Enhanced humidity-sensing properties of novel graphene oxide/zinc oxide nanoparticles layered thin film QCM sensor

• Graphene oxide/zinc oxide layered film was first proposed for humidity sensing.
• Synergistic effect between GO and ZnO nanoparticles was observed and discussed.
• High sensitivity, rapid response/recovery and stable repeatability were obtained.
• Humidity-sensing models were built and discussed.

In this letter, a novel graphene oxide (GO, top layer)/zinc oxide nanoparticles (ZnO, bottom layer) layered thin film was sprayed on quartz crystal microbalance (QCM) for humidity detection within the range of 11.3% RH and 97.3% RH. A remarkable enhancement in sensitivity (41.10 Hz/%RH) of GO/ZnO sensor was achieved, compared with that of ZnO/GO sensor (25.11 Hz/%RH) and single film sensors (8.85 Hz/%RH for ZnO and 16.67 Hz/%RH for GO). Meanwhile, the resultant GO/ZnO sensor also exhibited rapid response/recovery rates (less than 9 s/5 s @63.2%) and stable repeatability. Based on morphological and structural analyses, it was speculated that the superior humidity-sensing properties of GO/ZnO sensor might be ascribed to the supporting role of ZnO layer, the smallest nanoparticles aggregation size and the higher mechanical modules.