Modification Of Crystal Structure Research Articles

Structural and piezoelectric properties evolution induced by cobalt doping and cobalt/niobium co-doping in BaTiO3

Lead–zirconate–titanate PbZr(1−x)TixO3 (PZT), materials for piezoelectric applications are the dominant piezoceramics since their properties are high. However PZTs need to be substituted by safer materials due to health and environmental problems of lead. In this work, the crystal structure modifications of BaTiO3 induced by cobalt doping and niobium/cobalt co-doping were investigated in the range 0.1–25at%. Low Co and Co/Nb doping level significantly improve piezoelectric properties of BaTiO3. The piezoelectric constant, obtained for BaTiO3 doped with 0.075at% of Cobalt (d33=200pC/N), is twice of that measured for pure BaTiO3. At high doping concentration, the structure of BaTi1−x CoxO3 and BaTi1−x CoxNbxO3 change from tetragonal to hexagonal while BaTi1−x CoxNb2xO3 remains tetragonal and gradually turns into cubic. It suggests that the ionic charge defect is balanced by oxygen vacancies formation when Ti4+ are substituted by Co2+/Co3+.

Characterization of the optical properties of ArF laser irradiated Nd:YAG crystal

Nd:YAG crystal samples were irradiated by 100pulses of ArF laser at 50 and 250mJ/cm2 laser fluences and 1 and 50Hz repetition rates. The UV–vis–NIR spectra of the samples before and after the irradiation show that optical absorption changed in the entire spectral range. Additional absorption spectra were obtained for determining possible annihilated and generated defects in the crystal structure. A 236nm negative absorption band reveals that many oxygen vacancy centers of the crystal structure removed by 50mJ/cm2 ArF laser irradiation. On the other hand, a small positive absorption band at 239nm was observed related to F center generation in the crystal structure. The additional absorption spectral behavior of 250mJ/cm2 irradiated sample was different and a continuum positive absorption band in the 239–350nm spectral range was observed due to new defects generation in the crystal structure. It is proposed that it would be possible to optimize the crystal structure modification by controlling the laser irradiation parameters such as energy fluence, pulse number and repetition rate.

Synthesis and enhancement of multiferroic properties of (x)Ba0.95Sr0.05TiO3–(1−x)BiFe0.90Dy0.10O3 ceramics

Polycrystalline (x)Ba0.95Sr0.05TiO3–(1−x)BiFe0.90Dy0.10O3 [(x)BST–(1−x)BFDO] ceramics were synthesized by the standard solid-state reaction method. Samples prepared from these powders were sintered at various temperatures (900–1000°C). The crystal structure, microstructure, magnetic, dielectric, complex impedance and magnetoelectric properties of the (x)BST–(1−x)BFDO ceramics were systematically investigated. The X-ray diffraction pattern indicated that (x)BST–(1−x)BFDO ceramics showed a structural transition from rhombohedral to cubic phase. The average grain size increased to a maximum 2.86μm for x=0.20 and then decreased. M–H plot showed weak ferromagnetism for x=0.00 to 0.30. The magnetization value increased for increasing BST substitution up to x=0.20 due to the modification of crystal structure and then decreased for further increasing due to the nonmagnetic behavior of BST. A significant remnant magnetization (0.086emu/g) and a coercive magnetic field (103.62Oe) were also obtained for this solid solution. The complex initial permeability increased with the increase of both BST content (up to x=0.20) and sintering temperatures. The room-temperature dielectric constant increased whereas dielectric loss decreased with increasing BST content because of reducing oxygen vacancies. Impedance spectroscopy analysis confirmed the conducting grains and highly resistive grain boundaries affecting the conductivity but the grains had major contribution in the conduction mechanism. Magnetoelectric voltage coefficient (αME) increased with the increase of BST content because of strong interaction between magnetic and ferroelectric domains. The highest value of αME=1.67mVcm−1Oe−1 was observed for x=0.20 solid solution sintered at Ts=1000°C because of uniform grains in size and shape at this composition.

Preparation, characterization and molecular modeling studies of the inclusion complex of Caffeine with Beta-cyclodextrin

The formation through supramolecular interaction of a host–guest inclusion complex of caffeine (CA) with nano-hydrophobic cavity beta-cyclodextrin (β-CD) is achieved by a physical mixture, a kneading method and a co-precipitation method. The formation of the inclusion complex of CA with β-CD in solution state is confirmed by UV–visible spectrophotometer, fluorescence spectrophotometer and time-resolved fluorescence spectrophotometer. The stoichiometry of the inclusion complex is 1:1; the imidazole ring and pyrimidine ring of caffeine is deeply entrapped in the beta-cyclodextrin as confirmed by spectral shifts. The Benesi–Hildebrand plot is used to calculate the binding constant of the inclusion complex of CA with β-CD at room temperature. The Gibbs free energy change of the inclusion complex process is calculated and the process is found to be spontaneous. The thermal stability of the inclusion complex of CA with β-CD is analyzed using differential scanning calorimetry. The crystal structure modification of a solid inclusion complex is confirmed by scanning electron microscopy image analysis. The formation of the inclusion complex of CA with β-CD in the solid phase is also confirmed by FT-IR and XRD. The formation of the inclusion complex between CA and β-CD, as confirmed by molecular docking studies, is in good relationship with the results obtained through different experimental methods.

Virtually Designed Triclosan-Based Inhibitors of Enoyl-Acyl Carrier Protein Reductase of Mycobacterium tuberculosis and of Plasmodium falciparum.

We report here new chemical structures of predicted nanomolar triclosan-based inhibitors (TCLs) of Mycobacterium tuberculosis enoyl-acyl carrier protein reductase (InhA) virtually proposed by computer-assisted molecular design. 3D models of InhA-TCL complexes were prepared by in situ modifications of the reference crystal structure (PDB entry 1P45) for a training set of 15 TCLs with known InhA inhibitory activities. A QSAR model was built leading to linear correlation between the calculated free energies of complexation (ΔΔGcom ) and experimental values IC50 (exp) : pIC50 =-0.0657×ΔΔGcom +3.0502, R(2) =0.96. In addition, ligand-based quantitative pharmacophore model (PH4) was built from bound conformations of the training set compounds and confirmed the correlation between molecular models and observed activities: pIC50 (exp=) 0.8929×pIC50 (pre) -0.441, R(2) =0.95. Structural information from both models helped us to propose new TCL analogues. A virtual library of TCLs with known predicted activities against enoyl-acyl carrier protein reductase of Plasmodium falciparum (PfENR) was evaluated, revealing dual target TCLs. Moreover, analysis of binding site interactions suggested enriching substitutions, which led to more potent TCLs with predicted pIC50 (pre) as low as 7 nM. The computational approach, which used both free energy estimated from molecular modeling and 3D-QSAR pharmacophore model, was helpful in virtually proposing the dual-targeted drugs and provided valuable information for the design of novel potential antituberculotic agents.

Crystal chemical and structural modifications of erionite fibers leached with simulated lung fluids

Inhalation of erionite has been proven to be the cause of the extended epidemic of malignant mesothelioma occurring in Central Anatolia, Turkey, and of cases of lung diseases in the U.S.A. Its carcinogenicity is three orders of magnitude greater than that of regulated asbestos. Here we report the results of the investigation of the structural and crystal chemical modifications occurring in erionite leached with artificial lysosomal fluid (ALF) and Gamble’s solution. ALF leaching produces a migration of Na+ ions from Ca1 to Ca2 extraframework cationic site, without the occurrence of any significant modification of the chemical composition of the fibers. In contrast, leaching with Gamble’s solution induces a complex ionic-exchange process resulting in a temporary partial replacement of Na+ by Ca2+, coming from the fluid, which is fixed at a third Ca3 cationic site. Subsequently, the exchange process reverses. In fact, Ca2+ is removed from Ca3 and Na+ migrates back to Ca1, the structure being indistinguishable from the starting, unleached material. Such processes seem to be accompanied by a progressive amorphization of fibers. Present data could provide valuable background for a more detailed comprehension of the morphostructural/biological activity relationships inducing pathogenicity.

PZT to Lead Free Piezo Ceramics: A Review

The growth of piezo science is phenomenal since the discovery of piezoelectricity in 1880. Among various piezoelectric materials, lead zirconate titanate (PZT) is a very popular and exhaustively studied piezo system which allows synthesis of large number of materials with wide range of properties due to formation of solid solutions over large range of Zr:Ti ratio. Also, this system accommodates wide range of dopants for modification of crystal structure. Due to this versatile nature, PZT has emerged as very popular among users and researchers worldwide. However, considering the toxicity of lead oxide, development of lead free piezo ceramics is encouraged in recent years. Some lead free piezo material systems such as BNT, BKT, KNN, BZT-BCT have been explored. However, development of lead free piezo devices and their performance in comparison with PZT devices are yet to be established. At this juncture, it was felt that an article reviewing the current status of development of piezo materials highlighting the change from PZT to various lead free systems would be of very much interest to the researchers. Therefore, efforts are made to bring out the recent developments on R&D of piezo materials in this review article.

Tuning oxide activity through modification of the crystal and electronic structure: from strain to potential polymorphs.

Discovering new materials with tailored chemical properties is vital for advancing key technologies in catalysis and energy conversion. One strategy is the modification of a material's crystal structure, and new methods allow for the synthesis and stabilization of potential materials in a range of crystal polymorph structures. We assess the potential reactivity of four metastable oxide polymorphs of MO2 (M = Ru, Rh, Pt, Ir) transition metal oxides. In spite of the similar local geometry and coordination between atoms in the metastable polymorphic and stable rutile structure, we find that polymorph reactivities cannot be explained by strain alone and offer tunable reactivity and increased stability. Atom-projected density of states reveals that the unique reactivity of polymorphs are caused by a redistribution of energy levels of the t2g-states. This structure-activity relationship is induced by slight distortions to the M-O bonds in polymorphic structures and is unattainable by strain. We predict columbite IrO2 to be more active than rutile IrO2 for oxygen evolution.

BaCoO2.22: the most oxygen-deficient certified cubic perovskite.

The cubic BaCoO(∼2.2) was announced in the early 50's as the final product of high temperature self-reduction within the BaCoO(3-δ) series. However, apart from this report no clear characterization has been provided to date. Here, we confirm after the preparation of single crystal and powder samples that in this compound the ratio of oxygen vacancies is close to 27% in absence of any long range ordering. It follows that BaCoO(2.22) appears as the most oxygen deficient cubic perovskite stabilized at room temperature, its tolerance factor being displaced close to 1 by the combination of large Ba(2+) and Co(2/3+) ions in the A and B sites. The tolerance factor plays a limiting role for re-oxidation and fluorination using topochemical routes, despite the high concentration of available vacancies. Single crystal XRD data and DFT structural relaxation show that the Co sites are off-centered inside pseudo-tetrahedra leading to reinforced magnetic exchanges. Robust antiferromagnetic ordering is suggested to occur above 400 K while this compound shows a semi-conducting behavior. It was also possible to prepare an even more reduced mixed metallic phase of formula BaCo(0.5)Fe(0.5)O(2.16).

Ore Minerals Down to Nanoscale: Petrogenetic Implications

Like most minerals, sulphides and oxides are compositionally heterogeneous at the smallest scale. The application of a variety of different techniques is necessary to fully understand their crystal-chemistry, each with its own inherent advantages and dis-advantages, and each with limited ranges of obser-vational scale. Focussed Ion Beam Scanning Electron Microscopy (FIB-SEM) opens up new avenues for in-situ sampling of small volumes of material which have been compositionally characterised by other techniques, including SEM, EPMA and LA-ICPMS. Slices lifted from the surface of a polished section, typically 40 x 20 µm in size and a few µm thick, can be imaged and prepared for Transmission Electron Microscope (TEM) analysis. This procedure allows for bridging micro- to nanoscale observations on a site which is of petrogenetic interest (e.g., Ciobanu et al., 2011). One of the main themes of inquiry is the distribution of trace elements in ores relative to subtle changes in mineral speciation, nanoparticle nucleation or crystal-structural modifications. Here we show examples of the application of FIB-SEM and TEM studies to such topics from across ore geology. 2 Homology in Mixed-Layer Chalcogenides Bismuth minerals are common accessory minerals in gold deposits, and include Pb-Bi-sulphosalts and – tellurides. They form homologous or polysomatic series where small chemical variation from one species to another is linked to modifications of crystal-structural layers (modules or blocks) in a predictive manner. These minerals can thus record subtle variations in the chemistry of an evolving ore system via crystallisation processes at the smallest scale. One example is the tetradymite group, where the crystalchemical formula nBi2·mBi2X3 (X = Te, Se, S; e.g., Cook et al., 2007) indicates that all the phases can be derived from archetypal layers of fixed width, but of variable numbers (n, m) in the stacking sequence. Based on TEM studies that show monotonic decrease of crystal modulation vectors with increase in Bi, the homology in the group has been

Development and Evaluation of Non-Hydrous Skin Analogue Liquid Crystal using Thermo-Sensitivity Smart Sensor

【In this study, skin permeation enhancement was confirmed by designing it to have a structure and composition similarity to the intercellular lipids that improve miscibility with skin by cross-linked lipids poloxamer. The cross-linked lipids poloxamer was synthesized and analyzed by 1H NMR that structure dose had conjugated pluronic with ceramide3. Active component is released by modification of liquid crystal structure because PPO part, large-scale molecule block of pluronic, has hydrophobic nature at skin temperature of $35^{\circ}C$ . Conjugated pluronic with ceramide3 was synthesized using Pluronic F127 and p-NPC (4-nitrophenyl chloroformate) at room temperature yielded 89%. Pluronic(Ceramide 3-conjugated Pluronic) was synthesized by reaction of p-NP-Pluronic with Ceramide3 and DMAP. The yield was 51%. This cross-linked lipids poloxamer was blended and dissolved at isotropic state with skin surface lipids, phospholipid, ceramide, cholesterol and anhydrous additive solvent. Next step was preceded by ${\alpha}$ -Transition at low temperature for making the structure of Meso-Phase Lamella, and non-hydrous skin analogue liquid crystal using thermo-sensitivity smart sensor, lamellar liquid crystal structure through aging time. For confirmation of conjugation thermo-sensitivity smart sensor and non-hydrous skin analogue liquid crystal, structural observation and stability test were performed using XRD(Xray Diffraction), DSC(Differential Scanning Calorimetry), PM (Polarized Microscope) And C-SEM (Cryo-Scanning Electron Microscope). Thermo-sensitivity observation by Franz cell revealed that synthesized smart sensor shown skin permeation effect over 75% than normal liquid crystal. Furthermore, normal non-hydrous skin analogue liquid crystal that not applied smart sensor shown similar results below $35^{\circ}C$ of skin temperature, but its effects has increased more than 30% above $35^{\circ}C$ .】

In Situ-DRIFTS Study of Rh Promoted CuCo/Al2O3for Ethanol Synthesis via CO Hydrogenation

The promoting effect of rhodium on the structure and activity of the supported Cu-Co based catalysts for CO hydrogenation was investigated in detail. The samples were characterized by DRIFTS, <TEX>$N_2$</TEX>-adsorption, XRD, <TEX>$H_2$</TEX>-TPR, <TEX>$H_2$</TEX>-TPD and XPS. The results indicated that the introduction of rhodium to Cu-Co catalysts resulted in modification of metal dispersion, reducibility and crystal structure. DRIFTS results of CO hydrogenation at reaction condition (P=2 MPa, <TEX>$T=260^{\circ}C$</TEX>) indicated the addition of 1 wt % rhodium improved hydrogenation ability of Cu-Co catalysts. The ethanol selectivity and CO conversion were both improved by 1 wt % Rh promoted Cu-Co based catalysts. The alcohol distribution over un-promoted and rhodium promoted Cu-Co based catalysts obeys A-S-F rule and higher chain growth probability was got on rhodium promoted catalyst.

Crystal structure of human cytosolic aspartyl-tRNA synthetase

Human cytosolic aspartyl-tRNA synthetase (DRS) catalyzes the attachment of the amino acid aspartic acid to its cognate tRNA and it is a component of the multi-tRNA synthetase complex (MSC) which has been known to be involved in unexpected signaling pathways. Here, we report the crystal structure of DRS at 2.25 Å resolution. DRS is a homodimer with a dimer interface 3,750.5 Å2which comprises of 16.6% of the monomeric surface area. Our structure reveals the C-terminal end of the N-helix which is considered as a unique addition in DRS, and its conformation further supports the switching model of the N-helix for the transfer of tRNAAsp to elongation factor 1α. From our analyses of the crystal structure and post-translational modification of DRS, we suggest that the phosphorylation of Ser146 provokes the separation of DRS from the MSC and provides the binding site for an interaction partner with unforeseen functions.

Semiconductor photocatalysts for water oxidation: current status and challenges

Artificial photosynthesis is a highly-promising strategy to convert solar energy into hydrogen energy for the relief of the global energy crisis. Water oxidation is the bottleneck for its kinetic and energetic complexity in the further enhancement of the overall efficiency of the artificial photosystem. Developing efficient and cost-effective photocatalysts for water oxidation is a growing desire, and semiconductor photocatalysts have recently attracted more attention due to their stability and simplicity. This article reviews the recent advancement of semiconductor photocatalysts with a focus on the relationship between material optimization and water oxidation efficiency. A brief introduction to artificial photosynthesis and water oxidation is given first, followed by an explanation of the basic rules and mechanisms of semiconductor particulate photocatalysts for water oxidation as theoretical references for discussions of componential, surface structure, and crystal structure modification. O2-evolving photocatalysts in Z-scheme systems are also introduced to demonstrate practical applications of water oxidation photocatalysts in artificial photosystems. The final part proposes some challenges based on the dynamics and energetics of photoholes which are fundamental to the enhancement of water oxidation efficiency, as well as on the simulation of natural water oxidation that will be a trend in future research.

Magnonic band structures in two-dimensional bi-component magnonic crystals with in-plane magnetization

We investigate the magnonic band structure of in-plane magnetized two-dimensional magnonic crystals composed of cobalt dots embedded into a permalloy antidot lattice. Our analysis is based on the results of numerical calculations carried out by the plane wave method. The complex magnonic band structure found in square-lattice magnonic crystals is explained on the basis of the spin wave dispersion relations calculated in the empty lattice model. We show that four principal effects influence the formation of a magnonic band structure in planar two-dimensional bi-component magnonic crystals: a folding effect, Bragg scattering, hybridization between various spin wave modes, and a demagnetizing field. While the first two effects are found for other types of waves in periodic composites, the third one exists in an anisotropic medium and the last one is specific to spin waves propagating in magnonic crystals with magnetization in the film plane. The strong anisotropy in the dispersion relation of spin waves in thin ferromagnetic films results in the crossing and anti-crossing of the fast, Damon–Eshbach-like mode with a number of other spin waves folded to the first Brillouin zone. The demagnetizing field can induce the formation of channels for spin waves which are propagating perpendicular to the external magnetic field direction, but this property exists only in the limiting range of the thicknesses and the lattice constants of the bi-component magnonic crystals. Based on the model analysis we propose a modification of the magnonic crystal structure by changing its thickness, lattice constant and aspect ratio along the direction of the applied magnetic field to significantly modify the magnonic band structure and obtain partial magnonic band gaps.

Effect of strontium ranelate on bone mineral: Analysis of nanoscale compositional changes

Strontium ranelate has been used to prevent bone loss and stimulate bone regeneration. Although strontium may integrate into the bone crystal lattice, the chemical and structural modifications of the bone when strontium interacts with the mineral phase are not completely understood. The objective of this study was to evaluate apatite from the mandibles of rats treated with strontium ranelate in the drinking water and compare its characteristics with those from untreated rats and synthetic apatites with and without strontium. Electron energy loss near edge structures from phosphorus, carbon, calcium and strontium were obtained by electron energy loss spectroscopy in a transmission electron microscope. The strontium signal was detected in the biological and synthetic samples containing strontium. The relative quantification of carbon by analyzing the CK edge at an energy loss of ΔE=284eV showed an increase in the number of carbonate groups in the bone mineral of treated rats. A synthetic strontium-containing sample used as control did not exhibit a carbon signal. This study showed physicochemical modifications in the bone mineral at the nanoscale caused by the systemic administration of strontium ranelate.

Color tunable Sr2SiO4:Eu2+ phosphors through the modification of crystal structure

Eu2+ doped Sr2SiO4 phosphors were prepared through a solid-state reaction method. The phase-composition and photoluminescence of the obtained phosphors were systematically studied in terms of calcination temperature, Eu and Ba doping. High calcination temperature promoted the phase transformation from α′–Sr2SiO4 (orthorhombic) to β–Sr2SiO4 (monoclinic), while the doping of Eu or Ba ions could stabilize α′–Sr2SiO4 phase due to their long bond length with oxygen. Small amount of Eu/Ba doping prefers to occupy Sr(I) sites in the crystal lattice of Sr2SiO4, acting as nucleation sites for both α′– and β–Sr2SiO4 phases. After nucleation, Eu2+ ions distribute equally in the two sites. Through structural modification, the Sr2SiO4:Eu2+ phosphors could be controlled to emit different colors in a wide range, from blue to yellow, making them good candidates for tuning the chromaticity in application.

Crystal structure of human cytosolic aspartyl‐tRNA synthetase, a component of multi‐tRNA synthetase complex

Human cytosolic aspartyl-tRNA synthetase (DRS) catalyzes the attachment of the amino acid aspartic acid to its cognate tRNA and it is a component of the multi-tRNA synthetase complex (MSC) which has been known to be involved in unexpected signaling pathways. Here, we report the crystal structure of DRS at a resolution of 2.25 Å. DRS is a homodimer with a dimer interface of 3750.5 Å2 which comprises 16.6% of the monomeric surface area. Our structure reveals the C-terminal end of the N-helix which is considered as a unique addition in DRS, and its conformation further supports the switching model of the N-helix for the transfer of tRNAAsp to elongation factor 1α. From our analyses of the crystal structure and post-translational modification of DRS, we suggest that the phosphorylation of Ser146 provokes the separation of DRS from the MSC and provides the binding site for an interaction partner with unforeseen functions.

Interplay between lattice, orbital, and magnetic degrees of freedom in the chain-polymer Cu(II) breathing crystals

The chain-polymer Cu(II) ``breathing crystals'' C${}_{21}$H${}_{19}$CuF${}_{12}$N${}_{4}$O${}_{6}$ were studied using the x-ray diffraction and ab initio band structure calculations. We show that the crystal structure modification at $T=146$ K, associated with the spin crossover transition, induces the changes of the orbital order in half of the Cu sites. This in turn results in the switch of the magnetic interaction sign in accordance with the Goodenough-Kanamori-Andersen theory of the coupling between the orbital and spin degrees of freedom.

Influence of Trace Amount of Well-Dispersed Carbon Nanotubes on Structural Development and Tensile Properties of Polypropylene

Functionalized multiwalled carbon nanotubes (F-MWCNTs) were individually dispersed in a commercial polypropylene (PP) matrix using our well-established α-zirconium phosphate (ZrP) nanoplatelet-assisted dispersion approach. The F-MWCNTs remained uniformly dispersed in PP after melt mixing and injection-molding and were found to remarkably enhance modulus and strength at only 0.1 wt % loading. The individual F-MWCNTs were mostly oriented and extended in the flow direction and were shown to be integrated within the crystalline structure of the matrix. The change in mechanical properties is attributed to both the modification in crystal structure due to MWCNT-induced nucleation and the direct reinforcement of crystalline lamellae and amorphous regions by the MWCNTs. We propose that the compatibilized F-MWCNTs exhibit sufficient interfacial interaction with the PP matrix to anchor lamellae stacks and resist interlamellar slip. The F-MWCNTs also reinforce amorphous domains between crystallites and behave as “su...