Comparación de los procesos de estimulación del ligando 4 1BB en linfocitos B esplénicos.

Electrochemical Impedance Spectroscopy, EIS, employs the application of a.c. signals of selected frequencies and small amplitude (5-10 mV). By varying the frequency of the signal, a selective perturbation of different physic-chemical phenomena can be performed, thus allowing the identification of their separate contributions.

The response is usually interpreted in terms of equivalent circuit, i.e. the electrical circuit (a combination of electrical components connected in series/parallel) which gives the same response as the investigated real system. Each component represents a certain phenomenon (faradic resistance, solution resistance, double layer capacitance, etc.).

The impedance of an electrode or a battery is given by the following expression: (20)

where ଵ

ఠ ஼ , and ω is the angular frequency (2πf); L is the inductance andCthe capacitance.

The frequency of the maximum,

WhereRis related to the exchanged current for the reaction and capacitance

times larger than the double layer capacitance, interface.

Each electrode reaction has a distinctive, characteristic impedance signature. Usually, battery electrodes have large surface areas and, therefore, show large capacitances. It is common for cells to have a capacitance of far

milliohms

Impedance data are usually represented in the Nyquist plot (imaginary part of vs its real part,

representation plots can be used (e.g.

Figure 2.10

behaviour of the impedance cha

(Reprinted from reference The frequency of the maximum,

is related to the exchanged current for the reaction and capacitance Cp, usually of the

times larger than the double layer capacitance,

Each electrode reaction has a distinctive, characteristic impedance signature. Usually, battery electrodes have large surface areas and, therefore, show large capacitances. It is common for cells to have a capacitance of far

milliohms9.

Impedance data are usually represented in the Nyquist plot (imaginary part of its real part, Zreal) and the Bode plot (

representation plots can be used (e.g.

Figure 2.10 Simple battery circuit diagram (top); Corresponding Argand diagram of the behaviour of the impedance

characteristic behaviours of ohmic (Reprinted from reference

The frequency of the maximum,

is related to the exchanged current for the reaction and , usually of the order of the hundreds of μ

times larger than the double layer capacitance,

Each electrode reaction has a distinctive, characteristic impedance signature. Usually, battery electrodes have large surface areas and, therefore, show large capacitances. It is common for cells to have a capacitance of far

Impedance data are usually represented in the Nyquist plot (imaginary part of ) and the Bode plot (

representation plots can be used (e.g.

Simple battery circuit diagram (top); Corresponding Argand diagram of the behaviour of the impedance with frequency f for an idealis

racteristic behaviours of ohmic

(Reprinted from reference 11, Copyright (2002), with permission from ACS journals) The frequency of the maximum,fm, of the semicircle give

௠

is related to the exchanged current for the reaction and

order of the hundreds of μ

times larger than the double layer capacitance,

Each electrode reaction has a distinctive, characteristic impedance signature. Usually, battery electrodes have large surface areas and, therefore, show large capacitances. It is common for cells to have a capacitance of far

Impedance data are usually represented in the Nyquist plot (imaginary part of ) and the Bode plot (Z

representation plots can be used (e.g.Zrealand

Simple battery circuit diagram (top); Corresponding Argand diagram of the with frequency f for an idealis

racteristic behaviours of ohmic, activation and diffusion are

11, Copyright (2002), with permission from ACS journals)

Chapter 2.

, of the semicircle give (21)

is related to the exchanged current for the reaction and

order of the hundreds of μ

times larger than the double layer capacitance, C

Each electrode reaction has a distinctive, characteristic impedance signature. Usually, battery electrodes have large surface areas and, therefore, show large capacitances. It is common for cells to have a capacitance of far

Impedance data are usually represented in the Nyquist plot (imaginary part of Z modulus and

andZimvsω).

Simple battery circuit diagram (top); Corresponding Argand diagram of the with frequency f for an idealis

ivation and diffusion are

11, Copyright (2002), with permission from ACS journals)

Chapter 2. Characteri

, of the semicircle give the relaxation time:

is related to the exchanged current for the reaction and C

order of the hundreds of μF cm-1, which is almost ten CDL, at the

Each electrode reaction has a distinctive, characteristic impedance signature. Usually, battery electrodes have large surface areas and, therefore, show large capacitances. It is common for cells to have a capacitance of farad

Impedance data are usually represented in the Nyquist plot (imaginary part of

modulus and φ vs ω), but several other

ω).

Simple battery circuit diagram (top); Corresponding Argand diagram of the with frequency f for an idealised battery sy

ivation and diffusion are shown

11, Copyright (2002), with permission from ACS journals)

Characterisation Techniques

the relaxation time:

Cis the polaris , which is almost ten , at the electrode-

Each electrode reaction has a distinctive, characteristic impedance signature. Usually, battery electrodes have large surface areas and, therefore, show large ads and resistance of

Impedance data are usually represented in the Nyquist plot (imaginary part of

), but several other

Simple battery circuit diagram (top); Corresponding Argand diagram of the ed battery system where the

shown (bottom) 11, Copyright (2002), with permission from ACS journals)

ation Techniques

the relaxation time:

the polarisation , which is almost ten -solution

Each electrode reaction has a distinctive, characteristic impedance signature. Usually, battery electrodes have large surface areas and, therefore, show large s and resistance of

Impedance data are usually represented in the Nyquist plot (imaginary part of Z,Zim, ), but several other

Simple battery circuit diagram (top); Corresponding Argand diagram of the stem where the

(bottom). 11, Copyright (2002), with permission from ACS journals)

References

1. Cheetham , A.K. and Day, P. Solid State Chemistry Techniques Oxford University Press (1991).

2. Bragg, W.L. Proc.Camb. Phil. Soc.(1912)1743.

3. Bruker AXS ltd, TOPAS V3.0: General Profile and Structure Analysis Software for Powder Diffraction Data. 2004.

4. Reitveld, H.M.Acta Cryst., (1969)265.

5. Brunauer, S.; Emmett, P.H.; Teller, E.J. Am. Chem. Soc.(1938)60309. 6. Long, D.A., Raman Spectroscopy, McGraw-Hill International Book

Company 1977.

7. Hardwick, L.J.; Holzapfel, M.; Novak, P.; Dupont, L.; Baudrin, E. Electrochimica Acta(2007)525357–5367.

8. Ratner, B.; Castner, D.Electrospectroscopy for Chemical Analysis in Surface Analysis, Editor J.C. Vickerman, Wiley 1997.

9. Winter, M. and Brodd, R.J.Chem. Rev.(2004) 1044245-4269.

10. Vincent, C.A. and Scrosati, B. Modern Batteries, 2nd Edition, Arnold Publ. Ltd., London, 1997.

Chapter 3. Synthesis and Characterisation of TiO2(B) materials