Trapping plasmonic nanoparticles with MHz electric fields

Abstract

Dielectrophoresis drives motion of nanoparticles through the interaction of their induced dipoles with a non-uniform electric field. We experimentally observe rf dielectrophoresis on 100 nm diameter gold nanoparticles in solution and show that for MHz frequencies the nanoparticles can reversibly aggregate at the electrode gaps. A frequency resonance is observed at which reversible trapping of gold nanoparticle ‘clouds’ occurs in the gap centre, producing almost a thousand-fold increase in density. Through accounting for gold cores surrounded by a conducting double layer ion shell, a simple model accounts for this reversibility. This suggests substantial control over nanoparticle separation is possible, enabling the formation of equilibrium nano-architectures in specific locations.