Graphene: A sub-nanometer trans-electrode membrane

TL;DR

This paper demonstrates that graphene membranes act as trans-electrodes with unique electrochemical properties, enabling high-resolution nanopore sensing and new insights into atomic-scale surface processes.

Contribution

It reveals graphene's trans-electrode behavior in ionic solutions and its potential for ultra-thin, high-resolution sensing applications.

Findings

Graphene acts as a trans-electrode with unique electrochemical properties.

The effective insulating thickness of graphene membranes is less than one nanometer.

Graphene's in-plane conductivity can be modulated by trans-electrode environments.

Abstract

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 emerge. Here, we show that when immersed in ionic solution, a layer of graphene takes on new electrochemical properties that make it a trans-electrode. The trans-electrode's 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 conductivity measurements on a CVD grown graphene membrane that separates two aqueous ionic solutions. Despite this membrane being only one to two atomic layers thick, we find it is a remarkable ionic insulator with a very small stable conductivity 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. Sensors based on modulation of graphene's in-plane electronic conductivity in response to trans-electrode environments and voltage biases will provide new insights into atomic processes at the electrode surfaces.