Open AccessArticle
Colloidal Nanocrystalline Semiconductor Materials as Photocatalysts for Environmental Protection of Architectural Stone
Crystals 2017, 7(1), 30; doi:10.3390/cryst7010030 (registering DOI) -
Abstract
Rod-shaped TiO2 nanocrystals (TiO2 NRs), capped by oleic acid molecules (OLEA), were synthesized with controlled size, shape and surface chemistry by using colloidal routes. They were investigated for application as coating materials for preserving architectural stone of monumental and archaeological interest,
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Rod-shaped TiO2 nanocrystals (TiO2 NRs), capped by oleic acid molecules (OLEA), were synthesized with controlled size, shape and surface chemistry by using colloidal routes. They were investigated for application as coating materials for preserving architectural stone of monumental and archaeological interest, in consideration of their self-cleaning and protection properties. For this purpose, two different deposition techniques, namely casting and dipping, were tested for the application of a nanocrystal dispersion on a defined stone type, as a relevant example of porous calcarenites, namely the Pietra Leccese, a building stone widely used in monuments and buildings of cultural and historic interest of the Apulia region (Italy). The physical properties of the stone surface were investigated before and after the treatment with the prepared nanostructured materials. In particular, colour, wettability, water transfer properties and stability of the coating were monitored as a function of time and of the application method. The self-cleaning properties of the TiO2 NRs coated surfaces were tested under simulated and real solar irradiation. The obtained results were discussed in the light of the specific surface chemistry and morphology of TiO2 NRs, demonstrating the effectiveness of TiO2 NRs as an active component in formulations for stone protection. Full article
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Open AccessArticle
Synthesis, Crystal Structure, Luminescence and Magnetism of Three Novel Coordination Polymers Based on Flexible Multicarboxylate Zwitterionic Ligand
Crystals 2017, 7(1), 32; doi:10.3390/cryst7010032 (registering DOI) -
Abstract
Three novel zwitterionic coordination polymers, namely, {[Zn(HCbdcp)2]·H2O} (1), {[Mn(Cbdcp)]·3H2O} (2) and {[Cu2(Cbdcp)(HCbdcp)Cl·H2O]·2H2O} (3), Cbdcp = 3,5-dicarboxy-1-(4-carboxybenzyl)pyridin-1-ium, have been prepared by a hydrothermal method and characterized
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Three novel zwitterionic coordination polymers, namely, {[Zn(HCbdcp)2]·H2O} (1), {[Mn(Cbdcp)]·3H2O} (2) and {[Cu2(Cbdcp)(HCbdcp)Cl·H2O]·2H2O} (3), Cbdcp = 3,5-dicarboxy-1-(4-carboxybenzyl)pyridin-1-ium, have been prepared by a hydrothermal method and characterized by X-ray single crystal diffraction analysis, powder X-ray diffraction analysis, IR spectroscopy, and thermogravimetric analysis. With the changing of metal centers, these complexes show distinct structures: a mononuclear 2D 44-sql network for 1, a 3D 6,6-connected-type topology for 2 and a novel dinuclear 2D layer for 3. These diverse architectures prove that coordination geometry of metal ions, coordination modes of carboxylate groups and the rotationally flexible CH2 linker played significant roles in the construction of CPs; moreover, they also indicated that H3CbdcpCl is an ideal organic candidate for the building of novel structures. The solid-state luminescent properties of complexes 13 were investigated, respectively. In addition, the magnetic properties of 2 and 3 were studied and both of them exhibit antiferromagnetic behaviors. Full article
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Open AccessArticle
Ionic Liquid Crystals Modifier for Selective Determination of Terazosin Antihypertensive Drug in Presence of Common Interference Compounds
Crystals 2017, 7(1), 27; doi:10.3390/cryst7010027 (registering DOI) -
Abstract
Electrochemical sensor was fabricated based on carbon paste electrode modified with an ionic liquid crystal ILC (2-chloro-1,3-dimethyl-imidazolidinium hexafluorophosphate) in presence of sodium dodecyl sulfate for the selective electrochemical determination of Terazosin (TZ) in presence of common interference compounds. The electrode performance was compared
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Electrochemical sensor was fabricated based on carbon paste electrode modified with an ionic liquid crystal ILC (2-chloro-1,3-dimethyl-imidazolidinium hexafluorophosphate) in presence of sodium dodecyl sulfate for the selective electrochemical determination of Terazosin (TZ) in presence of common interference compounds. The electrode performance was compared in presence of other ionic liquids ILs (1-Butyl-4-methyl pyridinium tetrafluoroborate) and (1-n-Hexyl-3-methyl imidazolium tetrafluoroborate). Ultrasensitive determination of Terazosin HCl at the ILC modified electrode in the linear dynamic ranges of 0.002 to 0.09 μmol·L−1 and 0.2 to 30 μmol·L−1 with correlation coefficients 0.996 and 0.995 and LODs 1.69 × 10−11 mol·L−1 and 6.43 × 10−9 mol·L−1, respectively, were obtained. Selective determination of TZ in presence of uric acid and ascorbic acid and simultaneous determination of binary mixtures of TZ/dopamine, TZ/paracetamol and TZ/Morphine were also determined successfully using the modified sensor. Full article
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Open AccessReview
Dirac Landau Level Spectroscopy in Pb1−xSnxSe and Pb1−xSnxTe across the Topological Phase Transition: A Review
Crystals 2017, 7(1), 29; doi:10.3390/cryst7010029 (registering DOI) -
Abstract
Topological crystalline insulators (TCIs) are topological materials that have Dirac surface states occurring at crystalline symmetric points in the Brillouin zone. This topological state has been experimentally shown to occur in the lead–tin salts Pb1−xSnxSe and Pb1−xSn
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Topological crystalline insulators (TCIs) are topological materials that have Dirac surface states occurring at crystalline symmetric points in the Brillouin zone. This topological state has been experimentally shown to occur in the lead–tin salts Pb1−xSnxSe and Pb1−xSnxTe. More recent works also took interest in studying the topological phase transition from trivial to non-trivial topology that occurs in such materials as a function of increasing Sn content. A peculiar property of these materials is the fact that their bulk bands disperse following a massive Dirac dispersion that is linear at low energies above the energy gap. This makes Pb1−xSnxSe and Pb1−xSnxTe ideal platforms to simultaneously study 3D and 2D Dirac physics. In this review, we will go over infrared magneto-optical studies of the Landau level dispersion of Pb1−xSnxSe and Pb1−xSnxTe for both the bulk and surface bands and summarize work that has been done on this matter. We will review recent work on probing the topological phase transition in TCI. We will finally present our views on prospects and open questions that have yet to be addressed in magneto-optical spectroscopy studies on Pb1-xSnxSe and Pb1−xSnxTe. Full article
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Open AccessArticle
Influence of Alkyl Trimethyl Ammonium Bromides on Hydrothermal Formation of α-CaSO4·0.5H2O Whiskers with High Aspect Ratios
Crystals 2017, 7(1), 28; doi:10.3390/cryst7010028 -
Abstract
In this paper, the influence of alkyl trimethyl ammonium bromides (CnH2n+1(CH3)3NBr, n = 10, 12, 14, 16, 18, abbreviated as ATAB) on the formation of alpha calcium sulfate hemihydrate (α-CaSO4·0.5H2O) whiskers
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In this paper, the influence of alkyl trimethyl ammonium bromides (CnH2n+1(CH3)3NBr, n = 10, 12, 14, 16, 18, abbreviated as ATAB) on the formation of alpha calcium sulfate hemihydrate (α-CaSO4·0.5H2O) whiskers under a hydrothermal condition (135 °C, 3.0 h) was analyzed. Specifically, it focuses on cetyl trimethyl ammonium bromide (C16H33(CH3)3NBr, abbreviated as CTAB). The rising CTAB concentration from 0 to 9.2 × 10−4 mol·L−1 led to the increase of the average aspect ratio of α-CaSO4·0.5H2O whiskers from 80 to 430, since the selective adsorption of CTAB on the negatively-charged side facets of the whiskers inhibited the growth of the whiskers along the direction normal to the lateral facets. The further increase of CTAB concentration above the critical micelle concentration (abbreviated as CMC) showed little effect on the morphology of α-CaSO4·0.5H2O whiskers, considering that CTAB tended to form micelles instead of being adsorbed on the whisker surfaces. Similar phenomena were observed in other ATABs (n = 10, 12, 14, 18). Full article
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Open AccessArticle
The New Method of XRD Measurement of the Degree of Disorder for Anode Coke Material
Crystals 2017, 7(1), 5; doi:10.3390/cryst7010005 -
Abstract
Quantitative analysis by X-ray powder diffraction of two cokes (pitch coke and petroleum coke) shows that their crystal structure changed with increasing temperature. The crystal data processing of the crystallization degree of disorder is used with further improvement of the proposed microcrystalline-stacking fault
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Quantitative analysis by X-ray powder diffraction of two cokes (pitch coke and petroleum coke) shows that their crystal structure changed with increasing temperature. The crystal data processing of the crystallization degree of disorder is used with further improvement of the proposed microcrystalline-stacking fault calculation method. With this improvement it is now possible to obtain the degree of stacking disorder of two cokes applied as anode materials at different graphitization temperatures. Raman spectroscopy verified the accuracy of this method, which is more reliable than the crystal structure refinement using the d002 method. This paper provides the theoretical analysis and interpretation of the relationship between the microstructure model of the material and quantitative data, discharge capacity, and the first charge-discharge efficiency. Full article
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Open AccessArticle
Numerical Modelling of the Czochralski Growth of β-Ga2O3
Crystals 2017, 7(1), 26; doi:10.3390/cryst7010026 -
Abstract
Our numerical modelling of the Czochralski growth of single crystalline β-Ga2O3 crystals (monoclinic symmetry) starts at the 2D heat transport analysis within the crystal growth furnace, proceeds with the 3D heat transport and fluid flow analysis in the crystal-melt-crucible
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Our numerical modelling of the Czochralski growth of single crystalline β-Ga2O3 crystals (monoclinic symmetry) starts at the 2D heat transport analysis within the crystal growth furnace, proceeds with the 3D heat transport and fluid flow analysis in the crystal-melt-crucible arrangement and targets the 3D thermal stress analysis within the β-Ga2O3 crystal. In order to perform the stress analysis, we measured the thermal expansion coefficients and the elastic stiffness coefficients in two samples of a β-Ga2O3 crystal grown at IKZ. Additionally, we analyse published data of β-Ga2O3 material properties and use data from literature for comparative calculations. The computations were performed by the software packages CrysMAS, CGsim, Ansys-cfx and comsol Multiphysics. By the hand of two different thermal expansion data sets and two different crystal orientations, we analyse the elastic stresses in terms of the von-Mises stress. Full article
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Open AccessArticle
Four Thermochromic o-Hydroxy Schiff Bases of α-Aminodiphenylmethane: Solution and Solid State Study
Crystals 2017, 7(1), 25; doi:10.3390/cryst7010025 -
Abstract
More than a hundred years after the first studies of the photo- and thermochromism of o-hydroxy Schiff bases (imines), it is still an intriguing topic that fascinates several research groups around the world. The reasons for such behavior are still under investigation,
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More than a hundred years after the first studies of the photo- and thermochromism of o-hydroxy Schiff bases (imines), it is still an intriguing topic that fascinates several research groups around the world. The reasons for such behavior are still under investigation, and this work is a part of it. We report the solution-based and mechanochemical synthesis of four o-hydroxy imines derived from α-aminodiphenylmethane. The thermochromic properties were studied for the single crystal and polycrystalline samples of the imines. The supramolecular impact on the keto-enol tautomerism in the solid state was studied using SCXRD and NMR, while NMR spectroscopy was used for the solution state. All four imines are thermochromic, although the color changes of the single crystals are not as strong as of the polycrystalline samples. One of the imines shows negative thermochromism, and that one is in keto-amine tautomeric form, both in the solid state as in solution. Full article
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Open AccessArticle
Potassium Disorder in the Defect Pyrochlore KSbTeO6: A Neutron Diffraction Study
Crystals 2017, 7(1), 24; doi:10.3390/cryst7010024 -
Abstract
KSbTeO6 defect pyrochlore has been prepared from K2C2O4, Sb2O3, and 15% excess TeO2 by solid-state reaction at 850 °C. Direct methods implemented in the software EXPO2013 allowed establishing the basic structural
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KSbTeO6 defect pyrochlore has been prepared from K2C2O4, Sb2O3, and 15% excess TeO2 by solid-state reaction at 850 °C. Direct methods implemented in the software EXPO2013 allowed establishing the basic structural framework. This was followed by a combined Rietveld refinement from X-ray powder diffraction (XRD) and neutron powder diffraction (NPD) data, which unveiled additional structural features. KSbTeO6 is cubic, a = 10.1226(7) Å, space group Fd3¯m, Z = 8 and it is made of a mainly covalent framework of corner-sharing (Sb,Te)O6 octahedra, with weakly bonded K+ ions located within large cages. The large K-O distances, 3.05(3)–3.07(3) Å, and quite large anisotropic atomic displacement parameters account for the easiness of K+ exchange for other cations of technological importance. Full article
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Open AccessArticle
Synthesis, Crystal Structure, DFT Study of m-Methoxy-N′-(3-Methoxybenzoyl)-N-Phenylbenzohydrazide
Crystals 2017, 7(1), 19; doi:10.3390/cryst7010019 -
Abstract
The crystal structure of m-methoxy-N′-(m-anisoyl)-N-phenylbenzohydrazide has been determined by means of single-crystal X-ray diffraction. The title compound crystallizes in the monoclinic space group P 21/c with unit cell parameters: a = 8.7338(1), b = 24.5602(3), c
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The crystal structure of m-methoxy-N′-(m-anisoyl)-N-phenylbenzohydrazide has been determined by means of single-crystal X-ray diffraction. The title compound crystallizes in the monoclinic space group P 21/c with unit cell parameters: a = 8.7338(1), b = 24.5602(3), c = 9.6929(1) Å, β = 113.186(2)°, V = 1911.23(4) Å3, Z = 4. The dihedral angles between the mean plane of the central benzene ring and two terminal aromatic rings are 72.44(4)° and 89.90(4)°, respectively. The two methoxyphenyl rings are orthogonal with a dihedral angle of 89.74(4)°. The crystal packing is stabilized by a combination of N–HO intermolecular hydrogen bonding and weak intermolecular C–HO interactions. The X-ray structure was compared with the optimized counterpart calculated by the B3LYP/6-311G basis set and the results showed that the optimized geometry can reproduce the crystal structure parameters well. Full article
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Open AccessArticle
Synthesizing Iron Oxide Nanostructures: The Polyethylenenemine (PEI) Role
Crystals 2017, 7(1), 22; doi:10.3390/cryst7010022 -
Abstract
Controlled synthesis of anisotropic iron oxide nanoparticles is a challenge in the field of nanomaterial research that requires an extreme attention to detail. In particular, following up a previous work showcasing the synthesis of magnetite nanorods (NRs) using a two-step approach that made
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Controlled synthesis of anisotropic iron oxide nanoparticles is a challenge in the field of nanomaterial research that requires an extreme attention to detail. In particular, following up a previous work showcasing the synthesis of magnetite nanorods (NRs) using a two-step approach that made use of polyethylenenemine (PEI) as a capping ligand to synthesize intermediate β-FeOOH NRs, we studied the effect and influence of the capping ligand on the formation of β-FeOOH NRs. By comparing the results reported in the literature with those we obtained from syntheses performed (1) in the absence of PEI or (2) by using PEIs with different molecular weight, we showed how the choice of different PEIs determines the aspect ratio and the structural stability of the β-FeOOH NRs and how this affects the final products. For this purpose, a combination of XRD, HRTEM, and direct current superconducting quantum interference device (DC SQUID) magnetometry was used to identify the phases formed in the final products and study their morphostructural features and related magnetic behavior. Full article
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Open AccessEditorial
Crystal Indentation Hardness
Crystals 2017, 7(1), 21; doi:10.3390/cryst7010021 -
Abstract
There is expanded interest in the long-standing subject of the hardness properties of materials. A major part of such interest is due to the advent of nanoindentation hardness testing systems which have made available orders of magnitude increases in load and displacement measuring
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There is expanded interest in the long-standing subject of the hardness properties of materials. A major part of such interest is due to the advent of nanoindentation hardness testing systems which have made available orders of magnitude increases in load and displacement measuring capabilities achieved in a continuously recorded test procedure. The new results have been smoothly merged with other advances in conventional hardness testing and with parallel developments in improved model descriptions of both elastic contact mechanics and dislocation mechanisms operative in the understanding of crystal plasticity and fracturing behaviors. No crystal is either too soft or too hard to prevent the determination of its elastic, plastic and cracking properties under a suitable probing indenter. A sampling of the wealth of measurements and reported analyses associated with the topic on a wide variety of materials are presented in the current Special Issue. Full article
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Open AccessEditorial
Acknowledgement to Reviewers of Crystals in 2016
Crystals 2017, 7(1), 20; doi:10.3390/cryst7010020 -
Abstract The editors of Crystals would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2016.[...] Full article
Open AccessArticle
Role of Internal Radiation in Oxide Crystal Growth by Heat Exchanger Method
Crystals 2017, 7(1), 18; doi:10.3390/cryst7010018 -
Abstract
Internal radiation was investigated using the finite volume method for the heat exchanger method (HEM) growth of oxide crystals. Special attention was devoted to the temperature and thermal stress distributions in the bottom region of the grown crystal at the end of the
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Internal radiation was investigated using the finite volume method for the heat exchanger method (HEM) growth of oxide crystals. Special attention was devoted to the temperature and thermal stress distributions in the bottom region of the grown crystal at the end of the solidification process. The numerical results show that internal radiation strongly strengthens heat transport through the crystal. However, it causes isotherms to intensively concentrate in the crystal bottom region, leading to a significant increase in the temperature gradient and thermal stress in this region. Then, the effect of absorption coefficient on this phenomenon was numerically investigated. It was found that the radiation heat transfer rate at the bottom surface of the crystal monotonically decreases as the absorption coefficient is increased, while the conduction heat transfer rate first increases and then decreases as the absorption coefficient is increased, under the interaction between internal radiation and heat conduction. The variations of the maximum temperature gradient and thermal stress in the crystal bottom show the same tendency as the conduction heat transfer rate. This study indicates that the role of internal radiation on the heat transfer and thermal stress in oxide crystal by HEM process shows some differences from that by Czochralski and Kyropoulos processes. Full article
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Open AccessArticle
New Acetylenic Amine Derivatives of 5,8-Quinolinediones: Synthesis, Crystal Structure and Antiproliferative Activity
Crystals 2017, 7(1), 15; doi:10.3390/cryst7010015 -
Abstract
Acetylenic amine derivatives of the 5,8-quinolinedione were synthesized and characterized by the 1H and 13C NMR, IR spectroscopy and MS spectra. Additionally, the 6- and 7-substituted allylamine-5,8-quinolinediones were synthesized for comparison purposes. The crystal structure was determined for the 6-chloro-7-propargylamine-5,8-quinolinedione and
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Acetylenic amine derivatives of the 5,8-quinolinedione were synthesized and characterized by the 1H and 13C NMR, IR spectroscopy and MS spectra. Additionally, the 6- and 7-substituted allylamine-5,8-quinolinediones were synthesized for comparison purposes. The crystal structure was determined for the 6-chloro-7-propargylamine-5,8-quinolinedione and 7-chloro-6-propargylamine-5,8-quinolinedione. Additionally, the IR spectral analysis supplemented by the density functional theory (DFT) calculations were carried out. It was found that different positions of the propargylamine side chain had a distinct influence on crystal structure, formation of H-bonds and the carbonyl stretching IR bands. Correlation between the frequency separation Δν of the carbonyl IR bands and the position of the 6- and 7-substituents was found. The 7-substituted derivatives exhibited a higher frequency separation Δν. The observed correlation could provide an opportunity to use the IR spectroscopy to study substitution reactions. Cytotoxic activities against three human cancer cell lines for the 5,8-quinolinedione derivatives with different amine substituents, i.e., propargylamine, N-methylpropargylamine, 1,1-dimethylpropargylamine, allylamine and propylamine were also analysed with respect to their molecular structure. Full article
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Open AccessArticle
Structural and Gas Retention Changes Induced by Ozonization of Cobalt(II) and Manganese(II) Hexacyanocobaltates(III)
Crystals 2017, 7(1), 16; doi:10.3390/cryst7010016 -
Abstract
Transition metal hexacyanocobaltates are porous materials with open metal sites and a wide variety of pores. In this work, manganese(II) and cobalt(II) hexacyanocobaltates(III) have been selected to explore the interactions between the open metal sites located in their pores and the guest molecules:
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Transition metal hexacyanocobaltates are porous materials with open metal sites and a wide variety of pores. In this work, manganese(II) and cobalt(II) hexacyanocobaltates(III) have been selected to explore the interactions between the open metal sites located in their pores and the guest molecules: hydrogen, carbon dioxide, water and methanol. An experimental setup was designed and implemented to conduct post-synthesis modification of the solids with ozone. Samples were dehydrated, ozonized and saturated with methanol in situ. Ozone molecules acted on the open metal sites changing their oxidation state, causing a contraction of the unit cell and inducing a stronger interaction of the molecules of water and methanol with the lattice. This strengthening prevented the lattice from being evacuated without compromising its framework stability. The decomposition temperature decreased in all ozonized samples as a consequence of the elongation and weakening of the cobalt-carbon bond. Active infrared and Raman bands were used to monitor the interaction between the open metal sites at the framework surface and the guest molecules. The cell contraction and the presence of residual methanol molecules in the porosity reduced the hydrogen and carbon dioxide retention capacity of the samples. Full article
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Open AccessArticle
Infrared Investigations of the Neutral-Ionic Phase Transition in TTF-CA and Its Dynamics
Crystals 2017, 7(1), 17; doi:10.3390/cryst7010017 -
Abstract
The neutral-ionic phase transition in TTF-CA was investigated by steady-state and time-resolved infrared spectroscopy. We describe the growth of high-quality single crystals and their characterization. Extended theoretical calculations were performed in order to obtain the band structure, the molecular vibrational modes and the
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The neutral-ionic phase transition in TTF-CA was investigated by steady-state and time-resolved infrared spectroscopy. We describe the growth of high-quality single crystals and their characterization. Extended theoretical calculations were performed in order to obtain the band structure, the molecular vibrational modes and the optical spectra along all crystallographic axes. The theoretical results are compared to polarization-dependent infrared reflection experiments. The temperature-dependent optical conductivity is discussed in detail. We study the photo-induced phase transition in the vicinity of thermally-induced neutral-ionic transition. The observed temporal dynamics of the photo-induced states is attributed to the random-walk of neutral-ionic domain walls. We simulate the random-walk annihilation process of domain walls on a one-dimensional chain. Full article
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Open AccessArticle
Ivabradine Hydrochloride (S)-Mandelic Acid Co-Crystal: In Situ Preparation during Formulation
Crystals 2017, 7(1), 13; doi:10.3390/cryst7010013 -
Abstract
The pharmaceutical salt ivabradine hydrochloride is indicated for the symptomatic treatment of chronic stable angina pectoris and chronic heart failure. It exhibits extensive polymorphism and co-crystallization, which could be a way to provide an alternative solid form. We conducted a co-crystal screen, from
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The pharmaceutical salt ivabradine hydrochloride is indicated for the symptomatic treatment of chronic stable angina pectoris and chronic heart failure. It exhibits extensive polymorphism and co-crystallization, which could be a way to provide an alternative solid form. We conducted a co-crystal screen, from which two hits were identified: with (S)-mandelic and (R)-mandelic acid. Both structures were determined from single-crystal X-ray diffraction data as co-crystals. The co-crystals were further characterized by common solid-state techniques, such as X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC), solid-state NMR, IR and Raman spectroscopy, and dynamic vapor sorption (DVS). The co-crystal with (S)-mandelic acid was selected for further development; its physical and chemical stability was compared with two different polymorphs of the hydrochloride salt. The co-crystal exhibited a similar stability with the polymorph used in the original drug product and was, therefore, selected for formulation into the drug product. During the pre-formulation experiments, the in situ formation of the co-crystal was achieved during the wet granulation process. The following formulation experiments showed no influence of in situ prepared co-crystal on the overall stability of the bulk, when compared with pre-prepared co-crystal formulation. Full article
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Open AccessArticle
Photo-Thermal Effects in 1D Gratings of Gold Nanoparticles
Crystals 2017, 7(1), 14; doi:10.3390/cryst7010014 -
Abstract
This work investigates the heat delivered by a mono-layer 1D grating of gold nanoparticles (GNPs) created by photo-reduction through two-photon direct laser writing (2P-DLW) in a poly-vinyl alcohol (PVA) matrix doped with HAuCl4, under resonant laser radiation. We drop cast a
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This work investigates the heat delivered by a mono-layer 1D grating of gold nanoparticles (GNPs) created by photo-reduction through two-photon direct laser writing (2P-DLW) in a poly-vinyl alcohol (PVA) matrix doped with HAuCl4, under resonant laser radiation. We drop cast a film of a PVA + HAuCl4 mixture onto a glass substrate, in which we create gratings of 1 mm2 made by stripes of GNPs characterized by high polydispersivity. We demonstrate that, by controlling the pitch of the GNP stripes, we obtain different values of the photo-induced temperature variations. In the framework of thermo-plasmonics, the experimental investigation of the heat generation from a monolayer of gold nanoparticles represents a key element as a starting point to design thermo-smart platforms for sensing, solar energy harvesting and thermo-catalysis. Full article
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Open AccessReview
The Physics of the Hume-Rothery Electron Concentration Rule
Crystals 2017, 7(1), 9; doi:10.3390/cryst7010009 -
Abstract
For a long time we have shared the belief that the physics of the Hume-Rothery electron concentration rule can be deepened only through thorough investigation of the interference phenomenon of itinerant electrons with a particular set of lattice planes, regardless of whether d-states
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For a long time we have shared the belief that the physics of the Hume-Rothery electron concentration rule can be deepened only through thorough investigation of the interference phenomenon of itinerant electrons with a particular set of lattice planes, regardless of whether d-states are involved near the Fermi level or not. For this purpose, we have developed the FLAPW-Fourier theory (Full potential Linearized Augmented Plane Wave), which is capable of determining the square of the Fermi diameter, (2kF)2, and the number of itinerant electrons per atom, e/a, as well as the set of lattice planes participating in the interference phenomenon. By determining these key parameters, we could test the interference condition and clarify how it contributes to the formation of a pseudogap at the Fermi level. Further significant progress has been made to allow us to equally handle transition metal (TM) elements and their compounds. A method of taking the center of gravity energy for energy distribution of electrons with a given electronic state has enabled us to eliminate the d-band anomaly and to determine effective (2kF)2, and e/a, even for systems involving the d-band or an energy gap across the Fermi level. The e/a values for 54 elements covering from Group 1 up to Group 16 in the Periodic Table, including 3d-, 4d- and 5d-elements, were determined in a self-consistent manner. The FLAPW-Fourier theory faces its limit only for elements in Group 17 like insulating solids Cl and their compounds, although the value of e/a can be determined without difficulty when Br becomes metallic under high pressures. The origin of a pseudogap at the Fermi level for a large number of compounds has been successfully interpreted in terms of the interference condition, regardless of the bond-types involved in the van Arkel-Ketelaar triangle map. Full article
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