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排序方式: 共有116条查询结果,搜索用时 15 毫秒
71.
Peng Zuo Takao Fuji Takuya Horio Shunsuke Adachi Toshinori Suzuki 《Applied physics. B, Lasers and optics》2012,108(4):815-819
Ultrashort 198- and 158-nm pulses are generated simultaneously by cascaded four-wave mixing of the second and third harmonics of a 80-fs Ti:Sapphire laser in filamentation propagation through a single Ar gas cell. The energies of the 198- and 158-nm pulses are 7.6?μJ and 600?nJ, respectively. The duration of 198-nm pulse is determined to be ca. 45?fs by transient-grating frequency-resolved optical grating, which indicates that the pulse is intrinsically transform limited and chirped by the rear window of the gas cell. The spectral bandwidths of 198- and 158?nm support the transform limited pulse durations of 40 and 28?fs, respectively. 相似文献
72.
Nakamura H Ukai M Shimoyama Y 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2006,63(4):883-887
Using electron spin resonance (ESR) spectroscopy, we revealed the presence of four radical species in gamma-ray irradiated ginseng (Agaliaceae). Before irradiation, the representative ESR spectrum of ginseng is composed of a sextet centered at g = 2.0, a sharp singlet at the same g-value, and a singlet at about g = 4.0. The first one is attributable to a hyperfine (hf) signal of Mn2+ ion (hf constant: 7.4 mT). The second one is due to an organic free radical. The third one is originated from Fe3+. Upon gamma-ray irradiation, a new ESR (the fourth) signal was detectable in the vicinity of g = 2.0 region. The progressive saturation behaviors of the ESR signals at various microwave power levels were indicative of different relaxation time for those radicals. The anisotropic ESR spectra were detected by the angular rotation of the sample tube. This is due to the existence of anisotropic microcrystalline in the ginseng powder sample. 相似文献
73.
Rapid Synthesis of D‐A′‐π‐A Dyes through a One‐Pot Three‐Component Suzuki–Miyaura Coupling and an Evaluation of their Photovoltaic Properties for Use in Dye‐Sensitized Solar Cells
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Shunsuke Irie Dr. Shinichiro Fuse Dr. Masato M. Maitani Prof. Yuji Wada Dr. Yuhei Ogomi Prof. Shuzi Hayase Dr. Tatsuo Kaiho Dr. Hisashi Masui Dr. Hiroshi Tanaka Prof. Takashi Takahashi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(7):2507-2514
Twenty‐four D‐A′–π‐A dyes were rapidly synthesized through a one‐pot three‐component Suzuki–Miyaura coupling reaction, which was assisted by microwave irradiation. We measured the absorption spectra, electrochemical properties, and solar‐cell performance of all the synthesized dyes. The D5 πA4 dye contained our originally designed rigid and nonplanar donor and exerted the highest efficiency at 5.4 %. The short‐circuit current (Jsc) was the most important parameter for the conversion efficiency (η) in the case of the organic D‐A′‐π‐A dyes. Optimal ranges for the D‐A′‐π‐A dyes were observed for high values of Jsc/λmax at λ=560–620 nm, an optical‐absorption edge of λ=690–790 nm, and EHOMO and ELUMO values of <1.14 and ?0.56 to ?0.76 V, respectively. 相似文献
74.
Rapid Synthesis of Thiophene‐Based,Organic Dyes for Dye‐Sensitized Solar Cells (DSSCs) by a One‐Pot,Four‐Component Coupling Approach 下载免费PDF全文
Keisuke Matsumura Soichi Yoshizaki Dr. Masato. M. Maitani Prof. Yuji Wada Dr. Yuhei Ogomi Prof. Shuzi Hayase Dr. Tatsuo Kaiho Dr. Shinichiro Fuse Dr. Hiroshi Tanaka Prof. Takashi Takahashi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(27):9742-9747
This one‐pot, four‐component coupling approach (Suzuki–Miyaura coupling/C?H direct arylation/Knoevenagel condensation) was developed for the rapid synthesis of thiophene‐based organic dyes for dye‐sensitized solar cells (DSSCs). Seven thiophene‐based, organic dyes of various donor structures with/without the use of a 3,4‐ethylenedioxythiophene (EDOT) moiety were successfully synthesized in good yields based on a readily available thiophene boronic acid pinacol ester scaffold (one‐pot, 3‐step, 35–61 %). Evaluation of the photovoltaic properties of the solar cells that were prepared using the synthesized dyes revealed that the introduction of an EDOT structure beside a cyanoacrylic acid moiety improved the short‐circuit current (Jsc) while decreasing the fill factor (FF). The donor structure significantly influenced the open‐circuit voltage (Voc), the FF, and the power conversion efficiency (PCE). The use of a n‐hexyloxyphenyl amine donor, and our originally developed, rigid, and nonplanar donor, both promoted good cell performance (η=5.2–5.6 %). 相似文献
75.
Rainwater,soil water,and soil nitrate effects on oxygen isotope ratios of nitrous oxide produced in a green tea (Camellia sinensis) field in Japan 下载免费PDF全文
76.
The PdII-catalyzed tandem cyclization of chiral allylic alcohols possessing an internal epoxide and a terminal alcohol provided a contiguous THF–THP and THF–THP ring units stereospecifically. The cyclizations take place via a 5-exo-tet-5-exo-trig mode, however, the cyclization of methyl substituted epoxy diols proceeded via 6-endo-tet-6-exo-trig fashion in a part to construct the oxygen-fused THP–THP ring. The different reaction rates of precursors, which are different stereochemistry at allylic alcohol have been elucidated. 相似文献
77.
Nishizawa K Kurahashi N Sekiguchi K Mizuno T Ogi Y Horio T Oura M Kosugi N Suzuki T 《Physical chemistry chemical physics : PCCP》2011,13(2):413-417
High-resolution soft X-ray photoelectron spectra of liquid water (H(2)O and D(2)O) were measured using a liquid beam photoelectron spectrometer. The 1a(1) (O1s) band and the lowest valence 1b(1) band had single peaks, which is not consistent with the split 1b(1)→ 1a(1) of the X-ray emission band of liquid water if the splitting is assumed to originate from level shifts in two different hydrogen bonding structures. The second valence 3a(1) band of liquid water exhibited a flat top implying that two bands exist underneath a broad feature, which is similar to the case of the 3a(1) band of amorphous ice. The energy splitting between the two 3a(1) bands is estimated to be 1.38 eV (H(2)O) and 1.39 eV (D(2)O). Ab initio calculations suggest that the large splitting of the 3a(1) band is characteristic of water molecules that function as both proton donor and acceptor. The overall result is consistent with the conventional model of a tetrahedral hydrogen-bonding network in liquid water. 相似文献
78.
Ema T Ura N Eguchi K Ise Y Sakai T 《Chemical communications (Cambridge, England)》2011,47(21):6090-6092
Chiral diporphyrin receptor 1, which has a macrocyclic cavity to sandwich aromatic guest molecules via double π-π stacking interactions, enabled the naked-eye detection of an aromatic explosive as well as chiral discrimination in NMR. 相似文献
79.
Jukiya Sakamoto Yuhei Umeda Kenta Rakumitsu Michinori Sumimoto Hayato Ishikawa 《Angewandte Chemie (International ed. in English)》2020,59(32):13414-13422
A collective synthesis of glycosylated monoterpenoid indole alkaloids is reported. A highly diastereoselective Pictet–Spengler reaction with α‐cyanotryptamine and secologanin tetraacetate as substrates, followed by a reductive decyanation reaction, was developed for the synthesis of (?)‐strictosidine, which is an important intermediate in biosynthesis. This two‐step chemical method was established as an alternative to the biosynthetically employed strictosidine synthase. Furthermore, after carrying out chemical and computational studies, a transition state for induction of diastereoselectivity in our newly discovered Pictet–Spengler reaction is proposed. Having achieved the first enantioselective total synthesis of (?)‐strictosidine in just 10 steps, subsequent bioinspired transformations resulted in the concise total syntheses of (?)‐strictosamide, (?)‐neonaucleoside A, (?)‐cymoside, and (?)‐3α‐dihydrocadambine. 相似文献
80.
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