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Free-standing nanocrystalline graphite (NCG) membranes directly grew on SiN x substrates with the aid of the catalyst-free chemical vapor deposition method. A new type of NCG nanopore was formed in the NCG membrane via controlled dielectric breakdown in KCl electrolyte. The electrical properties, especially the ionic conductance of the NCG nanoporewere examined under different physical parameters (pore size, ion strength, and pH condition). Due to their impressive transport properties, we first realized DNA sensing using the NCG nanopores. [Display omitted] • A nanopore was formed in a free-standing nanocrystalline graphite 2D membrane via controlled dielectric breakdown. • Nonlinear but symmetric I–V curves of the NCG nanopore indicate the existence of internal electrostatic potential. • DNA translocation caused stochastic upward current pulses. • The dsDNA translocation speed was slowed down compared to other nanopores. [ABSTRACT FROM AUTHOR]

With the advantages of simple equipment and in-situ preparation of nanopores, the CBD method has been widely concerned by researchers. In this work, a fluorescence platform was set up to directly observe the λ-DNA motions near the CBD prepared different kinds of SiN x nanopores. At first, for the one nanopore film, the λ-DNA post-translocation motion was observed. Then, for the multiple nanopores film, the current modulation phenomena of each nanopore after the DNA clogged the pores was observed. When the distance of asymmetric pores is less than the length of λ-DNA, the larger nanopores are easy to be blocked preferentially by considering the tug-of-war on λ-DNA; when the asymmetric porous distance is larger than the DNA two polymer length, due to the forming a folded structure, the smaller nanopores are preferentially blocked. These results reveal that the clogging phenomena during the DNA translocation analysis for the nanopores are varied, and it should be considered for CBD-prepared nanopores. A fluorescence platform was set up to directly observe the λ-DNA motions near the CBD prepared different kinds of SiNx nanopores and reveals the clogging phenomena during the DNA translocation analysis for the nanopores. [Display omitted] • CBD prepared different kinds of SiNx nanopores. • directly observe the λ-DNA motions near nanopores. • the clogging phenomena during the DNA translocation analysis. [ABSTRACT FROM AUTHOR]