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991.
Ni‐CeO2 is a highly efficient, stable and non‐expensive catalyst for methane dry reforming at relative low temperatures (700 K). The active phase of the catalyst consists of small nanoparticles of nickel dispersed on partially reduced ceria. Experiments of ambient pressure XPS indicate that methane dissociates on Ni/CeO2 at temperatures as low as 300 K, generating CHx and COx species on the surface of the catalyst. Strong metal–support interactions activate Ni for the dissociation of methane. The results of density‐functional calculations show a drop in the effective barrier for methane activation from 0.9 eV on Ni(111) to only 0.15 eV on Ni/CeO2?x(111). At 700 K, under methane dry reforming conditions, no signals for adsorbed CHx or C species are detected in the C 1s XPS region. The reforming of methane proceeds in a clean and efficient way.  相似文献   
992.
Metal‐nanoparticle‐catalyzed cutting is a promising way to produce graphene nanostructures with smooth and well‐aligned edges. Using a multiscale simulation approach, we unambiguously identified a “Pac‐Man” cutting mechanism, characterized by the metal nanoparticle “biting off” edge carbon atoms through a synergetic effect of multiple metal atoms. By comparing the reaction rates at different types of edge sites, we found that etching of an entire edge carbon row could be triggered by a single zigzag‐site etching event, which explains the puzzling linear dependence of the overall carbon‐atom etching rate on the nanoparticle surface area observed experimentally. With incorporation of the nanoparticle size effect, the mechanisms revealed herein open a new avenue to improve controllability in graphene cutting.  相似文献   
993.
Miniaturized liquid–liquid interfacial reactors offer enhanced surface area and rapid confinement of compounds of opposite solubility, yet they are unable to provide in situ reaction monitoring at a molecular level at the interface. A picoreactor operative at the liquid–liquid interface is described, comprising plasmonic colloidosomes containing Ag octahedra strategically assembled at the water‐in‐decane emulsion interface. The plasmonic colloidosomes isolate ultrasmall amounts of solutions (<200 pL), allowing parallel monitoring of multiple reactions simultaneously. Using the surface‐enhanced Raman spectroscopy (SERS) technique, in situ monitoring of the interfacial protonation of dimethyl yellow (p‐dimethylaminoazobenzene (DY)) is performed, revealing an apparent rate constant of 0.09 min?1 for the first‐order reaction. The presence of isomeric products with similar physical properties is resolved, which would otherwise be indiscernible by other analytical methods.  相似文献   
994.
Tuning the activity of radicals is crucial for radical reactions and radical‐based materials. Herein, we report a supramolecular strategy to accelerate the Fenton reaction through the construction of supramolecularly activated radical cations. As a proof of the concept, cucurbit[7]uril (CB[7]) was introduced, through host–guest interactions, onto each side of a derivative of 1,4‐diketopyrrolo[3,4‐c]pyrrole (DPP), a model dye for Fenton oxidation. The DPP radical cation, the key intermediate in the oxidation process, was activated by the electrostatically negative carbonyl groups of CB[7]. The activation induced a drastic decrease in the apparent activation energy and greatly increased the reaction rate. This facile supramolecular strategy is a promising method for promoting radical reactions. It may also open up a new route for the catalytic oxidation of organic pollutants for water purification and widen the realm of supramolecular catalysis.  相似文献   
995.
Solvation dynamics in alcohols confined in silica nanochannels was examined by time-resolved fluorescence spectroscopy using coumarin 153 (C153) as a fluorescent probe. Surfactant-templated mesoporous silica was fabricated inside the pores of an anodic alumina membrane. The surfactant was removed by calcination to give mesoporous silica (Cal-NAM) containing one-dimensional (1D) silica nanochannels (diameter, 3.1 nm) whose inner surface was covered with silanol groups. By treating Cal-NAM with trimethylchlorosilane, trimethylsilyl (TMS) groups were formed on the inner surface of the silica nanochannels (TMS-NAM). Fluorescence dynamic Stokes shifts of C153 were measured in alcohols (ethanol, butanol, hexanol, and decanol) confined in the silica nanochannels of Cal- and TMS-NAMs, and the time-dependent fluorescence decay profiles could be best fitted by a biexponential function. The estimated solvent relaxation times were much larger than those observed in bulk alcohols for both Cal- and TMS-NAMs when ethanol or butanol was used as a solvent, indicating that the mobility of these alcohol molecules was restricted within the silica nanochannels. However, hexanol or decanol in Cal- and TMS-NAMs did not cause a remarkable increase in the solvent relaxation time in contrast to ethanol or butanol. Therefore, it was concluded that a relatively rigid assembly of alcohols (an alcohol chain) was formed within the silica nanochannels by hydrogen bonding interaction and van der Waals force between the surface functional groups of the silica nanochannels and alcohol molecules and by the successive interaction between alcohol molecules when alcohol with a short alkyl chain (ethanol or butanol) was used as a solvent.  相似文献   
996.
Solvothermal reaction of [MnCl2(terpy)] with elemental As and Se at a 1:1:2 molar ratio in H2O/trien (10:1) at 150 °C affords the linear trimanganese(II) complex [{Mn(terpy)}3(μ‐AsSe4)2] ( 1 ). The tridentate [AsSe2(Se2)]3? anions of 1 chelate the terminal {Mn(terpy)}2+ fragments and bridge these through their remaining Se atom to the central {Mn(terpy)}2+ moiety. Weak interactions of Mn1···Se and Mn3···Se bonds with length 2.914(7) and 3.000(7) Å link the molecules of 1 into infinite chains. Treatment of [MnCl2(cyclam)]Cl with As and Se at a 1:1:2 molar ratio in superheated H2O/CH3OH (1:1) at 150 °C yields the dinuclear complex [{Mn(cyclam)}2 (μ‐As2Se6)] ( 2 ), whose novel [(AsSe2)2(μ‐Se2)]4? ligands bridge the MnII atoms in a μ‐1κ2Se1, Se2: 2κ2Se5,Se6 manner.  相似文献   
997.
Two novel coordination polymers, [Cd(BIM)Cl2]n ( 1 ) and [Pb(BIM)Cl2]n ( 2 ) [wherein BIM = bis(imidazol‐1‐yl)methane], were synthesized by the reactions of the BIM ligand with CdCl2 and PbCl2, respectively. They were characterized by elemental analyses, IR, TGA and X‐ray single‐crystal diffraction techniques. Single‐crystal X‐ray structure analyses showed there is a pseudooctahedral arrangement around the cadmium atom in the complex 1 . It has a three‐dimensional network which contains one‐dimensional inorganic‐organic hybrid chains and μ2‐bridging chloride ligands. A rare pentacoordinate square‐pyramidal arrangement was adopted for the lead(II) atom in the complex 2 , which has an unusual two‐dimensional layer structure of macrometallacycles crosslinked with the bridging Pb2Cl2 units. The metal atoms in both complexes were coordinated with two BIM ligands in cis arrangement and bridged by μ2‐bridging chloride ligands.  相似文献   
998.
The reaction of 2,2′‐Bis(2N‐(1,1′,3,3′‐tetramethyl‐guanidino))diphenylene‐amine (TMG2PA) ( 1 ) with CuI in MeCN results in the formation of [CuII(TMG2PAamid)I] ( 2 ) indicatingthat CuI is the target of an oxidative attack of the N‐H proton of the ligand which itself is converted to molecular hydrogen. In contrast, if [Cu(MeCN)4][PF6] is used as the CuI source, [CuI2(TMGbenz)2][PF6]2 ( 3 ) is obtained instead. The use of the non‐coordinating counterion [PF6] apparently prevents CuI from oxidation but induces itself a cyclisation reaction within the ligand which results in the formation of a benzimidazole‐guanidine ligand.  相似文献   
999.
Enders' N‐heterocyclic carbene (NHC) dehydrogenates ammonia–borane with a relatively low barrier, producing NH2BH2 and NHC–(H)2. The nickel NHC catalyst present in the reaction media can activate the NHC–(H)2 produced to regenerate the free NHC and release H2. The release of free NHC enables further dehydrogenation of ammonia–borane.

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1000.
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