Cobalt nanoparticles with tuned interaction potential: Towards worm- and chain-like aggregates

C. Dobbrow - M. Vaidyanathan - L. Belkoura - D. Guin - A. M. Schmidt

Department Chemie, Universität zu Köln, Luxemburger Str. 116, D-50939 Köln }{ National Institute of Technology, Dumas Road, Ichchhanath Surat-395007, India

Abstract
In this work, we use intrinsic particle properties to create a balance between repulsive and attractive forces in ferromagnetic particles. This opens a pathway to the design of super-structured ferromagnetic particle ensembles from the interplay of attractive dipole-dipole interaction and repulsive electrostatic forces. We vary the amount of charge-inducing ligands, tri-octylphosphine oxide (TOPO) during the particle synthesis and investigate the influence of the TOPO concentration on the particle size distribution and core self-assembly, both by TEM and by dispersion-based methods. Unexpected correlations between the core size, hydrodynamic radius and the magnetic properties are found, and the evolving structures can be tailored by adjusting the synthetic conditions in terms of chain morphology and degree of order. Tables 3, Figs 5, Refs 14.