Figure 3.

Schematic representation of the electrode/electrolyte interface. The first layer in contact with the gold electrode is the ssDNA self-assembled monolayer, modelled as a capacitance C_ssDNA. Then we have the ions present in solution that arrange in response to the gold and DNA charges forming the so-called double layer capacitance C_DL, in series with C_ssDNA. When hybridization occurs, the binding of the complementary strand will produce a change in capacitance due to height changes, substitution of water molecules in the biological layer, and changes in the electrical charge density. The capacitance, extracted from the impedance measured in our electrochemical setup, is plotted versus time for the ssDNA-functionalized electrode (red curve) and for the mismatched (green) and perfectly matching (blue) complementary sequences.