Recent advances in the application of metal oxide nanomaterials for the conservation of stone artefacts, ecotoxicological impact and preventive measures

Due to the ongoing threat of degradation of artefacts and monuments, the conservation of cultural heritage items has been gaining prominence on the global scale. Thus, finding suitable approaches that can preserve these materials while keeping their natural aspect of is crucial. In particular, preventive conservation is an approach that aims to control deterioration before it happens in order to decrease the need for the intervention. Several techniques have been developed in this context. Notably, the application of coatings made of metal oxide nanomaterials dispersed in polymer matrix can be effectively address stone heritage deterioration issues. In particular, metal oxide nanomaterials (TiO2, ZnO, CuO, and MgO) with self-cleaning and antimicrobial activity have been considered as possible cultural heritage conservative materials. Metal oxide nanomaterials have been used to strengthen heritage items in several studies. This review seeks to update the knowledge of different kinds of metal oxide nanomaterials, especially nanoparticles and nanocomposites, that have been employed in the preservation and consolidation of heritage items over the last 10 years. Notably, the transport of nanomaterials in diverse environments is undoubtedly not well understood. Therefore, controlling their effects on various neighbouring non-target organisms and ecological processes is crucial