An Investigation of PLD-Deposited Barium Strontium Titanate (Ba_xSr_1-xTiO₃) Thin Film Optical Properties

Reflectance and transmittance parameters of pulsed laser deposited barium strontium titanate (BST) were investigated using spectrophotometric methods. Three stoichiometries consisting of BaxSr1-xTiO3 (x = 0.30, 0.40, 0.50) were deposited on glass substrates using oxygen partial pressures of 1.3 Pa ± 0.13 Pa at 500oC. Subsequently, the measured optical parameters were employed to determine the refractive index (n), extinction coefficient (k), optical conductivity (σ), absorption coefficient (α) and optical bandgap (Eg) using swept spectra in the ultraviolet, visible and near-infrared range (200 nm - 1100 nm) as these have not been reported in the literature. The calculated parameters for Ba0.4Sr0.6TiO3 are reported in this experimental work. Minimal differences in the transmittance have been observed at the visible band edges when comparing each stoichiometry. Sharp cutoffs were observed at the bands edges and strong absorbance in the 200 nm - 300 nm band as attributed to the crystal structure based upon the oxygen partial pressure during the deposition process.

Ce-SAD Phasing of Glucose Isomerase and Thermolysin Using Cu <i>Kα</i>Radiation

Current structural genomics projects aim to solve a large number of selected protein structures as fast as possible. High degree of automation and standardization is required at every step of the whole process to speed up protein structure determination. Phase problem is a bottleneck in macromolecular structure determination and also in model building which is a time-consuming task. The simplest approach to phasing macromolecular crystal structures is the use of a SAD signal. SAD data can be collected using the in-house copper (1.54 A) wavelength source. Data collected using copper wavelength with the incorporation of anomalously scattering heavy metal atoms may serve as a powerful tool for structural biologists to solve novel protein structures as well where synchrotron beam line is not available. A short soak of protein crystals in heavy metal solution or by incorporating heavy atoms into the protein drop while crystallizing the protein (co-crystallization) leads to incorporation of these heavy metal ions into the ordered solvent shell around the protein surface. The present work aims to determine whether cerium ion can be successfully incorporated into the protein crystal through quick-soaking method while maintaining the isomorphism. The study also aims in understanding whether this metal ion can be used for phasing purpose. The intensity data are collected and analyzed for anomalous signal, substructure solution and the binding sites.

Pseudosymmetric Features and Nonlinear Optical Properties of Potassium Titanyl Phosphate Crystals

A number of publications containing structural data, characteristics of nonlinear optical properties of pure and doped crystals of potassium titanyl phosphate (KTP) family have been reviewed to analyze the structural and symmetry conditionality of nonlinear optical properties of these crystals. The pseudosymmetric features of KTP-type crystals with respect to inversion are investigated. Specifically, pseudoinversion distribution maps are calculated;pseudoinversion extrema and coordinates of pseudoinversion centres are found;and the distributions of pure and doped KTP-type structures and their individual atomic sublattices over the degree of pseudoinversion are analyzed. A correlation between the characteristics of nonlinear optical properties of a number of crystals belonging to the KTP family and the degree of pseudoinversion of their atomic structures is demonstrated.

Synthesis, Structural Characterization and Computational Studies of Bis(2-Ethylimidazole) Bis(Formato)Zinc(II)-Water (1/1)

The reaction of 2-ethylimidazole and zinc formate monohydrate in 1:2 ratio in toluene leads to the formation of bis(2-ethylimidazole)bis(formato)zinc(II)-water (1/1), [Zn(N2H8C5)2(OCHO)2]·H2O, 1 which has been characterized by several techniques, including elemental and thermal analyses, IR, 1HNMR and 13CNMR spectroscopies, single crystal X-ray diffraction and DFT studies. The results obtained show that this complex crystallizes in the orthorhombic crystal system of the Pbca space group, with cell parameters a = 14.7230(2) &Aring;, b = 7.3880(10) &Aring;, c = 29.0843(4) &Aring;, α = 90°, β = 90°, γ = 90°, V = 3163.73 &Aring;3 and Z = 8. The zinc center is bound to two molecules of 2-ethylimidazole, two formate molecules in a tetrahedral coordination geometry. One water of crystallization is present in the coordination sphere of the compound. Its molecular crystalline structure is strengthened by O/N-H…O, O-H…π, O-H…H, C-H…O, H…π, π…O and π…π interactions. The optimized structure, frontier molecular orbitals, global reactivity descriptors, molecular electrostatic potential, natural bond orbitals and the Mulliken atomic charges were investigated through theoretical studies.

Synthesis and Structure of Dimeric Copper (I) Complex from Bis[(2,2’)-dimethyl 2,2’-(1,10-phenanthroline-2,9-diyl) bis(methan-1-yl-1-ylidene)-bis(hydrazinecarbo dithioate)]

Metal complex, bis[(2,2’)-dimethyl 2,2’-(1,10-phenanthrline-2,9-diyl)bis(methan-1-yl-1-ylidene)-bis(hydrazinecarrbo dithioate)copper(I)], was synthesized from the reaction of Schiff base, (2,2’)-dimethyl 2,2’-(1,10-phenanthroline-2,9-diyl)bis(methan-1-yl-1-ylidene)-bis(hydrazinecarbo dithioate) and CuCl2 at reflux condition in methanol. The copper centers of the complex appear to be reduced. This probably was facilitated by in situ oxidative formation of disulfide bond at the uncomplexed ligand moieties. Single crystal X-ray diffraction analysis reveals the distorted tetrahedral geometry around the copper centers. This compound crystallizes in the triclinic space group, P-1 with crystallographic parameters: a = 10.006(3) ?, b = 13.272(3) ?, c = 22.123(6) ?, α = 85.656(6)°, β = 81.656(6)°, γ = 73.097(5)°, μ = 1.223 mm-1 , V = 2779.5(13) ?3, Z = 2, Dc = 1.437 Mg/m3, T = 293 (2) K.

Crystal and Molecular Structure of 4-Benzoyl-1,5-diphenyl-1H-pyrazole-3-carbonitrile

The crystal structure of potential active 4-benzoyl-1,5-diphenyl-1H*-pyrazole-3-carbonitrile (C23H15N3O) (I) has been determined from single crystal X-ray diffraction data. Also IR, Uv-vis and NMR spectral data were determined. The title compound crystallizes in the monoclinic space group P* 21/c, with a* = 9.3167(2), b* = 20.6677(3), c* = 10.6143(3) ?, β* = 112.665(3)°, V* = 1886.00(8) ?3, Dcalc* = 1.23g cm-3, Z* = 4. In the structure, intermolecular H*-bonds lead to the formation of a centrosymmetric dimmer of the molecule. Furthermore, the compound has a wide transmission window (300 to 1100 nm) with a transparency of nearly 100% and the UV cut-off wavelength occurs at 242 nm.

Vibrational, Electronic and Structural Study of Sprayed ZnO Thin Film Based on the IR-Raman Spectra and DFT Calculations

Applying the Density Function Theory (DFT) combined with LCAO basis set and employing the B3LYP hybrid functional, the optimized geometrical parameters, electronic properties, as well as the Infrared and Raman spectra for wurtzite-ZnO structure were investigated. Prior to computing, ZnO thin film prepared by the spray pyrolysis method is characterized by X-ray diffraction using Rietveld refinement. This analysis shows that ZnO has hexagonal wurtzite structure (P63mc) with lattice parameters, a = 3.2467 and c = 5.2151 Åin good agreement with our predicted optimized geometry. Atomic force microscopy (AFM), Raman spectroscopy and UV-Vis-NIR spectrophotometry techniques are used to explore morphological, optical and vibrational properties of the sprayed ZnO thin film. The computed band gap is in excellent agreement with that deduced from UV-Vis transmission . The simulated infrared and Raman spectra were also calculated, and a good agreement with the measured spectra is obtained. Finally, a detailed interpretation of the infrared and Raman spectra is reported.

Investigating Double-Regime Crossover in Y₁Ba₂Cu_{3 - x}R_xO_{7 - δ}Superconductors

The effect of Pr and Gd doping on the transport properties of Cu-deficient YBCO superconductors has been studied. Two series of Y1Ba2Cu3 - xRxO7 - δ, where R = Pr or Gd, were prepared by the conventional solid-state reaction technique. Resistance measurements showed a suppression of Tc with increasing of Pr- and Gd-contents in addition to a normal-state metal-to-insulator transition. Moreover, a superconductor-to-insulator transition has been observed at ambient pressure for temperatures less than 50 K for Pr with x = 0.3 and for Gd with x > 0.3. The overall complex behaviours of the resistivity data have been preliminary explained in terms of localization of charge carriers, structural disorders, and magnetic ordering of magnetic moments.

Lead Iodide Crystals as Input Material for Radiation Detectors

Lead iodide is an important inorganic solid for fundamental research and possible technological applications and is considered to be a potential room temperature nuclear radiation detector. In lead iodide the phenomenon of polytypism is posing an interesting problem of phase transformations amongst its various polytypic modifications. The transformations have also been observed even when the crystals are stored for few months. It causes deterioration in functioning of PbI2 devices. Taking into account the known structures of PbI2 and the data available on the mode of growth and storage of crystals, it has been concluded that purified melt grown crystals of PbI2 are the best suited for nuclear radiation detectors.

Synthesis and Crystal Structure of the First Example of a Tris-Chelated Co(II) Complex Based on Oxamide Dioxime Ligand

A new cobalt(II) complex, [Co(H2 oxado)3 ]C2 O4 H2 oxado·2H2 O (H2 oxado = oxamide dioxime), has been synthesized in aqueous solution and characterized by elemental analysis and single crystal X-ray structure determination. The complex crystallizes in the triclinic space group P-1, with the parameters a = 9.46(4), b = 11.84(5), c = 12. 81(5)?&Aring, α = 104.94(6), β = 99.29(5), γ = 106.73(5), V = 1284(9) &Aring3, Z = 2. The central cobalt(II) cation is pseudo-octahedrally coordinated by six imino N atoms of the neutral oxamide dioxime ligand. In the solid state, each of the following bricks, namely the cationic complexes, the oxalate dianions as well as the oxamide dioxime crystallization molecules, pile up parallel to the a axis. The bulk structure is consolidated by an extended three-dimensional network of hydrogen bridgings—that link the ionic partners, oxamide dioxime and water molecules to one another—and by coulombic interactions.

Syntheses, Crystal Structure and Photoluminescence Properties of Piperidinium Tetrakis (1,3-Diphenyl-1,3-Propanedionato) Europate(III) Complex and Its Two Different Crystals

Treatment of 1,3-diphenyl-1,3-propanedione 1a with europium (III) chloride in the presence of piperidine results in the halide ligands exchange giving newly piperidinium tetrakis (1,3-diphenyl-1,3-propanedionato)europate(III) complex 2a. The complex was characterized by 1H-NMR, positive FAB-mass, and Elemental Analysis. The exact molecular structure of 2a was determined by single crystal X-ray diffraction with the monoclinic space group Cc (centrosymmetric, No.13). The large cavity sizes of the complex 2a facilitated the inclusion of water and benzene solvate molecules. The other two different crystals 2b, 2c having two water molecules and one benzene moleculewere obtained by the crystallization in different solvents and the exact molecular structures were determined by single crystal X-ray diffraction analysis with space groups P21/n (centrosymmetric, No.14), and P21/n (centrosymmetric, No.14), respectively. The eight coordinate structures of the complexes in the three crystals were slightly different due to the crystal packing and the existence of the solvent molecule(s). The photoluminescence studies indicated that four β-diketone ligands acted as strong antenna ligands and transferred the absorbed energy to europium (III) ion, consequently red luminescence was observed. These strong emissions wereattributed to the 5D0 → 7F2 transition of Europium (III) ions under UV excitation. The photoluminescence spectrum of the three crystals was almost same in solid as well as in solution.

Three New -CF3, -CN Containing <i>π</i>-Conjugated Heteroaromatic Compounds: Synthesis, Crystal Structure and Photoelectronic Properties

Three new π-conjugated hetero aromatic materials consisting of pyridine 3a, furan 3b, and thiophene 3c have been synthesized by Knoevenagel condensation reaction. These molecules have been characterized by 1H NMR, EI-MS and single crystal X-ray diffraction analysis. Molecule 3a crystallized under monoclinic system with space group C2/c, molecule 3b crystallized under triclinic system with space group P-1 and the molecule 3c crystalized under triclinic system with space group P-1. The optoelectronic properties of these compounds have been studied.Molecules 3a, 3b and 3c showed strong absorption maxima wavelengths at 300, 419 and 418 nm, respectively. The molar extinction coefficients (ε) of the compounds 3a, 3b and 3c suggested that molecule 3b has better ability to absorb UV light;molecule 3a has better fluorescence intensity than molecule 3b and 3c. Low energy gaps of HOMO and LUMO energy levels of these compounds suggests that these compounds may be a promising new class of lead compounds for developing high performance semiconductor materials. Compounds 3a, 3b and 3c has emissions near to blue light, a slight modification of the structures by extending conjugation may find important applications in optoelectronic devices as blue light emitters in organic light-emitting devices for the development of new generation organic semiconducting materials.

Estimation of Nucleation Thermodynamical Parameters of La2Sr2xCuO4 (LSCO) and YBa2Cu2O7–δ (YBCO) Crystallizing from High Temperature Solution

The growth kinetics of LSCO and YBCO single crystals from high temperature solution of LSCO-CuO solute-solvent and YBCO-CuO solute-solvent systems has been investigated. Based on regular solution model and classical nucleation theory, the thermodynamical data investigated for the systems are used to determine the nucleation parameters: interfacial free energy, metastable zone-width, volume free energy, critical energy barrier for nucleation and radius of critical nucleus for LSCO and YBCO which leads to the understanding of the nucleation phenomena of LSCO and YBCO.

Interaction of Iron(III)-5,10,15,20-Tetrakis (4-Sulfonatophenyl) Porphyrin with Chloroquine, Quinine and Quinidine

Iron(III)-5,10,15,20-tetrakis(4-sulfonatophenyl) porphyrin (FeTPPS) is used as non-physiological metalloporphyrin model for the natural iron (III)-protoporphyrin IX (FePPIX) resulting from hemoglobin degradation to investigate ligand binding reactions in aqueous solution. Studies were conducted on the interaction of FeTPPS with Chloroquine, Quinine, and Quinidine, which are historically the most common quinoline-based drugs used to treat malaria, an infectious disease afflicting several hundred millions every year worldwide, mainly in tropical regions. Using UV-Visible spectrophotometry, the binding reaction was studied at pH 7.40 in purely aqueous solution, and in aqueous solution containing NaNO3 at concentration of 0.1 M. Fitted titration curves obtained were in agreement with experimental data according to a formation scheme of 1:1 complex (1 FeTPPS μ-oxo-dimer: 1 Antimalarial). Values of apparent binding constant (K) obtained were between 4.3 × 103 M-1 to 7.59 × 104 M-1, demonstrating that FeTPPS and the antimalarials formed stable complexes. The stability of the complex decreased when NaNO3 was added to the solution. This ionic strength dependence was ascribed to electrostatic effects. Quinine and Chloroquine interacted with FeTPPS stronger than Quinidine did. Chloroquine showed the strongest affinity to FeTPPS. These findings revealed the influence of steric and stereochemical factors. Molecular electrostatic potentials (MEP) calculated with Hartree-Fock theory argue in favor of π-π and electrostatic interactions between reaction partners as driving forces for the complex formation. In the case of FeTPPS: Chloroquine interaction, it is suggested that an intramolecular hydrogen bond is formed between phenyl??and quinuclidine N-H+ as additional force stabilizing the complex. Analysis of crystallographic data using the Cambridge Structural Database (CSD) gave evidence of the hydrogen bond formation between phenyl??and N-H+ groups in 370 structures.

Method to Study the Primary Nucleation for Solid Solution: Application to Uranium-Neodymium Oxalate Coprecipitation

Actinides co-precipitation is currently investigated in order to synthesize solid solutions of actinides mixed oxalates. This paper deals with the thermodynamic and kinetic study of the precipitation of uranium-neodymium oxalate system. Based on an analysis of the theories developed in the literature, a new expression for the determination of the supersaturation ratio for the solid solutions is presented. An experimental study of the nucleation kinetics was performed on the mixed uranium-neodymium oxalates. Homogeneous and heterogeneous primary nucleation laws are obtained using a specific stopped flow apparatus. The experimental results are consistent with the classical behaviour of nucleation phenomena. The values of the kinetic parameters for the solid solution point out that the formation of the uraniumneodymium mixed oxalates is kinetically favoured compared with the simple uranium and neodymium oxalates.

Purification, Crystallization and Preliminary X-Ray Diffraction Analysis of Exodeoxyribonuclease III from Crenarchaeon <i>Sulfolobus tokodaii</i>Strain 7

Exodeoxyribonuclease III (EXOIII) acts as a 3’→5’ exonuclease and is homologous to purinic/apyrimidinic (AP) endonuclease (APE), which plays an important role in the base excision repair pathway. To structurally investigate the reaction and substrate recognition mechanisms of EXOIII, a crystallographic study of EXOIII from Sulfolobus tokodaii strain 7 was carried out. The purified enzyme was crystallized by using the hanging-drop vapor-diffusion method. The crystals belonged to space group C2, with unit-cell parameters a = 154.2, b = 47.7, c = 92.4 ?, β = 125.8° and diffracted to 1.5 ? resolution.

Characterization of Thin Films by Low Incidence X-Ray Diffraction

Glancing Angle X-ray Diffraction (GAXRD) is introduced as a direct, non-destructive, surface-sensitive technique for analysis of thin films. The method was applied to polycrystalline thin films (namely, titanium oxide, zinc selenide, cadmium selenide and combinations thereof) obtained by electrochemical growth, in order to determine the composition of ultra-thin surface layers, to estimate film thickness, and perform depth profiling of multilayered heterostructures. The experimental data are treated on the basis of a simple absorption-diffraction model involving the glancing angle of X-ray incidence.

Docking of Glycokinase with Oxo, Sulfo, and Seleno Derivatives of the Carboxamide Activator S41

Inactivation of Glucokinase (GK) is associated with diabetes. Therefore, design of drugs targeting the GK activator site is currently integrated in the?strategy of the diabetes treatment.?The present work investigated the affinity of 30 ligands to GK based on molecular docking using the Gold 5.6 program. Glucokinase’s structure was derived from the Protein Data Bank (PDB Code?3S41), while the ligands were seleno, sulfo and oxo derivatives of the co-crystallized?carboxamide activator (PDB code:?S41). The results of the ligand-protein docking?revealed that GK formed thermodynamically stable complexes with all ligands. The main forces stabilizing the complexes are lipophilic interactions, enhanced by hydrogen bonds. Ligand molecular areas responsible for lipophilic and hydrogen bonding contacts with amino acid residues in the allosteric site of GK were evidenced by molecular electrostatic potentials (MEPs). Interestingly,?twelve of the S41 derivatives interacted with GK more strongly than the co-crystallized activator, while maintaining the lipophilic contacts with key amino acid residues like Arg63, which are catalytically crucial for?therapeutic properties of GK activators (GKAs).?It is noteworthy that divalent Se and S atoms were also involved in chalcogen bonds in the GKA site. Those bonds were nearly linear like hydrogen bonds. Such bond directionality should guide the design of pharmacophoric ligands containing chalcogen atoms.

Synthesis, Structural Characterization and DFT Studies of Silver(I) Complex Salt of Bis(4,5-dihydro-1<i>H</i>-benzo[g]indazole)

A new silver complex salt [Ag(N2C11H10)2]NO3 (where N2C11H10 = 4,5-dihydro-1H-benzo[g]indazole), has been synthesized and characterized by elemental and thermal analyses, IR and 1HNMR spectroscopies, single crystal X-ray structure determination and DFT studies. Its molecular structure comprises of a silver center coordinated to two nitrogen atoms from two 4,5-dihydro-1H-benzo[g]indazole molecule giving rise to a cationic complex entity, [Ag(N2C11H10)2]+ with as counter ion. The bulk structure is consolidated by N–H…O, C–H…π, Ag…π and Ag…O intermolecular interactions, thus generating a pseudo-helical network. The optimized structure, frontier molecular orbitals (HOMO and LUMO) and global reactivity descriptors were investigated by performing DFT calculations.

Metal-Organic Deposition of Epitaxial La_0.7Sr_0.3CoO₃Thin Films on LaAlO₃Substrates

La0.7Sr0.3CoO3 (LSCO) thin films were epitaxially grown on (001)-single crystalline LaAlO3 substrates by metal organic deposition. The evolution of the crystallinity of the films having various thicknesses and obtained at various annealing temperatures is investigated using Raman spectroscopy. The Raman mode associated to the Jahn-Teller distortions in the LSCO films is found to be dependent on the annealing temperature and sensitive to the strain state evolution with film thickness. The microstructure and morphology of the obtained films were investigated using transmission electron microscopy observations on cross-sections and atomic force microscopy. The obtained films are characterized by nanocrystalline morphology, with an average roughness around 5 nm. By increasing the annealing temperature to 1000℃ and the film thickness to 100 nm, the electrical resistivity was decreased by several orders of magnitude. The film resistivity reaches approximately 2.7 × 10–4 Ω&bull;cm in a wide interval of temperature of 77 - 320 K, making this material a promising candidate for a variety of applications.