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991.
Katsukiyo Miura Takahiro Nakagawa Akira Hosomi 《Journal of the American Chemical Society》2002,124(4):536-537
In the presence of CaCl2, dimethylsilyl (DMS) enolates smoothly reacted with aldehydes under mild conditions to give aldol adducts in good to high yields. The catalytic activities of various metal and tetrabutylammonium salts have revealed that CaCl2 works as a Lewis base catalyst to activate DMS enolates. The CaCl2-promoted reaction proceeded even in the presence of water or in pure water. This catalytic system was applicable to the aldol reaction with aqueous aldehydes such as formalin. 相似文献
992.
Yoshiko Miura Natsuko Wada Yoshihiro Nishida Hiroshi Mori Kazukiyo Kobayashi 《Journal of polymer science. Part A, Polymer chemistry》2004,42(18):4598-4606
Here we report the chemoenzymatic synthesis and recognition function of glycoconjugate polymers carrying nonreducing disaccharides [α-D -glucopyranosyl-(1-1)-α-D -glucopyranoside (trehalose) and α-D -galactopyranosyl-(1-1)-α-D -glucopyranoside (Gal-type trehalose)]. The lipase-catalyzed esterification of the disaccharides with divinyl sebacate is completely selective at the primary Glc 6-OH position of trehalose and at the Gal 6-OH position of Gal-type trehalose. The resultant vinyl esters can be polymerized to yield glycoconjugate polymers with poly(vinyl alcohol) backbones. The interactions of the glycoconjugate polymers with lectins (concanavalin A and Bandeiraera simplicifolia) are amplified because of the glycocluster effect. The polymer carrying pendant α-D -galactopyranosyl-(1-1)-α-D -glucopyranoside shows inhibition activity against Shiga toxin-1 based on a stereochemical structure similar to that of globosyl Gb2 disaccharide. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4598–4606, 2004 相似文献
993.
S. Yao Y. Shimizu N. Miura N. Yamazoe 《Applied Physics A: Materials Science & Processing》1993,57(1):25-29
A solid electrolyte CO2 sensor using a sodium ionic conductor and a lithium carbonate-based auxiliary phase was investigated. The sensor responded excellently to CO2 in the temperature range of 350–600° C, without being affected by coexistent water vapor. The EMF responses to varying partial pressures of CO2 (P
CO
2) followed a 2-electron reaction of CO2 under fixed P
O
2. Under fixed P
CO
2 (2×10–3 atm), the EMF was found to be almost independent of P
O
2 at temperatures above 450° C, while it depended on P
O
2 following a 2-electron reaction of O2 at 305° C and below. Two alternative sensing electrode reactions were proposed to take place depending on the working temperature. 相似文献
994.
Shibo Xu Kazutaka Takamatsu Prof. Dr. Koji Hirano Prof. Dr. Masahiro Miura 《Angewandte Chemie (International ed. in English)》2018,57(36):11797-11801
A Ni(OAc)2‐catalyzed C?H coupling of 8‐aminoquinoline‐derived benzamides with epoxides has been developed. The reaction proceeds with concomitant removal of the 8‐aminoquinoline auxiliary to form the corresponding 3,4‐dihydroisocoumarins directly. Additionally, the nickel catalysis is stereospecific, and the cis‐ and trans‐epoxides are converted into the corresponding cis‐ and trans‐dihydroisocoumarins with retention of configuration, which is complementary to previously reported palladium catalysis. Moreover, while still preliminary, the C ?H functionalization is also achieved in the presence of modified NiCl2 catalysts. 相似文献
995.
有关用于各种氧化反应中Au-Ag双金属催化剂存在显著协同效应的来源有两种观点:(1) AgOx块与体相Au表面的接触界面起重要作用,体相Au的表面是催化活性位;(2) Au-Ag双金属催化剂中形成的Au-Ag合金中电荷从Ag转移到Au上,可能对催化剂活性起作用。因此,确定Au表面上Ag是以氧化物还是以金属合金形式存在可能是深度理解该协同效应的关键。
为了检测和验证催化剂活性的增加是由于Ag2O与Au纳米粒子的紧密接触,在密闭循环反应体系中比较研究了Au/Ag2O和Ag2O催化剂上CO氧化反应。将CO/O2摩尔比为2的混合气通入到这二个催化剂上来跟踪压力降低的速率。因而检测了气体的消耗量和CO2的生成量。结果发现,在稳态下Au/Ag2O和Ag2O催化剂的压力降低的速率不存在差别。这两个催化剂上压力的降低是由于Ag2O中表面晶格氧被混合气中CO的还原所致。 Au/Ag2O催化剂上得到的结果与以前研究的具有氧化表面的Ag掺杂的Au粉末(Ag/Au-b)上的一致,也表明AgOx块与体相Au表面界面周边不大可能是CO氧化反应催化活性位。基于具有稳态表面的Ag/Au-b样品上的研究结果,我们认为AgOx物种被还原为0价态Ag而形成的Ag-Au合金很可能是催化活性位。 相似文献
为了检测和验证催化剂活性的增加是由于Ag2O与Au纳米粒子的紧密接触,在密闭循环反应体系中比较研究了Au/Ag2O和Ag2O催化剂上CO氧化反应。将CO/O2摩尔比为2的混合气通入到这二个催化剂上来跟踪压力降低的速率。因而检测了气体的消耗量和CO2的生成量。结果发现,在稳态下Au/Ag2O和Ag2O催化剂的压力降低的速率不存在差别。这两个催化剂上压力的降低是由于Ag2O中表面晶格氧被混合气中CO的还原所致。 Au/Ag2O催化剂上得到的结果与以前研究的具有氧化表面的Ag掺杂的Au粉末(Ag/Au-b)上的一致,也表明AgOx块与体相Au表面界面周边不大可能是CO氧化反应催化活性位。基于具有稳态表面的Ag/Au-b样品上的研究结果,我们认为AgOx物种被还原为0价态Ag而形成的Ag-Au合金很可能是催化活性位。 相似文献
996.
997.
Nitrogen‐Rich Manganese Oxynitrides with Enhanced Catalytic Activity in the Oxygen Reduction Reaction 下载免费PDF全文
Dr. Akira Miura Dr. Carolina Rosero‐Navarro Dr. Yuji Masubuchi Dr. Mikio Higuchi Prof. Dr. Shinichi Kikkawa Prof. Dr. Kiyoharu Tadanaga 《Angewandte Chemie (International ed. in English)》2016,55(28):7963-7967
The catalytic activity of manganese oxynitrides in the oxygen reduction reaction (ORR) was investigated in alkaline solutions to clarify the effect of the incorporated nitrogen atoms on the ORR activity. These oxynitrides, with rock‐salt‐like structures with different nitrogen contents, were synthesized by reacting MnO, Mn2O3, or MnO2 with molten NaNH2 at 240–280 °C. The anion contents and the Mn valence states were determined by combustion analysis, powder X‐ray diffraction, and X‐ray absorption near‐edge structure analysis. An increase in the nitrogen content of rock‐salt‐based manganese oxynitrides increases the valence of the manganese ions and reinforces the catalytic activity for the ORR in 1 m KOH solution. Nearly single‐electron occupancy of the antibonding eg states and highly covalent Mn?N bonding thus enhance the ORR activity of nitrogen‐rich manganese oxynitrides. 相似文献
998.
Keiichi Irifune Dr. Ken Yamazaki Dr. Takayuki Nakamuro Prof. Dr. Masahiro Murakami Prof. Dr. Tomoya Miura 《Angewandte Chemie (International ed. in English)》2023,62(33):e202307826
A ligand-controlled regiodivergence in Ni-catalyzed rearrangement of vinylcyclopropanes to 1,4- or 1,5-disubstituted cyclopentenes is reported. The 1,4- or 1,5-disubstituted cyclopentene is selectively obtained depending on the choice of ligands. Detailed kinetic studies and density functional theory calculations on the catalytic cycle revealed that the product selectivity is determined at the reductive elimination step from the six-membered η1-allyl intermediate. 相似文献
999.
Junko Konishi Koji Fujita Kazuki Nakanishi Shotaro Nishitsuji Mikihito Takenaka Kiyotaka Miura Kazuyuki Hirao 《Journal of Sol-Gel Science and Technology》2008,46(1):63-69
Titania (TiO2) monoliths with well-defined bicontinuous macropores and gel skeletons were prepared through the alkoxy-derived sol–gel process
accompanied by spinodal decomposition, and the structural evolution during evaporation drying and heat treatment was probed
by a combination of ultra-small-angle X-ray scattering and small-angle X-ray scattering. X-ray scattering profiles of wet
and dried gels revealed that microporous structures related to the existence of primary particles are present in the gel skeletons
at the wet stage and are preserved during drying. Additionally, it is found that the primary particles swollen in the wet
condition are dried to compact aggregates to produce the smooth surface of gel skeletons. Upon heating at 400 °C, the particle–particle
correlation associated with regularity of mesostructures is enhanced. From nitrogen adsorption–desorption measurements, the
average pore size is less than 1 nm in the dried gel and increases to 3.1 nm by the heat treatment. Homogeneous growth of
primary particles due to interparticle-polycondensation reaction is responsible for the increased size and uniform distribution
of mesopores in the heat-treated gel. 相似文献
1000.
Gobi KV Matsumoto K Toko K Ikezaki H Miura N 《Analytical and bioanalytical chemistry》2007,387(8):2727-2735
This paper describes the fabrication and sensing characteristics of a self-assembled monolayer (SAM)-based surface plasmon
resonance (SPR) immunosensor for detection of benzaldehyde (BZ). The functional sensing surface was fabricated by the immobilization
of a benzaldehyde–ovalbumin conjugate (BZ–OVA) on Au-thiolate SAMs containing carboxyl end groups. Covalent binding of BZ–OVA
on SAM was found to be dependent on the composition of the base SAM, and it is improved very much with the use of a mixed
monolayer strategy. Based on SPR angle measurements, the functional sensor surface is established as a compact monolayer of
BZ–OVA bound on the mixed SAM. The BZ–OVA-bound sensor surface undergoes immunoaffinity binding with anti-benzaldehyde antibody
(BZ-Ab) selectively. An indirect inhibition immunoassay principle has been applied, in which analyte benzaldehyde solution
was incubated with an optimal concentration of BZ-Ab for 5 min and injected over the sensor chip. Analyte benzaldehyde undergoes
immunoreaction with BZ-Ab and makes it inactive for binding to BZ–OVA on the sensor chip. As a result, the SPR angle response
decreases with an increase in the concentration of benzaldehyde. The fabricated immunosensor demonstrates a low detection
limit (LDL) of 50 ppt (pg mL−1) with a response time of 5 min. Antibodies bound to the sensor chip during an immunoassay could be detached by a brief exposure
to acidic pepsin. With this surface regeneration, reusability of the same sensor chip for as many as 30 determination cycles
has been established. Sensitivity has been enhanced further with the application of an additional single-step multi-sandwich
immunoassay step, in which the BZ-Ab bound to the sensor chip was treated with a mixture of biotin-labeled secondary antibody,
streptavidin and biotin–bovine serum albumin (Bio–BSA) conjugate. With this approach, the SPR sensor signal increased by ca.
12 times and the low detection limit improved to 5 ppt with a total response time of no more than ca. 10 min.
Figure A single-step multi-sandwich immunoassay step increases SPR sensor signal by ca. 12 times affording a low detection limit
for benzaldehyde of 5 ppt 相似文献