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 16.2x16.2x3.35 A degrees(3) nanoparticle in a field vertical bar E vertical bar > 0.015 V/A degrees is an order of magnitude less than the field-free orientational time (similar to 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.