The rectification of mono- and bivalent ions in single conical nanopores

The polyethylene terephthalate (PET) films were irradiated with single 6.9 MeV/u ⁵⁸Ni¹⁹⁺ ions at the Lanzhou Interdisciplinary Heavy Ion Microbeam (LIHIM), and single conical nanopores were produced by asymmetric chemical etching of the latent ion tracks. Then, the current-voltage (I–V) characteristic was measured in LiCl, NaCl, KCl, MgCl₂, and CaCl₂ solution at different concentrations to study the transport properties of different cations in the single conical nanopores respectively. The measured I–V data showed that the conical nanopores have rectified transportation of these cations at the applied voltage of between +2 V and −2 V. The rectification coefficient γ of the mono- and bivalent ions was determined in their solution of 0.0001–1 M measured at 1 V, the result showed that the rectification coefficient is dependent on the valence of the ions and the electrolyte solution.