On the calculation of the potential of mean force between atomistic nanoparticles

Abstract

We study the potential of mean force (PMF) between atomistic silica and gold nanoparticles in the vacuum by using molecular dynamics simulations. Such an investigation is devised in order to fully characterize the effective interactions between atomistic nanoparticles, a crucial step to describe the PMF in high-density coarse-grained polymer nanocomposites. In our study, we first investigate the behavior of silica nanoparticles, considering cases corresponding to different particle sizes and assessing results against an analytic theory developed by Hamaker for a system of Lennard-Jones interacting particles (H.C. Hamaker, Physica A 4, 1058 (1937)). Once validated the procedure, we calculate effective interactions between gold nanoparticles, which are considered both bare and coated with polyethylene chains, in order to investigate the effects of the grafting density [Formula: see text] on the PMF. Upon performing atomistic molecular dynamics simulations, it turns out that silica nanoparticles experience similar interactions regardless of the particle size, the most remarkable difference being a peak in the PMF due to surface interactions, clearly apparent for the larger size. As for bare gold nanoparticles, they are slightly interacting, the strength of the effective force increasing for the coated cases. The profile of the resulting PMF resembles a Lennard-Jones potential for intermediate [Formula: see text], becoming progressively more repulsive for high [Formula: see text] and low interparticle separations.

Structure and thermodynamics of grafted silica/polystyrene dilute nanocomposites investigated through self-consistent field theory

“…On the other hand, the main advantage of SCFT in relation to FOMC is that it can directly calculate the free energy, enthalpy and entropy of mixing between the NP and the polymer matrix and the potential of mean force between two nanoparticles immersed in a host polymer matrix. 39,49,50 The calculations were performed by employing the SCFT in one dimension (radial distance or normal distance coordinates) by taking advantage of the symmetry of the nanoparticle/planar surface. This one-dimensional treatment is expected to perform fairly well at moderate to large grafting densities and molecular weights of grafted chains.…”

Ion-mediated charge-charge interactions drive aggregation of surface-functionalized gold nanoparticles

“…For example, Monte Carlo simulations demonstrated that ligand-mediated short-range attractive interactions between monolayer-protected AuNPs can lead to aggregation despite long-range electrostatic energy barriers 29 . All-atom Molecular Dynamics (MD) emphasized that the aggregation energy profile between polyethylene coated gold NPs is driven by short-range attraction and characterized by a large attractive well 25 , while coarse grained model demonstrated the effect of surface chemistry and coverage on the aggregation of thiol coated AuNPs 28 . Taken together these studies confirmed that hydrophobic interactions are the driving force behind NP aggregation, in agreement with the DLVO framework.…”

Measuring the Casimir Forces with an Adhered Cantilever: Analysis of Roughness and Background Effects

“…When gold interacts with silicon we can take σ 11 = 0.293 nm for Au and σ 22 = 0.392 nm for Si [61] and find for h c = 0.245 nm.…”