Halloysite Nanotubes: Interfacial Properties and Applications in Cultural Heritage.

The peculiar surfaces of halloysite nanotubes and their biocompatibility are attracting the interest of researchers based on the wide range of attainable applications. The large aspect ratio of this nanotubular material ensures promising properties as reinforcing agent in polymeric matrices, such as cellulose and its derivatives, that entail strengthening due for instance to ageing-induced degradation. The halloysite cavity has a suitable size to host a large variety of active species such as deacidifying (calcium hydroxide) and flame retardant agents (fluorinated surfactants) for a controlled and sustained release relevant in conservation of Cultural Heritage. Additionally, anionic surfactants can be selectively adsorbed at the inner surface generating inorganic micelles able to solubilize hydrophobic species in a controlled cleaning protocol. We briefly discuss how the natural halloysite nanotubes can be supportive in various conservation process of Cultural Heritage and present an outlook for future perspectives.