DISSERTATION

________________________________________________________________ Experimental Work
Figure 5.4. Scheme of the electrochemical setup used for determination of the pzc. The
implemented capacitive bridge (Cb) is shown in the figure. CE – counter electrode, RE –
reference electrode, WE – working electrode.
Determination of the pzc of the DNA modified surface was done by initially immobilizing
ssDNA (from 1 µM solution in 10 mM PB with 450 mM K2SO4) on a clean electrode surface
for 5 min via potential-assisted immobilization (0.5/-0.2 V (vs. Ag/AgCl/3 M KCl) following
a pulse profile with 10 ms pulse duration (procedure explained in detail in Section 5.7.2).
Afterwards the electrode was thoroughly rinsed with the immobilization buffer and water,
respectively to remove any loosely bound DNA strands, and placed in an appropriate solution
for pzc determination. PDEIS was performed for a potential range of -0.4 V to 0.5 V vs.
Ag/AgCl (3 M KCl) with 30 mV potential steps. EIS measurements for discrete potential values
were done as in the case of the bare electrode.
5.5 Potential-assisted formation of self-assembled monolayers
Preparation of gold electrodes for thiol self-assembling was done as explained in Chapter 5.3.
After characterization with EIS and CV (see Sections 5.9.1 and 5.9.2) gold electrodes were
immediately used for potential-assisted SAM formation of thiols of different length – MCH,
MCU and MCHD (1 mM in phosphate buffer, 20 mM K2SO4 with 30 % ethanol), using several
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