Humidity Sensing Properties of Metal Organic Framework-Derived Hollow Ball-Like TiO2 Coated QCM Sensor

This paper demonstrates three kinds of TiO2 with hollow hall, nanosphere, and nanoflower nanostructures coated quartz crystal microbalance (QCM) humidity sensors, which were synthesized by metal organic framework (MOF)-derived, hydrothermal and solvothermal route. The compositional and morphological characteristics of three kinds of TiO2 nanostructures were characterized by means of X-ray diffraction, specific surface area analysis, scanning electron microscopy, and water contact angle measurement. We found that the surface structure plays a crucial role in the humidity-sensing response properties of QCM sensors. The humidity sensing experiment was performed at room temperature. The MOF-derived hollow hall-like TiO2 coated QCM sensor exhibited excellent humidity sensing characteristics over a wide RH range (0%-97%RH), such as high sensitivity (33.8 Hz/%RH), good repeatability, and short dynamic response/recovery times (5 s/2 s). In addition, Langmuir adsorption model was developed to explain the humidity-sensing properties of the TiO2-based QCM sensor. This paper proves that MOF-derived hollow-ball TiO2 is a potential candidate nanomaterial for humidity sensor fabrication.