title: Controlling the self-assembly of magnetic nanoparticles by competing dipolar and isotropic particle interactions.
abstract: Control over the self-assembly of magnetic nanoparticles (MNP) into superstructures due to different types of coupling is of interest in the development of "bottom-up" fabrication schemes. Here we realize a simple strategy for the systematic variation of particle interaction potential in magnetic nanoparticles. This is achieved by varying the effective surface potential by means of a co-surfactant introduced in the course of the synthesis process. As a consequence, the ability to form chain-like assemblies is affected by the resulting balance of attractive and repulsive forces. We use electron microscopy, electron diffraction, and light scattering methods to study a series of cobalt nanoparticles as a characteristic example of ferromagnetic MNP. We demonstrate experimentally and substantiate theoretically that the observed behavior results from a balance between magnetic dipole-dipole, steric, and electrostatic interactions.
authors.affiliation: Chemical Engineering Department, Ben Gurion University, Beer Sheva 84105, Israel.
authors.forename: Manuela
authors.initials: M
authors.lastname: Hod
authors.affiliation: Institut für Physikalische Chemie, Department Chemie, Universität zu Köln, Luxemburger Str. 116, D-50939 Köln, Germany.
authors.forename: Celin
authors.initials: C
authors.lastname: Dobbrow
authors.affiliation: Institut für Physikalische Chemie, Department Chemie, Universität zu Köln, Luxemburger Str. 116, D-50939 Köln, Germany.
authors.forename: Mukanth
authors.initials: M
authors.lastname: Vaidyanathan
authors.affiliation: Institut für Physikalische Chemie, Department Chemie, Universität zu Köln, Luxemburger Str. 116, D-50939 Köln, Germany.
authors.forename: Debanjan
authors.initials: D
authors.lastname: Guin
authors.affiliation: Institut für Physikalische Chemie, Department Chemie, Universität zu Köln, Luxemburger Str. 116, D-50939 Köln, Germany.
authors.forename: Lhoussaine
authors.initials: L
authors.lastname: Belkoura
authors.affiliation: Institut für Physikalische Chemie, Department Chemie, Universität zu Köln, Luxemburger Str. 116, D-50939 Köln, Germany.
authors.forename: Reinhard
authors.initials: R
authors.lastname: Strey
authors.affiliation: Chemical Engineering Department, Ben Gurion University, Beer Sheva 84105, Israel.
authors.forename: Moshe
authors.initials: M
authors.lastname: Gottlieb
authors.affiliation: Institut für Physikalische Chemie, Department Chemie, Universität zu Köln, Luxemburger Str. 116, D-50939 Köln, Germany. Electronic address: annette.schmidt@uni-koeln.de.
authors.forename: Annette M
authors.initials: AM
authors.lastname: Schmidt
keywords: Chain-like objects; Dipolar particle coupling; Ferromagnetic nanoparticles; Interaction potential; Magnetic super-structures; Nanoparticle self-assembly