Nanodiamond/Ti 3 C 2 MXene‐coated quartz crystal microbalance humidity sensor with high sensitivity and high quality factor

Abstract To address the challenge of achieving both high sensitivity and a high quality factor in quartz crystal microbalance (QCM) humidity sensors, a nanodiamond (ND)/Ti 3 C 2 MXene composite‐coated QCM humidity sensor was fabricated. The material characteristics of ND, Ti 3 C 2 MXene, and ND/Ti 3 C 2 MXene composite were analyzed by transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy. The experimental results demonstrated that the hydrophilic ND nanoparticles coated on Ti 3 C 2 MXene nanosheet prevented the self‐stacking of Ti 3 C 2 MXene and enhanced the sensitivity of Ti 3 C 2 MXene‐based QCM humidity sensor. Moreover, the high mechanical modulus of Ti 3 C 2 MXene material helped ND/Ti 3 C 2 MXene composite‐coated QCM humidity sensor to achieve a high quality factor (> 20,000). ND/Ti 3 C 2 MXene composite‐coated QCM humidity sensor exhibited a sensitivity of 82.45 Hz/%RH, a humidity hysteresis of 1.1%RH, fast response/recovery times, acceptable repeatability, and good stability from 11.3%RH to 97.3%RH. The response mechanism of ND/Ti 3 C 2 MXene composite‐coated QCM humidity sensor was analyzed in combination with a bi‐exponential kinetic adsorption model. Finally, the potential application of ND/Ti 3 C 2 MXene composite‐coated QCM humidity sensor was demonstrated through its frequency response to wooden blocks with different moisture contents.