Quartz Crystal Microbalance Humidity Sensors Based on Nanodiamond Sensing Films

The quest for highly sensitive QCM humidity sensors: The coating of CNT/MOF composite sensing films as case study

“…The dispersion process is relatively faster and does not require long ultrasonication [22], stirring [34] or milling process [38]. The composite films here are synthesized at 50 o C, making it a low cost process compared to previous reports, which require high temperatures above 500 o C [27,34,37,38]. Lastly, the sensitivity demonstrated by 0.5 mg CNT-HKUST-1 composite thin film is up to ten times better when compared to the previously reported QCM-based humidity sensors, thereby making it a promising approach towards, simple, low-cost, low-power, stable, reliable and highly sensitive humidity sensors.…”

“…Humidity sensors based on various transduction techniques, including acoustic [4], resistance [5,6], magnetic [7], resonance [8], optical [9][10][11], impedance [12][13][14], delay-line [15], capacitance [16][17][18][19], and thermal [20] have been reported. Among these methods, is quartz crystal microbalance (QCM) technique, which are bulk acoustic-wave resonators, which have wide measuring range, are low-cost, small, stable, and highly sensitive to changes in mass with low detection limit, making them a preferable choice in sensing applications [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39]. The change in mass (∆m) on the surface of the QCM is related to the shift in resonance frequency (∆f) given by the Sauerbrey equation [40]:…”

“…For gas-sensing applications, QCMs alone are nonfunctional, as they require an additional layer (i.e. sensing layer) that induces a change in mass and/or viscoelastic characteristics on the surface when exposed to the target gas [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39]. QCMs for humidity sensing application have been intensively studied by coating them with different water-adsorbing materials, such as polymers [21,23,25,26,30,31,33,34,36,39], oxides [21,23,25,28,32,34,36,37], nano-structures [21-23, 25, 27-30, 32, 33, 35-39], and composites [21,23,25,26,29,30,36,39].…”

Quartz Crystal Micro–Balance Gas Sensor with Ink–Jet Printed Nano–Diamond Sensitive Layer

“…The largest shift in frequency of 147 Hz in our experiments was observed for changes of relative humidity in wet air. A higher sensitivity to humidity was reported by Yao et al [9] (up to 4 kHz @ 97 % RH) on QCM with an air-brush deposited nanodiamond sensitive layer.…”

Hydrophobic ZnO-TiO2Nanocomposite with Photocatalytic Promoting Self-Cleaning Surface

“…The measurement precision of QCM is affected by surface roughness and relative wettability [2]. The alteration in the wettability of the surface can result in large changes in resonant frequency (f) during adsorption of mass on the QCM surface.…”