The Xue Jianming research group and collaborators of the School of Physics have made important progress in the study of tunable ion-selective nanochannels based on ion beam preparation

Ion-selective artificial nanochannels are widely used in seawater desalination, ion screening and nanofluid devices, and have become one of the international research frontiers in the field of
nanochannels in recent years.
Because different application scenarios require nanochannel devices with different ion screening capabilities, researchers have long needed to prepare corresponding ion-selective channels according to specific requirements, which requires a lot of time and resources and is limited
by experimental techniques.
Although some nanochannels with tunable ion selectivity have been reported in the work, they are actually several devices with different structures and fixed performance, so the study and preparation of truly tunable ion-selective nanochannels is still scarce
.

In view of the above challenges, Professor Xue Jianming's research group of the Institute of Heavy Ion Physics and the State Key Laboratory of Nuclear Physics and Nuclear Technology, School of Physics, Peking University, and Du Guanghua, a researcher at the Institute of Modern Physics of the Chinese Academy of Sciences, successfully prepared high-quality graphene sub-nanopores by ion beam irradiation, and further designed and prepared a multi-functional graphene heterochannel consisting of graphene sub-nanopores and tapered polyethylene terephthalate nanochannels (Figure 1).

。 This channel exhibits different ion selectivity at different applied voltages and has the potential not only as an efficient primary/divalent ion screening device, but also as an excellent biomimetic ion channel with cationic valence sensitive nanofluid diodes (Figure 2).

The ion selectivity of the graphene heterochannel originated from the negatively charged graphene sub-nanopores, and further combined with computational simulations, it was found that its equivalent charge density was affected by the voltage-dependent ion enrichment/depletion effect of the channel
internally.
The rectifier effect of the channel on the opposite of monovalent and divalent ions is caused by differences in diffusion currents caused
by different ion concentration gradients.
The foregoing work provides new ideas for the construction of similar multifunctional heterogeneous nanochannels with tunable ion selectivity, opening up this emerging research field that is expected to quickly meet the different needs
of complex and variable situations in practical applications.

Figure 1.
Graphene heterochannel structure schematic with graphene subnanoporous scanning transmission electron microscopy images

Figure 2.
Graphene heterogeneous nanochannels have voltage-adjustable ion selectivity

On August 19, 2022, the research results were published online in Nature Communications under the title of "Multifunctional graphene heterogeneous nanochannel with voltage-tunable ionselectivity".

。 Su Shihao, a 2018 doctoral candidate at the School of Physics, Peking University, and Zhang Yifan, a 2017 doctoral candidate, are co-first authors; Xue Jianming and Du Guanghua are co-corresponding authors; Other collaborators include Yao Huijun, a researcher at the Institute of Modern Physics of the
Chinese Academy of Sciences.

The above research work is supported
by the National Natural Science Foundation of China, the Special Topic of Science Challenges, the Institute of Modern Physics of the Chinese Academy of Sciences, the Electron Microscopy Laboratory of Peking University, and the High Performance Computing Platform of Peking University.