Layered double hydroxides (LDHs) are a class of layered materials that show intercalant-dependent properties. Precise control over the type and concentration of intercalants in LDHs is important to tailor their properties and functions. Herein, through an anion exchange process, we partially replaced the NO3 2– ions in MgAl-LDH nanosheets with terephthalic acid (BDC) ions and systematically studied their ionic conduction and humidity sensing properties at different NO3 2–/BDC ratios. Our results show that moderate BDC intercalation boosted the humid sensing response to 3 orders of magnitude compared to the original MgAl-LDH intercalated with NO3 2– ions. This is because the BDC molecules could help improve the hydrophilicity of the LDH and thus the ability to absorb water molecules. However, too high a BDC concentration resulted in a considerable reduction in the ionic conduction of the LDH because this might block ionic conductive paths. As a demonstration, the MgAl-LDH-NO3 2–-BDC hybrid was fabricated into a flexible humidity sensor, which showed potential as a wearable breath sensor.

This work demonstrates introducing noble metal nanodots with suitable surface ligands in gas sensing materials is an effective way to improve their performance, and noble metal/metal oxide/rGO composites have potentials in flexible gas sensing.