Charge Transfer to Metal Nanoparticles Bouncing from Conductive Surfaces

The charging behavior of metal nanoparticles bouncing from conductive surfaces was investigated in a single-stage-low-pressure-impactor. Ag and Pt particles of a fixed particle size between 20 nm and 100 nm were impacted on targets of bulk Au and Pt, respectively, and the resulting contact charge was measured as a function of impact velocity. The influence of target hardness was revealed by the comparison to measurements with soft nanostructured layers obtained by direct current sputtering of Au and Pt on mica discs. From the dataset, regions of elastic, elastoplastic, and fully plastic particle deformation were identified, and the size-dependent effective yield stress for the respective particle materials was calculated. The influence of electron back-tunneling in the separation phase of the collision on the effective contact charge is discussed.