Tunable Ion Conductivity in Defect-Controlled Graphene Nanochannels

Abstract

Many novel transport phenomena are observed in graphene nanochannels with ultrahigh surface flatness and nano- or sub-nanoscale constraints. Two critical physical parameters, surface slip length, and surface charge, play a vital role in the channel transport process. However, effectively controlling these parameters under such tight constraints remains a significant challenge. Here, it is developed a novel method that combines oxygen ion etching and layer-by-layer assembly of 2D material, to prepare graphene nanochannels. During the assembly process, defects are introduced into the graphene surface via oxygen ion etching. A significantly higher conductivity is observed for the pristine graphene channels compared to those with defects on both the upper and lower surfaces. Consistent with this observation, the conductivity of graphene channels with defects on only one surface falls between the two aforementioned values. Combined with theoretical analysis, the conductivity difference is attributed to the surface slip inhibition due to the introduced defects, and the change of surface charge, both caused by oxygen ion etching. By introducing defects, a new method is uncovered for fine-tuning ion transport in graphene nanochannels.