Surface-modified aluminogermanate nanotube by OPA: Synthesis and characterization

Partial Transformation of Imogolite by Decylphosphonic Acid Yields an Interface Active Composite Material

The phosphonic acid moiety is commonly used as an anchoring group for the surface modification of imogolite. However, the impact of the reaction on its structure has never been clearly analyzed before. We study the reaction of imogolite and decylphosphonic acid by combining infrared spectroscopy, X-ray scattering, scanning electron microscopy, transmission electron microscopy, and solid-state nuclear magnetic resonance spectroscopy. Instead of a surface functionalization, we observe the formation of a lamellar phase interconnected with imogolite bundles. Although we find no evidence for grafted imogolite tubes, we observe the expected dispersion characteristics and stabilization of water in toluene emulsions described in the literature. Based on the surface chemistry of imogolite, we propose an explanation for the observed reactivity and link the structural features of the obtained composite material to its dispersibility in toluene and its observed properties at the toluene-water interface.

Imogolite Nanotubes: A Flexible Nanoplatform with Multipurpose Applications

Among a wide variety of inorganic nanotubes, imogolite nanotubes (INTs) represent a model of nanoplatforms with an untapped potential for advanced technological applications. Easily synthesized by sol-gel methods, these nanotubes are directly obtained with a monodisperse pore size. Coupled with the possibility to adjust their surface properties by using straightforward functionalization processes, INTs form a unique class of diameter-controlled nanotubes with functional interfaces. The purpose of this review is to provide the reader with an overview of the synthesis and functionalization of INTs. The properties of INTs will be stated afterwards into perspective with the recent development on their applications, in particular for polymer/INTs nanocomposites, molecular confinement or catalysis.

Behaviour of hybrid inside/out Janus nanotubes at an oil/water interface. A route to self-assembled nanofluidics?

Imogolites are natural aluminosilicate nanotubes that have a diameter of a few nanometers and can be several microns long. These nanotubes have different chemical groups on their internal (Si-OH) and external (Al-OH-Al) surfaces, that can be easily functionalised independently on both surfaces. Here we show that taking advantage of the particular shape and chemistry of imogolite, it is possible to prepare inside/out Janus nanotubes. Two kinds of symmetric Janus nanotubes are prepared: one with an external hydrophilic surface and an internal hydrophobic cavity (imo-CH₃) and one with an external hydrophobic surface and a hydrophilic internal cavity (OPA-imo). The behaviour of such inside/out Janus nanotubes at oil/water interfaces is studied. The OPA-imo adsorbs strongly at the oil/water interface and is very efficient in stabilising water-in-oil emulsions through an arrested coalescence mechanism. Imo-CH₃ also adsorbs at the oil/water interface. It stabilises oil-in-water emulsions by inducing slow oil-triggered modifications of the viscosity of the continuous phase. The possible transport of small molecules inside the imo-CH₃ nanotubes is evidenced, opening up routes towards self-assembled nanofluidics.

Single-step formation of micron long (OH)3Al2O3Ge(OH) imogolite-like nanotubes

Micron-long germanium-based double-walled imogolite nanotubes were synthesized at high concentrations, as evidenced by cryo-TEM, AFM, SAXS and IR characterization methods. In addition, the spontaneous formation of a liquid-crystalline phase was observed. The novel synthesis route made it possible for the first time to obtain both long and concentrated germanium-based imogolite-like nanotubes in a single step.