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31.
Conducting polymer (CP) films, used as ion-sensing membranes under open circuit potentiometric conditions, are usually characterised with rather high detection limit, in the range of 10−4-10−5 mol dm−3. This effect is unfavourable, not only from the point of view of CP applications in potentiometry as ion sensitive membranes, but also when these materials are used as ion-to-electron transducers (solid contacts) for ion-selective electrodes. The theoretical considerations presented underline the crucial role of spontaneous processes of polymer charging/discharging—the source of observed high detection limit of sensors comprising CP layer under zero current conditions. Although the mechanism of occurring process is different from that observed for plastic, solvent polymeric based ion-selective electrodes, the ultimate result—alteration of activity of electrolyte at the membrane/solution interface leading to elevation of the detection limit—is the same.The method of estimation of parameters characterising spontaneous charge transfer processes is presented. The values obtained can be used to calculate the resulting polymer/solution interface activity of electrolyte ions, thus the detection limit of CP membrane can be theoretically predicted.A method of lowering of the detection limit of conducting polymer membranes, applying galvanostatic polarisation to compensate the spontaneous process of polymer charging/discharging, is presented.The experimental results obtained for poly(pyrrole), poly(N-methylpyrrole) and poly(3,4-ethylenedioxythiophene) are in good accordance with predictions of the presented model. 相似文献
32.
Mariia Svyntkivska Tomasz Makowski Ewa Piorkowska Marek Brzezinski Agata Herc Anna Kowalewska 《Molecules (Basel, Switzerland)》2021,26(5)
Electrospun nonwovens of poly(L-lactide) (PLLA) modified with multiwall carbon nanotubes (MWCNT) and linear ladder-like poly(silsesquioxane) with methoxycarbonyl side groups (LPSQ-COOMe) were obtained. MWCNT and LPSQ-COOMe were added to the polymer solution before the electrospinning. In addition, nonwovens of PLLA grafted to modified MWCNT were electrospun. All modified nonwovens exhibited higher tensile strength than the neat PLA nonwoven. The addition of 10 wt.% of LPSQ-COOMe and 0.1 wt.% of MWCNT to PLLA increased the tensile strength of the nonwovens 2.4 times, improving also the elongation at the maximum stress. 相似文献
33.
Andrzej Kudelski Marcin Pisarek Agata Roguska Marcin Hodyski Maria Janik‐Czachor 《Journal of Raman spectroscopy : JRS》2012,43(10):1360-1366
Silver nanoparticles deposited on various ‘inert’ porous materials (mainly Al2O3 and TiO2) are often used as substrates for surface‐enhanced Raman scattering (SERS) measurements. In this study, we used the sputter deposition technique to cover tubular arrays of Al2O3 and TiO2 with Ag nanoparticles. Raman spectra of pyridine (as a probe molecule) and of two selected dyes (5‐(4‐dimethylaminobenzylidene)rhodanine and 5‐(4‐(dimethylamino)benzylidene)‐3‐(3‐methoxypropyl)rhodanine) adsorbed on fabricated Ag/TiO2‐n/Ti and Ag/Al2O3‐n/Al substrates were measured. We found that the SERS spectra of pyridine adsorbed on Ag nanoparticles deposited on an Al2O3‐n/Al substrate are distinctly different from those measured for an Ag/TiO2‐n/Ti composite. Similar effects were observed for dyes adsorbed on the surface of both composites. The spectral differences between two kinds of composites (Ag/TiO2‐n/Ti and Ag/Al2O3‐n/Al) are discussed in terms of (1) the modified electronic structure of the Ag nanoparticles due to their interaction with different substrate materials and (2) the different atomic topology of the metal particles thus deposited on the surfaces of the substrates. Composite samples were also studied with the aid of scanning electron microscopy (SEM) and Auger electron spectroscopy (AES) to reveal their characteristic morphological and chemical features. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
34.
Agata Biaoska Zbigniew Ciunik 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(12):o853-o855
The crystal structures of brucine (2,3‐dimethoxystrychnidin‐10‐one), C23H26N2O4, brucine acetone solvate, C23H26N2O4·C3H6O, and brucine 2‐propanol solvate dihydrate, C23H26N2O4·C3H7O·2H2O, have been determined. Crystals of brucine and its 2‐propanol solvate dihydrate exhibit similar monolayer sheet packing, whereas crystals of the acetone solvate adopt a different mode of packing, as brucine pillars. The solvent appears to control the brucine self‐assembly on the basis of common donor–acceptor properties of the surfaces. 相似文献
35.
36.
This paper describes a new approach to the problem of computing spherical expansions of zonal functions on Euclidean spheres.
We derive an explicit formula for the coefficients of the expansion expressing them in terms of the Taylor coefficients of
the profile function rather than (as done usually) in terms of its integrals against Gegenbauer polynomials. Our proof of
this result is based on a polynomial identity equivalent to the canonical decomposition of homogeneous polynomials and uses
only basic properties of this decomposition together with simple facts concerning zonal harmonic polynomials. As corollaries,
we obtain direct and apparently new derivations of the so-called plane wave expansion and of the expansion of the Poisson
kernel for the unit ball.
Received: 26 January 2007 相似文献
37.
The objective of this paper is to provide information about application of solid-phase extraction (SPE) for isolation of nine high-intensity sweeteners (acesulfame-K, alitame, aspartame, cyclamate, dulcin, neotame, saccharin, sucralose and neohesperidin dihydrochalcone) from aqueous solutions. The influence of several types of LC-MS compatible buffers (different pH values and compositions) on their recovery has been studied and discussed. A number of commercially available SPE cartridges, such as Chromabond C18ec, Strata-X RP, Bakerbond Octadecyl, Bakerbond SDB-1, Bakerbond SPE Phenyl, Oasis HLB, LiChrolut RP-18, Supelclean LC-18, Discovery DSC-18 and Zorbax C18 were tested in order to evaluate their applicability for the isolation of analytes. Very high recoveries (better than 92%) of all studied compounds were obtained using formic acid-N,N-diisopropylethylamine buffer adjusted to pH 4.5 and C18-bonded silica sorbents. Behaviour of polymeric sorbents strongly depends on their structure. Strata-X RP behaves much like a C18-bonded silica sorbent. Recoveries obtained using Oasis HLB were comparable with those observed for silica-based sorbents. The only compound less efficiently (83%) retained by this sorbent was cyclamate. Bakerbond SDB-1 shows unusual selectivity towards aspartame and alitame. Recoveries of these two sweeteners were very low (26 and 42%, respectively). It was also found that aspartame and alitame can be selectively separated from the mixture of sweeteners using formic acid-triethylamine buffer at pH 3.5. 相似文献
38.
Izabela Kaminska Joanna Niedziolka-Jonsson Agata Roguska Marcin Opallo 《Electrochemistry communications》2010,12(12):1742-1745
Gold nanoparticles have been electrodeposited on an electrode through electrogeneration at an ITO|AuCl4? solution in an ionic liquid|aqueous electrolyte three-phase junction. The electrodeposition was carried out by inverted double-pulse potential chronoamperometry. The direct reduction of AuCl4? ions at the electrode is followed by a counterion transfer through the liquid|liquid interface. Contrary to the electrodeposition from a single ionic liquid phase, scanning electron microscopy reveals that the shape of the resulting nanoparticles is highly angular and well-developed with a diameter of 110 ± 30 nm. Catalytic oxidation of glucose on the modified electrode is demonstrated. 相似文献
39.
Agata L. Starosta Viktoriya V. Karpenko Anna V. Shishkina Aleksandra Mikolajka Natalia V. Sumbatyan Frank Schluenzen Galina A. Korshunova Alexey A. Bogdanov Daniel N. Wilson 《Chemistry & biology》2010,17(5):504-514
Highlights? Macrolides exhibit nascent polypeptide chain–dependent inhibition ? Peptides can form specific interactions with the ribosomal tunnel ? A covalent bond between tylosin and the ribosome is necessary for inhibitory activity 相似文献
40.
Rafal Kruszynski Agata Trzesowska‐Kruszynska 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(9):o449-o454
In the title compounds, C7H6ClN2O+·NO3− and C7H6ClN2O+·ClO4−, the ions are connected by N—H...O hydrogen bonds and halogen interactions. Additionally, in the first compound, co‐operative π–π stacking and halogen...π interactions are observed. The energies of the observed interactions range from a value typical for very weak interactions (1.80 kJ mol−1) to one typical for mildly strong interactions (53.01 kJ mol−1). The iminium cations exist in an equilibrium form intermediate between exo‐ and endocyclic. This study provides structural insights relevant to the biochemical activity of 2‐amino‐5‐chloro‐1,3‐benzoxazole compounds. 相似文献