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991.
In this paper, n-Zinc oxide/p-copper oxide heterojunctions were fabricated by RF-sputtering on indium tin oxide-covered glass substrates. The structural and optical properties of the copper oxide and zinc oxide films were analyzed by X-ray diffraction, Fourier transform infrared, scanning electronic microscopy and ultraviolet-visible spectroscopy. The electrical junction properties were investigated by current–voltage (I–V) characteristics. Additionally, both capacitance (C) and conductance (G) versus frequency (f) measurements were realized at room temperature. The junctions showed a rectifying behavior, and C and G varied with both voltage and frequency. 相似文献
992.
We prove the existence of canonical scrolls; that is, scrolls playing the role of canonical curves. First of all, they provide the geometrical version of Riemann Roch Theorem: any special scroll is the projection of a canonical scroll and they allow to understand the classification of special scrolls in PN. Canonical scrolls correspond to the projective model of canonical geometrically ruled surfaces over a smooth curve. We also prove that the generic canonical scroll is projectively normal except in the hyperelliptic case and for very particular cases in the nonhyperelliptic situation. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
993.
N.D McCavishR.A Bennett 《Surface science》2003,546(1):47-56
We have employed low energy electron diffraction (LEED) and X-ray photoelectron spectroscopy to follow the epitaxial growth of thin films of TiO2 on W(1 0 0). The films were grown both by metal vapour deposition of titanium onto the substrate in UHV with subsequent annealing in a low partial pressure of oxygen, and by metal vapour deposition in a low partial pressure of oxygen. LEED patterns showed the characteristic patterns of (1 1 0) oriented rutile. A systematic spot splitting was observed and attributed to a stepped surface. The calculated step height was found to be in good agreement with that expected for rutile TiO2(1 1 0), 3.3 Å. Titanium core level shifts were used to identify oxidation states as a function of film thickness allowing the interpretation in terms of a slightly sub-stoichiometric interface layer in contact with the substrate. In combination with the LEED patterns, the film structure is therefore determined to be (1 1 0) oriented rutile with a comparable level of stoichiometry to UHV prepared bulk crystals. The ordered step structure indicates considerable structural complexity of the surface. 相似文献
994.
Keigo Suzuki Masashi Inoguchi Keisuke Kageyama Hiroshi Takagi Yukio Sakabe 《Journal of nanoparticle research》2009,11(6):1349-1360
In this study, pulsed laser ablation, online annealing, and following size classification using a differential mobility analyzer
(DMA) were employed to fabricate quantum dots (QDs) of zinc oxide (ZnO). The irregularly shaped ZnO particles were obtained
at annealing temperature less than 873 K, which gradually transformed into spherical QDs with increasing the annealing temperature.
Finally, ZnO QDs with narrow size distribution having spherical shapes were successfully obtained at temperatures above 1173 K
under the DMA classification at a nominal size of 10 nm. TEM observation demonstrated that the ZnO QDs obtained by this process
were well-crystallized single crystallites with a wurtzite structure. Further, ZnO QDs with average sizes in the range of
4.8–8.1 nm were successfully fabricated by reducing the specified sizes of DMA. These features of the fabricated ZnO QDs are
favorable for investigation of intrinsic quantum size effect in ZnO. 相似文献
995.
Shaun D. Gittard John R. Perfect Wei Wei Roger J. Narayan 《Applied Surface Science》2009,255(11):5806-5811
The electronic and chemical properties of semiconductor materials may be useful in preventing growth of microorganisms. In this article, in vitro methods for assessing microbial growth on semiconductor materials will be presented. The structural and biological properties of silicon wafers coated with zinc oxide thin films were evaluated using atomic force microscopy, X-ray photoelectron spectroscopy, and MTT viability assay. The antimicrobial properties of zinc oxide thin films were established using disk diffusion and CDC Biofilm Reactor studies. Our results suggest that zinc oxide and other semiconductor materials may play a leading role in providing antimicrobial functionality to the next-generation medical devices. 相似文献
996.
Uroš Maver Darko Makovec Janko Jamnik 《Journal of magnetism and magnetic materials》2009,321(19):3187-3192
The aim of this study was to attach a model drug (naproxen) onto superparamagnetic iron oxide nanoparticles (SPION). First, SPION were coated with thin layer of silica that contained micropores. We demonstrated that such surface functionalization could be optimized by the use of citric acid which prevented SPION agglomeration during the procedure. HRTEM investigation showed a uniform 1-2-nm-thick silica coating around SPION. This coating did not affect significantly the magnetic properties of the SPION. Into the coated SPION we successfully incorporated about 30 wt% of naproxen. The latter was readily released after immersion into a testing solution. The composites could be interesting for potential use in diagnostics. 相似文献
997.
By the reaction of KCN with Cp2TiCl2 (Cp = η5-C5H5) in boiling methanol, bis(cyclopentadienyl)-methoxytitanium(IV) cyanide, Cp2Ti(OCH3)CN, is formed which in air is converted into the dinuclear oxygen-bridged derivative (Cp2TiCN)2O. By the same procedure, the bis(methylcyclopentadienyl) analogue [MeCp2TiCN]2O has been obtained. An X-ray diffraction study of (Cp2TiCN)2O has shown that the CN group acts as a unidentate ligand with a Ti? C bond length of 2.158 Å and a Ti? C? N bond angle of 177.7°, very close to linearity. The Ti? O bond distance, 1.836 Å, and the bond angle at the bridging O atom, 174.1°, are normal. The ligands are arranged in a nearly tetrahedral way around the Ti atoms. The structural results are compared to those for similar dinuclear titanium complexes. 相似文献
998.
Dr. Thomas L. Gianetti Dr. Samuel P. Annen Dr. Gustavo Santiso‐Quinones Prof. Dr. Markus Reiher Prof. Dr. Matthias Driess Prof. Dr. Hansjörg Grützmacher 《Angewandte Chemie (International ed. in English)》2016,55(5):1854-1858
The oxidation of alcohols with N2O as the hydrogen acceptor was achieved with low catalyst loadings of a rhodium complex that features a cooperative bis(olefin)amido ligand under mild conditions. Two different methods enable the formation of either the corresponding carboxylic acid or the ester. N2 and water are the only by‐products. Mechanistic studies supported by DFT calculations suggest that the oxygen atom of N2O is transferred to the metal center by insertion into the Rh?H bond of a rhodium amino hydride species, generating a rhodium hydroxy complex as a key intermediate. 相似文献
999.
Phase behavior and Li+ Ion conductivity of styrene‐ethylene oxide multiblock copolymer electrolytes 下载免费PDF全文
Solid polymer electrolytes are attractive materials for use as battery separators. Here, a molecular weight series of polystyrene–polyethylene oxide (PEO) multiblock copolymers was synthesized by the thiol–norbornene click reaction. The subsequent materials were characterized both neat and with a lithium bis‐(trifluoromethane)sulfonimide salt loading [(Li)/(EO)] of 0.1. In general, neat samples demonstrated crystallinity scaling with PEO content. Lithium ion‐containing samples had broad scattering peaks, half of which displayed disordered scattering, even at the lowest block molecular weights (polystyrene = 1 kg/mol, PEO = 1 kg/mol). Fitting of disordered scattering data, using the random phase approximation, yielded χRPA and Rg values that were compared with recent predictive work by Balsara and coworkers. The predictions were accurate near the volume fraction fPEO = 0.5 but deviated symmetrically with volume fraction asymmetry. Samples were also analyzed by electrochemical impedance spectroscopy for their potential to conduct lithium ions. Samples with fPEO ≥ 0.5 demonstrated robust conductivity, whereas samples below this volume fraction conducted very poorly, with one exception (fPEO = 0.24). This work expanded upon our recently reported approach to multiblock copolymer synthesis, demonstrating the improved access of materials to further our fundamental understanding of multiblock copolymers. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
1000.
Hongyuan Wang Toshinari Ugomori Yong Wang Kazuhiro Tanaka Hidetoshi Kita Ken‐Ichi Okamoto Yasunori Suma 《Journal of Polymer Science.Polymer Physics》2000,38(13):1800-1811
Poly(ethylene oxide imide) segmented copolymer (PEO‐PI) membranes were crosslinked by the chemical reaction between ethylene glycol diglycidyl ether and benzylalcohol groups of diamine moieties in polyimide segments at high temperatures. Sorption and diffusion of penetrants took place in poly(ethylene oxide) segment microdomains. Sorption and desorption behavior of pure vapors such as benzene (Bz), cyclohexane (Cx) and n‐hexane (Hx) was classified as the Fickian diffusion. Sorption isotherms of binary liquid mixtures could be represented by the Flory–Rehner model, but the model overpredicted the sorption amounts of Cx and Hx, leading to small predictions of sorption selectivity αS for Bz/Cx and Bz/Hx systems. UNIFAC‐FV model fairly well predicted the sorption amounts of aromatic hydrocarbons, but significantly overestimated those of nonaromatic ones, leading to too small predictions of αS. Pervaporation (PV) behavior of PEO‐PI membranes was governed by sorption behavior followed by membrane swelling. Diffusion coefficient weakly depended on the minimum cross section of a penetrant. The diffusivity selectivity αD hardly depended on the feed composition and was about 1.4 and 0.75 for Bz/Cx and Bz/Hx, respectively. PV selectivity αPV was larger for Bz/Hx than for Bz/Cx because of larger αS. PEO‐PI membranes displayed high specific permeation flux Ql and reasonably high αPV for aromatic/nonaromatic hydrocarbons; for example, Ql = 60 Kg μm/(m2 h) and αPV = 8 for a feed mixture containing Bz, Tol, Hx, n‐Ot and i‐Ot of 20 wt % at 353 K. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1800–1811, 2000 相似文献