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251.
We have prepared π-conjugated organic dye specimens embedded in a transparent polymer film and observed a characteristic photoluminescence peak, having very narrow peak width as compared with the fluorescence in solution, when we prepared the film around the perimeter of a multimode silica fiber. The peak position showed no dependence on the excitation wavelength, indicating that it could not be explained by a whispering gallery mode. The peaks can be explained by amplified spontaneous emissions (ASE) because the intensity depended linearly on the excitation intensity with some threshold. When the excitation laser was directly coupled to the fiber core, we observed ASE peaks of the optical fiber itself. These fiber ASE peaks shifted to longer wavelength when we varied the excitation to shorter wavelength, which clearly ruled out the possibility of silicate Raman scattering as the origin. 相似文献
252.
Surudee Treetepvijit Suchada Chuanuwatanakul Yasuaki Einaga Rika Sato Orawon Chailapakult 《Analytical sciences》2005,21(5):531-535
The electrochemical analysis of tetracycline was investigated using nickel-implanted boron-doped diamond thin film electrode by cyclic voltammetry and amperometry with a flow injection system. Cyclic voltammetry was used to study the electrochemical oxidation of tetracycline. Comparison experiments were carried out using as-deposited boron-doped diamond thin film electrode (BDD). Nickel-implanted boron-doped diamond thin film electrode (Ni-DIA) provided well-resolved oxidation irreversible cyclic voltammograms. The current signals were higher than those obtained using the as-deposited BDD electrode. Results using nickel-implanted boron-doped diamond thin film electrode in flow injection system coupled with amperometric detection are presented. The optimum potential for tetracycline was 1.55 V versus Ag/AgCl. The linear range of 1.0 to 100 microM and the detection limit of 10 nM were obtained. In addition, the application for drug formulation was also investigated. 相似文献
253.
Dynamics of Photoelectrons and Structural Changes of Tungsten Trioxide Observed by Femtosecond Transient XAFS
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Prof. Yohei Uemura Daiki Kido Dr. Yuki Wakisaka Dr. Hiromitsu Uehara Dr. Tadashi Ohba M.Sc. Yasuhiro Niwa Dr. Shunsuke Nozawa Dr. Tokushi Sato Dr. Kohei Ichiyanagi Dr. Ryo Fukaya Prof. Shin‐ichi Adachi Dr. Tetsuo Katayama Dr. Tadashi Togashi Dr. Sigeki Owada Dr. Kanade Ogawa Dr. Makina Yabashi Dr. Keisuke Hatada Prof. Satoru Takakusagi Prof. Toshihiko Yokoyama Prof. Bunsho Ohtani Prof. Kiyotaka Asakura 《Angewandte Chemie (International ed. in English)》2016,55(4):1364-1367
The dynamics of the local electronic and geometric structures of WO3 following photoexcitation were studied by femtosecond time‐resolved X‐ray absorption fine structure (XAFS) spectroscopy using an X‐ray free electron laser (XFEL). We found that the electronic state was the first to change followed by the local structure, which was affected within 200 ps of photoexcitation. 相似文献
254.
Construction of Hexahydrophenanthrenes By Rhodium(I)‐Catalyzed Cycloisomerization of Benzylallene‐Substituted Internal Alkynes through C−H Activation
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Yasuaki Kawaguchi Dr. Shigeo Yasuda Prof. Dr. Chisato Mukai 《Angewandte Chemie (International ed. in English)》2016,55(35):10473-10477
The treatment of benzylallene‐substituted internal alkynes with [RhCl(CO)2]2 effects a novel cycloisomerization by C(sp2)?H bond activation to produce hexahydrophenanthrene derivatives. The reaction likely proceeds through consecutive formation of a rhodabicyclo[4.3.0] intermediate, σ‐bond metathesis between the C(sp2)?H bond on the benzene ring and the C(sp2)?RhIII bond, and isomerization between three σ‐, π‐, and σ‐allylrhodium(III) species, which was proposed based on experiments with deuterated substrates. 相似文献
255.
256.
Yasuaki Tokudome Tetsuo Sato Motohiko Hidaka Masahide Takahashi 《Journal of Sol-Gel Science and Technology》2013,65(3):318-323
For functional hybrid materials with desirable physical properties as well as chemical characteristics, controlled modification, i.e., site selective modification, of inorganic networks is one of the promising approaches. Here, we report a selective modification of less-condensed Si atoms in a siloxane-based UV-cured resin can drastically improve thermal crack resistance. The highly improved thermal crack resistance is attained by elimination of monomeric Si alkoxides using trimethylchlorosilane (TMCS) as a modifier. Liquid- and solid-state 29Si NMR analyses were performed to evaluate the selectivity of reaction between TMCS and monomeric Si alkoxides included in photocurable precursory sols, whereas thermal mechanical analysis was to estimate coefficients of thermal expansion and deformation temperature of the UV-cured resins. The reaction between TMCS and the UV curable precursory sol occurs via a moisture-assisted process involving moderate hydrolysis reactions. As a result, the addition of TMCS increases a temperature at which crack forms from 150 up to 300 °C. 相似文献
257.
258.
Yasuaki Okamoto Yoshitaka Nomura Hiderou Nakamura Kazuyuki Iwamaru Terufumi Fujiwara Takahiro Kumamaru 《Microchemical Journal》2000,65(3):66
A high preconcentration method by liquid–liquid extraction using liquid surfactant membranes was developed. The water-in-oil (w/o) emulsion containing dilute hydrochloric acid, 2-ethylhexyl hydrogen 2-ethylhexylphosphonate (PC-88A), liquid paraffin, and kerosene was used for the extraction. In a resulting volume of 1000 cm3 of an aqueous sample solution (pH 5.0) containing less than 1 mg of each metal ion, 2 cm3 of w/o emulsion droplets coated with sorbitan monooleate were dispersed. The analyte metal ions in the outer bulk aqueous phase were extracted into the organic phase to form a complex with PC-88A and successively back-extracted into the inner aqueous phase. The analytes in the resulting inner aqueous phase were determined subsequently by graphite furnace atomic absorption spectrometry applied as a detector. By this procedure, concentration factors of 570, 820, 750, 970, 860, and 880 were achieved for chromium(III), manganese(II), cobalt(II), nickel(II), copper(II), and cadmium(II), respectively, and also the respective detection limits (3σ) of 0.4, 20, 1.2, 18, 18, and 0.7 pg cm−3 were obtained. 相似文献
259.
Shirafuji Tatsuru Miyazaki Yasuo Hayashi Yasuaki Nishino Shigehiro 《Plasmas and Polymers》1999,4(1):57-75
Plasma copolymerization of hexamethyldisiloxane (HMDSO,(CH3)3-Si-O-Si-(CH3)3) and C4F8 was performed using an RF plasma enhanced chemical vapor deposition method for application to low dielectric constant intermetal dielectrics. Structure of the films was investigated by X-ray photoelectron spectroscopy and Fourier transform infrared (FT-IR) spectroscopy. The film composition was controlled gradually from fluorinated carbon to organic siloxane by changing the mixing ratio of HMDSO/Ar. Dielectric constant of the films ranged from 2–3.3. Thermal stability of the films, which was characterized by intensity loss of IR absorbance peak around 1000–1500 cm–1 corresponding to C-F
n
, Si-O-Si and Si-(CH2)n-Si bonds, was inferior to that from C2F4/HMDSO/Ar. In situ gasphase FT-IR spectroscopy revealed that there was a marked difference between the gas phase of C4F8/HMDSO/Ar and that of C2F4/HMDSO/Ar discharges. The IR spectrum of the former combination plasma contained a peak at 1250 cm–1 with full width at half maximum as large as 150 cm–1, which suggests that fluorocarbon particles and/or dusts are formed in the plasma. This suggests also that deposition precursors are not only CF
n
(n = 1, 2, and 3) but also larger precursors such as C
x
F
y
(x > 1, y < 2x + 2) in C4F8/HMDSO/Ar discharges, which is presumably the cause of difference in thermal stability of the films prepared from C4F8/HMDSO/Ar and C2F4/HMDSO/Ar mixtures. 相似文献
260.
Utilising extremely different vaporisation properties of boron compounds, the determination procedures of volatile boric acid and total boron using tungsten boat furnace (TBF) ICP-MS and TBF-ICP-AES have been investigated. For the determination of volatile boric acid by TBF-ICP-MS, tetramethylammonium hydroxide (TMAH, Me4NOH) was used as a chemical modifier to retain it during drying and ashing stages. As for the total boron, not only non-volatile inorganic boron such as boron nitride (BN), boron carbide (B4C), etc. but also boric acid (B(OH)3) was decomposed by a furnace-fusion digestion with NaOH to produce sodium salt of boron, a suitable species for the electrothermal vaporisation (ETV) procedure. The proposed method was applied to the analysis of various standard reference materials. The analytical results for various biological and steel samples are described. 相似文献