Frictional duality of metallic nanoparticles: Influence of particle morphology, orientation, and air exposure

The contact area dependence of the interfacial friction experienced during the translation of antimony nanoparticles deposited on a graphite substrate is studied under different conditions using the tip of an atomic force microscope as a manipulation tool. In vacuum a dual behavior of the friction-area curves is found, characterized by the observation that some particles exhibit friction below the detection limit while other similarly sized particles showed constant shear stress values. Detailed investigations prove the reproducibility of this effect, revealing that neither the particle's morphology nor their alignment relative to the substrate lattice influence the findings. In contrast, we observe that a temporary exposure to ambient air can lead to a drastic increase in the particle's friction.