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991.
Yuki Shinno Dr. Kenta Iyoki Dr. Koji Ohara Yutaka Yanaba Dr. Yusuke Naraki Prof. Dr. Tatsuya Okubo Prof. Dr. Toru Wakihara 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(45):20274-20278
The STW-type zeolite is attractive for developing novel enantioselective syntheses/separation of chiral compounds because it is the only chiral zeolitic microporous material whose enantioenriched synthesis has been achieved. In addition to the conventional industries in which zeolites are used, STW should have diverse industrial applications in the pharmaceutical and food industries. However, the toxic and caustic fluoride required for synthesizing STW severely hinders its commercialization by mass production. Herein, we report the first example of fluoride-free STW synthesis, in which the two roles of fluoride—formation of a zeolitic framework rich in tetravalent T-atoms and promotion of double 4-membered ring unit formation—were substituted by dry gel conversion and Ge addition, respectively. The STW obtained was highly crystalline, with a similar micropore volume and thermal stability as those of original fluoride-based STW. Our approach is promising not only for the fluoride-free synthesis of enantiomeric STW but also for general fluoride-free syntheses. 相似文献
992.
Dilshadbek T. Usmanov Satoshi Ninomiya Kenzo Hiraoka 《Journal of the American Society for Mass Spectrometry》2013,24(11):1727-1735
In this paper, the important issue of the desorption of less- and nonvolatile compounds with minimal sample decomposition in ambient mass spectrometry is approached using ambient flash desorption mass spectrometry. The preheated stainless steel filament was driven down and up along the vertical axis in 0.3 s. At the lowest position, it touched the surface of the sample with an invasion depth of 0.1 mm in 50 ms (flash heating) and was removed from the surface (fast cooling). The heating rate corresponds to ~104 °C/s at the filament temperature of 500 °C. The desorbed gaseous molecules were ionized by using a dielectric barrier discharge ion source, and the produced ions were detected by a time-of-flight (TOF) mass spectrometer. Less-volatile samples, such as pharmaceutical tablets, narcotics, explosives, and C60 gave molecular and protonated molecule ions as major ions with thermal decomposition minimally suppressed. For synthetic polymers (PMMA, PLA, and PS), the mass spectra reflected their backbone structures because of the suppression of the sequential thermal decompositions of the primary products. The present technique appears to be suitable for high-throughput qualitative analyses of many types of solid samples in the range from a few ng to 10 μg with minimal sample consumption. Some contribution from tribodesorption in addition to thermal desorption was suggested for the desorption processes. Figure
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993.
Tae Seok Kwon Sadanori Kumazawa Tetsuya Yokoi Shuji Kondo Hideo Kunisada Yasuo Yuki 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(9):1553-1567
Abstract Photopolymerization of styrene in the presence of diphenyl diselenide proceeded smoothly. The polymer yields and the number average molecular weight (Mn) of the polymers increased with reaction time. Further, a linear relationship was found for a plot of Mn for polystyrene versus polymer yield. These results indicate that this polymerization proceeds through a living radical mechanism. Photopolymerization of styrene with bis(p-tertbutylphenyl) diselenide afforded a telechelic polystyrene with terminal arylseleno groups. The resulting polymer underwent the reductive elimination of terminal seleno groups by the reaction with tri-n-butyltin hydride. Moreover, this telechelic polymer was treated with hydrogen peroxide to afford polystyrene with carbon-carbon double bonds at both chain ends. 相似文献
994.
Shuji Kondo Masakazu Takesue Masahiro Suzuki Hideo Kunisada Yasuo Yuki 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(12):2033-2040
Abstract Polymer-supported dimethylformamides were prepared by copolymerization of N-methyl-N-(p-vinylbenzyl)formamide, styrene, and divinylbenzene with AIBN. These polymers displayed catalytic activity for the reaction of alkyl bromides with alkali metal thiocyanates and potassium acetate in a solid-solid-liquid triphase system, although the corresponding monomeric formamides were inactive. The catalytic activity depended remarkably on the copolymer composition. Further, the catalytic reaction was affected by some experimental parameters such as stirring speed, particle size, degree of crosslinking, and solvent. A plausible catalytic reaction mechanism consisting of collisional contact between the solid catalysts and reagents was proposed. 相似文献
995.
Seiji Takahashi Masamichi Tsukagoshi Toshiya Sato Yuki Kitahara Toshihiro Fujii 《Journal of Thermal Analysis and Calorimetry》2013,111(1):685-688
The kinetics of the thermal degradation of Japanese lacquer (urushi) films in N2 and in air were studied by means of thermogravimetry (TG). Thermogravimetric and derivative thermogravimetric curves indicated that the degradation occurred in three stages. The atmosphere influenced the apparent activation energies (E a) of the three degradation stages. The activation energies (E a) for the first stage in N2 and air, obtained from the TG curve, were 19.12 and 10.19 kcal mol?1, respectively, and the corresponding pre-exponential factors (A) were 6.18 × 105 and 1.24 × 102 min?1 for 1-year-old urushi films. 相似文献
996.
A Pt–CeO2 composite thin film was prepared on a glassy carbon electrode by one-step electrochemical deposition technique. The film was constructed of Pt particles well dispersed and embedded in a porous CeO2 substrate. The prepared Pt–CeO2/GC electrode showed a better catalytic performance toward methanol electrooxidation compared with the bulk Pt electrode. 相似文献
997.
Dr. Akira Ueda Hideki Wasa Dr. Shinsuke Nishida Dr. Yuki Kanzaki Prof. Dr. Kazunobu Sato Prof. Dr. Takeji Takui Prof. Dr. Yasushi Morita 《化学:亚洲杂志》2013,8(9):2057-2063
A triangulene‐based C2‐symmetric 33 π‐conjugated stable neutral π‐radical, 2. , which possesses two dicyanomethylene groups and one oxo group, has been designed, synthesized, and isolated as an analogue of tris(dicyanomethylene) derivative 1. and trioxo derivative TOT. with C3 symmetry. Effects of molecular‐symmetry reduction and electron‐accepting substituents on this fused polycyclic neutral π‐radical system were studied in terms of their molecular structure, electronic‐spin structure, and electrochemical and optical properties with the help of theoretical calculations. Interestingly, this system ( 2. ) has a four‐stage redox ability, like TOT. , as well as low frontier energy levels and a small SOMO–LUMO gap, similar to 1. , in spite of the loss of the degenerate LUMOs in symmetry‐lowered 2. , which is associated with the attachment of the weaker electron‐accepting oxo group instead of the dicyanomethylene group in 1. . These prominent results are attributable to the structural and electronic properties in the triangulene‐based highly delocalized fused polycyclic neutral π‐radical system. 相似文献
998.
Daisuke Kosumi Toshiyuki Kusumoto Mitsuru Sugisaki Yoshiro Iinuma Yuki Takaesu Masahiko Iha Hideki Hashimoto 《Journal of luminescence》2011,131(3):515-10770
Ultrafast relaxation kinetics of fucoxanthin in polar and non-polar solvents have been studied by femtosecond pump-probe spectroscopy. Transient absorption associated with S1 or intramolecular charge transfer (ICT) excited state has been observed following either one-photon excitation to the optically allowed S2 state or two-photon excitation to the symmetry-forbidden S1 state. The results suggest that the ICT state formed after excitation of fucoxanthin in a polar solvent is a distinct excited state from S1. 相似文献
999.
Yuki Obukuro Hiroyuki Nakamura Kenji Obata Shigenori Matsushima Masao Arai Kenkichiro Kobayashi 《Journal of Physics and Chemistry of Solids》2011,72(12):1477-1481
The electronic structure of Sr2Bi2O5 is calculated by the GGA approach. Both of the valence band maximum and the conduction band minimum are located at Γ-point. This means that Sr2Bi2O5 is a direct band-gap material. The wide energy-band dispersions near the valence band maximum and the conduction band minimum predict that holes and electrons generated by band gap excitation have a high mobility. The conduction band is composed of Bi 6p, Sr 4d and O 2p energy states. On the other hand, the valence band can be divided into two energy regions ranging from −9.5 to −7.9 eV (lower valence band) and from −4.13 to 0 eV (upper valence band). The former mainly consists of Bi 6s states hybridizing with O 2s and O 2p states, and the latter is mainly constructed from O 2p states strongly interacting with Bi 6s and Bi 6p states. 相似文献
1000.
Yuhei Ishizaka Yuki Kawaguchi Kunimasa Saitoh Masanori Koshiba 《Optics Communications》2011,284(14):3528-3533
We propose a novel ultra-compact all-optical XOR and AND logic gates without using nonlinear optics. In order to realize these devices, we adopt photonic crystal waveguides (PCWs) based on multi-mode interference devices. Numerical results show that the operating bandwidth of the ON to OFF logic-level contrast ratio of not less than 6.79 dB is 35 nm for XOR logic gate and 9 nm for AND logic gate. Proposed logic gates have the potential to be key components for an optical packet switching system due to their small feature sizes and low power consumption. 相似文献