A facile PDMS coating approach to room-temperature gas sensors with high humidity resistance and long-term stability

The interference from relative humidity (RH) poses a critical issue for the practical application of room-temperature gas sensors. We demonstrate herein coating gas sensors with a hydrophobic polydimethylsiloxane (PDMS) layer can significantly enhance their humidity resistance. Pd nanoparticles (NPs) decorated TiO2 nanotubes (Pd/TiO2 NTs) is selected as a typical room-temperature gas sensor. By a simple thermal evaporation process, a conformal PDMS layer can be coated on the nanostructured sensing material. PDMS layer not only endows the sensor with a hydrophobic surface to water droplet, but also has a sufficient thickness to effectively prevent the penetration of water molecules. In contrast, other hydrophobic modification layer (such as silane coupling agent) can only make gas sensors superhydrophobic but not able to enhance their humidity resistance. Additionally, PDMS layer improves the long-term stability of Pd/TiO2 NTs sensors through affording protection of Pd NPs on the surface of gas sensors. Furthermore, PDMS layer is stable enough to resist the degradation during long-term usage. The PDMS coating strategy is simple and can be applied to gas sensors with various morphologies, which promotes the real applications of room-temperature gas sensors in moist environments.