New cut angle quartz crystal microbalance with low frequency–temperature coefficients in an aqueous phase

In a traditional quartz crystal microbalance (QCM), an AT-cut (cut angle φ = 35.25° in yxl orientation) quartz wafer is employed because it has low frequency–temperature coefficients (dF/dT) at room temperature region. But when a QCM is in contact with a liquid phase, its frequency is also related to the properties of the liquid, which are temperature dependent. The value of dF/dT is about 20 Hz/°C for a 9 MHz AT-cut QCM with one side facing water. In this work, a group of QCMs in new cut angles were prepared. The influence of the cut angle on the frequency–temperature characteristic, response sensitivities to surface mass loading and viscodensity of liquid were investigated. An intrinsically temperature-compensated QCM sensor that possesses low dF/dT values in aqueous solution was reported. When a 9 MHz QCM with φ = 35.65° was contacted with water with one side, its dF/dT value is close to zero at ca. 25 °C and its averaged value of |dF/dT| is only 0.6 Hz/°C in the temperature range of 23–27 °C. The frequency responses to surface mass loading and viscodensity of liquid phase are very close among the QCMs with the cut angles in the range of 35.15–35.7°. The intrinsically temperature-compensated QCM was applied to investigate the alternate adsorption processes of cationic polyelectrolyte and silica nanoparticle.