Molecular Dynamics Simulations of Surfactant Functionalized Nanoparticles in the Vicinity of an Oil/Water Interface

Abstract

The localization of nanoparticles (NPs) at fluid/fluid interfaces has emerged as an effective self-assembly method. To understand the fundamentals of this localization mechanism, it is necessary to quantify the physical behavior of NPs in the vicinity of a fluid interface. Conventional theories treat the NP as a rigid object whose equilibrium position is dictated by the balance of its surface tensions with the two fluids. However, most NPs are functionalized with “soft” organic surface layers which play a large role in determining the shape of the NP. Through molecular dynamics simulations, we show that the functionalizing layer also greatly alters the interfacial behavior of the NP beyond the scope of common theory. Furthermore, we characterize the effect of the surface density of functionalizing molecules on the NP deformability. Our results have implications on the experimental interpretation of NP contact angles and may be useful for future theory development.

Molecular Simulation of Hydrophobin Adsorption at an Oil–Water Interface

“…Interfacial adsorption is then essentially irreversible which is consistent with the biological functions of these proteins. The desorption free energies are comparable to those found for synthetic nanoparticles, from both molecular simulation [27][28][29] and experimental measurements. 52 The adsorption strengths are significantly larger than those found for small surfacants and biomolecules.…”

Interactions and Stress Relaxation in Monolayers of Soft Nanoparticles at Fluid-Fluid Interfaces

“…Ligand-grafted metal or semiconductor nanocrystals at fluid-fluid interfaces are widely used in nanomaterials synthesis [13][14][15] and in catalytic processes [16]. Simulation studies predict the rearrangement of the ligand brush into anisotropic lensshaped configurations when these nanoparticles adsorb at fluid-fluid interfaces [4][5][6]8]. This prediction is supported by x-ray reflectivity measurements of nanoparticle density at the interface [7].…”

“…Soft colloids at fluid-fluid interfaces, for instance star copolymers [1], microgels [2,3], and polymer-or ligandgrafted nanoparticles [4][5][6][7][8][9], stretch and deform, adopting shapes that are dictated by the interplay of surface tension and deformability, much like in the wetting of membranes, vesicles [10], and soft solids [11,12]. Ligand-grafted metal or semiconductor nanocrystals at fluid-fluid interfaces are widely used in nanomaterials synthesis [13][14][15] and in catalytic processes [16].…”

Molecular dynamics study of nanoparticle stability at liquid interfaces: Effect of nanoparticle-solvent interaction and capillary waves

“…In pioneering work Bresme and Quirke employed molecular dynamics simulations to study the effect of line tension on the stability of nanoparticles at liquid interfaces [15][16][17] . More recently the interaction potential between a nanoparticle and a liquid interface was determined using Monte Carlo or molecular dynamics simulations, for uniform 18 , Janus (amphiphilic) 19 , and polymer-grafted nanoparticles 20 . Simulations have also been used to study the interactions between adsorbed nanoparticles 21 , self-assembly of nanoparticles at liquid-liquid interfaces 22 , and nanoparticle diffusion at interfaces 23,24 .…”