1. Electrochemical Impedance Spectroscopy Mr.Halavath Ramesh 16-MCH-001 Department of Chemistry Loyola College –Chennai. University of Madras

2. Introduction The term impedance refers to the frequency dependant resistances to current flow of a circuit element (resistor, capacitor,inductor.etc). Impedance assume an AC current of a specific frequency in Hertz(cycle/s). Impendence: Zw= Ew/Iw Ew= Frequency –dependant potential Iw= Frequency –dependant current. Ohm’s Law: R= E/I -R= Impedance at the limit of zero frequency. Impedances of common circuit elements change with applied frequency. We will take advantage of this relationship to determine different contributions to the overall cell impedance. Impedance apply a small AC(Frequency Domain) wave of changing frequency. V=iZ Impedance

3. FARADAIC IMPEDANCE Some of the best methods for studying the rate of electron transfer reactions involve a.c measurement of the faradic impedance the equivalent circuit parameter representing the barrier to current flow between electrode and solution. The faradic impedance includes both the finite rate of electron transfer and the rate of transport of electro active material to the electrode surface. In electrochemistry faradic impedance is the resistance and capacitance acting jointly at the surface of an electrode of an electrochemical cell.

13. Sinusoidal Voltage : A sinusoidal voltage sources is an alternator a generator that has a coil rotating in a magnetic field.

23. Software For Localized Electrochemical Impedance Spectroscopy

31. Impedance measurement System-Biological Materials A study by showed a temporary change in electrical impedance of biological cells after an application of high voltage pulse with very short duration. The result of the increase in conductivity due to 10 pulses at intervals of 3 seconds is measured. Time domain based impedance measurements were used to study the changes in electrical parameters of biological samples following the application of ultra-short high voltage (HV) pulses. Change in DC/AC voltage is 250,500, 750,1000 voltage for group 1,2,3 and 4 respectively. Impedance from Voltage and current signals The typical voltage waveform of the pulse as recorded by oscilloscope is shown on Fig. 2. From the waveform it can be seen that the voltage extremely increases at the beginning until reach maximum voltage and drop exponentially. At about 800 ns the voltage has more decrease of before steadily decreases

33. The maximum current when PEF occurs is shown in fig. 4 for various charging voltage.

36. Biological tissues belong to media that conduct the electric current Intercellular space and cell interior are ionic conductors and hence in general they are presented as resistive elements, whereas cell membranes, because of their structure, are presented as capacitive elements. Therefore, biological tissues are generally considered as objects of impeditive nature. The impeditive character of biological tissue causes electric current to be spread through tissues in a manner that is frequency dependent. It is commonly accepted that low frequency currents (of the order of kHz and below) flow mainly through the intercellular spaces whereas high frequency currents (hundreds of kHz, MHz) flow also through the cell membranes. Therefore, EIS can deliver information on the properties of various regions passed by currents of a given frequency. Diversification of the regions of different current flow provided by EIS makes it possible to evaluate the structure of the tissues being examined, e.g., the proportion between the intercellular space and the cell area (the state of cell membrane, etc.)