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Nanotubes that change their shape when assembled


Imogolite nanotubes, which have a circular cross section, become hexagonal when organized in large bundles, forming a honeycomb lattice. Such deformation, evidenced by X-ray scattering, could induce new properties of these nanoobjects, with potential applications for separative chemistry, molecular storage or in nanofluidics for instance.

Nanotubes represent a model system for understanding confinement phenomena at the nanometer scale. Current research carried on by an LPS team deals in particular with the properties of nano-confined water, with possible applications for storage or desalination.

Imogolites are aluminosilicate or aluminogermanate nanotubes with chemical formula (HO)XO3Al2(OH)3, where X = Si or Ge. One of the current research projects led by an LPS team focuses on nano-confined water with potential applications in terms of storage or desalination. Imogolite nanotubes are of fundamental interest for understanding the properties of nano-confined water, which are significantly different from those of bulk water. They are hydrophilic, but one can vary their surface properties by functionalizing their inner or outer cavities. Those nanotubes are also considered for the preparation of nanomaterials with potential applications in the fields of the separative chemistry, molecular storage or nanofluidics.


X-ray scattering diagrams depending on the shape and organization of imogolite nanotubes.

 

In this work, we demonstrate the major influence of inter-tube interactions on the shape of imogolite nanotubes, synthesized within a collaboration with a CEA laboratory (LIONS). In dilute suspensions, Ge-imogolite nanotubes present circular cross sections. Drying via evaporation leads to the formation of a powder where nanotubes assemble in large bundles, on a two-dimensional hexagonal lattice. We performed a detailed analysis of the corresponding X-ray scattering patterns and showed, for the first time, that the nanotubes are no longer cylindrical, but that they become hexagonal. This experimental result should stimulate further theoretical or numerical studies. New physico-chemical properties are expected for this nano-honeycomb system.

 

Contacts :
Stéphan Rouzière
Pascale Launois

Reference :
Hexagonalization of Aluminogermanate Imogolite Nanotubes Organized Into Closed-Packed Bundles
Amara M. S., Rouzière S., Paineau E., Bacia-Verloop M., Thill A. and Launois P.
J. Phys. Chem. C 118, 9299–9306 (2014).