Fig. 4
Impedance responses of different steps of probe-DNA attachment. Complex impedance plot at a DC bias of +0.25 V vs Ag/AgCl in 1 mM [Fe(CN)6]3−/4− + 0.1 M aqueous KCl solution for a different steps of probe-DNA attachment directly to the gold surface and b different steps of probe-DNA attachment to VASWCNTs on the gold surface. The frequency range is 100 kHz to 0.1 Hz with 5 mV rms signal. Solid lines are the fit to the experimental response using an appropriate equivalent circuit, which is shown as an inset of a. See the “Methods”/“Materials” section of the text for a more detailed discussion about the specific components of the equivalent circuit used here