# Host–Guest Chemistry as a Supramolecular Engine for Iontronic Transduction in Nanochannels

## TL;DR

This review explores how supramolecular host-guest chemistry can control ionic transport in nanochannels, enabling precise and tunable iontronic devices for sensing and separation.

## Contribution

The paper provides a comprehensive review of host-guest systems in nanochannels for iontronic transduction, emphasizing their tunable and stimulus-responsive behavior.

## Key findings

- Crown ether-based systems achieve biological-level Na+/K+ selectivity in nanochannels.
- Calixcrowns and pillararenes enable nanomolar-level ion detection in functionalized nanochannels.
- External stimuli like pH and temperature can reversibly switch conductive states in these systems.

## Abstract

Since the first synthetic macrocyclic receptors were shown to bind ions selectively, supramolecular host–guest chemistry has enabled the translation of molecular recognition events into physical signals. Early coupling of such receptors to ion-sensitive field-effect transistors established a bridge between supramolecular chemistry and solid-state electronics. Today, this bridge is rebuilt in iontronics, where ions carry information through nanoconfined media and ionic transport becomes highly sensitive to electrostatic gradients, surface charge, and surface molecular interactions. As a result, ionic flux can serve as an efficient transduction mechanism that responds precisely, reversibly, and rapidly to changes in the chemical environment. Within this regime, host–guest chemistry offers a powerful means to exert direct control over ionic behavior, allowing molecular recognition to modulate conductance, rectification, and ion selectivity, thereby conferring practical function to nanofluidic systems. This review highlights systems in which host molecules act as chemical actuators that modulate nanochannel surface chemistry, thereby regulating ionic flux and enabling reversible, tunable, and stimulus-responsive behaviors. We survey architectures in which crown ethers, calixcrowns, pillararenes, and related hosts are integrated into solid-state nanochannels, emphasizing representative achievements such as biological-level Na+/K+ selectivity in crown ether-based systems and nanomolar-level detection of ions using calixcrowns- and pillararene-functionalized nanochannels. Finally, we discuss how temperature, pH, light, and redox state act as external stimuli that reversibly switch between conductive states, yielding ion-selective platforms for sensing and ion sieving.