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71.
Fabrication of mesoporous ZnO nanosheets from precursor templates grown in aqueous solutions 总被引:1,自引:0,他引:1
Keita Kakiuchi Eiji Hosono Toshio Kimura Hiroaki Imai Shinobu Fujihara 《Journal of Sol-Gel Science and Technology》2006,39(1):63-72
Mesoporous ZnO nanosheets were successfully prepared by pyrolytic transformation of zinc carbonate hydroxide hydrate, Zn4CO3(OH)6·H2O. The nanosheets were initially formed as assemblies on glass substrates during chemical bath deposition (CBD) in aqueous
solutions of urea and zinc acetate dihydrate, zinc chloride, zinc nitrate hexahydrate, or zinc sulfate heptahydrate at 80°C.
It was key to induce heterogeneous nucleation of Zn4CO3(OH)6·H2O by promoting a gradual hydrolysis reaction of urea and controlling the degree of supersaturation of zinc hydroxide species.
Morphology of Zn4CO3(OH)6·H2O was largely influenced by the anions present in the CBD solutions. The Zn4CO3(OH)6·H2O nanosheets were transformed into wurtzite ZnO by heating at 300°C in air without losing the microstructural feature. 相似文献
72.
Some of the ascidians belonging to the suborder Phlebobranchia accumulate vanadium ion efficiently from seawater. Clarification of the mechanism of this surprisingly efficient metal-accumulation system is desirable. Two mutually similar vanadium-binding proteins (vanabin1 and vanabin2) have recently been isolated from a vanadium-rich ascidian Ascidia sydneiensis samea. In this study, the vanadium-binding properties of vanabin2 have been investigated by X-band CW EPR and pulsed EPR spectroscopy. CW EPR spectra of samples containing various ratios of VO2+ and vanabin2 invariably exhibited a usual mononuclear-type VO2+ EPR signal with the intensity dependent on the ratio [vanabin]/[V]. EPR titration has shown that vanabin2 can bind up to approximately 23.9 vanadium ions per one molecule, almost all of which ( approximately 84%) are in a mononuclear VO2+ state as estimated by EPR quantitation. Electron spin-echo envelope modulation (ESEEM) spectra of VO-vanabin2 exhibited reasonably intense peaks attributable to amine nitrogen. This is consistent with the fact that vanabin2 is a lysine-rich protein (14 lysines out of 91 amino acids). The present study reveals the uniqueness of vanabin2, which can bind a large number of metal ions in a mononuclear fashion in contrast to the situation for ferritin and metallothionein. 相似文献
73.
Masahiro Tsunooka Shingo Tanaka Makoto Tanaka Hiroaki Egawa Takamasa Nonaka 《Journal of polymer science. Part A, Polymer chemistry》1985,23(9):2495-2505
In the photocrosslinking of poly(2,3-epithiopropyl methacrylate) (PETMA) films the effect of the pendant episulfide group's oxidation on the crosslinking of PETMA was investigated. Thermal crosslinking of PETMA is promoted by peroxides such as benzoyl peroxide and hydrogen peroxide. IR spectrum of the crosslinked PETMA showed that the reaction proceeded through the oxidation of episulfide groups by the peroxides. The anthracene (An) sensitized photocrosslinking of PETMA films also proceeded via the oxidation of episulfide groups by singlet oxygen. It was found that residual tetrahydrofuran (THF) in the films remarkably increased the rate of the photocrosslinking and/or reduced the induction period. From the further investigation concerning casting solvents it was found that residual CS2, CCl4, and CHCl3 in films increased the rate of the photocrosslinking and/or reduced the induction period of the photocrosslinking. The disappearance rate of An in the films was also increased by the presence of residual CS2, CCl4, and CHCl3, differring from the result of THF. These results were explained by a difference in lifetime of singlet oxygen in the films. From the results were explained by a difference in lifetime of singlet oxygen in the films. From the results concerning the effects of hydroperoxides such as THF hydroperoxide and t-butyl hydroperoxide on the photocrosslinking of PETMA films the acceleration effect of the residual THF was deduced to be due to the promotion of singlet oxygen-oxidation of sulfide groups by protic compounds such as THF hydroperoxide and H2O in the THF. 相似文献
74.
Kittaka A Kurihara M Peleg S Suhara Y Takayama H 《Chemical & pharmaceutical bulletin》2003,51(3):357-358
Hereditary vitamin D-resistant rickets (HVDRR) is a genetic disorder caused by mutations in the vitamin D receptor, which lead to resistance to 1alpha,25-dihydroxyvitamin D(3) [1alpha,25(OH)(2)D(3)]. We found that the A ring-modified analogues, 2alpha-(3-hydroxypropyl)- and 2alpha-(3-hydroxypropoxy)-1alpha,25(OH)(2)D(3), (O1C3 and O2C3) can bind better than the natural hormone to the mutant VDR (R274A), which similar to the HVDRR mutant, R274L, had lost the hydrogen bond to the 1alpha-hydroxyl group of 1alpha,25(OH)(2)D(3). 相似文献
75.
Tsuyoshi Kurikawa Hiroaki Takeda Atsushi Nakajima Koji Kaya 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1997,40(1):65-69
In the gas phase, we have successfully synthesized organometallic clusters, Mn(benzene)m (M=3d transition metal atoms), by using a laser vaporization method. The measurements of mass spectra and ionization energies (Ei) have revealed that the organometallic clusters can take two types of structures; layered sandwich structures (m = n + 1) and metal clusters saturatedly covered with benzenes. For early transition metals of Sc, Ti, and V, only the multiple decker sandwich structure clusters were preferentially produced, in which benzene and metal atoms are alternately piled up. For late transition metals of Co and Ni, the metal clusters saturatedly surrounded by benzenes were also produced as well as the sandwich clusters. Furthermore, the Eis of M1(benzene)2 (M = Sc-Ni) were systematically measured and their electronic properties will be discussed. 相似文献
76.
Isocyanide—mercuric chloride complexes react readily with an excess of primary and secondary amines to give guanidines and metallic mercury in high yields through a redox decomposition reaction. In the presence of triethylamine, isocyanide—mercuric chloride complexes react with an equimolar amount of a primary amine to give a carbodiimide and metallic mercury. An intermediate organomercuric compound was isolated in the reaction of the isocyanide—mercuric chloride complex with pyrrolidone. 相似文献
77.
78.
Kano K Kitagishi H Tamura S Yamada A 《Journal of the American Chemical Society》2004,126(46):15202-15210
5,10,15,20-Tetrakis(4-sulfonatophenyl)porphinato iron(III) (Fe(III)TPPS) forms a very stable 1:2 complex with heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin (TMe-beta-CD), whose iron(III) center is located at a hydrophobic cleft formed by two face-to-face TMe-beta-CD molecules. Various inorganic anions (X(-)) such as F(-), Cl(-), Br(-), I(-), N(3)(-), and SCN(-) coordinate to Fe(III)TPPS(TMe-beta-CD)(2) to form five-coordinate high-spin Fe(III)TPPS(X)(TMe-beta-CD)(2), while no coordination occurs with ClO(4)(-), H(2)PO(4)(-), NO(3)(-), and HSO(4)(-). Except for F(-), none of the anions investigated coordinate to Fe(III)TPPS in the absence of TMe-beta-CD due to extensive hydration to the anions as well as to Fe(III)TPPS. The present system shows a high selectivity toward the N(3)(-) anion. The thermodynamics suggests that Lewis basicity, hydrophilicity, and shape of an X(-) anion are the main factors to determine the stability of the Fe(III)TPPS(X)(TMe-beta-CD)(2) complex. 相似文献
79.
Ammonium aromatic diselenoates were synthesized by reacting aromatic diselenoic acid 2-(trimethylsilyl)ethyl esters derived from aluminum 2-(trimethylsilyl)ethyl selenolate with aromatic selenoic acid O-methyl esters with ammonium fluorides. The results of molecular structure analysis and NMR studies of ammonium salts supported the double-bond character between the carbon atom and selenium atoms. 相似文献
80.
Ohno H Ando K Hamaguchi H Takeoka Y Tanaka T 《Journal of the American Chemical Society》2002,124(51):15255-15266
The base-mediated intramolecular amination of bromoallenes having an axial chirality is described. The treatment of (4S,aR)-4-alkyl-4-[N-(arylsulfonyl)amino]-1-bromobuta-1,2-dienes with NaH in DMF affords 2,3-cis-2-ethynylaziridines in good to excellent selectivity (2,3-cis:trans = 92:8-99:1). The reaction of (4S,aS)-bromoallenes with NaH/DMF also gives 2,3-cis-2-ethynylaziridines selectively (79:21-91:9). These experimental results have been rationalized by B3LYP density functional calculations together with the 6-31+G(d) basis set and the Onsager solvation model. The transition structures for cis-aziridine formation of both (4S,aR)- and (4S,aS)-bromoallenes in DMF are favored over the corresponding trans transition structures by 4.35 and 1.41 kcal/mol, respectively. Furthermore, the calculations predicted that a less polar solvent gives higher cis selectivity for (4S,aS)-bromoallenes. In fact, improvement of the cis selectivity to 99:1 has been realized by using a less polar solvent such as THF. The cyclization of bromoallenes bearing a beta- or gamma-amino group also affords four- and five-membered azacycles in a highly cis-selective manner. 相似文献