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Small. 2016 Jan 13;12(2):220-8. doi: 10.1002/smll.201502127. Epub 2015 Nov 18.

Binary Superlattices from {Mo132} Polyoxometalates and Maghemite Nanocrystals: Long-Range Ordering and Fine-Tuning of Dipole Interactions.

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Sorbonne Universités, UPMC Univ Paris 06, CNRS UMR 8232, Institut Parisien de Chimie Moléculaire, Université Pierre et Marie Curie, 4 place Jussieu, case courrier 42, F-75005, Paris CEDEX 05, France.
Sorbonne Universités, UPMC Univ Paris 06, CNRS, UMR 8233, MONARIS, Case courrier, 52, Université Pierre et Marie Curie, 4 place Jussieu, F-75005, Paris, France.
Laboratoire de Physique des solides, UMR CNRS 8502, Université Paris Sud, Bât. 510, 91405, Orsay CEDEX, France.


In the present article, the successful coassembly of spherical 6.2 nm maghemite (γ-Fe2O3) nanocrystals and giant polyoxometalates (POMs) such as 2.9 nm {Mo132} is demonstrated. To do so, colloidal solutions of oleic acid-capped γ-Fe2O3 and long-chain alkylammonium-encapsulated {Mo132 } dispersed in chloroform are mixed together and supported self-organized binary superlattices are obtained upon the solvent evaporation on immersed substrates. Both electronic microscopy and small angles X-ray scattering data reveal an AB-type structure and an enhanced structuration of the magnetic nanocrystals (MNCs) assembly with POMs in octahedral interstices. Therefore, {Mo132} acts as an efficient binder constituent for improving the nanocrystals ordering in 3D films. Interestingly, in the case of didodecyldimethylammonium (C12)-encapsulated POMs, the long-range ordered binary assemblies are obtained while preserving the nanocrystals magnetic properties due to weak POMs-MNCs interactions. On the other hand, POMs of larger effective diameter can be employed as spacer blocks for MNCs as shown by using {Mo132} capped with dioctadecyldimethylammonium (C18) displaying longer chains. In that case, it is shown that POMs can also be used for fine-tuning the dipolar interactions in γ-Fe2O3 nanocrystal assemblies.


binary superlattices; maghemites; magnetic dipolar interactions; polyoxometalates; {mo132}


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