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271.
272.
273.
Shao-Chen Yang Qihuang Gong Zongju Xia Y. H. Zou Y. Q. Wu D. Qiang Y. L. Sun Z. N. Gu 《Applied physics. B, Lasers and optics》1992,55(1):51-53
The nonlinear third-order optical susceptibility of C70 in a toluene solution is measured for the first time by the method of degenerate four-wave mixing using 10 ns laser pulses at 1.06 m. The third-order susceptibility X
in
(3)
is 5.6×10–12 esu for a C70 toluene solution at a concentration of 0.476 g/l. The correspondent magnitude of the hyperpolarizability 1111 of the C70 molecule is 1.2×10–30 esu which is in a good agreement with the prediction given by the model of a free electron in a spherical box. 相似文献
274.
Li ZT Zhang XL Lian XD Yu YH Xia Y Zhao CX Chen Z Lin ZP Chen H 《The Journal of organic chemistry》2000,65(17):5136-5142
A variety of novel calix[4]arene-incorporating crown ethers with or without intramolecular hydrogen bonding have been prepared by two efficient methods and utilized as donor rings to assemble calix[4]arene [2]catenanes based on pi-stacking interaction between hydroquinone and bipyridinium units. Treatment of calix[4]arene crown ethers 4, 10a, or 10b, whose cone conformation was fixed by intramolecular hydrogen bonding within the calix[4]arene moiety, with dicationic salt 15 x 2PF6 and dibromide 16 afforded the corresponding [2]catenanes 17a x 4PF6, 17b x 4PF6, and 17c x 4PF6 in 20%, 53%, and 55% yields, respectively, whereas from the reactions of 15 x 2PF6 and dibromide 16 in the presence of conformationally flexible 11 or 12 with a cone conformation kept by two propyl groups, [2]catenanes 18 x 4PF6 and 19 x 4PF6 were obtained in 12% and 6% yields. [2]Catenanes 21a x 4Cl, 21b x 4Cl, and 21c x 4Cl, incorporating calix[4]arene in both the donor and acceptor rings, were also successfully assembled from 10a or 10b, 16, and dicationic salts 20a x 2PF6 or 20b x 2PF6. The dynamic 1H NMR and absorption spectra of the [2]catenanes have been investigated, which revealed a strongest donor-acceptor interaction in 17a x 4PF6 and that the cone [2]catenanes 17a-c x 4PF6 can isomerize to the partial cone isomer at high temperature. The difference of the dynamic properties of these catenanes was discussed. The results demonstrate that catenation is one new general method to change the conformational distributions of calix[4]arenes. 相似文献
275.
A dual-electrode approach for highly selective detection of glucose based on diffusion layer theory: experiments and simulation 总被引:1,自引:0,他引:1
A dual-electrode configuration for the highly selective detection of glucose in the diffusion layer of the substrate electrode is presented. In this approach, a glassy carbon electrode (GCE, substrate) modified with a conductive layer of glucose oxidase/Nafion/graphite (GNG) was used to create an interference-free region in its diffusion layer by electrochemical depletion of interfering electroactive species. A Pt microelectrode (tip, 5 microm in radius) was located in the diffusion layer of the GNG-modified GCE (GNG-G) with the help of scanning electrochemical microscopy. Consequently, the tip of the electrode could sense glucose selectively by detecting the amount of hydrogen peroxide (H2O2) formed from the oxidization of glucose on the glucose oxidase layer. The influences of parameters, including tip-substrate distance, substrate potential, and electrolyzing time, on the interference-removing efficiency of this dual-electrode approach have been investigated systematically. When the electrolyzing time was 30 s, the tip-substrate distance was 1.8 a (9.0 microm) (where a is the radius of the tip electrode), the potentials of the tip and substrate electrodes were 0.7 V and 0.4 V, respectively, and a mixture of ascorbic acid (0.3 mM), uric acid (0.3 mM), and 4-acetaminophen (0.3 mM) had no influence on the glucose detection. In addition, the current-time responses of the tip electrode at different tip-substrate distances in a solution containing interfering species were numerically simulated. The results from the simulation are in good agreement with the experimental data. This research provides a concept of detection in the diffusion layer of a substrate electrode, as an interference-free region, for developing novel microelectrochemical devices. 相似文献
276.
Single crystals of {[Cu(TO)2(H2O)2](NO3)2}n (TO: 1, 2, 4‐triazol‐5‐one) were grown by slow evaporation from aqueous solution. It crystallizes in the orthorhombic space group Pbca, with a = 7.082(1), b = 10.285(1), c = 17.911(3)Å, V = 1304.6(3)Å3, Z = 4. The CuII distorted octahedra are bridged by bidentate TO ligands into infinite 2‐D interlaced rhombic grid‐like network planes, {[Cu(TO)2(H2O)2]2+}n. Hydrogen bonds, electrostatic interactions, and weak van der Waals' forces assemble these planes and the NO3— anions to a layered structure. The title compound decomposes at 153.4 °C to the final products, Cu(CN)2 and CuO. 相似文献
277.
Xu‐Xia Sun Shu‐Lan Ma Hai‐Bo Huang Chuan‐Min Qi 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(2):o87-o88
In the crystal structure of the title compound, C21H21NO2, strong N—H⋯O and O—H⋯O hydrogen bonds exist. The keto–amine form is favoured over the enol–imine form in the tautomerism. Six‐membered chelate rings formed by intramolecular hydrogen bonds increase the stability of the whole molecule. Intermolecular hydrogen bonds link adjacent units together, forming an infinite one‐dimensional chain parallel to the a axis. 相似文献
278.
The effect of ß-cyclodextrin (ß-CD) on cetyltrimethylammonium bromide (CTAB) micellar properties was studied by the determination of the diffusion coefficient, D. When the CTAB micelles have a spherical structure, D firstly increased and then remained unchanged, while the micellar aggregation number, N, decreased with the addition of ß-CD. When the CTAB concentration was less than the first critical micellar concentration, CTAB molecules could be included into ß-CD cavities with the molar ratio of CTAB to ß-CD being about 1:1. However, when the CTAB concentration was higher than the first critical micellar concentration, mixed spherical micelles were formed with the molar ratio of CTAB to ß-CD being 9:1. 相似文献
279.
Chun Xia Tan Ruo Fei Feng Xiao Xia Peng 《中国化学快报》2007,18(5):505-508
By the condensation of 2,6-bis(4-amino-5-mercapto-[1,2,4]-triazoles-2)pyridine with aromatic acid in the presence of phosphorus oxychloride. Compounds of 2,6-bis(6-aryl-[1,2,4]-triazolo[3,4-b][1,3,4]-thiadiazole-3-yl)pyridines were synthesized. Their structures were confirmed by IR, ^1H NMR spectroscopies and elemental analysis. Their electrochemical behavior and cyclic voltammogram also were be studied. The results showed that they have high ionization potentials and good affinity. 相似文献
280.
Using the self-assembly β-cyclodextrin (β-CD) and cetyltrimethylammonium bromide (CTAB) as structure-directing agents, high-quality ordered MCM-41 silicas have been prepared. Small-angle X-ray diffraction (SXRD), N2 adsorption-desorption and scanning electron microscope (SEM) techniques were used to characterize the calcined samples. Results showed that the pore structure of the resulting mesoporous silica belonged to the two-dimensional hexagonal structure (space group p6mm). The high-quality hexagonal structure was formed as n?1 (n denotes molar ratio of β-CD to CTAB). N2 adsorption-desorption curves revealed type IV isotherms, H4 hysteresis loops, for all samples, and H1 hysteresis loops for samples at n=0, 0.1, 1 and 2, respectively. The pore size and the pore wall thickness of the samples increased with the increase in n values, respectively. 相似文献