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101.
Harada T Ikeda S Hashimoto F Sakata T Ikeue K Torimoto T Matsumura M 《Langmuir : the ACS journal of surfaces and colloids》2010,26(22):17720-17725
A core-shell composite consisting of a palladium (Pd) nanoparticle and a hollow carbon shell (Pd@hmC) was employed as a catalyst for aerobic oxidation of various alcohols. The core-shell structure was synthesized by consecutive coatings of Pd nanoparticles with siliceous and carbon layers followed by removal of the intermediate siliceous layer. Structural characterizations using TEM and N(2) adsorption-desorption measurements revealed that Pd@hmC thus-obtained was composed of a Pd nanoparticle core of 3-6 nm in diameter and a hollow carbon shell with well-developed mesopore (ca. 2.5 nm in diameter) and micropore (ca. 0.4-0.8 nm in diameter) systems. When compared to some Pd-supported carbons, Pd@hmC showed a high level of catalytic activity for oxidation of benzyl alcohol into benzaldehyde using atmospheric pressure of O(2) as an oxidant. The Pd@hmC composite also exhibited a high level of catalytic activity for aerobic oxidations of other primary benzylic and allylic alcohols into corresponding aldehydes. The presence of a well-developed pore system in the lateral carbon shell enabled efficient diffusion of both substrates and products to reach the central Pd nanoparticles, leading to such high catalytic activities. This core-shell structure also provided high thermal stability of Pd nanoparticles toward coalescence and/or aggregation due to the physical isolation of each Pd nanoparticle from neighboring particles by the carbon shell: this specific property of Pd@hmC resulted in possible regeneration of catalytic activity for these aerobic oxidations by a high-temperature heat treatment of the sample recovered after catalytic reactions. 相似文献
102.
Kobayashi M Matsuo T Fukunaga T Hashizume D Fueno H Tanaka K Tamao K 《Journal of the American Chemical Society》2010,132(43):15162-15163
π-Conjugated disilenes with 2-naphthyl or 2-fluorenyl groups on the silicon atoms have been synthesized as air-stable emissive red solids using the bulky 1,1,3,3,5,5,7,7-octaethyl-s-hydrindacen-4-yl (Eind) groups. The strong π-π* absorptions and distinct emission at room temperature, both in solution and in the solid state, have been observed due to the substantial contribution of the 3p(π)*(Si-Si)-2p(π)*(carbon π-electron system) conjugation. 相似文献
103.
Evaluation of chemiluminescence reagents for selective detection of reactive oxygen species 总被引:2,自引:0,他引:2
Shinya Yamaguchi Kaname Ohyama Maiko Kohno Akira Takadate Naotaka Kuroda 《Analytica chimica acta》2010,665(1):74-27
In order to evaluate the chemiluminescence (CL) reagents for selective detection of reactive oxygen species (ROS), we comprehensively measured the CL responses of 20 CL reagents (three luminol derivatives, two imidazopyrazinone derivatives, eight lophine derivatives, six acridinium ester derivatives and lucigenin) against six types of ROS (superoxide anion: O2−, hydroxyl radical: OH, hydrogen peroxide: H2O2, hypochlorite anion: ClO−, singlet oxygen: 1O2, and nitric oxide: NO). As a result of the screening, it was found that nine CL reagents selectively detected O2− while one CL reagent selectively detected OH. However, no CL reagent had selectivity on the detection of H2O2, ClO−, 1O2 and NO. Our screening results could help to select the most suitable CL reagent for selective determination of different ROS.As an application study, 4-methoxyphenyl-10-methylacridinium-9-carboxylate (MMAC), one of the acridinium ester derivatives, showed high selectivity on the detection of O2−, and thus was applied to the assay of superoxide dismutase (SOD) activity. The dynamic range and detection limit of the developed CL assay were 0.1-10 and 0.06 U mL−1, respectively. Significant correlation (r = 0.997) was observed between the results by the CL assay using MMAC and the spectrophotometric assay using 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium monosodium salt. 相似文献
104.
Iwashina T Yamaguchi MA Nakayama M Onozaki T Yoshida H Kawanobu S Onoe H Okamura M 《Natural product communications》2010,5(12):1903-1906
Three flavonol glycosides were isolated from the flowers of carnation cultivars 'White Wink' and 'Honey Moon'. They were identified from their UV, MS, 1H and 13C NMR spectra as kaempferol 3-O-neohesperidoside, kaempferol 3-O-sophoroside and kaempferol 3-O-glucosyl-(1 --> 2)-[rhamnosyl-(1 --> 6)-glucoside]. Referring to previous reports, flavonols occurring in carnation flowers are characterized as kaempferol 3-O-glucosides with additional sugars binding at the 2 and/or 6-positions of the glucose. The kaempferol glycoside contents of a nearly pure white flower and some creamy white flower lines were compared. Although the major glycoside was different in each line, the total kaempferol contents of the creamy white lines were from 5.9 to 20.9 times higher than the pure white line. Thus, in carnations, kaempferol glycosides surely contribute to the creamy tone of white flowers. 相似文献
105.
Kobayashi S Waki T Nakanishi I Matsumoto K Anzai K 《Chemical & pharmaceutical bulletin》2010,58(11):1442-1446
New potent antioxidants conjugating the catechol (=pyrocatechol; pyrCat) group to two N-termini of modified double-stranded tyrosine residues were synthesized and showed radical scavenging activity with 2,2-diphenyl-1-picrylhydrazyl radical (DPPH radical, DPPH˙) as a free radical model, second-order rate constants for the DPPH˙ scavenging reaction, and the results from electron spin resonance (ESR) studies. It was found that the tyrosine (Tyr) residue and pyrCat containing new antioxidants developed in the study have about 3-20 times more potent antioxidative activity than Trolox, pyrCat, and L-ascorbic acid (VC). In order to elucidate the relationship between antioxidant activity and the molecular orbital states, and to design potent antioxidants we present an interesting approach using an absolute hardness (η)-absolute electronegativity (χ) diagram based on chemical hardness. It was shown that quantum chemicals were required to develop potent antioxidants. 相似文献
106.
Adachi I Aihara H Dijkstra HB Enomoto R Fujii H Fujii K Fujii T Fujimoto J Fujiwara N Hayashii H Higashi S Iida N Imanishi A Ikeda H Ishii T Itoh R Iwasaki H Iwata S Kajikawa R Kamae T Kato S Kawabata S Kichimi H Kishida T Kobayashi M Kuroda S Kusuki N Maruyama A Maruyama K Masuda H Matsuda T Miyamoto A Morimoto T Nakamura K Nitoh O Noguchi S Ochiai F Okuno H Okusawa T Ohshima T Ozaki H Sato T Sai F Shimonaka J Shimozawa K Shirahashi A Sugahara R Sugiyama A Suzuki S Suwada T Takahashi K 《Physical review letters》1988,60(2):97-100
107.
Masanori Miura Takanori Koike Tsukasa Ishihara Fukushi Hirayama Shuichi Sakamoto Minoru Okada 《合成通讯》2013,43(24):3809-3820
A one‐pot synthetic procedure for 2,2′‐disubstituted biaryls was developed via a Suzuki cross‐coupling reaction of aryl triflates in a biphasic solvent system. The effects of various bases and solvents were investigated. Results showed that the Na2CO3–toluene/H2O combination gave the highest yields. 相似文献
108.
109.
Oligomeric Alkoxysilanes with Cagelike Hybrids as Cores: Designed Precursors of Nanohybrid Materials
Hideki Kuge Yoshiaki Hagiwara Atsushi Shimojima Dr. Kazuyuki Kuroda Prof. 《化学:亚洲杂志》2008,3(3):600-606
Well‐defined alkoxysilane oligomers containing a cagelike carbosiloxane core were synthesized and used as novel building blocks for the formation of siloxane‐based hybrid networks. These oligomers were synthesized from the cagelike trimer derived from bis(triethoxysilyl)methane by silylation with mono‐, di‐, and triethoxychlorosilanes ((EtO)nMe3?nSiCl, n=1, 2, and 3). Hybrid xerogels were prepared by hydrolysis and polycondensation of these oligomers under acidic conditions. The structures of the products varied depending on the number of alkoxy groups (n). When n=2 and 3, microporous xerogels (BET surface areas of 820 and 510 m2 g?1, respectively) were obtained, whereas a nonporous xerogel was obtained when n=1. 29Si NMR spectroscopic analysis suggested that partial rearrangement of the siloxane networks, which accompanied the cleavage of the Si–O–Si linkages, occurred during the polycondensation processes. By using an amphiphilic triblock copolymer surfactant as a structure‐directing agent, hybrid thin films with a 2D hexagonal mesostructure were obtained when n=2 and 3. These results provide important insight into the rational synthesis of molecularly designed hybrid materials by sol–gel chemistry. 相似文献
110.