Reorientation kinetics of superparamagnetic nanostructured rods

Abstract

The attractive interactions between oppositely charged species (colloids, macromolecules etc) dispersed in water are strong, and the direct mixing of solutions containing such species generally yields to a precipitation, or to a phase separation. We have recently developed means to control the electrostatically-driven attractions between nanoparticles and polymers in water, and at the same time to preserve the stability of the dispersions. We give here an account of the formation of supracolloidal aggregates obtained by co-assembly of 7 nm particles with copolymers. Nanostructured rods of length comprised between 5 and 50 microns and diameter 500 nm were investigated. By application of a magnetic field, the rods were found to reorient along with the magnetic field lines. The kinetics of reorientation was investigated using step changes of the magnetic field of amplitude 90 degrees. From the various results obtained, among which an exponential decay of the tangent of the angle made between the rod and the field, we concluded that the rods are superparamagnetic.

12 pages - 452kB 7 - figures - 1 Table will be published in Journal of Physics : Condensed Matter

References in corpus (6)

• Precipitation-Redispersion of Cerium Oxide Nanoparticles with Poly(Acrylic Acid) : Towards Stable Dispersions
• Size Distribution of Superparamagnetic Particles Determined by Magnetic Sedimentation
• Stoichiometry of Electrostatic Complexes Determined by Light Scattering
• Stable Oxide Nanoparticle Clusters Obtained by Complexation
• Evidence of Overcharging in the Complexation between Oppositely Charged Polymers and Surfactants
• Magnetic tubules

Cited by in corpus (2)

• Electrostatic co-assembly of magnetic nanoparticles and fluorescent nanospheres: a versatile approach toward bimodal nanorods
• In vitro toxicity and uptake of magnetic nanorods