Mimicking how plants control CO2 influx: CO2 activation of ion current rectification in nanochannels

Abstract

One of the key processes of photosynthesis is to control the influx of atmospheric carbon dioxide (CO2). Ion channels fulfill this process by regulating the opening and closing of stomatal pores in plants leaves. Inspired by this natural process, we have developed an amidine-modified gas-responsive system that closely mimics stomatal pores: CO2 rather than the variation in the pH value directly modulates the conductance state of the channel. The CO2-activated chemical reaction of amidine groups is reversible and produces an excess surface charge on the pore walls of asymmetric nanochannels, which makes the ions pass preferentially through the nanochannels in one direction relative to the conductance in the other direction, resulting in a significant ion current rectification. Furthermore, the influence of the different molecular conformation of the amidine-containing molecules on the current is investigated and discussed. The conclusive simulation of our system based on the Poisson and Nernst Planck (PNP) model is also in good agreement with the experimental results. Accordingly, we have successfully mimicked the mechanism of stomatal closure in plants with our gas-activated nanosystem.