Investigation of Electrokinetic Ion Transport in Self-Assembled Graphene Oxide Nanochannels*

This study investigates a two-dimensional material - graphene oxide (GO), identifies the structure of the GO nanochannels, and focuses on the analysis of ionized electrokinetic transport in the nanochannels. We begin with the discussion on the dissociated functional groups about the GO. In conjunction with the number of dissociated functional groups and the electric double layer theory, surface charge density and the distribution of ions in the GO nanochannels can be obtained. Second, we proposed a self-assembled GO nanochannel. We controlled the height of the nanochannels during fabrication and measured the conductance of the nanochannels under different concentrations of potassium chloride aqueous solution and hydrochloric acid.  We inferred that proton hopping benefits from the organized hydrogen-bond network due to the presence of structured water and functional groups, yielding higher proton mobility in the GO nanochannels. Slip-enhanced conductance from electrosmosis in the GO nanochannels becomes significant at high surface charge density. Through this study, the behavior of fluids in the GO nanochannels can be more clearly revealed.