A Facile Approach to Fabricate QCM Humidity Sensor Based on Molybdenum Disulfide/Cellulose Nanocrystal Thin Film

In this article, molybdenum disulfide (MoS<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>)/cellulose nanocrystal (CNC) nanocomposites are coated on silver electrodes of the quartz crystal microbalance (QCM) by the drop-coating method for humidity sensing. The performance of QCM humidity sensors of MoS<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>, CNC, and MoS<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>/CNC thin films is investigated in the relative humidity (RH) range of 11.31%–97.59%. The experimental results reveal that MoS<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>/CNC humidity sensor has high sensitivity (ca. 36.03 Hz/%RH), which is higher than CNC (ca. 1.25 times) and MoS<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (ca. 2.5 times). Meanwhile, the sensor has excellent repeatability, high stability, and low humidity hysteresis (ca. 3.3%RH). Moreover, the Langmuir isotherm adsorption model is also used to investigate the humidity-sensitive mechanism of MoS<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>/CNC humidity sensors. In addition, MoS<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>/CNC humidity sensor can be well applicable for respiration monitoring which has good application prospect.