Abstract
Electrochemical impedance spectroscopy is finding increasing use in electrochemical sensors and biosensors, both in their characterisation, including during successive phases of sensor construction, and in application as a quantitative determination technique. Much of the published work continues to make little use of all the information that can be furnished by full physical modelling and analysis of the impedance spectra, and thus does not throw more than a superficial light on the processes occurring. Analysis is often restricted to estimating values of charge transfer resistances without interpretation and ignoring other electrical equivalent circuit components. In this article, the important basics of electrochemical impedance for electrochemical sensors and biosensors are presented, focussing on the necessary electrical circuit elements. This is followed by examples of its use in characterisation and in electroanalytical applications, at the same time demonstrating how fuller use can be made of the information obtained from complete modelling and analysis of the data in the spectra, the values of the circuit components and their physical meaning. The future outlook for electrochemical impedance in the sensing field is discussed.
Highlights
The development of electrochemical sensors and biosensors requires three essential steps, namely preparation, characterisation and testing, for applications in synthetic and natural samples
Of the former, the most use is made of atomic force microscopy and scanning electron microscopy, the surface analysis techniques that are used to examine the morphology of surface layers of materials in general
After a brief description of the fundamentals of Electrochemical impedance spectroscopy (EIS) which are necessary in order to be able to use the technique adequately for electrochemical sensor research, illustrative examples will be given, chosen to show what can be achieved by EIS as a characterisation technique and as a technique for quantitative determinations of electroactive species
Summary
The development of electrochemical sensors and biosensors requires three essential steps, namely preparation, characterisation and testing, for applications in synthetic and natural samples. The non-electrochemical techniques are normally those of surface analysis, microscopic and spectroscopic. Of the former, the most use is made of atomic force microscopy and scanning electron microscopy, the surface analysis techniques that are used to examine the morphology of surface layers of materials in general. Its widespread use before the 1980s, just as was the case for electrochemical pulse techniques, was hindered by the practical difficulties in applying the potential waveform to the electrodes in an accurate way and being able to analyse the response in a short time period. After a brief description of the fundamentals of EIS which are necessary in order to be able to use the technique adequately for electrochemical sensor research, illustrative examples will be given, chosen to show what can be achieved by EIS as a characterisation technique and as a technique for quantitative determinations of electroactive species.
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