Forces affecting nanoparticles in fluid, and the shape of the acoustic signal accompanying particle detachment from QCM surface

In the present work we use a thickness shear mode resonator—QCM operating at variable amplitude. Not frequency shift is recorded during the measurement but a sharp signal generated during the rupture of nanoparticles from the surface under smoothly increasing amplitude of oscillations. We consider the process of nanoparticle rupture from the QCM surface. The nature of signal formation is described, the motion of the nanoparticle and forces affecting it are considered. A connection between the properties of the ruptured particle with signal form (shape) is revealed. A sharp single peak is observed during the rupture of a rigid spherical nanoparticle, while the separation of long nanometer-sized particles bound along their length is accompanied by peak broadening. If a nanoparticle composed of separate smaller particles is detached from the surface, the particle decomposes into fragments, and the signal appears as a set of separate peaks.