Fabrication and characterization of layer-by-layer nano self-assembled ZnO nanorods/carbon nanotube film sensor for ethanol gas sensing application at room temperature

This paper reported a ZnO/multi-wall carbon nanotubes (MWNTs) film-based sensor for ethanol gas detection. The film sensor was fabricated on a printed circuit board with interdigital electrodes microstructure. ZnO and MWNTs were utilized to form a hierarchical nanostructure using layer-by-layer self-assembly technique. The ZnO/MWNTs nanocomposites were characterized by scanning electron microscope and X-ray diffraction. The ethanol gas sensing properties of the presented sensor, such as the sensitivity, response-recovery characteristics and repeatability, were investigated by exposing to different concentration of ethanol gas varying from 5 to 500 ppm at room temperature. Comparisons were made with the drop-casted ZnO and layer-by-layer self-assembled ZnO/PSS film sensors under the same design, substrate and experiment conditions. As a result, the ZnO/MWNTs film sensor exhibited outstanding sensitivity, prompt response-recovery time and good repeatability, which outstripped that of the other two sensors. Furthermore, the normalized response of the sensor as a function of ethanol gas concentration was shown in this work, and the possible sensing mechanism of the above mentioned sensor was discussed in detail. This work highlights the unique superiority of layer-by-layer self-assembled ZnO/MWNTs film for constructing ethanol gas sensors.