Tuning the dipole-directed assembly of core-shell nickel-coated gold nanorods

We present the dipole-directed assembly of nickel-coated gold nanorods into nanorings and nanowires. We used two different coating methods to synthesise these core-shell superstructures. Surprisingly, the two coating methods lead to very different kinds of dipole directed assembly. We show that the resultant dipole assembly is very sensitive to the reaction conditions and can be tuned to obtain core-shell nanochains, nanorings, and nanowires. In addition to the presented experimental work, cluster moving Monte Carlo simulations of a system of core-shell nanorods were carried out. These simulations are based on a small number of magnetic interaction energy terms and do not explicitly deal with steric interactions or van der Waals forces. The simulation results are in line with the obtained experimental results, confirming that the magnetic self-assembly of core-shell nanorods can be described by means of a relatively simple model.