DISSERTATION

_____________________________________________________________ Results and Discussion
pulse assisted immobilization procedures, tailored for the specific molecule length, compact
SAMs can be obtained within minutes.
Figure 3.38. Coverage curves calculated from optimal capacitance curves for all three
thiol derivatives: MCH 0.5/-0.2 V (10 ms pulse duration), MCU 0.5/-0.2 V (10 ms pulse
duration), MCHD 0.5/-0.2 V (10 s pulse duration) according to Equation (3.9). Figure
adapted from ref. 89 .
It was previously reported that by applying constant potentials an acceleration of the SAM
formation kinetics of aliphatic thiols (C12-C14) can be achieved 21,92 . For example, Ma and
Lennox reported to obtain a complete chemisorption in only 15 min upon applying a constant
potential 13 . They assessed the SAM integrity by evaluating the blocking ability towards electron
transfer of a redox mediator and observed a full blocking of electron transfer for SAM formation
supported by applying constant potentials from 0.2 V up to even 1 V. The obtained result is
surprising since it is known that relatively high anodic potentials of above 600 mV induce Au-
S bond cleavage 19 . Nevertheless, for the purpose of comparison, our potential-assisted SAM
formation method was tested using this approach. A typical CV obtained by using the optimized
procedure for potential-assisted SAM formation of MCU is presented in Figure 3.39, where it
can be seen that a complete blocking of electron transfer is achieved already within seconds.
3.3 Importance of controlling the surface 77