Enhancing the rectification efficiency by changing ion species and introducing concentration gradients

Synthetic nanopores with ion selectivity have transport characteristics similar to biological ion channels and semiconductor electron devices. For example, conical nanopores with fixed surface charge and small openings have rectification properties, which depend on the surface charge density and can be regulated by surface chemical modification. Here we show a simple and effective method to significantly enhance the rectification ratio by changing the ion species and introducing concentration gradient across the nanopores. The experimental results show that the rectification ratio (Q=I-/I+) of a 100nm nanopore in polyimide film without chemical modification approaches 50 in KF solution with the electrolyte concentration on each side of the membrane is 1mM and 300mM, respectively.