There is a demand for new straightforward approaches for stabilization and solubilization of various nanoparticulate materials in their colloidal form, that pave way for fabrication of materials possessing compatibility with wide range of dispersing media. Therefore in this thesis a new general method to form stable nanocrystals in water and organics using amphiphilic polymers generated through simple and low cost techniques is presented and discussed. Amphiphilic coating agents are formed using thiolated or carboxylated polyethylene glycol methyl ether (mPEG-SH) as a starting material. These materials are available with a wide variety of chain lengths. The method of obtaining of amphiphilic NPs is quite general and applicable for semiconductor CdTe nanocrystals as well as nanoscale noble metal (Au) and magnetic (Fe3O4) particles. This approach is based on anchoring PEG segment to the surface of a nanoparticle to form an amphiphilic palisade. Anchoring is realized via interaction of –SH (for CdTe and Au) or –COOH (in the case of magnetite) functional groups with particle’s surface. The resulting amphiphilicity of the nanocrystals is an inherent property of their surface and it is preserved also after careful washing out of solution of any excess of the ligand. The nanocrystals reversibly transfer between different phases spontaneously, i.e. without any adjustment of ionic strength, pH or composition of the phases. Such reversible and spontaneous phase transfer of nanocrystals between solvents of different chemical nature has a great potential for many applications as it constitutes a large degree of control of nanocrystals compatibility with technological processes or with bio-environments such as water, various buffers and cell media as well as their assembly and self-assembly capabilities.

There is a demand for new straightforward approaches for stabilization and solubilization of various nanoparticulate materials in their colloidal form, that pave way for fabrication of materials possessing compatibility with wide range of dispersing media. Therefore in this thesis a new general method to form stable nanocrystals in water and organics using amphiphilic polymers generated through simple and low cost techniques is presented and discussed. Amphiphilic coating agents are formed using thiolated or carboxylated polyethylene glycol methyl ether (mPEG-SH) as a starting material. These materials are available with a wide variety of chain lengths. The method of obtaining of amphiphilic NPs is quite general and applicable for semiconductor CdTe nanocrystals as well as nanoscale noble metal (Au) and magnetic (Fe3O4) particles. This approach is based on anchoring PEG segment to the surface of a nanoparticle to form an amphiphilic palisade. Anchoring is realized via interaction of –SH (for CdTe and Au) or –COOH (in the case of magnetite) functional groups with particle’s surface. The resulting amphiphilicity of the nanocrystals is an inherent property of their surface and it is preserved also after careful washing out of solution of any excess of the ligand. The nanocrystals reversibly transfer between different phases spontaneously, i.e. without any adjustment of ionic strength, pH or composition of the phases. Such reversible and spontaneous phase transfer of nanocrystals between solvents of different chemical nature has a great potential for many applications as it constitutes a large degree of control of nanocrystals compatibility with technological processes or with bio-environments such as water, various buffers and cell media as well as their assembly and self-assembly capabilities.

Cette thèse s'inscrit dans un contexte de recherche d'amélioration des propriétés d'extraction d'ions sur phase solide. Au travers de ces travaux est développée une méthodologie innovante visant à adapter la structuration, la morphologie ainsi que les fonctions d'extraction aux ions et aux milieux cibles. Pour cela, nous avons opté pour une méthode « tout-en-un » passant par l'utilisation d'organosilanes amphiphiles. Composées d'une tête condensable et d'une tête « extractante » aux extrémités d'une chaîne hydrophobe, ces molécules polyvalentes font office à la fois d'agent matriciel silicique, d'agent structurant et d'agent extractant. Par analogie avec un tensioactif, nous avons montré que l'auto-assemblage de telles molécules est gouverné par des paramètres liés notamment à la taille de la partie hydrophile de la molécule. En utilisant différents agents de courbure, il est possible de jouer sur la taille du couple agent de courbure/fonction extractante. La courbure à l'interface entre le milieu et l'agrégat est donc ajustable, ce qui conduit à différents types d'agrégation. Par cette méthode, des bicouches, des vésicules et des micelles directes cylindriques ont été obtenues. A l'inverse, l'ajout de précurseur de silice (TEOS) dans la préparation peut conduire au gonflement des structures et à l'inversion de l'agrégation vers des micelles inverses cylindriques. L'effet du solvant a également été étudié et a permis d'aboutir à des morphologies très diverses. Enfin, l'accessibilité des fonctions et les propriétés d'extraction des matériaux élaborés ont été évaluées au travers de modifications chimiques de la tête extractante et de tests d'extraction d'ions métalliques (Terres rares, platinoïdes …). / The aim of this study is to develop a suitable “all-in-one” approach involving amphiphilic organosilane precursors in order to prepare hybrid materials for solid phase extraction processes. Such molecules combine both condensable and functional parts around a long hydrophobic alkyl chain.Similarly to a surfactant, the amphiphilic behavior of the organosilane molecules is governed by the size of the hydrophilic extractant function. By playing with the curvature agent size, it is possible to adjust the size of the couple extractant part/curvature agent at the interface between the aggregates and the surrounding media. Therefore, the aggregation shape is tunable. This approach constitutes an efficient and original method in order to tune the nanostructure of highly functionalized silica at the early stage of the elaboration. Hybrid organic-inorganic planar objects and vesicles are obtained for smaller curvature agents. Increasing the size of the curvature agent results in a transition of the aggregation geometry from vesicles to cylindrical direct micelles, leading to highly functionalized nanofibers.Comparatively, the addition of a silica precursor as TEOS in the preparation results in the swelling of the condensable part of the amphiphilic organosilane molecules. Thereby, as a curvature agent, the addition of TEOS allows tuning the aggregation towards reverse cylindrical micelles. Solvent effects have also been evaluated, appearing as a critical morphological parameter. Macroporous materials, blackberry-like particles and elongated or spherical nanoparticles can be obtained depending on the solvent.Finally, the accessibility of the functions and the extraction properties of the materials have been studied through chemical modifications and metallic ion extraction experiments (Rare earth elements, platinoids …).