INSTRUMENTATION FOR SIMULTANEOUS MEASUREMENT OF DOUBLE-LAYER CAPACITANCE AND SOLUTION RESISTANCE AT A QCM ELECTRODE

Double-layer capacitance and solution resistance are two parameters th at can be used to indicate dynamic changes occurring near the surface of an electrode. Here, we report the development of instrumentation th at simultaneously monitors data from the quartz-crystal microbalance ( QCM) sensor and the electrica] double-layer without the use of a poten tiostat. The development of this instrumentation is reported along wit h some preliminary data. Early indications are that the capacitance re sponds to structural changes in the electrical double-layer. Changes i n resistance reflect changes in the solution anywhere between the two electrodes. The frequency shifts of the QCM originate in structural ch anges that occur not only in the electrical double-layer but also fart her out into the solution.