A Novel Fabrication of 3.6 nm High Graphene Nanochannels for Ultrafast Ion Transport

Graphene-based 2D nanochannels of 3.6, 10, and 50 nm heights and a 2μm width with rectangular shapes were fabricated for the first time, and their ion transport properties were reported. The fabrication options of nanochannel inscription and the novel technique of graphene conformal coating altogether enabled to create graphitic nanoconfinements with no limitation to particular nanomaterials, such as carbon nanotube, thereby leading to diversified investigation of the unique nanofluidic phenomena in the graphitic environment. Thus, prepared 3.6 nm high graphene nanochannels take a clean and smooth surface and show ionic conductance =115 times larger than that in the SiO₂/Si nanochannels. As the ion concentration increases, the Debye length decreases to become smaller than the channel height, augmenting electroosmotic ion transport and plug flow. Therefore, as the ion concentration and channel size increase, so does the ionic conductance. In the case of the hydrophilic surface, there is the immobile stern layer having a zero slip length. On the other hand, the hydrophilic SiO₂ channels having small slip length present low ion transport rate. In addition, the potential surface effects due to the substrate can affect fluid velocity and ion transport through the nanochannel.