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Crystals, Volume 6, Issue 8 (August 2016) – 16 articles

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Open AccessReview
Graphene-Like ZnO: A Mini Review
Crystals 2016, 6(8), 100; https://doi.org/10.3390/cryst6080100 - 22 Aug 2016
Cited by 55 | Viewed by 4715
Abstract
The isolation of a single layer of graphite, known today as graphene, not only demonstrated amazing new properties but also paved the way for a new class of materials often referred to as two-dimensional (2D) materials. Beyond graphene, other 2D materials include h-BN, [...] Read more.
The isolation of a single layer of graphite, known today as graphene, not only demonstrated amazing new properties but also paved the way for a new class of materials often referred to as two-dimensional (2D) materials. Beyond graphene, other 2D materials include h-BN, transition metal dichalcogenides (TMDs), silicene, and germanene, to name a few. All tend to have exciting physical and chemical properties which appear due to dimensionality effects and modulation of their band structure. A more recent member of the 2D family is graphene-like zinc oxide (g-ZnO) which also holds great promise as a future functional material. This review examines current progress in the synthesis and characterization of g-ZnO. In addition, an overview of works dealing with the properties of g-ZnO both in its pristine form and modified forms (e.g., nano-ribbon, doped material, etc.) is presented. Finally, discussions/studies on the potential applications of g-ZnO are reviewed and discussed. Full article
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Open AccessCommunication
Photonic Crystals with an Eye Pattern Similar to Peacock Tail Feathers
Crystals 2016, 6(8), 99; https://doi.org/10.3390/cryst6080099 - 20 Aug 2016
Cited by 12 | Viewed by 2891
Abstract
A facile fabrication of photonic crystals (PCs) with an eye pattern similar to peacock tail feathers has been demonstrated by self-assembly of colloidal particles in a sandwich mode. The sandwich mode is formed by superhydrophilic flat substrate sandwiching the poly(styrene-methyl methacrylate-arylic acid) (Poly(St-MMA-AA)) [...] Read more.
A facile fabrication of photonic crystals (PCs) with an eye pattern similar to peacock tail feathers has been demonstrated by self-assembly of colloidal particles in a sandwich mode. The sandwich mode is formed by superhydrophilic flat substrate sandwiching the poly(styrene-methyl methacrylate-arylic acid) (Poly(St-MMA-AA)) latex suspension (2 wt%) by the hydrophobic one. The patterns are characterized by optical microscopy images, reflection spectra, and the relative scanning electronic microscope images. This work will provide beneficial help for the understanding of the self-assembly process of colloidal crystals. Full article
(This article belongs to the Special Issue Colloidal Crystals)
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Open AccessArticle
Single Crystal Growth of Pure Co3+ Oxidation State Material LaSrCoO4
Crystals 2016, 6(8), 98; https://doi.org/10.3390/cryst6080098 - 18 Aug 2016
Cited by 10 | Viewed by 2923
Abstract
We report on the single crystal growth of the single-layer perovskite cobaltate LaSrCoO4 that was grown by the optical floating zone method using high oxygen pressures. Phase purity and single crystallinity were confirmed by X-ray diffraction techniques. The pure Co3+ oxidation [...] Read more.
We report on the single crystal growth of the single-layer perovskite cobaltate LaSrCoO4 that was grown by the optical floating zone method using high oxygen pressures. Phase purity and single crystallinity were confirmed by X-ray diffraction techniques. The pure Co3+ oxidation state was confirmed by X-ray absorbtion spectroscopy measurements. A transition to a spin glass state is observed at ∼7 K in magnetic susceptibility and specific heat measurements. Full article
(This article belongs to the Special Issue Traveling Solvent Floating Zone (TSFZ) Method in Crystal Growth)
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Open AccessFeature PaperReview
3D DNA Crystals and Nanotechnology
Crystals 2016, 6(8), 97; https://doi.org/10.3390/cryst6080097 - 18 Aug 2016
Cited by 11 | Viewed by 4172
Abstract
DNA’s molecular recognition properties have made it one of the most widely used biomacromolecular construction materials. The programmed assembly of DNA oligonucleotides has been used to create complex 2D and 3D self-assembled architectures and to guide the assembly of other molecules. The origins [...] Read more.
DNA’s molecular recognition properties have made it one of the most widely used biomacromolecular construction materials. The programmed assembly of DNA oligonucleotides has been used to create complex 2D and 3D self-assembled architectures and to guide the assembly of other molecules. The origins of DNA nanotechnology are rooted in the goal of assembling DNA molecules into designed periodic arrays, i.e., crystals. Here, we highlight several DNA crystal structures, the progress made in designing DNA crystals, and look at the current prospects and future directions of DNA crystals in nanotechnology. Full article
(This article belongs to the Special Issue Nucleic Acid Crystallography)
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Open AccessArticle
Elastodynamic Analysis of a Hollow Cylinder with Decagonal Quasicrystal Properties: Meshless Implementation of Local Integral Equations
Crystals 2016, 6(8), 94; https://doi.org/10.3390/cryst6080094 - 17 Aug 2016
Cited by 3 | Viewed by 2098
Abstract
A meshless approximation and local integral equation (LIE) formulation are proposed for elastodynamic analysis of a hollow cylinder made of quasicrystal materials with decagonal quasicrystal properties. The cylinder is assumed to be under shock loading. Therefore, the general transient elastodynamic problem is considered [...] Read more.
A meshless approximation and local integral equation (LIE) formulation are proposed for elastodynamic analysis of a hollow cylinder made of quasicrystal materials with decagonal quasicrystal properties. The cylinder is assumed to be under shock loading. Therefore, the general transient elastodynamic problem is considered for coupled phonon and phason displacements and stresses. The equations of motion in the theory of compatible elastodynamics of wave type for phonons and wave-telegraph type for phasons are employed and can be easily modified to the elasto-hydro dynamic equations for quasicrystals (QCs). The angular dependence of the tensor of phonon–phason coupling coefficients handicaps utilization of polar coordinates, when the governing equations would be given by partial differential equations with variable coefficients. Despite the symmetry of the geometrical shape, the local weak formulation and meshless approximation are developed in the Cartesian coordinate system. The response of the cylinder in terms of both phonon and phason stress fields is obtained and studied in detail. Full article
(This article belongs to the Special Issue Structure and Properties of Quasicrystals 2016)
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Open AccessArticle
Technique for High-Quality Protein Crystal Growth by Control of Subgrain Formation under an External Electric Field
Crystals 2016, 6(8), 95; https://doi.org/10.3390/cryst6080095 - 16 Aug 2016
Cited by 8 | Viewed by 2536
Abstract
X-ray diffraction (XRD) rocking-curves were measured for tetragonal hen egg white (HEW) lysozyme crystals grown with and without application of an external electric field, and the crystal quality was assessed according to the full width at half-maximums (FWHMs) of each rocking-curve profile. The [...] Read more.
X-ray diffraction (XRD) rocking-curves were measured for tetragonal hen egg white (HEW) lysozyme crystals grown with and without application of an external electric field, and the crystal quality was assessed according to the full width at half-maximums (FWHMs) of each rocking-curve profile. The average FWHMs for tetragonal HEW lysozyme crystals grown with an external electric field at 1 MHz were smaller than those for crystals grown without, especially for the 12 12 0 reflection. The crystal homogeneity of the tetragonal HEW lysozyme crystals was also improved under application of an external electric field at 1 MHz, compared to that without. Improvement of the crystal quality of tetragonal HEW lysozyme crystals grown under an applied field is discussed with a focus on subgrain formation. In addition, the origin of subgrain misorientation is also discussed with respect to the incorporation of impurities into protein crystals. Full article
(This article belongs to the Special Issue Crystal Dislocations)
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Open AccessArticle
An Exact Method to Determine the Photonic Resonances of Quasicrystals Based on Discrete Fourier Harmonics of Higher-Dimensional Atomic Surfaces
Crystals 2016, 6(8), 93; https://doi.org/10.3390/cryst6080093 - 10 Aug 2016
Cited by 2 | Viewed by 2543
Abstract
A rigorous method for obtaining the diffraction patterns of quasicrystals is presented. Diffraction patterns are an essential analytical tool in the study of quasicrystals, since they can be used to determine their photonic resonances. Previous methods for approximating the diffraction patterns of quasicrystals [...] Read more.
A rigorous method for obtaining the diffraction patterns of quasicrystals is presented. Diffraction patterns are an essential analytical tool in the study of quasicrystals, since they can be used to determine their photonic resonances. Previous methods for approximating the diffraction patterns of quasicrystals have relied on evaluating the Fourier transform of finite-sized super-lattices. Our approach, on the other hand, is exact in the sense that it is based on a technique that embeds quasicrystals into higher dimensional periodic hyper-lattices, thereby completely capturing the properties of the infinite structure. The periodicity of the unit cell in the higher dimensional space can be exploited to obtain the Fourier series expansion in closed-form of the corresponding atomic surfaces. The utility of the method is demonstrated by applying it to one-dimensional Fibonacci and two-dimensional Penrose quasicrystals. The results are verified by comparing them to those obtained by using the conventional super-lattice method. It is shown that the conventional super-cell approach can lead to inaccurate results due to the continuous nature of the Fourier transform, since quasicrystals have a discrete spectrum, whereas the approach introduced in this paper generates discrete Fourier harmonics. Furthermore, the conventional approach requires very large super-cells and high-resolution sampling of the reciprocal space in order to produce accurate results leading to a very large computational burden, whereas the proposed method generates accurate results with a relatively small number of terms. Finally, we propose how this approach can be generalized from the vertex model, which assumes identical particles at all vertices, to a more realistic case where the quasicrystal is composed of different atoms. Full article
(This article belongs to the Special Issue Structure and Properties of Quasicrystals 2016)
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Open AccessReview
Strategies to Approach Stabilized Plasticity in Metals with Diminutive Volume: A Brief Review
Crystals 2016, 6(8), 92; https://doi.org/10.3390/cryst6080092 - 09 Aug 2016
Cited by 2 | Viewed by 1698
Abstract
Micrometer- or submicrometer-sized metallic pillars are widely studied by investigators worldwide, not only to provide insights into fundamental phenomena, but also to explore potential applications in microelectromechanical system (MEMS) devices. While these materials with a diminutive volume exhibit unprecedented properties, e.g., strength values [...] Read more.
Micrometer- or submicrometer-sized metallic pillars are widely studied by investigators worldwide, not only to provide insights into fundamental phenomena, but also to explore potential applications in microelectromechanical system (MEMS) devices. While these materials with a diminutive volume exhibit unprecedented properties, e.g., strength values that approach the theoretical strength, their plastic flow is frequently intermittent as manifested by strain bursts, which is mainly attributed to dislocation activity at such length scales. Specifically, the increased ratio of free surface to volume promotes collective dislocation release resulting in dislocation starvation at the submicrometer scale or the formation of single-arm dislocation sources (truncated dislocations) at the micrometer scale. This article reviews and critically assesses recent progress in tailoring the microstructure of pillars, both extrinsically and intrinsically, to suppress plastic instabilities in micrometer or submicrometer-sized metallic pillars using an approach that involves confining the dislocations inside the pillars. Moreover, we identify strategies that can be implemented to fabricate submicrometer-sized metallic pillars that simultaneously exhibit stabilized plasticity and ultrahigh strength. Full article
(This article belongs to the Special Issue Crystal Dislocations)
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Open AccessArticle
Metal(II) Complexes of Compartmental Polynuclear Schiff Bases Containing Phenolate and Alkoxy Groups
Crystals 2016, 6(8), 91; https://doi.org/10.3390/cryst6080091 - 09 Aug 2016
Cited by 6 | Viewed by 2136
Abstract
Five mono-nuclear Cu(II) and Ni(II) complexes and one dinuclear Zn(II) complex were synthesized from the Schiff bases N,N'-bis(3-ethoxy-2-hydroxybenzylidene)-1,2-phenylenediamine (H2LOEt-phda) and 2-ethoxy-6-({2-[(3-ethoxy-2-hydroxybenzylidene)amino]-benzyl}iminomethyl)phenol (H2LOEt-ambza): [Cu(LOEt-phda)(H2O)].H2O (1), [Ni(L [...] Read more.
Five mono-nuclear Cu(II) and Ni(II) complexes and one dinuclear Zn(II) complex were synthesized from the Schiff bases N,N'-bis(3-ethoxy-2-hydroxybenzylidene)-1,2-phenylenediamine (H2LOEt-phda) and 2-ethoxy-6-({2-[(3-ethoxy-2-hydroxybenzylidene)amino]-benzyl}iminomethyl)phenol (H2LOEt-ambza): [Cu(LOEt-phda)(H2O)].H2O (1), [Ni(LOEt-phda)].H2O (2), [Cu(LOEt-ambza)].H2O·EtOH (3), [Cu(LOEt-ambza)].H2O (4), [Ni(LOEt-ambza)] (5) and [Zn2(LOEt-ambza)(μ-OAc)(OAc)] (6). The complexes were structurally characterized with elemental microanalyses, IR, UV-Vis and ESI-MS spectroscopic techniques as well as single crystal X-ray crystallography. The metal centers display distorted square planar geometries in 24 and 5 and distorted square pyramidal (SP) in 1, whereas in 6 an intermediate geometry between SP and TBP was observed around the first Zn2+ ion and a tetrahedral around the second ion, with one acetate is acting as a bridging ligand. In all cases, metal ions were incorporated into the N2-O2 binding site with no involvement of the alkoxy groups in the coordination. The LOEt-ambza-complexes 36 revealed significant dihedral angles between the phenol rings and the plane containing the central benzene ring, and large O2-O2 bond distances (5.1-5.9 Ǻ). Results are discussed in relation to other related Schiff base complexes. Full article
(This article belongs to the Special Issue Crystal Structure of Complex Compounds)
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Open AccessArticle
Bisphthalonitrile with a Disulfide-Based Linker and its Dimethylene Analogue: Comparative Structural Insights
Crystals 2016, 6(8), 89; https://doi.org/10.3390/cryst6080089 - 09 Aug 2016
Cited by 1 | Viewed by 1832
Abstract
Phthalonitriles are key precursors of phthalocyanines. Self-quenching dimeric phthalocyanines likely to be cleaved into monomeric species are of potential interest for tumour-site activated photosensitisers. Disulfide linkers can be specifically cleaved in tumoral tissue do to their reductive nature. Hence, a disulfide-linked phthalonitrile was [...] Read more.
Phthalonitriles are key precursors of phthalocyanines. Self-quenching dimeric phthalocyanines likely to be cleaved into monomeric species are of potential interest for tumour-site activated photosensitisers. Disulfide linkers can be specifically cleaved in tumoral tissue do to their reductive nature. Hence, a disulfide-linked phthalonitrile was designed to serve as further precursor of specifically tumour-activatable phthalocyanine-based photosensitising systems. Bisphthalonitrile with a disulfide-based linker and its dimethylene analogue were comparatively analyzed on a spectroscopic point of view as well as with DFT calculations. A thorough crystallographic analysis of the disulfide-linked derivative was conducted. Full article
(This article belongs to the Section Biomolecular Crystals)
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Open AccessArticle
Simulation of Polymer Crystallization under Isothermal and Temperature Gradient Conditions Using Particle Level Set Method
Crystals 2016, 6(8), 90; https://doi.org/10.3390/cryst6080090 - 08 Aug 2016
Cited by 6 | Viewed by 2897
Abstract
Morphological models for polymer crystallization under isothermal and temperature gradient conditions with a particle level set method are proposed. In these models, the particle level set method is used to improve the accuracy in studying crystal interaction. The predicted development of crystallinity during [...] Read more.
Morphological models for polymer crystallization under isothermal and temperature gradient conditions with a particle level set method are proposed. In these models, the particle level set method is used to improve the accuracy in studying crystal interaction. The predicted development of crystallinity during crystallization under quiescent isothermal condition by our model is reanalyzed with the Avrami model, and good agreement between the predicted and theoretical values is observed. In the temperature gradient, the computer simulation results with our model are consistent with the experiment results in the literature. Full article
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Open AccessReview
Mono- and Bimetalic Amidoboranes
Crystals 2016, 6(8), 88; https://doi.org/10.3390/cryst6080088 - 05 Aug 2016
Cited by 23 | Viewed by 2368
Abstract
In this review, we present an overview on metal amidoboranes, which have recently been considered as hydrogen storage materials for fueling of the low temperature fuel cells. We focus on amidoborane salts containing only metal cations and amidoborate anions. During the last decades, [...] Read more.
In this review, we present an overview on metal amidoboranes, which have recently been considered as hydrogen storage materials for fueling of the low temperature fuel cells. We focus on amidoborane salts containing only metal cations and amidoborate anions. During the last decades, 19 new compounds from this group were described in the literature. We provide a summary of various physical and chemical properties of amidoborane compounds reported up to date. Full article
(This article belongs to the Special Issue Boron-Based (Nano-)Materials: Fundamentals and Applications)
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Open AccessReview
X-ray Diffraction: A Powerful Technique for the Multiple-Length-Scale Structural Analysis of Nanomaterials
Crystals 2016, 6(8), 87; https://doi.org/10.3390/cryst6080087 - 04 Aug 2016
Cited by 30 | Viewed by 4856
Abstract
During recent decades innovative nanomaterials have been extensively studied, aiming at both investigating the structure-property relationship and discovering new properties, in order to achieve relevant improvements in current state-of-the art materials. Lately, controlled growth and/or assembly of nanostructures into hierarchical and complex architectures [...] Read more.
During recent decades innovative nanomaterials have been extensively studied, aiming at both investigating the structure-property relationship and discovering new properties, in order to achieve relevant improvements in current state-of-the art materials. Lately, controlled growth and/or assembly of nanostructures into hierarchical and complex architectures have played a key role in engineering novel functionalized materials. Since the structural characterization of such materials is a fundamental step, here we discuss X-ray scattering/diffraction techniques to analyze inorganic nanomaterials under different conditions: dispersed in solutions, dried in powders, embedded in matrix, and deposited onto surfaces or underneath them. Full article
(This article belongs to the Special Issue Colloidal Nanocrystals: Synthesis, Characterization and Application)
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Open AccessArticle
Second-Harmonic Generation in Membrane-Type Nonlinear Acoustic Metamaterials
Crystals 2016, 6(8), 86; https://doi.org/10.3390/cryst6080086 - 29 Jul 2016
Cited by 8 | Viewed by 2593
Abstract
We study analytically and numerically the second-harmonic generation in a one-dimensional nonlinear acoustic metamaterial, composed of an air-filled waveguide periodically loaded by clamped elastic plates. Based on the transmission line approach, we derive a nonlinear dynamical lattice model which, in the continuum approximation, [...] Read more.
We study analytically and numerically the second-harmonic generation in a one-dimensional nonlinear acoustic metamaterial, composed of an air-filled waveguide periodically loaded by clamped elastic plates. Based on the transmission line approach, we derive a nonlinear dynamical lattice model which, in the continuum approximation, leads to a nonlinear dispersive wave equation. By applying the perturbation method to the latter, we derive the analytical expressions for the first- and second-harmonics, which are in excellent agreement with the numerical simulations of the nonlinear dynamical lattice model. Apart from the case of dispersionless nonlinear propagation and the Fubini solution, special attention is payed to the role of dispersion. In that regard, it is found that, once dispersion comes into play, second-harmonic beatings in space due to phase-mismatch can be identified. Our results provide many opportunities for the development of new periodic acoustic structures featuring both nonlinearity and dispersion. Full article
(This article belongs to the Special Issue Phononic Crystals)
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Open AccessArticle
Properties of LiGa0.5In0.5Se2: A Quaternary Chalcogenide Crystal for Nonlinear Optical Applications in the Mid-IR
Crystals 2016, 6(8), 85; https://doi.org/10.3390/cryst6080085 - 28 Jul 2016
Cited by 10 | Viewed by 2212
Abstract
LiGaSe2 (LGSe) and LiInSe2 (LISe) are wide band-gap nonlinear crystals transparent in the mid-IR spectral range. LiGa0.5In0.5Se2 (LGISe) is a new mixed crystal, a solid solution in the system LGSe–LISe, which exhibits the same orthorhombic structure [...] Read more.
LiGaSe2 (LGSe) and LiInSe2 (LISe) are wide band-gap nonlinear crystals transparent in the mid-IR spectral range. LiGa0.5In0.5Se2 (LGISe) is a new mixed crystal, a solid solution in the system LGSe–LISe, which exhibits the same orthorhombic structure (mm2) as the parent compounds in the same time being more technological with regard to the growth process. In comparison with LGSe and LISe its homogeneity range is broader in the phase diagram. About 10% of the Li ions in LGISe occupy octahedral positions (octapores) with coordination number of 3. The band-gap of LGISe is estimated to be 2.94 eV at room temperature and 3.04 eV at 80 K. The transparency at the 0-level extends from 0.47 to 13 µm. LGISe crystals exhibit luminescence in broad bands centered near 1.7 and 1.25 eV which is excited most effectively by band-to-band transition. From the measured principal refractive indices and the fitted Sellmeier equations second-harmonic generation from 1.75 to 11.8 μm (fundamental wavelength) is predicted. The nonlinear coefficients of LGISe have values between those of LGSe and LISe. 6LGISe crystals are considered promising also for detection of thermal neutrons. Full article
(This article belongs to the Special Issue Nonlinear Optical Crystals)
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Open AccessArticle
A Novel Approach to Quantitatively Assess the Uniformity of Binary Colloidal Crystal Assemblies
Crystals 2016, 6(8), 84; https://doi.org/10.3390/cryst6080084 - 26 Jul 2016
Cited by 2 | Viewed by 2213
Abstract
Colloidal self-assembly into highly ordered binary systems represents a versatile and inexpensive approach to generate well defined surface topographical features with submicron resolution. In addition, the use of surface-functionalized particles where each particle bears a different surface functionality enables the generation of highly [...] Read more.
Colloidal self-assembly into highly ordered binary systems represents a versatile and inexpensive approach to generate well defined surface topographical features with submicron resolution. In addition, the use of surface-functionalized particles where each particle bears a different surface functionality enables the generation of highly resolved surface chemical patterns. Such topographical, as well as chemical features, are of great interest in biomaterials science particularly in the context of investigating and controlling the cellular response. While colloidal crystals have been used to generate a wide range of surface patterns, it has not been possible until now to quantitatively describe the degree of uniformity within such systems. In the present work we describe a novel approach to quantitatively assess the uniformity within binary colloidal assemblies based on image processing methods, primarily the Circular Hough Transform and distance calculations. We believe that the methodology presented here will find broad application in the field of colloidal crystals to quantitatively describe the integrity and homogeneity of assemblies. Full article
(This article belongs to the Special Issue Colloidal Crystals)
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