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A novel determination method of electroinactive molecules by means of electrochemical technique is presented. A new self-assembled monolayer containing cyclodextrin (CD) is prepared with mono(6-o-p-tolylsulfonyl)-β-cyclodextrin. Although this derivatization process leads to a β-CD coverage of 10% of a full monolayer, this layer shows an effective host-guest response to ferrocene. The interfacial ferrocene complexation gives a response similar to that expected for a Langmuir adsorption isotherm yielding a stability constant of 4.2 ×104 mol-1· L and a maximum ferrocene coverage of 8.6×10-12 mol/cm2. The redox peak currents of the surface-confined ferrocene decrease upon addition of competing β-CD guest species to the solution, such as m-toluic acid (mTA) and sodium dodecyl sulfonate (SDS). This principle has been used for the determination of the electroinactive molecules, mTA and SDS in the concentration ranges of 0.8-2.7 μmol/L and 5-100 nmol/L, respectively. 相似文献
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John A. Cowan Judith A. K. Howard Michael A. Leech 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(10):1196-1198
4,4′-Bipyridine (BPY) and 2,3,5,6-tetrahydroxy-1,4-benzoquinone (THBQ) crystallize in a 3:2 ratio as a neutral molecular adduct, 3C10H8N2·2C6H4O6, in space group P. There are two independent and centrosymmetric THBQ molecules and two different BPY molecules in the asymmetric unit, one of which lies about an inversion centre. The molecules link together through O—H⃛O and O—H⃛N hydrogen bonds to form three interpenetrating networks which create a `superlattice' of three times the volume of the primitive cell. 相似文献
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Anna M. Nowicka Agata Kowalczyk Mikolaj Donten Dónal Leech Maria Hepel Zbigniew Stojek 《Electroanalysis》2010,22(20):2323-2329
This paper presents a way of modification of crystalline gold surface with a high quality layer of gold nanoparticles (Au NPs) via self‐assembled dithiol. The application of additional Au NPs monolayer prepared at various temperatures was tested with three types of biosensors previously described in the literature. The examined DNA biosensors differed by the detection method and the way of the immobilization of DNA probe at the modified gold electrode surface. For the immobilization of DNA probe in the sensing layer either the formation of SAM or the affinity binding (biotin – sterptavidin) or covalent attachment were used. The necessary condition of successful preparation of a perfect such monolayer is the preparation temperature of 4 °C. The preparation of Au NPs layers at higher than 4 °C temperatures leads to poor repeatability and unsatisfactory precision of the measurements. The application of the perfect Au monolayer lowers the detection limit (circa by 10 to 100 times) for all tested DNA biosensors. 相似文献
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A chemically modified graphite electrode was prepared by using a dual film of [Os(bpy)2(PVP)10Cl]Cl polymer and Nafion. The modified electrode showed excellent electrocatalytical activity for the oxidation of norepinephrine (NE) and an ability to eliminate efficiently the interference of ascorbic acid and other anions. The catalytic peak currents obtained from the cyclic voltammograms increased linearly with increasing concentration of NE. A log-log plot of catalytic current versus NE concentration showed a dual-linear relationship in the ranges 1.8 x 10(-8)-4.4 x 10(-6) M and 4.4 x 10(-6)-2.9 x 10(-4) M with correlation coefficients of 0.990 and 0.999, respectively. The detection limit was about 18 nM (3 delta). At a potential of +500 mV the chronoamperometric response showed a linear relationship between the steady state current and NE concentration in the range 1.3-130 microM. With a further increase in NE concentration a Michaelis-Menten-shaped response was observed. The apparent Michaelis-Menten constant and the maximum current were 1.7 mM and 86 microA, respectively. The modified electrode showed excellent reproducibility, sensitivity and stability for the determination of NE at trace levels. 相似文献
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Francesca P. A. Fabbiani Charlotte K. Leech Kenneth Shankland Andrea Johnston Philippe Fernandes Alastair J. Florence Norman Shankland 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(11):o659-o663
Bendroflumethiazide, or 3‐benzyl‐6‐(trifluoromethyl)‐3,4‐dihydro‐2H‐1,2,4‐benzothiadiazine‐7‐sulfonamide 1,1‐dioxide, is reported to crystallize as 1:1 solvates with acetone, C15H14F3N3O4S2·C3H6O, and N,N‐dimethylformamide, C15H14F3N3O4S2·C3H7NO. A detailed investigation of the crystal packing and intermolecular interactions is presented by means of Hirshfeld surface analysis. This analysis confirms the atomic positions of methyl H atoms of the solvent molecules that were inferred from the X‐ray data and provides a useful tool for structure validation. 相似文献
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We investigate nonlinear oscillations in a fourth-order partialdifferential equation which models a suspension bridge. Previouswork establishes multiple periodic solutions when a parameterexceeds a certain eigenvalue. In this paper, we use Leray-Schauderdegree theory to prove that if the parameter is increased further,beyond a second eigenvalue, then additional solutions are created. 相似文献