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Structural resolution of inorganic nanotubes with complex stoichiometry.

ABSTRACT: Determination of the atomic structure of inorganic single-walled nanotubes with complex stoichiometry remains elusive due to the too many atomic coordinates to be fitted with respect to X-ray diffractograms inherently exhibiting rather broad features. Here we introduce a methodology to reduce the number of fitted variables and enable resolution of the atomic structure for inorganic nanotubes with complex stoichiometry. We apply it to recently synthesized methylated aluminosilicate and aluminogermanate imogolite nanotubes of nominal composition (OH)3Al2O3Si(Ge)CH3. Fitting of X-ray scattering diagrams, supported by Density Functional Theory simulations, reveals an unexpected rolling mode for these systems. The transferability of the approach opens up for improved understanding of structure-property relationships of inorganic nanotubes to the benefit of fundamental and applicative research in these systems.

SUBMITTER: Monet G

PROVIDER: S-EPMC5964105 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature

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Structural resolution of inorganic nanotubes with complex stoichiometry.

Monet Geoffrey G Amara Mohamed S MS Rouzière Stéphan S Paineau Erwan E Chai Ziwei Z Elliott Joshua D JD Poli Emiliano E Liu Li-Min LM Teobaldi Gilberto G Launois Pascale P

Nature communications 20180523 1

Determination of the atomic structure of inorganic single-walled nanotubes with complex stoichiometry remains elusive due to the too many atomic coordinates to be fitted with respect to X-ray diffractograms inherently exhibiting rather broad features. Here we introduce a methodology to reduce the number of fitted variables and enable resolution of the atomic structure for inorganic nanotubes with complex stoichiometry. We apply it to recently synthesized methylated aluminosilicate and aluminoger ...[more]

PMID: 29789570

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Project description:Water dynamics in inorganic nanotubes is studied by neutron scattering technique. Two types of aluminosilicate nanotubes are investigated: one is completely hydrophilic on the external and internal surfaces (IMO-OH) while the second possesses an internal cavity which is hydrophobic due to the replacement of Si-OH bonds by Si-CH3 ones (IMO-CH3), the external surface being still hydrophilic. The samples have internal radii equal to 7.5 and 9.8 Å, respectively. By working under well-defined relative humidity (RH) values, water dynamics in IMO-OH was revealed by quasi-elastic spectra as a function of the filling of the interior of the tubes. When one water monolayer is present on the inner surface of the tube, water molecules can jump between neighboring Si-OH sites on the circumference by 2.7 Å. A self-diffusion is then measured with a value (D = 1.4 × 10-5 cm2 s-1) around half of that in bulk water. When water molecules start filling also the interior of the tubes, a strong confinement effect is observed, with a confinement diameter (6 Å) of the same order of magnitude as the radius of the nanotube (7.5 Å). When IMO-OH is filled with water, the H-bond network is very rigid, and water molecules are immobile on the timescale of the experiment. For IMO-OH and IMO-CH3, motions of the hydroxyl groups are also evidenced. The associated relaxation time is of the order of 0.5 ps and is due to hindered rotations of these groups. In the case of IMO-CH3, quasi-elastic spectra and elastic scans are dominated by the motions of methyl groups, making the effect of the water content on the evolution of the signals negligible. It was however possible to describe torsions of methyl groups, with a corresponding rotational relaxation time of 2.6 ps. The understanding of the peculiar behavior of water inside inorganic nanotubes has implications in research areas such as nanoreactors. In particular, the locking of motions inside IMO-OH when it is filled with water prevents its use under these conditions as a nanoreactor, while the interior of the IMO-CH3 cavity is certainly a favorable place for confined chemical reactions to take place.

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Structural resolution of inorganic nanotubes with complex stoichiometry.

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Structural resolution of inorganic nanotubes with complex stoichiometry.

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