Crystals

13 pages, 3843 KiB

Open AccessArticle

Synthesis, Structure, and Photomagnetic Properties of a Hydrogen-Bonded Lattice of [Fe(bpp)₂]²⁺ Spin-Crossover Complexes and Nicotinate Anions

by Verónica Jornet-Mollá, Carlos Giménez-Saiz and Francisco M. Romero

Crystals 2018, 8(11), 439; https://doi.org/10.3390/cryst8110439 - 21 Nov 2018

Cited by 16 | Viewed by 4263

Abstract

In this paper, we report on the synthesis, crystal structure, and photomagnetic properties of the spin-crossover salt of formula [Fe(bpp)₂](C₆H₄NO₂)₂·4H₂O (1·4H₂O) (bpp = 2,6-bis(pyrazol-3-yl)pyridine; C₆H [...] Read more.

In this paper, we report on the synthesis, crystal structure, and photomagnetic properties of the spin-crossover salt of formula [Fe(bpp)₂](C₆H₄NO₂)₂·4H₂O (1·4H₂O) (bpp = 2,6-bis(pyrazol-3-yl)pyridine; C₆H₄NO₂⁻ = nicotinate anion). This compound exhibits a 3D supramolecular architecture built from hydrogen bonds between iron(II) complexes, nicotinate anions, and water molecules. As synthesized, the hydrated material is low-spin and desolvation triggers a low-spin (LS) to high-spin (HS) transformation. Anhydrous phase 1 undergoes a partial spin crossover (T_1/2= 281 K) and a LS to HS photomagnetic conversion with a T(LIESST) value of 56 K. Full article

(This article belongs to the Special Issue Synthesis and Applications of New Spin Crossover Compounds)

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13 pages, 1030 KiB

Open AccessReview

Can Microbially Induced Calcite Precipitation (MICP) through a Ureolytic Pathway Be Successfully Applied for Removing Heavy Metals from Wastewaters?

by Álvaro Esteban Torres-Aravena, Carla Duarte-Nass, Laura Azócar, Rodrigo Mella-Herrera, Mariella Rivas and David Jeison

Crystals 2018, 8(11), 438; https://doi.org/10.3390/cryst8110438 - 21 Nov 2018

Cited by 79 | Viewed by 11480

Abstract

Microbially induced calcite precipitation (MICP) through a ureolytic pathway is a process that promotes calcite precipitation as a result of the urease enzymatic activity of several microorganisms. It has been studied for different technological applications, such as soil bio-consolidation, bio-cementation, CO₂ sequestration, [...] Read more.

Microbially induced calcite precipitation (MICP) through a ureolytic pathway is a process that promotes calcite precipitation as a result of the urease enzymatic activity of several microorganisms. It has been studied for different technological applications, such as soil bio-consolidation, bio-cementation, CO₂ sequestration, among others. Recently, this process has been proposed as a possible process for removing heavy metals from contaminated soils. However, no research has been reported dealing with the MICP process for heavy metal removal from wastewater/waters. This (re)view proposes to consider to such possibility. The main characteristics of MICP are presented and discussed. The precipitation of heavy metals contained in wastewaters/waters via MICP is exanimated based on process characteristics. Moreover, challenges for its successful implementation are discussed, such as the heavy metal tolerance of inoculum, ammonium release as product of urea hydrolysis, and so on. A semi-continuous operation in two steps (cell growth and bio-precipitation) is proposed. Finally, the wastewater from some typical industries releasing heavy metals are examined, discussing the technical barriers and feasibility. Full article

(This article belongs to the Special Issue Biological Crystallization)

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9 pages, 2697 KiB

Open AccessArticle

Interfacial Mixing Analysis for Strained Layer Superlattices by Atom Probe Tomography

by Ayushi Rajeev, Weixin Chen, Jeremy D. Kirch, Susan E. Babcock, Thomas F. Kuech, Thomas Earles and Luke J. Mawst

Crystals 2018, 8(11), 437; https://doi.org/10.3390/cryst8110437 - 21 Nov 2018

Cited by 8 | Viewed by 4471

Abstract

Quantum wells and barriers with precise thicknesses and abrupt composition changes at their interfaces are critical for obtaining the desired emission wavelength from quantum cascade laser devices. High-resolution X-ray diffraction and transmission electron microscopy are commonly used to calibrate and characterize the layers’ [...] Read more.

Quantum wells and barriers with precise thicknesses and abrupt composition changes at their interfaces are critical for obtaining the desired emission wavelength from quantum cascade laser devices. High-resolution X-ray diffraction and transmission electron microscopy are commonly used to calibrate and characterize the layers’ thicknesses and compositions. A complementary technique, atom probe tomography, was employed here to obtain a direct measurement of the 3-dimensional spatially-resolved compositional profile in two In_xGa_1−xAs/In_yAl_1−yAs III-V strained-layer superlattice structures, both grown at 605 °C. Fitting the measured composition profiles to solutions to Fick’s Second Law yielded an average interdiffusion coefficient of 3.5 × 10⁻²³ m² s⁻¹ at 605 °C. The extent of interdiffusion into each layer determined for these specific superlattices was 0.55 nm on average. The results suggest that quaternary active layers will form, rather than the intended ternary compounds, in structures with thicknesses and growth protocols that are typically designed for quantum cascade laser devices. Full article

(This article belongs to the Special Issue MOVPE Growth of Crystalline Film)

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10 pages, 2746 KiB

Open AccessCommunication

Self-Assembly of a Carboxyl-Functionalized BODIPY Dye via Hydrogen Bonding

by Beatriz Matarranz, Angel Sampedro, Constantin G. Daniliuc and Gustavo Fernández

Crystals 2018, 8(11), 436; https://doi.org/10.3390/cryst8110436 - 20 Nov 2018

Cited by 12 | Viewed by 4259

Abstract

We report the synthesis, characterization, and self-assembly behavior of a 4,4-Difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) dye functionalized at the meso-position with a butyric acid group. Various spectroscopic investigations (UV-Vis, emission, and Fourier-transform infrared spectroscopy (FTIR) studies) supported by X-ray analysis revealed the formation [...] Read more.

We report the synthesis, characterization, and self-assembly behavior of a 4,4-Difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) dye functionalized at the meso-position with a butyric acid group. Various spectroscopic investigations (UV-Vis, emission, and Fourier-transform infrared spectroscopy (FTIR) studies) supported by X-ray analysis revealed the formation of self-assembled structures in the solid state with translationally stacked BODIPY units driven by hydrogen bonding between the carboxyl groups. Full article

(This article belongs to the Special Issue Self-Assembled Supramolecular Polymers via Strong H Bonding)

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10 pages, 4175 KiB

Open AccessArticle

Aging Behavior and Precipitation Analysis of Cu-Ni-Co-Si Alloy

by Xiangpeng Xiao, Jian Huang, Jinshui Chen, Hai Xu, Zhao Li and Jianbo Zhang

Crystals 2018, 8(11), 435; https://doi.org/10.3390/cryst8110435 - 20 Nov 2018

Cited by 14 | Viewed by 4315

Abstract

Cu-Ni-Si alloy with a different Co content was prepared by inductive melting and hot rolling. The alloy was solution treated at 950 °C for 1.5 h and aged at 450 °C, 500 °C, and 550 °C for different times. The phase diagram calculation [...] Read more.

Cu-Ni-Si alloy with a different Co content was prepared by inductive melting and hot rolling. The alloy was solution treated at 950 °C for 1.5 h and aged at 450 °C, 500 °C, and 550 °C for different times. The phase diagram calculation and transmission electron microscopy was used to investigate the effect of Co addition on the aging precipitation behavior of the Cu-Ni-Si alloy. The phase transformation kinetics equation was calculated as well. The results show that, with the increase of aging temperature, the two-phase region of Fcc + Ni₂Si in the Cu-Ni-Si ternary diagram would get wider. Some Ni_xSi_y phases would also form in the Cu-rich isothermal section. The addition of Co would replace part of Ni to form the (Ni, Co)₂Si phase, which inhibits the spinodal decomposition process of the Cu-Ni-Si alloy during the aging process. The precipitated phase of the Cu-Ni-Si alloy with a high content of the Co element is more likely to grow with the extension of aging time. The phase transformation kinetic equations of the Cu-Ni-Si alloy at 450 °C and 500 °C showed good agreement with the experimental results. Furthermore, it can be seen from the precipitation kinetic curve the addition of the Co element accelerates precipitation in the aging process. Full article

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11 pages, 3436 KiB

Open AccessArticle

From Initial Hit to Crystal Optimization with Microseeding of Human Carbonic Anhydrase IX—A Case Study for Neutron Protein Crystallography

by Katarina Koruza, Bénédicte Lafumat, Maria Nyblom, Wolfgang Knecht and Zoë Fisher

Crystals 2018, 8(11), 434; https://doi.org/10.3390/cryst8110434 - 20 Nov 2018

Cited by 5 | Viewed by 7877

Abstract

Human carbonic anhydrase IX (CA IX) is a multi-domain membrane protein that is therefore difficult to express or crystalize. To prepare crystals that are suitable for neutron studies, we are using only the catalytic domain of CA IX with six surface mutations, named [...] Read more.

Human carbonic anhydrase IX (CA IX) is a multi-domain membrane protein that is therefore difficult to express or crystalize. To prepare crystals that are suitable for neutron studies, we are using only the catalytic domain of CA IX with six surface mutations, named surface variant (SV). The crystallization of CA IX SV, and also partly deuterated CA IX SV, was enabled by the use of microseed matrix screening (MMS). Only three drops with crystals were obtained after initial sparse matrix screening, and these were used as seeds in subsequent crystallization trials. Application of MMS, commercial screens, and refinement resulted in consistent crystallization and diffraction-quality crystals. The crystallization protocols and strategies that resulted in consistent crystallization are presented. These results demonstrate not only the use of MMS in the growth of large single crystals for neutron studies with defined conditions, but also that MMS enabled re-screening to find new conditions and consistent crystallization success. Full article

(This article belongs to the Special Issue Biological Crystallization)

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9 pages, 2926 KiB

Open AccessArticle

Soft X-ray Absorption Spectroscopy Study of Spin Crossover Fe-Compounds: Persistent High Spin Configurations under Soft X-ray Irradiation

by Ahmed Yousef Mohamed, Minji Lee, Kosuke Kitase, Takafumi Kitazawa, Jae-Young Kim and Deok-Yong Cho

Crystals 2018, 8(11), 433; https://doi.org/10.3390/cryst8110433 - 19 Nov 2018

Cited by 11 | Viewed by 5521

Abstract

Metal-organic complex exhibiting spin crossover (SCO) behavior has drawn attention for its functionality as a nanoscale spin switch. The spin states in the metal ions can be tuned by external stimuli such as temperature or light. This article demonstrates a soft X-ray–induced excited [...] Read more.

Metal-organic complex exhibiting spin crossover (SCO) behavior has drawn attention for its functionality as a nanoscale spin switch. The spin states in the metal ions can be tuned by external stimuli such as temperature or light. This article demonstrates a soft X-ray–induced excited spin state trapping (SOXEISST) effect in Hofmann-like SCO coordination polymers of Fe^II(4-methylpyrimidine)₂[Au(CN)₂]₂ and Fe^II(pyridine)₂[Ni(CN)₄]. A soft X-ray absorption spectroscopy (XAS) study on these polymers showed that the high spin configuration (HS; S = 2) was prevalent in Fe²⁺ ions during the measurement even at temperatures much lower than the critical temperatures (>170 K), manifesting HS trapping due to the X-ray irradiation. This is in strong contrast to the normal SCO behavior observed in Fe^II(1,10-phenanthroline)₂(NCS)₂, implying that the structure of the ligand chains in the polymers with relatively loose Fe-N coordination might allow a structural adaptation to stabilize the metastable HS state under the soft X-ray irradiation. Full article

(This article belongs to the Special Issue Synthesis and Applications of New Spin Crossover Compounds)

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9 pages, 2948 KiB

Open AccessArticle

Fabrication of Novel ZIF-8@BiVO₄ Composite with Enhanced Photocatalytic Performance

by Yun-hui Si, Ya-yun Li, Yu Xia, Shao-ke Shang, Xin-bo Xiong, Xie-rong Zeng and Ji Zhou

Crystals 2018, 8(11), 432; https://doi.org/10.3390/cryst8110432 - 19 Nov 2018

Cited by 33 | Viewed by 6664

Abstract

In this work, a novel metal-organic framework (MOF) and BiVO₄ (BVO) composite photocatalyst was successfully synthesized by an in-situ growth method. The characterization of obtained samples was done by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, N₂ adsorption, and photoluminescence [...] Read more.

In this work, a novel metal-organic framework (MOF) and BiVO₄ (BVO) composite photocatalyst was successfully synthesized by an in-situ growth method. The characterization of obtained samples was done by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, N₂ adsorption, and photoluminescence spectroscopy. The photocatalytic performance of ZIF-8@BiVO₄ composite was evaluated by the degradation of methylene blue (MB) under simulated visible light irradiation. Compared with the mixture of BVO and ZIF-8, the composite photocatalyst exhibited superior photodegradation efficiency, which could be attributed to the synergistic effect between BVO and ZIF-8. The reduced recombination of photogenerated electrons and holes was considered to be an important reason for the enhancement of photocatalytic performance. This design demonstrates a rational method to improve the photocatalytic performance by combining photocatalysts with MOFs. Full article

(This article belongs to the Special Issue Synthesis, Modeling, Characterization and Applications of Metal-Organic Frameworks)

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18 pages, 3238 KiB

Open AccessCommunication

Filling Tricompartmental Ligands with Gd^III and Zn^II Ions: Some Structural and MRI Studies

by Julio Corredoira-Vázquez, Matilde Fondo, Jesús Sanmartín-Matalobos, Pablo Taboada and Ana M. García-Deibe

Crystals 2018, 8(11), 431; https://doi.org/10.3390/cryst8110431 - 16 Nov 2018

Cited by 2 | Viewed by 3214

Abstract

Here we report the synthesis and characterization of a mononuclear gadolinium complex (Gd) and two heteronuclear Zn-Gd complexes (ZnGd and Zn₂Gd), which contain two similar three-armed ligands that display an external compartment suitable for lanthanoid ions, and [...] Read more.

Here we report the synthesis and characterization of a mononuclear gadolinium complex (Gd) and two heteronuclear Zn-Gd complexes (ZnGd and Zn₂Gd), which contain two similar three-armed ligands that display an external compartment suitable for lanthanoid ions, and two internal compartments adequate for zinc (II) ions [H₃L′ = (2-(3-formyl-2-hydroxy-5-methyl phenyl)-1,3-bis[4 -(3-formyl-2-hydroxy-5-methylphenyl)-3-azabut-3-enyl]-1,3-imidazolidine; H₃L = 2-(5-bromo-2-hydroxy-3-methoxyphenyl)-1,3-bis[4-(5-bromo-2-hydroxy-3-methoxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine]. The synthetic methods used were varied, but the use of a metalloligand, [Zn₂(L)AcO], as starting material was the key factor to obtain the heterotrinuclear complex Zn₂Gd. The structure of the precursor dinuclear zinc complex is mostly preserved in this complex, since it is based on a compact [Zn₂Ln(L)(OH)(H₂O)]³⁺ residue, with a µ₃-OH bridge between the three metal centers, which are almost forming an isosceles triangle. The asymmetric spatial arrangement of other ancillary ligands leads to chirality, what contrasts with the totally symmetric mononuclear gadolinium complex Gd. These features were confirmed by the crystal structures of both complexes. Despite the presence of the bulky compartmental Schiff base ligand, the chiral heterotrinuclear complex forms an intricate network which is predominately expanded in two dimensions, through varied H-bonds that connect not only the ancillary ligands, but also the nitrate counterions and some solvated molecules. In addition, some preliminary magnetic resonance imaging (MRI) studies have been made to determine the relaxivities of the three gadolinium complexes, with apparently improved T₁ and T₂ relaxivities with increasing zinc nuclearity, since both transversal and longitudinal relaxivities appear to enhance in the sequence Gd < ZnGd < Zn₂Gd. Full article

(This article belongs to the Special Issue Selected Papers from "The 1st International Electronic Conference on Crystals")

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18 pages, 2037 KiB

Open AccessReview

Recent Advances in and New Perspectives on Crystalline Silicon Solar Cells with Carrier-Selective Passivation Contacts

by Cao Yu, Shengzhi Xu, Jianxi Yao and Shuwei Han

Crystals 2018, 8(11), 430; https://doi.org/10.3390/cryst8110430 - 15 Nov 2018

Cited by 58 | Viewed by 9837

Abstract

Crystalline silicon (c-Si) is the dominating photovoltaic technology today, with a global market share of about 90%. Therefore, it is crucial for further improving the performance of c-Si solar cells and reducing their cost. Since 2014, continuous breakthroughs have been achieved in the [...] Read more.

Crystalline silicon (c-Si) is the dominating photovoltaic technology today, with a global market share of about 90%. Therefore, it is crucial for further improving the performance of c-Si solar cells and reducing their cost. Since 2014, continuous breakthroughs have been achieved in the conversion efficiencies of c-Si solar cells, with a current record of 26.6%. The great efficiency boosts originate not only from the materials, including Si wafers, emitters, passivation layers, and other functional thin films, but also from novel device structures and an understanding of the physics of solar cells. Among these achievements, the carrier-selective passivation contacts are undoubtedly crucial. Current carrier-selective passivation contacts can be realized either by silicon-based thin films or by elemental and/or compound thin films with extreme work functions. The current research and development status, as well as the future trends of these passivation contact materials, structures, and corresponding high-efficiency c-Si solar cells will be summarized. Full article

(This article belongs to the Special Issue Advances in Thin Film Solar Cells)

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15 pages, 33681 KiB

Open AccessArticle

Structural, Electronic, Magnetic, Mechanic and Thermodynamic Properties of the Inverse Heusler Alloy Ti₂NiIn Under Pressure

by Tie Yang, Jieting Cao and Xiaotian Wang

Crystals 2018, 8(11), 429; https://doi.org/10.3390/cryst8110429 - 15 Nov 2018

Cited by 23 | Viewed by 4269

Abstract

Structural, electronic, magnetic and mechanic properties of the inverse Heusler alloy Ti₂NiIn under different pressure are systematically studied with density functional theory (DFT). The equilibrium lattice constant and electronic band structure at null pressure are obtained to be consistent with previous [...] Read more.

Structural, electronic, magnetic and mechanic properties of the inverse Heusler alloy Ti₂NiIn under different pressure are systematically studied with density functional theory (DFT). The equilibrium lattice constant and electronic band structure at null pressure are obtained to be consistent with previous work. Under currently applied static pressure from 0 GPa to 50 GPa, it is found that the half-metallicity of the material is maintained and the total magnetic moment (M_t) is kept at 3 µ_B, which obeys the Slater–Pauling rule, M_t = Z_t − 18, where Z_t is the total number of valence electrons. Besides, the effect of the tetragonal distortion was studied and it is found that the magnetic property of Ti₂NiIn is almost unchanged. Several mechanical parameters are calculated including three elastic constants, bulk modulus B, Young’s modulus E, and shear modulus S and the mechanical stability is examined accordingly. Furthermore, the thermodynamic properties, such as the heat capacity C_V, the thermal expansion coefficient α, the Grüneisen constant γ and the Debye temperature Θ_D, are computed by using the quasi-harmonic Debye model within the same pressure range at a series of temperature from 0 to 1500 K. This theoretical study provides detailed information about the inverse Heusler compound Ti₂NiIn from different aspects and can further lead some insight on the application of this material. Full article

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16 pages, 6414 KiB

Open AccessArticle

Influence of Pressure on the Mechanical and Electronic Properties of Wurtzite and Zinc-Blende GaN Crystals

by Hongbo Qin, Tianfeng Kuang, Xinghe Luan, Wangyun Li, Jing Xiao, Ping Zhang, Daoguo Yang and Guoqi Zhang

Crystals 2018, 8(11), 428; https://doi.org/10.3390/cryst8110428 - 14 Nov 2018

Cited by 4 | Viewed by 5515

Abstract

The mechanical and electronic properties of two GaN crystals, wurtzite and zinc-blende GaN, under various hydrostatic pressures were investigated using first principles calculations. The results show that the lattice constants of the two GaN crystals calculated in this study are close to previous [...] Read more.

The mechanical and electronic properties of two GaN crystals, wurtzite and zinc-blende GaN, under various hydrostatic pressures were investigated using first principles calculations. The results show that the lattice constants of the two GaN crystals calculated in this study are close to previous experimental results, and the two GaN crystals are stable under hydrostatic pressures up to 40 GPa. The pressure presents extremely similar trend effect on the volumes of unit cells and average Ga-N bond lengths of the two GaN crystals. The bulk modulus increases while the shear modulus decreases with the increase in pressure, resulting in the significant increase of the ratios of bulk moduli to shear moduli for the two GaN polycrystals. Different with the monotonic changes of bulk and shear moduli, the elastic moduli of the two GaN polycrystals may increase at first and then decrease with increasing pressure. The two GaN crystals are brittle materials at zero pressure, while they may exhibit ductile behaviour under high pressures. Moreover, the increase in pressure raises the elastic anisotropy of GaN crystals, and the anisotropy factors of the two GaN single crystals are quite different. Different with the obvious directional dependences of elastic modulus, shear modulus and Poisson’s ratio of the two GaN single crystals, there is no anisotropy for bulk modulus, especially for that of zinc-blende GaN. Furthermore, the band gaps of GaN crystals increase with increasing pressure, and zinc-blende GaN has a larger pressure coefficient. To further understand the pressure effect on the band gap, the band structure and density of states (DOSs) of GaN crystals were also analysed in this study. Full article

(This article belongs to the Special Issue Advances in Structural and Compositional Characterization for the Development of Wide Bandgap Semiconductors)

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10 pages, 3363 KiB

Open AccessArticle

Evaluation of the Effect of Nd Content and Extrusion Process on Thermal Conductivity of Mg-Mn-Zn-Nd Alloys

by Ying-Long Zhou, Jie Liu, Dong-Mei Luo and Dong-Chu Chen

Crystals 2018, 8(11), 427; https://doi.org/10.3390/cryst8110427 - 14 Nov 2018

Cited by 2 | Viewed by 2706

Abstract

The thermal conductivity of the Mg-1Mn-2Zn-xNd alloys (x = 0.5, 1.0, 1.5 wt. %) was studied for the potential applications of heat dissipation. The phase constituents were examined by X-ray diffraction analysis, and the microstructure was observed by light and scanning electron microscopes. [...] Read more.

The thermal conductivity of the Mg-1Mn-2Zn-xNd alloys (x = 0.5, 1.0, 1.5 wt. %) was studied for the potential applications of heat dissipation. The phase constituents were examined by X-ray diffraction analysis, and the microstructure was observed by light and scanning electron microscopes. The thermal conductivity of the Mg alloys was gauged at room temperature using laser flash method. The experimental results indicate that the thermal conductivity of both the cast and extruded Mg alloys decreases slowly with Nd content, and the extrusion process remarkably reduces the grain sizes and thermal conductivity of the Mg alloys. The thermal conductivity of cast Mg-1Mn-2Zn-xNd alloys exceeds the required critical value (100 W/(m·k)) for the cast Mg alloys. Among them, the cast Mg-1Mn-2Zn-1Nd alloy has great potential to be a good candidate of heat dissipation materials due to its good combination of thermal and mechanical properties. Full article

(This article belongs to the Special Issue Microstructure and Physical Properties of Magnesium Alloys and Composites)

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9 pages, 2645 KiB

Open AccessArticle

Electric and Optical Properties of Pb(Er_1/2Nb_1/2)-Pb(Mg_1/3Nb_1/3)-PbTiO₃ Crystals

by Wei Zhao, Zengzhe Xi, Pinyang Fang, Xiaojuan Li, Wei Long, Aiguo He, Ying Li and Yuanmin Zhang

Crystals 2018, 8(11), 426; https://doi.org/10.3390/cryst8110426 - 14 Nov 2018

Cited by 4 | Viewed by 2839

Abstract

New ferroelectric crystals Pb(Er_1/2Nb_1/2)-Pb(Mg_1/3Nb_1/3)O-PbTiO₃ (PEN-PMN-PT) were grown by using the flux method. Phase structure of the crystals was described by the X-ray diffraction analysis. Dielectric, ferroelectric and optical properties of the PEN-PMN-PT crystals were [...] Read more.

New ferroelectric crystals Pb(Er_1/2Nb_1/2)-Pb(Mg_1/3Nb_1/3)O-PbTiO₃ (PEN-PMN-PT) were grown by using the flux method. Phase structure of the crystals was described by the X-ray diffraction analysis. Dielectric, ferroelectric and optical properties of the PEN-PMN-PT crystals were investigated systematically. Higher Curie temperature (T_c ~ 291 °C) and larger coercive field (E_c ~ 17.6 kV/cm) for the 40PEN-13PMN-47PT can be obtained, respectively, compared with those of the PMN-PT. Moreover, strong green and red emissions can be excited by using the 980 nm laser. The PEN-PMN-PT crystals with these performances have some promising applications in the electromechanical and optical devices. Full article

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12 pages, 5066 KiB

Open AccessArticle

Enhanced High Voltage Performance of Chlorine/Bromine Co-Doped Lithium Nickel Manganese Cobalt Oxide

by Huali Zhu, Qifeng Li, Xiaolong Gong, Kaifeng Cao and Zhaoyong Chen

Crystals 2018, 8(11), 425; https://doi.org/10.3390/cryst8110425 - 9 Nov 2018

Cited by 12 | Viewed by 5594

Abstract

The chlorine (Cl) and bromine (Br) co-doped lithium nickel manganese cobalt oxide (LiNi_1/3Co_1/3Mn_1/3O₂) was successfully synthesized by the molten salt method. The synthesized LiNi_1/3Co_1/3Mn_1/3O₂ compound demonstrates spherical morphology, [...] Read more.

The chlorine (Cl) and bromine (Br) co-doped lithium nickel manganese cobalt oxide (LiNi_1/3Co_1/3Mn_1/3O₂) was successfully synthesized by the molten salt method. The synthesized LiNi_1/3Co_1/3Mn_1/3O₂ compound demonstrates spherical morphology, which is formed by aggregated spherical-like or polygon primary particles. Halogen substitution would contribute to the growth of the primary particles. The LiNi_1/3Co_1/3Mn_1/3O₂ compound has the typical hexagonal layered structure, and no impurity phase is detected. The surface oxidation state of the compound is improved after Cl and Br substitution. Moreover, the Cl and Br co-doped LiNi_1/3Co_1/3Mn_1/3O₂ compound exhibits both improved rate capacity and cycle stability at a high voltage (4.6 V) compared with the pristine LiNi_1/3Co_1/3Mn_1/3O₂. The initial discharge capacities of Cl and Br co-doped LiNi_1/3Co_1/3Mn_1/3O₂ are 208.9 mAh g⁻¹, 200.6 mAh g⁻¹, 188.2 mAh g⁻¹, 173.3 mAh g⁻¹, and 157.1 mAh g⁻¹ at the corresponding rates of 0.1C, 0.2C, 0.5C, 1C, and 3C respectively. The capacity retention at 1C after 50 cycles is increased from 81.1% to 93.2% by co-doping. The better contact between the electroactive particles of the electrode and the smaller resistance enhance the electric conductivity of the Cl and Br co-doped LiNi_1/3Co_1/3Mn_1/3O₂ cathode. The synthesized LiNi_1/3Co_1/3Mn_1/3O₂ is a promising cathode material for a high-power and large-capacity lithium-ion battery. Full article

(This article belongs to the Special Issue New Materials for Li-Ion Batteries)

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11 pages, 4746 KiB

Open AccessArticle

Synthesis, Crystal Structure, and Properties of a Zn(II) Coordination Polymer Based on a Difunctional Ligand Containing Triazolyl and Carboxyl Groups

by Jia-Le Li, Wei-Dong Li, Zi-Wei He, Shuai-Shuai Han and Shui-Sheng Chen

Crystals 2018, 8(11), 424; https://doi.org/10.3390/cryst8110424 - 9 Nov 2018

Cited by 3 | Viewed by 3232

Abstract

A new compound, namely, [Zn(L)₂]_n (1) was obtained by the reaction of 2-methyl-4-(4H-1,2,4-triazol-4-yl) benzoic acid (HL) with ZnSO₄·7H₂O, and the compound was characterized by single-crystal X-ray diffraction, infrared spectroscopy, elemental analysis, powder [...] Read more.

A new compound, namely, [Zn(L)₂]_n (1) was obtained by the reaction of 2-methyl-4-(4H-1,2,4-triazol-4-yl) benzoic acid (HL) with ZnSO₄·7H₂O, and the compound was characterized by single-crystal X-ray diffraction, infrared spectroscopy, elemental analysis, powder X-ray diffraction (PXRD), and thermogravimetric analysis. The linear HL ligands were deprotonated to be L⁻ anions and act as two-connectors to link Zn²⁺ to form a two-dimensional (2D) lay structure with (4, 4) topology. The large vacancy of 2D framework allows another layer structure to interpenetrate, resulting in the formation of 2D + 2D → 2D parallel interpenetration in 1. The weak interactions, such as hydrogen bonding and π–π stacking interactions, connect the adjacent 2D layers into a three-dimensional (3D) coordination polymer. The solid-state UV-visible spectroscopy and luminescent property have also been studied. Full article

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3 pages, 156 KiB

Open AccessEditorial

Carbonates

by Linda Pastero

Crystals 2018, 8(11), 423; https://doi.org/10.3390/cryst8110423 - 8 Nov 2018

Cited by 1 | Viewed by 2361

Abstract

Although the minerals belonging to the carbonate group are a widely discussed subject, their relevance remains unchanged due to their many applications in a wide range of disciplines, from mineralogy, geochemistry and geology, to biology, medicine, industry and waste remediation. [...] Full article

16 pages, 667 KiB

Open AccessEditor’s ChoiceReview

Peculiarities of Protein Crystal Nucleation and Growth

by Christo N. Nanev

Crystals 2018, 8(11), 422; https://doi.org/10.3390/cryst8110422 - 8 Nov 2018

Cited by 11 | Viewed by 5178

Abstract

This paper reviews investigations on protein crystallization. It aims to present a comprehensive rather than complete account of recent studies and efforts to elucidate the most intimate mechanisms of protein crystal nucleation. It is emphasized that both physical and biochemical factors are at [...] Read more.

This paper reviews investigations on protein crystallization. It aims to present a comprehensive rather than complete account of recent studies and efforts to elucidate the most intimate mechanisms of protein crystal nucleation. It is emphasized that both physical and biochemical factors are at play during this process. Recently-discovered molecular scale pathways for protein crystal nucleation are considered first. The bond selection during protein crystal lattice formation, which is a typical biochemically-conditioned peculiarity of the crystallization process, is revisited. Novel approaches allow us to quantitatively describe some protein crystallization cases. Additional light is shed on the protein crystal nucleation in pores and crevices by employing the so-called EBDE method (equilibration between crystal bond and destructive energies). Also, protein crystal nucleation in solution flow is considered. Full article

(This article belongs to the Special Issue Biological Crystallization)

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13 pages, 5205 KiB

Open AccessArticle

Optical Detection of Green Emission for Non-Uniformity Film in Flat Panel Displays

by Fu-Ming Tzu and Jung-Hua Chou

Crystals 2018, 8(11), 421; https://doi.org/10.3390/cryst8110421 - 8 Nov 2018

Cited by 2 | Viewed by 3555

Abstract

Among colours, the green colour has the most sensitivity in human vision so that green colour defects on displays can be effortlessly perceived by a photopic eye with the most intensity in the wavelength 555 nm of the spectrum. With the market moving [...] Read more.

Among colours, the green colour has the most sensitivity in human vision so that green colour defects on displays can be effortlessly perceived by a photopic eye with the most intensity in the wavelength 555 nm of the spectrum. With the market moving forward to high resolution, displays can have resolutions of 10 million pixels. Therefore, the method of detecting the appearance of the panel using ultra-high resolutions in TFT-LCD is important. The machine vision associated with transmission chromaticity spectrometer that quantises the defects are explored, such as blackening and whitening. The result shows the significant phenomena to recognize the non-uniformity of film-related chromatic variation. In contrast, the quantitative assessment illustrates that the just noticeable difference (JND) of chromaticity CIE xyY at 0.001 is the measuring sensitivity for the chromatic variables (x, y), whereas JND is a perceptible threshold for a colour difference metric. Moreover, an optical device associated with a ¹⁹⁸Hg discharge lamp calibrates the spectrometer accuracy. Full article

(This article belongs to the Special Issue Thin Film Transistor)

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10 pages, 4913 KiB

Open AccessArticle

Enhancing the Light-Extraction Efficiency of AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes by Optimizing the Diameter and Tilt of the Aluminum Sidewall

by Yung-Min Pai, Chih-Hao Lin, Chun-Fu Lee, Chun-Peng Lin, Cheng-Huan Chen, Hao-Chung Kuo and Zhi-Ting Ye

Crystals 2018, 8(11), 420; https://doi.org/10.3390/cryst8110420 - 8 Nov 2018

Cited by 18 | Viewed by 5620

Abstract

To realize high-efficiency AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs), enhancing their light-extraction efficiency (LEE) is crucial. This paper proposes an aluminum-based sidewall reflector structure that could replace the conventional ceramic-based packaging method. We design optimization simulations and experimental results demonstrated the light power output [...] Read more.

To realize high-efficiency AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs), enhancing their light-extraction efficiency (LEE) is crucial. This paper proposes an aluminum-based sidewall reflector structure that could replace the conventional ceramic-based packaging method. We design optimization simulations and experimental results demonstrated the light power output could be enhanced 18.38% of DUV-LEDs packaged with the aluminum-based sidewall. Full article

(This article belongs to the Special Issue GaN-Based Optoelectronic Materials and Light Emitting Devices)

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7 pages, 3506 KiB

Open AccessArticle

Fabrication and Optical Properties of 2at.%Yb:LuYAG Mixed Crystal through Nanocrystalline Powders

by Ding Zhou, Meiqi Yang, Jiayue Xu, Yijian Jiang, Yunfeng Ma and Ying Shi

Crystals 2018, 8(11), 419; https://doi.org/10.3390/cryst8110419 - 8 Nov 2018

Cited by 1 | Viewed by 3370

Abstract

Ytterbium doped Lu_1.5Y_1.5Al₅O₁₂ (LuYAG) nanocrystalline powders were synthesized by a wet chemical mixed precipitant co-precipitation (MPP) method, and then the mixed crystal of Yb:LuYAG was grown in an optical floating zone (OFZ) furnace at the speed [...] Read more.

Ytterbium doped Lu_1.5Y_1.5Al₅O₁₂ (LuYAG) nanocrystalline powders were synthesized by a wet chemical mixed precipitant co-precipitation (MPP) method, and then the mixed crystal of Yb:LuYAG was grown in an optical floating zone (OFZ) furnace at the speed of 6–10 mm/h, using a [111] oriented YAG seed crystal. The transmittance of the polished LuYAG crystal is close to the ideal value of LuAG or YAG. The X-ray rocking curve shows complete symmetry and the full width at half maximum (FWHM) is 10 arc-second, indicating the good quality of as grown Yb:LuYAG multicomponent garnet crystal. The thermal luminescent spectrum at room temperature shows four deep energy traps at around 1–1.3 eV. X-ray excited luminesce (XEL) spectra is measured to characterize the existence of Lu_Al or Y_Al shadow defects in the bulk single crystal. The emission peak at around 320 nm indicates that the LuYAG crystal prepared by OFZ have lower concentrations of antisite defects (AD) with respect to its Czochralski counterpart. Full article

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5 pages, 2726 KiB

Open AccessArticle

Fabrication of GaOx Confinement Structure for InGaN Light Emitter Applications

by Yi-Yun Chen, Yuan-Chang Jhang, Chia-Jung Wu, Hsiang Chen, Yung-Sen Lin and Chia-Feng Lin

Crystals 2018, 8(11), 418; https://doi.org/10.3390/cryst8110418 - 7 Nov 2018

Cited by 1 | Viewed by 2833

Abstract

An indium gallium nitride (InGaN) light-emitting diode (LED) with an embedded porous GaN reflector and a current confined aperture is presented in this study. Eight pairs of n⁺-GaN:Si/GaN in stacked structure are transformed into a conductive, porous GaN/GaN reflector through an [...] Read more.

An indium gallium nitride (InGaN) light-emitting diode (LED) with an embedded porous GaN reflector and a current confined aperture is presented in this study. Eight pairs of n⁺-GaN:Si/GaN in stacked structure are transformed into a conductive, porous GaN/GaN reflector through an electrochemical wet-etching process. Porous GaN layers surrounding the mesa region were transformed into insulating GaOx layers in a reflector structure through a lateral photoelectrochemical (PEC) oxidation process. The electroluminescence emission intensity was localized at the central mesa region by forming the insulating GaOx layers in a reflector structure as a current confinement aperture structure. The PEC-LED structure with a porous GaN reflector and a current-confined aperture surrounded by insulating GaOx layers has the potential for nitride-based resonance cavity light source applications. Full article

(This article belongs to the Special Issue Functional Oxide Based Thin-Film Materials)

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13 pages, 11980 KiB

Open AccessArticle

Effect of Additives on the Morphologies of Hydrothermal Products Prepared from Semi-Dry Desulfurization Residues

by Lixia Li, Haiqing Hao and Zhitao Yuan

Crystals 2018, 8(11), 417; https://doi.org/10.3390/cryst8110417 - 6 Nov 2018

Cited by 3 | Viewed by 3768

Abstract

For effective utilization of the residues, calcium sulfate whiskers were prepared from semi-dry desulfurization residues by hydrothermal synthesis reactions. Aiming at collecting the products with a long length and large aspect ratio, the additives, including sodium oleate, sodium dodecyl benzene sulfonate (SDBS), and [...] Read more.

For effective utilization of the residues, calcium sulfate whiskers were prepared from semi-dry desulfurization residues by hydrothermal synthesis reactions. Aiming at collecting the products with a long length and large aspect ratio, the additives, including sodium oleate, sodium dodecyl benzene sulfonate (SDBS), and sodium citrate, were added to control the growth of the crystal. Compared with no additives, whiskers with relatively a longer length and larger aspect ratio could be obtained in the presence of sodium oleate or SDBS. The sodium citrate made the whiskers thicker and shorter. Then, the effects of the additives on crystal growth and the morphology of the hydrothermal products were investigated with the aid of X-ray diffraction (XRD) patterns and molecular dynamics simulations. According to the results of XRD, the diffraction intensity of the crystal face (400) increased under the influence of sodium oleate, promoting crystal growth along the c-axis. The molecular structures of the corresponding faces were built based on the strong peaks shown in the XRD patterns. The atomic distribution on the computed crystal faces was presented. The interaction energies on different faces were calculated to illustrate the different adsorption configurations of the additives. Among the calculated faces, the interaction energies on (400) were both most negative for sodium oleate and SDBS. Therefore, sodium oleate and SDBS preferred to adsorb on (400). As a result, the growth of (400) was thus inhibited and the crystal grew along the c-axis. Compared with sodium oleate and SDBS, the lowest adsorption energy of sodium citrate on the face (310) indicated that sodium citrate has no positive effect on the directional growth of the crystal parallel to c-axis. The molecular simulation results were virtually identical to the crystal faces analysis results. Full article

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12 pages, 70692 KiB

Open AccessArticle

Non-Local Game of Life in 2D Quasicrystals

by Fang Fang, Sinziana Paduroiu, Dugan Hammock and Klee Irwin

Crystals 2018, 8(11), 416; https://doi.org/10.3390/cryst8110416 - 6 Nov 2018

Cited by 3 | Viewed by 7289

Abstract

On a two-dimensional quasicrystal, a Penrose tiling, we simulate for the first time a game of life dynamics governed by non-local rules. Quasicrystals have inherently non-local order since any local patch, the emperor, forces the existence of a large number of tiles at [...] Read more.

On a two-dimensional quasicrystal, a Penrose tiling, we simulate for the first time a game of life dynamics governed by non-local rules. Quasicrystals have inherently non-local order since any local patch, the emperor, forces the existence of a large number of tiles at all distances, the empires. Considering the emperor and its local patch as a quasiparticle, in this case a glider, its empire represents its field and the interaction between quasiparticles can be modeled as the interaction between their empires. Following a set of rules, we model the walk of life in different setups and we present examples of self-interaction and two-particle interactions in several scenarios. This dynamic is influenced by both higher dimensional representations and local choice of hinge variables. We discuss our results in the broader context of particle physics and quantum field theory, as a first step in building a geometrical model that bridges together higher dimensional representations, quasicrystals and fundamental particles interactions. Full article

(This article belongs to the Special Issue Structure and Properties of Quasicrystals)

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9 pages, 1391 KiB

Open AccessArticle

New Iron(II) Spin Crossover Complexes with Unique Supramolecular Networks Assembled by Hydrogen Bonding and Intermetallic Bonding

by Takashi Kosone, Itaru Tomori, Daisuke Akahoshi, Toshiaki Saito and Takafumi Kitazawa

Crystals 2018, 8(11), 415; https://doi.org/10.3390/cryst8110415 - 5 Nov 2018

Cited by 4 | Viewed by 3048

Abstract

Two spin crossover (SCO) coordination polymers assembled by combining Fe^II octahedral ion, 4-cyanopyridine (4-CNpy) and [Au(CN)₂]⁻ liner unit are described. These compounds, Fe(4-CNpy)₂[Au(CN)₂]₂·1/2(4-CNpy) (1a) and {Fe(4-CNpy)₂[Au(CN)₂]₂ [...] Read more.

Two spin crossover (SCO) coordination polymers assembled by combining Fe^II octahedral ion, 4-cyanopyridine (4-CNpy) and [Au(CN)₂]⁻ liner unit are described. These compounds, Fe(4-CNpy)₂[Au(CN)₂]₂·1/2(4-CNpy) (1a) and {Fe(4-CNpy)₂[Au(CN)₂]₂}-{Fe(H₂O)₂[Au(CN)₂]₂} (1b), present quite different supramolecular networks that show different magnetic behaviors. Compound 1a crystallizes in the centrosymmetric space group Pbcn. The asymmetric unit contains two 4-CNpy, one type of Fe²⁺, and two types of crystallographically distinct [Au(CN)₂]⁻ units which form Hofmann-like two dimensional layer structures with guest spaces. The layers are combined with another layer by strong gold-gold intermetalic interactions. Compound 1b crystallizes in the centrosymmetric space group Pnma. The bent bismonodentate [Au^I(CN)₂] units and Fe^II ions form a complicated interpenetrated three dimensional structure. In addition, 1b exhibits ferromagnetic interaction. Full article

(This article belongs to the Special Issue Synthesis and Applications of New Spin Crossover Compounds)

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12 pages, 2272 KiB

Open AccessCommunication

Synthesis and Fluorescence Properties of a Structurally Characterized Hetero-Hexanuclear Zn(II)-La(III) Salamo-Like Coordination Compound Containing Auxiliary Ligands

by Wen-Ting Guo, Ling-Zhi Liu, Meng Yu, Fei Wang, Jian-Chun Ma and Wen-Kui Dong

Crystals 2018, 8(11), 414; https://doi.org/10.3390/cryst8110414 - 4 Nov 2018

Cited by 2 | Viewed by 2980

Abstract

A hetero-hexanuclear Zn(II)-La(III) coordination compound, [{(ZnL)₂La}₂(bdc)₂](NO₃)₂ (H₂bdc = terephthalic acid) has been synthesized with a symmetric Salamo-like bisoxime, and characterized by elemental analyses, IR, UV-Vis, fluorescent spectroscopy, and single-crystal X-ray diffraction analysis. [...] Read more.

A hetero-hexanuclear Zn(II)-La(III) coordination compound, [{(ZnL)₂La}₂(bdc)₂](NO₃)₂ (H₂bdc = terephthalic acid) has been synthesized with a symmetric Salamo-like bisoxime, and characterized by elemental analyses, IR, UV-Vis, fluorescent spectroscopy, and single-crystal X-ray diffraction analysis. All of the Zn(II) ions are pentacoordinated by N₂O₂ donator atoms from the (L)²⁻ unit and one oxygen atom from one terephthalate anion. The Zn(II) ions adopt trigonal bipyramidal geometries (τ_Zn1 = 0.61, τ_Zn2 = 0.56). The La(III) ions are decacoordinated in the Zn(II)-La(III) coordination compound and has a distorted bicapped square antiprism geometry. Meanwhile, the photophysical property of the Zn(II)-La(III) coordination compound was also measured and discussed. Full article

(This article belongs to the Special Issue Crystal Structures of Boron Compounds)

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3 pages, 172 KiB

Open AccessEditorial

Crystal Dislocations: Their Impact on Physical Properties of Crystals

by Peter Lagerlof

Crystals 2018, 8(11), 413; https://doi.org/10.3390/cryst8110413 - 3 Nov 2018

Cited by 4 | Viewed by 3576

Abstract

It is rare to find technical applications involving a material of any crystal structure that is not impacted by dislocations—which affect the material’s mechanical properties, interfaces, martensitic phase transformations, crystal growth, and electronic properties, to name a few. [...] Full article

(This article belongs to the Special Issue Crystal Dislocations: Their Impact on Physical Properties of Crystals)

55 pages, 32414 KiB

Open AccessReview

Metal–Organic Framework Membranes: From Fabrication to Gas Separation

by Osama Shekhah, Valeriya Chernikova, Youssef Belmabkhout and Mohamed Eddaoudi

Crystals 2018, 8(11), 412; https://doi.org/10.3390/cryst8110412 - 31 Oct 2018

Cited by 52 | Viewed by 12411

Abstract

Gas membrane-based separation is considered one of the most effective technologies to address energy efficiency and large footprint challenges. Various classes of advanced materials, including polymers, zeolites, porous carbons, and metal–organic frameworks (MOFs) have been investigated as potential suitable candidates for gas membrane-based [...] Read more.

Gas membrane-based separation is considered one of the most effective technologies to address energy efficiency and large footprint challenges. Various classes of advanced materials, including polymers, zeolites, porous carbons, and metal–organic frameworks (MOFs) have been investigated as potential suitable candidates for gas membrane-based separations. MOFs possess a uniquely tunable nature in which the pore size and environment can be controlled by connecting metal ions (or metal ion clusters) with organic linkers of various functionalities. This unique characteristic makes them attractive for the fabrication of thin membranes, as both the diffusion and solubility components of permeability can be altered. Numerous studies have been published on the synthesis and applications of MOFs, as well as the fabrication of MOF-based thin films. However, few studies have addressed their gas separation properties for potential applications in membrane-based separation technologies. Here, we present a synopsis of the different types of MOF-based membranes that have been fabricated over the past decade. In this review, we start with a short introduction touching on the gas separation membrane technology. We also shed light on the various techniques developed for the fabrication of MOF as membranes, and the key challenges that still need to be tackled before MOF-based membranes can successfully be used in gas separation and implemented in an industrial setting. Full article

(This article belongs to the Special Issue MOF-Based Membranes)

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13 pages, 714 KiB

Open AccessArticle

Impurity-Induced Spin-State Crossover in La_0.8Sr_0.2Co_1−xAl_xO₃

by Ichiro Terasaki, Masamichi Ikuta, Takafumi D. Yamamoto and Hiroki Taniguchi

Crystals 2018, 8(11), 411; https://doi.org/10.3390/cryst8110411 - 31 Oct 2018

Cited by 2 | Viewed by 3103

Abstract

We have prepared a set of polycrystalline samples of La

_{0.8}

Sr

_{0.2}

Co

_{1 - x}

Al

_{x}

O

_{3}

(

0 \leq x \leq 0.2

), and have measured the magnetization as functions of temperature and magnetic field. We find that [...] Read more.

We have prepared a set of polycrystalline samples of La

_{0.8}

Sr

_{0.2}

Co

_{1 - x}

Al

_{x}

O

_{3}

(

0 \leq x \leq 0.2

), and have measured the magnetization as functions of temperature and magnetic field. We find that the average spin number per Co ion (

S_{Co}

) evaluated from the room-temperature susceptibility is around 1.2–1.3 and independent of x. However, we further find that

S_{Co}

evaluated from the saturation magnetization at 2 K is around 0.3–0.7, and decreases dramatically with x. This naturally indicates that a significant fraction of the Co

^{3 +}

ions experience a spin-state crossover from the intermediate- to low-spin state with decreasing temperature in the Al-substituted samples. This spin-state crossover also explains the resistivity and the thermopower consistently. In particular, we find that the thermopower is anomalously enhanced by the Al substitution, which can be consistently explained in terms of an extended Heikes formula. Full article

(This article belongs to the Special Issue Synthesis and Applications of New Spin Crossover Compounds)

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28 pages, 8103 KiB

Open AccessArticle

Structural and Magnetic Properties of Co‒Mn Codoped ZnO Nanoparticles Obtained by Microwave Solvothermal Synthesis

by Jacek Wojnarowicz, Myroslava Omelchenko, Jacek Szczytko, Tadeusz Chudoba, Stanisław Gierlotka, Andrzej Majhofer, Andrzej Twardowski and Witold Lojkowski

Crystals 2018, 8(11), 410; https://doi.org/10.3390/cryst8110410 - 31 Oct 2018

Cited by 24 | Viewed by 5943

Abstract

Zinc oxide nanoparticles codoped with Co²⁺ and Mn²⁺ ions (Zn_(1−x−y)Mn_xCo_yO NPs) were obtained for the first time by microwave solvothermal synthesis. The nominal content of Co²⁺ and Mn²⁺ in Zn_(1−x−y)Mn_x [...] Read more.

Zinc oxide nanoparticles codoped with Co²⁺ and Mn²⁺ ions (Zn_(1−x−y)Mn_xCo_yO NPs) were obtained for the first time by microwave solvothermal synthesis. The nominal content of Co²⁺ and Mn²⁺ in Zn_(1−x−y)Mn_xCo_yO NPs was x = y = 0, 1, 5, 10 and 15 mol % (the amount of both ions was equal). The precursors were obtained by dissolving zinc acetate dihydrate, manganese (II) acetate tetrahydrate and cobalt (II) acetate tetrahydrate in ethylene glycol. The morphology, phase purity, lattice parameters, dopants content, skeleton density, specific surface area, average particle size, average crystallite size, crystallite size distribution and magnetic properties of NPs were determined. The real content of dopants was up to 25.0% for Mn²⁺ and 80.5% for Co²⁺ of the nominal content. The colour of the samples changed from white to dark olive green in line with the increasing doping level. Uniform spherical NPs with wurtzite structure were obtained. The average size of NPs decreased from 29 nm to 21 nm in line with the increase in the dopant content. Brillouin type paramagnetism and an antiferromagnetic interaction between the magnetic ions was found for all samples, except for that with 15 mol % doping level, where a small ferromagnetic contribution was found. A review of the preparation methods of Co²⁺ and Mn²⁺ codoped ZnO is presented. Full article

(This article belongs to the Special Issue Microwave-Assisted Synthesis of Nanocrystals and Nanostructures)

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