Rapid impedance scanning QCM for electrochemical applications based on miniaturized hardware and high-performance curve fitting

An impedance system for QCM measurements is described which produces a much higher information content than existing oscillator methods. The new system is favourably priced, and fits on a small single printed circuit board. The use of a personal computer with a dedicated software algorithm enables fast fitting of the collected data and allows high flexibility without the need of a change in hardware. It was shown that this QCM device is able to collect stable and high-quality data with the – in electrochemistry not very commonly used – small and very inexpensive 0.55 in. diameter quartz devices, even under heavy load. A full spectrum containing serial and parallel resonance frequencies, with a band width of 20 kHz can be scanned within 200 ms at a resolution of 0.2 Hz. Lowering requirements, e.g. by scanning series resonance frequency only, the acquisition time can be reduced drastically. The electrochemical applications (EQCM) so developed was checked using known electrochemical tasks such as copper deposition, dissolution and the electropolymerization of aniline.