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 x 16.2 x 3.35 A(3) nanoparticle in a field |E| > 0.015 V/A is an order of magnitude less than the field-free orientational time (approximately 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.