DISSERTATION

________________________________________________________________ Experimental Work
pulse profiles: 0.3/-0.1 V, 0.5/-0.2 V and 0.5/-0.4 V (vs. Ag/AgCl/3 M KCl) with various pulse
durations of 1 ms, 10 ms, 100 ms and 10 s.
Real-time impedance measurements were performed during potential-assisted SAM formation
to investigate the kinetics of self-assembly. This was done in a way that the applied pulse
profiles were considered as DC potentials which were superimposed with an AC signal of 1
kHz frequency and 5 mVrms amplitude. Experiments were performed using a setup that
consisted of a potentiostat with a summing amplifier (IPS AJ, Germany), a function generator
(Agilent 33120A, USA), a lock-in amplifier (EG&G Instruments 7265 DSP, USA) and a 16 bit
CIO-DAS 1602/16 AD/DA board (Plug-In electronic, Germany).
Determination of the capacitance was done by calculating initially the imaginary impedance
component (-Z'') using the recorded magnitude (|Z|) and phase (θ) values:
|Z| =
A AC
k|Z| meas
(5.5)
−Z ′′ = |Z|sinθ
where AAC is AC amplitude, k is the correction coefficient taking into account the current range
of the potentiostat (10 mA/10 V) and |Z|meas is the measured value of the magnitude. Using the
value of the imaginary impedance component the capacitance was calculated using the
following expression, derived from an RC series equivalent electrical circuit:
C = −1
ωZ ′′ (5.6)
Data sampling was done at a rate of 100 ms per data point and recorded with a home-made
software. Oscillations of the recorded signals coming from the applied pulse potential were
suppressed by applying a digital filter to the experimental plots. Data analysis and curve fitting
was performed with Origin.
5.6 Potential-assisted desorption
Potential-assisted desorption was performed using ssDNA-, MCU- or ssDNA/MCU-modified
electrodes. The experiment was done in 10 mM PB with 450 mM K2SO4 by applying a 0.9/-0.9
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