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. (C) 2014 Elsevier B.V. All rights reserved.