Colloidal magnetic nanocrystal clusters: variable length-scale interaction mechanisms, synergetic functionalities and technological advantages

What is it about?

We discuss the progress in complex colloidal systems of individual nanocrystals arranged in tailored cluster-like structures with focus on those of iron oxide chemical origin. Such size-tunable (diameter <100 nm) nanostructures can be obtained upon careful modification of surfactant-assisted chemical synthesis parameters. While such clusters can retain the magnetic behavior of their individual nanocrystals (superparamagnetic at room temperature), they experience interactions which affect the collective macroscopic behaviour, postulating to a hierarchy of length-scale dependent mechanisms. In view of this complexity, we use complementary experimental tools and theory to understand the role of the emerging intra-cluster surface-spin disorder, exchange and dipole-dipole interactions. The coexistence of these competing physical contributions within the same particle ensemble reveals that the clusters’ bulk magnetic state is strongly mediated by the underlined superspin glass dynamics. The emergence of such cooperative mechanisms is shown to be the key in the design of biocompatible cluster-like targeted theranostic agents.

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Why is it important?

We show that water-dispersible, of low-cytotoxicity colloidal nano-assemblies of iron-oxides can address successfully function-driven requirements for theranostics in healthcare market, including excellent capacity as T2-contrast generation in magnetic resonance imaging (MRI) and increased heat dissipation capability in magnetic hyperthermia treatment of diseases.

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