Tailoring inter-core distance of clustered SPIONs using silica spacers for enhanced magnetic particle imaging (MPI).

An emulsion-based self-assembly strategy for the formation of Superparamagnetic Iron Oxide Nanoparticles (SPION) clusters with precisely tunable silica spacers is reported. Systematic control of the silica shell thickness enables modulation of magnetic inter-core spacing within the clusters. This results in a pronounced enhancement in Magnetic Particle Imaging (MPI) signal generation, attributed to a combination of enhanced long-range magnetic dipole-dipole coupling interaction, the suppression of short-range exchange-like coupling interaction and the passivation of SPION surface spin disorder. The interplay between effects gives rise to an increase in harmonic content of clustered core@shell particles compared with their non-clustered counterparts, resulting in brighter MPI images.