Establishment of "in situ" Measurement Method for mass and Viscoelasticity Changes at Interfaces between Electrode and Solution

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Analytical techniques using the quartz crystal electrodes are most suitable for examining the electrode reaction dynamics. The techniques can be divided into active method and passive method. In the active method, which is known as quartz crystal microbalance(QCM) technique, a quartz crystal itself is made to oscillate spontaneously and an oscillation frequency is counted using a frequency counter. On the other hand, in the passive method, which we call quartz crystal impedance(QCI) method herein, ac voltage is applied to a quartz crystal and an impedance-frequency spectrum is obtained. In this research, the in situ measurement systems of the both methods have been established. From the piezoelectric admittance measurements, it was found that the electrical equivalent circuit parameters(i.e., resistance R, inductance L and capacitance C components) on electrode surfaces can be evaluated and mean the mass, viscoelasticity and/or mechanical stress changes of thin films on electrodes during the redox reactions. The measurement method of the equivalent circuit parameters and the series resonant frequency of the electrode-separated piezoelectric quartz crystal was also established. It was demonstrated that this device can be a powerful tool for detecting changes in liquid properties.