Squeezing ionic liquids through nanopores.

Room temperature ionic liquids (RTILs) are substances composed entirely of ions and are liquids at or below 100 degrees C. Ionic conductivity of RTIL is one of the most important physical properties of these unique substances that determine their potential applications as a new medium for capacitors, fuel and solar cells as well as in separation systems. The quality of performance of these devices relies on the understanding of ionic transport of RTIL on a nanoscale. In this letter, we use ionic current carried by RTILs in single nanopores as a probe for their nanoscale transport properties. We show that the conductivity of RTILs through nanopores is significantly less than corresponding bulk values. Our experiments allowed us to address the nature of the interaction of these confined RTILs with charged surfaces. Electrostatic interactions of RTILs with nanopores are the basis for the formation of ionic diodes rectifying transport of the constituent ions.