Structural probing of clusters and gels of self-aggregated magnetic nanoparticles

B. Frka-Petesic¹ - E. Dubois¹ - L. Almasy¹ - V. Dupuis¹ - F. Cousin² - R. Perzynski¹

¹ UPMC PECSA UMR 7195 case 51, 4 place Jussieu, 75005 Paris, France
² LLB CEA-CNRS UMR 12, CE-Saclay, 91191 Gif-sur-Yvette, France

Abstract
The microstructure of home-made aqueous magnetic fluids based on maghemite (γ−Fe₂O₃) and cobalt ferrite (CoFe₂O₄) nanoparticles is monitored from repulsive on the average towards attractive on the average by tuning the interparticle electrostatic repulsion through modulations of ionic strength and pH. A self-aggregation leading to sols of individual clusters and/or a thixotropic gel phase is induced. Their microstructure under finely controlled physico-chemical conditions is probed in zero field by Small Angle X-ray Scattering and Ultra-Small Angle Neutron Scattering. Tables 1, Figs 5, Refs 40.