Viscoelastic response and profile of adsorbed molecules probed by quartz crystal microbalance.

The acoustic responses of molecular films with continuous viscoelastic profiles adsorbed on solid-liquid interfaces probed by quartz crystal microbalance (QCM) are analyzed using a continuum mechanics model. The numerically calculated results show that the shift of resonant frequency and the change of dissipation factor of a QCM are determined mostly by the change of viscoelastic profile of the layers in solution adjacent to the quartz-solution interface due to the adsorbed molecular film. For films with the same amount of absorbed mass, the changes in resonant frequency and the dissipation factor vary approximately linearly with the width of the film-solution interface in the profiles. Other viscoelastic properties of the adsorbed films are also affected by the profiles.