Enhanced humidity-sensing response of metal oxide coated carbon nanotube

In this study, carbon nanotube (CNT)-yarn humidity sensors were fabricated using either a MnO2-coated CNT yarn or a pure CNT yarn as the sensing material. The results of this study showed that an increase in humidity causes a decrease in the hole density of p-type nanotubes, which in turn results in an increase in the resistance of the sensors. Here, the MnO2-coated sensor showed better sensitivity than the uncoated sensor. Active MnO2 coated on a CNT yarn serves as a catalyst for promoting charge transfer between the H2O molecules and the CNTs by forming a p-n heterojunction; this charge transfer plays an important role in realizing a composite sensor with high sensitivity. Further, these CNT-yarn sensors are flexible, bendable, and durable. These sensors can also be used as gas and vapor sensors, as well as for the construction of flexible sensing materials.