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151.
Miklós Orbán 《Reaction Kinetics and Catalysis Letters》1990,42(2):343-353
The role of copper ions in the copper-catalyzed chemical reactions is discussed. It is pointed out that copper ions can induce oscillatory behavior in many systems for the following reasons: (1) Copper cations can exist in three oxidation states (+1, +2 and +3); (2) Copper cations can form precipitates and stable complexes with a large number of reactants and intermediates; (3) Copper ions can participate in both oxidation and reduction processes, due to the surprisingly large range of redox potentials exhibited by the Cu2+/Cu+ and Cu3+/Cu2+ couples (known redox potentials span from 0.1 to 1.8 V, depending on the counter-ion or ligand present). 相似文献
152.
Fe3O4 Anisotropic Nanostructures in Hydrogels: Efficient Catalysts for the Rapid Removal of Organic Dyes from Wastewater
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Yang Gao Chen Hu Wen Jiang Zheng Prof. Dr. Sen Yang Prof. Dr. Fei Li Dr. Shao Dong Sun Prof. Dr. Miklós Zrínyi Prof. Dr. Yoshihito Osada Prof. Dr. Zhi Mao Yang Prof. Dr. Yong Mei Chen 《Chemphyschem》2016,17(13):1999-2007
Fe3O4 anisotropic nanostructures that exhibit excellent catalytic performance are rarely used to catalyze Fenton‐like reactions because of the inevitable drawbacks resulting from traditional preparation methods. In this study, a facile, nontoxic, water‐based approach is developed for directly regulating a series of anisotropic morphologies of Fe3O4 nanostructures in a hydrogel matrix. In having the advantages of both the catalytic activity of Fe3O4 and the adsorptive capacity of an anionic polymer network, the hybrid nanocomposites have the capability to effect the rapid removal of cationic dyes, such as methylene blue, from water samples. Perhaps more interestingly, hybrid nanocomposites loaded with Fe3O4 nanorods exhibit the highest catalytic activity compared to those composed of nanoneedles and nanooctahedra, revealing the important role of nanostructure morphology. By means of scanning electrochemical microscopy, it is revealed that Fe3O4 nanorods can efficiently catalyze H2O2 decomposition and thus generate more free radicals (.OH, .HO2) for methylene blue degradation, which might account for their high catalytic activity. 相似文献
153.
Czaun M Hevesi L Takafuji M Ihara H 《Chemical communications (Cambridge, England)》2008,(18):2124-2126
A new route for the preparation of magneto-responsive polymeric gels involving iron nanoparticles as nano cross-linkers has been described. 相似文献
154.
We report here on a method for preparation of precise laboratory solutions using controlled diffusion for dosing. The desired
chemical is delivered into the target solution from a stock solution through a mass-transport-limiting delivery port that
blocks convection but allows reproducible diffusive transport. Solution making with this approach involves a single step irrespective
of how low the desired concentration is. Diffusional delivery of chemicals involves no appreciable movement of water and,
thus, no addition of volume. The approach is therefore particularly suitable for standard addition. Precise solutions of usual
laboratory volumes can be made within a short time period with proper design of the delivery port or ports. Comparison with
the performance of conventional methods of routine solution preparation shows that better precision can be achieved with less
labor using this approach. 相似文献
155.
156.
Following Csörg?, Szyszkowicz and Wang (Ann. Stat. 34, 1013–1044, 2006) we consider a long range dependent linear sequence. We prove weak convergence of the uniform Vervaat and the uniform Vervaat error processes, extending their results to distributions with unbounded support and removing normality assumption. 相似文献
157.
Istvan Hajdu Magdolna Bodnár Genovéva Filipcsei John F. Hartmann Lajos Daróczi Miklós Zrínyi János Borbély 《Colloid and polymer science》2008,286(3):343-350
The present paper describes the preparation and characterization of novel biodegradable nanoparticles based on self-assembly
of poly-gamma-glutamic acid (γ-PGA) and chitosan (CH). The nanosystems were stable in aqueous media at low pH conditions.
Solubility of the systems was determined by turbidity measurements. Surface charge and mobility were measured electrophoretically.
The particle size and the size distribution of the polyelectrolyte complexes were identified by dynamic light scattering and
transmission electron microscopy (TEM). It was found that the size and size distribution of the nanosystems depends on the
concentrations of γ-PGA and CH solutions and their ratio as well as on the pH of the mixture and the order of addition. The
diameter of individual particles was in the range of 20–285 nm measured by TEM, and the average hydrodynamic diameters were
between 150 and 330 nm. These biodegradable, self-assembling stable nanocomplexes might be useful for several biomedical applications. 相似文献
158.
Kéki S Török J Nagy L Zsuga M 《Journal of the American Society for Mass Spectrometry》2008,19(5):656-665
Atmospheric pressure photoionization mass spectrometric (APPI-MS) study on three types of polyisobutylene derivatives is reported. Two of the polyisobutylenes investigated were polyisobutylene with dihydroxy and diolefinic end-groups derived from aromatic moieties [dicumyl chloride, 1,4-bis(2-chloro-2-propyl)benzene], and the third contained no aromatic moieties with a monohydroxy end-group. All three polyisobutylene derivatives (PIBs) had an average molecular weight (M(n)) of approximately 2000 g/mol, with a polydispersity lower than 1.2. In the positive ion APPI mode, protonated PIB molecules were formed, but the molecular weights obtained were considerably lower than those expected, indicating fragmentation of the PIB chains. In the negative APPI mode, using solvents such as tetrahydrofuran and toluene as dopants, no signal was obtained. However, in chlorinated solvents, such as CCl(4), CHCl(3), and CH(2)Cl(2), in the presence of toluene dopant, PIB adducts with chloride ions were formed with relatively high signal intensity. In the case of CH(2)Cl(2), no dopant (toluene) was necessary to generate chlorinated adduct ions, albeit increasing the toluene concentration in the flow increased the PIB signal intensity. The effect of the toluene concentration on PIB signal intensity was studied and models that include (1) photoionization of toluene, (2) formation of chloride ions from the chlorinated solvents by dissociative electron capture, (3) formation of chlorinated adduct ions and charge recombination reactions between the toluene radical cation, (4) chloride ions, and (5) chlorinated adduct ions are proposed based on the experimental results. 相似文献
159.
Micellar proportion, t(prop,mic) = t(mic)/t(m), a quantity expressing how much time is spent by the analyte in the micellar phase related to its whole migration time (t(m)) has been introduced by utilizing the micellar phase residence time (t(mic)). The t(prop,mic) values have been determined for analytes of different chemical structures (alkyl benzene and alkyl phenone homologous series, alcohols, strongly hydrophobic peptides) studied by micellar elektrokinetic chromatography (MEKC) using various cationic and anionic pseudostationary phases. A good linear correlation was obtained between t(prop,mic) and the calculated hydrophobicity (CLOGP) of the analytes for all pseudostationary phases (CLOGP = A.logt(prop,mic) + B). Considering a given pseudostationary phase, t(prop,mic) as a relative quantity is a suitable parameter to characterize and compare experimentally the behavior of the various analytes in MEKC. Applying a set of probe molecules with known hydrophobicity, the CLOGP(50) value (showing the value of hydrophobicity of a virtual molecule spending exactly 50% of its migration time in the pseudostationary phase) has been calculated for each pseudostationary phase applied here. This experimentally determinable numerical value (characterizing the pseudostationary phase) can be utilized to compare the hydrophobicity and hence retention ability of the pseudostationary phases. The t(prop,mic) value was found to be applicable to compare the methylene selectivity of the different pseudostationary phases as well: logt(prop,mic) = A.Z + B, where Z is the number of carbon atoms of the alkyl chain in the alkyl benzene homologous series. 相似文献
160.