Experimental and simulation studies of unusual current blockade induced by translocation of small oxidized PEG through a single nanopore†
Detection of a single macromolecule based on the use of artificial nanopores is an attractive and promising field of research. In this work, we report a device based on a 5 nm single nanopore with a high length/diameter ratio, tailored by the track etching and atomic layer deposition techniques. The translocation of neutral polyethylene glycol (PEG) and charged polyethylene glycol-carboxylate (PEG-carboxylate) molecules of low molar masses (200 and 600 g mol−1) through this nanodevice was studied. It was shown that charged PEG-carboxylate molecules, which permeate through the pore, promote an unusual blockade of ionic current whereas the neutral PEG molecules do not show such behaviour. The molecular dynamics simulation shows that both neutral and charged PEGs permeate through the nanopore close to its inner surface. The main difference between the two macromolecules is the existence of a structured shell of cations around the charged PEG, which is likely to cause the observed unusual current blockade.