  Large-scale molecular dynamics simulations are used to simulate a layer of
nanoparticles diffusing on the surface of a liquid. Both a low viscosity
liquid, represented by Lennard-Jones monomers, and a high viscosity liquid,
represented by linear homopolymers, are studied. The organization and diffusion
of the nanoparticles are analyzed as the nanoparticle density and the contact
angle between the nanoparticles and liquid are varied. When the interaction
between the nanoparticles and liquid is reduced the contact angle increases and
the nanoparticles ride higher on the liquid surface, which enables them to
diffuse faster. In this case the short range order is also reduced as seen in
the pair correlation function. For the polymeric liquids, the out-of-layer
fluctuation is suppressed and the short range order is slightly enhanced.
However, the diffusion becomes much slower and the mean square displacement
even shows sub-linear time dependence at large times. The relation between
diffusion coefficient and viscosity is found to deviate from that in bulk
diffusion. Results are compared to simulations of the identical nanoparticles
in 2-dimensions.
