Gold clusters sliding on graphite: a possible quartz crystal microbalance experiment?

Abstract

A large measured 2D diffusion coefficient of gold nanoclusters on graphite has been known experimentally and theoretically for about a decade. When subjected to a lateral force, these clusters should slide with an amount of friction that could be measured. We examine the hypothetical possibility to measure by Quartz Crystal Microbalance (QCM) the phononic sliding friction of gold clusters in the size range around 250 atoms on a graphite substrate between 300 and 600 K. Assuming the validity of Einstein's relations of ordinary Brownian motion and making use of the experimentally available activated behavior of the diffusion coefficients, we can predict the sliding friction and slip times as a function of temperature. It is found that a prototypical deposited gold cluster could yield slip times in the standard measurable size of 10 −9 sec for temperatures around 450 − 500 K, or 200 C. Since gold nanoclusters may also melt around these temperatures, QCM would offer the additional chance to observe this phenomenon through a frictional change.

Lubricity of gold nanocrystals on graphene measured using quartz crystal microbalance

“…The question remains on why we observe the enhanced lubricity that exceeds the previous prediction1819. We use molecular dynamics (MD) simulations to determine the answer.…”

Effect of temperature on kinetic nanofriction of a Brownian adparticle

“…Therefore, our result can be used to predict the temperature dependence of the required driving force to control a C 60 admolecule on graphene as a component of molecular devices operating at thermal equilibrium state [21,44]. Moreover, our findings might help tune the experimental setup for measuring the sliding force in the corresponding QCM experiments, where the required resolution is beyond the temporal/spatial precision of available equipments [29]. The present work can be generalized to any classical adsorbate/substrate system provided that the adsorbate exhibits a continuous Brownian motion rather than a stick-slip (hopping) motion.…”

“…It is noted that a small activation energy of surface diffusion was recently obtained both experimentally and computationally in the benzene/graphite system [7,9]. For comparison, the activation energy in the gold-cluster/graphite system is an order of magnitude higher than the C 60 /graphene system [29,36]. The two distinct regimes of the nanoscale BM, which are distinct from the traditional picture of surface diffusion, were recently reported as quasi-continuous BM (QCBM) below 75 K, and ballistic-like BM (BLBM) above 75 K [24].…”

“…According to the fluctuation dissipation theorem (FDT) [43], the Einstein relation is held where the particle responds to weak driving forces. Such weak driving forces include the thermal fluctuations at an equilibrium temperature, as well as weak applied driving forces realized in molecular motor [21] and QCM experiments [29]. Hence, within the range of validity of FDT, where the velocity of a drifting nanoparticle (of mass m) is comparable to its thermal velocity (v th / (k B T/m) ½ ), the kinetic nanofriction force (F f = mgv motion ) imposed on the adparticle by the substrate can be evaluated from the diffusion coefficient of its Brownian motion.…”

“…http://dx.doi.org/10.1016/j.cplett.2013.03.020 narrow temperature range around 140 K [7]. The sliding friction force of a gold cluster on graphite at a variety of temperatures was theoretically investigated [29]. It was assumed that the goldcluster diffusion on graphite followed a BM and the SE relation was applicable.…”