Chemical reactivity of self-organized alumina nanopores in aqueous medium

This work is devoted to the characterization of the structure and chemistry of small self-organized nanopores of aluminum oxide in aqueous medium (diameter <20 nm). A structural model based on AlO4/AlO6 clusters is proposed to describe the amorphous oxide constituting the walls of the nanostructure. X-ray absorption near edge spectroscopy measurements, electrokinetic measurements and O18 tracer experiments bring to light the structural changes and the specific diffusion mechanism in the nanometer network. Immersion in boiling water induces both the transformation of AlO4 to AlO6 clusters and the release of sulfate species by hydrolysis. Water molecules rapidly diffuse in the nanostructure, but ion diffusion is selective because of surface positive charges and overlap of the surface electric field in very small pores.