Graphene as a sub-nanometer trans-electrode membrane

Isolated, atomically thin conducting membranes of graphite, called graphene, have recently been the subject of intense research with the hope that practical applications in fields ranging from electronics to energy science will emerge1. Here, we show that when immersed in ionic solution, a layer of graphene becomes a new electrochemical structure we call a trans-electrode. The trans-electrode's unique properties are the consequence of the atomic scale proximity of its two opposing liquid-solid interfaces together with graphene's well known in-plane conductivity. We show that several trans-electrode properties are revealed by ionic conductance measurements on a CVD grown graphene membrane that separates two aqueous ionic solutions. Although our membranes are only one to two atomic layers2,3 thick, we find they are remarkable ionic insulators with a very small stable conductance that depends on the ion species in solution. Electrical measurements on graphene membranes in which a single nanopore has been drilled show that the membrane's effective insulating thickness is less than one nanometer. This small effective thickness makes graphene an ideal substrate for very high-resolution, high throughput nanopore-based single molecule detectors. The sensitivity of graphene's in-plane electronic conductivity to its immediate surface environment, as influenced by trans-electrode potential, will offer new insights into atomic surface processes and sensor development opportunities.