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排序方式: 共有70条查询结果,搜索用时 15 毫秒
1.
Capon RJ Skene C Liu EH Lacey E Gill JH Heiland K Friedel T 《Natural product research》2004,18(4):305-309
Bioassay directed fractionation of a Raspailia (Raspailia) sp. (Order Poecilosclerida; Family Raspailiidae) collected during scientific trawling operations off the Northern Rottnest Shelf yielded as nematocidal agents the known metabolites, phorboxazoles A (1) and B (2). Further examination revealed the new natural product but known synthetic compound, esmodil (3). The structure for 3 was confirmed by spectroscopic analysis and total synthesis. 相似文献
2.
Afshin Nabiyan Johannes Bernhard Max Dr. Christof Neumann Magdalena Heiland Prof. Dr. Andrey Turchanin Prof. Dr. Carsten Streb Prof. Dr. Felix Helmut Schacher 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(68):16924-16929
An effective strategy to enhance the performance of inorganic semiconductors is moving towards organic-inorganic hybrid materials. Here, we report the design of core–shell hybrid materials based on a TiO2 core functionalized with a polyampholytic (poly(dehydroalanine)-graft-(n-propyl phosphonic acid acrylamide) shell (PDha-g-PAA@TiO2). The PDha-g-PAA shell facilitates the efficient immobilization of the photosensitizer Eosin Y (EY) and enables electronic interactions between EY and the TiO2 core. This resulted in high visible-light-driven H2 generation. The enhanced light-driven catalytic activity is attributed to the unique core–shell design with the graft copolymer acting as bridge and facilitating electron and proton transfer, thereby also preventing the degradation of EY. Further catalytic enhancement of PDha-g-PAA@TiO2 was possible by introducing [Mo3S13]2− cluster anions as hydrogen-evolution cocatalyst. This novel design approach is an example for a multi-component system in which reactivity can in future be independently tuned by selection of the desired molecular or polymeric species. 相似文献
3.
The adsorption of CO and O on Ni (111) was studied by low-energy ion scattering (ISS) and low-energy electron diffraction (LEED). For the ordered (√7/2) × (√7/2) R19.1° CO layer ion scattering gives a coverage greater than monolayer, and for the (2 × 2) O layer a coverage of monolayer. The CO is non-dissociatively adsorbed, with the C bound to the Ni. The molecules are oriented parallel to the surface normal. Island formation at lower CO coverages is possible. 相似文献
4.
5.
S. Priggemeyer H. Koschmieder G. N. Van Wyk W. Heiland 《Fresenius' Journal of Analytical Chemistry》1991,341(5-6):343-345
Summary Yttrium iron garnet (YIG) films are made by liquid phase epitaxy (LPE) on a gadolinium gallium garnet (GGG) substrate. The melt contains mainly lead oxide (PbO) and therefore lead can be incorporated into the films. During the annealing process it was found that lead segregates to the surface of the YIG films. The evidence for and the temperature dependence of the segregation process is studied by low energy ion scattering (ISS).
On leave from: Department of Physics, University of the O.F.S., 9300 Bloemfontein, South Africa 相似文献
6.
The Hall effect on polar faces of ZnO has been measured at 80 K. Surface excess electron densities between 107 and 1013 cm?2 have been achieved by photolysis, annealing or hydrogen exposure. The surface electron mobility as a function of carrier density shows a modulated structure. Possible scattering mechanism are discussed. 相似文献
7.
The interaction between crystal and adsorbed dye molecules has been studied under well defined conditions by measurements of field effect and spectrally sensitized photoconductivity. The (101̄0) surfaces of n-type ZnO crystals (band gap 3.3 eV) are cleaned in ultrahigh vacuum. A pretreatment with atomic hydrogen produces an accumulation layer. Merocyanine (polymethine) dye molecules are deposited by sublimation in the same vacuum (coverage (1–2000) × 1014 cm?2. Optical excitation of the dye causes a sensitized photoconductivity in the ZnO crystal close to the surface. The spectra distribution resembles the absorption spectrum of the dye with a maximum at 2.3 eV. An electric field applied perpendicular to the dye covered surface induces charge carriers in the crystal and changes the surface conductivity (field effect). Additional excitation of the dye by light causes a slow relaxation of the field-induced change of surface conductivity. This relaxation is observed for both signs of the field. Furthermore a memory of the dye covered crystals has been found. It can be programmed by field and light, read out via the surface conductivity and quenched by light. A phenomenological model for relaxation and memory is refined by kinetic equations and by considerations about charge transport within the dye layer. The observations can only be explained by a charge transfer between crystal and dye operating in both directions. From these results the following conclusion is drawn for the mechanism of spectrally sensitized photoconductivity of the present system: An electron transfer between dye molecules and crystal represents the decisive step rather than an energy transfer. 相似文献
8.
The desorption of zinc from cleaved polar faces was investigated in UHV. TDS (calibrated by evaporation of metallic Zn), surface conductivity, LEED and AES were used. The initial sticking coefficient is lower on the Zn face than on the O face, 0.2 and 1 respectively. On both faces two states of adsorption occur. The lower state on the Zn face has an activation energy of 35 kcal/mole(1.5 eV). The corresponding energy on the oxygen face is 16 kcal/mole (0.7 eV). The lower peak is connected with an increase in surface conductivity on both faces. On the Zn face this surface conductivity can be attributed to a surface donor 1.3 eV above the conduction band edge. Above one monolayer the formation of islands and an epitactical growing of a zinc lattice were found. 相似文献
9.
10.
Energy distributions of low-energy noble gas ions backscattered from a single-crystal nickel surface
The energy distribution of noble gas ions in the energy range below 1 keV from a single-crystalline surface depends on the composition and the structure of the surface, the mass and energy of the impinging ions and the geometrical conditions (e.g. angle of incidence) of the experiment. In the case of He ions the kinematic binary collision theory can be applied. For Ne ions the scattering process is more complicated, good agreement between a multiple scattering model and the experiment is achieved. Deviations from this general behaviour are observed with heavier ions (Ar+) and at very low energies. The experimental evidence for the different processes is discussed. 相似文献