Wetting of nanoparticles and nanoparticle arrays

We report investigations of nanoparticulate wetting carried out using molecular dynamics simulations. Despite their small size, model ‘Lennard–Jones’ nanoparticles in simple Lennard–Jones solvents exhibit well defined contact angles, which for high surface tension interfaces have been shown to obey Youngʹs equation with surprising accuracy. In this paper we present new results for fully molecular models of nanoparticles at a water surface, where again well-defined contact angles are evident. Pressure area curves obtained in Langmuir trough experiments on (nano) particulates have been used in the past to determine contact angles. We have recently demonstrated by molecular dynamics and theory that, contrary to expectations, the collapse pressure measured in this experiment should be independent of contact angle and that the initial collapse mode is by surface buckling. We present new molecular dynamics results for arrays of nanoparticles with a contact angle of 72° at a liquid–vapour interface which confirm our earlier work and offer more information on the details of the structure of collapsed nanoparticle arrays.