Clays and other inorganic nanoparticulate solids are commonly used as building blocks to produce a new generation of nanostructured functional materials of interest for diverse applications. In particular, the presence of silanol groups at the external surface of fibrous clays, such as sepiolite, facilitates their assembly to other nanoparticles stabilizing the resulting nanoarchitectures that may show simultaneously the properties of the individual nanoparticulated solids or even synergistic effects. In this context, we introduce a new family of nanoarchitectures based on the assembly of sepiolite nanofibers and halloysite nanotubes (HNT) and show various examples on their further modification as a route towards functionalization of nanocomposites. Ultrasonication of the clays dispersed in water produces highly homogeneous and stable suspensions from which it is possible to cast films of variable sepiolite:HNT composition. Moreover, the methodology allows the further assembly with other nanoparticulated solids.For instance, the incorporation of cellulose nanofibers to the dispersion allows for the preparation of biohybrid films with improved mechanical properties. The HNT can be used as container for drugs and other species. In this way, the biohybrid films are potentially applicable as antiseptics as demonstrated by the controlled release of encapsulated salicylic acid from the lumen of HNT. The films proved very effective in the inhibition of <i>S. aureus</i> bacterial growth at pH 5.5 (typical human skin pH). Alternatively, the co-assembly of the clays with graphene nanoplatelets and/or carbon nanotubes produces electrically conductive inorganic materials that can be processed as films or as foams. The additional incorporation of biopolymers like chitosan or alginate allows for the conformation of conducting bionanocomposite films and foams with improved mechanical properties. These bionanocomposites are useful for the loading of bioactive species, which leads to versatile functional materials of interest for diverse applications. For instance, immobilizing glucose oxidase enzymes in the HNT lumen renders materials acting as the active phase in biosensors and as 3D bioanode in biofuel cells.

Sepiolite-halloysite nanoarchitectures and their role in functional nanocomposites

255th National Meeting (2018)

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