The nanoscopic principles of capacitive ion sensing interfaces.

Herein we discuss the operational principles of molecular interfaces that specifically recruit ions from an electrolyte solution and report this in a reagentless capacitive manner. At low ionic occupancy the response of the interface obeys a Debye-type phenomenon akin to classic "image charge" effects. At higher levels of occupancy, the response follows Thomas-Fermi screening and, significantly, is dependent on the electronic structure of the mesoscopic ion-receptor host-guest ensemble.