A quantum‐chemical study of phosphor impurity in BaTiO3 crystal

Structural and electronic effects produced by a P impurity in the cubic and tetragonal BaTiO₃ lattices are investigated using a simple quantum chemical computer code based on the Hartree–Fock methodology. The obtained atomic displacements due to the defect present in otherwise pure crystal are mainly toward the impurity atom, thus reducing the interatomic distances within the defective region. It is also found that the phosphor produces some redistribution of electron density from the defect‐neighboring atoms toward the chemical bonds thus diminishing the charges on atoms. We also observe a local energy level in the band‐gap of material being composed mainly of P 3s atomic orbital. The level finds itself close to the top of the upper valence band, in no case contributing into the n‐type conductivity in BaTiO₃. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

Chemical synthesis of poly‐γ‐glutamic acid by polycondensation of γ‐glutamic acid dimer: Synthesis and reaction of poly‐γ‐glutamic acid methyl ester

α‐Methyl glutamic acid (L ‐L )‐, (L ‐D )‐, (D ‐L )‐, and (D ‐D )‐γ‐dimers were synthesized from L ‐ and D ‐glutamic acids, and the obtained dimers were subjected to polycondensation with 1‐(3‐dimethylaminopropyl)‐3‐ethylcarbodiimide hydrochloride and 1‐hydroxybenzotriazole hydrate as condensation reagents. Poly‐γ‐glutamic acid (γ‐PGA) methyl ester with the number‐average molecular weights of 5000∼20,000 were obtained by polycondensation in N,N‐dimethylformamide in 44∼91% yields. The polycondensation of (L ‐L )‐ and (D ‐D )‐dimers afforded the polymers with much larger |[α]_D | compared with the corresponding dimers. The polymer could be transformed into γ‐PGA by alkaline hydrolysis or transesterification into α‐benzyl ester followed by hydrogenation. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 732–741, 2001     

Tetrakis­(tetra­hydro­furan‐κO)­lithium mer‐tris­(carbazolyl‐κN)‐trans‐di­chloro(tetra­hydro­furan‐κO)­zirconate

In the title compound, [Li(C₄H₈O)₄][ZrCl₂(C₁₂H₈N)₃(C₄H₈O)], the environment of the Zr atom is pseudo‐octahedral, with the three carbazolyl ligands in a mer configuration. The counter‐ion of the zirconium complex is composed of an Li atom surrounded by four tetra­hydro­furan (THF) mol­ecules. The THF mol­ecule attached to the Zr atom is disordered over two sites, as are two of the THF mol­ecules in the lithium moiety. All bond distances and angles are consistent with those in complexes with similar structural entities. The Zr—N bond distances are 2.2185 (18) and 2.167 (3) Å.     

Tri­benzyl{η5‐[2‐(p‐tolyl)­prop‐2‐yl]­cyclo­penta­dienyl}­zirconium

The title compound, [Zr(C₇H₇)₃(C₁₅H₁₇)], (I), crystallizes from light petroleum with two independent mol­ecules in the asymmetric unit. Whereas in the parent mol­ecule, Zr(η⁵‐C₅H₅)(CH₂Ph)₃, all three Zr—CH₂Ph angles are equal, in (I), they differ significantly. In spite of their different environments, both independent mol­ecules in (I) exhibit a small, an expected, and a large Zr—CH₂Ph angle. The angles are similar to those of the closely related tri­benzyl­[η⁵‐(benzyl­di­methyl­silyl)­cyclo­penta­dienyl]­zirconium complex. The smallest Zr—CH₂Ph angle and the consequently relatively short Zr?C_ipso distance are indicative of η²‐bonding of the benzyl group.     

Structural and electronic properties of La‐doped CaTiO3 crystal

There is experimental and computational evidence that some important properties such as electrical conductivity and ferroelectricity in the CaTiO₃ crystal change according to the dopant states. Using an INDO quantum‐chemical computational method modified for crystal calculations we explore the stability of the La‐doped CaTiO₃ crystal in both phases, cubic and orthorhombic. The calculations are carried out by means of the supercell model based on the LUC (large unit cell) approach as it is implemented into the CLUSTERD computer code. The equilibrium geometry for impurity is found together with the crystalline lattice distortions. Atomic displacements and relaxation energies are analyzed in a comparative manner for the two crystallographic phases. A new effect of electron transfer from the local one‐electron energy level within the band‐gap to the conduction band is observed. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002     

α‐olefin homopolymerization and ethylene/1‐hexene copolymerization catalysed by novel ansa‐group IV complexes/MAO system

The catalytic properties of a set of ansa‐complexes (R‐Ph)₂C(Cp)(Ind)MCl₂ [R = ^tBu, M = Ti ( 3 ), Zr ( 4 ) or Hf ( 5 ); R = MeO, M = Zr ( 6 ), Hf ( 7 )] in α‐olefin homopolymerization and ethylene/1‐hexene copolymerization were explored in the presence of MAO (methylaluminoxane). Complex 4 with steric bulk ^tBu group on phenyl exhibited remarkable catalytic activity for ethylene polymerization. It was 1.6‐fold more active than complex 11 [Ph₂C(Cp)(Ind)ZrCl₂] at 11 atm ethylene pressure and was 4.8‐fold more active at 1 atm pressure. The introduction of bulk substituent ^tBu into phenyl groups not only increased the catalytic activity greatly but also enhanced the content of 1‐hexene in ethylene/1‐hexene copolymerization. The highest 1‐hexene incorporation was 25.4%. In addition, 4 was also active for propylene and 1‐hexene homopolymerization, respectively, and low isotactic polypropylene (mmmm = 11.3%) and isotactic polyhexene (mmmm = 31.6%) were obtained. Copyright © 2007 John Wiley & Sons, Ltd.     

High‐Throughput Production of Zr‐Doped Li4Ti5O12 Modified by Mesoporous Libaf3 Nanoparticles for Superior Lithium and Potassium Storage

Li₄Ti₅O₁₂ is a promising anode for lithium‐ion batteries due to its zero‐strain properties. However, its low conductivity has greatly affected its rate performance. At the same time, the electrolyte decomposition during cycling also needs to be solved, especially at low cut‐off voltage. Herein, using a high‐throughput two‐step method, we synthesized Zr‐doped LTO modified by mesoporous LiBaF₃ nanoparticles for alkali‐ion storage. The doping of Zr can enhance the electronic conductivity and facilitate the rate performance. Meanwhile, the coating of mesoporous LiBaF₃ nanoparticles can form a mesoporous surface with large pore size (ca. 3–10 nm), which can benefit the alkali ion diffusion and simultaneously restrain the formation of an excess solid electrolyte interface to a reasonable range. The optimized material is used as an advanced anode for both lithium‐ion and potassium‐ion batteries, and good battery behavior including high‐rate performance and high stability is achieved.     

A doubly bridged isodicyclopentadienyl zirconium complex: bis{N‐(3,5‐dimethylphenyl)‐N‐[(η5‐isodicyclopentadien‐2‐yl)dimethylsilyl]amido‐κN}zirconium(II) diethyl ether solvate

Transmetallation of the dilithium salt of (3,5‐dimethyphenyl­amino)(isodicyclopentadienyl)dimethylsilane by treatment with zirconium tetrachloride in a 2:1 ratio leads to the substitution of all four chloride ligands. With the applied stoichiometry, the title complex, [Zr(C₂₀H₂₅NSi)₂]·C₄H₁₀O, was obtained and crystallized from diethyl ether. X‐ray diffraction characterization showed that both isodi­cyclo­penta­dienyl ligands (alternatively called 4,5,6,7‐tetrahydro‐4,7‐methano‐1H‐indene) are complexed to the metal on their exo face in a completely stereoselective manner and that they are η⁵‐bonded to the Zr atom.     

A two‐step reaction scheme leading to singlet carbene species that can be detected under matrix conditions for the reaction of Zr(3F) with either CH3F or CH3CN

The results obtained from CASSCF‐MRMP2 calculations are used to rationalize the singlet complexes detected under matrix‐isolation conditions for the reactions of laser‐ablated Zr(³F) atoms with the CH₃F and CH₃CN molecules, without invoking intersystem crossings between electronic states with different multiplicities. The reaction Zr(³F) + CH₃F evolves to the radical products ZrF· + ·CH₃. This radical asymptote is degenerate to that emerging from the singlet channel of the reactants Zr(¹D) + CH₃F because they both exhibit the same electronic configuration in the metal fragment. Hence, the caged radicals obtained under cryogenic‐matrix conditions can recombine through triplet and singlet paths. The recombination of the radical species along the low‐multiplicity channel produces the inserted structures H₃C? Zr? F and H₂C?ZrHF experimentally detected. For the Zr(³F) + CH₃CN reaction, a similar two‐step reaction scheme involving the radical fragments ZrNC· + ·CH₃ explains the presence of the singlet complexes H₃C? Zr? NC and H₂C?Zr(H)NC revealed in the IR‐matrix spectra upon UV irradiation. © 2014 Wiley Periodicals, Inc.     

Chemical solution processing and characterization of Ba(Zr,Ti)O<Subscript>3</Subscript>/LaNiO<Subscript>3</Subscript> layered thin films

Ba(Zr,Ti)O₃/LaNiO₃ layered thin films have been synthesized by chemical solution deposition (CSD) using metal-organic precursor solutions. Ba(Zr,Ti)O₃ thin films with smooth surface morphology and excellent dielectric properties were prepared on Pt/TiO _x /SiO₂/Si substrates by controlling the Zr/Ti ratios in Ba(Zr,Ti)O₃. Chemically derived LaNiO₃ thin films crystallized into the perovskite single phase and their conductivity was sufficiently high as a thin-film electrode. Ba(Zr,Ti)O₃/LaNiO₃ layered thin films of single phase perovskite were fabricated on SiO₂/Si and fused silica substrates. The dielectric constant of a Ba(Zr_0.2Ti_0.8)O₃ thin film prepared at 700°C on a LaNiO₃/fused silica substrate was found to be approximately 830 with a dielectric loss of 5% at 1 kHz and room temperature. Although the Ba(Zr_0.2Ti_0.8)O₃ thin film on the LaNiO₃/fused silica substrate showed a smaller dielectric constant than the Ba(Zr_0.2Ti_0.8)O₃ thin film on Pt/TiO _x /SiO₂/Si, small temperature dependence of dielectric constant was achieved over a wide temperature range. Furthermore, the fabrication of the Ba(Zr,Ti)O₃/LaNiO₃ films in alternate thin layers similar to a multilayer capacitor structure was performed by the same solution deposition process.     

Nanostructured ZrO2 and Zr‐C‐N Coatings from Chemical Vapor Deposition of Metal‐Organic Precursors

Nanocrystalline zirconium carbonitride (Zr‐C‐N) and zirconium oxide (ZrO₂) films were deposited by chemical vapor deposition (CVD) of zirconium‐tetrakis‐diethylamide (Zr(NEt₂)₄) and ‐tert‐butyloxide (Zr(OBu^t)₄), respectively. The films were deposited on iron substrates and characterized by scanning electron microscopy (SEM), X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS). The Zr‐C‐N films show blue, golden brown or bronze colours, with colour stability depending upon the precursor composition (pure metal amide or mixed with Et₂NH). The deposition temperature showed no pronounced effect on the granular morphology of the Zr‐C‐N films. The XRD data of the films correspond to the formation of carbonitride phase whereas the XPS analyses revealed a strong surface oxidation and incorporation of oxygen in the film. The films deposited using a mixture of Zr(NEt₂)₄ and Et₂NH showed higher N content, better adhesion and scratch resistance when compared to films obtained from the CVD of pure Zr(NEt₂)₄. Subject to the precursor composition and deposition temperature (550‐750 °C), the microhardness values of Zr‐C‐N films were found to be in the range 2.11‐5.65 GPa. For ZrO₂ films, morphology and phase composition strongly depend on the deposition temperature. The CVD deposits obtained at 350 °C show tetragonal ZrO₂ to be the only crystalline phase. Upon increasing the deposition temperature to 450 °C, a mixture of tetragonal and monoclinic modifications was formed with morphology made up of interwoven elongated grains. At higher temperatures (550 and 650 °C), pure monoclinic phase was obtained with facetted grains and developed texture.     

Specific recognition of ribavirin in animal‐derived foods by high performance liquid chromatography combined with magnetic solid‐phase extraction based on highly selective Zr‐Fe3O4

For the first time, a magnetic solid‐phase extraction with high‐performance liquid chromatography detection method using Zr functionalized Fe₃O₄ magnetic material to enrich ribavirin was successfully established. Zr components that modified in Fe₃O₄ nanoparticles via a simple one‐step hydrothermal method was selected in this work to specifically capture ribavirin by the strong chemical bonding between Zr components of Zr functionalized Fe₃O₄ magnetic material and cis‐hydroxyl of ribavirin, which was confirmed by pseudo‐second‐order kinetic model. And Fe₃O₄ components were selected in this work to achieve simple operation. Under the optimal experimental conditions, proposed magnetic solid‐phase extraction with high‐performance liquid chromatography detection method along with Zr functionalized Fe₃O₄ magnetic material offered a wide range linearity at 10–200 µg/L with correlation coefficient of 0.9978 with low detection limit of 2.68 µg/L for ribavirin. The relative standard deviations obtained from nine parallel extractions of 100 µg/L ribavirin were 4.41% and revealed good repeatability. This established method was successfully applied to detect real samples including chicken liver, egg, and shrimp with satisfactory recoveries of 74.13–92.9%.     

H‐doped PbTiO3: Structure and electronic properties

The geometry and electronic properties of the interstitial H atom in the tetragonal PbTiO₃ crystal have been studied using an advanced quantum chemical computer code developed for the modeling of crystals. The inserted H atom was found to bind to one of the O atoms and to form the hydroxyl, O? H group, with the inter‐atomic distance equal to 0.93 Å and 1.00 Å for the hydroxyls containing O atom in the dimerized and nondimerized Ti? O? Ti chains, respectively. Atomic displacements in the vicinity of O? H complex are calculated and analyzed in relation to the H‐produced changes upon the atomic charges in defective region. The role of H impurity on the ferroelectric polarization in the tetragonal PbTiO₃ is discussed in terms of the results obtained in our research and those presented in the other studies on this subject. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Preparation and application of a novel core–shell‐particle‐supported zirconocene catalyst

The use of functional groups bearing silica/poly(styrene‐co‐4‐vinylpyridine) core–shell particles as a support for a zirconocene catalyst in ethylene polymerization was studied. Several factors affecting the behavior of the supported catalyst and the properties of the resulting polymer, such as time, temperature, Al/N (molar ratio), and Al/Zr (molar ratio), were examined. The conditions of the supported catalyst preparation were more important than those of the ethylene polymerization. The state of the supported catalyst itself played a decisive role in both the catalytic behavior of the supported catalyst and the properties of polyethylene (PE). IR and X‐ray photoelectron spectroscopy were used to follow the formation of the supports. The formation of cationic active species is hypothesized, and the performance of the core–shell‐particle‐supported zirconocene catalyst is discussed as well. The bulk density of the PE formed was higher than that of the polymer obtained from homogeneous and polymer‐supported Cp₂ZrCl₂/methylaluminoxane catalyst systems. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2085–2092, 2001     

Improvement in Hydrogen Desorption from β‐ and γ‐MgH2 upon Transition‐Metal Doping

A thorough study of the structural, electronic, and hydrogen‐desorption properties of β‐ and γ‐MgH₂ phases substituted by selected transition metals (TMs) is performed through first‐principles calculations based on density functional theory (DFT). The TMs considered herein include Sc, V, Fe, Co, Ni, Cu, Y, Zr, and Nb, which substitute for Mg at a doping concentration of 3.125 % in both the hydrides. This insertion of TMs causes a variation in the cell volumes of β‐ and γ‐MgH₂. The majority of the TM dopants decrease the lattice constants, with Ni resulting in the largest reduction. From the formation‐energy calculations, it is predicted that except for Cu and Ni, the mixing of all the selected TM dopants with the MgH₂ phases is exothermic. The selected TMs also influence the stability of both β‐ and γ‐MgH₂ and cause destabilization by weakening the Mg?H bonds. Our results show that doping with certain TMs can facilitate desorption of hydrogen from β‐ and γ‐MgH₂ at much lower temperatures than from their pure forms. The hydrogen adsorption strengths are also studied by density‐of‐states analysis.     

Charge‐Transfer Mechanism in Pt/KTa(Zr)O3 Photocatalysts Modified with Porphyrinoids for Water Splitting

The mechanism of photocatalytic splitting of H₂O into H₂ and O₂ on Pt/KTa(Zr)O₃ modified with various porphyrinoids was investigated. The photocatalytic activity of KTaO₃ catalysts is improved by dye modification. Cyanocobalamin (vitamin B₁₂) is the most effective for improving water‐splitting activity, and the formation rates of H₂ and O₂ achieved values of 575 and 280 μmol g_cat.^?1 h^?1, respectively. X‐ray photoelectron spectroscopy spectra of KTa(Zr)O₃ photocatalysts showed that Pt loaded onto dye‐modified KTaO₃ was slightly oxidized and had low catalytic activity for the H₂ oxidation reaction. Photoluminescence (PL) spectra of KTaO₃ catalysts suggested that excitation energy was transferred between KTaO₃, tetraphenylporphyrinatochromium(III) (Cr–TPP), and the Pt cocatalyst. The wavelength dependence of the activity of dye‐modified KTa(Zr)O₃ photocatalysts indicated that excitation of both KTa(Zr)O₃ and the dye was essential for achieving increased photocatalytic activity. This result suggests that two‐step excitation occurred in the dye‐modified KTa(Zr)O₃ photocatalysts. Because the lifetime of the charge‐separated state increased, this study reveals that modification with porphyrinoids is effective for increasing water‐splitting activity.     

Copolymerization of propylene with various higher α‐olefins using silica‐supported rac‐Me2Si(Ind)2ZrCl2

The copolymerization of propylene with 1‐hexene, 1‐octene, 1‐decene, and 1‐dodecene was carried out with silica‐supported rac‐Me₂Si(Ind)₂ZrCl₂ as a catalyst. The copolymerization activities of the homogeneous and supported catalysts and the microstructures of the resulting copolymers were compared. The activity of the supported catalyst was only one‐half to one‐eighth of that of the homogeneous catalyst, depending on the comonomer type. The supported catalyst copolymerized more comonomer into the polymer chain than the homogeneous catalyst at the same monomer feed ratio. Data of reactivity ratios showed that the depression in the activity of propylene instead of an enhancement in the activity of olefinic comonomer was responsible for this phenomenon. We also found that copolymerization with α‐olefins and supporting the metallocene on a carrier improved the stereoregularity and regioregularity of the copolymers. The melting temperature of all the copolymers decreased linearly with growing comonomer content, regardless of the comonomer type and catalyst system. Low mobility of the propagation chain in the supported catalyst was suggested as the reason for the different polymerization behaviors of the supported catalyst with the homogeneous system. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3294–3303, 2001     

Surviving High‐Temperature Calcination: ZrO2‐Induced Hematite Nanotubes for Photoelectrochemical Water Oxidation

Nanotubular Fe₂O₃ is a promising photoanode material, and producing morphologies that withstand high‐temperature calcination (HTC) is urgently needed to enhance the photoelectrochemical (PEC) performance. This work describes the design and fabrication of Fe₂O₃ nanotube arrays that survive HTC for the first time. By introducing a ZrO₂ shell on hydrothermal FeOOH nanorods by atomic layer deposition, subsequent high‐temperature solid‐state reaction converts FeOOH‐ZrO₂ nanorods to ZrO₂‐induced Fe₂O₃ nanotubes (Zr‐Fe₂O₃ NTs). The structural evolution of the hematite nanotubes is systematically explored. As a result of the nanostructuring and shortened charge collection distance, the nanotube photoanode shows a greatly improved PEC water oxidation activity, exhibiting a photocurrent density of 1.5 mA cm⁻² at 1.23 V (vs. reversible hydrogen electrode, RHE), which is the highest among hematite nanotube photoanodes without co‐catalysts. Furthermore, a Co‐Pi decorated Zr‐Fe₂O₃ NT photoanode reveals an enhanced onset potential of 0.65 V (vs. RHE) and a photocurrent of 1.87 mA cm⁻² (at 1.23 V vs. RHE).     

Substituent effects on the Bergman cyclization of (Z)‐1,5‐hexadiyne‐3‐enes: a systematic computational study

The effects of several substituents (? BH₂, ? BF₂, ? AlH₂, ? CH₃, ? C₆H₅, ? CN, ? COCH₃, ? CF₃, ? SiH₃, ? NH₂, ? NH₃⁺, ? NO₂, ? PH₂, ? OH, ? OH₂⁺, ? SH, ? F, ? Cl, ? Br) on the Bergman cyclization of (Z)‐1,5‐hexadiyne‐3‐ene (enediyne, 3 ) were investigated at the Becke–Lee–Yang–Parr (BLYP) density functional (DFT) level employing a 6‐31G* basis set. Some of the substituents (? NH₃⁺, ? NO₂, ? OH, ? OH₂⁺, ? F, ? Cl, ? Br) are able to lower the barrier (up to a minimum of 16.9 kcal mol^?1 for difluoro‐enediyne 7rr ) and the reaction enthalpy (the cyclization is predicted to be exergonic for ? OH₂⁺ and ? F) compared to the parent system giving rise to substituted 1,4‐dehydrobenzenes at physiological temperatures. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1605–1614, 2001     

Influence of the preparation conditions of Pd‐ZrO2 and AuPd‐ZrO2 nanoparticle–decorated functionalised MWCNTs: Electron spectroscopy study aided with the QUASES

The Pd, AuPd, and ZrO₂ nanoparticle–decorated functionalised multiwalled carbon nanotubes (f‐MWCNTs) were reported as efficient catalysts of formic acid (FA) electro‐oxidation. Different preparation conditions influence their chemical and structural properties analysed by X‐ray photoelectron spectroscopy aided with the quantitative analysis of surfaces by electron spectroscopy. Different reduction procedures such as NaBH₄, a polyol microwave‐assisted method (PMWA), and a high pressure microwave reactor (HPMWR) were applied for decorating ZrO₂/f‐MWCNTs with Pd and AuPd nanoparticles. The ZrO₂ nanoparticles are attached through oxygen groups to the surface of f‐MWCNTs. In NaBH₄ and HPMWR procedures, Pd nanoparticles precipitate predominantly on ZrO₂ of nearly nominal stoichiometry, whereas in PMWA procedure, Pd and AuPd nanoparticles precipitate predominantly on the surface of f‐MWCNTs, bridging with oxygen groups and ZrO_x (x < 2) and leading to Pd‐O‐Zr phase formation. Strong reducing procedures (NaBH₄ and FA) led to smaller Pd nanoparticle size, Pd oxide content, and PdO_x overlayer thickness in contrary to weak reduction procedures (HPMWR and PMWA). The highest content of Pd‐O‐Zr phase appeared for Pd predominant precipitation on ZrO₂ nanoparticles (HPMWR) in contrary to Pd and AuPd predominant precipitation on surface of f‐MWCNTs (NaBH₄ ~ FA > PMWA). Larger content of Pd‐O‐Zr phase in AuPd‐decorated ZrO₂/f‐MWCNTs in contrary to Pd‐decorated sample (PMWA) could be justified by different electronic properties of nanoparticles. The FA treatment of Pd and AuPd‐ZrO₂/f‐MWCNTs samples provided decreasing Pd oxide content, overlayer thickness, nanoparticle size, increasing nanoparticle surface coverage and density, amount of Pd‐O‐Zr, what results from reduction of oxygen groups bridging with Pd and ZrO_x nanoparticles, also through Pd‐O‐Zr phase.