Frédéric Lerouge

Towards thrombosis-targeted zeolite nanoparticles for laser-polarized 129Xe MRI

The synthesis and functionalisation of zeolite nanoparticles designed for laser-polarized 129Xe NMR experiments in solution are described. These nanoparticles were functionalized by using original synthesis pathways through semicarbazide COCHO chemistry in order to ensure anchoring of a peptide for targeting biological receptors and attachment of PEG chains for in vivo experiments. Results demonstrated that accessibility of the dissolved noble gas to the micropores was maintained after functionalization. γ Scintigraphy with 111In linked to the zeolite particles has been investigated in order to follow the behaviour of the zeolite nanoparticles in mice. These preliminary 111In scintigraphy experiments showed the localization of the nanoparticles after injection in mice and their biodistribution, as a first proof-of-concept towards in vivo129Xe MRI.

Auto-organization of Nanostructured Organic−Inorganic Hybrid Xerogels Prepared by Sol−Gel Processing: The Case of a “Twisted” Allenic Precursor

Nanostructured hybrid materials prepared by sol−gel hydrolysis−polycondensation of the precursor 1,3-bis(propyltrimethoxysilyl)-1,3-diphenylallene P having a bulky rigid and twisted core with two short flexible arms exhibited a self-organization evaluated by birefringence measurements (micrometric scale) and X-ray diffraction studies (nanometric scale). These observations show that the auto-organization of hybrid materials is not limited to rigid-rod or mesogenic spacers. It appears as a more general phenomenon. The twisted geometry of the organic group induced an anisotropic organization, the morphology of which was unprecedented and different from the one observed with the linear or mesogenic hybrid materials previously studied. Moreover, the birefringence pictures were also different from those observed with liquid crystals. In some cases unprecedented wavy parallel cracks showed the extension of the organization over the millimetric scale. It is the same for the X-ray diffraction. In all the cases pre...

Self-organization of a tetrasubstituted tetrathiafulvalene (TTF) in a silica based hybrid organic–inorganic material

A hybrid organic inorganic nanostructured material containing a TTF core substituted by four arms exhibited a high level of both condensation at silicon (96%) and self-organization as evidenced by X-ray diffraction and an unprecedented birefringent behaviour.

Auto-organization of nanostructured organic–inorganic hybrid xerogels prepared from planar precursors by sol–gel processing

Nanostructured hybrid materials were prepared by sol–gel hydrolysis-polycondensation of 1,3,5-tris(p-triethoxysilylphenyl)benzene PR having a rigid structure and 1,3,5-tris(p-trimethoxysilylpropylphenyl)benzene PF having a planar core connected to three short and flexible arms. Both precursors presented nine directions for solid formation. Their organization was evaluated by birefringence measurements (micrometre scale) and X-ray diffraction studies (nanometre scale). The influence of the planar geometry and the rigidity or flexibility of the organic groups has been studied as well as the effect of changes in experimental conditions. It has been shown that the organization of these solids was less influenced by the experimental parameters than in the case of linear precursors. In the case of the rigid precursor PR, the solids obtained XR had a high intensity of birefringence (7.5–8 × 10−3) and the gels presented cracks whatever the experimental conditions (nucleophile or acid catalysis). In contrast the flexible precursor PF led to solids XF with a lower birefringence (6.2–6.8 × 10−3) and the morphology of the solids in the cells depended on the concentration of catalyst. Interestingly the birefringence appeared without cracks with a lower amount of catalyst and isotropic circular cross-shaped nodules were observed in this case whatever the temperature. The X-ray diffraction diagrams clearly showed that these solids presented a better nanometre scale organization than the gel formed from 1,3,5-tris(trimethoxysilyl)benzene. These observations show that the auto-organization of hybrid materials appears induced by weak van der Waals type interactions as a general phenomenon which is not limited to linear and mesogenic precursors.

Hydrophobic induced supramolecular self-organization of tetrahedral units based on van der Waals interactions

Nanostructured hybrid materials were prepared by sol–gel hydrolysis–polycondensation of tetrakis(4-trisisopropoxysilylphenyl)germane PGe and tetrakis(4-trisisopropoxysilylphenyl) tin PSn which present a tetrahedral germanium or tin central atom. Both precursors presented twelve directions for solid formation oriented regularly on the four directions of the tetrahedron. Their organization was evaluated by X-ray diffraction studies (nanometric scale) and birefringence measurements (micrometric scale). It has been shown that the organization of these solids was influenced by the experimental parameters. The intensities of birefringence lay in the same range (1.6 × 10−3 to 2.1 × 10−3) for all the gels XGe and XSn. Regular parallel rectangular chunks were observed in all cases. The orientation of the optical axis was found perpendicular to the edges of the chunks in all cases. The existence of such optical axes regularly oriented towards the edges of the chunks corresponded to an anisotropic organization at the micrometric scale. The results presented here strengthen the fact that the auto-organization observed in nanostructured organic–inorganic hybrid materials occurs during the formation of Si–O–Si bonds, which transforms intermolecular interactions into intramolecular ones corresponding to the weak van der Waals-type interactions existing between the organic units. The role of hydrophilic–hydrophobic interactions is discussed.

Self-organization of porphyrin units induced by magnetic field during sol–gel polymerization

The use of a magnetic field as a controlling factor during the hydrolysis-polycondensation of porphyrin precursors substituted by Si(OR)(3) groups, induces a self-organization of porphyrin moieties due to the stacking of these units in the hybrid material and this study also confirms the effect of the magnetic field in the nano- and micrometric organization during the kinetically controlled polycondensation process.

The van der Waals induced supramolecular organization of hydrophobic tetrahedral units in the course of hydrolytic polycondensation

This paper describes the hydrolytic polymerization of a tetrahedral precursor in the four directions. The hydrolytic polycondensation occurring at silicon led to highly polycondensed solids (around 100%). The solids obtained exhibited an organization at the nanometric scale evidenced by X-ray powder diffraction and another at the micrometric scale (birefringence experiments). The optical axis determination which corresponds to the orientation of the cross-linked colloids exhibits an inverse micelle type geometry. Thus the self-organization of the tetrahedral units is controlled by the poor hydrophilicity of the medium.