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Crystals, Volume 6, Issue 9 (September 2016)

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Editorial

Jump to: Research, Review, Other

Open AccessEditorial Boron-Based (Nano-)Materials: Fundamentals and Applications
Crystals 2016, 6(9), 118; doi:10.3390/cryst6090118
Received: 6 September 2016 / Accepted: 13 September 2016 / Published: 19 September 2016
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Abstract
The boron (Z = 5) element is unique. Boron-based (nano-)materials are equally unique. Accordingly, the present special issue is dedicated to crystalline boron-based (nano-)materials and gathers a series of nine review and research articles dealing with different boron-based compounds. Boranes, borohydrides, polyhedral boranes
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The boron (Z = 5) element is unique. Boron-based (nano-)materials are equally unique. Accordingly, the present special issue is dedicated to crystalline boron-based (nano-)materials and gathers a series of nine review and research articles dealing with different boron-based compounds. Boranes, borohydrides, polyhedral boranes and carboranes, boronate anions/ligands, boron nitride (hexagonal structure), and elemental boron are considered. Importantly, large sections are dedicated to fundamentals, with a special focus on crystal structures. The application potentials are widely discussed on the basis of the materials’ physical and chemical properties. It stands out that crystalline boron-based (nano-)materials have many technological opportunities in fields such as energy storage, gas sorption (depollution), medicine, and optical and electronic devices. The present special issue is further evidence of the wealth of boron science, especially in terms of crystalline (nano-)materials. Full article
(This article belongs to the Special Issue Boron-Based (Nano-)Materials: Fundamentals and Applications)
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Research

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Open AccessArticle Facet Appearance on the Lateral Face of Sapphire Single-Crystal Fibers during LHPG Growth
Crystals 2016, 6(9), 101; doi:10.3390/cryst6090101
Received: 31 May 2016 / Revised: 26 July 2016 / Accepted: 28 July 2016 / Published: 25 August 2016
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Abstract
Results of the study of the lateral surface of single-crystal (SC) sapphire fibers grown along crystallographic directions [0001] and [112¯0] by the LHPG method are presented. The appearance or absence of faceting of the lateral surface
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Results of the study of the lateral surface of single-crystal (SC) sapphire fibers grown along crystallographic directions [ 0001 ] and [ 11 2 ¯ 0 ] by the LHPG method are presented. The appearance or absence of faceting of the lateral surface of the fibers depending on the growth direction is analyzed. The crystallographic orientation of the facets is investigated. The microstructure of the samples is investigated with the help of an optical microscope and a JSM-5910LV scanning electronic microscope (JEOL). The crystallographic orientations of the facets on the SC sapphire fiber surface are determined by electron backscatter diffraction (EBSD). The seed orientation is studied by means of XRD techniques. Full article
(This article belongs to the Special Issue Traveling Solvent Floating Zone (TSFZ) Method in Crystal Growth)
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Open AccessArticle The First Homoleptic Complex of Seven-Coordinated Osmium: Synthesis and Crystallographical Evidence of Pentagonal Bipyramidal Polyhedron of Heptacyanoosmate(IV)
Crystals 2016, 6(9), 102; doi:10.3390/cryst6090102
Received: 9 August 2016 / Revised: 17 August 2016 / Accepted: 18 August 2016 / Published: 23 August 2016
Cited by 2 | PDF Full-text (1236 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The ligand exchange in (n-Bu4N)2OsIVCl6 (n-Bu4N = tetra-n-butylammonium) leads to the formation of the osmium(IV) heptacyanide, the first fully inorganic homoleptic complex of heptacoordinated osmium. The single-crystal X-ray
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The ligand exchange in (n-Bu4N)2OsIVCl6 (n-Bu4N = tetra-n-butylammonium) leads to the formation of the osmium(IV) heptacyanide, the first fully inorganic homoleptic complex of heptacoordinated osmium. The single-crystal X-ray diffraction (SC-XRD) study reveals the pentagonal bipyramidal molecular structure of the [Os(CN)7]3− anion. The latter being a diamagnetic analogue of the highly anisotropic paramagnetic synthon, [ReIV(CN)7]3− can be used for the synthesis of the model heterometallic coordination compounds for the detailed study and simulation of the magnetic properties of the low-dimensional molecular nanomagnets involving 5d metal heptacyanides. Full article
(This article belongs to the Special Issue Crystal Structure of Complex Compounds)
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Open AccessArticle Three-Dimensional Cadmium(II) Cyanide Coordination Polymers with Ethoxy-, Butoxy- and Hexyloxy-ethanol
Crystals 2016, 6(9), 103; doi:10.3390/cryst6090103
Received: 28 July 2016 / Revised: 16 August 2016 / Accepted: 17 August 2016 / Published: 24 August 2016
Cited by 1 | PDF Full-text (2579 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The three novel cadmium(II) cyanide coordination polymers with alkoxyethanols, [Cd(CN)2(C2H5OCH2CH2OH)]n (I), [{Cd(CN)2(C4H9OCH2CH2OH)}3{Cd(CN)2}]n (II)
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The three novel cadmium(II) cyanide coordination polymers with alkoxyethanols, [Cd(CN)2(C2H5OCH2CH2OH)]n (I), [{Cd(CN)2(C4H9OCH2CH2OH)}3{Cd(CN)2}]n (II) and [{Cd(CN)2(H2O)2}{Cd(CN)2}3·2(C6H13OCH2CH2OH)]n (III), were synthesized and charcterized by structural determination. Three complexes have three-dimensional Cd(CN)2 frameworks; I has distorted tridymite-like structure, and, II and III have zeolite-like structures. The cavities of Cd(CN)2 frameworks of the complexes are occupied by the alkoxyethanol molecules. In I and II, hydroxyl oxygen atoms of alkoxyethanol molecules coordinate to the Cd(II) ions, and the Cd(II) ions exhibit slightly distort trigonal-bipyramidal coordination geometry. In II, there is also tetrahedral Cd(II) ion which is coordinated by only the four cyanides. The hydroxyl oxygen atoms of alkoxyethanol connects etheric oxygen atoms of the neighboring alkoxyethanol by hydrogen bond in I and II. In III, hexyloxyethanol molecules do not coordinate to the Cd(II) ions, and two water molecules coordnate to the octahedral Cd(II) ions. The framework in III contains octahedral Cd(II) and tetrahedral Cd(II) in a 1:3 ratio. The Cd(CN)2 framework structures depended on the difference of alkyl chain for alkoxyethanol molecules. Full article
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Open AccessFeature PaperCommunication Packing of Helices: Is Chirality the Highest Crystallographic Symmetry?
Crystals 2016, 6(9), 106; doi:10.3390/cryst6090106
Received: 31 July 2016 / Revised: 16 August 2016 / Accepted: 22 August 2016 / Published: 30 August 2016
Cited by 1 | PDF Full-text (1391 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Chiral structures resulting from the packing of helices are common in biological and synthetic materials. Herein, we analyze the noncentrosymmetry (NCS) in such systems using crystallographic considerations. A comparison of the chiral structures built from helices shows that the chirality can be expected
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Chiral structures resulting from the packing of helices are common in biological and synthetic materials. Herein, we analyze the noncentrosymmetry (NCS) in such systems using crystallographic considerations. A comparison of the chiral structures built from helices shows that the chirality can be expected for specific building units such as 31/32 or 61/65 helices which, in hexagonal arrangement, will more likely lead to a chiral resolution. In these two systems, we show that the highest crystallographic symmetry (i.e., the symmetry which can describe the crystal structure from the smallest assymetric unit) is chiral. As an illustration, we present the synthesis of two materials ([Zn(2,2’-bpy)3](NbF6)2 and [Zn(2,2’-bpy)3](TaF6)2) in which the 3n helices pack into a chiral structure. Full article
(This article belongs to the Special Issue Nonlinear Optical Crystals)
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Open AccessArticle A Novel Effect of CO2 Laser Induced Piezoelectricity in Ag2Ga2SiS6 Chalcogenide Crystals
Crystals 2016, 6(9), 107; doi:10.3390/cryst6090107
Received: 5 August 2016 / Revised: 24 August 2016 / Accepted: 26 August 2016 / Published: 31 August 2016
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Abstract
We have discovered a substantial enhancement of the piezoelectric coefficients (from 10 to 78 pm/V) in the chalcogenide Ag2Ga2SiS6 single crystals. The piezoelectric studies were done under the influence of a CO2 laser (wavelength 10.6 μm, time
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We have discovered a substantial enhancement of the piezoelectric coefficients (from 10 to 78 pm/V) in the chalcogenide Ag2Ga2SiS6 single crystals. The piezoelectric studies were done under the influence of a CO2 laser (wavelength 10.6 μm, time duration 200 ns, lasers with power densities varying up to 700 MW/cm2). Contrary to the earlier studies where the photoinduced piezoelectricity was done under the influence of the near IR lasers, the effect is higher by at least one order, which is a consequence of the phonon anharmonic contributions and photopolarizations. Such a discovery allows one to build infrared piezotronic devices, which may be used for the production of the IR laser tunable optoelectronic triggers and memories. This is additionally confirmed by the fact that analogous photoillumination by the near IR laser (Nd:YAG (1064 nm) and Er:glass laser (1540 nm)) gives the obtained values of the effective piezoelectricity at of least one order less. The effect is completely reversible with a relaxation time up to several milliseconds. In order to clarify the role of free carriers, additional studies of photoelectrical spectra were done. Full article
(This article belongs to the Special Issue Crystal Growth for Optoelectronic and Piezoelectric Applications)
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Open AccessArticle Crystallography of Representative MOFs Based on Pillared Cyanonickelate (PICNIC) Architecture
Crystals 2016, 6(9), 108; doi:10.3390/cryst6090108
Received: 2 July 2016 / Revised: 18 August 2016 / Accepted: 22 August 2016 / Published: 5 September 2016
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Abstract
The pillared layer motif is a commonly used route to porous coordination polymers or metal organic frameworks (MOFs). Materials based on the pillared cyano-bridged architecture, [Ni’(L)Ni(CN)4]n (L = pillar organic ligands), also known as PICNICs, have been shown to be
[...] Read more.
The pillared layer motif is a commonly used route to porous coordination polymers or metal organic frameworks (MOFs). Materials based on the pillared cyano-bridged architecture, [Ni’(L)Ni(CN)4]n (L = pillar organic ligands), also known as PICNICs, have been shown to be especially diverse where pore size and pore functionality can be varied by the choice of pillar organic ligand. In addition, a number of PICNICs form soft porous structures that show reversible structure transitions during the adsorption and desorption of guests. The structural flexibility in these materials can be affected by relatively minor differences in ligand design, and the physical driving force for variations in host-guest behavior in these materials is still not known. One key to understanding this diversity is a detailed investigation of the crystal structures of both rigid and flexible PICNIC derivatives. This article gives a brief review of flexible MOFs. It also reports the crystal structures of five PICNICS from our laboratories including three 3-D porous frameworks (Ni-Bpene, NI-BpyMe, Ni-BpyNH2), one 2-D layer (Ni-Bpy), and one 1-D chain (Ni-Naph) compound. The sorption data of BpyMe for CO2, CH4 and N2 is described. The important role of NH3 (from the solvent of crystallization) as blocking ligands which prevent the polymerization of the 1-D chains and 2-D layers to become 3D porous frameworks in the Ni-Bpy and Ni-Naph compounds is also addressed. Full article
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Open AccessArticle Synthesis, Crystal Structure, and Cytotoxic Activity of a Novel Eight-Coordinated Dinuclear Ca(II)-Schiff Base Complex
Crystals 2016, 6(9), 109; doi:10.3390/cryst6090109
Received: 14 July 2016 / Revised: 1 September 2016 / Accepted: 5 September 2016 / Published: 7 September 2016
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Abstract
A novel eight-coordinated dinuclear Ca(II) complex, [Ca2(L)2(H2O)10]·H2O (L = 4-formylbenzene-1,3-disulfonate-3-pyridinecarboxylic hydrazone) (1), was synthesized by the reaction of 3-pyridinecarboxylic hydrazide, disodium 4-formylbenzene-1,3-disulfonate, and Ca(ClO4)2·4H2O in
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A novel eight-coordinated dinuclear Ca(II) complex, [Ca2(L)2(H2O)10]·H2O (L = 4-formylbenzene-1,3-disulfonate-3-pyridinecarboxylic hydrazone) (1), was synthesized by the reaction of 3-pyridinecarboxylic hydrazide, disodium 4-formylbenzene-1,3-disulfonate, and Ca(ClO4)2·4H2O in ethanol-water solution (v:v = 3:1) at 50 °C. Complex 1 was characterized by elemental analysis, IR, 1H-NMR, 13C-NMR, and X-ray single crystal diffraction analysis. Dinuclear Ca(II) complex 1 belongs to triclinic, space group P-1 with a = 7.186(3) Å, b = 11.978(5) Å, c = 12.263(5) Å, α = 90.318(5)°, β = 91.922(5)°, γ = 96.797(5)°, V = 1047.5(8) Å3, Z = 1, Dc = 1.685 mg·m−3, μ = 0.572 mm−1, F(000) = 552, and final R1 = 0.0308, ωR2 = 0.0770. Dinuclear Ca(II) molecules form a 1D chained structure by π–π stacking interaction. The 1D chains form a 3D framework structure by the π–π stacking interaction and hydrogen bonds. The in vitro cytotoxic activity activity of 1 against HL-60 and MLTC-1 was also investigated. Full article
(This article belongs to the Section Biomolecular Crystals)
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Open AccessArticle Molecular Structure, Spectroscopic and DFT Computational Studies of Arylidene-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione
Crystals 2016, 6(9), 110; doi:10.3390/cryst6090110
Received: 4 July 2016 / Revised: 1 September 2016 / Accepted: 5 September 2016 / Published: 8 September 2016
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Abstract
Reaction of barbituric acid derivatives and di-substituted benzaldehyde in water afforded arylidene-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione derivatives (1 and 2). The one step reaction proceeded efficiently, smoothly, and in excellent yield. The arylidene compounds were characterized by spectrophotometric tools
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Reaction of barbituric acid derivatives and di-substituted benzaldehyde in water afforded arylidene-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione derivatives (1 and 2). The one step reaction proceeded efficiently, smoothly, and in excellent yield. The arylidene compounds were characterized by spectrophotometric tools plus X-ray single crystal diffraction technique. Quantum chemical calculations were performed using the DFT/B3LYP method to optimize the structure of the two isomers (1 and 2) in the gas phase. The optimized structures were found to agree well with the experimental X-ray structure data. The highest occupied (HOMO) and lowest unoccupied (LUMO) frontier molecular orbitals analyses were performed and the atomic charges were calculated using natural populationanalysis. Full article
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Open AccessArticle Symmetry-Induced Light Confinement in a Photonic Quasicrystal-Based Mirrorless Cavity
Crystals 2016, 6(9), 111; doi:10.3390/cryst6090111
Received: 17 June 2016 / Revised: 25 August 2016 / Accepted: 5 September 2016 / Published: 8 September 2016
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Abstract
We numerically investigate the electromagnetic field localization in a two-dimensional photonic quasicrystal generated with a holographic tiling. We demonstrate that light confinement can be induced into an air mirrorless cavity by the inherent symmetry of the spatial distribution of the dielectric scatterers forming
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We numerically investigate the electromagnetic field localization in a two-dimensional photonic quasicrystal generated with a holographic tiling. We demonstrate that light confinement can be induced into an air mirrorless cavity by the inherent symmetry of the spatial distribution of the dielectric scatterers forming the side walls of the open cavity. Furthermore, the propagation direction can be controlled by suitable designs of the structure. This opens up new avenues for designing photonic materials and devices. Full article
(This article belongs to the Special Issue Structure and Properties of Quasicrystals 2016)
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Open AccessArticle Coupled Acoustic-Mechanical Bandgaps
Crystals 2016, 6(9), 112; doi:10.3390/cryst6090112
Received: 30 April 2016 / Revised: 9 August 2016 / Accepted: 5 September 2016 / Published: 8 September 2016
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Abstract
In this work, we study the existence of coupled bandgaps for corrugated plate structures and acoustic channels. The study is motivated by the observation that the performance of traditional bandgap structures, such as periodic plates, may be compromised due to the coupling to
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In this work, we study the existence of coupled bandgaps for corrugated plate structures and acoustic channels. The study is motivated by the observation that the performance of traditional bandgap structures, such as periodic plates, may be compromised due to the coupling to a surrounding acoustic medium and the presence of acoustic resonances. It is demonstrated that corrugation of the plate structure can introduce bending wave bandgaps and bandgaps in the acoustic domain in overlapping and audible frequency ranges. This effect is preserved also when taking the physical coupling between the two domains into account. Additionally, the coupling is shown to introduce extra gaps in the band structure due to modal interaction and the appearance of a cut-on frequency for the fundamental acoustic mode. Full article
(This article belongs to the Special Issue Phononic Crystals)
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Open AccessArticle Synthesis of Novel p-tert-Butylcalix[4]arene Derivative: Structural Characterization of a Methanol Inclusion Compound
Crystals 2016, 6(9), 114; doi:10.3390/cryst6090114
Received: 5 July 2016 / Revised: 26 August 2016 / Accepted: 5 September 2016 / Published: 9 September 2016
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Abstract
A p-tertbutylcalix[4]arene derivative was synthesized from a reaction of the diisothiocyanate p-tertbutylcalix[4]arene, obtaining crystals that were then characterized by mass spectroscopy, Raman spectroscopy, and single-crystal X-ray diffraction. The molecule presents two acid carbamothioic-n-ethoxy-methyl-ester substituent groups. Through crystallization of this compound, it
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A p-tertbutylcalix[4]arene derivative was synthesized from a reaction of the diisothiocyanate p-tertbutylcalix[4]arene, obtaining crystals that were then characterized by mass spectroscopy, Raman spectroscopy, and single-crystal X-ray diffraction. The molecule presents two acid carbamothioic-n-ethoxy-methyl-ester substituent groups. Through crystallization of this compound, it was also found that it includes a methanol molecule within the aromatic cavity. The inclusion of the methanol molecule is due to favorable CH∙∙∙π interactions. Full article
(This article belongs to the Section Biomolecular Crystals)
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Open AccessArticle The Effect of Twin Grain Boundary Tuned by Temperature on the Electrical Transport Properties of Monolayer MoS2
Crystals 2016, 6(9), 115; doi:10.3390/cryst6090115
Received: 30 June 2016 / Revised: 14 August 2016 / Accepted: 7 September 2016 / Published: 14 September 2016
Cited by 1 | PDF Full-text (4597 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Theoretical calculation and experimental measurement have shown that twin grain boundary (GB) of molybdenum disulphide (MoS2) exhibits extraordinary effects on transport properties. Precise transport measurements need to verify the transport mechanism of twin GB in MoS2. Here, monolayer molybdenum
[...] Read more.
Theoretical calculation and experimental measurement have shown that twin grain boundary (GB) of molybdenum disulphide (MoS2) exhibits extraordinary effects on transport properties. Precise transport measurements need to verify the transport mechanism of twin GB in MoS2. Here, monolayer molybdenum disulphide with a twin grain boundary was grown in our developed low-pressure chemical vapor deposition (CVD) system, and we investigated how the twin GB affects the electrical transport properties of MoS2 by temperature-dependent transport studies. At low temperature, the twin GB can increase the in-plane electrical conductivity of MoS2 and the transport exhibits variable-range hopping (VRH), while at high temperature, the twin GB impedes the electrical transport of MoS2 and the transport exhibits nearest-neighbor hopping (NNH). Our results elucidate carrier transport mechanism of twin GB and give an important indication of twin GB in tailoring the electronic properties of MoS2 for its applications in next-generation electronics and optoelectronic devices. Full article
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Open AccessCommunication Numerical Analysis of the Combined Influence of Accelerated Crucible Rotation and Dynamic Crucible Translation on Liquid Phase Diffusion Growth of SiGe
Crystals 2016, 6(9), 116; doi:10.3390/cryst6090116
Received: 25 July 2016 / Revised: 3 September 2016 / Accepted: 6 September 2016 / Published: 13 September 2016
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Abstract
The effects of accelerated crucible rotation technique (ACRT) and dynamic translation on liquid phase diffusion (LPD) growth of SixGe1−x single crystals have been separately investigated numerically in earlier works and were found to have a very positive impact on the
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The effects of accelerated crucible rotation technique (ACRT) and dynamic translation on liquid phase diffusion (LPD) growth of SixGe1−x single crystals have been separately investigated numerically in earlier works and were found to have a very positive impact on the LPD growth process. Building upon these findings, in this paper, we study the consequences of imposing both ACRT and dynamic translation on this growth technique. Time-dependent, axisymmetric numerical simulations using moving grid approach have been carried out using finite volume code Ansys Fluent. Crucible translation effect is simulated using dynamic thermal boundary condition. Results are compared to the case in which this growth system is subjected to ACRT only. It is predicted that by combining ACRT with dynamic pulling, excellent axial compositional uniformity can be achieved and growth rate can be improved substantially without significantly compromising on the benefits of employing ACRT. The results show that it is advantageous to utilize the combination of ACRT and dynamic translation during LPD growth rather than using them independently for producing relatively uniform composition SixGe1−x single crystals in a shorter span of time. Full article
(This article belongs to the Special Issue Global Modeling in Crystal Growth)
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Open AccessArticle Self-Assembly of Gold Nanocrystals into Discrete Coupled Plasmonic Structures
Crystals 2016, 6(9), 117; doi:10.3390/cryst6090117
Received: 25 July 2016 / Revised: 25 August 2016 / Accepted: 31 August 2016 / Published: 14 September 2016
Cited by 1 | PDF Full-text (3226 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Development of methodologies for the controlled chemical assembly of nanoparticles into plasmonic molecules of predictable spatial geometry is vital in order to harness novel properties arising from the combination of the individual components constituting the resulting superstructures. This paper presents a route for
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Development of methodologies for the controlled chemical assembly of nanoparticles into plasmonic molecules of predictable spatial geometry is vital in order to harness novel properties arising from the combination of the individual components constituting the resulting superstructures. This paper presents a route for fabrication of gold plasmonic structures of controlled stoichiometry obtained by the use of a di-rhenium thio-isocyanide complex as linker molecule for gold nanocrystals. Correlated scanning electron microscopy (SEM)—dark-field spectroscopy was used to characterize obtained discrete monomer, dimer and trimer plasmonic molecules. Polarization-dependent scattering spectra of dimer structures showed highly polarized scattering response, due to their highly asymmetric D∞h geometry. In contrast, some trimer structures displayed symmetric geometry (D3h), which showed small polarization dependent response. Theoretical calculations were used to further understand and attribute the origin of plasmonic bands arising during linker-induced formation of plasmonic molecules. Theoretical data matched well with experimentally calculated data. These results confirm that obtained gold superstructures possess properties which are a combination of the properties arising from single components and can, therefore, be classified as plasmonic molecules. Full article
(This article belongs to the Special Issue Colloidal Nanocrystals: Synthesis, Characterization and Application)
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Open AccessArticle Spacer-Controlled Supramolecular Assemblies of Cu(II) with Bis(2-Hydroxyphenylimine) Ligands. from Monoligand Complexes to Double-Stranded Helicates and Metallomacrocycles
Crystals 2016, 6(9), 120; doi:10.3390/cryst6090120
Received: 28 August 2016 / Revised: 13 September 2016 / Accepted: 14 September 2016 / Published: 21 September 2016
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Abstract
Reaction of Cu(NO3)2·3H2O or Cu(CH3COO)2·H2O with the bis(2-hydroxyphenylimine) ligands H2L1-H2L4 gave four Cu(II) complexes of composition [Cu2(L1)(NO3
[...] Read more.
Reaction of Cu(NO3)2·3H2O or Cu(CH3COO)2·H2O with the bis(2-hydroxyphenylimine) ligands H2L1-H2L4 gave four Cu(II) complexes of composition [Cu2(L1)(NO3)2(H2O)]·MeOH, [Cu2(L2)2], [Cu2(L3)2] and [Cu2(L4)2]·2MeOH. Depending on the spacer unit, the structures are characterized by a dinuclear arrangement of Cu(II) within one ligand (H2L1), by a double-stranded [2+2] helical binding mode (H2L2 and H2L3) and a [2 + 2] metallomacrocycle formation (H2L4). In these complexes, the Cu(II) coordination geometries are quite different, varying between common square planar or square pyramidal arrangements, and rather rare pentagonal bipyramidal and tetrahedral geometries. In addition, solution studies of the complex formation using UV/Vis and ESI-MS as well as solvent extraction are reported. Full article
(This article belongs to the Special Issue Crystal Structure of Complex Compounds)
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Review

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Open AccessReview Statistical Approach to Diffraction of Periodic and Non-Periodic Crystals—Review
Crystals 2016, 6(9), 104; doi:10.3390/cryst6090104
Received: 18 July 2016 / Revised: 12 August 2016 / Accepted: 22 August 2016 / Published: 26 August 2016
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Abstract
In this paper, we show the fundamentals of statistical method of structure analysis. Basic concept of a method is the average unit cell, which is a probability distribution of atomic positions with respect to some reference lattices. The distribution carries complete structural information
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In this paper, we show the fundamentals of statistical method of structure analysis. Basic concept of a method is the average unit cell, which is a probability distribution of atomic positions with respect to some reference lattices. The distribution carries complete structural information required for structure determination via diffraction experiment regardless of the inner symmetry of diffracting medium. The shape of envelope function that connects all diffraction maxima can be derived as the Fourier transform of a distribution function. Moreover, distributions are sensitive to any disorder introduced to ideal structure—phonons and phasons. The latter are particularly important in case of quasicrystals. The statistical method deals very well with phason flips and may be used to redefine phasonic Debye-Waller correction factor. The statistical approach can be also successfully applied to the peak’s profile interpretation. It will be shown that the average unit cell can be equally well applied to a description of Bragg peaks as well as other components of diffraction pattern, namely continuous and singular continuous components. Calculations performed within statistical method are equivalent to the ones from multidimensional analysis. The atomic surface, also called occupation domain, which is the basic concept behind multidimensional models, acquires physical interpretation if compared to average unit cell. The statistical method applied to diffraction analysis is now a complete theory, which deals equally well with periodic and non-periodic crystals, including quasicrystals. The method easily meets also any structural disorder. Full article
(This article belongs to the Special Issue Structure and Properties of Quasicrystals 2016)
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Open AccessReview A Review of Transmission Electron Microscopy of Quasicrystals—How Are Atoms Arranged?
Crystals 2016, 6(9), 105; doi:10.3390/cryst6090105
Received: 30 June 2016 / Revised: 9 August 2016 / Accepted: 15 August 2016 / Published: 26 August 2016
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Abstract
Quasicrystals (QCs) possess rotational symmetries forbidden in the conventional crystallography and lack translational symmetries. Their atoms are arranged in an ordered but non-periodic way. Transmission electron microscopy (TEM) was the right tool to discover such exotic materials and has always been a main
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Quasicrystals (QCs) possess rotational symmetries forbidden in the conventional crystallography and lack translational symmetries. Their atoms are arranged in an ordered but non-periodic way. Transmission electron microscopy (TEM) was the right tool to discover such exotic materials and has always been a main technique in their studies since then. It provides the morphological and crystallographic information and images of real atomic arrangements of QCs. In this review, we summarized the achievements of the study of QCs using TEM, providing intriguing structural details of QCs unveiled by TEM analyses. The main findings on the symmetry, local atomic arrangement and chemical order of QCs are illustrated. Full article
(This article belongs to the Special Issue Structure and Properties of Quasicrystals 2016)
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Open AccessReview Van Der Waals Heterostructures between Small Organic Molecules and Layered Substrates
Crystals 2016, 6(9), 113; doi:10.3390/cryst6090113
Received: 16 July 2016 / Revised: 27 August 2016 / Accepted: 30 August 2016 / Published: 9 September 2016
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Abstract
Two dimensional atomic crystals, like grapheme (G) and molybdenum disulfide (MoS2), exhibit great interest in electronic and optoelectronic applications. The excellent physical properties, such as transparency, semiconductivity, and flexibility, make them compatible with current organic electronics. Here, we review recent progress
[...] Read more.
Two dimensional atomic crystals, like grapheme (G) and molybdenum disulfide (MoS2), exhibit great interest in electronic and optoelectronic applications. The excellent physical properties, such as transparency, semiconductivity, and flexibility, make them compatible with current organic electronics. Here, we review recent progress in the understanding of the interfaces of van der Waals (vdW) heterostructures between small organic molecules (pentacene, copper phthalocyanine (CuPc), perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA), and dioctylbenzothienobenzothiophene (C8-BTBT)) and layered substrates (G, MoS2 and hexagonal boron nitride (h-BN)). The influences of the underlying layered substrates on the molecular arrangement, electronic and vibrational properties will be addressed. Full article
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Open AccessConcept Paper Two-Level Electron Excitations and Distinctive Physical Properties of Al-Cu-Fe Quasicrystals
Crystals 2016, 6(9), 119; doi:10.3390/cryst6090119
Received: 1 July 2016 / Revised: 8 September 2016 / Accepted: 12 September 2016 / Published: 19 September 2016
Cited by 1 | PDF Full-text (1993 KB) | HTML Full-text | XML Full-text
Abstract
This article is not a review in the conventional sense. Rather, it is a monographic study of the implications of detection in Al-Cu-Fe quasicrystals of the electronic heat capacity contributions associated with the two-level electron excitations. Our aim was to reveal correlations between
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This article is not a review in the conventional sense. Rather, it is a monographic study of the implications of detection in Al-Cu-Fe quasicrystals of the electronic heat capacity contributions associated with the two-level electron excitations. Our aim was to reveal correlations between these contributions, on the one hand, and specific features of electron transport, magnetic susceptibility, Hall-effect, tunnelling and optical spectra, on the other hand. It is shown that the full range of these features can be understood in the framework of the unified conceptual scheme based on two-level electron excitations. Full article
(This article belongs to the Special Issue Structure and Properties of Quasicrystals 2016)
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