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排序方式: 共有4626条查询结果,搜索用时 15 毫秒
1.
Haruki Inoue Dr. Shin-ichi Naya Atsunobu Akita Dr. Hisashi Sugime Prof. Dr. Hiroaki Tada 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(46):e202201653
Gold nanoparticles with different mean sizes were formed on antimony-doped tin oxide nanocrystals by the temperature-varied deposition-precipitation method (Au/ATO NCs). Au/ATO NCs possess strong absorption in the near-infrared region due to Drude excitation in addition to the localized surface plasmon resonance (LSPR) of AuNPs around 530 nm. Au/ATO NCs show thermally activated catalytic activity for the oxidation of cinnamyl alcohol to cinnamaldehyde by hydrogen peroxide. The catalytic activity increases with a decrease in the mean Au particle size (dAu) at 5.3 nm≤dAu≤8.2 nm. Light irradiation (λex >660 nm, ∼0.5 sun) of Au/ATO NCs increases the rate of reaction by more than twice with ∼95 % selectivity. Kinetic analyses indicated that the striking enhancement of the reaction stems from the rise in the temperature near the catalyst surface of ∼30 K due to the photothermal effect of the ATO NCs. 相似文献
2.
Synthesis of Highly Substituted γ‐Butyrolactones by a Gold‐Catalyzed Cascade Reaction of Benzyl Esters 下载免费PDF全文
Maria Camila Blanco Jaimes Alexander Ahrens Daniel Pflästerer Dr. Matthias Rudolph Prof. Dr. A. Stephen K. Hashmi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(1):427-433
Easily accessible benzylic esters of 3‐butynoic acids in a gold‐catalyzed cyclization/rearrangement cascade reaction provided 3‐propargyl γ‐butyrolactones with the alkene and the carbonyl group not being conjugated. Crossover experiments showed that the formation of the new C?C bond is an intermolecular process. Initially propargylic–benzylic esters were used, but alkyl‐substituted benzylic esters worked equally well. In the case of the propargylic–benzylic products, a simple treatment of the products with aluminum oxide initiated a twofold tautomerization to the allenyl‐substituted γ‐butyrolactones with conjugation of the carbonyl group, the olefin, and the allene. The synthetic sequence can be conducted stepwise or as a one‐pot cascade reaction with similar yields. Even in the presence of the gold catalyst the new allene remains intact. 相似文献
3.
Chunhong Wang Qi Cui Zhixin Zhang Prof. Zhu-Jun Yao Dr. Shaozhong Wang Prof. Zhi-Xiang Yu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(42):9821-9826
1,3-Azaprotio transfer of propargylic α-ketocarboxylate oximes, a new type of alkynyl oximes featuring an ester tether, has been explored by taking advantage of gold catalysis. The incorporation of an oxygen atom to the chain of alkynyl oximes led to the formation of two different oxa-cyclic nitrones. It was found that internal alkynyl oximes with an E-configuration deliver five-membered nitrones, whereas terminal alkynyl oximes with an E-configuration afford six-membered nitrones. DFT calculations on four possible pathways supported a stepwise formation of C−N and C−H bonds, in which a 1,3-acyloxy-migration competes with the 1,3-azaprotio-transfer, especially in the case of internal alkynyl oximes. The relative nucleophilic properties of oxygen in the carbonyl group and the nitrogen in the oxime, the electronic effects of alkynes, and the influence of the ring system have been investigated computationally. 相似文献
4.
Probing the Catalytic Activity of Reduced Graphene Oxide Decorated with Au Nanoparticles Triggered by Visible Light 下载免费PDF全文
Dr. Jiale Wang Dr. Fabiane J. Trindade Caroline B. de Aquino Joana C. Pieretti Prof. Dr. Sergio H. Domingues Prof. Dr. Romulo A. Ando Prof. Dr. Pedro H. C. Camargo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(27):9889-9894
Hybrid materials in which reduced graphene oxide (rGO) is decorated with Au nanoparticles (rGO–Au NPs) were obtained by the in situ reduction of GO and AuCl4?(aq) by ascorbic acid. On laser excitation, rGO could be oxidized as a result of the surface plasmon resonance (SPR) excitation in the Au NPs, which generates activated O2 through the transfer of SPR‐excited hot electrons to O2 molecules adsorbed from air. The SPR‐mediated catalytic oxidation of p‐aminothiophenol (PATP) to p,p′‐dimercaptoazobenzene (DMAB) was then employed as a model reaction to probe the effect of rGO as a support for Au NPs on their SPR‐mediated catalytic activities. The increased conversion of PATP to DMAB relative to individual Au NPs indicated that charge‐transfer processes from rGO to Au took place and contributed to improved SPR‐mediated activity. Since the transfer of electrons from Au to adsorbed O2 molecules is the crucial step for PATP oxidation, in addition to the SPR‐excited hot electrons of Au NPs, the transfer of electrons from rGO to Au contributed to increasing the electron density of Au above the Fermi level and thus the Au‐to‐O2 charge‐transfer process. 相似文献
5.
Umie F.M. Haziz Rosenani A. Haque Shun-Ze Zhan Hassan H. Abdallah Mohd R. Razali 《应用有机金属化学》2020,34(10):e5818
The synthesis and characterizations for a series of dinuclear gold (I)-di-NHC complexes, 1–8 through the trans-metalation method of their respective silver (I)-di-NHC complexes, i–viii are reported (where NHC = N-heterocyclic carbene). The successful complexation of a series of unusual non-symmetrical and symmetrical di-NHC ligands, 3,3'-(ethane-1,2-diyl)-1-alkylbenzimidazolium-1'-butylbenzimidazolium (with alkyl = methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, benzyl) with the gold (I) ions are suggested by elemental analysis, Fourier transform-infrared, 1H- and 13C-NMR data. The 13C-NMR spectra of 1–8 show a singlet sharp peak in the range of 190.00–192.00 ppm, indicating the presence of a carbene carbon that bonded to the gold (I) ion. From single crystal X-ray diffraction data, the structure of complex 6 with the formula of [di-NHC-Au (I)]2·2PF6 is obtained [where NHC = 3,3'-(ethane-1,2-diyl)-1-hexylbenzimidazolium-1'-butylbenzimidazolium]. The photophysical study in solid state of 6 displays an intense photoluminescence with a strong emission maxima, λem = 480 nm, upon excitation at 340 nm at room temperature. Interestingly, the emission maximum at 77 K shows a structural character with a strong peak at 410 nm, a medium at 433 nm and a weak at 387 nm, accompanied by a tail band to about 500 nm. 相似文献
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10.
C. Guillermier 《Applied Surface Science》2006,252(19):6644-6647
The yield of CN from glycine rises from one CN per projectile impact to two when the sample is covered with a nominally 1 nm thick layer of silver. These yields were obtained for bombardment with Au4004+ projectile with 136 keV impact energy. A multitude of CN-based clusters, e.g. AgxOy(CN)z are produced concurrently. As a result, a total of three CN-based secondary ions are generated per projectile impact. The exceptionally high yield for CN is of interest for biological SIMS. 相似文献