Crystals

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3 pages, 167 KiB

Open AccessEditorial

Nonclassical Nucleation and Crystallization

by Helmut Cölfen

Crystals 2020, 10(2), 61; https://doi.org/10.3390/cryst10020061 - 23 Jan 2020

Cited by 15 | Viewed by 4753

Abstract

Nucleation and growth are of uttermost importance for crystallization since they determine the structure, shape, and properties of a crystal [...] Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

Research

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14 pages, 4009 KiB

Open AccessArticle

Novel NiMgOH-rGO-Based Nanostructured Hybrids for Electrochemical Energy Storage Supercapacitor Applications: Effect of Reducing Agents

by Konda Shireesha, Thida Rakesh Kumar, Tumarada Rajani, Chidurala Shilpa Chakra, Murikinati Mamatha Kumari, Velpula Divya and Kakarla Raghava Reddy

Crystals 2021, 11(9), 1144; https://doi.org/10.3390/cryst11091144 - 19 Sep 2021

Cited by 12 | Viewed by 2673

Abstract

This paper describes the synthesis and characterization of NiMgOH-rGO nanocomposites made using a chemical co-precipitation technique with various reducing agents (e.g., NaOH and NH₄OH) and reduced graphene oxide at 0.5, 1, and 1.5 percent by weight. UV-visible spectroscopy, Fourier-transform infrared spectroscopy, [...] Read more.

This paper describes the synthesis and characterization of NiMgOH-rGO nanocomposites made using a chemical co-precipitation technique with various reducing agents (e.g., NaOH and NH₄OH) and reduced graphene oxide at 0.5, 1, and 1.5 percent by weight. UV-visible spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, a particle size analyzer, and cyclic voltammetry were used to characterize the composite materials. The formation of the NiMgOH-rGO nanocomposite with crystallite sizes in the range of 10–40 nm was inferred by X-ray diffraction patterns of materials, which suggested interlayers of Ni(OH)₂ and Mg(OH)₂. The interactions between the molecules were detected using Fourier-transform infrared spectroscopy, while optical properties were studied using UV-visible spectroscopy. A uniform average particle size distribution in the range of 1–100 nm was confirmed by the particle size analyzer. Using cyclic voltammetry and galvanostatic charge/discharge measurements in a 6 M KOH solution, the electrochemical execution of NiMgOH-rGO nanocomposites was investigated. At a 1 A/g current density, the NiMgOH-rGO nanocomposites prepared with NH₄OH as a reducing agent had a higher specific capacitance of 1977 F/g. The electrochemical studies confirmed that combining rGO with NiMgOH increased conductivity. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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14 pages, 2382 KiB

Open AccessArticle

Structures of a Phosphoryl Derivative of 4-Allyl-2,4-dihydro-3H-1,2,4-triazole-3-thione: An Illustrative Example of Conformational Polymorphism

by Ivan V. Fedyanin, Aida I. Samigullina, Ivan A. Krutov, Elena L. Gavrilova and Dmitry V. Zakharychev

Crystals 2021, 11(9), 1126; https://doi.org/10.3390/cryst11091126 - 15 Sep 2021

Cited by 4 | Viewed by 2042

Abstract

Two polymorphic forms of a conformationally flexible molecule, 5-[(Diphenylphosphoryl)methyl]-4-(prop-2-en-1-yl)-2,4-dihydro-3H-1,2,4-triazole-3-thione, were obtained by crystallization and characterized by X-ray diffraction analysis and differential scanning calorimetry. The relative stability of polymorphic forms was estimated with DFT calculations of crystal structures and isolated molecules. It turns out, [...] Read more.

Two polymorphic forms of a conformationally flexible molecule, 5-[(Diphenylphosphoryl)methyl]-4-(prop-2-en-1-yl)-2,4-dihydro-3H-1,2,4-triazole-3-thione, were obtained by crystallization and characterized by X-ray diffraction analysis and differential scanning calorimetry. The relative stability of polymorphic forms was estimated with DFT calculations of crystal structures and isolated molecules. It turns out, that in the first more dense polymorph with higher cohesion energy and crystal lattice energy, the molecule adopts an energetically unfavorable conformation, and forms dimers with lower H-bond strength, as compared to the second polymorph. On the other hand, in the second polymorph, the molecule adopts almost the lowest-energy conformation and forms infinite chains via strong H-bonds. The first form that seems to be more thermodynamically stable at room temperature transforms into the second form via two endothermic phase transitions; the apparent irreversibility of the transition is due to high energy difference between the molecular conformations in crystals. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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16 pages, 5183 KiB

Open AccessArticle

Fracture Behavior of Single-Crystal Sapphire in Different Crystal Orientations

by Shizhan Huang, Jiaming Lin, Ningchang Wang, Bicheng Guo, Feng Jiang, Qiuling Wen and Xizhao Lu

Crystals 2021, 11(8), 930; https://doi.org/10.3390/cryst11080930 - 11 Aug 2021

Cited by 13 | Viewed by 5922

Abstract

In order to study the anisotropy of fracture toughness and fracture mechanism of single-crystal sapphire, the three-point bending tests and the single-edge V-notch beam (SEVNB) were used to test the fracture toughness of A-plane, C-plane, and M-plane sapphire, which are widely used in [...] Read more.

In order to study the anisotropy of fracture toughness and fracture mechanism of single-crystal sapphire, the three-point bending tests and the single-edge V-notch beam (SEVNB) were used to test the fracture toughness of A-plane, C-plane, and M-plane sapphire, which are widely used in the semiconductor, aerospace, and other high-tech fields. Fracture morphology was investigated by a scanning electron microscope and three-dimensional video microscopy. The fracture toughness and fracture morphology of different crystal planes of sapphire showed obvious anisotropy and were related to the loading surfaces. C-plane sapphire showed the maximal fracture toughness of 4.24 MPa·m^1/2, and fracture toughness decreases in the order of C-plane, M-plane, and A-plane. The surface roughness is related to the dissipation of fracture energy. The surface roughness of the fracture surface is in the same order as C-plane > M-plane > A-plane. The fracture behavior and morphology of experiments were consistent with the theoretical analysis. C-plane sapphire cleavages along the R-plane with an angle of 57.6 degrees and the rhombohedral twin were activated. M-plane and A-plane sapphire cleavages along their cross-section. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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12 pages, 3271 KiB

Open AccessArticle

Spin-Phonon Coupling in A₂BMnO₆ (A = La, Pr, Nd, Sm, Gd; B = Co, Ni) Double-Perovskite Thin Films: Impact of the A-Site Cation Radius

by Christoph Meyer, Philipp Ksoll, Vladimir Roddatis and Vasily Moshnyaga

Crystals 2021, 11(7), 747; https://doi.org/10.3390/cryst11070747 - 26 Jun 2021

Cited by 3 | Viewed by 1846

Abstract

Two series of B-site ordered, double-perovskite A₂CoMnO₆ and A₂NiMnO₆ (A = La, Pr, Nd, Sm, Gd) epitaxial films with thickness d ~ 100 nm were grown on SrTiO₃(111) substrates via metalorganic aerosol deposition. Polarization and [...] Read more.

Two series of B-site ordered, double-perovskite A₂CoMnO₆ and A₂NiMnO₆ (A = La, Pr, Nd, Sm, Gd) epitaxial films with thickness d ~ 100 nm were grown on SrTiO₃(111) substrates via metalorganic aerosol deposition. Polarization and temperature-dependent Raman spectroscopy were carried out in order to determine the spin-phonon coupling constant, λ, and the impact of the A-site cation radius on the phonon properties. The reduction of the A-site cation radius from La³⁺ down to Gd³⁺ systematically shifts the Raman modes to lower wavenumbers, and decreases the magnetization-induced softening of the Ag breathing mode, described by the spin-phonon coupling constant, λ, which changes from λ = 1.42 cm⁻¹ (La₂CoMnO₆) and λ = 1.53 cm⁻¹ (La₂NiMnO₆) down to λ = 0.58 cm⁻¹ (Gd₂CoMnO₆) and λ = 0.44 cm⁻¹ (Gd₂NiMnO₆). A similar effect of the A-cation radius was established for the c-lattice parameter and Curie temperature, TC, in this series of double-perovskite films. Our observations directly demonstrate a strong impact of the lattice structure on the ferromagnetic superexchange interaction in double perovskites. Moreover, the A₂CoMnO₆ and A₂NiMnO₆ series exhibit very similar behavior of spin-phonon coupling due to the only moderate difference of Co²⁺ and Ni²⁺ cation size. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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21 pages, 3210 KiB

Open AccessArticle

Start-Up of a Solid Oxide Fuel Cell System with a View to Materials Science-Related Aspects, Control and Thermo-Mechanical Stresses

by Konrad W. Eichhorn Colombo and Vladislav V. Kharton

Crystals 2021, 11(7), 732; https://doi.org/10.3390/cryst11070732 - 24 Jun 2021

Cited by 5 | Viewed by 3010

Abstract

The start-up of a solid oxide fuel cell (SOFC) is investigated by means of numerical simulation with a view to material and operational constraints on a component and system level, as well as thermo-mechanical stresses. The applied multi-physics modeling approach couples thermal-, electrochemical, [...] Read more.

The start-up of a solid oxide fuel cell (SOFC) is investigated by means of numerical simulation with a view to material and operational constraints on a component and system level, as well as thermo-mechanical stresses. The applied multi-physics modeling approach couples thermal-, electrochemical, chemical-, and thermo-mechanical phenomena. In addition to constraints, emphasis is given to degrees of freedom with respect to manipulated and controlled variables of the system. Proper ramping during the start-up procedure keeps critical parameter values within a safe regime. Of particular interest are gradient in terms of temperature and chemical concentrations. Nevertheless, simulations show that thermo-mechanical stresses are relatively high during the initial start-up phase, the system is, thus, more susceptible to failure. The combination of multi-physics modeling in conjunction with practical control aspects for start-up of an SOFC, which is presented in this paper, is important for applications. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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9 pages, 3367 KiB

Open AccessArticle

Synthesis and Optical Characterizations of Yb³⁺: Ca_xSr_1−xF₂ Transparent Ceramics

by Hongran Ling, Bingchu Mei, Weiwei Li, Yu Yang, Yongqiang Zhang and Xinwen Liu

Crystals 2021, 11(6), 652; https://doi.org/10.3390/cryst11060652 - 8 Jun 2021

Viewed by 1875

Abstract

In this study, 3 at.% Yb³⁺: Ca_xSr_1−xF₂ nanopowders were synthesized via the chemical co-precipitation method. Highly transparent 3 at.% Yb³⁺: Ca_xSr_1−xF₂ ceramics with various CaF₂ concentrations were fabricated [...] Read more.

In this study, 3 at.% Yb³⁺: Ca_xSr_1−xF₂ nanopowders were synthesized via the chemical co-precipitation method. Highly transparent 3 at.% Yb³⁺: Ca_xSr_1−xF₂ ceramics with various CaF₂ concentrations were fabricated by hot-pressed sintering. The 3 at.% Yb³⁺: Ca_xSr_1−xF₂ nanopowders exhibited a spherical shape with slight agglomeration, and their particle size ranged from 26 nm to 36 nm. With an increase of the CaF₂ concentration, the peak shape changed significantly and the width of the emission band increased inhomogeneously. The minimal fluorescence lifetime at the wavelength of 1011 nm of 3 at.% Yb³⁺: Ca_xSr_1−xF₂ transparent ceramics with various CaF₂ concentrations was higher than 3.25 ms, which was longer than that of the 3 at.% Yb³⁺: CaF₂ (2.6 ms) and the 3 at.% Yb³⁺: SrF₂ (3.22 ms) reported in previous literature. The results indicate that incorporating Ca²⁺ ions into the SrF₂ is an effective method to modulate the optical properties of transparent ceramics. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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23 pages, 5241 KiB

Open AccessArticle

Bulk and Surface Conformations in Solid-State Lovastatin: Spectroscopic and Molecular Dynamics Studies

by Anuradha R. Pallipurath, Jonathan M. Skelton, Andrew Britton, Elizabeth A. Willneff and Sven L. M. Schroeder

Crystals 2021, 11(5), 509; https://doi.org/10.3390/cryst11050509 - 4 May 2021

Cited by 1 | Viewed by 2401

Abstract

Conformational flexibility in molecules can give rise to a range of functional group terminations at crystal surfaces and dynamic disorder in the bulk. In this work, we explore the conformational behavior of the drug molecule lovastatin in the crystallographically disordered solid and at [...] Read more.

Conformational flexibility in molecules can give rise to a range of functional group terminations at crystal surfaces and dynamic disorder in the bulk. In this work, we explore the conformational behavior of the drug molecule lovastatin in the crystallographically disordered solid and at crystal surfaces through a combination of computational modeling and spectroscopy. Gas-phase and periodic quantum-chemical calculations are used to study the potential energy surface associated with rotatable bonds to examine the disorder in bulk. These calculations are combined with vibrational and X-ray photoelectron spectroscopy measurements to obtain insight into the conformations in bulk and at the surface. Our MD simulations show that the bulk disorder is driven by cooperative motion of the butyl group on the S-butanoate moiety along one crystallographic direction beyond a unit cell. The calculations show that the O-H group can rotate relatively freely between two low-energy conformers in the gas phase but is locked in position by intermolecular H-bonding interactions in the bulk crystal, and we find tentative spectroscopic evidence for the second conformer being present at the surface. We also comment on the relative utility of these different techniques for studying molecular conformation in bulk and at surfaces and highlight possible areas for future developments. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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16 pages, 3373 KiB

Open AccessArticle

Cocrystals Based on 4,4’-bipyridine: Influence of Crystal Packing on Melting Point

by Daniel Ejarque, Teresa Calvet, Mercè Font-Bardia and Josefina Pons

Crystals 2021, 11(2), 191; https://doi.org/10.3390/cryst11020191 - 16 Feb 2021

Cited by 13 | Viewed by 3739

Abstract

The reactions of piperonylic acid (HPip) and cinnamic acid (HCinn) with 4,4’-bipyridine (4,4’-bipy) have been assayed using the same synthetic methodology, yielding two binary cocrystals with different acid:4,4’-bipy molar ratios, (HPip)(4,4’-bipy) (1) and (HCinn)₂(4,4’-bipy) (2). The melting [...] Read more.

The reactions of piperonylic acid (HPip) and cinnamic acid (HCinn) with 4,4’-bipyridine (4,4’-bipy) have been assayed using the same synthetic methodology, yielding two binary cocrystals with different acid:4,4’-bipy molar ratios, (HPip)(4,4’-bipy) (1) and (HCinn)₂(4,4’-bipy) (2). The melting point (m.p.) of these cocrystals have been measured and a remarkable difference (ΔT ≈ 78 °C) between them was observed. Moreover, the two cocrystals have been characterized by powder X-ray diffraction (PXRD), elemental analysis (EA), FTIR-ATR, ¹H NMR spectroscopies, and single-crystal X-ray diffraction. The study of their structural packings via Hirshfeld surface analysis and energy frameworks revealed the important contribution of the π···π and C-H···π interactions to the formation of different structural packing motifs, this being the main reason for the difference of m.p. between them. Moreover, it has been observed that 1 and 2 presented the same packing motifs as the crystal structure of their corresponding carboxylic acids, but 1 and 2 showed lower m.p. than those of the carboxylic acids, which could be related to the lower strength of the acid-pyridine heterosynthons respect to the acid-acid homosynthons in the crystal structures. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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22 pages, 6359 KiB

Open AccessArticle

Synthesis, Cytotoxic Activity, Crystal Structure, DFT Studies and Molecular Docking of 3-Amino-1-(2,5-dichlorophenyl)-8-methoxy-1H-benzo[f]chromene-2-carbonitrile

by Menna El Gaafary, Tatiana Syrovets, Hany M. Mohamed, Ahmed A. Elhenawy, Ahmed M. El-Agrody, Abd El-Galil E. Amr, Hazem A. Ghabbour and Abdulrahman A. Almehizia

Crystals 2021, 11(2), 184; https://doi.org/10.3390/cryst11020184 - 13 Feb 2021

Cited by 28 | Viewed by 5047

Abstract

The target compound 3-amino-1-(2,5-d ichlorophenyl)-8-methoxy-1H-benzo[f]-chromene-2-carbonitrile (4) was synthesized via a reaction of 6-methoxynaphthalen-2-ol (1), 2,5-dichlorobenzaldehyde (2), and malononitrile (3) in ethanolic piperidine solution under microwave irradiation. The newly synthesized β-enaminonitrile was characterized by FT-IR, ¹H [...] Read more.

The target compound 3-amino-1-(2,5-d ichlorophenyl)-8-methoxy-1H-benzo[f]-chromene-2-carbonitrile (4) was synthesized via a reaction of 6-methoxynaphthalen-2-ol (1), 2,5-dichlorobenzaldehyde (2), and malononitrile (3) in ethanolic piperidine solution under microwave irradiation. The newly synthesized β-enaminonitrile was characterized by FT-IR, ¹H NMR, ¹³C NMR, mass spectroscopy, elemental analysis and X-ray diffraction data. Its cytotoxic activity was evaluated against three different human cancer cell lines MDA-MB-231, A549, and MIA PaCa-2 in comparison to the positive controls etoposide and camptothecin employing the XTT cell viability assay. The analysis of the Hirshfeld surface was utilized to visualize the reliability of the crystal package. The obtained results confirmed that the tested molecule revealed promising cytotoxic activities against the three cancer cell lines. Furthermore, theoretical calculations (DFT) were carried out with the Becke3-Lee-Yang-parr (B3LYP) level using 6-311++G(d,p) basis. The optimization geometry for molecular structures was in agreement with the X-ray structure data. The HOMO-LUMO energy gap of the studied system was discussed. The intermolecular-interactions were studied through analysis of the topological-electron-density(r) using the QTAIM and NCI methods. The novel compound exhibited favorable ADMET properties and its molecular modeling analysis showed strong interaction with DNA methyltransferase 1. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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13 pages, 2982 KiB

Open AccessArticle

Coordination Polymers in Dicyanamido-Cadmium(II) with Diverse Network Dimensionalities

by Franz A. Mautner, Patricia V. Jantscher, Roland C. Fischer, Ana Torvisco, Klaus Reichmann, Nahed M. H. Salem, Kenneth J. Gordon, Febee R. Louka and Salah S. Massoud

Crystals 2021, 11(2), 181; https://doi.org/10.3390/cryst11020181 - 12 Feb 2021

Cited by 9 | Viewed by 2258

Abstract

The synthesis and structural characterization of six dicyanamido-cadmium(II) complexes are reported: catena-[Cd(μ_1,3-dca)(μ_1,5-dca)(3-ampy)] (1), catena-[Cd₃(μ_1,3,5-dca)₂(μ_1,5-dca)₄(pyNO)₂(H₂O)₂] (2), catena-{Cd(H [...] Read more.

The synthesis and structural characterization of six dicyanamido-cadmium(II) complexes are reported: catena-[Cd(μ_1,3-dca)(μ_1,5-dca)(3-ampy)] (1), catena-[Cd₃(μ_1,3,5-dca)₂(μ_1,5-dca)₄(pyNO)₂(H₂O)₂] (2), catena-{Cd(H₂O)₂(μ_1,5-dca)₂](2,6-lut-NO)} (3), catena-[Cd(Me₂en)(μ_1,5-dca)₂] (4), catena-[Cd(Me₄en)(μ_1,5-dca)₂] (5), and [Cd(1,8-damnp)₂(dca)₂] (6), where dca = dicyanamide anion, 3-ampy = 3-aminopyridine, pyNO = pyridine-N-oxide, 2,6-lut-NO = 2,6-lutidine-N-oxide, Me₂en = N,N-dimethyl-ethylenediamine, Me₄en = N,N,N′,N′-tetramethyl-ethylenediamine, and 1,8-damnp = 1,8-diaminonaphthaline. The coordination polymers have different dimensionalities: 1 and 5 form 3D networks structures; 3 and 4 form polymeric 1D chains and 1DD double chains, respectively. Ribbons of three fused polymeric chains are observed in 2. In 6, the mononuclear complex units form a hydrogen-bonded supramolecular 3D network. In the coordination polymer compounds, the dca linkers display three bonding modes: the most common μ_1,5-dca and the least popular μ_1,3- and μ_1,3,5-dca bonding. The luminescence emission and thermal properties of the complexes were investigated. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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15 pages, 3057 KiB

Open AccessArticle

Structural Characterization, Magnetic and Luminescent Properties of Praseodymium(III)-4,4,4-Trifluoro-1-(2-Naphthyl)Butane-1,3-Dionato(1-) Complexes

by Franz A. Mautner, Florian Bierbaumer, Roland C. Fischer, Ramon Vicente, Ànnia Tubau, Arnau Ferran and Salah S. Massoud

Crystals 2021, 11(2), 179; https://doi.org/10.3390/cryst11020179 - 11 Feb 2021

Cited by 11 | Viewed by 3200

Abstract

Four new Pr(III) mononuclear complexes of formula [Pr(ntfa)₃(MeOH)₂] (1), [Pr(ntfa)₃(bipy)₂] (2), [Pr(ntfa)₃(4,4′-Mt₂bipy)] (3) and [Pr(ntfa)₃(5,5′-Me₂bipy)] (4), where ntfa = [...] Read more.

Four new Pr(III) mononuclear complexes of formula [Pr(ntfa)₃(MeOH)₂] (1), [Pr(ntfa)₃(bipy)₂] (2), [Pr(ntfa)₃(4,4′-Mt₂bipy)] (3) and [Pr(ntfa)₃(5,5′-Me₂bipy)] (4), where ntfa = 4,4,4-trifuoro-1-(naphthalen-2-yl)butane-1,3-dionato(1-), 5,5′-Me2bipy = 5,5′-dimethyl-2,2′-dipyridine, 4,4′-Mt2bipy = 4,4′-dimethoxy-2,2′-dipyridine, have been synthesized and structurally characterized. The complexes display the coordination numbers 8 for 1, 3 and 4, and 10 for 2. Magnetic measurements of complexes 1–4 were consistent with a magnetically uncoupled Pr³⁺ ion in the ³H₄ ground state. The solid state luminescence studies showed that the ancillary chelating bipyridyl ligands in the 2–4 complexes greatly enhance the luminescence emission in the visible and NIR regions through efficient energy transfer from the ligands to the central Pr³⁺ ion; behaving as “antenna” ligands. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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15 pages, 4930 KiB

Open AccessArticle

Crystal Structures of New Ivermectin Pseudopolymorphs

by Kirill Shubin, Agris Bērziņš and Sergey Belyakov

Crystals 2021, 11(2), 172; https://doi.org/10.3390/cryst11020172 - 9 Feb 2021

Cited by 6 | Viewed by 3585

Abstract

New pseudopolymorphs of ivermectin (IVM), a potential anti-COVID-19 drug, were prepared. The crystal structure for three pseudopolymorphic crystalline forms of IVM has been determined using single-crystal X-ray crystallographic analysis. The molecular conformation of IVM in crystals has been compared with the conformation of [...] Read more.

New pseudopolymorphs of ivermectin (IVM), a potential anti-COVID-19 drug, were prepared. The crystal structure for three pseudopolymorphic crystalline forms of IVM has been determined using single-crystal X-ray crystallographic analysis. The molecular conformation of IVM in crystals has been compared with the conformation of isolated molecules modeled by DFT calculations. In a solvent with relatively small molecules (ethanol), IVM forms monoclinic crystal structure (space group I2), which contains two types of voids. When crystallized from solvents with larger molecules, like γ-valerolactone (GVL) and methyl tert-butyl ether (MTBE), IVM forms orthorhombic crystal structure (space group P2₁2₁2₁). Calculations of the lattice energy indicate that interactions between IVM and solvents play a minor role; the main contribution to energy is made by the interactions between the molecules of IVM itself, which form a framework in the crystal structure. Interactions between IVM and molecules of solvents were evaluated using Hirshfeld surface analysis. Thermal analysis of the new pseudopolymorphs of IVM was performed by differential scanning calorimetry and thermogravimetric analysis. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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18 pages, 8590 KiB

Open AccessArticle

In Situ Investigations on Stress and Microstructure Evolution in Polycrystalline Ti(C,N)/α-Al₂O₃ CVD Coatings under Thermal Cycling Loads

by José García, Maiara Moreno, Wei Wan, Daniel Apel, Haroldo Pinto, Matthias Meixner, Manuela Klaus and Christoph Genzel

Crystals 2021, 11(2), 158; https://doi.org/10.3390/cryst11020158 - 4 Feb 2021

Cited by 11 | Viewed by 3188

Abstract

The stress behavior and the associated microstructure evolution of industrial Ti(C,N)/α-Al₂O₃ coatings subjected to thermal cycling are investigated by in situ energy dispersive synchrotron X-ray diffraction and transmission electron microscopy. Temperature-dependent stresses and changes in microstructural parameters (domain size and [...] Read more.

The stress behavior and the associated microstructure evolution of industrial Ti(C,N)/α-Al₂O₃ coatings subjected to thermal cycling are investigated by in situ energy dispersive synchrotron X-ray diffraction and transmission electron microscopy. Temperature-dependent stresses and changes in microstructural parameters (domain size and microstrain) are analyzed by in situ measurements at different temperatures between 25 and 800 °C, both in the heating up and cooling down step, including several thermal cycles. Transmission electron microscopy is used to evaluate defects before and after the thermal treatment. The introduction of high compressive stresses in α-Al₂O₃ by top-blasting is connected to a high defect density at the basal planes of the alumina layer. The stress relaxation of the alumina layer at high temperatures is associated with a successive annihilation of defects until a reversible temperature-dependent stress condition is set. Top-blasting does not change the initial microstructure and residual stress of the Ti(C,N) layer. Ti(C,N) shows a cyclic stress behavior associated with the heat treatment and an elastic deformation behavior in the temperature range investigated. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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10 pages, 1782 KiB

Open AccessArticle

Fast-Response Liquid Crystal for Spatial Light Modulator and LiDAR Applications

by Junyu Zou, Qian Yang, En-Lin Hsiang, Haruki Ooishi, Zhuo Yang, Kifumi Yoshidaya and Shin-Tson Wu

Crystals 2021, 11(2), 93; https://doi.org/10.3390/cryst11020093 - 22 Jan 2021

Cited by 34 | Viewed by 4351

Abstract

We report a new nematic mixture for liquid-crystal-on-silicon spatial light modulator (SLM) and light detection and ranging (LiDAR) applications. The mixture exhibits a relatively high birefringence (Δn), moderate dielectric anisotropy (Δɛ), low viscosity, and reasonably good photostability. To achieve [...] Read more.

We report a new nematic mixture for liquid-crystal-on-silicon spatial light modulator (SLM) and light detection and ranging (LiDAR) applications. The mixture exhibits a relatively high birefringence (Δn), moderate dielectric anisotropy (Δɛ), low viscosity, and reasonably good photostability. To achieve 2π phase change at 5 V, the response time (on + off) is 2.5 ms at 40 °C with λ = 633 nm, and 5.9 ms with λ = 905 nm. After exposure by a blue laser (λ = 465 nm) with a total dosage up to 20 MJ/cm², this mixture shows no sign of photodegradation. Widespread applications of this material for high brightness SLMs, LiDAR, near-eye displays, and head-up displays are foreseeable. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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12 pages, 2418 KiB

Open AccessArticle

One-Step Carbothermal Synthesis of Super Nanoadsorbents for Rapid and Recyclable Wastewater Treatment

by Wen-chan Ji, Ping Hu, Xiao-yu Wang, Sandra Elizabeth Saji, Tian Chang, Xin-yu Zhu, Fairy Fan Yang, Qi-gao Cao, Rui Dang, Kuai-she Wang and Zongyou Yin

Crystals 2021, 11(1), 75; https://doi.org/10.3390/cryst11010075 - 18 Jan 2021

Cited by 1 | Viewed by 2217

Abstract

As a potential magnetic super adsorbent in wastewater treatment, Fe₃O₄ has been researched intensively up to date. However, its key problem of poor comprehensive magnetic properties is still challenging. In this work, an effective solution to this problem has been [...] Read more.

As a potential magnetic super adsorbent in wastewater treatment, Fe₃O₄ has been researched intensively up to date. However, its key problem of poor comprehensive magnetic properties is still challenging. In this work, an effective solution to this problem has been developed by a one-step carbothermal synthesis of Fe₃O₄ crystals, which are merited with pure-stoichiometry (FeO-phase free), high crystallinity, small-size (~10 nm), strong magnetism and sensitive magnetic response. The unveiled saturation magnetization of Fe₃O₄ nanoparticles reaches as high as 90.32 emu·g⁻¹, and the fastest magnetic response time is as short as only 5 s. Such magnetic Fe₃O₄ super adsorbents exhibit outstanding performance when applied as an adsorbent for wastewater treatment. They can quickly and effectively adsorb methylene blue with an adsorption capacity of 62.5 mg·g⁻¹, which is much higher than that of Fe₃O₄ adsorbents prepared by other methods reported in the literature. Importantly, this capacity is refreshable after removing the adsorbed methylene blue just by ultrasonic cleaning. With such combined outstanding magnetic properties and recyclable adsorption capacity, the problems associated with the conventional adsorbent solid–liquid separation could be resolved, thus making a forward development towards industrial wastewater treatment. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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15 pages, 3218 KiB

Open AccessArticle

Evaluation of Novel Glycerol/PEO Gel Polymer Electrolytes for Non-Toxic Dye-Sensitized Solar Cells with Natural Dyes Regarding Long-Term Stability and Reproducibility

by Jan Lukas Storck, Marius Dotter, Bennet Brockhagen and Timo Grothe

Crystals 2020, 10(12), 1158; https://doi.org/10.3390/cryst10121158 - 19 Dec 2020

Cited by 11 | Viewed by 2866

Abstract

Alongside efficiency, long-term stability of dye-sensitized solar cells (DSSCs) is a key factor regarding their commercialization. One suitable and cost-effective method to increase the long-term stability is to prevent leakage and evaporation of the electrolyte by gelling it with polymers such as poly(ethylene [...] Read more.

Alongside efficiency, long-term stability of dye-sensitized solar cells (DSSCs) is a key factor regarding their commercialization. One suitable and cost-effective method to increase the long-term stability is to prevent leakage and evaporation of the electrolyte by gelling it with polymers such as poly(ethylene oxide) (PEO) and gaining a gel polymer electrolyte (GPE). In this study, a GPE based on PEO and glycerol is investigated for the first time as electrolyte for environmentally friendly DSSCs with natural dyes. To evaluate the novel glycerol/PEO GPE, the ionic conductivity and resulting efficiency progressions of DSSCs were measured for 75 days. Different molecular weights (MWs) of PEO and blending with poly(vinylidene fluoride) (PVDF) had negligible impact on efficiencies. 17 wt% PEO was found to be more suitable than lower concentrations and resulted in a relatively high efficiency over 75 days. A glycerol electrolyte without PEO had higher ionic conductivity and achieved higher efficiencies as well but leaked from the unsealed DSSCs. In addition, the reproducibility was examined especially, which appeared to be reduced by considerable differences between identical DSSCs and between measurements of the same DSSC at different times. This emphasizes the relevance of studying multiple DSSC per sample to ensure reliable results. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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7 pages, 1200 KiB

Open AccessCommunication

Crystallization and Preliminary X-ray Diffraction Study of a Novel Bacterial Homologue of Mammalian Hormone-Sensitive Lipase (halip1) from Halocynthiibacter arcticus

by Sangeun Jeon, Jisub Hwang, Wanki Yoo, Hackwon Do, Han-Woo Kim, Kyeong Kyu Kim, Jun Hyuck Lee and T. Doohun Kim

Crystals 2020, 10(11), 963; https://doi.org/10.3390/cryst10110963 - 23 Oct 2020

Cited by 1 | Viewed by 1965

Abstract

Hormone sensitive lipase is a central enzyme in triacylglycerol hydrolysis, lipid modification, and transformation of various lipids. Microbial hormone-sensitive lipases, which are highly similar to a catalytic domain of mammalian equivalents, have attracted strong attention due to their application potentials. Here, characterization and [...] Read more.

Hormone sensitive lipase is a central enzyme in triacylglycerol hydrolysis, lipid modification, and transformation of various lipids. Microbial hormone-sensitive lipases, which are highly similar to a catalytic domain of mammalian equivalents, have attracted strong attention due to their application potentials. Here, characterization and a preliminary X-ray crystallographic analysis of a novel bacterial homologue of hormone-sensitive lipase (HaLip1) from Halocynthiibacter arcticus is reported. Sequence analysis shows that HaLip1 has a conserved serine residue within the GDSAG motif. In addition, a characteristic HGGG motif for oxyanion formation was identified. The HaLip1 protein was overexpressed in E. coli. SDS-PAGE, overlay assay, and mass analysis were performed to confirm purity and activity of HaLip1 protein. Furthermore, HaLip1 was crystallized in a condtion consisting of 25% (w/v) PEG 3350, 0.1 M Hepes-KOH, pH 7.5, 0.2 M sodium chloride. Diffraction data were processed to 1.30 Å with an R_merge of 7.3%. The crystals of HaLip1 belong to the P2₁2₁2₁, with unit cell parameters of a = 54.6 Å, b = 59.5 Å, and c = 82.9 Å. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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17 pages, 3197 KiB

Open AccessArticle

Calcium Phosphate Nanoparticle Precipitation by a Continuous Flow Process: A Design of Experiment Approach

by Lorenzo Degli Esposti, Alessandro Dotti, Alessio Adamiano, Claudia Fabbi, Eride Quarta, Paolo Colombo, Daniele Catalucci, Claudio De Luca and Michele Iafisco

Crystals 2020, 10(10), 953; https://doi.org/10.3390/cryst10100953 - 19 Oct 2020

Cited by 15 | Viewed by 3921

Abstract

Calcium phosphate nanoparticles (CaP NPs) are an efficient class of nanomaterials mainly used for biomedical applications but also very promising in other sectors such as cosmetics, catalysis, water remediation, and agriculture. Unfortunately, as in the case of other nanomaterials, their wide application is [...] Read more.

Calcium phosphate nanoparticles (CaP NPs) are an efficient class of nanomaterials mainly used for biomedical applications but also very promising in other sectors such as cosmetics, catalysis, water remediation, and agriculture. Unfortunately, as in the case of other nanomaterials, their wide application is hindered by the difficulty to control size, morphology, purity and degree of particle aggregation in the translation from laboratory to industrial scale production that is usually carried out in batch or semi-batch systems. In this regard, the use of continuous flow synthesis can help to solve this problem, providing more homogenous reaction conditions and highly reproducible synthesis. In this paper, we have studied with a design of experiment approach the precipitation of citrate functionalized CaP NPs aided by sonication using a continuous flow wet chemical precipitation, and the effect of some of the most relevant process factors (i.e., reactant flow rate, sonication amplitude, and maturation time) on the physico-chemical properties of the NPs were evaluated. From the statistical data analysis, we have found that CaP NP dimensions are influenced by the reactor flow rate, while the crystalline domain dimensions and product purity are influenced by the maturation process. This work provides a deeper understanding of the relationships between reaction process factors and CaP NP properties, and is a relevant contribution for the scale-up production of CaP NPs for nanomedical or other applications. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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10 pages, 2872 KiB

Open AccessArticle

The Detection of Monoclinic Zirconia and Non-Uniform 3D Crystallographic Strain in a Re-Oxidized Ni-YSZ Solid Oxide Fuel Cell Anode

by Thomas M. M. Heenan, Antonis Vamvakeros, Chun Tan, Donal P. Finegan, Sohrab R. Daemi, Simon D. M. Jacques, Andrew M. Beale, Marco Di Michiel, Dan J. L. Brett and Paul R. Shearing

Crystals 2020, 10(10), 941; https://doi.org/10.3390/cryst10100941 - 16 Oct 2020

Cited by 4 | Viewed by 3298

Abstract

The solid oxide fuel cell (SOFC) anode is often composed of nickel (Ni) and yttria-stabilized zirconia (YSZ). The yttria is added in small quantities (e.g., 8 mol %) to maintain the crystallographic structure throughout the operating temperatures (e.g., room-temperature to >800 °C). The [...] Read more.

The solid oxide fuel cell (SOFC) anode is often composed of nickel (Ni) and yttria-stabilized zirconia (YSZ). The yttria is added in small quantities (e.g., 8 mol %) to maintain the crystallographic structure throughout the operating temperatures (e.g., room-temperature to >800 °C). The YSZ skeleton provides a constraining structural support that inhibits degradation mechanisms such as Ni agglomeration and thermal expansion miss-match between the anode and electrolyte layers. Within this structure, the Ni is deposited in the oxide form and then reduced during start-up; however, exposure to oxygen (e.g., during gasket failure) readily re-oxidizes the Ni back to NiO, impeding electrochemical performance and introducing complex structural stresses. In this work, we correlate lab-based X-ray computed tomography using zone plate focusing optics, with X-ray synchrotron diffraction computed tomography to explore the crystal structure of a partially re-oxidized Ni/NiO-YSZ electrode. These state-of-the-art techniques expose several novel findings: non-isotropic YSZ lattice distributions; the presence of monoclinic zirconia around the oxidation boundary; and metallic strain complications in the presence of variable yttria content. This work provides evidence that the reduction–oxidation processes may destabilize the YSZ structure, producing monoclinic zirconia and microscopic YSZ strain, which has implications upon the electrode’s mechanical integrity and thus lifetime of the SOFC. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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13 pages, 4198 KiB

Open AccessArticle

In Situ Electric-Field Study of Surface Effects in Domain Engineered Pb(In_1/2Nb_1/2)O₃-Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ Relaxor Crystals by Grazing Incidence Diffraction

by Markys G. Cain, Margo Staruch, Paul Thompson, Christopher Lucas, Didier Wermeille, Yves Kayser, Burkhard Beckhoff, Sam E. Lofland and Peter Finkel

Crystals 2020, 10(9), 728; https://doi.org/10.3390/cryst10090728 - 20 Aug 2020

Cited by 2 | Viewed by 2700

Abstract

In this work, we present a grazing incidence X-ray diffraction study of the surface of a 0.24Pb(In_1/2Nb_1/2)O₃-Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PIN-PMN-PT) [011] poled rhombohedral single crystal. The near surface microstructure (the top several [...] Read more.

In this work, we present a grazing incidence X-ray diffraction study of the surface of a 0.24Pb(In_1/2Nb_1/2)O₃-Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PIN-PMN-PT) [011] poled rhombohedral single crystal. The near surface microstructure (the top several tens to hundreds of unit cells) was measured in situ under an applied electric field. The strains calculated from the change in lattice parameters have been compared to the macroscopic strain measured with a strain gauge affixed to the sample surface. The depth dependence of the electrostrain at the crystal surface was investigated as a function of temperature. The analysis revealed hidden sweet spots featuring unusually high strains that were observed as a function of depth, temperature and orientation of the lattice planes. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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23 pages, 14465 KiB

Open AccessArticle

Computational Analysis of Low-Energy Dislocation Configurations in Graded Layers

by Daniele Lanzoni, Fabrizio Rovaris and Francesco Montalenti

Crystals 2020, 10(8), 661; https://doi.org/10.3390/cryst10080661 - 1 Aug 2020

Cited by 3 | Viewed by 2783

Abstract

Graded layers are widely exploited in semiconductor epitaxy as they typically display lower threading dislocation density with respect to constant-composition layers. However, strain relaxation occurs via a rather complex distribution of misfit dislocations. Here we exploit a suitable computational approach to investigate dislocation [...] Read more.

Graded layers are widely exploited in semiconductor epitaxy as they typically display lower threading dislocation density with respect to constant-composition layers. However, strain relaxation occurs via a rather complex distribution of misfit dislocations. Here we exploit a suitable computational approach to investigate dislocation distributions minimizing the elastic energy in overcritical constant-composition and graded layers. Predictions are made for SiGe/Si systems, but the methodology, based on the exact (albeit in two dimensions and within linear elasticity theory) solution of the stress field associated with a periodic distribution of defects, is general. Results are critically compared with experiments, when possible, and with a previous mean-field model. A progressive transition from one-dimensional to two-dimensional distributions of defects when continuous linear grading is approached is clearly observed. Interestingly, analysis of the low-energy distribution of dislocations reveals close analogies with typical pile-ups as produced by dislocation multiplication. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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12 pages, 5626 KiB

Open AccessArticle

Plasmonic Photomobile Polymer Films

by Riccardo Castagna, Massimo Rippa, Francesco Simoni, Fulvia Villani, Giuseppe Nenna and Lucia Petti

Crystals 2020, 10(8), 660; https://doi.org/10.3390/cryst10080660 - 1 Aug 2020

Cited by 6 | Viewed by 2767

Abstract

In this work, we introduce the approaches currently followed to realize photomobile polymer films and remark on the main features of the system based on a biphasic structure recently proposed. We describe a method of making a plasmonic nanostructure on the surface of [...] Read more.

In this work, we introduce the approaches currently followed to realize photomobile polymer films and remark on the main features of the system based on a biphasic structure recently proposed. We describe a method of making a plasmonic nanostructure on the surface of photomobile films. The characterization of the photomobile film is performed by means of Dark Field Microscopy (DFM), Scanning Electron Microscopy (SEM), and Atomic Force Microscopy (AFM). Preliminary observations of the light-induced effects on the Localized Surface Plasmon Resonance are also reported. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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13 pages, 4462 KiB

Open AccessArticle

Crystal Structure of the Apo and the ADP-Bound Form of Choline Kinase from Plasmodium falciparum

by Archimede Torretta, Luisa Carlota Lopez-Cara and Emilio Parisini

Crystals 2020, 10(7), 613; https://doi.org/10.3390/cryst10070613 - 14 Jul 2020

Cited by 4 | Viewed by 3976

Abstract

Among the malaria-causing parasites, the deadliest is Plasmodium falciparum, which accounts for the majority of the fatalities. As the infection progresses inside erythrocytes, major cellular and metabolic changes take place. For its own growth, the parasite relies on the accumulation of phospholipids, [...] Read more.

Among the malaria-causing parasites, the deadliest is Plasmodium falciparum, which accounts for the majority of the fatalities. As the infection progresses inside erythrocytes, major cellular and metabolic changes take place. For its own growth, the parasite relies on the accumulation of phospholipids, which are essential for membrane synthesis. Within the Kennedy pathway, the P. falciparum choline kinase (PfChoK) has a central role in the biosynthesis of phosphatidylcholine and its selective inhibition leads to the parasite arrest and eradication. Here, we report the crystal structure of the apo and the ADP-bound form of choline kinase from Plasmodium falciparum at 2.0 and 2.2 Å resolution, respectively. These new structural data will facilitate the implementation of effective structure-based drug development strategies against PfChoK in the fight against malaria. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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13 pages, 6118 KiB

Open AccessArticle

In Situ Imaging of Domain Structure Evolution in LaBGeO₅ Single Crystals

by Andrey Akhmatkhanov, Constantine Plashinnov, Maxim Nebogatikov, Evgenii Milov, Ilya Shnaidshtein and Vladimir Shur

Crystals 2020, 10(7), 583; https://doi.org/10.3390/cryst10070583 - 6 Jul 2020

Cited by 6 | Viewed by 2437

Abstract

LaBGeO₅ (LBGO) crystals are unique ferroelectric materials for manufacturing highly efficient UV laser sources based on frequency conversion. This is due to their low cut-off wavelength, high nonlinear-optical coefficients, and non-hygroscopicity. Periodical poling requires a deep study of domain kinetics in these [...] Read more.

LaBGeO₅ (LBGO) crystals are unique ferroelectric materials for manufacturing highly efficient UV laser sources based on frequency conversion. This is due to their low cut-off wavelength, high nonlinear-optical coefficients, and non-hygroscopicity. Periodical poling requires a deep study of domain kinetics in these crystals. Domain imaging by Cherenkov second harmonic generation microscopy was used to reveal the main processes of domain structure evolution: (1) growth and merging of isolated domains, (2) growth of stripe domains formed on the artificial linear surface defects, and (3) domain shrinkage. In a low field, growth of triangular domains and fast shape recovery after merging were observed, while in a high field, the circular domains grew independently after merging. The revealed essential wall motion anisotropy decreased with the field. The anisotropy led to significant shape transformations during domain shrinkage in low field. The formation of short-lived triangular domains rotated by 180 degrees with respect to the growing isolated domains was observed. The obtained results were explained within the kinetic approach to domain structure evolution based on the analogy between the growth of crystals and ferroelectric domains, taking into account the gradual transition from determined nucleation in low field to the stochastic one in high field. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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10 pages, 4670 KiB

Open AccessArticle

Partial and Total Substitution of Zn by Mg in the Cu₂ZnSnS₄ Structure

by Diana M. Mena Romero, David Victoria Valenzuela and Cristy L. Azanza Ricardo

Crystals 2020, 10(7), 578; https://doi.org/10.3390/cryst10070578 - 4 Jul 2020

Cited by 3 | Viewed by 2519

Abstract

Cu

_{2}

ZnSnS

_{4}

(CZTS) is a quaternary semiconductor that has emerged as a promising component in solar absorber materials due to its excellent optical properties such as band-gap energy of ca. 1.5 eV and significant absorption coefficient in the order of 10 [...] Read more.

Cu

_{2}

ZnSnS

_{4}

(CZTS) is a quaternary semiconductor that has emerged as a promising component in solar absorber materials due to its excellent optical properties such as band-gap energy of ca. 1.5 eV and significant absorption coefficient in the order of 10

^{4}

cm

^{- 1}

. Nevertheless, the energy conversion efficiency of CZTS-based devices has not reached the theoretical limits yet, possibly due to the existence of antisite defects (such as Cu

_{Zn}

or Zn

_{Cu}

) and secondary phases. Based on electronic similarities with Zn, Mg has been proposed for Zn substitution in the CZTS structure in the design of alternative semiconductors for thin-film solar cell applications. This work aims to study the properties of the CZTS having Mg incorporated in the structure replacing Zn, with the following stoichiometry: x = 0, 0.25, 0.5, 0.75, and 1 in the formula Cu

_{2}

Zn

_{1 - x}

Mg

_{x}

SnS

_{4}

(CZ-MTS). The semiconductor was prepared by the hot injection method, using oleylamine (OLA) as both surfactant and solvent. The presence and concentration of incorporated Mg allowed the fine-tuning of the CZ-MTS semiconductor’s structural and optical properties. Furthermore, it was observed that the inclusion of Mg in the CZTS structure leads to a better embodiment ratio of the Zn during the synthesis, thus reducing the excess of starting precursors. In summary, CZ-MTS is a promising candidate to fabricate high efficient and cost-effective thin-film solar cells made of earth-abundant elements. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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15 pages, 4232 KiB

Open AccessArticle

Novel Pb(II) Complexes: X-Ray Structures, Hirshfeld Surface Analysis and DFT Calculations

by Ghodrat Mahmoudi, Saikat Kumar Seth, Antonio Bauza Riera, Fedor Ivanovich Zubkov and Antonio Frontera

Crystals 2020, 10(7), 568; https://doi.org/10.3390/cryst10070568 - 2 Jul 2020

Cited by 10 | Viewed by 2595

Abstract

Herein we report the synthesis and detailed structural characterization of two new centrosymmetric dinuclear coordination compounds of Pb(II) [Pb₂L₂(NCS)₄] (1) and [Pb₂L₂(NO₃)₄]∙2MeOH (2), using the [...] Read more.

Herein we report the synthesis and detailed structural characterization of two new centrosymmetric dinuclear coordination compounds of Pb(II) [Pb₂L₂(NCS)₄] (1) and [Pb₂L₂(NO₃)₄]∙2MeOH (2), using the organic ligand 1,2-diphenyl-1,2-bis((methyl(pyridin-2-yl)methylene)hydrazono)ethane (L). In both complexes, each subunit [PbLX₂ (X = NO₃ or NCS)] adopts a quasi-aromatic Möbius metal chelate structure. Each ligand L is coordinated in a tetradentate coordination mode to Pb(II), yielding the 12π electron chelate ring via two pyridyl-imine units. In compound (1), the coordination sphere is completed by one disordered N,S-coordinated thiocyanate anion and two μ_1,1-bridging N-coordinated thiocyanate anions. In compound (2), the coordination sphere of Pb(II) is completed by two monodentate and two bidentate nitrato ligands (two of them acting as bridging ligands). Crystal packing of both compounds is stabilized by intermolecular hydrogen bonds, intra- and intermolecular C–H∙∙∙π interactions. The Hirshfeld molecular surfaces of (1) and (2) demonstrate that their packing is dominated by C–H∙∙∙O/N/S interactions as well as by far less favored H∙∙∙H contacts. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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12 pages, 7840 KiB

Open AccessArticle

Water Structures and Packing Efficiency in Methylene Blue Cyanometallate Salts

by Stefano Canossa, Claudia Graiff, Domenico Crocco and Giovanni Predieri

Crystals 2020, 10(7), 558; https://doi.org/10.3390/cryst10070558 - 1 Jul 2020

Cited by 5 | Viewed by 3358

Abstract

Crystal structure prediction is the holy grail of crystal engineering and is key to its ambition of driving the formation of solids based on the selection of their molecular constituents. However, this noble quest is hampered by the limited predictability of the incorporation [...] Read more.

Crystal structure prediction is the holy grail of crystal engineering and is key to its ambition of driving the formation of solids based on the selection of their molecular constituents. However, this noble quest is hampered by the limited predictability of the incorporation of solvent molecules, first and foremost the ubiquitous water. In this context, we herein report the structure of four methylene blue cyanometallate phases, where anions with various shapes and charges influence the packing motif and lead to the formation of differently hydrated structures. Importantly, water molecules are observed to play various roles as isolated fillings, dimers, or an infinite network with up to 13 water molecules per repeating unit. Each crystal structure has been determined by single-crystal X-ray diffraction and evaluated with the aid of Hirshfeld surface analysis, focussing on the role of water molecules and the hierarchy of different classes of interactions in the overall supramolecular landscape of the crystals. Finally, the collected pieces of evidence are matched together to highlight the leading role of MB stacking and to derive an explanation for the observed hydration diversity based on the structural role of water molecules in the crystal architecture. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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7 pages, 2160 KiB

Open AccessArticle

Unexpected Selective Gas Adsorption on a ‘Non-Porous’ Metal Organic Framework

by Stuart Beveridge, Craig A. McAnally, Gary S. Nichol, Alan R. Kennedy, Edmund J. Cussen and Ashleigh J. Fletcher

Crystals 2020, 10(6), 548; https://doi.org/10.3390/cryst10060548 - 26 Jun 2020

Cited by 2 | Viewed by 2696

Abstract

A metal organic framework Cu(tpt)BF₄·¾H₂O was synthesized as a potential carbon capture material, with the aim being to exploit the Lewis base interaction of the incorporated ligand functionalities with acidic gas. The material displays high thermal stability but an [...] Read more.

A metal organic framework Cu(tpt)BF₄·¾H₂O was synthesized as a potential carbon capture material, with the aim being to exploit the Lewis base interaction of the incorporated ligand functionalities with acidic gas. The material displays high thermal stability but an exceptionally low surface area; however, this contrasts starkly with its ability to capture carbon dioxide, demonstrating significant activated diffusion within the framework. The full characterization of the material shows a robust structure, where the CO₂ sorption is 120% greater than current industrial methods using liquid amine solutions; the thermal energy required for sorbent regeneration is reduced by 65%, indicating the true industrial potential of the synthesized material. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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28 pages, 7336 KiB

Open AccessArticle

Properties of Fourier Syntheses and New Syntheses

by Maria Cristina Burla, Benedetta Carrozzini, Giovanni Luca Cascarano, Carmelo Giacovazzo and Giampiero Polidori

Crystals 2020, 10(6), 538; https://doi.org/10.3390/cryst10060538 - 24 Jun 2020

Cited by 1 | Viewed by 2208

Abstract

In this study, the properties of observed, difference, and hybrid syntheses (hybrid indicates a combination of observed and difference syntheses) are investigated from two points of view. The first has a statistical nature and aims to estimate the amplitudes of peaks corresponding to [...] Read more.

In this study, the properties of observed, difference, and hybrid syntheses (hybrid indicates a combination of observed and difference syntheses) are investigated from two points of view. The first has a statistical nature and aims to estimate the amplitudes of peaks corresponding to the model atoms, belonging or not belonging to the target structure; the amplitudes of peaks related to the target atoms, missed or shared with the model; and finally, the quality of the background. The latter point deals with the practical features of Fourier syntheses, the special role of weighted syntheses, and their usefulness in practical applications. It is shown how the properties of the various syntheses may vary according to the available structural model and, in particular, how weighted hybrid syntheses may act like an observed and difference or a full hybrid synthesis. The theoretical results obtained in this paper suggest new Fourier syntheses using novel Fourier coefficients: their main features are first discussed from a mathematical point of view. Extended experimental applications show that they meet the basic mission of the Fourier syntheses, enhancing peaks corresponding to the missed target atoms, depleting peaks corresponding to the model atoms not belonging to the target, and significantly reducing the background. A comparison with the results obtained via the most popular modern Fourier syntheses is made, suggesting a role for the new syntheses in modern procedures for phase extension and refinement. The most promising new Fourier synthesis has been implemented in the current version of SIR2014. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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14 pages, 1795 KiB

Open AccessArticle

Analysis of the Phase Stability of LiMO₂ Layered Oxides (M = Co, Mn, Ni)

by Mariarosaria Tuccillo, Oriele Palumbo, Michele Pavone, Ana Belen Muñoz-García, Annalisa Paolone and Sergio Brutti

Crystals 2020, 10(6), 526; https://doi.org/10.3390/cryst10060526 - 20 Jun 2020

Cited by 26 | Viewed by 5281

Abstract

Transition-metal (TM) layered oxides have been attracting enormous interests in recent decades because of their excellent functional properties as positive electrode materials in lithium-ion batteries. In particular LiCoO₂ (LCO), LiNiO₂ (LNO) and LiMnO₂ (LMO) are the structural prototypes of a [...] Read more.

Transition-metal (TM) layered oxides have been attracting enormous interests in recent decades because of their excellent functional properties as positive electrode materials in lithium-ion batteries. In particular LiCoO₂ (LCO), LiNiO₂ (LNO) and LiMnO₂ (LMO) are the structural prototypes of a large family of complex compounds with similar layered structures incorporating mixtures of transition metals. Here, we present a comparative study on the phase stability of LCO, LMO and LNO by means of first-principles calculations, considering three different lattices for all oxides, i.e., rhombohedral (hR12), monoclinic (mC8) and orthorhombic (oP8). We provide a detailed analysis—at the same level of theory—on geometry, electronic and magnetic structures for all the three systems in their competitive structural arrangements. In particular, we report the thermodynamics of formation for all ground state and metastable phases of the three compounds for the first time. The final Gibbs Energy of Formation values at 298 K from elements are: LCO(hR12) −672 ± 8 kJ mol⁻¹; LCO(mC8) −655 ± 8 kJ mol⁻¹; LCO(oP8) −607 ± 8 kJ mol⁻¹; LNO(hR12) −548 ± 8 kJ mol⁻¹; LNO(mC8) −557 ± 8 kJ mol⁻¹; LNO(oP8) −548 ± 8 kJ mol⁻¹; LMO(hR12) −765 ± 10 kJ mol⁻¹; LMO(mC8) −779 ± 10 kJ mol⁻¹; LMO(oP8) −780 ± 10 kJ mol⁻¹. These values are of fundamental importance for the implementation of reliable multi-phase thermodynamic modelling of complex multi-TM layered oxide systems and for the understanding of thermodynamically driven structural phase degradations in real applications such as lithium-ion batteries. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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43 pages, 17502 KiB

Open AccessArticle

Understanding the Antipathogenic Performance of Nanostructured and Conventional Copper Cold Spray Material Consolidations and Coated Surfaces

by Bryer C. Sousa, Kristin L. Sundberg, Matthew A. Gleason and Danielle L. Cote

Crystals 2020, 10(6), 504; https://doi.org/10.3390/cryst10060504 - 12 Jun 2020

Cited by 15 | Viewed by 5045

Abstract

The role of high strain rate and severe plastic deformation, microstructure, electrochemical behavior, surface chemistry and surface roughness were characterized for two copper cold spray material consolidations, which were produced from conventionally gas-atomized copper powder as well as spray-dried copper feedstock, during the [...] Read more.

The role of high strain rate and severe plastic deformation, microstructure, electrochemical behavior, surface chemistry and surface roughness were characterized for two copper cold spray material consolidations, which were produced from conventionally gas-atomized copper powder as well as spray-dried copper feedstock, during the course of this work. The motivation underpinning this work centers upon the development of a more robust understanding of the microstructural features and properties of the conventional copper and nanostructured copper coatings as they relate to antipathogenic contact killing and inactivation applications. Prior work has demonstrated greater antipathogenic efficacy with respect to the nanostructured coating versus the conventional coating. Thus, microstructural analysis was performed in order to establish differences between the two coatings that their respective pathogen kill rates could be attributed to. Results from advanced laser-induced projectile impact testing, X-ray diffraction, scanning electron microscopy, electron backscatter diffraction, scanning transmission microscopy, nanoindentation, energy-dispersive X-ray spectroscopy, nanoindentation, confocal microscopy, atomic force microscopy, linear polarization, X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy and copper ion release assaying were performed during the course of this research. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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17 pages, 8392 KiB

Open AccessArticle

Coordination Compounds Featuring Non-Toxic Chiral 1,4-Dicarboxylic Acids and Copper(II)

by Marius Kremer, Jan van Leusen and Ulli Englert

Crystals 2020, 10(6), 485; https://doi.org/10.3390/cryst10060485 - 6 Jun 2020

Viewed by 2880

Abstract

Six new coordination compounds of copper cations and 1,4-dicarboxylic acids have been synthesized and structurally investigated. Aspartic acid (H₂asp), enantiopure, racemic and meso tartaric acid (H₂tart), di-para-toluyltartaric acid (H₂dptta) and dibenzoyltartaric acid (H₂dbta) [...] Read more.

Six new coordination compounds of copper cations and 1,4-dicarboxylic acids have been synthesized and structurally investigated. Aspartic acid (H₂asp), enantiopure, racemic and meso tartaric acid (H₂tart), di-para-toluyltartaric acid (H₂dptta) and dibenzoyltartaric acid (H₂dbta) represent environmentally benign water-soluble proligands which may be deprotonated for oxygen coordination. Chelating ligands such as tetramethylethylenediamine (TMEDA) and 2-aminomethylpyridine (AMPY) efficiently reduce the dimensionality of the target compounds, and additional aqua ligands complete the coordination environments. In this line of argument, the discrete mononuclear complexes [Cu(AMPY)(asp)(H₂O)] and [Cu(Hdbta)₂(H₂O)₄] were obtained; for the latter, only a preliminary structure model can be presented which, however, agrees with the powder diffraction pattern of the bulk. From enantiopure and racemic tartaric acid and TMEDA the closely related chain polymers [Cu^II(H₂tart)(TMEDA)(H₂O)₂)]_n were obtained; the racemic compound consists of individual homochiral strands of opposite chirality. The high steric demand of di-para-toluyltartaric acid leads to one-dimensional [Cu(dptta)(EtOH)(H₂O)₂]_n with coordinated ethanol (EtOH) in the distant Jahn–Teller site of the coordination sphere. Cu(II), meso-tartaric acid and TMEDA aggregate to a trinuclear coordination compound [Cu^II₂Cu^I(H₂tart)(Htart)(TMEDA)₂]. Its peripheral cations show the expected Jahn–Teller geometry of Cu(II), but the unambiguous assignment of the oxidation state +I for central cation required susceptibility measurements: their results prove the presence of only two and only very weakly interacting divalent cations, separated by a diamagnetic center. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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15 pages, 2415 KiB

Open AccessArticle

Synthesis, Characterization and Biological Studies of Ether–Based Ferrocenyl Amides and their Organic Analogues

by Sana Waseem Abbasi, Naveed Zafar Ali, Martin Etter, Muhammad Shabbir, Zareen Akhter, Stacey J. Smith, Hammad Ismail and Bushra Mirza

Crystals 2020, 10(6), 480; https://doi.org/10.3390/cryst10060480 - 4 Jun 2020

Viewed by 2605

Abstract

Ferrocenyl amides (FB1-FB13) and their organic analogues (BZ1-BZ13) were prepared by a low-temperature condensation method. Ferrocenyl amides were synthesised using 4-ferrocenylbenzoyl chloride and ether-based amines and diamines. Benzoyl chloride was used to synthesise organic analogues by reacting with various amines. The synthesised compounds [...] Read more.

Ferrocenyl amides (FB1-FB13) and their organic analogues (BZ1-BZ13) were prepared by a low-temperature condensation method. Ferrocenyl amides were synthesised using 4-ferrocenylbenzoyl chloride and ether-based amines and diamines. Benzoyl chloride was used to synthesise organic analogues by reacting with various amines. The synthesised compounds were characterised by elemental, spectroscopic (FT-IR and NMR) and single crystal X-ray diffraction methods. Crystal structures of the representative organic analogues (BZ2 and BZ6) were solved by single crystal X-ray diffraction. BZ2 crystallises in the triclinic space group P

\bar{1}

with a unit cell volume of V = 1056.6(3) Å³ and with two formula units per unit cell. Whereas BZ6 assembles in the orthorhombic space group Pbca with four formula units per unit cell and a unit cell volume of V = 1354.7(2) Å³. Spectral studies confirmed the presence of amide linkages in the synthesised compound with a strong N—H·····O=C hydrogen bonding network established between amide groups of neighbouring molecular scaffolds further stabilising the molecular stacking in accordance with the archetypal crystal structures. The bioactive nature of each compound was assessed by DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical scavenging activity, hydrogen peroxide scavenging activity and total antioxidant activity. Antidiabetic, anticholinesterase enzyme inhibition tests, as well as antibacterial activities, were performed showing significant biological activity for ferrocenyl amides as compared to their organic analogues. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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14 pages, 2978 KiB

Open AccessArticle

Tris(ethylenediamine) Cobalt(II) and Manganese(II) Nitrates

by Miguel Cortijo, Ángela Valentín-Pérez, Mathieu Rouzières, Rodolphe Clérac, Patrick Rosa and Elizabeth A. Hillard

Crystals 2020, 10(6), 472; https://doi.org/10.3390/cryst10060472 - 3 Jun 2020

Cited by 6 | Viewed by 5799

Abstract

Octahedral tris(ethylenediamine) coordination complexes demonstrate helicoidal chirality, due to the arrangement of the ligands around the metal core. The enantiomers of the nitrate salts [Ni(en)₃](NO₃)₂ and [Zn(en)₃](NO₃)₂ spontaneously resolve to form a mixture [...] Read more.

Octahedral tris(ethylenediamine) coordination complexes demonstrate helicoidal chirality, due to the arrangement of the ligands around the metal core. The enantiomers of the nitrate salts [Ni(en)₃](NO₃)₂ and [Zn(en)₃](NO₃)₂ spontaneously resolve to form a mixture of conglomerate crystals, which present a reversible phase transition from space group P6₃22 to enantiomorphic P6₅22 or P6₁22, with the latter depending on the handedness of the enantiomer. We report here the synthesis and characterization of [Mn(en)₃](NO₃)₂ and [Co(en)₃](NO₃)₂, which are isostructural to the Zn(II) and Ni(II) derivatives. The Mn(II) analogue undergoes the same phase transition centered at 150(2) K, as determined by single-crystal X-ray diffraction, Raman spectroscopy, and differential scanning calorimetry. The Co(II) derivative does not demonstrate a phase transition down to 2 K, as evidenced by powder X-ray diffraction and heat capacity measurements. The phase transition does not impact the magnetic properties of the Ni(II) and Mn(II) analogues; these high spin compounds display Curie behavior that is consistent with S = 1 and 5/2, respectively, down to 20 K, while the temperature-dependent magnetic moment for the Co(II) compound reveals a significant orbital contribution. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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21 pages, 21731 KiB

Open AccessArticle

Mineral Vesicles and Chemical Gardens from Carbonate-Rich Alkaline Brines of Lake Magadi, Kenya

by Melese Getenet, Juan Manuel García-Ruiz, Cristóbal Verdugo-Escamilla and Isabel Guerra-Tschuschke

Crystals 2020, 10(6), 467; https://doi.org/10.3390/cryst10060467 - 1 Jun 2020

Cited by 11 | Viewed by 4328

Abstract

Mineral vesicles and chemical gardens are self-organized biomimetic structures that form via abiotic mineral precipitation. These membranous structures are known to catalyze prebiotic reactions but the extreme conditions required for their synthesis has cast doubts on their formation in nature. Apart from model [...] Read more.

Mineral vesicles and chemical gardens are self-organized biomimetic structures that form via abiotic mineral precipitation. These membranous structures are known to catalyze prebiotic reactions but the extreme conditions required for their synthesis has cast doubts on their formation in nature. Apart from model solutions, these structures have been shown to form in serpentinization-driven natural silica-rich water and by fluid-rock interaction of model alkaline solutions with granites. Here, for the first time, we demonstrate that self-assembled hollow mineral vesicles and gardens can be synthesized in natural carbonate-rich soda lake water. We have synthesized these structures by a) pouring saturated metal salt solutions, and b) by immersing metal salt pellets in brines collected from Lake Magadi (Kenya). The resulting structures are analyzed by using SEM coupled with EDX analysis, Raman spectroscopy, and powder X-ray diffraction. Our results suggest that mineral self-assembly could have been a common phenomenon in soda oceans of early Earth and Earth-like planets and moons. The composition of the obtained vesicles and gardens confirms the recent observation that carbonate minerals in soda lakes sequestrate Ca, thus leaving phosphate behind in solution available for biochemical reactions. Our results strengthens the proposal that alkaline brines could be ideal sites for “one-pot” synthesis of prebiotic organic compounds and the origin of life. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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13 pages, 2671 KiB

Open AccessArticle

Towards an Understanding of Crystallization by Attachment

by Haihua Pan and Ruikang Tang

Crystals 2020, 10(6), 463; https://doi.org/10.3390/cryst10060463 - 1 Jun 2020

Cited by 3 | Viewed by 3174

Abstract

Crystallization via particle attachment was used in a unified model for both classical and non-classical crystallization pathways, which have been widely observed in biomimetic mineralization and geological fields. However, much remains unknown about the detailed processes and driving mechanisms for the attachment. Here, [...] Read more.

Crystallization via particle attachment was used in a unified model for both classical and non-classical crystallization pathways, which have been widely observed in biomimetic mineralization and geological fields. However, much remains unknown about the detailed processes and driving mechanisms for the attachment. Here, we take calcite crystal as a model mineral to investigate the detailed attachment process using in situ Atomic Force Microscopy (AFM) force measurements and molecular dynamics simulations. The results show that hydration layers hinder the attachment; however, in supersaturated solutions, ionic bridges are formed between crystal gaps as a result of capillary condensation, which might enhance the aggregation of calcite crystals. These findings provide a more detailed understanding of the crystal attachment, which is of vital importance for a better understanding of mineral formation under biological and geological environments with a wide range of chemical and physical conditions. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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7 pages, 270 KiB

Open AccessArticle

A Simple Method for Photoconductivity Measurement in Lithium Niobate

by Marco Bazzan, Laurent Guilbert and Michel Aillerie

Crystals 2020, 10(6), 461; https://doi.org/10.3390/cryst10060461 - 1 Jun 2020

Viewed by 1969

Abstract

A simple and effective technique to characterize the photoconductivity (PC) of lithium niobate is presented. The technique is based on the modulation of the external field and on the observation of the optical response of the material as a function of the intensity [...] Read more.

A simple and effective technique to characterize the photoconductivity (PC) of lithium niobate is presented. The technique is based on the modulation of the external field and on the observation of the optical response of the material as a function of the intensity of a gaussian beam using a Tardy’s polarimetric setup in the

r_{22}

configuration. When the temporal period of the modulation is larger than the Maxwell time of the material, the effect of the PC can be detected observing the kinetics of the screening effect of the external applied field. This approach allows measuring a wide dynamic range up to high light intensities with good accuracy using a standard oscilloscope and with no need for charge collection electrodes. The technique is demonstrated by comparing two samples, the first possessing a standard congruent composition, the second being doped with Zn in order to boost the PC. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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13 pages, 2675 KiB

Open AccessArticle

Hydrogen Bonds with BF₄⁻ Anion as a Proton Acceptor

by Sławomir J. Grabowski

Crystals 2020, 10(6), 460; https://doi.org/10.3390/cryst10060460 - 1 Jun 2020

Cited by 26 | Viewed by 4767

Abstract

The BF₄⁻ anion is characterised by weak Lewis base properties; it is usually classified as a “non-coordinating anion”. The searches through the Cambridge Structural Database (CSD) were performed and it was found that the BF₄⁻ anion often occurs in [...] Read more.

The BF₄⁻ anion is characterised by weak Lewis base properties; it is usually classified as a “non-coordinating anion”. The searches through the Cambridge Structural Database (CSD) were performed and it was found that the BF₄⁻ anion often occurs in crystal structures and it is involved in numerous intermolecular interactions; hydrogen bonds are the majority of them. The hydrogen bonds involving the BF₄⁻ anion as a proton acceptor are closer to linearity with the increase of the strength of interaction that is in line with the tendency known for other hydrogen bonds. However, even for short contacts between the proton and the Lewis base centre, slight deviations from linearity occur. The MP2/aug-cc-pVTZ calculations on the BF₄⁻…HCN complex and on the BF₄⁻…(HCN)₄ cluster were also carried out to characterise corresponding C-H…F hydrogen bonds; such interactions often occur in crystal structures. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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16 pages, 5277 KiB

Open AccessArticle

Effect of Chitosan Electrospun Fiber Mesh as Template on the Crystallization of Calcium Oxalate

by Nicole Butto, Nicole Cotrina Vera, Felipe Díaz-Soler, Mehrdad Yazdani-Pedram and Andrónico Neira-Carrillo

Crystals 2020, 10(6), 453; https://doi.org/10.3390/cryst10060453 - 31 May 2020

Cited by 8 | Viewed by 2543

Abstract

Biominerals fulfill various physiological functions in living organisms, however, pathological mineralization can also occur generating mineral pathologies such as the formation of calcium oxalate (CaOx) calculi in the urinary tract. Inspired by the ability of living organisms to generate biogenic minerals using biological [...] Read more.

Biominerals fulfill various physiological functions in living organisms, however, pathological mineralization can also occur generating mineral pathologies such as the formation of calcium oxalate (CaOx) calculi in the urinary tract. Inspired by the ability of living organisms to generate biogenic minerals using biological organic matrices, and the need to understand the mechanisms of crystallization, three-dimensional fibrillary meshes based on chitosan fibers with random and controlled topology by electrospinning were manufactured. Chitosan was selected due to its active role on in vitro crystallization and its physicochemical properties, which allows the exposure of their functional chemical groups that could selectively stabilize hydrated crystalline forms of CaOx. CaOx crystals were generated on conductive tin indium oxide (ITO) glass substrates modified with electrospun chitosan fibers by using electrocrystallization (EC) technique. The chitosan fibers and the resulting CaOx crystals were analyzed by optical microscopy (OM), scanning electron microscopy (SEM), and X-ray diffraction (XRD) techniques, which demonstrated that the chemical nature and topology of the three-dimensional fibers used as organic template are key factors in the control of type, morphology, and crystallographic orientation of CaOx. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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10 pages, 1826 KiB

Open AccessArticle

Ultrahigh Electromechanical Coupling and Its Thermal Stability in (Na_1/2Bi_1/2)TiO₃-Based Lead-Free Single Crystals

by Chao Chen, Li Yang, Xingan Jiang, Xiaokun Huang, Xiaoyi Gao, Na Tu, Kaizheng Shu, Xiangping Jiang, Shujun Zhang and Haosu Luo

Crystals 2020, 10(6), 435; https://doi.org/10.3390/cryst10060435 - 29 May 2020

Cited by 6 | Viewed by 2164

Abstract

In this work, we report the ultrahigh electromechanical coupling performance of NBT-6BT-KNN lead-free single crystal at room temperature. The thickness mode electromechanical coupling coefficient (k_t) and the 31 mode electromechanical coupling coefficient (k₃₁) reach 69.0% and 45.7%, [...] Read more.

In this work, we report the ultrahigh electromechanical coupling performance of NBT-6BT-KNN lead-free single crystal at room temperature. The thickness mode electromechanical coupling coefficient (k_t) and the 31 mode electromechanical coupling coefficient (k₃₁) reach 69.0% and 45.7%, respectively, which are superior to the PZT-5H lead-based ceramics of k_t~60% and k₃₁~39%. In addition, the evolution of the crystal structure and domain morphology is revealed by Raman scattering spectra, a polarizing microscope and piezoelectric force microscopy characterization. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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12 pages, 2909 KiB

Open AccessArticle

Origin of Structural Change Driven by A-Site Lanthanide Doping in ABO₃-Type Perovskite Ferroelectrics

by Lan Xu, Zujian Wang, Bin Su, Chenxi Wang, Xiaoming Yang, Rongbing Su, Xifa Long and Chao He

Crystals 2020, 10(6), 434; https://doi.org/10.3390/cryst10060434 - 29 May 2020

Cited by 15 | Viewed by 3057

Abstract

Lanthanide doping is widely employed to tune structural change temperature and electrical properties in ABO₃-type perovskite ferroelectric materials. However, the reason that A-site lanthanide doping leads to the decrease of the Curie temperature is still not clear. Based on the reported [...] Read more.

Lanthanide doping is widely employed to tune structural change temperature and electrical properties in ABO₃-type perovskite ferroelectric materials. However, the reason that A-site lanthanide doping leads to the decrease of the Curie temperature is still not clear. Based on the reported Curie temperature of lanthanides (Ln) doped in two classic ferroelectrics PbTiO₃ and BaTiO₃ with A²⁺B⁴⁺O₃-type perovskite structure, we discussed the relationship between the decrease rate of Curie temperature (ΔT_C) and the bond strength variance of A-site cation (σ). For Nd ion doped Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (Nd-PMNT) ferroelectric crystal as an example, the internal factors of the dramatic decline of the Curie temperature induced by A-site Nd doping were investigated under a systematic study. The strong covalent bonds of Ln-O play an important role in A-site Ln composition-induced structural change from ferroelectric to paraelectric phase, and it is responsible for the significant decrease in the Curie temperature. It is proposed that the cells become cubic around the Ln ions due to the strong covalent energy of Ln-O bonding in A-site Ln doped A²⁺B⁴⁺O₃ perovskite ferroelectrics. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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12 pages, 3618 KiB

Open AccessArticle

The Effect of Printing Parameters on Electrical Conductivity and Mechanical Properties of PLA and ABS Based Carbon Composites in Additive Manufacturing of Upper Limb Prosthetics

by Attila Pentek, Miklos Nyitrai, Adam Schiffer, Hajnalka Abraham, Matyas Bene, Emese Molnar, Roland Told and Peter Maroti

Crystals 2020, 10(5), 398; https://doi.org/10.3390/cryst10050398 - 15 May 2020

Cited by 21 | Viewed by 4518

Abstract

Additive manufacturing technologies are dynamically developing, strongly affecting almost all fields of industry and medicine. The appearance of electrically conductive polymers has had a great impact on the prototyping process of different electrical components in the case of upper limb prosthetic development. The [...] Read more.

Additive manufacturing technologies are dynamically developing, strongly affecting almost all fields of industry and medicine. The appearance of electrically conductive polymers has had a great impact on the prototyping process of different electrical components in the case of upper limb prosthetic development. The widely used FFF 3D printing technology mainly uses PLA (polylactic acid) and ABS (acrylonitrile butadiene styrene) based composites, and despite their presence in the field, a detailed, critical characterization and comparison of them has not been performed yet. Our aim was to characterize two PLA and ABS based carbon composites in terms of electrical and mechanical behavior, and extend the observations with a structural and signal transfer analysis. The measurements were carried out by changing the different printing parameters, including layer resolution, printing orientation and infill density. To determine the mechanical properties, static and dynamic tests were conducted. The electrical characterization was done by measuring the resistance and signal transfer characteristics. Scanning electron microscopy was used for the structural analysis. The results proved that the printing parameters had a significant effect on the mechanical and electrical characteristics of both materials. As a major novelty, it was concluded that the ABS carbon composite has more favorable behavior in the case of additive manufacturing of electrical components of upper limb prosthetics, and they can be used as moving, rotating parts as well. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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12 pages, 2757 KiB

Open AccessArticle

Microstructure and Mechanical Properties of an Austenitic CrMnNiMoN Spring Steel Strip with a Reduced Ni Content

by Christina Schröder, Marco Wendler, Olena Volkova and Andreas Weiß

Crystals 2020, 10(5), 392; https://doi.org/10.3390/cryst10050392 - 12 May 2020

Cited by 3 | Viewed by 2931

Abstract

The article presents the mechanical properties of the austenitic stainless steel X5CrMnNiMoN16-4-4 after deformation by cold rolling and subsequent short-term tempering (deformation and partitioning (D&P) treatment). Tensile strengths of 1700–900 MPa and beyond were achieved both after work hardening and in the D&P-treated [...] Read more.

The article presents the mechanical properties of the austenitic stainless steel X5CrMnNiMoN16-4-4 after deformation by cold rolling and subsequent short-term tempering (deformation and partitioning (D&P) treatment). Tensile strengths of 1700–900 MPa and beyond were achieved both after work hardening and in the D&P-treated strip. The initial state of austenite in terms of grain size and pre-strengthening, as well as the selected cold rolling temperature significantly influenced the deformation-induced formation of α’ martensite and thus the flow and hardening behavior of the steel. The usage of two different rolling temperature regimes showed that the strength properties in the cold strip can be specifically adjusted. Lower deformation-induced martensite fractions enabled a larger thickness reduction of the strip without increasing the rolling force, while high deformation-induced martensite fractions led to strong hardening at low deformation levels. The D&P-treatment permits the strength of the cold-rolled strip with a predominantly austenitic microstructure to be increased to the required level. The total elongation of such a D&P strip was well over 2%. The D&P treatment of the spring steel strip is a cost-effective alternative to conventional tempering treatment. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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16 pages, 3563 KiB

Open AccessArticle

Novel Cd (II) Coordination Polymers Afforded with EDTA or Trans-1,2-Cdta Chelators and Imidazole, Adenine, or 9-(2-Hydroxyethyl) Adenine Coligands

by Jeannette Carolina Belmont-Sánchez, María Eugenia García-Rubiño, Antonio Frontera, Antonio Matilla-Hernández, Alfonso Castiñeiras and Juan Niclós-Gutiérrez

Crystals 2020, 10(5), 391; https://doi.org/10.3390/cryst10050391 - 11 May 2020

Cited by 3 | Viewed by 2659

Abstract

Three mixed-ligands of Cd(II) coordination polymers were unintentionally obtained: {[Cd(µ₃-EDTA)(Him)·Cd(Him)(H₂O)₂]·H₂O}_n (1), {[Cd(µ₄-CDTA)(Hade)·Cd(Hade)₂]}_n (2), and {[Cd(µ₃-EDTA)(H₂O)·Cd(H9heade)(H₂O)]·2H₂O}_n ( [...] Read more.

Three mixed-ligands of Cd(II) coordination polymers were unintentionally obtained: {[Cd(µ₃-EDTA)(Him)·Cd(Him)(H₂O)₂]·H₂O}_n (1), {[Cd(µ₄-CDTA)(Hade)·Cd(Hade)₂]}_n (2), and {[Cd(µ₃-EDTA)(H₂O)·Cd(H9heade)(H₂O)]·2H₂O}_n (3), having imidazole (Him), adenine (Hade) or 9-(2-hydroxyethyl)adenine (9heade) as the N-heterocyclic coligands. Compounds 2 and 3 were obtained by working with an excess of corresponding N-heterocyclic coligands. The single-crystal X-ray diffraction structures and thermogravimetric analyses are reported. The chelate moieties in all three compounds exhibit hepta-coordinated Cd centers, whereas the non-chelated Cd center is five-coordinated in 1 and six-coordinated in 2 and 3. Him and Hade take part in the seven-coordinated chelate moieties in 1 and 2, respectively. In contrast, 9heade is unable to replace the aqua ligand of the chelate [Cd (EDTA) (H₂O)] moiety in 3. The thermogravimetric analysis (TGA) behavior of [Cd (H₂EDTA) (H₂O)]·2H₂O in 1 and 3 leads to a residue of CdO, whereas the N-rich compound 2 yields CdO·Cd(NO₃)₂ as a residue. Density functional theory (DFT) calculations along with molecular electrostatic potential (MEP) and quantum theory of atoms-in-molecules computations were performed in adenine (compound 2) and (2-hydroxyethyl)adenine (compound 3) to analyze how the strength of the H-bonding and π-stacking interactions, respectively, are affected by their coordination to the Cd-metal center. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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14 pages, 2940 KiB

Open AccessArticle

Formation of Nanoclusters in Gold Nucleation

by Cornelia M. Schneider and Helmut Cölfen

Crystals 2020, 10(5), 382; https://doi.org/10.3390/cryst10050382 - 8 May 2020

Cited by 6 | Viewed by 3553

Abstract

Gold nanoclusters consisting of a specific atom number have gained popularity in research in recent years due to their outstanding properties. Due to their molecule-like behavior, their properties depend strongly on their size. Although they represent the link species between atoms and nanoparticles [...] Read more.

Gold nanoclusters consisting of a specific atom number have gained popularity in research in recent years due to their outstanding properties. Due to their molecule-like behavior, their properties depend strongly on their size. Although they represent the link species between atoms and nanoparticles and are the subject of current research, a high-resolution characterization is still missing. Here, we used the band forming experiment in analytical ultracentrifugation (AUC) to characterize the gold nanoclusters in the moment of their generation using thioglycerol as a stabilizer. The concentration variation of the gold precursor, reducing agent, and stabilizer was investigated. The formation of different cluster species from the smallest Au₄ up to Au₉₁₁ could be observed. Very stable clusters of Au₅₅ appear in every experiment and other cluster sizes more rarely. The extracted UV/Vis spectra could additionally be correlated to every cluster. The variation in the concentration of sodium borohydride and the stabilizer did not lead to a clear trend, but the gold ion concentration directed the size of the formed clusters. A decrease seemed to promote the generation of a higher abundance of smaller clusters accompanied by less big clusters, and vice versa. These results present the characterization of the different nanocluster generations directly in the formation process of nanoparticles and therefore are a contribution to the understanding of their formation. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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10 pages, 4461 KiB

Open AccessArticle

Impact of Phase Structure on Piezoelectric Properties of Textured Lead-Free Ceramics

by Xiaoyi Gao, Nannan Dong, Fangquan Xia, Qinghu Guo, Hua Hao, Hanxing Liu and Shujun Zhang

Crystals 2020, 10(5), 367; https://doi.org/10.3390/cryst10050367 - 3 May 2020

Cited by 11 | Viewed by 3263

Abstract

The impact of phase structure on piezoelectric performances of <001> textured Na_0.5Bi_0.5TiO₃ (NBT) based lead-free ceramics was studied, including 0.88NBT-0.08K_0.5Bi_0.5TiO₃-0.04BaTiO₃ (88NBT) with morphotropic phase boundary (MPB) composition and 0.90NBT-0.07K_0.5Bi [...] Read more.

The impact of phase structure on piezoelectric performances of <001> textured Na_0.5Bi_0.5TiO₃ (NBT) based lead-free ceramics was studied, including 0.88NBT-0.08K_0.5Bi_0.5TiO₃-0.04BaTiO₃ (88NBT) with morphotropic phase boundary (MPB) composition and 0.90NBT-0.07K_0.5Bi_0.5TiO₃-0.03BaTiO₃ (90NBT) with rhombohedral phase. Both textured ceramics exhibit a high Lotgering factor, being on the order of f~96%. The piezoelectric coefficients of the textured 88NBT and 90NBT ceramics are increased by 20% and 60%, respectively, comparing to their randomly oriented ceramics. The piezoelectric enhancement of 90NBT textured ceramic is three times higher than 88NBT, revealing the phase structure plays a significant role in enhancing the piezoelectric performances of textured ceramics. Of particular significance is that the 90NBT textured ceramic exhibits almost hysteresis-free strain behavior. The enhanced piezoelectric property with minimal strain hysteresis is attributed to the <001> poled rhombohedral engineered domain configuration. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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14 pages, 2579 KiB

Open AccessArticle

Computational Investigation of the Folded and Unfolded Band Structure and Structural and Optical Properties of CsPb(I_1−xBr_x)₃ Perovskites

by Hamid M. Ghaithan, Zeyad A. Alahmed, Andreas Lyras, Saif M. H. Qaid and Abdullah S. Aldwayyan

Crystals 2020, 10(5), 342; https://doi.org/10.3390/cryst10050342 - 27 Apr 2020

Cited by 11 | Viewed by 4693

Abstract

The structural, electronic, and optical properties of inorganic CsPb(I_1−xBr_x)₃ compounds were investigated using the full-potential linear augmented-plane wave (FP-LAPW) scheme with a generalized gradient approximation (GGA). Perdew–Burke–Ernzerhof generalized gradient approximation (PBE-GGA) and modified Becke–Johnson GGA (mBJ-GGA) potentials were [...] Read more.

The structural, electronic, and optical properties of inorganic CsPb(I_1−xBr_x)₃ compounds were investigated using the full-potential linear augmented-plane wave (FP-LAPW) scheme with a generalized gradient approximation (GGA). Perdew–Burke–Ernzerhof generalized gradient approximation (PBE-GGA) and modified Becke–Johnson GGA (mBJ-GGA) potentials were used to study the electronic and optical properties. The band gaps calculated using the mBJ-GGA method gave the best agreement with experimentally reported values. CsPb(I_1−xBr_x)₃ compounds were wide and direct band gap semiconductors, with a band gap located at the M point. The spectral weight (SW) approach was used to unfold the band structure. By substituting iodide with bromide, an increase in the band gap energy (E_g) values of 0.30 and 0.55 eV, using PBE-GGA and mBJ-GGA potentials, respectively, was observed, whereas the optical property parameters, which were also investigated, demonstrated the reverse effect. The high absorption spectra in the ultraviolet−visible energy range demonstrated that CsPb(I_1−xBr_x)₃ perovskite could be used in optical and optoelectronic devices by partly replacing iodide with bromide. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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11 pages, 2475 KiB

Open AccessArticle

Optical and Thermoelectric Properties of Surface-Oxidation Sensitive Layered Zirconium Dichalcogenides ZrS_2−xSe_x (x = 0, 1, 2) Crystals Grown by Chemical Vapor Transport

by Thalita Maysha Herninda and Ching-Hwa Ho

Crystals 2020, 10(4), 327; https://doi.org/10.3390/cryst10040327 - 22 Apr 2020

Cited by 21 | Viewed by 3937

Abstract

In this work, structure, optical, and thermoelectric properties of layered ZrS_2−xSe_x single crystals with selenium composition of x = 0, 1, and 2 were examined. Single crystals of zirconium dichalcogenides layer compounds were grown by chemical vapor transport method using [...] Read more.

In this work, structure, optical, and thermoelectric properties of layered ZrS_2−xSe_x single crystals with selenium composition of x = 0, 1, and 2 were examined. Single crystals of zirconium dichalcogenides layer compounds were grown by chemical vapor transport method using I₂ as the transport agent. X-ray diffraction (XRD) and high-resolution transmission electron microscope (HRTEM) results indicated that ZrS_2−xSe_x (x = 0, 1, and 2) were crystalized in hexagonal CdI₂ structure with one-layer trigonal (1T) stacking type. X-ray photoelectron and energy dispersive X-ray measurements revealed oxidation sensitive behavior of the chalcogenides series. Transmittance and optical absorption showed an indirect optical gap of about 1.78 eV, 1.32 eV, and 1.12 eV for the ZrS_2−xSe_x with x = 0, 1, and 2, respectively. From the result of thermoelectric experiment, ZrSe₂ owns the highest figure-of merit (ZT) of ~0.085 among the surface-oxidized ZrS_2−xSe_x series layer crystals at 300 K. The ZT values of the ZrS_2−xSe_x (x = 0, 1, and 2) series also reveal increase with the increase of Se content owing to the increase of carrier concentration and mobility in the highly Se-incorporated zirconium dichalcogenides with surface states. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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12 pages, 4039 KiB

Open AccessArticle

Single-Crystal ³¹P and ⁷Li NMR of the Ionic Conductor LiH₂PO₄

by Otto E. O. Zeman, Viktoria Kainz and Thomas Bräuniger

Crystals 2020, 10(4), 302; https://doi.org/10.3390/cryst10040302 - 15 Apr 2020

Cited by 1 | Viewed by 3953

Abstract

The electronic surroundings of phosphorus and lithium atoms in the ionic conductor lithium dihydrogen phosphate (LDP) have been studied by single-crystal nuclear magnetic resonance (NMR) spectroscopy at room temperature. From orientation-dependent NMR spectra of a large homegrown LDP single crystal, the full ³¹ [...] Read more.

The electronic surroundings of phosphorus and lithium atoms in the ionic conductor lithium dihydrogen phosphate (LDP) have been studied by single-crystal nuclear magnetic resonance (NMR) spectroscopy at room temperature. From orientation-dependent NMR spectra of a large homegrown LDP single crystal, the full ³¹P chemical shift (CS) and ⁷Li quadrupole coupling (QC) tensor was determined, using a global fit over three rotation patterns. The resulting CS tensor is characterized by its three eigenvalues:

δ_{11}^{P A S} = (67.0 \pm 0.6)

ppm,

δ_{22}^{P A S} = (13.9 \pm 1.5)

ppm, and

δ_{33}^{P A S} = (- 78.7 \pm 0.9)

ppm. All eigenvalues have also been verified by magic-angle spinning NMR on a polycrystalline sample, using Herzfeld–Berger analysis of the rotational side band pattern. The resulting ⁷Li QC tensor is characterized by its quadrupolar coupling constant

χ = Q_{33}^{P A S} = (- 71 \pm 1)

kHz and the two eigenvalues

Q_{11}^{P A S} = (22.3 \pm 0.9)

kHz, and

Q_{22}^{P A S} = (48.4 \pm 0.8)

kHz. The initially unknown orientation of the mounted crystal, expressed by the orientation of the rotation axis in the orthorhombic crystal frame, was included in the global data fit as well, thus obtaining it from NMR data only. Full article

(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)

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