High Sensitivity and High Stability QCM Humidity Sensors Based on Polydopamine Coated Cellulose Nanocrystals/Graphene Oxide Nanocomposite.

In this paper, a high sensitivity and high stability quartz crystal microbalance (QCM) humidity sensor using polydopamine (PDA) coated cellulose nanocrystal (CNC)/graphene oxide (GO) (PDA@CNC/GO) nanocomposite as sensitive material is demonstrated. The PDA@CNC was prepared by the self-polymerization action on the surface of CNC, and it acted as filler material to form functional nanocomposite with GO. The material characteristics of PDA@CNC, CNC/GO and PDA@CNC/GO were analyzed by transmission electron microscope (TEM) and Fourier transform infrared spectroscopy (FTIR), respectively. The experimental results show that the introduction of PDA@CNC into GO film not only effectively enhanced the sensitivity of GO-based nanocomposite-coated QCM sensor but also significantly maintained high stability in the entire humidity range. The PDA@CNC/GO30-coated QCM humidity sensor exhibited a superior response sensitivity up to 54.66 Hz/% relative humidity (RH), while the change rate of dynamic resistance of the sensor in the humidity range of 11.3-97.3% RH is only 14% that is much smaller than that of CNC/GO-coated QCM. Besides, the effect of the PDA@CNC content on the sensitivity and stability of GO-based nanocomposite-coated QCM humidity was also studied. Moreover, other performances of PDA@CNC/GO-coated QCM humidity sensor, including humidity hysteresis, fast response and recovery and long-term stability, were systematically investigated. This work suggests that PDA@CNC/GO nanocomposite is a promising candidate material for realizing high sensitivity and high stability QCM humidity sensor in the entire humidity detection range.