Impedance spectroscopy selected applications

The nature and mobility of ions and solvent in zeolite cages will affect the ac-impedance of the material. This effect can be utilized for zeolite-based sensor concepts where a zeolite film is coated on interdigitated electrodes. For example, it was shown that the impedance of a film of proton-conducting H-ZSM-5 is influenced by the presence of ammonia (Figs. 15, 16).[126,127] The ammonia is protonated in the zeolite, thus producing much larger ammonium ions with different mobilities in the zeolite that can be detected by impedance spectroscopy. The detection of ammonia is of interest for automotive applications where the selective catalytic reduction of NOx by ammonia is envisioned. 

There is a vast amount of literature on the subject of impedance measurements comprising a large number of different applications, such as corrosion, characterization of thin films and coatings, batteries, semiconductor electrodes, sensors, biological systems, and many more. It is beyond the scope of this article to cover all of these applications comprehensively. This chapter, therefore, concentrates on the description of the main principles and theories and selected applications of impedance methods. A more thorough treatment of the subject from the point of view of corrosion can be found in [1, 2], impedance spectroscopy of solid systems is described in [3]. The fundamentals of impedance spectroscopy of electrochemical systems are also explained in [4, 5]. 

In the previous sections, the impedance behavior of electrochemical cells was described, with a view of how kinetic parameters of electrochemical reactions or electrode properties such as the morphology might be extracted from an impedance spectrum. However, electrochemical impedance spectroscopy has been utilized for a vast number of applications and is not limited to mechanistic investigations of electrode reactions. A large number of studies have been dedicated to the investigation of coated electrode surfaces. In this chapter, a few selected examples will be given of how impedance spectra of coated electrodes can be evaluated and what information can be gained from them. 

This book is the third in the series Lecture Notes on Impedance Spectroscopy. It includes selected and extended contributions from the International Workshop on Impedance Spectroscopy (IWISTl). It is a set of presented contributions of world-class manuscripts describing state-of-the-art research in the field of impedance spectroscopy. It reports about new advances and different approaches in dealing with impedance spectroscopy including theory, methods and applications. The book is interesting for researchers and developers in the field of impedance spectroscopy. 

The next two chapters of this book section address the novel micro- and nanotechnologies impact in the field. Electroanalysis on board of microfluidics and lab-on-a-chip platforms is studied in Chapter 12 and selected nanoelectrochemistry applications for food analysis are covered in Chapter 13. To conclude this part. Chapter 14 deals with the principles and food applications using electrochemical impedance spectroscopy. 

Impedance measiuements are useful for resistive as well as for capacitive sensors. Analytes can affect the different components of the equivalence circuit in various ways. By impedance spectroscopy, i.e. by phase selective determination of the complex quantities, maximiun sensitivity and selectivity can be achieved. Impedance in this case is not the preferred method in fundamental research its greatest usefulness is in analytical applications. It is aimed at a cahbration curve as hnear as possible. 

While the practical application of IRMPD spectroscopy to mass-selected molecular ions had thus been shown, its widespread use as a structural tool in irai chemistry was impeded by the limited tunability of the CO2 laser and the absence of other useful laser sources featuring a high power and wide tunability across the IR spectrum. The interest in IRMPD spectroscopy of gaseous ions revived around the mm of the millennium, when IR free electron lasers (FELs) as well as novel high pulse-energy OPOs were coupled with ion storage tandem mass spectrometers. 

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