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The 2015 AFC thesis award in Physics is attributed to Mohamed Salah Amara

During his PhD thesis, Mohamed Salah Amara has studied : first, the synthesis of metal oxide nanotubes, under the supervision of Antoine Thill (LIONS/NIMBE, CEA-Saclay) and second, the structure of these nanotubes and the properties of confined liquids, and in particular water, under the direction of Pascale Launois at Laboratoire de Physique des Solides (LPS, Orsay), in collaboration with Erwan Paineau et Stéphan Rouzière (LPS) and with Stéphane Rols (ILL, Grenoble).

The title of M.S. Amara thesis is ‘Imogolite nanotubes and properties of confined water : organization, structure and dynamics’. Imogolite nanotubes are hydrophilic alumino-silicate and alumino-germanate nanotubes with nominal formula Si(Ge)Al2O7H4. Alumino-silicate nanotubes can be found in soils and both types of nanotubes are synthesized by soft chemistry, as single- or double-walled nanotubes. Since the seminal article on the structure of natural imogolite nanotubes in 1972, where the authors however underlined that they could not conclude on their exact structure, no complete experimental study was performed.

Mohamed Salah Amara proposed a new methodology to analyze the nanotube structure, based on a geometrical minimization of interatomic distances and angles and to the comparison of simulated X-ray scattering (XRS) diagrams to coupled small and wide-angle XRS experiments. He was thus able to propose, for the first time, the exact structure of natural and synthetic single-walled alumino-silicate nanotubes and of synthetic single-walled alumino-germanate nanotubes. He moreover studied the structure of the double-walled alumino-germanate nanotubes, showing that the two walls periods are incommensurate. He studied by XRS the deformation of interacting nanotubes, with potential applications on their properties. He also showed that nanotubes, chemically modified to become hydrophobic, encapsulate organic molecules, with potential applications for water decontamination. Last, he showed, for the first time, thanks to XRS and inelastic neutron scattering experiments, the existence of two types of water inside hydrophilic imogolite nanotubes, with specific dynamical properties. The results of Mohamed Salah Amara on the structure of imogolites could become a benchmark for the geologists, chemists and physicists studying these nanotubes and their properties. Mohamed Salah Amara thesis moreover opens up new prospects in the field of molecular nanoconfinement.

Financing :

Région Ile-de-France (Domaine d’intérêt majeur (DIM) : NanoK
réseau C’Nano
projet IMOGEAU

Contact :

Pascale Launois