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Model Calculations and Experimental Studies as a Route Toward Simplification of the Kinetic Mechanism of the H2O2–NaSCN–NaOH–CuSO4 Homogeneous Oscillator 下载免费PDF全文
Oscillatory chemical reactions are usually characterized by complicated kinetic mechanisms in which the source of instability is combined with the parallel dissipative process. One of such systems is the H2O2–NaSCN–NaOH–CuSO4 homogeneous oscillator, in which dynamic instabilities are associated with the irreversible oxidation of thiocyanate ions with hydrogen peroxide. Following our previous studies on this system, we now propose further intuitive and substantial simplification of its kinetic mechanism toward the scheme involving only five intermediates. Its compatibility with our previous, nine‐variable model is verified in terms of model calculations, compared with experimental potentiometric and spectrophotometric data. In particular, supercritical nature of a Hopf bifurcation as a route toward oscillations born out of a single steady state upon increasing catalyst (copper species) concentration was observed in the model and an analogous type of bifurcation is suggested by available experimental data. Our work is a step toward final reduction of the mechanism of the studied system to the “minimum oscillator,” the concept used earlier, e.g., for the Belousov–Zhabotinsky reaction, of however remarkably different kinetic mechanism. 相似文献
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Smriti Singh Ilona Zilkowski Andrea Ewald Tobias Maurell‐Lopez Krystyna Albrecht Martin Möller Jürgen Groll 《Macromolecular bioscience》2013,13(4):470-482
Nanogels consist of three dimensionally cross‐linked hydrophilic polymer chains and can thus be easily modified through functionalization of the polymeric building blocks, for example to yield stimuli‐sensitive materials. For drug transport and intracellular release, redox‐sensitive systems are especially of interest, as the intracellular space is reductive. In this study, parameters that allow preparation of nanogels with tunable size between 150 and 350 nm are systematically evaluated and identified. Most importantly, a new and mild oxidation catalyst, alloxan, is introduced for the preparation of the nanogels. This broadens the range of possible payloads to more‐sensitive molecules. Particle stability, degradation in cytosolic conditions, and cytocompatibility in concentrations up to 10 mg · mL?1 are demonstrated.
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Ramona Samba Kai Fuchsberger Ilona Matiychyn Sebastian Epple Lydia Kiesel Alfred Stett Wolfgang Schuhmann Martin Stelzle 《Electroanalysis》2014,26(3):548-555
In this work, composite microelectrodes from poly(3,4‐ethylenedioxythiophene) (PEDOT) and carbon nanotubes (CNT) are characterized as electrochemical sensing material for neurotransmitters. Dopamine can be detected using square wave voltammetry at these microelectrodes. The CNTs improve the sensitivity by a factor of two. In addition, the selectivity towards dopamine in the presence of ascorbic acid and uric acid was examined. While both electrodes, PEDOT and PEDOT‐CNT are able to detect all measured concentrations of dopamine in the presence of uric acid, small concentrations of dopamine and ascorbic acid are only distinguishable at PEDOT‐CNT electrodes. Changing the pH has a strong influence on the selectivity. Moreover, it is possible to detect concentrations as low as 1 µM dopamine in complex cell culture medium. Finally, other catecholamines like serotonin, epinephrine, norepinephrine and L ‐dopa are also electrochemically detectable at PEDOT‐CNT microelectrodes. 相似文献
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Julia Bkowicz Ilona Turowska‐Tyrk 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(8):o437-o440
The analysis of the crystal structures of rac‐3‐benzoyl‐2‐methylpropionic acid, C11H12O3, (I), morpholinium rac‐3‐benzoyl‐2‐methylpropionate monohydrate, C4H10NO+·C11H11O3−·H2O, (II), pyridinium [hydrogen bis(rac‐3‐benzoyl‐2‐methylpropionate)], C5H6N+·(H+·2C11H11O3−), (III), and pyrrolidinium rac‐3‐benzoyl‐2‐methylpropionate rac‐3‐benzoyl‐2‐methylpropionic acid, C4H10N+·C11H11O3−·C11H12O3, (IV), has enabled us to predict and understand the behaviour of these compounds in Yang photocyclization. Molecules containing the Ar—CO—C—C—CH fragment can undergo Yang photocyclization in solvents but they can be photoinert in the crystalline state. In the case of the compounds studied here, the long distances between the O atom of the carbonyl group and the γ‐H atom, and between the C atom of the carbonyl group and the γ‐C atom preclude Yang photocyclization in the crystals. Molecules of (I) are deprotonated in a different manner depending on the kind of organic base used. In the crystal structure of (III), strong centrosymmetric O...H...O hydrogen bonds are observed. 相似文献