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Long passage times of short ssDNA molecules through metallized nanopores fabricated by controlled breakdown

Abstract:

The fabrication of individual nanopores in metallized dielectric membranes using controlled breakdown directly in solution is described. Nanopores as small as 1.5-nm in diameter are fabricated in Au-coated silicon nitride membranes immersed in 1 M KCl by subjecting them to high electric fields. The physical and electrical characteristics of nanopores produced with this method are presented. The translocation of short single-stranded DNA molecules is demonstrated through such nanopore devices without further passivation of the metallic surface. Metallized nanopores can prolong the translocation times of 50-nt ssDNA fragments by as much as two orders of magnitude, while the slowest events can reach an average speed as slow as 2 nucleotides per millisecond. The mechanism for the long dwell-time distribution is differentiated from prior studies, which relied on friction to slow down DNA, and is attributed to nucleotide-Au interactions.