DISSERTATION

________________________________________________________________ Experimental Work
was isolated with a shrink-tube. PbF2 was electrochemically deposited on the lead wire in a 0.5
NaF solution by cyclic voltammetry (Figure 5.1, a). During the first scan the potential was
initially decreased to negative values in order to remove the native oxide from the surface of
the lead wire and by this improve the deposition of lead fluoride. The deposition was done for
20 cycles at a scan rate of 20 mV/s. After deposition the electrode was kept in the same solution
and chronoamperometry was performed for 2 h at 0.2 V vs. Ag/AgCl (3 M KCl) in order to
improve the stability of the deposited PbF2 film. Finally, the lead wire with deposited PbF2 was
inserted in the prepared pipette and fixed (Figure 5.1, b). The prepared electrode was usually
left overnight to assure stabilization of the electrode potential. The electrode potential was
controlled before use and it was around -600 mV vs. Ag/AgCl (3 M KCl).
5.3 Preparation of gold surfaces
Figure 5.2. Home-made polishing machine.
Polycrystalline gold electrodes were mechanically and electrochemically cleaned before each
experiment in the following manner. Electrodes were mechanically polished using a homemade
automatic polishing machine built by Dr. Kirill Sliozberg (Figure 5.2). The polishing
machine consisted of a rotating disk covered with an appropriate polishing cloth and a holder
for two electrodes that was simultaneously moved in x direction keeping the electrodes
perpendicular to the surface of the rotating disk. By this polishing was performed in all
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