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Nanoparticules photomagnétiques et agents de contraste à base de réseaux de coordination

Abstract : Designing new objects in the perspective of creating useful functionalities at the nanoscale has been the subject of intense research efforts during the last 20 years. In the field of molecular magnetism, coordination nanoparticles (CNP) are among the most fascinating materials in the field of molecular magnetism because they may show bistability at room temperature under the effect of different external stimuli such as light, temperature, pressure, electrical field, etc…. The new and elegant route to stabilize negatively charged surfactant-free nanoparticles in water permitting an epitaxial growth of successive the layers of the same or of different Prussian Blue Analogues described by some of us was used in this work to design core-multi-shell nanocrystals with a fine tuning of their thickness. These network structures may be useful for several applications such as data storage and medical imaging.In the first part, we describe the synthesis of well controlled photomagnetic CsCoFe(CN)6 nanoparticles. The synthesis involves several factors that influence the size and homogeneity of the particles. The controlled growth of the size objects was also performed to investigate the effect of the size on the photomagnetic response. The assembly of these particles on oriented graphite (HOPG) substrates leads to a compact monolayer of several microns. The compact monolayers were used as template for the controlled growth of photomagnetic films. In the second part, we report the synthesis of sub-50 nm heterostructured nano-objects in which a ferromagnetic network of CsNiCr(CN)6 is combined to a photo magnetic CsCoFe(CN)6 layer in order to achieve synergy between the two components. The synergistic behavior is observed in such heterostructures and manifested by (i) a uniform reversal of the magnetization and (ii) a persistent increase of the photo-induced magnetization up to the “ordering” temperature (60 K) of the ferromagnetic component.The last part is devoted to the synthesis of nanosized coordination networks contrast agents. First, Prussian blue nanoparticles KFeFe(CN)6 with different sizes were prepared with excellent size control. Relaxivity values of the longitudinal component T1 of the relaxation time were found to depend on the size and the rate of the paramagnetic atoms present on the surface. On the other hand, we describe the synthesis of MnxIn1-xFe(CN)6 nanoparticles with different proportions of Mn. Different sizes were obtained, which depend on the rate of inserted Mn ions. We have demonstrated that the MnII ions are located on the surface in a sub-core-shell structure, which explains the high relaxivity values. The high relaxivity values of these particles show that they are excellent candidates as contrast agents for magnetic resonance imaging (MRI).
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https://tel.archives-ouvertes.fr/tel-00813757
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Submitted on : Tuesday, April 16, 2013 - 11:05:19 AM
Last modification on : Wednesday, October 14, 2020 - 3:42:31 AM
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Nada Dia. Nanoparticules photomagnétiques et agents de contraste à base de réseaux de coordination. Autre. Université Paris Sud - Paris XI; Université Libanaise. Faculté des Sciences (Beyrouth, Liban), 2013. Français. ⟨NNT : 2013PA112003⟩. ⟨tel-00813757⟩

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