic studies frequently involve the determination of a previously unknown crystal structure; General Structure Analysis System (GSAS)-II provides two methods for this purpose. The Monte Carlo/simulated annealing method is fundamentally stochastic in nature; random trials are tested for suitability by comparing calculated structure factors with a suite of observed ones. In contrast, the charge flipping method may begin with a suite of random structure factor phases, but the subsequent mathematical steps are entirely deterministic even though they appear to display chaotic behavior. This paper will briefly describe these methods as implemented in GSAS-II, illustrating their use with examples. Full article
(This article belongs to the Special Issue Structural Analysis of Crystalline Materials from Powders)
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14 pages, 13279 KB  
Article
Substituent Effects on the Crystal Structures of Salts Prepared from (R)-2-Methoxy-2-(1-naphthyl)propanoic Acid and (R)-1-Arylethylamines
by Akio Ichikawa, Hiroshi Ono and Yuji Mikata
Crystals 2017, 7(9), 263; https://doi.org/10.3390/cryst7090263 - 28 Aug 2017
Cited by 1 | Viewed by 4954
Abstract
The crystal structures of salts 6–9 prepared from (R)-2-methoxy-2-(1-naphthyl)propanoic acid [(R)-MαNP acid, (R)-1] and (R)-1-arylethylamines [salt 6, (R)-1-(4-methoxyphenyl)ethylamine∙(R)-1; salt 7, (R)-1-(4-fluorophenyl)ethylamine∙( [...] Read more.
The crystal structures of salts 6–9 prepared from (R)-2-methoxy-2-(1-naphthyl)propanoic acid [(R)-MαNP acid, (R)-1] and (R)-1-arylethylamines [salt 6, (R)-1-(4-methoxyphenyl)ethylamine∙(R)-1; salt 7, (R)-1-(4-fluorophenyl)ethylamine∙(R)-1; salt 8, (R)-1-(4-chlorophenyl)ethylamine∙(R)-1; and salt 9, (R)-1-(3-chlorophenyl)ethylamine∙(R)-1] were elucidated by X-ray crystallography. The solid-state associations and conformations of the MαNP salts were defined using the concepts of supramolecular- and planar chirality, respectively, and the crystal structures of salts 6–9 were interpreted as a three-step hierarchical assembly. The para-substituents of the (R)-1-arylethylammonium cations were found on sheet structures consisting of 21 columns. Thus, salts possessing smaller para-substituents, that is, salt 7 (p-F) and salt 9 (p-H), and larger para-substituents, that is, salt 6 (p-OMe) and salt 8 (p-Cl), crystallized in the space groups P21 and C2, respectively. Additionally, weak intermolecular interactions, that is, aromatic C–H···π, C–H···F, and C–H···O interactions, were examined in crystalline salts 6–9. Full article
(This article belongs to the Special Issue Crystal Structure Analysis of Supramolecular and Porous Solids)
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8 pages, 2662 KB  
Article
Enhanced Thermoelectric Performance of Te-Doped Bi2Se3−xTex Bulks by Self-Propagating High-Temperature Synthesis
by Rui Liu, Xing Tan, Guangkun Ren, Yaochun Liu, Zhifang Zhou, Chan Liu, Yuanhua Lin and Cewen Nan
Crystals 2017, 7(9), 257; https://doi.org/10.3390/cryst7090257 - 28 Aug 2017
Cited by 62 | Viewed by 7785
Abstract
Polycrystalline Bi2Se3−xTex (x = 0~1.5) samples were prepared by self-propagating high-temperature synthesis (SHS) combined with spark plasma sintering (SPS) and their thermoelectric properties were investigated. The SHS-SPS process can shorten the time with few energy consumptions, and obtain [...] Read more.
Polycrystalline Bi2Se3−xTex (x = 0~1.5) samples were prepared by self-propagating high-temperature synthesis (SHS) combined with spark plasma sintering (SPS) and their thermoelectric properties were investigated. The SHS-SPS process can shorten the time with few energy consumptions, and obtain almost pure Bi2Se3-based phases. Consequently, the Se vacancies and anti-site defects contribute to the converged carrier concentration of ~2 × 1019 cm−3 while the increased carrier effective mass enhances the Seebeck coefficient to more than −158 μV K−1 over the entire temperature range. The lattice thermal conductivity is suppressed from 1.07 Wm−1 K−1 for the pristine specimen to ~0.6 Wm−1 K−1 for Te-substitution samples at 300 K because of point defects caused by the difference of mass and size between Te and Se atoms. Coupled with the enhanced power factor and reduced lattice thermal conductivity, a high ZT of 0.67 can be obtained at 473 K for the Bi2Se1.5Te1.5 sample. Our results reveal that Te-substitution based on the SHS-SPS method is highly-efficient and can improve the thermoelectric properties of Bi2Se3-based materials largely. Full article
(This article belongs to the Special Issue Materials Processing and Crystal Growth for Thermoelectrics)
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13 pages, 3104 KB  
Article
Electrostatic Potential and a Simple Extended Electric Dipole Model of Hydrogen Fluoride as Probes of Non-Bonding Electron Pairs in the Cyclic Ethers 2,5-Dihydrofuran, Oxetane and Oxirane
by J. Grant Hill and Anthony C. Legon
Crystals 2017, 7(9), 261; https://doi.org/10.3390/cryst7090261 - 25 Aug 2017
Cited by 1 | Viewed by 5115
Abstract
The electrostatic potential near to the oxygen atom in each of the cyclic ethers 2,5-dihydrofuran, oxetane and oxirane has been calculated by using a distributed multipole analysis (DMA) of each molecule. The electrostatic potential energy V(φ) of a unit non-perturbing [...] Read more.
The electrostatic potential near to the oxygen atom in each of the cyclic ethers 2,5-dihydrofuran, oxetane and oxirane has been calculated by using a distributed multipole analysis (DMA) of each molecule. The electrostatic potential energy V(φ) of a unit non-perturbing positive charge was calculated (via the DMA of the cyclic ether molecule) as a function of the angle φ between the C2 axis of the cyclic ether and a vector of length r from the O atom to the unit charge. The resulting potential energy functions each has two equivalent minima. The angles φmin at the minima are compared with the angles φ0 and φe made by the O⋯H bond with the C2 axes in the cyclic ether⋯HF complexes, as determined by rotational spectroscopy and ab initio calculations at the CCSD(T)-F12c/cc-pVTZ-F12 level of theory, respectively. An electrostatic model of cyclic ether⋯HF complexes in which the DMA of the cyclic ether interacts with a simple extended electric dipole representation of HF is also used to calculate the variation of the potential energy VHF(φ) of the HF molecule with φ. The angles φmin generated by this model are also compared with φ0 and φe. The extent to which the electrostatic potential and the extended electric dipole HF model can be used as probes for the directions of non-bonding electron pairs carried by O in these cyclic ethers is discussed. Full article
(This article belongs to the Special Issue Analysis of Halogen and Other σ-Hole Bonds in Crystals)
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8 pages, 965 KB  
Article
Effects of Curing Temperature on Electro-Optical Characteristics of a Polymer-Stabilized In-Plane-Switching Liquid Crystal Cell
by Jae-Hyeon Woo, Tae-Hoon Choi, Byoung-Gyu Jeon and Tae-Hoon Yoon
Crystals 2017, 7(9), 260; https://doi.org/10.3390/cryst7090260 - 25 Aug 2017
Cited by 8 | Viewed by 6123
Abstract
We investigated the electro-optic characteristics of a polymer-stabilized, in-plane-switching (IPS) liquid crystal cell as the UV curing temperature was varied. We found that the response time of an IPS cell could be reduced through low-temperature UV curing of a low concentration of polymer [...] Read more.
We investigated the electro-optic characteristics of a polymer-stabilized, in-plane-switching (IPS) liquid crystal cell as the UV curing temperature was varied. We found that the response time of an IPS cell could be reduced through low-temperature UV curing of a low concentration of polymer material. We also found that fast switching could be achieved at a low operating voltage and with little light leakage in the dark state. Low-temperature curing of the polymer structure could greatly reduce the average distance between polymer bundles even at low polymer concentrations. Therefore, the decrease in transmittance of a polymer-stabilized IPS cell could be minimized by increasing the cell gap without sacrificing the response time because of the sufficiently high anchoring strength of the polymer structure obtained through low-temperature UV curing. Full article
(This article belongs to the Section Liquid Crystals)
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11 pages, 3299 KB  
Article
Synthesis, Characterization and DFT Calculations of 4,5,12- and 1,8,12-trichloro-9,10-dihydro-9,10-ethanoanthracene-12-carbonitriles
by Mujeeb A. Sultan, Usama Karama, Abdulrahman I. Almansour, Saied M. Soliman, Hazem A. Ghabbour and Yahia N. Mabkhot
Crystals 2017, 7(9), 259; https://doi.org/10.3390/cryst7090259 - 25 Aug 2017
Cited by 3 | Viewed by 4215
Abstract
The chlorinated ethanoanthracenes: 4,5,12- and 1,8,12-(trichloro-9,10-dihydro-9,10-ethanoanthracene-12-carbonitriles) (1 and 2), which are regioisomers, were synthesized and characterized using nuclear magnetic resonance (1H- and 13C-NMR) and infrared (IR) spectroscopic techniques. The structure of isomer 1 was further confirmed using a [...] Read more.
The chlorinated ethanoanthracenes: 4,5,12- and 1,8,12-(trichloro-9,10-dihydro-9,10-ethanoanthracene-12-carbonitriles) (1 and 2), which are regioisomers, were synthesized and characterized using nuclear magnetic resonance (1H- and 13C-NMR) and infrared (IR) spectroscopic techniques. The structure of isomer 1 was further confirmed using a single-crystal X-ray technique. The relative stabilities of the title compounds were calculated using the density functional theory (DFT) method on the basis of their total energies and thermodynamic parameters. Isomer 1 is thermodynamically more stable than isomer 2 in the gas phase and in solution. The calculated molecular geometry of isomer 1 agreed well with the experimental X-ray structure. The atomic charge distribution at the different atomic sites was calculated using natural bond orbital analysis. Isomer 2 was predicted to be more polar than isomer 1. Full article
(This article belongs to the Special Issue Experimental and Theoretical Electron Density Analysis of Crystals)
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7 pages, 1700 KB  
Article
High Temperature Transport Properties of Yb and In Double-Filled p-Type Skutterudites
by Dean Hobbis, Yamei Liu, Kaya Wei, Terry M. Tritt and George S. Nolas
Crystals 2017, 7(9), 256; https://doi.org/10.3390/cryst7090256 - 23 Aug 2017
Cited by 6 | Viewed by 4368
Abstract
Yb and In double-filled and Fe substituted polycrystalline p-type skutterudite antimonides were synthesized by direct reaction of high-purity elements, followed by solid-state annealing and densification by hot pressing. The stoichiometry and filling fraction were determined by both Rietveld refinement of the X-ray diffraction [...] Read more.
Yb and In double-filled and Fe substituted polycrystalline p-type skutterudite antimonides were synthesized by direct reaction of high-purity elements, followed by solid-state annealing and densification by hot pressing. The stoichiometry and filling fraction were determined by both Rietveld refinement of the X-ray diffraction data and energy dispersive spectroscopic analyses. The transport properties were measured between 300 K and 830 K, and basically indicate that the resistivity and Seebeck coefficient both increase with increasing temperature. In both specimens, the thermal conductivity decreased with increasing temperature up to approximately 700 K, where the onset of bipolar conduction was observed. A maximum ZT value of 0.6 at 760 K was obtained for the Yb0.39In0.018Co2.4Fe1.6Sb12 specimen. Full article
(This article belongs to the Special Issue Materials Processing and Crystal Growth for Thermoelectrics)
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