Synthesis of Ge-imogolite: influence of the hydrolysis ratio on the structure of the nanotubes

The synthesis protocol for Ge-imogolite (aluminogermanate nanotubes) consists of 3 main steps: base hydrolysis of a solution of aluminum and germanium monomers, stabilization of the suspension and heating at 95 °C. The successful synthesis of these nanotubes was found to be sensitive to the hydrolysis step. The impact of the hydrolysis ratio (from n(OH)/n(Al) = 0.5 to 3) on the final product structure was examined using a combination of characterization tools. Thus, key hydrolysis ratios were identified: n(OH)/n(Al) = 1.5 for the formation of nanotubes with structural defects, n(OH)/n(Al) = 2 for the synthesis of a well crystallized Ge imogolite and n(OH)/n(Al) > 2.5 where nanotube formation is hindered. The capability of controlling the degree of the nanotube's crystallinity opens up interesting opportunities in regard to new potential applications.