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

Abstract

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.

Atomistic modelling of friction of Cu and Au nanoparticles adsorbed on graphene

“…The slopes of the linear fits to the friction force data for Au NPs are 2.29 and 2.03 pN/nm 2 at a higher and lower F a , respectively. They exceed the values of 1.21 pN/nm 2 obtained in MD simulations for silver [7] and 1.04 pN/nm 2 from the experiments [3,5]. However, the experiments are performed at much lower sliding velocities than in the MD simulations, and the fact that the slope for the lower applied force is slightly smaller than for the higher force is consistent with a smaller slope at the AFM sliding velocities.…”

(In)commensurability, scaling, and multiplicity of friction in nanocrystals and application to gold nanocrystals on graphite

“…Very low friction was found in experiments with finite contacts at very low velocities to depend strongly on the orientation. 5,6 Coexisting states of very different friction have also been observed in the sliding of antimony nanoparticles 7,8 and have been attributed to contamination or (in)commensurate interfaces. Meanwhile, recent theoretical studies 9,10 have shown that nanocrystals can slide with constant orientation only for particular orientations.…”

Nonuniform friction-area dependency for antimony oxide surfaces sliding on graphite

“…To overcome a majority of these limitations, Ritter et al and Dietzel et al have pioneered a new approach in which the AFM tip is used to laterally manipulate antimony (Sb) nanoparticles, which have been thermally deposited on graphite and MoS 2 , forming atomically smooth interfaces with their substrates. [27][28][29][30][31] Thus, experimentally observed contact areas represent the real contact areas between the nanoparticles and the substrate, eliminating the need to distinguish between the apparent and real contact area, as it is usually the case for typical interfaces involving multiple asperities. 26 With the exception of the occasional observation of virtually vanishing friction due to structural lubricity under unusually clean conditions (almost exclusively ultrahigh vacuum), recording the lateral forces experienced by the AFM tip during the manipulation events has revealed a linear dependence of frictional force (F f ) on nanoparticle-substrate contact area (A) for the investigated size regimes (usually between 10 000 nm 2 to >100 000 nm 2 ).…”