Humidity-sensing properties of hierarchical ZnO/MWCNTs/ZnO nanocomposite film sensor based on electrostatic layer-by-layer self-assembly

This paper demonstrated a resistive-type humidity sensor with hierarchical ZnO/MWCNTs/ZnO nanocomposite film coated. Hydrothermally synthesized ZnO nanorods and functionalized multi-walled carbon nanotubes (MWCNTs) were utilized to construct a humidity sensor by using electrostatic layer-by-layer (ELbL) self-assembly technique. The characterization results including scanning electron microscope and X-ray diffraction confirmed the successful formation of as-prepared nanostructures. The electrical properties of the sensing films were investigated under different deposition time in the ELbL self-assembly process. The humidity sensing behaviors of the ZnO/MWCNTs/ZnO hierarchical hybrid film were investigated in a wide relative humidity (RH) range. It is found that the sensor exhibited an excellent linear response with RH, small hysteresis, acceptable repeatability and swift response-recovery characteristics. The possible sensing mechanism for the presented sensor was attributed to the nanostructure of ZnO/MWCNTs/ZnO and swelling effects between interlayers. This study provided a benchmark for humidity sensor fabrication using ELbL self-assembly technique.