title: Size distribution of superparamagnetic particles determined by magnetic sedimentation.
abstract: We report on the use of magnetic sedimentation as a means to determine the size distribution of dispersed magnetic particles. The particles investigated here are (i) single anionic and cationic nanoparticles of diameter D approximately 7 nm and (ii) nanoparticle clusters resulting from electrostatic complexation with polyelectrolytes and polyelectrolyte-neutral copolymers. A theoretical expression of the sedimentation concentration profiles at the steady state is proposed, and it is found to accurately describe the experimental data. When compared to dynamic light scattering, vibrating sample magnetometry, and cryogenic transmission electron microscopy, magnetic sedimentation exhibits a unique property: it provides the core size and core size distribution of nanoparticle aggregates.
authors.affiliation: Matière et Systèmes Complexes, UMR 7057 CNRS Université Denis Diderot Paris-VII, 140 rue de Lourmel, F-75015 Paris, France. jean-francois.berret@ccr.jussieu.fr
authors.forename: J-F
authors.initials: JF
authors.lastname: Berret
authors.forename: O
authors.initials: O
authors.lastname: Sandre
authors.forename: A
authors.initials: A
authors.lastname: Mauger
mesh_terms: D000838:Anions; D002412:Cations; D002627:Chemistry, Physical / Q000379:methods*; D008027:Light; D008280:Magnetics; D046529:Microscopy, Electron, Transmission; D015233:Models, Statistical; D053758:Nanoparticles / Q000737:chemistry*; D049329:Nanostructures; D036103:Nanotechnology / Q000379:methods*; D010316:Particle Size; D011108:Polymers / Q000737:chemistry; D012542:Scattering, Radiation; D055672:Static Electricity; D013499:Surface Properties
chemical_list: D000838:Anions; D002412:Cations; D011108:Polymers