Preparation of Cu-doped TiO2 via refluxing of alkoxide solution and its photocatalytic properties

Cu-doped TiO₂ was prepared by the refluxing of a mixture of copper and titanium alkoxides. The refluxing improved the Cu²⁺ dispersion in the TiO₂ and formed effective Ti–O–Cu bonds. The impurity states due to the highly dispersed Cu²⁺ were presumed to trap the electrons in the conduction band of the TiO₂ and prevent charge recombination of the electrons and holes. Consequently, the prolonged charge separation duration was suggested to enhance the photocatalytic activity of the Cu-doped TiO₂. This enhancement was confirmed by the hydroxyl radical generation and organic compound degradation. The Ti–O–Cu bonds and electronic interaction between Cu and Ti should effectively promote the electron trapping. The Cu-doped TiO₂ exhibited a visible light-induced activity due to the transition from the TiO₂ valence band to the Cu²⁺ impurity states.     

Hydrogen permeation of tungsten phosphate glass thin films

Thin films of tungsten phosphate glasses were deposited on a Pd substrate by a pulsed laser deposition method and the flux of hydrogen passed thorough the glass film was measured with a conventional gas permeation technique in the temperature range 300–500 °C. The glass film deposited at low oxygen pressure was inappropriate for hydrogen permeation because of reduction of W ions due to oxygen deficiency. The membrane used in the hydrogen permeation experiment was a 3-layered membrane and consisted of Pd film (~ 20 nm), the glass film (≤ 300 nm) and the Pd substrate (250 µm). When the pressure difference of hydrogen and thickness of the glass layer were respectively 0.2 MPa and ~ 100 nm, the permeation rate through the membrane was 2.0 × 10^? 6 mol cm^? 2 s^? 1 at 500 °C. It was confirmed that the protonic and electronic mixed conducting glass thin film show high hydrogen permeation rate.     

Catalytic Reactivity of Molybdenum–Trihalide Complexes Bearing PCP‐Type Pincer Ligands

Molybdenum–iodide complexes bearing a PCP[1] ligand have been found to work as excellent catalysts toward ammonia formation under ambient reaction conditions among dinitrogen‐bridged dimolybdenum complexes and other molybdenum complexes bearing PNP and PCP[2] ligands.     

Observation of Resonant Photon Tunneling in Photonic Double Barrier Structures

Reflectance and transmittance of 632.8 nm He-Ne laser light for photonic double barrier structures (consisting of a SF10 prism, SiO₂ layer, Al or Al₂O₃ active layer, SiO₂ layer and SF10 prism) were measured as a function of the angle of incidence for both the ρ- and s-polarized incidence. Sharp reflection dips and transmission peaks were observed at angles larger than the critical angle of total reflection. The appearance of the transmission peaks can be attributed to resonant photon tunneling through the photonic double barrier structures analogous to resonant electron tunneling through double potential barrier structures. Resonant tunneling is mediated by the long-range surface plasmon polariton in the case of the Al active layer and the electromagnetic guided modes in the case of the Al₂O₃ layer.This paper was originally presented at the seventh Meeting on Near Field Optics, which was held on July 1, 1998 at Nagoya University, Nagoya, organized by Research Group on Near Field Optics, the Optical Society of Japan, an affiliate of Japan Society of Applied Physics. The authors have won the Near Field Optics Award for their best presentation at the meeting.     

Theoretical Study on Redox Potential Control of Iron-Sulfur Cluster by Hydrogen Bonds: A Possibility of Redox Potential Programming

The effect of hydrogen bonds around the active site of Anabaena [2Fe-2S] ferredoxin (Fd) on a vertical ionization potential of the reduced state (IP(red)) is examined based on the density functional theory (DFT) calculations. The results indicate that a single hydrogen bond increases the relative stability of the reduced state, and shifts IP(red) to a reductive side by 0.31–0.33 eV, regardless of the attached sulfur atoms. In addition, the IP(red) value can be changed by the number of hydrogen bonds around the active site. The results also suggest that the redox potential of [2Fe-2S] Fd is controlled by the number of hydrogen bonds because IP(red) is considered to be a major factor in the redox potential. Furthermore, there is a possibility that the redox potentials of artificial iron-sulfur clusters can be finely controlled by the number of the hydrogen bonds attached to the sulfur atoms of the cluster.     

Liquid Crystal Auto-Induction and Amplification Function for Circularly Polarized Luminescence (CPL) with High gem-Value,and Dynamically Controllable CPL Devices

Optically active phenylenevinylene derivatives with fluorescence are employed for preparation of a cholesteric liquid crystal based circularly polarized light (CPL) emission device. The device shows intense CPL with a quite large value of the g_em-factor (= 0.6) and quick CPL light switching driven by cholesteric-nematic transition with a homeotropic alignment. This research develops the auto-induction of fluorescent chiral inducers in host liquid crystal for formation of a helical structure with CPL amplification. The present research applies a classical LC light-scattering system using chiral technology as a new method for obtaining CPL dynamic control with an intense g_em-factor.     

Visible‐Light Sensitization and Photoenergy Storage in Quantum Dot/Polyoxometalate Systems

Recently, the process by which energy is transferred from photoexcited semiconductor nanocrystals, called quantum dots (QDs), to other semiconductors has attracted much attention and has potential application in solar energy conversion (i.e., QD‐sensitized solar cells). Sensitization of wide band gap polyoxometalates (POMs) to visible light by using CuInS₂ QDs dispersed in an organic solution is demonstrated herein. Photoluminescence quenching and lifetime studies revealed efficient electron transfer from the CuInS₂ QDs to POMs, such as SiW₁₂O₄₀ and W₁₀O₃₂, that were hybridized with a cationic surfactant. CuInS₂ QDs function as an antenna that absorbs visible light and supplies electrons to the POMs to enable certain photocatalytic reactions, including noble‐metal‐ion reduction. The photoenergy storage capabilities of the QD‐POM system, in which electrons photogenerated in QDs by visible‐light excitation are trapped and accommodated by POMs to form reduced POM, are also demonstrated. Electrons stored in the POM can be later discharged through reductive reactions, such as oxygen reduction, in the dark.     

Syntheses and Odor Descriptions of Cyclopropanated Compounds. Part 5

Analogs of methyl jasmonate (=methyl (1R*,2R*)‐3‐oxo‐2‐[(Z)‐pent‐2‐enyl]cyclopentaneacetate; MJA) bearing a cyclopropane ring, double bond, or a F‐substituent were synthesized, and their odor characteristics were examined. Most of the analogs with the same stereochemical properties as methyl epijasmonate showed odor properties superior to MJA. Interestingly, the enol acetate of MJA had a diffusive orchid‐like note.