Measuring the double-layer capacitance of graphene devices in solution

Graphene, a two dimensional metal made from carbon, has been studied extensively as a sensor in biological systems. Biological systems produce voltages that can be detected by the graphene device. Effectively, the voltage creates a capacitance layer at the graphene/liquid interface, which then inhibits conduction through the graphene. When modeling this interaction, it is typical to assume the capacitive layer is identical to that in a liquid/metal interface. To test whether this is a valid assumption, the capacitance for a macroscopic system is compared to a graphene device for several concentrations of salt water. This work may prove important for studies of supercapacitors.