Evaporation induced self-assembly of different shapes and sizes of nanoparticles: A molecular dynamics study.

Molecular dynamics simulations of Lennard-Jones particles have been performed to study the self-assembled structure of nanoparticles (NPs) formed upon evaporation of nanofluid droplets on a heated surface. Different shapes of NPs such as a sphere, cube, triangle, and rod are considered in this work for the nanofluid. The influence of solvent-surface and NP-surface interaction strengths, size, and shape of NPs is analyzed on the structure of the NP deposit formed upon evaporation. The solvophilic substrate leads to the formation of different structures such as the hemispherical clump, monolayer, and ring depending on the size, shape, and interaction between other pairs of atoms. On the other hand, the solvophobic substrate always leads to a clump of NPs. Structural and thermodynamic properties are calculated to characterize the self-assembled structures. The low pair energy and high excess entropy are the characteristics of a ring structure. Furthermore, the mean square displacement of NPs is found to be lower for the ring structure compared to the hemispherical clump structure, and this observation is independent of the shape and size of the NP. The change in arrangement from disorder to order is observed for rod shaped NPs during evaporation.