Orbital Interaction and Electron Density Transfer in PdII([9]aneB2A)L2 Complexes: Theoretical Approaches

The geometric structures of Pd-complexes {Pd([9]aneB2A)L2 and Pd([9]aneBAB)L2 where A = P, S; B = N; L = PH3, P(CH3)3, Cl−}, their selective orbital interaction towards equatorial or axial (soft A…Pd) coordination of macrocyclic [9]aneB2A tridentate to PdL2, and electron density transfer from the electron-rich trans L-ligand to the low-lying unfilled a1g(5s)-orbital of PdL2 were investigated using B3P86/lanl2DZ for Pd and 6-311+G** for other atoms. The pentacoordinate endo-[Pd([9]aneB2A)(L-donor)2]2+ complex with an axial (soft A--Pd) quasi-bond was optimized for stability. The fifth (soft A--Pd) quasi-bond between the σ-donor of soft A and the partially unfilled a1g(5s)-orbital of PdL2 was formed. The pentacoordinate endo-Pd([9]aneB2A)(L-donor)2]2+ complex has been found to be more stable than the corresponding tetracoordinate endo-Pd complexes. Except for the endo-Pd pentacoordinates, the tetracoordinate Pd([9]aneBAB)L2 complex with one equatorial (soft A-Pd) bond is found to be more stable than the Pd([9]aneB2A)L2 isomer without the equatorial (A-Pd) bond. In particular, the geometric configuration of endo-[Pd([9]anePNP)(L-donor)2]2+ could not be optimized

Photocatalytic Ohmic layered nanocomposite for efficient utilization of visible light photons

The WO3/W/PbBi2Nb1.9Ti0.1O9 photocatalyst was fabricated by depositing the tungsten clusters over the p-type perovskite base material with the chemical vapor deposition method, and later partly oxidizing the surfaces of these clusters to obtain n-type WO3 overlayers and W metal layer as an Ohmic junction. This NCPC showed unprecedented high activity for the photocatalytic oxidation of water, photocurrent generation, and acetaldehyde decomposition under visible light irradiation (lambda >= 420 nm). (c) 2006 American Institute of Physicsclose313

Band gap tuning of lead-substituted BaSnO3 for visible light photocatalysis

The Pb substitution effect was investigated experimentally and theoretically on the crystal structure of BaSnO3 and on the photo-oxidation activity of H2O. The chemically doped Pb in BaSnO3 induced a concentration-dependent redshift of the experimental band gap (BG). The BaPb0.8Sn0.2O3 system produced 32 mu mol/h of O-2 under lambda >= 420 nm photons, but no O-2 for BaSnO3. The DFT calculations of BaPbxSn1-xO3 (x=0,0.5,1) by using generalized approximation, implying the BG alteration and the photocatalytic activity of BaPbxSn1-xO3, are due to the induced Pb 6s orbital in the BG of BaSnO3. Thus Pb modified the insulating nature of BaSnO3 to semiconducting and semimetallic. (c) 2007 American Institute of Physicsclose343

Enhancement of the electrochemical performance in LiFePO4 cathode materials synthesized by using the sol-gel method

LiFePO4 powders were synthesized by using the sol-gel and the solid-state reaction methods. The chemical states of Fe ions were studied by using XPS, and their electrochemical properties according to the oxidation states of Fe ions were compared. The average oxidation state of Fe ions in LiFePO4 powders synthesized by using the solid-state reaction method was found to be Fe3+, on the other hand, that of Fe ions synthesized by using the sol-gel method was found to be Fe2+. The obtained discharge capacities were 50 mAh/g and 120 mAh/g at a rate 0.1 C in LiFePO4 synthesized by using the solid-state reaction and sol-gel methods, respectively. Relatively a good cycling stability was observed in sol-gel prepared powder

Enhanced photochemical properties of electron rich W-doped PbBi2Nb2O9 layered perovskite material under visible-light irradiation

The substitution effect of W6+ at Nb5+ site in PbBi2Nb2O9, a layered Aurivillius-phase perovskite system, has been studied and further optimized to fabricate an efficient photocatalyst. The material doped with electron donor (W+6), PbBi2Nb2-xWxO9 with an optimum composition of x = 0.15 exhibited a red shifted (0.14 eV) band gap, generated two times higher photocurrent, and showed analogous higher quantum yield for photodecomposition of H2O/CH3OH solution than undoped material under visible light ((lambda >= 420 nm). In contrast, the material doped with hole donor (Ti+4) revealed deteriorated photochemical properties. The higher electron density by n-type doping seems to be responsible for the more efficient charge separation in PbBi2Nb2-xWxO9 (0<x<0.5). (C) 2007 Elsevier B.V. All rights reservedclose151

Engineered Nanorod Perovskite Film Photocatalysts to Harvest Visible Light

A uniform array of Aurivillius phase perovskite PbBi(2)Nb(2)O(9) photocatalyst in a nanorod configuration is fabricated on a conducting glass as a photoelectrode for a photo-electrochemical water oxidation. Dramatically improved photoactivity is demonstrated for the nanorod electrode compared to a PbBi(2)Nb(2)O(9) particulate electrode. Directional electron transport in crystalline nanorods is faster than percolation through a random polycrystalline particle networkclose33313

Porous Carbon Interlayer Derived from Traditional Korean Paper for Li–S Batteries

A carbonized interlayer effectively helps to improve the electrochemical performance of lithium–sulfur (Li–S) batteries. In this study, a simple and inexpensive carbon intermediate layer was fabricated using a traditional Korean paper called “hanji”. This carbon interlayer has a fibrous porous structure, with a specific surface area of 91.82 m2 g−1 and a BJH adsorption average pore diameter of 26.63 nm. The prepared carbon interlayer was utilized as an intermediary layer in Li–S batteries to decrease the charge-transfer resistance and capture dissolved lithium polysulfides. The porous fiber-shaped carbon interlayer suppressed the migration of polysulfides produced during the electrochemical process. The carbon interlayer facilitates the adsorption of soluble lithium polysulfides, allowing for their re-utilization in subsequent cycles. Additionally, the carbon interlayer significantly reduces the polarization of the cell. This simple strategy results in a significant improvement in cycle performance. Consequently, the discharge capacity at 0.5 C after 150 cycles was confirmed to have improved by more than twofold, reaching 230 mAh g−1 for cells without the interlayer and 583 mAh g−1 for cells with the interlayer. This study demonstrates a simple method for improving the capacity of Li–S batteries by integrating a functional carbon interlayer

Iron-oxide nanoparticles mediated cyclization of 3-(4-chlorophenyl)-1-hydrazinylisoquinoline to 1-(4,5-dihydropyrazol-1-yl)isoquinolines

Iron-oxide nanoparticles were obtained using chitosan templates and their crystalline character and particle size have been confirmed through powder x-ray diffraction and transmission electron microscopy measurements. The particle sizes were found to be 10–25 nm. The diversified chalcones 2 were reacted with 1-hydrazinylisoquinoline 1 in the presence of iron-oxide nanoparticles to the corresponding pyrazolines 3a–j in high yield and purity. The pyrazolines were characterized by spectroscopic techniques

Influence of EDTA in poly(acrylic acid) binder for enhancing electrochemical performance and thermal stability of silicon anode

The crucial roles of ethylenediaminetetraacetic acid (EDTA) in the poly(acrylic acid) (PAA)-binder system were investigated for the high electrochemical performance silicon anode in lithium-ion batteries. The EDTA supports the construction of a mechanically robust network through the formation of sbndCOOH linkage with the SiO2 layer of the Si nanoparticles. The mixture of the PAA/EDTA binder and the conductive agent exhibited an improved elastic modulus and peeling strength. The creation of hydrogen fluoride (HF) was effectively suppressed through the elimination of the H2O. An H2O-phosphorous pentafluoride (PF5) reaction, which is known for its use in the etching of metal oxides including its creation of the solid electrolyte interphase (SEI) layer, generates the HF. A remarkably sound cyclability with a discharge capacity of 2540 mA h g(-1) was achieved as a result of the synergistic effect between robust mechanical properties and suppression of the HF creation for the stability of the SEI layer

Second harmonic generation and fabrication of transparent K2O-Na2O-Nb2O5-TeO2 glass-ceramics

To develop and utilize TeO2-based glasses as nonlinear optical materials or matrix glasses, xK2O- (14-x)Na2O-14Nb2O5-72TeO2 (x=0???14 mol%) glasses were prepared using a conventional melt quenching method and then the nano-crystallization behavior and second harmonic generation (SHG) properties of these glasses were investigated. Although SHG was clearly observed in 10K2O-4Na2O-14Nb2O5-72TeO2 glassceramics consisting of a nano-crystalline phase, the 14Na2O-14Nb2O5-72TeO2 glass-ceramic exhibited no SHG. K+ ions played an important role in inducing SHG in the K2O-Na2O-Nb2O5-TeO2 system.close0