Magnetic nanoparticles (NPs) interact with neighboring NPs, so that their magnetic properties change depending on their interparticle distances. Control of their interparticle distance and organized structure thus enables us to develop new functional materials. However, the precise control in the interparticle distance of the magnetic NPs remains a great challenge because the magnetic NPs are subject to aggregation due to their strong interparticle magnetic attraction. In this study, FePt NPs have been modified with liquid-crystalline organic dendrons to introduce self-organizing ability into the FePt NPs. Dendron modification of FePt NPs was carried out through amidation between carboxy moieties on the surface of FePt NPs and amino-substituted dendrons. The diameter of FePt nano-core of the resulting dendron-modified FePt NPs was 3.5 ± 0.4 nm, while their interparticle distance expanded to 5.2 ± 0.6 nm from 3.2 ± 0.6 nm on a TEM grid after dendron modification (<b>Fig.1</b>). Their self-organized structure was investigated by small angle X-ray scattering (SAXS) measurements. The SAXS patterns changed as the temperature increased, with the three prominent peaks appearing at 90 °C. These peaks corresponded to the (110), (200) and (211) lattice planes of a BCC structure with a lattice constant of <i>a</i> = 9.2 nm. These scattering disappeared over 130 °C. These results suggested that the dendron-modified FePt NPs formed the BCC structure in the temperature range from 90 °C to 130 °C.

Liquid-crystalline organic-inorganic hybrid nanoparticles with a FePt nano-core and characterization of their self-organized structure

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