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Potential and Current Density Distributions at Electrodes Intended for Bipolar Patterning
Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
Uppsala University.
Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
2009 (English)In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 81, no 1, 453-459 p.Article in journal (Refereed) Published
Abstract [en]

This paper deals with the use of reaction gradients on bipolar electrodes for the patterning of electrode surfaces. More specifically, the potential and current density distributions in two setups containing bipolar electrodes were investigated to optimize and design specific gradient geometries. Comparisons with simulations based on simple conductivity models showed a good qualitative agreement, demonstrating that these models could be used to predict bipolar behavior in more complex setups. In conjunction with imaging surface plasmon resonance (iSPR) experiments, the reaction gradients on bipolar electrodes could further be visualized. It was, for example, found that the gradient in potential difference was approximately linearly distributed in the center of the bipolar electrode and that these potential differences could be determined using an ordinary Ag/AgCl reference electrode. The present results thus provide a better understanding of the processes relevant for bipolar patterning. This approach was finally used to generate a circular gradient region in a self-assembled monolayer, thereby showing the possibilities to create interesting substrates for biosensors and microarray applications.

Place, publisher, year, edition, pages
2009. Vol. 81, no 1, 453-459 p.
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:liu:diva-16423DOI: 10.1021/ac801871cOAI: oai:DiVA.org:liu-16423DiVA: diva2:139586
Available from: 2009-01-23 Created: 2009-01-23 Last updated: 2017-12-14
In thesis
1. Electric Fields for Surface Design and Chemical Analysis
Open this publication in new window or tab >>Electric Fields for Surface Design and Chemical Analysis
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis deals with the use of electric fields for evaluation and control of chemical systems. An electric field can result in the flow of charge across an interface between a metal and a solution, by means of chemical reactions. This interplay between electricity and chemistry, i.e. electrochemistry, is a field of crucial importance both within research and industry. Applications based on electrochemical principles encompass such diverse areas as batteries and fuel cells, pH electrodes, and the glucose monitor used by people suffering from diabetes.A major part of the present work concerns the use of static electric fields in solutions containing a non-contacted metal surface. In such a setup it is possible to control the extent of electrochemical reactions at different positions on the metal. This allows the formation and evaluation of various types of gradients on electrodes, via indirectly induced electrochemical reactions. This approach is a new and simple way of forming for instance molecular gradients on conducting surfaces. These are very advantageous in biomimetic research, because a gradient contains a huge amount of discrete combinations of for example two molecules. The basis for the technique is the use of bipolar electrochemistry. Briefly, a surface can become a bipolar electrode (an electrode that acts as both anode and cathode) when the electric field in the solution exceeds a certain threshold value, thereby inducing redox reactions at both ends. In our experiments, the driving force for these reactions will vary along the electrode surface. Since the result of an electrochemical reaction can be the deposition or removal of material from an electrode, bipolar electrochemistry can be used to create gradients of that material on a surface. In order to gain a deeper understanding of these processes, the potential and current density distributions at bipolar electrodes were investigated with different methods. Especially the use of imaging techniques was important for the visualization and analysis of the gradients. Using this knowledge, the formation of more complex gradients was facilitated, and the results were further compared to simulations based on simple conductivity models. These simulations also provided us with means to predict the behavior of new and interesting setup geometries for pattering applications.The other major part is more application driven and deals with the use of alternating electric fields for chemical analysis, a technique known as electrochemical impedance spectroscopy (EIS). In this work, EIS has been applied for the analysis of engine oils and industrial cutting fluids. Emphasis was placed on practical aspects of the measurement procedure, and on the evaluation of the results using statistical methods. It was for example shown that it was possible to simultaneously determine the amount of different contaminants in low conducting solutions. Generally, EIS is used to measure the impedance of a solution or a solid, often as a function of the frequency of the alternating electric field. The impedance of a system is closely correlated to its complex dielectric constant, and EIS can therefor be used to examine many chemical and physical processes. It is further well suited for characterizing low conducting media with little or no redox-active species. The evaluation of impedance data is often a quite complex task, which is why we have made use of statistical methods that drastically reduce the effort and quickly reveal significant intrinsic parameters.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2008. 50 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1206
Keyword
Electric fields, Surface design, Chemical analysis, Bipolar electrodes, Impedance spectroscopy
National Category
Inorganic Chemistry Physical Chemistry Physical Chemistry Physical Chemistry
Identifiers
urn:nbn:se:liu:diva-12485 (URN)978-91-7393-819-8 (ISBN)
Public defence
2008-10-02, Planck, Fysikhuset, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2008-09-29 Created: 2008-09-08 Last updated: 2009-05-18Bibliographically approved

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Ulrich, ChristianAndersson, OlofBjörefors , Fredrik

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