The role of water vapour in ZnO nanostructures for humidity sensing at room temperature

•ZnO nanostructures (nanoparticles and nanorods) are evaluated as humidity sensors at room temperature.•Physico-chemical behaviour of the ZnO structures is exposed and discussed.•ZnO nanparticles shows inverse behaviour than ZnO nanorods under different RH atmospheres.•Promising results as RH sensor is observed for ZnO nanostructures. The role of water vapour in ZnO nanostructures for humidity sensing at room temperature is presented and discussed. Experimental and theoretical results demonstrate that ZnO nanoparticles and nanorods, show different physico-chemical behaviour under different relative humidity atmospheres. While electrical current density increases as RH does in the case of the ZnO nanoparticles, ZnO nanorods show inverse behaviour. These facts are related to the capillary condensation and water electric dipole moment effects, respectively. Additionally, a simultaneous validation between the sensor developed and a commercial device corroborates the potential application of this kind of low-cost sensing nanostructures presented in this work.