Fabrication of magnetic clusters and rods using electrostatic co-assembly

TL;DR

This paper presents a novel electrostatic co-assembly method to fabricate magnetic nanostructures, including spherical clusters and rods, by controlling the desalting transition and applying magnetic fields, resulting in superparamagnetic rods with tunable properties.

Contribution

Introduces a new protocol for creating magnetic clusters and rods via electrostatic co-assembly and desalting transition, with control over shape and magnetic properties.

Findings

Spherical clusters form spontaneously during desalting.

Magnetic field induces one-dimensional growth into rods.

Nanostructured rods retain superparamagnetic properties.

Abstract

Using a novel protocol for mixing oppositely charged colloids and macromolecules, magnetic clusters and rods are fabricated using 10 nm-iron oxide nanoparticles and polymers. Here, we show that as the dispersions undergo the so-called desalting transition, spherical clusters in the range 100 nm - 1 {\mu}m form spontaneously upon dialysis or dilution. With a magnetic field applied during the dialysis, a one-dimensional growth of the aggregates is initiated, resulting in the formation of 1 - 100 {\mu}m rods of average diameter 200 nm. In this paper, we demonstrate that the nanostructured rods have inherited the properties of the iron oxide particles, namely to be superparamagnetic. We also discuss the dependence of the magnetic properties as a function of the nanoparticle diameter.