Diffusion and Sedimentation in Suspensions of Shape-Anisotropic Nanoparticles

Nanoparticles are a crucial emerging technology in the fields of material science and chemical engineering, for example, to deliver medicines, to improve industrial processes such as oil recovery, and to enhance or modulate properties of other materials by making composites. Nanoparticle dynamics, such as diffusion or sedimentation, play an important role in determining how nanoparticles are processed and ultimately behave in these applications. The dynamics of spherical nanoparticles are well understood but far less is known about the dynamics of the many different shapes of nanoparticles that can be synthesized in the laboratory. To address this knowledge gap, we performed computer simulations of tetrahedral, cubic, octahedral, and spherocylinder nanoparticles suspended in a Newtonian solvent. We used the multiparticle collision dynamics (MPCD) method to model important solvent-mediated hydrodynamic interactions between nanoparticles. Diffusion and sedimentation coefficients were measured as a function of nanoparticle volume fraction using equilibrium and nonequilibrium simulations, respectively. The simulation results were compared to experimental data and theoretical predictions where available. This work provides useful reference data on the transport properties of nanoparticles with anisotropic shapes, and the methodology can be readily extended to new shapes.