Graphene-based ion rectifier using macroscale geometric asymmetry

Ion rectification is the asymmetrical conduction of ions through a system under different polarities of applied potentials. In this article we report the finding of a novel form of ion rectification in graphene oxide (GO) and reduced graphene oxide (RGO) films which act as an ensemble array of nanochannels. Rectification is imparted by introducing geometric asymmetry in fluidic inlets to the counter-ion selective nanochannels of GO/RGO which creates asymmetry in the enrichment/depletion effects at the macro-/nano-interface. The devices are made simply by cutting a GO or RGO film into a trapezoid and sealing the film within a Polydimethylsiloxane block so that fluid may only enter through one of two inlets. These devices exhibit rectification ratios larger than 20 (in 1 mM NaCl) while operating at modest voltages [−1 V, +1 V].