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81.
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
82.
Macroscopic and microscopic dissipative structural patterns formed in the course of drying the deionized aqueous colloidal
crystal suspensions of silica spheres (diameter: 103 nm) on a cover glass have been observed. Spoke-like and ring-like patterns
are formed in the macroscopic scale; the former is the crack in the sphere film and the latter is the hill accumulated with
spheres formed around the outside edge. The neighbored inter-spoke angle, thickness of the film, and other morphological parameters
have been discussed as a function of sphere concentration, concentration of sodium chloride, and the inclined angle of the
cover glass. Fractal patterns of the mud cracks are observed in the microscopic scale. Capillary forces between spheres at
the air-liquid surface and the relative rates between the water flow at the drying front and the convection flow of spheres
are important for the pattern formation.
Electronic Publication 相似文献
83.
Tatsuaki Yamaguchi Kimitoshi Saito Toshio Tsujimoto Hidetaka Yuki 《Journal of heterocyclic chemistry》1976,13(3):533-537
Nmr spectra of structural analogs of tenuazonic acid such as 3-acetyltetramic acid, 3-acetyltetronic acid, 3-acetylthiotetronic acid and others were investigated for elucidation of the tautomeric structures. These compounds have completely enolized β,β′-triketone systems, and the position of the nmr signals for the enolic proton shows that the strength of their intramolecular hydrogen-bonding is weaker than those of acyclic β,β′-triketones and six-membered cyclic triketones. The assignment was made for nmr signals split by the difference of the diamagnetic anisotropic effect in each tautomers. The percentages of each of the tautomers were calculated from the intensities of the corresponding nmr signals. The results were confirmed by means of 13C-nmr spectroscopy. 相似文献
84.
Tomohisa?Yamaguchi Keisuke?Kimura Akira?Tsuchida Tsuneo?OkuboEmail author Mitsuhiro?Matsumoto 《Colloid and polymer science》2005,283(10):1123-1130
Macroscopic and microscopic dissipative structural patterns formed in the course of drying the fractionated and monodisperse bentonite particles (plate-like in their shape) in aqueous deionized suspension and in the presence of NaCl have been studied on a cover glass. The patterns coexisted with the broad ring of the hill accumulated with the particles and with the round hills are formed around the outside edges of the film and in the center, respectively, in the macroscopic scale. By the addition of NaCl the pattern shifts from the broad ring to the round hill in the center. The spoke-like cracks, which have been observed for the suspensions of the spherical particles so often hitherto, are not observed at all for the bentonite suspensions. The characteristic convection flow of the particles and the interactions among the particles and substrate are important for the macroscopic pattern formation. Wrinkled, branch-like and/or star-like fractal patterns are observed in the microscopic scale. These patterns are determined mainly by the electrostatic and polar interactions between the particles and/or between the particle and the substrate in the course of drying. 相似文献
85.
Masao Kato Takao Shiraga Tatsumi Kimura Takashi Fukuda Hiro Matsuda Hachiro Nakanishi 《先进技术聚合物》2002,13(2):120-126
We synthesized some novel rigid NLO‐active maleimide copolymers bearing DR‐1 moieties ( PMPD , PHSD and PHND ). All copolymers exhibited high Tg's (190~197 °C), good solubilities for common solvents and excellent film‐forming properties. Dependence of film thickness on the d33 value for the poled copolymer films induced by corona poling was investigated and it was demonstrated that in less than thickness of 0.3 µm decrease of the thickness gives rise to remarkable increase in the d33 value. The poled copolymer films exhibited large d33 values (270 × 10?9 esu (film thickness 0.13 µm) for PMPD , 290 × 10?9 esu (0.12 µm) for PHSD and 350 × 10?9 esu (0.08 µm) for PHND ) as well as large r33 values (51.0 pmV?1 for PMPD and 60.4 pmV?1 for PHND ) which are significantly large compared to the value of LiNbO3 (31 pmV?1) as a typical EO material. The d33 values of the poled copolymers were kept constant even after standing 1000h at 80 °C, although a small decrease was observed at an initial stage. Further, the d33 values did not change up to ca. 123 °C upon heating at the rate of 10 °C/min in all cases. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
86.
[reaction: see text] Copper-mediated homocoupling of sterically hindered 2-(2,4,6-tri-tert-butylphenyl)-1-trialkylsilyl-2-phosphaethenyllithiums afforded 1,2-bis(trialkylsilyl)-3,4-diphosphacyclobutenes (1,2-dihydrodiphosphetenes) through a formal electrocyclic [2+2] cyclization in the P=C-C=P skeleton as well as 2-trimethylsilyl-1,4-diphosphabuta-1,3-diene. Reduction of 1,2-bis(trimethylsilyl)-3,4-diphosphacyclobutenes followed by quenching with electrophiles afforded ring-opened products, (E)-1,2-bis(phosphino)-1,2-bis(trimethylsilyl)ethene and (Z)-2,3-bis(trimethylsilyl)-1,4-diphosphabut-1-ene. The structures of the ring-opened products indicated E/Z isomerization around the C=C bond after P-P bond cleavage of 5, and the isomerization of the P-C=C skeleton. Ring opening of 1,2-bis(trimethylsilyl)-3,4-diphosphacyclobutenes affording (E,E)- and (Z,Z)-1,4-diphosphabuta-1,3-dienes was observed upon desilylation. 相似文献
87.
[reaction: see text] Phosphates from 3-substituted 4,4,4-trifluorobut-2-en-1-ols were found to be effective for construction of CF3-containing quaternary carbon centers by way of Cu(I)-catalyzed Grignard reactions in the presence of catalytic amounts of CuCN and trimethylsilyl chloride (TMSCl) in an anti S(N)2' manner. 相似文献
88.
Stereoblock poly(lactic acid) consisting of D- and L-lactate stereosequences can be successfully synthesized by solid-state polycondensation of a 1:1 mixture of poly(L-lactic acid) and poly(D-lactic acid). In the first step, melt-polycondensation of L- and D-lactic acids is conducted to synthesize poly(L-lactic acid) and poly(D-lactic acid) with a medium-molecular-weight, respectively. In the next step, these poly(L-lactic acid) and poly(D-lactic acid) are melt-blended in 1:1 ratio to allow formation of their stereocomplex. In the last step, this melt-blend is subjected to solid-state polycondensation at temperature where the dehydrative condensation is allowed to promote chain extension in the amorphous phase with the stereocomplex crystals preserved. Finally, stereoblock poly(lactic acid) having high-molecular-weight is obtained. The stereoblock poly(lactic acid) synthesized by this way shows a higher melting temperature in consequence of the controlled block lengths and the resulting higher-molecular-weight. The product characterization as well as the optimization of the polymerization conditions is described. Changes in M(w) of stereoblock poly(lactic acid) (sb-PLA) as a function of the reaction time. 相似文献
89.
New hydroxyl protecting groups of a safety-catch type, i.e., 4-methylsulfinylbenzyl-oxycarbonyl (Msz) group for Tyr and 4-methylsulfinylbenzyl (Msob) ether for Thr, have been developed. O-Msz and O-Msob groups are stable under both acidic and basic conditions and can be removed by a one-pot reaction involving reductive acidolysis using tetrachlorosilane-trifluoroacetic acid (TFA)-scavengers. Using these new protecting groups, a 17 residue-peptide, gamma-endorphin, was successfully synthesized by the efficient solid phase method. 相似文献
90.
Yorihiko Sasaki Shigehiro Konaka Takao Iijima Masao Kimura 《International journal of quantum chemistry》1982,21(2):475-485
The total (elastic and inelastic) intensity of electrons scattered by CO2 was measured in the s range of 1 to 12 Å?1 and compared with the theoretical intensity calculated from the Hartree-Fock molecular wave function and those calculated for the independent-atom-model (IAM ) molecule. In the range of s ? 4 Å?1 the electron correlation effect on the total scattered intensity was found to be represented by that for the IAM molecule. 相似文献