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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.

Author information

1
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.
2
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.
3
Laboratoire de Physique des solides, UMR CNRS 8502, Université Paris Sud, Bât. 510, 91405, Orsay CEDEX, France.

Abstract

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.

KEYWORDS:

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

PMID:
26578032
DOI:
10.1002/smll.201502127

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