DISSERTATION
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_____________________________________________________________ Results and Discussion<br />
3.3.3 Reproducible recycling of Au modified surfaces within seconds<br />
Parts of this section are in the manuscript that is in preparation: “Fully potential-controlled<br />
preparation of DNA chips” with coauthors: D. Jambrec, Y. U. Kayran and W. Schuhmann.<br />
Electrochemical SAM desorption has a wide range of applications including cleaning of gold<br />
electrodes to allow reusability of the surface (i.e. sensor recycling) 18 or modifying surface<br />
wettability and fabrication of mixed SAM layers 96,97 . The interest for electrochemical<br />
desorption of SAMs in this thesis is the development of a very fast and efficient desorption<br />
approach that allows cleaning of individual electrodes on a chip prior to their modification with<br />
appropriate DNA strands. Since DNA and alkylthiols that are used for surface modification<br />
have different anchoring molecules, where alkylthiols form only a single Au-S bond and the<br />
DNA forms six bonds Au-S from three disulfides within the anchoring site (see Section 3.4.1),<br />
we tested the efficiency of the developed potential pulse-assisted desorption approach on both<br />
types of molecules.<br />
Figure 3.41. Removal of DNA from the electrode surface (2 mm gold electrode). a) EIS<br />
and b) CV were used for the characterization of the surface at each step. DNA<br />
immobilization: incubation for 2 min in 1 µM DNA solution (10 mM PB, 450 mM K2SO4).<br />
Potential pulse-desorption: 0.9/-0.9 V vs. Ag/AgCl/3 M KCl, 10 ms pulse duration, 30 s.<br />
Measurements were performed in 10 mM PB, 20 mM K2SO4 containing 5 mM of<br />
K3[Fe(CN)6] and K4[Fe(CN)6]; CV at 100 mV/s scan rate.<br />
3.3 Importance of controlling the surface 81