Surface Functionalized Sensors for Humidity‐Independent Gas Detection

Semiconducting metal oxides (SMOXs) are used widely for gas sensors. However, the effect of ambient humidity on the baseline and sensitivity of the chemiresistors is still a largely unsolved problem, reducing sensor accuracy and causing complications for sensor calibrations. Presented here is a general strategy to overcome water‐sensitivity issues by coating SMOXs with a hydrophobic polymer separated by a metal–organic framework (MOF) layer that preserves the SMOX surface and serves a gas‐selective function. Sensor devices using these nanoparticles display near‐constant responses even when humidity is varied across a wide range [0–90 % relative humidity (RH)]. Furthermore, the sensor delivers notable performance below 20 % RH whereas other water‐resistance strategies typically fail. Selectivity enhancement and humidity‐independent sensitivity are concomitantly achieved using this approach. The reported tandem coating strategy is expected to be relevant for a wide range of SMOXs, leading to a new generation of gas sensors with excellent humidity‐resistant performance. A surface functionalization strategy, utilizing Co‐MOF/PDMS as tandem coating layers, was proposed to overcome the problem of humidity sensitivity for semiconducting metal‐oxide‐based gas sensors. This approach can be extended to various humidity‐independent gas‐sensing materials.