Ionic liquids (ILs) are a novel class of ionic solvents, which are being used more and more often in chemical systems based on nanoparticles (NP) for several industrial and technological applications. However, at present we are unable to master the state of dispersion or aggregation of NP in these solvents, and the classic theories applied to colloidal stability, such as the DLVO, cannot be applied. In particular, the difficulty is found in the description of the electrostatic interactions in these ionic media. In this work, we try to better understand colloidal interactions in ILs through two systems that have been thoroughly characterized separately: magnetic maghemite nanoparticles, whose surface is well controlled in water, and the ionic liquid ethylammonium nitrate (EAN), known for its resemblance to water. These two systems are finally mixed together and studied at both the macroscopic and microscopic levels. We perform characterizations through several techniques: flame atomic absorption spectroscopy, optical microscopy under magnetic field, scattering methods (neutrons, X-rays and light), magneto-optic birefringence. We discover the importance of having a charged NP surface in order to obtain stable maghemite dispersions in EAN. In particular, the best colloidal stability is reached by adsorbing citrate molecules on the NP surface. We further investigate the effect of the NP's size and concentration, of the cationic counterion used to compensate the charge of citrate, of water content. Finally, we transfer our acquired knowledge to the realization of dispersions in biocompatible ILs.
| Identifer | oai:union.ndltd.org:CCSD/oai:tel.archives-ouvertes.fr:tel-01058482 |
| Date | 25 February 2014 |
| Creators | Mamusa, Marianna |
| Publisher | Université Pierre et Marie Curie - Paris VI |
| Source Sets | CCSD theses-EN-ligne, France |
| Language | English |
| Detected Language | English |
| Type | PhD thesis |
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