Next Issue
Previous Issue

Table of Contents

Crystals, Volume 9, Issue 3 (March 2019)

  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Readerexternal link to open them.
Cover Story (view full-size image) Cover story: In this paper, we present a study on the evolution of crystal mosaicity during [...] Read more.
View options order results:
result details:
Displaying articles 1-61
Export citation of selected articles as:
Open AccessArticle Elucidation of the Crystal Structures and Dehydration Behaviors of Ondansetron Salts
Crystals 2019, 9(3), 180; https://doi.org/10.3390/cryst9030180
Received: 7 March 2019 / Revised: 24 March 2019 / Accepted: 25 March 2019 / Published: 26 March 2019
Viewed by 264 | PDF Full-text (8824 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In drug development, it is extremely important to evaluate the solubility and stability of solid states and to immediately determine the potential for development. Salt screening is a standard and useful method for obtaining drug candidates with good solid state properties. Ondansetron is [...] Read more.
In drug development, it is extremely important to evaluate the solubility and stability of solid states and to immediately determine the potential for development. Salt screening is a standard and useful method for obtaining drug candidates with good solid state properties. Ondansetron is marketed as a hydrochloride dihydrate, and its dehydration behavior was previously reported to transition to an anhydrate via a hemihydrate as an intermediate by heating. Here, we synthesized ondansetron hydrobromide and hydroiodide and examined their dehydration behaviors. Single-crystal structure analysis confirmed that like ondansetron hydrochloride, ondansetron hydrobromide formed a dihydrate. Moreover, the crystal lattice parameters and hydrogen bonding networks were similar and isomorphic. While single-crystal structure analysis showed that ondansetron hydroiodide also formed a dihydrate, the crystal lattice parameters and hydrogen bonding networks were different to those of ondansetron hydrobromide and hydrochloride. Additionally, the dehydration behavior of ondansetron hydrobromide differed from that of the hydrochloride, with no hemihydrate intermediate forming from the hydrobromide, despite similar anhydrate structures. Given that it is difficult to predict how a crystal structure will form and the resulting physical properties, a large amount of data is needed for the rational design of salt optimization. Full article
(This article belongs to the Special Issue Pharmaceutical Crystals)
Figures

Figure 1

Open AccessReview Prospective of (BaCa)(ZrTi)O3 Lead-free Piezoelectric Ceramics
Crystals 2019, 9(3), 179; https://doi.org/10.3390/cryst9030179
Received: 11 February 2019 / Revised: 4 March 2019 / Accepted: 13 March 2019 / Published: 26 March 2019
Viewed by 246 | PDF Full-text (604 KB) | HTML Full-text | XML Full-text
Abstract
Piezoelectric ceramics is a functional material that can convert mechanical energy into electrical energy and vice versa. It can find wide applications ranging from our daily life to high-end techniques and dominates a billion-dollar market. For half a century, the working horse of [...] Read more.
Piezoelectric ceramics is a functional material that can convert mechanical energy into electrical energy and vice versa. It can find wide applications ranging from our daily life to high-end techniques and dominates a billion-dollar market. For half a century, the working horse of the field has been the polycrystalline PbZr1−xTixO3 (PZT), which is now globally resisted for containing the toxic element lead. In 2009, our group discovered a non-Pb piezoelectric material, (BaCa)(ZrTi)O3 ceramics (BZT-BCT), which exhibits an ultrahigh piezoelectric coefficient d33 of 560–620 pC/N. This result brought extensive interest in the research field and important consequences for the piezoelectric industry that has relied on PZT. In the present paper, we review the recent progress, both experimental and theoretical, in the BZT-BCT ceramics. Full article
(This article belongs to the Special Issue Synthesis and Characterization of Ferroelectrics)
Figures

Figure 1

Open AccessArticle Study of Liquid Crystals Showing Two Isotropic Phases by 1H NMR Diffusometry and 1H NMR Relaxometry
Crystals 2019, 9(3), 178; https://doi.org/10.3390/cryst9030178
Received: 24 February 2019 / Revised: 21 March 2019 / Accepted: 23 March 2019 / Published: 26 March 2019
Viewed by 284 | PDF Full-text (2309 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this work, we report a study of two thermotropic liquid crystalline samples showing a not common mesophase behavior. The samples, namely a di-benzyloxy biphenyl derivative labelled 9/2 RS/RS, and a bimesogenic liquid crystal labelled L1, show a direct transition between [...] Read more.
In this work, we report a study of two thermotropic liquid crystalline samples showing a not common mesophase behavior. The samples, namely a di-benzyloxy biphenyl derivative labelled 9/2 RS/RS, and a bimesogenic liquid crystal labelled L1, show a direct transition between two isotropic phases followed, at lower temperatures, by the optically isotropic, 3D structured, cubic phase. These systems have been investigated by means of 1H NMR diffusometry and 1H NMR relaxometry in order to characterize their isotropic–isotropic’–cubic mesophase behavior, mainly on the dynamic point of view. In particular, the temperature trend of the self-diffusion coefficients measured for both samples allowed us to significantly distinguish between the two isotropic phases, while the temperature dependence of the 1H spin-lattice relaxation time (T1) did not show significant discontinuities at the isotropic–isotropic’ phase transition. A preliminary analysis of the frequency-dependence of 1H T1 at different temperatures gives information about the main motional processes active in the isotropic mesophases. Full article
(This article belongs to the Special Issue Nuclear Magnetic Resonance of Liquid Crystals)
Figures

Figure 1

Open AccessArticle Fab Fragment of VHH-Based Antibody Netakimab: Crystal Structure and Modeling Interaction with Cytokine IL-17A
Crystals 2019, 9(3), 177; https://doi.org/10.3390/cryst9030177
Received: 1 March 2019 / Revised: 15 March 2019 / Accepted: 21 March 2019 / Published: 26 March 2019
Viewed by 239 | PDF Full-text (3591 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Interleukin 17A (IL-17A) is a proinflammatory cytokine produced by Th17 cells. Antibody BCD-085 (netakimab) against human IL-17A is one of the new inhibitors of this cytokine. In netakimab, the VH domain is replaced by the VHH domain of Lama glama [...] Read more.
Interleukin 17A (IL-17A) is a proinflammatory cytokine produced by Th17 cells. Antibody BCD-085 (netakimab) against human IL-17A is one of the new inhibitors of this cytokine. In netakimab, the VH domain is replaced by the VHH domain of Lama glama possessing a long complementarity determining region (CDR-H3) in its heavy chain. Here we demonstrate the high affinity of IL-17A to the Fab fragment of netakimab and to its integral part, the VHH domain. We have determined the crystal structure of the Fab fragment of netakimab at 1.9 Å resolution. High variability in the orientation of light and heavy chains of the Fab fragment of netakimab was shown, which is determined by the peculiarity of the structural organization of the CDR-H3. As the high conformational plasticity of the molecule hampers modeling the Fab fragment of netakimab complexed to IL-17A, we have carried out modeling the complex between the antigen and the integral part of the Fab fragment, the VHH domain. We explain the high netakimab Fab fragment affinity for IL-17A by a large number of protein–protein contacts due to additional interactions between CDR-H3 and the cytokine dimer. Full article
(This article belongs to the Special Issue Protein Crystallography)
Figures

Figure 1

Open AccessArticle Deep Etched Gallium Nitride Waveguide for Raman Spectroscopic Applications
Crystals 2019, 9(3), 176; https://doi.org/10.3390/cryst9030176
Received: 29 January 2019 / Revised: 22 March 2019 / Accepted: 23 March 2019 / Published: 26 March 2019
Viewed by 352 | PDF Full-text (4700 KB) | HTML Full-text | XML Full-text
Abstract
Gallium nitride (GaN) materials with a high chemical stability and biocompatibility are well suited for bio-sensing applications and evanescent wave spectroscopy. However, GaN poses challenges for processing, especially for deep etching using conventional etching techniques. Here, we present a dry-etching technique using tetraethyl [...] Read more.
Gallium nitride (GaN) materials with a high chemical stability and biocompatibility are well suited for bio-sensing applications and evanescent wave spectroscopy. However, GaN poses challenges for processing, especially for deep etching using conventional etching techniques. Here, we present a dry-etching technique using tetraethyl orthosilicate (TEOS) oxide as an etching barrier. We demonstrate that a sharp, vertically-etched waveguide pattern can be obtained with low surface roughness. The fabricated GaN waveguide structure is further characterized using field-emission scanning electron microscopy, Raman spectroscopy, and a stylus profilometer. Full article
(This article belongs to the Special Issue GaN-Based Optoelectronic Materials and Light Emitting Devices)
Figures

Figure 1

Open AccessArticle Synthesis, Structures and Co-Crystallizations of Perfluorophenyl Substituted β-Diketone and Triketone Compounds
Crystals 2019, 9(3), 175; https://doi.org/10.3390/cryst9030175
Received: 26 February 2019 / Revised: 15 March 2019 / Accepted: 21 March 2019 / Published: 25 March 2019
Viewed by 249 | PDF Full-text (3394 KB) | HTML Full-text | XML Full-text
Abstract
Perfluorophenyl-substituted compounds, 3-hydroxy-1,3-bis(pentafluorophenyl)-2- propen-1-one (H1) and 1,5-dihydroxy-1,5-bis(pentafluorophenyl)-1,4-pentadien-3-one (H22), were prepared in 56 and 30% yields, respectively, and only the enol forms were preferentially obtained among the keto-enol tautomerism. Molecular conformations and tautomerism of the fluorine-substituted compounds were certified [...] Read more.
Perfluorophenyl-substituted compounds, 3-hydroxy-1,3-bis(pentafluorophenyl)-2- propen-1-one (H1) and 1,5-dihydroxy-1,5-bis(pentafluorophenyl)-1,4-pentadien-3-one (H22), were prepared in 56 and 30% yields, respectively, and only the enol forms were preferentially obtained among the keto-enol tautomerism. Molecular conformations and tautomerism of the fluorine-substituted compounds were certified based on X-ray crystallographic studies and density functional calculations. The solvent dependency of the absorption spectra was only observed for the fluorinated compounds. The compounds H1 and H22 quantitatively formed co-crystals with the corresponding non-perfluorinated compounds, dibenzoylmethane (H3) and 1,5-dihydroxy-1,5-diphenyl-1,4-pentadien-3-one (H24), respectively, through the arene–perfluoroarene interaction to give the 1:1 co-crystals H1•H3 and H22•H24, which were characterized by X-ray crystallographic and elemental analysis studies. Full article
(This article belongs to the Special Issue Halogen-Bonded Cocrystals)
Figures

Graphical abstract

Open AccessArticle Numerical Simulation of Temperature and Fluid Fields in Solidification Process of Ferritic Stainless Steel under Vibration Conditions
Crystals 2019, 9(3), 174; https://doi.org/10.3390/cryst9030174
Received: 22 February 2019 / Revised: 16 March 2019 / Accepted: 21 March 2019 / Published: 25 March 2019
Viewed by 222 | PDF Full-text (6787 KB) | HTML Full-text | XML Full-text
Abstract
A three-dimensional model of a circular casting mold with a vibrating nucleus generator was established, and the characteristics of temperature and flow fields during the solidification process of ferritic stainless steel Cr17 in the casting mold were analyzed using finite element and finite [...] Read more.
A three-dimensional model of a circular casting mold with a vibrating nucleus generator was established, and the characteristics of temperature and flow fields during the solidification process of ferritic stainless steel Cr17 in the casting mold were analyzed using finite element and finite difference methods. A standard k-ε turbulent current model was adopted to simulate the temperature field, and a standard k-ε model in Reynolds-averaged Navier–Stokes equations (RANS) was employed to deal with the flow field. The temperature field diffuses outward with a positive temperature gradient. Low degrees of undercooling can prevent solidified shells from forming rapidly on the surface of the nucleus generator. The temperature perpendicular to the direction of vibration is lower than that in the direction of vibration. The flow field exhibits a heart-shaped distribution and spreads gradually outward. The uniform distribution of grains can be achieved at three different frequencies of vibration. The results show that the degree of undercooling affects the distribution of the temperature field while the frequency of vibration affects the flow field significantly. Under the conditions of undercooling of 540 K and vibration frequency of 1000 Hz, the region perpendicular to the vibration direction of the nucleus generator is the optimum area for equiaxed crystal formation. Full article
(This article belongs to the Special Issue Nanostructured Ferritic Alloys)
Figures

Figure 1

Open AccessEditorial Ceramic Conductors
Crystals 2019, 9(3), 173; https://doi.org/10.3390/cryst9030173
Received: 21 March 2019 / Accepted: 21 March 2019 / Published: 25 March 2019
Viewed by 232 | PDF Full-text (149 KB) | HTML Full-text | XML Full-text
Abstract
For more than 4000 years, mankind has used and developed ceramics [...] Full article
(This article belongs to the Special Issue Ceramic Conductors)
Open AccessCommunication Effect of High-Density Nanoparticles on Recrystallization and Texture Evolution in Ferritic Alloys
Crystals 2019, 9(3), 172; https://doi.org/10.3390/cryst9030172
Received: 17 March 2019 / Accepted: 21 March 2019 / Published: 24 March 2019
Viewed by 385 | PDF Full-text (4349 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Ferritic alloys are important for nuclear reactor applications due to their microstructural stability, corrosion resistance, and favorable mechanical properties. Nanostructured ferritic alloys having a high density of Y-Ti-O rich nano-oxides (NOs < 5 nm) are found to be extremely stable at high temperatures [...] Read more.
Ferritic alloys are important for nuclear reactor applications due to their microstructural stability, corrosion resistance, and favorable mechanical properties. Nanostructured ferritic alloys having a high density of Y-Ti-O rich nano-oxides (NOs < 5 nm) are found to be extremely stable at high temperatures up to ~1100 °C. This study serves to understand the effect of a high density of nano-particles on texture evolution and recrystallization mechanisms in ferritic alloys of 14YWT (14Cr-3W-0.4Ti-0.21Y-Fe wt %) having a high density of nano-particles and dispersion-free FeCrAl (13Cr-5.2Al-0.05Y-2Mo-0.2Si-1Nb wt %). In order to investigate the recrystallization mechanisms in these alloys, neutron diffraction, electron backscattered diffraction, and in situ and ex situ transmission electron microscopy have been utilized. It has been observed that even though the deformation textures of both the 14YWT and FeCrAl alloys evolved similarly, resulting in either the formation (in FeCrAl alloy) or increase (in 14YWT) in γ-fiber texture, the texture evolution during recrystallization is different. While FeCrAl alloy keeps its γ-fiber texture after recrystallization, 14YWT samples develop a ε-fiber as a result of annealing at 1100 °C, which can be attributed to the existence of NOs. In situ transmission electron microscopy annealing experiments on 14YWT show the combination and growth of the lamellar grains rather than nucleation; however, the recrystallization and growth kinetics are slower due to NOs compared to FeCrAl. Full article
(This article belongs to the Special Issue Nanostructured Ferritic Alloys)
Figures

Graphical abstract

Open AccessArticle Impact of Weak Nanoparticle Induced Disorder on Nematic Ordering
Crystals 2019, 9(3), 171; https://doi.org/10.3390/cryst9030171
Received: 28 February 2019 / Revised: 20 March 2019 / Accepted: 22 March 2019 / Published: 24 March 2019
Viewed by 343 | PDF Full-text (1559 KB) | HTML Full-text | XML Full-text
Abstract
Dilute mixtures of nanoparticles (NPs) and nematic liquid crystals (LCs) are considered. We focus on cases where NPs enforce a relatively weak disorder to the LC host. We use a Lebwohl-Lasher semi-microscopic-type modeling where we assume that NPs effectively act as a spatially-dependent [...] Read more.
Dilute mixtures of nanoparticles (NPs) and nematic liquid crystals (LCs) are considered. We focus on cases where NPs enforce a relatively weak disorder to the LC host. We use a Lebwohl-Lasher semi-microscopic-type modeling where we assume that NPs effectively act as a spatially-dependent external field on nematic spins. The orientational distribution of locally favoured “easy” orientations is described by a probabilistic distribution function P. By means of a mean field-type approach, we derive a self-consistent equation for the average degree of nematic uniaxial order parameter S as a function of the concentration p of NPs, NP-LC coupling strength and P. Using a simple step-like probability distribution shape, we obtain the S(p) dependence displaying a crossover behaviour between two different regimes which is in line with recent experimental observations. We also discuss a possible origin of commonly observed non-monotonous variations of the nematic-isotropic phase temperature coexistence width on varying p. Full article
(This article belongs to the Section Liquid Crystals)
Figures

Figure 1

Open AccessArticle Optical Characterization and Photovoltaic Performance Evaluation of GaAs p-i-n Solar Cells with Various Metal Grid Spacings
Crystals 2019, 9(3), 170; https://doi.org/10.3390/cryst9030170
Received: 28 February 2019 / Revised: 16 March 2019 / Accepted: 19 March 2019 / Published: 22 March 2019
Viewed by 227 | PDF Full-text (1492 KB) | HTML Full-text | XML Full-text
Abstract
GaAs p-i-n solar cells are studied using electroreflectance (ER) spectroscopy, light beam induced current (LBIC) mapping and photovoltaic characterization. Using ER measurements, the electric field across the pn junction of a wafer can be evaluated, showing 167 kV/cm and 275 kV/cm in the [...] Read more.
GaAs p-i-n solar cells are studied using electroreflectance (ER) spectroscopy, light beam induced current (LBIC) mapping and photovoltaic characterization. Using ER measurements, the electric field across the pn junction of a wafer can be evaluated, showing 167 kV/cm and 275 kV/cm in the built-in condition and at −3 V reverse bias, respectively. In order to understand the effect of the interval between metal grids on the device’s solar performance, we performed LBIC mapping and solar illumination on samples of different grid spacings. We found that the integrated photocurrent intensity of LBIC mapping shows a consistent trend with the solar performance of the devices with various metal grid spacings. For the wafer used in this study, the optimal grid spacing was found to be around 300 μm. Our results clearly show the importance of the metal grid pattern in achieving high-efficiency solar cells. Full article
(This article belongs to the Special Issue III-V Heteroepitaxy for Solar Energy Conversion)
Figures

Figure 1

Open AccessArticle Power Allocation Optimization Design for the Quadrichromatic LED Based VLC Systems with Illumination Control
Crystals 2019, 9(3), 169; https://doi.org/10.3390/cryst9030169
Received: 13 February 2019 / Revised: 19 March 2019 / Accepted: 20 March 2019 / Published: 22 March 2019
Viewed by 222 | PDF Full-text (1223 KB) | HTML Full-text | XML Full-text
Abstract
For requiring high communication rate and high-quality illumination, multi-color light-emitting diodes (LEDs) have been utilized in visible light communication (VLC) systems and attracted substantial research interests. It should be noted that multiple colors are not independent from each other since they are jointly [...] Read more.
For requiring high communication rate and high-quality illumination, multi-color light-emitting diodes (LEDs) have been utilized in visible light communication (VLC) systems and attracted substantial research interests. It should be noted that multiple colors are not independent from each other since they are jointly limited by the chromaticity constraint. Thus, taking full consideration of the multi-color crosstalk problem and actual communication and illumination constraints, this paper formulates a power-efficient illumination control optimization design to reduce power consumption for the quadrichromatic LED (QLED) based VLC systems where signal to interference plus noise ratio (SINR) and quadrangle chromaticity tolerance region constraints should be satisfied. Simulation results illustrate that our proposed optimal power allocation strategy can significantly increase power efficiency for the VLC system compared with the uniform power allocation method. Moreover, the proposed scheme can provide optimal performance under different given correlated color temperature (CCT) values. Full article
(This article belongs to the Special Issue Recent Advances in Light-Emitting Diodes (LEDs))
Figures

Figure 1

Open AccessArticle Diode-Pumped Actively Q-Switched Nd:YVO4/RTP Intracavity Raman Laser at 1.49 µm
Crystals 2019, 9(3), 168; https://doi.org/10.3390/cryst9030168
Received: 19 February 2019 / Revised: 15 March 2019 / Accepted: 18 March 2019 / Published: 22 March 2019
Viewed by 244 | PDF Full-text (2252 KB) | HTML Full-text | XML Full-text
Abstract
For the first time, a diode-pumped actively Q-switched Nd:YVO4/RbTiOPO4 (RTP) intracavity Raman laser at 1.49 µm was demonstrated to the best of our knowledge. Experimentally, a dual-end diffusion-bonded YVO4–Nd:YVO4–YVO4 crystal was employed as the laser [...] Read more.
For the first time, a diode-pumped actively Q-switched Nd:YVO4/RbTiOPO4 (RTP) intracavity Raman laser at 1.49 µm was demonstrated to the best of our knowledge. Experimentally, a dual-end diffusion-bonded YVO4–Nd:YVO4–YVO4 crystal was employed as the laser medium to generate 1.34 µm laser radiation, and an RTP crystal as the Raman medium to enable the frequency conversion, by which radiation at 1.49 µm was achieved successfully. With an incident pump power of 10.4 W, an average output power of 502 mW was obtained at a pulse repetition rate of 15 kHz, corresponding to a conversion efficiency of 4.8%. Full article
(This article belongs to the Special Issue Crystalline Raman Lasers)
Figures

Figure 1

Open AccessArticle Stimulated Raman Scattering in Alkali-Earth Tungstate and Molybdate Crystals at Both Stretching and Bending Raman Modes under Synchronous Picosecond Pumping with Multiple Pulse Shortening Down to 1 ps
Crystals 2019, 9(3), 167; https://doi.org/10.3390/cryst9030167
Received: 20 February 2019 / Revised: 15 March 2019 / Accepted: 17 March 2019 / Published: 21 March 2019
Viewed by 205 | PDF Full-text (3261 KB) | HTML Full-text | XML Full-text
Abstract
Comparative investigation of characteristics of spontaneous and stimulated Raman scattering (SRS) in different alkali-earth tungstate and molybdate crystals at both high and low frequency anionic group vibrations is presented. It has been found that, among these crystals, the SrMoO4 and SrWO4 [...] Read more.
Comparative investigation of characteristics of spontaneous and stimulated Raman scattering (SRS) in different alkali-earth tungstate and molybdate crystals at both high and low frequency anionic group vibrations is presented. It has been found that, among these crystals, the SrMoO4 and SrWO4 crystals are the most perspective for SRS generation on both stretching and bending modes of internal anionic group vibrations with the strongest SRS pulse shortening under synchronous laser pumping because of not only highly intense stretching mode Raman line for efficient primary extra cavity long-shifted SRS conversion but also the widest bending mode Raman line for the strongest SRS pulse shortening down to the inverse width of the widest Raman line (~1 ps) at secondary intracavity short-shifted SRS conversion. The strongest 26-fold pump pulse shortening down to 1.4 ps at the Stokes component with the combined Raman shift in the synchronously pumped extra cavity SrMoO4 and SrWO4 Raman lasers has been demonstrated. It was found that synchronously pumped cascade SRS with combined Raman shift is more efficient in the SrWO4 crystal because the bending mode Raman line is more intense relative to the stretching mode Raman line than that in SrMoO4. Full article
(This article belongs to the Special Issue Crystalline Raman Lasers)
Figures

Figure 1

Open AccessArticle Synthesis, Crystal Structures, and Magnetic Properties of Three Cobalt(II) Coordination Polymers Constructed from 3,5-Pyridinedicarboxylic Acid or 3,4-Pyridinedicarboxylic Acid Ligands
Crystals 2019, 9(3), 166; https://doi.org/10.3390/cryst9030166
Received: 27 January 2019 / Revised: 17 March 2019 / Accepted: 18 March 2019 / Published: 21 March 2019
Viewed by 240 | PDF Full-text (2929 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Three 2D new coordination polymers Co2(L1)2(1,10-Phenanthroline)2(DMF)0.5(H2O) (1), (H2L1 = Pyridine-3,5-dicarboxylic acid) Co(L1)(2,2-bipyridine) (2), and Co(L2)(2,2-bipyridine) (DMF) (3) (H [...] Read more.
Three 2D new coordination polymers Co2(L1)2(1,10-Phenanthroline)2(DMF)0.5(H2O) (1), (H2L1 = Pyridine-3,5-dicarboxylic acid) Co(L1)(2,2-bipyridine) (2), and Co(L2)(2,2-bipyridine) (DMF) (3) (H2L2 = Pyridine-3,4-dicarboxylic acid) were synthesized through a solvothermal reaction of cobalt nitrate and pyridine carboxylic acid ligand with the auxiliary ligand (1,10-Phenanthroline or 2,2-bipyridine). They were characterized by X-ray diffraction and elemental analysis, infrared spectroscopy, thermogravimetry analysis, and magnetism. Compounds 13 featured 2D hexagonal (6,3) networks which linked into 3D supramolecular architectures through π–π interaction. In addition, compounds 1 and 2 showed the antiferromagnetic exchange interactions, and the magnetic property of compound 3 exhibited ferromagnetic exchange interactions. Full article
(This article belongs to the Section Crystalline Materials)
Figures

Graphical abstract

Open AccessArticle An Overview of Strengths and Directionalities of Noncovalent Interactions: σ-Holes and π-Holes
Crystals 2019, 9(3), 165; https://doi.org/10.3390/cryst9030165
Received: 12 March 2019 / Revised: 14 March 2019 / Accepted: 16 March 2019 / Published: 21 March 2019
Viewed by 319 | PDF Full-text (3340 KB) | HTML Full-text | XML Full-text
Abstract
Quantum mechanics, through the Hellmann–Feynman theorem and the Schrödinger equation, show that noncovalent interactions are classically Coulombic in nature, which includes polarization as well as electrostatics. In the great majority of these interactions, the positive electrostatic potentials result from regions of low electronic [...] Read more.
Quantum mechanics, through the Hellmann–Feynman theorem and the Schrödinger equation, show that noncovalent interactions are classically Coulombic in nature, which includes polarization as well as electrostatics. In the great majority of these interactions, the positive electrostatic potentials result from regions of low electronic density. These regions are of two types, designated as σ-holes and π-holes. They differ in directionality; in general, σ-holes are along the extensions of covalent bonds to atoms (or occasionally between such extensions), while π-holes are perpendicular to planar portions of molecules. The magnitudes and locations of the most positive electrostatic potentials associated with σ-holes and π-holes are often approximate guides to the strengths and directions of interactions with negative sites but should be used cautiously for this purpose since polarization is not being taken into account. Since these maximum positive potentials may not be in the immediate proximities of atoms, interatomic close contacts are not always reliable indicators of noncovalent interactions. This is demonstrated for some heterocyclic rings and cyclic polyketones. We briefly mention some problems associated with using Periodic Table Groups to label interactions resulting from σ-holes and π-holes; for example, the labels do not distinguish between these two possibilities with differing directionalities. Full article
(This article belongs to the Special Issue σ- and π-Hole Interactions in Crystals)
Figures

Figure 1

Open AccessEditorial Crystal Growth of Multifunctional Borates and Related Materials
Crystals 2019, 9(3), 164; https://doi.org/10.3390/cryst9030164
Received: 15 March 2019 / Accepted: 19 March 2019 / Published: 21 March 2019
Viewed by 234 | PDF Full-text (156 KB) | HTML Full-text | XML Full-text
Abstract
Crystalline materials play an important role in modern physics and electronics [...] Full article
(This article belongs to the Special Issue Crystal Growth of Multifunctional Borates and Related Materials)
Open AccessReview Surface-Controlled Photocatalysis and Chemical Sensing of TiO2, α-Fe2O3, and Cu2O Nanocrystals
Crystals 2019, 9(3), 163; https://doi.org/10.3390/cryst9030163
Received: 2 March 2019 / Accepted: 7 March 2019 / Published: 20 March 2019
Viewed by 268 | PDF Full-text (12951 KB) | HTML Full-text | XML Full-text
Abstract
A relatively new approach to the design of photocatalytic and gas sensing materials is to use the shape-controlled nanocrystals with well-defined facets exposed to light or gas molecules. An abrupt increase in a number of papers on the synthesis and characterization of metal [...] Read more.
A relatively new approach to the design of photocatalytic and gas sensing materials is to use the shape-controlled nanocrystals with well-defined facets exposed to light or gas molecules. An abrupt increase in a number of papers on the synthesis and characterization of metal oxide semiconductors such as a TiO2, α-Fe2O3, Cu2O of low-dimensionality, applied to surface-controlled photocatalysis and gas sensing, has been recently observed. The aim of this paper is to review the work performed in this field of research. Here, the focus is on the mechanism and processes that affect the growth of nanocrystals, their morphological, electrical, and optical properties and finally their photocatalytic as well as gas sensing performance. Full article
(This article belongs to the Special Issue Semiconductor Nanomaterials Surfaces)
Figures

Figure 1

Open AccessReview Liquid-Crystalline Dispersions of Double-Stranded DNA
Crystals 2019, 9(3), 162; https://doi.org/10.3390/cryst9030162
Received: 13 February 2019 / Revised: 12 March 2019 / Accepted: 17 March 2019 / Published: 20 March 2019
Viewed by 247 | PDF Full-text (6705 KB) | HTML Full-text | XML Full-text
Abstract
In this review, we compare the circular dichroism (CD) spectra of liquid-crystalline dispersion (LCD) particles formed in PEG-containing aqueous-salt solutions with the purpose of determining the packing of ds DNA molecules in these particles. Depending on the osmotic pressure of the solution, the [...] Read more.
In this review, we compare the circular dichroism (CD) spectra of liquid-crystalline dispersion (LCD) particles formed in PEG-containing aqueous-salt solutions with the purpose of determining the packing of ds DNA molecules in these particles. Depending on the osmotic pressure of the solution, the phase exclusion of ds DNA molecules at room temperature results in the formation of LCD particles with the cholesteric or the hexagonal packing of molecules. The heating of dispersion particles with the hexagonal packing of the ds DNA molecules results in a new phase transition, accompanied by an appearance of a new optically active phase of ds DNA molecules. Our results are rationalized by way of a concept of orientationally ordered “quasinematic” layers formed by ds DNA molecules, with a parallel alignment in the hexagonal structure. These layers can adopt a twisted configuration with a temperature increase; and as a result of this process, a new, helicoidal structure of dispersion particle is formed (termed as the “re-entrant” cholesteric phase). To prove the cholesteric pattern of ds DNA molecules in this phase, the “liquid-like” state of the dispersion particles was transformed into its “rigid” counterpart. Full article
(This article belongs to the Special Issue Advances in Cholesteric Liquid Crystals)
Figures

Figure 1

Open AccessArticle Solvent-Mediated Polymorphic Transformation of Famoxadone from Form II to Form I in Several Mixed Solvent Systems
Crystals 2019, 9(3), 161; https://doi.org/10.3390/cryst9030161
Received: 2 March 2019 / Accepted: 13 March 2019 / Published: 20 March 2019
Viewed by 253 | PDF Full-text (3689 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
This paper discloses six polymorphs of famoxadone obtained from polymorph screening, which were characterized by XRPD, DSC, and SEM. A study of solvent-mediated polymorphic transformation (SMPT) of famoxadone from the metastable Form II to the stable Form I in several mixed solvent systems [...] Read more.
This paper discloses six polymorphs of famoxadone obtained from polymorph screening, which were characterized by XRPD, DSC, and SEM. A study of solvent-mediated polymorphic transformation (SMPT) of famoxadone from the metastable Form II to the stable Form I in several mixed solvent systems at the temperature of 30 °C was also conducted. The transformation process was monitored by Process Analytical Technologies. It was confirmed that the Form II to Form I polymorphic transformation is controlled by the Form I growth process. The transformation rate constants depended linearly on the solubility difference value between Form I and Form II. Furthermore, the hydrogen-bond-donation/acceptance ability and dipolar polarizability also had an effect on the rate of solvent-mediated polymorphic transformation. Full article
(This article belongs to the Special Issue Pharmaceutical Crystals)
Figures

Figure 1

Open AccessArticle Effect of Crowding Agent Polyethylene Glycol on Lyotropic Chromonic Liquid Crystal Phases of Disodium Cromoglycate
Crystals 2019, 9(3), 160; https://doi.org/10.3390/cryst9030160
Received: 20 February 2019 / Revised: 13 March 2019 / Accepted: 15 March 2019 / Published: 19 March 2019
Viewed by 334 | PDF Full-text (4602 KB) | HTML Full-text | XML Full-text
Abstract
Adding crowding agents such as polyethylene glycol (PEG) to lyotropic chromonic liquid crystals (LCLCs) formed by water dispersions of materials such as disodium cromoglicate (DSCG) leads to a phase separation of the isotropic phase and the ordered phase. This behavior resembles nanoscale condensation [...] Read more.
Adding crowding agents such as polyethylene glycol (PEG) to lyotropic chromonic liquid crystals (LCLCs) formed by water dispersions of materials such as disodium cromoglicate (DSCG) leads to a phase separation of the isotropic phase and the ordered phase. This behavior resembles nanoscale condensation of DNAs but occurs at the microscale. The structure of condensed chromonic regions in crowded dispersions is not yet fully understood, in particular, it is not clear whether the condensed domains are in the nematic (N) or the columnar (C) state. In this study, we report on small angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) measurements of mixtures of aqueous solutions of DSCG with PEG and compare results to measurements of aqueous solutions of pure DSCG. X-ray measurements demonstrate that addition of PEG to DSCG in the N phase triggers appearance of the C phase that coexists with the isotropic (I) phase. Within the coexisting region, the lateral distance between the columns of the chromonic aggregates decreases as the temperature is increased. Full article
(This article belongs to the Special Issue New Trends in Lyotropic Liquid Crystals)
Figures

Figure 1

Open AccessArticle A Preview of a Construction of a Crystal Lattice Based on Intermolecular Interactions
Crystals 2019, 9(3), 159; https://doi.org/10.3390/cryst9030159
Received: 25 February 2019 / Revised: 13 March 2019 / Accepted: 14 March 2019 / Published: 19 March 2019
Viewed by 329 | PDF Full-text (5701 KB) | HTML Full-text | XML Full-text
Abstract
A general procedure of crystal packing reconstruction using a certain number of intermolecular interactions is introduced and demonstrated on the crystal structure of l-histidine·HCl·H2O. Geometric restrictions based on intermolecular interactions are used for formation of a molecular pair as a [...] Read more.
A general procedure of crystal packing reconstruction using a certain number of intermolecular interactions is introduced and demonstrated on the crystal structure of l-histidine·HCl·H2O. Geometric restrictions based on intermolecular interactions are used for formation of a molecular pair as a basic repetitive motif of the crystal packing. The geometric restrictions were applied gradually within a supervised procedure, narrowing the scope of possible arrangement of two adjacent molecules. Subsequently, a pair of histidine molecules was used for construction of a molecular chain. The chain formed contained translation information on histidine molecules in one dimension, which coincided with one of the cell parameters. Furthermore, the periodicity in the second and third dimensions can be accomplished by chain assembly into sheets (2D), and sheets can be arranged into the final 3D structure. For this purpose, the rest of the available intermolecular interactions could be used to control the mutual assembly of molecular chains and sheets. Complete molecular packing would enable derivation of standard crystallographic parameters that can be used for verification of the structural model obtained. However, the procedure described for construction of the whole 3D structure from molecular chains was not attempted, and is only briefly outlined here. The procedure described can be employed especially when standard crystallographic parameters are not available and traditional methods based on X-ray diffraction fail. Full article
(This article belongs to the Special Issue NMR Crystallography)
Figures

Graphical abstract

Open AccessReview Experimental Conditions for the Stabilization of the Lyotropic Biaxial Nematic Mesophase
Crystals 2019, 9(3), 158; https://doi.org/10.3390/cryst9030158
Received: 1 February 2019 / Revised: 4 March 2019 / Accepted: 15 March 2019 / Published: 19 March 2019
Viewed by 293 | PDF Full-text (3743 KB) | HTML Full-text | XML Full-text
Abstract
Nematic phases are some of the most common phases among the lyotropic liquid crystalline structures. They have been widely investigated during last decades. In early studies, two uniaxial nematic phases (discotic, ND, and calamitic, NC) were identified. After the [...] Read more.
Nematic phases are some of the most common phases among the lyotropic liquid crystalline structures. They have been widely investigated during last decades. In early studies, two uniaxial nematic phases (discotic, ND, and calamitic, NC) were identified. After the discovery of the third one, named biaxial nematic phase (NB) in 1980, however, some controversies in the stability of biaxial nematic phases began and still continue in the literature. From the theoretical point of view, the existence of a biaxial nematic phase is well established. This review aims to bring information about the historical development of those phases considering the early studies and then summarize the recent studies on how to stabilize different nematic phases from the experimental conditions, especially, choosing the suitable constituents of lyotropic mixtures. Full article
(This article belongs to the Special Issue New Trends in Lyotropic Liquid Crystals)
Figures

Figure 1

Open AccessCommunication Hybrid Biomimetic Materials from Silica/Carbonate Biomorphs
Crystals 2019, 9(3), 157; https://doi.org/10.3390/cryst9030157
Received: 28 February 2019 / Revised: 13 March 2019 / Accepted: 14 March 2019 / Published: 18 March 2019
Viewed by 327 | PDF Full-text (2170 KB) | HTML Full-text | XML Full-text
Abstract
The formation of a polymer protection layer around fragile mineral architectures ensures that structures stay intact even after treatments that would normally destroy them going along with a total loss of textural information. Here we present a strategy to preserve the shape of [...] Read more.
The formation of a polymer protection layer around fragile mineral architectures ensures that structures stay intact even after treatments that would normally destroy them going along with a total loss of textural information. Here we present a strategy to preserve the shape of silica-carbonate biomorphs with polymers. This method converts non-hybrid inorganic-inorganic composite materials such a silica/carbonate biomorphs into hybrid organic/carbonate composite materials similar to biominerals. Full article
(This article belongs to the Special Issue Biological Crystallization)
Figures

Graphical abstract

Open AccessArticle Two-Layer Erbium-Doped Air-Core Circular Photonic Crystal Fiber Amplifier for Orbital Angular Momentum Mode Division Multiplexing System
Crystals 2019, 9(3), 156; https://doi.org/10.3390/cryst9030156
Received: 25 February 2019 / Revised: 11 March 2019 / Accepted: 12 March 2019 / Published: 15 March 2019
Viewed by 259 | PDF Full-text (2143 KB) | HTML Full-text | XML Full-text
Abstract
Orbital angular momentum (OAM) mode-division multiplexing (MDM) has recently been under intense investigations as a new way to increase the capacity of fiber communication. In this paper, a two-layer Erbium-doped fiber amplifier (EDFA) for an OAM multiplexing system is proposed. The amplifier is [...] Read more.
Orbital angular momentum (OAM) mode-division multiplexing (MDM) has recently been under intense investigations as a new way to increase the capacity of fiber communication. In this paper, a two-layer Erbium-doped fiber amplifier (EDFA) for an OAM multiplexing system is proposed. The amplifier is based on the circular photonic crystal fiber (C-PCF), which can maintain a stable transmission for 14 OAM modes by a large index difference between the fiber core and the cladding. Further, the two-layer doped region can balance the amplification performance of different modes. The relationship between the performance and the parameters of the amplifier is analyzed numerically to optimize the amplifier design. The optimized amplifier can amplify 18 modes (14 OAM modes) simultaneously over the C-band with a differential mode gain (DMG) lower than 0.1 dB while keeping the modal gain over 23 dB and noise figure below 4 dB. Finally, the fabrication tolerance and feasibility are discussed. The result shows a relatively large fabrication tolerance in the OAM EDFA parameters. Full article
(This article belongs to the Special Issue Sonic and Photonic Crystals)
Figures

Figure 1

Open AccessArticle Growth of Ga2O3 Nanowires via Cu-As-Ga Ternary Phase Diagram
Crystals 2019, 9(3), 155; https://doi.org/10.3390/cryst9030155
Received: 13 February 2019 / Revised: 11 March 2019 / Accepted: 12 March 2019 / Published: 15 March 2019
Viewed by 282 | PDF Full-text (4068 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Currently, it is challenging to develop new catalysts for semiconductor nanowires (NWs) growth in a complementary-metal-oxide-semiconductor (CMOS) compatible manner via a vapor-liquid-solid (VLS) mechanism. In this study, chemically synthesized Cu2O nano cubes are adopted as the catalyst for single crystalline β-Ga [...] Read more.
Currently, it is challenging to develop new catalysts for semiconductor nanowires (NWs) growth in a complementary-metal-oxide-semiconductor (CMOS) compatible manner via a vapor-liquid-solid (VLS) mechanism. In this study, chemically synthesized Cu2O nano cubes are adopted as the catalyst for single crystalline β-Ga2O3 NWs growth in chemical vapor deposition. The growth temperature is optimized to be 750 to 800 °C. The NW diameter is controlled by tuning the sizes of Cu2O cubes in the 20 to 100 nm range with a bandgap of ~4.85 eV as measured by ultraviolet-visible absorption spectroscopy. More importantly, the catalyst tip is found to be Cu5As2, which is distinguished from those Au-catalyzed Au-Ga alloys. After a comprehensive phase diagram investigation, the β-Ga2O3 NWs are proposed to be grown by the ternary phase of Cu-As-Ga diffusing Ga into the growth frontier of the NW, where Ga react with residual oxygen to form the NWs. Afterward, Ga diminishes after growth since Ga would be the smallest component in the ternary alloy. All these results show the importance of the catalyst choice for CMOS compatible NW growth and also the potency of the ternary phase catalyst growth mode in other semiconductor NWs synthesis. Full article
(This article belongs to the Special Issue Structural and Optical Properties of Nanostructured Metal Oxides)
Figures

Figure 1

Open AccessArticle Representative Stress Correlation of Global Scratch Quantities at Scratch Testing: Experimental Verification
Crystals 2019, 9(3), 154; https://doi.org/10.3390/cryst9030154
Received: 28 February 2019 / Revised: 11 March 2019 / Accepted: 12 March 2019 / Published: 14 March 2019
Viewed by 253 | PDF Full-text (1647 KB) | HTML Full-text | XML Full-text
Abstract
Evaluation and correlation of global quantities, i.e., normal and tangential hardness, at scratch testing in the context of a representative stress description was investigated. In particular, verification based on experimental results is at issue. It has been shown previously that within the framework [...] Read more.
Evaluation and correlation of global quantities, i.e., normal and tangential hardness, at scratch testing in the context of a representative stress description was investigated. In particular, verification based on experimental results is at issue. It has been shown previously that within the framework of classical von Mises elasto-plasticity and quasi-static conditions, correlation can be achieved by using a combination of stresses at different levels of plastic strains to define representative quantities at scratching, accounting for the difference in mechanical behavior at elasto-plastic and rigid plastic scratching. However, verification from experimental results is required, which has been attempted in this study. Predictions based on previous theoretical results were compared with experimental findings for polymeric materials, as well as for different metals. Good agreement was found between the two sets of results, particularly so for the case of polymers modelled by von Mises elasto-plasticity. Accordingly, these results are of direct practical, accurate, and novel relevance for semi-crystalline polymers where viscoelastic effects are negligible. Full article
(This article belongs to the Section Crystalline Materials)
Figures

Figure 1

Open AccessArticle Luminescent Layered Double Hydroxides Intercalated with an Anionic Photosensitizer via the Memory Effect
Crystals 2019, 9(3), 153; https://doi.org/10.3390/cryst9030153
Received: 12 February 2019 / Revised: 8 March 2019 / Accepted: 9 March 2019 / Published: 14 March 2019
Viewed by 278 | PDF Full-text (1963 KB) | HTML Full-text | XML Full-text
Abstract
Layered double hydroxides (LDHs) containing Eu3+ activators were synthesized by coprecipitation of Zn2+, Al3+, and Eu3+ in alkaline NO3-rich aqueous solution. Upon calcination, these materials transform into a crystalline ZnO solid solution containing Al [...] Read more.
Layered double hydroxides (LDHs) containing Eu3+ activators were synthesized by coprecipitation of Zn2+, Al3+, and Eu3+ in alkaline NO3-rich aqueous solution. Upon calcination, these materials transform into a crystalline ZnO solid solution containing Al and Eu. For suitably low calcination temperatures, this phase can be restored to LDH by rehydration in water, a feature known as the memory effect. During rehydration of an LDH, new anionic species can be intercalated and functionalized, obtaining desired physicochemical properties. This work explores the memory effect as a route to produce luminescent LDHs intercalated with 1,3,5-benzenetricarboxylic acid (BTC), a known anionic photosensitizer for Eu3+. Time-dependent hydration of calcined LDHs in a BTC-rich aqueous solution resulted in the recovery of the lamellar phase and in the intercalation with BTC. The interaction of this photosensitizer with Eu3+ in the recovered hydroxide layers gave rise to efficient energy transfer from the BTC antennae to the Eu3+ ions, providing a useful tool to monitor the rehydration process of the calcined LDHs. Full article
(This article belongs to the Special Issue Layered Double Hydroxides)
Figures

Figure 1

Open AccessEditorial Microstructures and Properties of Martensitic Materials
Crystals 2019, 9(3), 152; https://doi.org/10.3390/cryst9030152
Received: 4 March 2019 / Accepted: 12 March 2019 / Published: 14 March 2019
Viewed by 238 | PDF Full-text (156 KB) | HTML Full-text | XML Full-text
Abstract
Martensite, initially named in honor of Adolph Martens and his pioneering work in metallography and microstructures at the end of the 19th century, has now a far broader meaning than previously used [...] Full article
(This article belongs to the Special Issue Microstructures and Properties of Martensitic Materials)
Open AccessArticle Impact of Delay Time before Annealing MAI-PbI2-DMSO Intermediate Phase on Perovskite Film Quality and Photo-Physical Properties
Crystals 2019, 9(3), 151; https://doi.org/10.3390/cryst9030151
Received: 1 March 2019 / Accepted: 8 March 2019 / Published: 14 March 2019
Viewed by 325 | PDF Full-text (2330 KB) | HTML Full-text | XML Full-text
Abstract
High-performance perovskite solar cells are strongly dependent on the quality of the perovskite layer. Two-step sequential deposition of CH3NH3PbI3 (MAPbI3) films is widely used to fabricate perovskite solar cells and many factors influence the quality of [...] Read more.
High-performance perovskite solar cells are strongly dependent on the quality of the perovskite layer. Two-step sequential deposition of CH3NH3PbI3 (MAPbI3) films is widely used to fabricate perovskite solar cells and many factors influence the quality of perovskite films, such as the delay time before annealing the MAI-PbI2-DMSO intermediate phase, which would impact the morphology and photo-physical properties of perovskite thin films. Here, the experimental research indicates that the impact of the delay time before annealing the MAI-PbI2-DMSO intermediate phase on the quality, crystallinity, and photo-physical properties of perovskite film is crucial. During the delay process, the delay time before annealing the MAI-PbI2-DMSO intermediate phase plays an important role in the nucleation process of perovskite grains inside the intermediate phase. With the extension of the delay time before annealing, the quality of the perovskite film deteriorates, thus the photo-physical properties change. We found that after the localized liquid–liquid diffusion of MAI and PbI2, with the extension of the delay time before annealing the MAI-PbI2-DMSO intermediate phase, the nucleation number of the perovskite grains increases and the grain size becomes smaller. Therefore, with the extension of the delay time before annealing, the device performance deteriorates. Full article
(This article belongs to the Special Issue Advances in Thin Film Solar Cells)
Figures

Figure 1

Crystals EISSN 2073-4352 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top