An Approach for Magnetic Halloysite Nanocomposite with Selective Loading of Superparamagnetic Magnetite Nanoparticles in the Lumen.

We present for the first time a method for the preparation of magnetic halloysite nanotubes (HNT) by loading of preformed superparamagnetic magnetite nanoparticles (SPION) of diameter size ∼6 nm with a hydrodynamic diameter of ∼10 nm into HNT. We found that the most effective route to reach this goal relies on the modification of the inner lumen of HNT by tetradecylphosphonic acid (TDP) to give HNT-TDP, followed by the loading with preformed oleic acid (OA)-stabilized SPION. Transmission electron microscopy evidenced the presence of highly crystalline magnetic nanoparticles only in the lumen, partially ordered in chainlike structures.

Quantification of amino groups on halloysite surfaces using the Fmoc-method.

The functionalization of halloysite nanotube (HNT) surfaces with aminosilanes is an important strategy for their further decoration with organic molecules to obtain hybrid inorganic-organic nanoarchitectures to be used in catalysis and drug delivery. The exact quantification of amino groups on the surface is an important aspect in view of the obtainment of systems with a known number of loaded molecules. In the present study, we describe a simple and reliable method for the correct quantification of groups present on HNT surfaces after their reaction with aminopropyltriethoxysilane (APTES).