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Université de Neuchâtel

Computer simulation of ion-selective membrane electrodes and related systems by finite-difference procedures

Morf, Werner E. ; Pretsch, Ernö ; de Rooij, Nicolaas F.

In: Journal of Electroanalytical Chemistry, 2007, vol. 602, no. 1, p. 43-54

A simple but powerful numerical simulation for analyzing the electrochemical behavior of ion-selective membranes and liquid junctions is presented. The computer modeling makes use of a finite-difference procedure in the space and time domains, which can be easily processed (e.g., with MS Excel software) without the need for complex mathematical evaluations. It leads to convincing results on the...

Université de Neuchâtel

Theory and computer simulation of the time-dependent selectivity behavior of polymeric membrane ion-selective electrodes

Morf, Werner E. ; Pretsch, Ernö ; de Rooij, Nicolaas F.

In: Journal of Electroanalytical Chemistry, 2008, vol. 614, no. 1-2, p. 15-23

A theoretical treatment of the time-dependent potential response of ion-selective electrodes to sample solutions containing primary and interfering ions is presented. The theory accounts for the influence of ion fluxes in the electrode membrane and the contacting aqueous sample layer and describes the variations in the apparent selectivity behavior as a function of the measuring time. The...

Université de Neuchâtel

Theoretical treatment and computer simulation of microelectrode arrays

Morf, Werner E. ; Koudelka-Hep, Milena ; de Rooij, Nicolaas F.

In: Journal of Electroanalytical Chemistry, 2006, vol. 560, no. 1, p. 47-56

New relations for and interrelations between the current responses of different microelectrode arrays are presented. Interdigitated microelectrode arrays (IDAs: alternating cathodes and anodes) and uniform microband electrode arrays (MEAs: only cathodes or anodes) are treated, and miniaturized systems with planar band electrodes or hemicylinder electrodes are discussed. A common basis was found...

Université de Neuchâtel

Influence of cationic and anionic additives on the electrical properties of ionophore-based ion-selective membranes

Morf, Werner E. ; de Rooij, Nicolaas F. ; Pretsch, Ernö

In: Journal of Electroanalytical Chemistry, 2005, vol. 581, no. 2, p. 265-274

The steady-state electrical behavior of cation-selective ionophore membranes with different kinds of ionic additives was studied on a theoretical basis. Membranes with both mobile and fixed anionic sites exhibit nonlinear current–voltage curves, which is in contrast with the ohmic behavior of pure fixed-site membranes. This can be explained from the specific concentration profiles in the...

Université de Neuchâtel

Current response of ion-selective solvent polymeric membranes at controlled potential

Sutter, Jolanda ; Morf, Werner E. ; de Rooij, Nicolaas F. ; Pretsch, Ernö

In: Journal of Electroanalytical Chemistry, 2004, vol. 571, no. 1, p. 27-35

From electrochemical measurements at the interface of two immiscible electrolytes, the current at controlled potential is usually a linear function of the ion concentration in the aqueous phase. Surprisingly, a linear relationship between the current and the logarithm of the sample ion activity is found for corresponding measurements on ion-selective electrode membranes. Here, a theoretical...

Université de Neuchâtel

Filling kinetics of liquids in nanochannels as narrow as 27 nm by capillary force

Han, Anpan ; Mondin, Giampietro ; Hegelbach, Nicole G. ; de Rooij, Nicolaas F. ; Staufer, Urs

In: Journal of Colloid and Interface Science, 2006, vol. 293, no. 1, p. 151-157

We report the filling kinetics of different liquids in nanofabricated capillaries with rectangular cross-section by capillary force. Three sets of channels with different geometry were employed for the experiments. The smallest dimension of the channel cross-section was respectively 27, 50, and 73 nm. Ethanol, isopropanol, water and binary mixtures of ethanol and water spontaneously filled...

Université de Neuchâtel

Heterogeneous oligonucleotide-hybridization assay based on hot electron-induced electrochemiluminescence of a rhodamine label at oxide-coated aluminum and silicon electrodes

Spehar-Deleze, Anna-Maria ; Suomi, Johanna ; Jiang, Qinghong ; de Rooij, Nicolaas F. ; Koudelka-Hep, Milena ; Kulmala, Sakari

In: Electrochimica Acta, 2006, vol. 51, no. 25, p. 5438-5444

This paper describes a heterogeneous oligonucleotide-hybridization assay based on hot electron-induced electrochemiluminescence (HECL) of a rhodamine label. Thin oxide-film coated aluminum and silicon electrodes were modified with an aminosilane layer and derivatized with short, 15-mer oligonucleotides via diisothiocyanate coupling. Target oligonucleotides were conjugated with...

Université de Neuchâtel

Computer simulation and theory of the diffusion- and flow-induced concentration dispersion in microfluidic devices and HPLC systems based on rectangular microchannels

Morf, Werner E. ; van der Wal, Peter D. ; de Rooij, Nicolaas F.

In: Analytica Chimica Acta, 2008, vol. 622, no. 1-2, p. 175-181

The dynamics of formation of solute peaks in microfluidic systems are investigated by computer simulation. A finite-element numerical procedure is applied to analyze the diffusion- and flow-controlled concentration dispersion in a 40 μm-high rectangular flow-through channel. Two-dimensional concentration profiles are shown for channels with cross sections of large aspect ratio. The final shapes...

Université de Neuchâtel

Optical, electrical and mechanical properties of the tantalum oxynitride thin films deposited by pulsing reactive gas sputtering

Le Dréo, H. ; Banakh, Oksana ; Keppner, Herbert ; Steinmann, P.-A. ; Briand, Danick ; de Rooij, Nicolaas F.

In: Thin Solid Films, 2006, vol. 515, no. 3, p. 952-956

Thin films of tantalum oxynitride were prepared by reactive magnetron sputtering using a Ta target and N2 and O2 as reactive gases. The nitrogen flow was kept constant while the oxygen flow was pulsed periodically. The film composition evolves progressively from TaO0.25N1.51 to TaO2.42N0.25 while increasing the oxygen pulse duty...