The existence of the threshold voltage which can switch the rectification state of ions in nanochannels was firstly revealed by researchers from the Institute of Modern Physics (IMP). The result was published in ACS Applied Materials & Interfaces, on September 25. 

The characteristics and mechanism of ion transport in nanochannels form the basis for the study of cellular ion channels, ion rectification and nanofiltration. Lots of research has been conducted on ion transport regulated by the structure and surface modification of nanochannels. However, the impact of electric field on the nanochannel surface and ion transport is still unclear. 

By applying single ion irradiation technology of HIRFL high energy microbeam and the track etching method, researchers systematically studied the influence of electric field regulation on the surface charge and ion transport in single polyethylene terephthalate (PET) nanochannel. 

It is found that divalent and trivalent cations respectively have reversible and irreversible surface charge modification effects on the PET nanopore. When the threshold electric field is exceeded, the carboxyl-cation bond of the PET molecular chain on the pore surface breaks, which leads to the dissociation of cation and the rearrangement of the molecular chain on the pore surface, and the surface charge density and equivalent nanopore diameter change accordingly. 

These findings, which reveal the working mechanism of voltage-gated ion channel, provide a new perspective for ion rectification and filtration control in micro/nano channels, and have potential applications in ion separation, biomolecular detection and energy harvesting in nanochannels.　  

This work was supported by the Natural Science Foundation of China. 

Link to the article: https://pubs.acs.org/doi/abs/10.1021/acsami.9b13088 

Figure 1. Ionic rectification and the switch of dominant current carrier in single PET nanochannel depends on the ion concentration (Image by Yaning Li) 

Figure 2. Current-voltage measurement demonstrates that the nanochannel switched between two states of ion transport characteristics.(Image by Yaning Li) 

Contact :

LIU Fang

Institute of Modern Physics

Email: fangliu@impcas.ac.cn