(105f) Controllable Assembly of Magnetic Janus Particles and Their Electric Properties

Magnetic nanoparticles have potential applications in position sensing, ultrahigh density magnetic storage media, clinical diagnosis and treatment, biological labeling, and separation applications. However, their use is hampered by non-specific aggregation due to the interaction of their magnetic moments. Janus particles with magnetic caps have a distinct advantage over symmetric particles. They exhibit an asymmetric magnetization that makes them suitable building blocks for directed three-dimensional assembly under the exposure of external magnetic field. If the Janus particles have also metallic properties, the addition of an electric field provides an additional experimental parameter.

Here, we present a study of the preparation and assembly behavior of iron oxide capped Janus particles, in presence of both magnetic and electric fields with the orientation of the two fields either being parallel or perpendicular to each other. Iron oxide capped Janus particles are prepared via deposition of iron onto a polystyrene particle monolayer using physical vapor deposition in an oxygen/argon atmosphere. Subsequently, the modified particles are assembled in a magnetic field for 30 min. Three assembly behaviors are observed: (i) staggered chains, (ii) double chains, or (iii) no assembly. Subsequently, samples are exposed to parallel and perpendicular AC electric and magnetic fields.

We will report on the changes observed in the assembly behavior of iron-oxide capped Janus particles as a function of deposition rate and type of the applied field. A diagram will be presented relating deposition rate and assembly behavior. In addition, we will report on the behavior of double and staggered chains in parallel and crossed magnetic and electric fields.