High-performance QCM humidity sensor based on graphene oxide/tin oxide/polyaniline ternary nanocomposite prepared by in-situ oxidative polymerization method

A quartz crystal microbalance (QCM)-based humidity sensor based on graphene oxide/tin dioxide/polyaniline (GO/SnO2/PANI) composite was fabricated by in-situ oxidative polymerization method. The morphological and compositional properties of the GO/SnO2/PANI nanocomposite sprayed on QCM were characterized by scanning electron microscopy (SEM), transmission electron microscopic (TEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), Fourier transform infrared spectrum (FT-IR) and X-ray photoelectron spectroscopy (XPS). The humidity-sensing properties of the GO/SnO2/PANI humidity sensor were investigated upon exposure to different relative humidity (RH) levels at room temperature. The experimental results confirmed that the GO/SnO2/PANI film-coated QCM sensor has a high sensitivity, good repeatability and short response/recovery time, which surpasses the previous reported counterparts. Moreover, the underlying humidity sensing mechanism of the sensor was attributed to the hydroxyl, carboxyl and epoxy functional groups attached on the GO nanosheets, the amino groups on PANI nanofibers, as well as surface vacancies and defects on SnO2 nanoparticles. The water molecules adsorption process on the QCM was discussed by using the Langmuir adsorption isotherm model. This work confirmed that the GO/SnO2/PANI nanocomposite is an excellent candidate for QCM sensor fabrication.