Microscopic Dynamics of the Orientation of a Hydrated Nanoparticle in an Electric Field

We use atomistic simulations to study the orientational dynamics of a nonpolar nanoparticle suspended in water and subject to an electric field. Because of the molecular-level effects we describe, the torque exerted on the nanoparticle exceeds continuum-electrostatics--based estimates by about a factor of 2. The reorientation time of a 16.2×16.2×3.35 ³ nanoparticle in a field |E|>0.015 V/ is an order of magnitude less than the field-free orientational time (~1 ns). Surprisingly, the alignment speed is nearly independent of the nanoparticle size in this regime. These findings are relevant for design of novel nanostructures and sensors and development of nanoengineering methods.