Molecular dynamics simulation of formation and growth of CdS nanoparticles

Monodispersed semiconducting nanoparticles are usually synthesised in a liquid medium using injection of an appropriate solution. A key factor in attaining a narrow particle size distribution (PSD) is the temporal separation of the nucleation and growth stages, where the former takes place during the injection. Faster injection produces a larger number of nuclei and a narrower PSD. The injection speed is expected to affect the diffusion of the ions in the solution and to create uniformly high supersaturation for a short period of time. In this paper, we study the growth of CdS nanoparticles during the injection by molecular dynamics simulation. A solution of Cd ions is injected into the simulation cell that contains sulphure ions; the variation of the PSD and its mean and variance are studied as functions of the injection velocity. Higher injection velocities produce narrower PSDs and smaller particles, hence providing a precise method for controlling both.