Surface Functionalized Sensors for Humidity‐Independent Gas Detection

• Published in: Angewandte Chemie International Edition Vol. 60; no. 12; pp. 6561 - 6566
• Main Authors: Qu, Fengdong, Zhang, Shendan, Huang, Chaozhu, Guo, Xuyun, Zhu, Ye, Thomas, Tiju, Guo, Haichuan, Attfield, J. Paul, Yang, Minghui
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 15.03.2021
• Edition: International ed. in English
• Subjects: Gas sensors; Humidity; Hydrophobicity; Metal oxides; Metal-organic frameworks; Nanoparticles; Polymers; Relative humidity; Selectivity; semiconductors; Sensitivity; Sensors; hydrophobicity; nanoparticles; sensors; metal oxides; semiconductors; metal-organic frameworks
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.202015856

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.