Engineering nanoceria for the protection of ancient frescoes

Ancient frescoes undergo complex degradation phenomena that irreversibly alter the surfaces and compromise the structural integrity, putting at risk the historic and cultural legacy from the past. To avoid this loss, innovative conservative solutions are highly sought, and nanomaterials could answer this urgent need. Cerium oxide nanoparticles (CeO2 NPs) have been gaining the interest of scientists due to their catalytic activity [1], and they can be the ideal candidates to fight difficult-to-tackle degradation phenomena. A microwave-assisted synthetic protocol was developed to obtain high yield and high surface-to-volume ratio. Thanks to this optimized approach, highly uniform NPs with diameters below 3 nm were produced, as determined with advanced characterization techniques. Through UV-visible spectroscopy the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) catalyzed by CeO2 NPs has been monitored as a quick assessment of the catalytic performances. After this extensive characterization, CeO2 NPs were included into a chitosan-based formulation [2], which was applied to mock-ups especially designed to replicate Roman frescoes. Preliminary tests of color alteration, hydrophobicity, and surface morphology were implemented, before and after artificial ageing, showing promising results in the development of advanced protective coatings based on CeO2 NPs.