Electrochemical Impedance Spectroscopy in the Characterisation and Application of Modified Electrodes for Electrochemical Sensors and Biosensors

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.

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“…The easiest circuit able to fit the EIS experimental data is reported in the inset of Figure 6 a. The latter is an adapted form of the Debye circuit which results from the parallel of an ionic resistance (R1) in series with a double layer capacitance (Q1) at the electrode surface and a dielectric capacitance (C1) [ 75 , 76 ].…”

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“…Electrochemical impedance spectroscopy (EIS) is one of the most important electrochemical techniques for interrogating surface chemistries which can be applied to detecting interfacial binding events through impedance measurements (in ohms). EIS has advantages over other electrochemical methods, such as that it is a steady-state technique, uses small signal analysis, and that it can investigate signal relaxation over a very wide range of applied frequencies with commercial usage [ 44 , 45 ]. On the other hand, EIS can be applied for assessing the electrical characteristics of nanomaterials, detecting and investigating the behavior of the electrode surface by delivering a sinusoidal voltage across a wide frequency range, and measuring the current with the least negative impact [ 46 ].…”

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