Crystals

Editorial

Jump to: Research, Review

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 4975

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

Jump to: Editorial, Review

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 14 | Viewed by 2827

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)

► Show Figures

Graphical abstract

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 2152

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)

► Show Figures

Graphical abstract

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 15 | Viewed by 6572

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)

► Show Figures

Figure 1

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 1963

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)

► Show Figures

Figure 1

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 6 | Viewed by 3296

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)

► Show Figures

Figure 1

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 1985

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)

► Show Figures

Figure 1

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 2533

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)

► Show Figures

Figure 1

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 15 | Viewed by 3967

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)

► Show Figures

Graphical abstract

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 29 | Viewed by 5193

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)

► Show Figures

Figure 1

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 2364

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)

► Show Figures

Graphical abstract

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 3328

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)

► Show Figures

Figure 1

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 3815

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)

► Show Figures

Figure 1

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 12 | Viewed by 3314

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)

► Show Figures

Graphical abstract

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 35 | Viewed by 4655

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)

► Show Figures

Figure 1

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 2328

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)

► Show Figures

Figure 1

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 3061

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)

► Show Figures

Figure 1

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 2066

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)

► Show Figures

Graphical abstract

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 4171

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)

► Show Figures

Graphical abstract

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 3470

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)

► Show Figures

Graphical abstract

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 2840

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)

► Show Figures

Figure 1

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 2935

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)

► Show Figures

Figure 1

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 2921

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)

► Show Figures

Figure 1

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 4138

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)

► Show Figures

Figure 1

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 7 | Viewed by 2608

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)

► Show Figures

Figure 1

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 2662

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)

► Show Figures

Figure 1

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 2740

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)

► Show Figures

Graphical abstract

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 3598

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)

► Show Figures

Graphical abstract

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 2862

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)

► Show Figures

Figure 1

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 2332

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)

► Show Figures

Figure 1

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 5613

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)

► Show Figures

Figure 1

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 16 | Viewed by 5279

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)

► Show Figures

Figure 1

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 3036

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)

► Show Figures

Graphical abstract

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 2764

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)

► Show Figures

Figure 1

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 6174

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)

► Show Figures

Graphical abstract

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 4562

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)

► Show Figures

Graphical abstract

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 3406

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)

► Show Figures

Figure 1

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 2113

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)

► Show Figures

Figure 1

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 5061

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)

► Show Figures

Figure 1

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 2665

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)

► Show Figures

Figure 1

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 2256

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)

► Show Figures

Figure 1

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 18 | Viewed by 3228

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)

► Show Figures

Figure 1

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 26 | Viewed by 4765

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)

► Show Figures

Figure 1

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 3097

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)

► Show Figures

Figure 1

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 4 | Viewed by 2770

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)

► Show Figures

Graphical abstract

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 3714

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)

► Show Figures

Graphical abstract

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 3435

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)

► Show Figures

Figure 1

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 4865

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)

► Show Figures

Figure 1

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 22 | Viewed by 4148

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)

► Show Figures

Graphical abstract

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 2 | Viewed by 4118

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)

► Show Figures

Graphical abstract

19 pages, 6718 KiB

Open AccessArticle

Synthesis of Carbon Onion and Its Application as a Porous Carrier for Amorphous Drug Delivery

by Nikhila Miriyala, Daniel J. Kirby, Aude Cumont, Ruoying Zhang, Baogui Shi, Defang Ouyang and Haitao Ye

Crystals 2020, 10(4), 281; https://doi.org/10.3390/cryst10040281 - 7 Apr 2020

Cited by 9 | Viewed by 4131

Abstract

Given the great potential of porous carrier-based drug delivery for stabilising the amorphous form of drugs and enhancing dissolution profiles, this work is focussed on the synthesis and application of carbon onion or onion-like carbon (OLC) as a porous carrier for oral amorphous [...] Read more.

Given the great potential of porous carrier-based drug delivery for stabilising the amorphous form of drugs and enhancing dissolution profiles, this work is focussed on the synthesis and application of carbon onion or onion-like carbon (OLC) as a porous carrier for oral amorphous drug delivery, using paracetamol (PA) and ibuprofen (IBU) as model drugs. Annealing of nanodiamonds at 1100 °C produced OLC with a diamond core that exhibited low cytotoxicity on Caco-2 cells. Solution adsorption followed by centrifugation was used for drug loading and results indicated that the initial concentration of drug in the loading solution needs to be kept below 11.5% PA and 20.7% IBU to achieve complete amorphous loading. Also, no chemical interactions between the drug and OLC could be detected, indicating the safety of loading into OLC without changing the chemical nature of the drug. Drug release was complete in the presence of sodium dodecyl sulphate (SDS) and was faster compared to the pure crystalline drug, indicating the potential of OLC as an amorphous drug carrier. Full article

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

► Show Figures

Figure 1

8 pages, 4163 KiB

Open AccessArticle

Fine Fabrication and Optical Waveguide Characteristics of Hexagonal tris(8-hydroxyquinoline)aluminum(Ⅲ) (Alq₃) Crystal

by Jungwoon Park, Seokho Kim, Jinho Choi, Sung Ho Yoo, Seongjae Oh, Do Hyoung Kim and Dong Hyuk Park

Crystals 2020, 10(4), 260; https://doi.org/10.3390/cryst10040260 - 30 Mar 2020

Cited by 5 | Viewed by 3325

Abstract

Herein, we reported on the precise growth and optical waveguide characteristics of hexagonal tris(8-hydroxyquinoline)aluminum(Ⅲ) (Alq₃) micro-crystals (MCs). The hexagonal Alq₃ MCs were prepared using surfactant-assisted assembly growth with the help of cetyltrimethylammoniumbromide (CTAB), in which the crystallization occurred as a [...] Read more.

Herein, we reported on the precise growth and optical waveguide characteristics of hexagonal tris(8-hydroxyquinoline)aluminum(Ⅲ) (Alq₃) micro-crystals (MCs). The hexagonal Alq₃ MCs were prepared using surfactant-assisted assembly growth with the help of cetyltrimethylammoniumbromide (CTAB), in which the crystallization occurred as a result of molecular assembly and packing. Also, we adjusted the molar ratio of Alq₃ and CTAB for the control degree of crystallization. The formation and structure of Alq₃ MCs were investigated using field-emission scanning electron microscopy and X-ray diffraction pattern experiments, respectively. The solid-state laser confocal microscope-photoluminescence spectra and charge-coupled device images for the Alq₃ MCs were measured to study the luminescence efficiency and colors, respectively. The optical waveguide performance of the hexagonal Alq₃ MCs was measured for each side direction. According to our results, crystalline Alq₃ micro-crystals are promising materials for application to the development of optical communication devices. Full article

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

► Show Figures

Figure 1

10 pages, 3076 KiB

Open AccessArticle

Comparison of the Ionic Liquid Crystal Phase of [C₁₂C₁im][BF₄] and [C₁₂C₁im]Cl by Atomistic MD Simulations

by Giacomo Saielli

Crystals 2020, 10(4), 253; https://doi.org/10.3390/cryst10040253 - 27 Mar 2020

Cited by 7 | Viewed by 3993

Abstract

We present fully atomistic molecular dynamics (MD) simulations at 450 K of two ionic liquid crystals in the smectic phase: 1-dodecyl-3-methylimidazolium tetrafluoroborate ([C₁₂C₁im][BF₄]) and 1-dodecyl-3-methylimidazolium chloride ([C₁₂C₁im]Cl). The two systems experimentally exhibit different [...] Read more.

We present fully atomistic molecular dynamics (MD) simulations at 450 K of two ionic liquid crystals in the smectic phase: 1-dodecyl-3-methylimidazolium tetrafluoroborate ([C₁₂C₁im][BF₄]) and 1-dodecyl-3-methylimidazolium chloride ([C₁₂C₁im]Cl). The two systems experimentally exhibit different ranges of thermal stability of the ionic smectic phase: The chloride salt has a more stable LC phase, between 270.3 K and 377.6 K, with a range of SmA of more than 107 K. In contrast, the tetrafluoroborate salt has a smectic phase between 299.6 K and 311.6 K, with a range of mesophase of just 12 K. The MD simulations show that the chloride system is stable in the smectic phase for the 5 ns of simulation, while the tetrafluoroborate salt melts into an isotropic ionic liquid, in qualitative agreement with the experiments. Comparison of the electrostatic and van der Waals energetic contributions enables one to rationalize the observed behavior as being due to the large size of the [BF₄] anion: a larger size of the anion means a lower charge density, and therefore a weaker electrostatic interaction in the ionic layer. Full article

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

► Show Figures

Figure 1

9 pages, 2336 KiB

Open AccessArticle

The Investigation for Coating Method of Titanium Dioxide Layer in Perovskite Solar Cells

by Pao-Hsun Huang, Chien-Wu Huang, Chih-Chieh Kang, Chia-Hsun Hsu, Shui-Yang Lien, Na-Fu Wang and Chien-Jung Huang

Crystals 2020, 10(3), 236; https://doi.org/10.3390/cryst10030236 - 24 Mar 2020

Cited by 7 | Viewed by 4635

Abstract

The effect of conventional Perovskite solar cells (PSCs) by using different concentration and spin-coating speeds of titanium dioxide (TiO₂) as an electron transport layer (ETL) was studied. The influence of TiO₂ based on device structure: fluorine-doped tin oxide substrate/TiO₂ [...] Read more.

The effect of conventional Perovskite solar cells (PSCs) by using different concentration and spin-coating speeds of titanium dioxide (TiO₂) as an electron transport layer (ETL) was studied. The influence of TiO₂ based on device structure: fluorine-doped tin oxide substrate/TiO₂/Perovskite (CH₃NH₃PbI₃)/2,2′,7,7′-Tetrakis[N,N-di(4-methoxyp phenyl)amino]-9,9′-spirobifluorene/silver, is also studied. The spin-coating speed is varied in a range from 1000 to 3000 rpm to get optimal performance of device. The optimized power conversion efficiency (PCE) of PSCs with original concentration (OC) and double concentration (DC) TiO₂ is 8.74 and 9.93%, respectively. The reason is attributed to excellent absorption in shorter wavelength, compact characteristic, and suitable thickness of TiO₂, leading to perfect short-circuit current density (Jsc), lower series resistance (Rs), and higher fill factor (FF) of 0.75. Besides, recombination of electron and hole is also decreased due to the compact feature, leading to higher open-circuit voltage (V_OC) of 0.91 V. Full article

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

► Show Figures

Figure 1

13 pages, 2520 KiB

Open AccessArticle

Exploring the Chelating Potential of an Easily Synthesized Schiff Base for Copper Sensing

by Jesús Sanmartín-Matalobos, Ana García-Deibe, Morteza Zarepour-Jevinani, Manuel Aboal-Somoza, Pilar Bermejo-Barrera and Matilde Fondo

Crystals 2020, 10(3), 235; https://doi.org/10.3390/cryst10030235 - 24 Mar 2020

Cited by 10 | Viewed by 3018

Abstract

The present study deals with the investigation of Cu²⁺, Ni²⁺ and Pd²⁺ chelating potential of the Schiff base, (E)-N-(2-((2-hydroxybenzylidene)amino)benzyl)-4-methylbenzenesulfonamide (H₂SB). Crystal structures of Ni(HSB)₂, Pd(HSB)₂ and Cu(HSB)₂ have been [...] Read more.

The present study deals with the investigation of Cu²⁺, Ni²⁺ and Pd²⁺ chelating potential of the Schiff base, (E)-N-(2-((2-hydroxybenzylidene)amino)benzyl)-4-methylbenzenesulfonamide (H₂SB). Crystal structures of Ni(HSB)₂, Pd(HSB)₂ and Cu(HSB)₂ have been elucidated from single crystal X-ray diffraction data. NMR spectroscopy showed the presence of two conformers of Pd(HSB)₂ in solution, both with an E configuration of the ligand. The determination of binding constants by fluorescence quenching showed that affinity of H₂SB to Cu²⁺ in solution is higher than for Ni²⁺ and Pd²⁺. Since there is a high demand for selective, sensitive, rapid and simple methods to detect copper in aqueous samples (both as Cu²⁺ ions and as CuO NPs), we have explored H₂SB as an optical chemosensor. H₂SB interacts with increasing concentrations of Cu²⁺ ions, giving rise to a linear increase in the absorbance of a band centered at about 392 nm. H₂SB displays a high selectivity toward Cu²⁺, even in the presence of the most common metal ions in water (Ca²⁺, Mg²⁺, Na⁺, K⁺, Al³⁺ and Fe³⁺), and some heavy transition metal ions such as the soft acids Pd²⁺ and Cd²⁺. H₂SB also interacts with increasing concentrations of CuO NPs, which gives rise to a linear decrease in its fluorescence intensity (λ_em = 500 nm, λ_ex = 390 nm). Quenching has occurred as a result of the formation of a non-fluorescent ground-state surface complex H₂SB–CuO NPs. The limits of detection and quantification of CuO NPs were 9.8 mg/L and 32.6 mg/L, respectively. The presence of TiO₂, Ag and Au NPs does not interfere with the determination of CuO NPs. Full article

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

► Show Figures

Figure 1

12 pages, 4677 KiB

Open AccessArticle

Halogen Bonding Provides Heterooctameric Supramolecular Aggregation of Diaryliodonium Thiocyanate

by Natalia S. Soldatova, Vitalii V. Suslonov, Troyana Yu. Kissler, Daniil M. Ivanov, Alexander S. Novikov, Mekhman S. Yusubov, Pavel S. Postnikov and Vadim Yu. Kukushkin

Crystals 2020, 10(3), 230; https://doi.org/10.3390/cryst10030230 - 22 Mar 2020

Cited by 37 | Viewed by 3728

Abstract

The crystal structure of the newly synthesized 4-methoxyphenyl(phenyl)iodonium thiocyanate, [PhI(4-C₆H₄OMe)](SCN), represents the first example of 16-membered cyclic heterooctamer formed by halogen bonding between the iodonium cation and SCN⁻. Results of density functional theory (DFT) calculations followed by [...] Read more.

The crystal structure of the newly synthesized 4-methoxyphenyl(phenyl)iodonium thiocyanate, [PhI(4-C₆H₄OMe)](SCN), represents the first example of 16-membered cyclic heterooctamer formed by halogen bonding between the iodonium cation and SCN⁻. Results of density functional theory (DFT) calculations followed by the topological analysis of the electron density distribution within the framework of the quantum theory of atoms in molecules (QTAIM) method at the ωB97XD/DZP-DKH level of theory reveal that energies of attractive intermolecular noncovalent interactions I···S and I···N (responsible for the formation of heterooctameric supramolecular clusters {PhI(4-C₆H₄OMe)}₄·{SCN}₄ in the solid state structure of [PhI(4-C₆H₄OMe)](SCN)) vary from 0.9 to 8.5 kcal/mol. Full article

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

► Show Figures

Figure 1

7 pages, 1762 KiB

Open AccessArticle

Microstructure and Mechanical Properties of Platinum Fiber Fabricated by Unidirectional Solidification

by Yuui Yokota, Takayuki Nihei, Masao Yoshino, Akihiro Yamaji, Satoshi Toyoda, Hiroki Sato, Yuji Ohashi, Shunsuke Kurosawa, Kei Kamada and Akira Yoshikawa

Crystals 2020, 10(3), 216; https://doi.org/10.3390/cryst10030216 - 19 Mar 2020

Cited by 4 | Viewed by 3325

Abstract

The microstructure and mechanical properties of platinum (Pt) fibers fabricated by unidirectional solidification using the alloy-micro-pulling-down (A-μ-PD) method were investigated using a Universal Testing Machine and Electron Backscattered Diffraction (EBSD). The Pt fiber fabricated at a growth rate of 10 mm/min was composed [...] Read more.

The microstructure and mechanical properties of platinum (Pt) fibers fabricated by unidirectional solidification using the alloy-micro-pulling-down (A-μ-PD) method were investigated using a Universal Testing Machine and Electron Backscattered Diffraction (EBSD). The Pt fiber fabricated at a growth rate of 10 mm/min was composed of relatively large grains with <100> crystal orientation along the growth direction. The crystal orientation was consistent with the easy axis of the crystal growth on the face-centered-cubic (f.c.c.) structure. On the other hand, the adjacent grains of the Pt fiber fabricated at 50 mm/min were randomly oriented owing to a faster growth rate. In tensile tests, the Pt fibers fabricated by the A-μ-PD method indicated extremely different stress–strain curves compared to the commercial Pt wire. The maximum tensile stress of the Pt fiber reached ~100 MPa, and the Pt fiber ruptured after 58% nominal strain. Full article

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

► Show Figures

Figure 1

15 pages, 6872 KiB

Open AccessArticle

Seeded Mineralization in Silk Fibroin Hydrogel Matrices Leads to Continuous Rhombohedral CaCO₃ Films

by Dan Wang, Yu-xuan Feng, Ming Li, Shengdi Guo and Yuan Jiang

Crystals 2020, 10(3), 166; https://doi.org/10.3390/cryst10030166 - 3 Mar 2020

Cited by 4 | Viewed by 3607

Abstract

As many biominerals are formed in gel-like media, hydrogel-mediated mineralization is deemed as paradigms of biomineralization and ideal approaches to synthetic minerals with hierarchical architectures and related functions. Nevertheless, the long diffusion distance in hydrogels makes mineralization a diffusion-limited process, leading to isolated [...] Read more.

As many biominerals are formed in gel-like media, hydrogel-mediated mineralization is deemed as paradigms of biomineralization and ideal approaches to synthetic minerals with hierarchical architectures and related functions. Nevertheless, the long diffusion distance in hydrogels makes mineralization a diffusion-limited process, leading to isolated crystals instead of uniform hierarchical architectures. In the current study, seeded mineralization in silk fibroin hydrogel matrices is successful in delivering continuous rhombohedral CaCO₃ films. Though the coverage of hydrogel matrices makes mineralization a diffusion-limited process, the presence of seed layers promotes the growth of uniform overlayers in proper conditions. The regulation of the solid content of hydrogels provides a rational route to rhombohedral architectures with tunable morphologies and thickness. In the course of mineralization, the hydrogel matrices are partially occluded in rhombohedral films as inter- and intra-crystalline constituents, as confirmed by scanning and transmission electron microscopy. Our study confirms the availability of synthesizing continuous mineralized films with hierarchical architectures and the structural gradient in hydrogel matrices via self-organized mineralization. These films with the occlusion of hydrogel constituents may exhibit significant strength and resilience, and their formation can deepen our mechanistic understanding of biomineralization proceeding in gel-like media. Full article

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

► Show Figures

Figure 1

11 pages, 3398 KiB

Open AccessArticle

PbMoO₄ Synthesis from Ancient Lead and Its Single Crystal Growth for Neutrinoless Double Beta Decay Search

by Arshad Khan, Pabitra Aryal, Hongjoo Kim, Moo Hyun Lee and Yeongduk Kim

Crystals 2020, 10(3), 150; https://doi.org/10.3390/cryst10030150 - 27 Feb 2020

Cited by 11 | Viewed by 3730

Abstract

A powder synthesis of PbMoO₄ (PMO) from ancient lead (Pb) and deeply purified commercial MoO₃ powders was performed using a wet chemistry technique to achieve the low radioactivity scintillator for neutrinoless double beta decay search in ¹⁰⁰Mo. The synthesized powders [...] Read more.

A powder synthesis of PbMoO₄ (PMO) from ancient lead (Pb) and deeply purified commercial MoO₃ powders was performed using a wet chemistry technique to achieve the low radioactivity scintillator for neutrinoless double beta decay search in ¹⁰⁰Mo. The synthesized powders were used to grow single crystals of PbMoO₄ by the Czochralski technique in an Ar environment. The luminescence and scintillation properties were measured with excitations using UV, X- and γ-rays in the temperature range of 10–300 K. Annealing of the grown PMO crystal in an air atmosphere significantly enhanced the scintillation light yield compared to that measured before annealing. The scintillation light yield of grown PMO crystal at 10 K was found to be 127% to that of a reference PMO crystal under 662 keV γ-rays excitation from a ¹³⁷Cs source. The background measurement of the grown crystal performed at 50 K shows a lower internal activity from ²¹⁰Pb compared to that of reference PMO (grown from modern Pb) crystal. These preliminary performances show that the PMO crystal grown from ancient Pb and deeply purified MoO₃ powders has a great potential to be used as a cryogenic scintillator for the neutrinoless double beta decay search in ¹⁰⁰Mo. Full article

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

► Show Figures

Figure 1

14 pages, 4473 KiB

Open AccessArticle

Ultrasonic Pulse Velocity—Compressive Strength Relationship for Portland Cement Mortars Cured at Different Conditions

by Esteban Estévez, Domingo Alfonso Martín, Cristina Argiz and Miguel Ángel Sanjuán

Crystals 2020, 10(2), 133; https://doi.org/10.3390/cryst10020133 - 22 Feb 2020

Cited by 23 | Viewed by 5762

Abstract

The purpose of this paper is to establish some correlations between the main technical parameter with regard to the cement-based materials technology, the 28-day compressive strength, and ultrasonic pulse velocity of standard mortar samples cured at three different conditions—(i) under water at 22 [...] Read more.

The purpose of this paper is to establish some correlations between the main technical parameter with regard to the cement-based materials technology, the 28-day compressive strength, and ultrasonic pulse velocity of standard mortar samples cured at three different conditions—(i) under water at 22 °C; (ii) climatic chamber at 95% RH and 22 °C; (iii) lab ambient, 50% RH, and 22 °C—and after five curing periods of 1, 2, 7, 14, and 28 days. Good correlations for each curing conditions were obtained. All the positive linear relationships showed better R2 than exponential ones. These findings may promote the use of ultrasonic pulse velocity for the estimation of the 28-day compressive strength of standard Portland cement samples within the factory internal quality control. Full article

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

► Show Figures

Graphical abstract

10 pages, 10866 KiB

Open AccessArticle

Side-Chain Liquid Crystal Co-Polymers for Angular Photochromic Anti-Counterfeiting Powder and Fiber

by Yanzi Gao, Ke Feng, Jin Zhang and Lanying Zhang

Crystals 2020, 10(2), 128; https://doi.org/10.3390/cryst10020128 - 20 Feb 2020

Cited by 1 | Viewed by 2695

Abstract

Anti-counterfeiting technologies with the features of easy distinguishability, high cost performance, and good processability are needed to meet the demands of a market during the consumption upgrading moment. A series of side-chain liquid crystal co-polymers (SCLCPs) are designed, synthesized, and blended, and the [...] Read more.

Anti-counterfeiting technologies with the features of easy distinguishability, high cost performance, and good processability are needed to meet the demands of a market during the consumption upgrading moment. A series of side-chain liquid crystal co-polymers (SCLCPs) are designed, synthesized, and blended, and the preparation of a series of angular photochromic materials that have different center reflection wavelengths in the visible and near infra-red region is reported in this article. Differential scanning calorimetry and polarized optical microscopy were utilized to characterize the phase transition behaviors and self-assembling structures of the SCLCPs. The selective reflection properties were characterized with a UV/VIS/IR spectrum study and further verified by scanning electron microscopy. The results showed that the SCLCPs had the desired reflection wavelengths and thermal stability. The SCLCPs could easily form a planar texture of cholesteric liquid crystal and, depending on the good processability, anti-counterfeiting powders and fibers with angular photochromic features were prepared and characterized to prove the potential applications of the SCLCPs in anti-counterfeiting labels. Full article

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

► Show Figures

Figure 1

10 pages, 4034 KiB

Open AccessArticle

3D Numerical Analysis of the Asymmetric Three-Phase Line of Floating Zone for Silicon Crystal Growth

by Xue-Feng Han, Xin Liu, Satoshi Nakano, Hirofumi Harada, Yoshiji Miyamura and Koichi Kakimoto

Crystals 2020, 10(2), 121; https://doi.org/10.3390/cryst10020121 - 15 Feb 2020

Cited by 2 | Viewed by 2878

Abstract

A numerical simulation has been carried out to study the asymmetric heat transfer, fluid flow, and three-phase line to explain the phenomenon of the spillage of the melt in floating zone (FZ) silicon growth. A three-dimensional high-frequency electromagnetic (EM) field is coupled with [...] Read more.

A numerical simulation has been carried out to study the asymmetric heat transfer, fluid flow, and three-phase line to explain the phenomenon of the spillage of the melt in floating zone (FZ) silicon growth. A three-dimensional high-frequency electromagnetic (EM) field is coupled with the heat transfer in the melt and crystal calculation domains. The current density along the three-phase line is investigated to demonstrate the inhomogeneous heating along the three-phase line. The asymmetric heating is found to affect the flow pattern and temperature distribution of the melt. The three-dimensional solid–liquid interface results show that, below the current supplies, the interface is deflected due to strong heating below the current supplies. The calculated asymmetric three-phase line shows a similar trend as the experimentally observed results. The results indicate that the re-melting and spillage phenomenon could occur below the current supplies. Full article

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

► Show Figures

Figure 1

16 pages, 1889 KiB

Open AccessArticle

Interaction and Polarization Energy Relationships in σ-Hole and π-Hole Bonding

by Jane S. Murray and Peter Politzer

Crystals 2020, 10(2), 76; https://doi.org/10.3390/cryst10020076 - 30 Jan 2020

Cited by 67 | Viewed by 4365

Abstract

We demonstrate that a wide range of σ- and π-hole interaction energies can be related to (a) the electrostatic potentials and electric fields of the σ- and π-hole molecules at the approximate positions of the negative sites and (b) the electrostatic potentials and [...] Read more.

We demonstrate that a wide range of σ- and π-hole interaction energies can be related to (a) the electrostatic potentials and electric fields of the σ- and π-hole molecules at the approximate positions of the negative sites and (b) the electrostatic potentials and polarizabilities of the latter. This is consistent with the Coulombic nature of these interactions, which should be understood to include both electrostatics and polarization. The energies associated with polarization were estimated and were shown to overall be greater for the stronger interactions; no new factors need be introduced to account for these. All of the interactions can be treated in the same manner. Full article

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

► Show Figures

Figure 1

14 pages, 35089 KiB

Open AccessFeature PaperArticle

Quasi-Transient Calculation of Czochralski Growth of Ge Crystals Using the Software Elmer

by Wolfram Miller, Nikolay Abrosimov, Jörg Fischer, Alexander Gybin, Uta Juda, Stefan Kayser and Jószef Janicskó-Csáthy

Crystals 2020, 10(1), 18; https://doi.org/10.3390/cryst10010018 - 31 Dec 2019

Cited by 7 | Viewed by 4599

Abstract

A numerical scheme was developed to compute the thermal and stress fields of the Czochralski process in a quasi-time dependent mode. The growth velocity was computed from the geometrical changes in melt and crystal due to pulling for every stage, for which the [...] Read more.

A numerical scheme was developed to compute the thermal and stress fields of the Czochralski process in a quasi-time dependent mode. The growth velocity was computed from the geometrical changes in melt and crystal due to pulling for every stage, for which the thermal and stress fields were computed by using the open source software Elmer. The method was applied to the Czochralski growth of Ge crystals by inductive heating. From a series of growth experiments, we chose one as a reference to check the validity of the scheme with respect to this Czochralski process. A good agreement both for the shapes of the melt/crystal interface at various time steps and the change in power consumption with process time was observed. Full article

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

► Show Figures

Figure 1

9 pages, 3142 KiB

Open AccessArticle

Dislocation Reaction Mechanism for Enhanced Strain Hardening in Crystal Nano-Indentations

by Ronald W. Armstrong and Wayne L. Elban

Crystals 2020, 10(1), 9; https://doi.org/10.3390/cryst10010009 - 23 Dec 2019

Cited by 6 | Viewed by 3090

Abstract

Stress–strain calculations are presented for nano-indentations made in: (1) an ammonium perchlorate (AP), NH₄ClO₄, {210} crystal surface; (2) an α-iron (111) crystal surface; (3) a simulated test on an α-iron (100) crystal surface. In each case, the calculation of [...] Read more.

Stress–strain calculations are presented for nano-indentations made in: (1) an ammonium perchlorate (AP), NH₄ClO₄, {210} crystal surface; (2) an α-iron (111) crystal surface; (3) a simulated test on an α-iron (100) crystal surface. In each case, the calculation of an exceptionally-enhanced plastic strain hardening, beyond that coming from the significant effect of small dislocation separations in the indentation deformation zone, is attributed to the formation of dislocation reaction obstacles hindering further dislocation movement. For the AP crystal, the exceptionally-high dislocation reaction-based strain hardening, relative to the elastic shear modulus, leads to (001) cleavage cracking in nano-, micro- and macro-indentations. For α-iron, the reaction of (a/2) <111> dislocations to form a [010] Burgers vector dislocation obstacles at designated {110} slip system intersections accounts for a higher strain hardening in both experimental and simulated nano-indentation test results. The α-iron stress–strain calculations are compared, both for the elastic deformation and plastic strain hardening of nano-indented (100) versus (111) crystal surfaces and include important observations derived from internally-tracked (a/2) <010> Burgers vector dislocation structures obtained in simulation studies. Additional comparisons are made between the α-iron calculations and other related strength properties reported either for bulk, micro-pillar, or additional simulated nano-crystal or heavily-drawn polycrystalline wire materials. Full article

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

► Show Figures

Figure 1

17 pages, 2970 KiB

Open AccessArticle

A High-Pressure Investigation of the Synthetic Analogue of Chalcomenite, CuSeO₃∙2H₂O

by Javier Gonzalez-Platas, Placida Rodriguez-Hernandez, Alfonso Muñoz, U. R. Rodríguez-Mendoza, Gwilherm Nénert and Daniel Errandonea

Crystals 2019, 9(12), 643; https://doi.org/10.3390/cryst9120643 - 5 Dec 2019

Cited by 9 | Viewed by 4677

Abstract

Synthetic chalcomenite-type cupric selenite CuSeO₃∙2H₂O has been studied at room temperature under compression up to pressures of 8 GPa by means of single-crystal X-ray diffraction, Raman spectroscopy, and density-functional theory. According to X-ray diffraction, the orthorhombic phase undergoes an [...] Read more.

Synthetic chalcomenite-type cupric selenite CuSeO₃∙2H₂O has been studied at room temperature under compression up to pressures of 8 GPa by means of single-crystal X-ray diffraction, Raman spectroscopy, and density-functional theory. According to X-ray diffraction, the orthorhombic phase undergoes an isostructural phase transition at 4.0(5) GPa with the thermodynamic character being first-order. This conclusion is supported by Raman spectroscopy studies that have detected the phase transition at 4.5(2) GPa and by the first-principles computing simulations. The structure solution at different pressures has provided information on the change with pressure of unit–cell parameters as well as on the bond and polyhedral compressibility. A Birch–Murnaghan equation of state has been fitted to the unit–cell volume data. We found that chalcomenite is highly compressible with a bulk modulus of 42–49 GPa. The possible mechanism driving changes in the crystal structure is discussed, being the behavior of CuSeO₃∙2H₂O mainly dominated by the large compressibility of the coordination polyhedron of Cu. On top of that, an assignation of Raman modes is proposed based upon density-functional theory and the pressure dependence of Raman modes discussed. Finally, the pressure dependence of phonon frequencies experimentally determined is also reported. Full article

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

► Show Figures

Figure 1

Review

Jump to: Editorial, Research

15 pages, 2935 KiB

Open AccessReview

Sol–Gel Ceramics for SEIRAS and SERS Substrates

by Jesús Alberto Garibay’Alvarado and Simón Yobanny Reyes-López

Crystals 2021, 11(4), 439; https://doi.org/10.3390/cryst11040439 - 18 Apr 2021

Cited by 7 | Viewed by 3821

Abstract

Surface Enhanced Infrared Absorption Spectroscopy and Surface Enhanced Raman Spectroscopy are analytic techniques that have not been massively adopted since there are issues that still need to be solved with regard to the nature of the signal enhancement substrates used. The sol–gel method [...] Read more.

Surface Enhanced Infrared Absorption Spectroscopy and Surface Enhanced Raman Spectroscopy are analytic techniques that have not been massively adopted since there are issues that still need to be solved with regard to the nature of the signal enhancement substrates used. The sol–gel method for the obtention of ceramics provides an alternative for the production of said substrates. Ceramics are very wear- and heat-resistant, properties that can be used for their regeneration, and through the sol–gel method, ceramics can be produced with high purity as well as can be fashioned in many ways through different techniques, which can be helpful in the pursuit of reproducibility. This paper discusses the different advantages of sol–gel ceramics, their use in the electrospinning technique, and their application in infrared and Raman surface-enhanced spectroscopy. Full article

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

► Show Figures

Figure 1

23 pages, 9922 KiB

Open AccessReview

On the Coordination Role of Pyridyl-Nitrogen in the Structural Chemistry of Pyridyl-Substituted Dithiocarbamate Ligands

by Edward R.T. Tiekink

Crystals 2021, 11(3), 286; https://doi.org/10.3390/cryst11030286 - 14 Mar 2021

Cited by 10 | Viewed by 2564

Abstract

A search of the Cambridge Structural Database was conducted for pyridyl-substituted dithiocarbamate ligands. This entailed molecules containing both an NCS₂⁻ residue and pyridyl group(s), in order to study their complexation behavior in their transition metal and main group element crystals, i.e., [...] Read more.

A search of the Cambridge Structural Database was conducted for pyridyl-substituted dithiocarbamate ligands. This entailed molecules containing both an NCS₂⁻ residue and pyridyl group(s), in order to study their complexation behavior in their transition metal and main group element crystals, i.e., d- and p-block elements. In all, 73 different structures were identified with 30 distinct dithiocarbamate ligands. As a general observation, the structures of the transition metal dithiocarbamates resembled those of their non-pyridyl derivatives, there being no role for the pyridyl-nitrogen atom in coordination. While the same is true for many main group element dithiocarbamates, a far greater role for coordination of the pyridyl-nitrogen atoms was evident, in particular, for the heavier elements. The participation of pyridyl-nitrogen in coordination often leads to the formation of dimeric aggregates but also one-dimensional chains and two-dimensional arrays. Capricious behaviour in closely related species that adopted very different architectures is noted. Sometimes different molecules comprising the asymmetric-unit of a crystal behave differently. The foregoing suggests this to be an area in early development and is a fertile avenue for systematic research for probing further crystallization outcomes and for the rational generation of supramolecular architectures. Full article

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

► Show Figures

Graphical abstract

27 pages, 4020 KiB

Open AccessReview

Application of Magnetic and Dielectric Nanofluids for Electromagnetic-Assistance Enhanced Oil Recovery: A Review

by Yarima Mudassir Hassan, Beh Hoe Guan, Hasnah Mohd Zaid, Mohammed Falalu Hamza, Muhammad Adil, Abdullahi Abbas Adam and Kurnia Hastuti

Crystals 2021, 11(2), 106; https://doi.org/10.3390/cryst11020106 - 26 Jan 2021

Cited by 27 | Viewed by 4513

Abstract

Crude oil has been one of the most important natural resources since 1856, which was the first time a world refinery was constructed. However, the problem associated with trapped oil in the reservoir is a global concern. Consequently, Enhanced Oil Recovery (EOR) is [...] Read more.

Crude oil has been one of the most important natural resources since 1856, which was the first time a world refinery was constructed. However, the problem associated with trapped oil in the reservoir is a global concern. Consequently, Enhanced Oil Recovery (EOR) is a modern technique used to improve oil productivity that is being intensively studied. Nanoparticles (NPs) exhibited exceptional outcomes when applied in various sectors including oil and gas industries. The harshness of the reservoir situations disturbs the effective transformations of the NPs in which the particles tend to agglomerate and consequently leads to the discrimination of the NPs and their being trapped in the rock pores of the reservoir. Hence, Electromagnetic-Assisted nanofluids are very consequential in supporting the effective performance of the nanoflooding process. Several studies have shown considerable incremental oil recovery factors by employing magnetic and dielectric NPs assisted by electromagnetic radiation. This is attributed to the fact that the injected nanofluids absorb energy disaffected from the EM source, which changes the fluid mobility by creating disruptions within the fluid’s interface and allowing trapped oil to be released. This paper attempts to review the experimental work conducted via electromagnetic activation of magnetic and dielectric nanofluids for EOR and to analyze the effect of EM-assisted nanofluids on parameters such as sweeping efficiency, Interfacial tension, and wettability alteration. The current study is very significant in providing a comprehensive analysis and review of the role played by EM-assisted nanofluids to improve laboratory experiments as one of the substantial prerequisites in optimizing the process of the field application for EOR in the future. Full article

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

► Show Figures

Figure 1

35 pages, 10102 KiB

Open AccessFeature PaperReview

Heterometallic Complexes Containing the Ni^II-Ln^III-Ni^II Moiety—Structures and Magnetic Properties

by Catherine P. Raptopoulou

Crystals 2020, 10(12), 1117; https://doi.org/10.3390/cryst10121117 - 8 Dec 2020

Cited by 4 | Viewed by 2235

Abstract

This review summarizes the structural characteristics and magnetic properties of trinuclear complexes containing the Ni^II-Ln^III-Ni^II moiety and also oligonuclear complexes and coordination polymers containing the same trinuclear moiety. The ligands used are mainly polydentate Schiff base ligands and [...] Read more.

This review summarizes the structural characteristics and magnetic properties of trinuclear complexes containing the Ni^II-Ln^III-Ni^II moiety and also oligonuclear complexes and coordination polymers containing the same trinuclear moiety. The ligands used are mainly polydentate Schiff base ligands and reduced Schiff base ligands and, in some cases, oximato, β-diketonato, pyridyl ketone ligands and others. The compounds reported are restricted to those containing one, two and three oxygen atoms as bridges between the metal ions; examples of carboxylato and oximato bridging are also included due to structural similarity. The magnetic properties of the complexes range from ferro- to antiferromagnetic depending on the nature of the lanthanide ion. Full article

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

► Show Figures

Graphical abstract

52 pages, 5971 KiB

Open AccessReview

Making NSCLC Crystal Clear: How Kinase Structures Revolutionized Lung Cancer Treatment

by Juliana F. Vilachã, Sarah C. Mitchel, Muluembet Z. Akele, Stephen Evans and Matthew R. Groves

Crystals 2020, 10(9), 725; https://doi.org/10.3390/cryst10090725 - 20 Aug 2020

Cited by 5 | Viewed by 6088

Abstract

The parallel advances of different scientific fields provide a contemporary scenario where collaboration is not a differential, but actually a requirement. In this context, crystallography has had a major contribution on the medical sciences, providing a “face” for targets of diseases that previously [...] Read more.

The parallel advances of different scientific fields provide a contemporary scenario where collaboration is not a differential, but actually a requirement. In this context, crystallography has had a major contribution on the medical sciences, providing a “face” for targets of diseases that previously were known solely by name or sequence. Worldwide, cancer still leads the number of annual deaths, with 9.6 million associated deaths, with a major contribution from lung cancer and its 1.7 million deaths. Since the relationship between cancer and kinases was unraveled, these proteins have been extensively explored and became associated with drugs that later attained blockbuster status. Crystallographic structures of kinases related to lung cancer and their developed and marketed drugs provided insight on their conformation in the absence or presence of small molecules. Notwithstanding, these structures were also of service once the initially highly successful drugs started to lose their effectiveness in the emergence of mutations. This review focuses on a subclassification of lung cancer, non-small cell lung cancer (NSCLC), and major oncogenic driver mutations in kinases, and how crystallographic structures can be used, not only to provide awareness of the function and inhibition of these mutations, but also how these structures can be used in further computational studies aiming at addressing these novel mutations in the field of personalized medicine. Full article

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

► Show Figures

Graphical abstract

35 pages, 3713 KiB

Open AccessReview

Zeolite-Like Boron Imidazolate Frameworks (BIFs): Synthesis and Application

by Vera I. Isaeva, Kostantinos E. Papathanasiou and Leonid M. Kustov

Crystals 2020, 10(7), 617; https://doi.org/10.3390/cryst10070617 - 15 Jul 2020

Cited by 11 | Viewed by 6040

Abstract

This review is devoted to discussion of the latest advances in design and applications of boron imidazolate frameworks (BIFs) that are a particular sub-family of zeolite-like metal–organic frameworks family. A special emphasis is made on nanostructured hybrid materials based on BIF matrices and [...] Read more.

This review is devoted to discussion of the latest advances in design and applications of boron imidazolate frameworks (BIFs) that are a particular sub-family of zeolite-like metal–organic frameworks family. A special emphasis is made on nanostructured hybrid materials based on BIF matrices and their modern applications, especially in environment remediation and energy conversion. Full article

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

► Show Figures

Figure 1

23 pages, 8631 KiB

Open AccessReview

Biocrystals in Plants: A Short Review on Biomineralization Processes and the Role of Phototropins into the Uptake of Calcium

by Mayra Cuéllar-Cruz, Karina Sandra Pérez, María Eugenia Mendoza and Abel Moreno

Crystals 2020, 10(7), 591; https://doi.org/10.3390/cryst10070591 - 9 Jul 2020

Cited by 24 | Viewed by 20517

Abstract

The biomineralization process is a mechanism inherent to all organisms of the Earth. Throughout the decades, diverse works have reported that the origin of life is tied to crystals, specifically to biominerals of silica that catalyzed RNA, and had some influence in the [...] Read more.

The biomineralization process is a mechanism inherent to all organisms of the Earth. Throughout the decades, diverse works have reported that the origin of life is tied to crystals, specifically to biominerals of silica that catalyzed RNA, and had some influence in the homochirality. Although the mechanism by which crystals surfaces (minerals) gave origin to life has not yet been proven, the truth is that, up to the present, biominerals are being synthetized by the organisms of different kingdoms in two basic ways: biologically induced and biologically controlled biomineralization. Paradoxically, this fact makes a fundamental difference between inorganic materials and those formed by living organisms, as the latter are associated with macromolecules that are bound to the mineral phase. Conserving growth and formation of these biogenic organic crystals inside cells is a fascinating subject that has been studied mainly in some of the kingdoms, like Monera (bacteria), Fungi (yeasts), and Animalia (Homo sapiens). Notwithstanding in the Plantae kingdom, the formation, conservation, and functions of crystals has not yet been completely elucidated and described, which is of particular relevance because life on Earth, as we know it, would not be possible without plants. The aim of the present work is to revise the different crystals of calcium oxalate synthetized inside the cells of plants, as well as to identify the mechanism of their formation and their possible functions in plants. The last part is related to the existence of certain proteins called phototropins, which not only work as the blue-light sensors, but they also play an important role on the accumulation of calcium in vacuoles. This new trend is shortly reviewed to explain the characteristics and their plausible role in the calcium uptake along with the biomineralization processes. Full article

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

► Show Figures

Figure 1

13 pages, 310 KiB

Open AccessReview

The Resolution in X-ray Crystallography and Single-Particle Cryogenic Electron Microscopy

by Victor R.A. Dubach and Albert Guskov

Crystals 2020, 10(7), 580; https://doi.org/10.3390/cryst10070580 - 5 Jul 2020

Cited by 18 | Viewed by 18324

Abstract

X-ray crystallography and single-particle analysis cryogenic electron microscopy are essential techniques for uncovering the three-dimensional structures of biological macromolecules. Both techniques rely on the Fourier transform to calculate experimental maps. However, one of the crucial parameters, resolution, is rather broadly defined. Here, the [...] Read more.

X-ray crystallography and single-particle analysis cryogenic electron microscopy are essential techniques for uncovering the three-dimensional structures of biological macromolecules. Both techniques rely on the Fourier transform to calculate experimental maps. However, one of the crucial parameters, resolution, is rather broadly defined. Here, the methods to determine the resolution in X-ray crystallography and single-particle analysis are summarized. In X-ray crystallography, it is becoming increasingly more common to include reflections discarded previously by traditionally used standards, allowing for the inclusion of incomplete and anisotropic reflections into the refinement process. In general, the resolution is the smallest lattice spacing given by Bragg’s law for a particular set of X-ray diffraction intensities; however, typically the resolution is truncated by the user during the data processing based on certain parameters and later it is used during refinement. However, at which resolution to perform such a truncation is not always clear and this makes it very confusing for the novices entering the structural biology field. Furthermore, it is argued that the effective resolution should be also reported as it is a more descriptive measure accounting for anisotropy and incompleteness of the data. In single particle cryo-EM, the situation is not much better, as multiple ways exist to determine the resolution, such as Fourier shell correlation, spectral signal-to-noise ratio and the Fourier neighbor correlation. The most widely accepted is the Fourier shell correlation using a threshold of 0.143 to define the resolution (so-called “gold-standard”), although it is still debated whether this is the correct threshold. Besides, the resolution obtained from the Fourier shell correlation is an estimate of varying resolution across the density map. In reality, the interpretability of the map is more important than the numerical value of the resolution. Full article

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

► Show Figures

Figure 1

24 pages, 9622 KiB

Open AccessReview

Photo-Aligned Ferroelectric Liquid Crystal Devices with Novel Electro-Optic Characteristics

by Vladimir Chigrinov, Qi Guo and Aleksey Kudreyko

Crystals 2020, 10(7), 563; https://doi.org/10.3390/cryst10070563 - 1 Jul 2020

Cited by 8 | Viewed by 4077

Abstract

This paper examines different applications of ferroelectric liquid crystal devices based on photo-alignment. Successful application of the photo-alignment technique is considered to be a critical breakthrough. A variety of display and photonic devices with azo dye aligned ferroelectric liquid crystals is presented: smart [...] Read more.

This paper examines different applications of ferroelectric liquid crystal devices based on photo-alignment. Successful application of the photo-alignment technique is considered to be a critical breakthrough. A variety of display and photonic devices with azo dye aligned ferroelectric liquid crystals is presented: smart glasses, liquid crystal Pancharatnam–Berry phase optical elements, 2D/3D switchable lenses, and laser therapy devices. Comparison of electro-optical behavior of ferroelectric liquid crystals is described considering the performance of devices. This paper facilitates the optimization of device design, and broadens the possible applications in the display and photonic area. Full article

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

► Show Figures

Figure 1

16 pages, 650 KiB

Open AccessFeature PaperReview

Assessment of Crystalline Materials for Solid State Lighting Applications: Beyond the Rare Earth Elements

by Pier Carlo Ricci

Crystals 2020, 10(7), 559; https://doi.org/10.3390/cryst10070559 - 1 Jul 2020

Cited by 20 | Viewed by 4475

Abstract

In everyday life, we are continually exposed to different lighting systems, from the home interior to car lights and from public lighting to displays. The basic emission principles on which they are based range from the old incandescent lamps to the well-established compact [...] Read more.

In everyday life, we are continually exposed to different lighting systems, from the home interior to car lights and from public lighting to displays. The basic emission principles on which they are based range from the old incandescent lamps to the well-established compact fluorescent lamps (CFL) and to the more modern Light Emitting Diode (LEDs) that are dominating the actual market and also promise greater development in the coming years. In the LED technology, the key point is the electroluminescence material, but the fundamental role of proper phosphors is sometimes underestimated even when it is essential for an ideal color rendering. In this review, we analyze the main solid-state techniques for lighting applications, paying attention to the fundamental properties of phosphors to be successfully applied. Currently, the most widely used materials are based on rare-earth elements (REEs) whereas Ce:YAG represents the benchmark for white LEDs. However, there are several drawbacks to the REEs’ supply chain and several concerns from an environmental point of view. We analyze these critical issues and review alternative materials that can overcome their use. New compounds with reduced or totally REE free, quantum dots, metal–organic framework, and organic phosphors will be examined with reference to the current state-of-the-art. Full article

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

► Show Figures

Figure 1

20 pages, 2208 KiB

Open AccessReview

Quantum Crystallography in the Last Decade: Developments and Outlooks

by Alessandro Genoni and Piero Macchi

Crystals 2020, 10(6), 473; https://doi.org/10.3390/cryst10060473 - 3 Jun 2020

Cited by 32 | Viewed by 4693

Abstract

In this review article, we report on the recent progresses in the field of quantum crystallography that has witnessed a massive increase of production coupled with a broadening of the scope in the last decade. It is shown that the early thoughts about [...] Read more.

In this review article, we report on the recent progresses in the field of quantum crystallography that has witnessed a massive increase of production coupled with a broadening of the scope in the last decade. It is shown that the early thoughts about extracting quantum mechanical information from crystallographic experiments are becoming reality, although a century after prediction. While in the past the focus was mainly on electron density and related quantities, the attention is now shifting toward determination of wavefunction from experiments, which enables an exhaustive determination of the quantum mechanical functions and properties of a system. Nonetheless, methods based on electron density modelling have evolved and are nowadays able to reconstruct tiny polarizations of core electrons, coupling charge and spin models, or determining the quantum behaviour at extreme conditions. Far from being routine, these experimental and computational results should be regarded with special attention by scientists for the wealth of information on a system that they actually contain. Full article

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

► Show Figures

Figure 1

34 pages, 7586 KiB

Open AccessReview

Printing ZnO Inks: From Principles to Devices

by Giuseppe Arrabito, Yana Aleeva, Riccardo Pezzilli, Vittorio Ferrara, Pier Gianni Medaglia, Bruno Pignataro and Giuseppe Prestopino

Crystals 2020, 10(6), 449; https://doi.org/10.3390/cryst10060449 - 31 May 2020

Cited by 19 | Viewed by 7470

Abstract

Solution-based printing approaches permit digital designs to be converted into physical objects by depositing materials in a layer-by-layer additive fashion from microscale to nanoscale resolution. The extraordinary adaptability of this technology to different inks and substrates has received substantial interest in the recent [...] Read more.

Solution-based printing approaches permit digital designs to be converted into physical objects by depositing materials in a layer-by-layer additive fashion from microscale to nanoscale resolution. The extraordinary adaptability of this technology to different inks and substrates has received substantial interest in the recent literature. In such a context, this review specifically focuses on the realization of inks for the deposition of ZnO, a well-known wide bandgap semiconductor inorganic material showing an impressive number of applications in electronic, optoelectronic, and piezoelectric devices. Herein, we present an updated review of the latest advancements on the ink formulations and printing techniques for ZnO-based nanocrystalline inks, as well as of the major applications which have been demonstrated. The most relevant ink-processing conditions so far explored will be correlated with the resulting film morphologies, showing the possibility to tune the ZnO ink composition to achieve facile, versatile, and scalable fabrication of devices of different natures. Full article

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

► Show Figures

Figure 1

31 pages, 15765 KiB

Open AccessReview

Recent Advancements in Crystalline Pb-Free Halide Double Perovskites

by Muhammad Usman and Qingfeng Yan

Crystals 2020, 10(2), 62; https://doi.org/10.3390/cryst10020062 - 23 Jan 2020

Cited by 47 | Viewed by 9187

Abstract

Lead halide perovskites have gained more and more attention because of their ease of synthesis and excellent photoelectric properties including a large absorption coefficient, long carrier lifetime, long carrier diffusion length, and high carrier mobility. However, their toxicity, instability, and phase degradation in [...] Read more.

Lead halide perovskites have gained more and more attention because of their ease of synthesis and excellent photoelectric properties including a large absorption coefficient, long carrier lifetime, long carrier diffusion length, and high carrier mobility. However, their toxicity, instability, and phase degradation in ambient environments impede their large-scale applications. To address these concerns, it is desirable to find stable alternative halide perovskites without toxicity and with comparable optoelectronic properties to lead-based perovskites. Over the years, a considerable number of lead-free halide perovskites have been added to this family of materials, including A₂B’B’’X₆, A₂BX₆, and A₃B₂X₉ type perovskites. Among these, double perovskites with the general formula A₂B’B’’X₆ are deemed to be a potential alternative to lead halide perovskites as they possess good stability under ambient conditions and excellent optoelectronic properties. In this review, recent progress in exploring Pb-free halide double perovskites is highlighted. The synthesis, composition-tuning, physical properties, and applications of representative 3D, 2D, and nanocrystal A₂B’B’’X₆ double perovskites are introduced. In addition, perspectives about current challenges and solutions in this field are also provided. Full article

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

► Show Figures

Graphical abstract

Journal Menu

Journal Browser

A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals

Share This Special Issue

Special Issue Editors

Special Issue Information

Keywords

Benefits of Publishing in a Special Issue

Published Papers (79 papers)

Editorial

Research

Review

Further Information

Guidelines

MDPI Initiatives

Follow MDPI