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排序方式: 共有502条查询结果,搜索用时 156 毫秒
231.
Dr. Yunfeng Bao Dr. Shiwen Du Dr. Kengo Shibata Dr. Xiangyang Guo Yoshinobu Kamakura Prof. Dr. Zhaochi Feng Prof. Dr. Yanqiang Huang Prof. Dr. Osamu Ishitani Prof. Dr. Kazuhiko Maeda Prof. Dr. Fuxiang Zhang 《Angewandte Chemie (International ed. in English)》2023,62(4):e202214273
Developing mixed-anion semiconductors for solar fuel production has inspired extensive interest, but the nitrohalide-based photocatalyst is still in shortage. Here we report a layered nitro-halide β-ZrNBr with a narrow band gap of ca. 2.3 eV and low defect density to exhibit multifunctionalities for photocatalytic water reduction, water oxidation and CO2 reduction under visible-light irradiation. As confirmed by the results of electron paramagnetic resonance (EPR) and density functional theory (DFT) calculations, the formation of anion vacancies in the nitro-halide photocatalyst was inhibited due to its relatively high formation energy. Furthermore, performance of β-ZrNBr can be effectively promoted by a simple exfoliation into nanosheets to shorten the carrier transfer distance as well as to promote charge separation. Our work extends the territory of functional photocatalysts into the nitro-halide, which opens a new avenue for fabricating efficient artificial photosynthesis. 相似文献
232.
Hirose K Shiba Y Ishibashi K Doi Y Tobe Y 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(11):3427-3433
Design, synthesis, and demonstration of a prototype of a shuttling molecular machine with a reversible brake function are reported. It is a photochemically and thermally reactive rotaxane composed of a dianthrylethane-based macrocycle as the ring component and a dumbbell shaped molecular unit with two, secondary ammonium stations separated by a phenylene spacer as the axle component. The rate of shuttling motion was shown to be reduced to less than 1 % (from 340 to <2.5 s(-1)) by reducing the size of the ring component from 30-crown-8 to 24-crown-8 macrocycles upon photoirradiation. The ring component was turned back to 30-crown-8 by thermal ring opening, thus establishing a reversible brake function that works in response to photochemical and thermal stimuli. 相似文献
233.
A rigid C(3v)-symmetrical host molecule, syn-1,3,5-tris(2-hydroxy-5-pentylphenyl)-2,4,6-trimethylbenzene, was readily obtained via Suzuki coupling and thermal atropisomerization. The host molecule effectively associated with various saccharides by multipoint hydrogen bonds, whereas its anti-atropisomer and analogue lacking in methyl groups showed much weaker association with saccharides. Thermodynamic analyses suggested that the difference of the association strength was caused by entropic factors. 相似文献
234.
235.
Hirokazu Hayashi Takashi Kamiyama Yoshio Nakamura Yoshinobu Izumi 《Journal of Non》1992,150(1-3):297-301
Quasielastic neutron scattering measurements have been made for concentrated solutions of LiNO3 in (1,3)-diaminopropane in the liquid and glassy states. The results indicate that a harmonic lattice vibration-like motion of the atoms in solid glasses changes around the glass transition temperature to an intermediate one prior to a translational diffusive motion at higher temperatures. This picture is consistent with the previous results obtaiend from NMR relaxation mearsuremts. 相似文献
236.
237.
Kuniaki Tatsuta Yoshiya Amemiya Yoshinobu Kanemura Mitsuhiro Kinoshita 《Tetrahedron letters》1981,22(40):3997-4000
The total synthesis of tyionolide, a 16-membered-ring aglycone of a macrolide antibiotic, tyiosin, has been accomplished by coupling two segments of C1-C10 and C11-C17 portions, which are stereospecifically derived from D-glucose. 相似文献
238.
McNamee CE Tsujii Y Matsumoto M 《Langmuir : the ACS journal of surfaces and colloids》2005,21(24):11283-11288
Atomic force microscopy was used to characterize an anatase TiO2 surface, prepared by the helical vapor preparation method. The forces between two bare TiO2 surfaces were measured in the presence of water at various pH values. This TiO2 isoelectric point (iep) was characterized by the presence of only a van der Waals attraction and was measured at pH 5.8; this value is similar to that for a rutile TiO2 surface. The adsorption mechanism of a nonionic surfactant molecule to this anatase TiO2 surface was investigated by measuring the forces between two such TiO2 surfaces at their iep pH in the presence of linear dodecanol tetraethoxylate (C12E4), a poly(ethoxylene oxide) n-alkyl ether. C12E4 was seen by the presence of steric forces to adsorb to the uncharged TiO2 surface. For low surfactant concentrations, C12E4 adsorbed with its hydrophobic tail facing the TiO2 substrate, to reduce its entropically unfavorable contacts with water. Additional surfactant adsorption occurred at higher surfactant concentrations by the hydrophobic and hydrophilic interactions between the surfactant tails and heads, respectively, and gave sub-bilayers. A two-step adsorption isotherm was subsequently proposed with four regions: (1) submonolayer, (2) complete monolayer, (3) sub-bilayer, and (4) bilayer. The absence of a long-range repulsive force between the two TiO2 surfaces in the presence of the C12E4 surface aggregates indicated that a C12E4 nonionic surfactant aggregate did not possess charge. 相似文献
239.
240.
Regular helical structures of polysaccharides are most conveniently described by a set of the helix parameters; n for the number of chemical repeating units per turn and h in Å for the rise per unit along the helix axis. A two dimensional mapping of n-h values for possible helix models along with the potential energy surfaces allows one to estimate conformational accessibility of a given posaccharide.1-3 Recently, we have adopted the method to study an acidic heteropolysaccharide4 and a branching glucan.5 These polysaccharides involve two or three sets of backbone glycosidic linkages (Φ-Ψ), each of which varies independently, and, therefore, enormous multidimensional spaces must be explored. Their n-h maps were calculated based on the low energy Φ-Ψ values derived from MM36-8-generated, relaxed-residue potential energy maps9, 10 of the component disaccharides. The present assessment of helix models for the two heteropolymeric glucans is achieved by calculating n-h maps in a similar fashion. These glucans are the two poly(disaccharide)s, poly[(1→3)-α-D-maltotriose] (elsinan) and poly[(1→3)-β-D-cellotriose] (lichenan). In addition to single-stranded helices, three types of mutiple helices; double-parallel, and double-antiparallel, and triple helices have also been examined. 相似文献