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(a) Schematic of an electrophoresis setup for DNA trapping. The DNA -SH-GCGCGCGC- is self-complementary. The sub-2 nm nanogap is exposed to DNA solution through a PMMA hole opening ( in diameter) and the rest of the device remains protected by the polymer. Applied bias was 1 V. is the series resistor to limit the electric field after the capture of one dsDNA to avoid multiple trapping events. (b) In situ monitoring of dsDNA trapping: two typical conductance vs time curves of DNA trapping (trapping 1 and 2 experiments are marked by triangles and squares, respectively). The step conductance increase indicates successful capturing of a dsDNA duplex.
characteristics of a dsDNA molecule in PBS buffer solution. The applied bias was from −200 to 200 mV at a ramp rate of 5 mV/50 ms. The inset at right corner is a schematic of dsDNA in a nanogap. Once a dsDNA molecule is trapped, the dsDNA is then immobilized to the nanogap electrode by thiol-gold bonding and formed a bridge between the nanogap so that it is possible to measure the conductance of the dsDNA in solution. Inset at the upper left corner: A histogram of dsDNA conductance measured from 15 samples.
characteristics of a DNA duplex in PBS buffer solution (triangle), de-ionized water (dot) and dehydrated state (star). Note that the data set of the dehydrated state overlaps with that of the de-ionized state.
In situ conductance measurement of the dsDNA upon melting. The applied bias is 0.1 V. A steplike conductance drop was observed due to denaturing of the DNA duplex structure.
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