Multifunctional coatings based on ultrasmall CeO2 nanoparticles for complex surface protection

The versatility and enhanced performances of today’s nanotechnologies pave the way for the design of surface coatings able to tackle several degradation pathways. Yet, designing effective strategies based on nanomaterials requires deep knowledge of their physico-chemical properties to better engineer their activity and tailor it to the final application. Cerium oxide nanoparticles (CeO2 NPs) are an exemplary case in which deep knowledge of their features allows to fully exploit and tune their catalytic functionalities. The antioxidant, UV-shielding, and antibacterial activity of these NPs can respond to the objective of this project, which focuses on the design of an advanced coating formulation for the protection of complex substrates exposed to multifactorial environments. Considering this goal, the performances of CeO2 NPs can be fully exploited by maximising the surface-to-volume ratio and precisely managing the Ce(III)/Ce(IV) redox cycling. Advancements in NPs-based coatings have been outlined in the literature, especially revolving around the achievement of polymer nanocomposites. Nonetheless, the development of high-performance and chemically stable coatings remains a challenge due to the lack of control in the NPs-polymer interactions. In this thesis, the combination of CeO2 NPs and chitosan has been explored, taking care to preserve the catalytic activity of the nanocatalyst and posing particular attention to its stability. Indeed, the protective action of CeO2 NPs combined to the barrier effect of chitosan can give rise to interesting synergistic effects, which positively impact the antibacterial and UV-shielding actions of the coating. This multifunctionality opens the way to application in complex case studies such as the conservation of frescoes. The vulnerability of these substrates remains a longstanding concern, driving the research towards innovative strategies. However, the field presents some inherent constrains that must be carefully considered when designing novel coating formulations. Current treatments have limited success due to the intricate nature of frescoes and the variability of their degradation conditions. Thus, the promotion of a rational coating design requires the definition of clear objectives, which can be identified through the analysis of these critical drawbacks. The successful application of the coating in this context can open novel routes towards other technological fields, expanding the impact of this project and finally offering a versatile strategy for surface protection.